At a local bar they had a game machine, and if you got a high score on any of the games, your tab for the evening was free.
One of the games was a "spot the differences" between two pictures with an ever decreasing timer for each round. Using this trick I was able to easily surpass the high score, and garner a crowd watching me perform this mind numbing feat.
My son and I always make jokes about everyone's 5 minutes of fame. Some random person on the jumbotron at a sporting event "Yup, there's his moment, it's over now."
Totally indulging in this side discussion: I remember thinking in high school and college that fame was the end-all of life, telling people that my goal was to have my own Wikipedia page. I saw it as something like the combination of being a "cool kid" (but for, you know, the whole of society instead of just one's school) and a sort of immortality.
Anyway, over the last couple of decades as an adult, besides realizing the obvious - how terribly shallow that is, and missing so much of what's really good in life - I've realized how fleeting fame seems to be even for the truly famous. Even looking over the list of US Presidents (never mind lesser political figures like VPs, cabinet members, congressmen, etc.) as someone who has always been interested in history, I look at some names and think, "who?" or "I've heard the name, but know nothing about him." I mean, of course you can still read about them, but that even a US President can be largely forgotten as a household name within 250 years is really a stunning thing to think about; they are ultimately no more immortal than someone who only has their name in a genealogy database or on a grave marker.
I think the desire for fame isn't an inherently bad thing.
> He was the man most gracious and fair-minded,
> Kindest to his people and keenest to win fame.
Those are the last lines of Beowulf. A man who won great fame among his people by slaying monsters and dragons. It's telling that the final line of the poem ends with his most dominant trait, "and keenest to win fame." Wanting fame is not wrong, and is far from shallow. The question is, "fame for what?" Regardless of whether you think Beowulf existed or not, it's telling that for a whole culture that the most important characteristic of a great man in one of their great poemsis "keenness to win fame," almost as a wink, with the bard saying "and if you want to be sung like this hero, you must desire fame just as keenly, and so do great deeds."
You may or may not be aware that Andy Warhol famously quipped that, "in the future, everyone will be famous for 15 minutes," back in the late 1960s. As media has gotten to be ever more ubiquitous and the cost of entry lower, he was clearly onto something decades before the internet!
Yeah, I was thinking that the while modern social media has made the "cost of entry lower," and everyone can theoretically reach more people than ever, it's hard to even describe most of it as "fame" anymore. I mean, does content even "go viral" anymore, with users subdivided into the tiniest niche communities or audiences? Even if things get traction for a while, there's so much competition with so much other content that everything seems to get quickly drowned out and then can't even be found again later through search.
I think the "cross eyed" phrase is a bit ambiguous.
What I ended up with (I think) is a focal point not closer than the screen but farther than it. My eyes didn't want to do it at first but then they did.
What is weird about it is the focusing and focal point are out of sync --- my brain can do it but the weird feeling is one of "gosh, this thing is a lot closer than it should be" where "should be" is based on focal point, and "is a lot closer" is based on focus.
Don't want to do this too much, feels like I could easily decalibrate my brain for real life lol.
Same as in autostereogram, the trick is to look to the distance.
Close your eyes and imagine a mountain far away or some distant object, notice how your eyes adjust to see it. Open your eyes and try to look at this imaginary mountain while the image is in front of you.
When you see the third Image, treat it as if its a distant 3d object somewhere on the horizon.
Bring your finger between your face and the image.
Now look at your finger.
Move your finger back and forth.
While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.
That's your moment.
Pull out your finger and look at that image.
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Should take lot less tries to learn doing it without finger. I have taught cross eye to my siblings and cousins using this method. But if you always need finger to focus it's fine.
The finger trick did it for me. As mentioned elsewhere, I used to do this academically (looking at protein structures), but I couldn't easily get back in the groove here without the finger.
When I was six, some older kid showed me this trick, but I could never really cross my eyes. These days, I wear glasses, so I guess no new superpowers for me.
You may have a very slightly 'lazy eye' (I do) - it can be a lot less extreme (not at all noticeable to others) than the pointing-completely-different-directions that people imagine, and iirc is highly correlated with astigmatism.
Optician used to tell me to work the muscle by following my finger to my nose, trying to maintain a single image. At a certain point it will snap into two - the 'lazy' eye has given up and drifted slightly - the goal is to get the finger as close as possible. Obviously if you get very close or all the way, that's 'cross-eyed', but I just can't do it.
Here's another trick: open the image in a browser, then zoom out. The smaller the image (up to a point and you can find a sweet spot) the easier it is to get them to overlap. Once you've got it, slowly zoom in a bit at a time, re-acquiring the overlap at each stage.
to HN yesterday which some people get and others don't. (That's different from the "cross-eyed stereogram" because one of them involves having two images and the other one has one image with two images hidden in it)
I can understand why it's hard for some. I've landed on that wiki page a while ago and couldn't figure it out. Then found a similar thing on an itch.io page that was easier for me to figure out.
In these later examples (starting with the easy puzzle of the OP, and your 3d examples), I find that I do the process in two stages.
Unfocus my sight until the third image shows up in the middle at the correct size (as a blurry mess). Then try to focus the center image.
which is one reason why stereo movies have struggled. (That plus some people get sick... Having both a flat and 3-d movie in two different theaters comes across as money grubbing to the consumer but it is really a money sink to the theater.)
I have a big problem crossing my eyes too while having no problem with the parallel view way seeing stereograms. I am actually going to stop trying as my eyes started to hurt.
Which one makes things become bigger? I learned that one first and then later figured out the one that makes the mixed image smaller (cross eyed I think?). Now I cannot do the big one anymore.
For me, what's difficult is holding my right eye closed without my left eye drifting to look at my nose. My right eye's good, I can move it and focus on anything within my (now peripheral-limited) view... but the left is wonky. I think I learned how to wink (and hold it) with the right really early, by age 3 or 4, but the other side I never tried until I was pre-teen... some sort of muscle atrophy?
You can also tell if your head's level, just by crossing your eyes. If the two images are diagonal to each other, then your eyes/head aren't level. I have no idea what the possible use for that would be.
What really helped me was doing some sessions with an Orthoptist to reeducate my eyes. I used to see double when stressed sometimes and could never imagine to converge/cross my eyes and retain focus.
With the reeducation I was able to see the Impossible one in focus after a couple tries.
I spent far too much time as a twenty-something generating autostereograms, which seems to have trained my eyes. I was able to "cross" the images on this page very quickly.
NB autostereograms require you to move your eyes away from each other, the opposite of crossing them. To put it another way, crossing your eyes is what your eyes do when you're looking at something close to you, while the opposite is when you're looking far away.
Which is why for ASGs people advise you to look past the picture. Or why you bring the pic close to your eyes (so close that you basically have no choice but to look beyond the picture)
Ever since I was a child addicted to the "magic eye" stereogram books, I've always diverged (not crossed) my eyes for spot-the-difference puzzles.
Also, if you're doing it on a piece of paper, hold a pen in each hand spaced right so you see the middle (3rd) hand in the middle combined image, and move both hands in sync to circle all the differences. Kind of a cool way to point them out to someone else.
The difficult puzzle took me about 10 seconds here since I was looking for more than one difference. I saw the first difference in about 1 second.
You can easily generate inverted ones that require crossing your eyes to appear properly, but they don't look as nice since they pop out instead of going into the screen/book.
When it works you get what seems like 3 images with the middle one showing the differences; you can then relax and peruse the middle image at will. I guess all the practice with SIRDS as a child probably helps.
It helps me to see the depth and then properly focus to cross them very slightly to start, then as I see the image my eyes adjust to pull it in focus properly.
That happened to me too but I persisted and eventually succeeded. I think I needed to cross my eyes slightly more than I was initially. I have been diagnosed with a minor eye convergence issue which makes it difficult to focus on near field objects in motion -- gaining this superpower was difficult but I did it without a headache thankfully.
Same! I feel like I can get a fleeting moment and then it's gone. I swear I could cross my eyes when I was a kid - I wonder if with practice it'll come back or if I'm just old and this skill I didn't-know-I-wanted is lost
My whole life I've been doing stereograms by diverging, but I couldn't get the three images in the post (the pairs would get closer but never fully overlap), so I tried crossing based on your comment. It was way easier than diverging (obviously, since I couldn't do it otherwise), but it took me a few tries, because I think it's actually /too/ easy to cross your eyes compared to diverging - I was way overshooting when I crossed my eyes. The trick was to notice this, and then control the un-crossing until they lined up.
Is diverging harder? I find it easier. Maybe it is from long ago practice on stereograms, but I'm curious if it could be due to neurological/physiological differences.
Diverging is way way easier for me, but I am positive that's because of the 10's of hours (at least) that I spent staring at magic eye images as a child.
Crossing is easier because you can simply hold your finger in front of your eyes and look at that for practice.
Diverging requires you to look past the image, meaning you have nothing to really look at, which makes it difficult to figure out what your eyes are even supposed to do.
Those stereograms aren't helping much either, since they look like nothing until you get it right. With cross-eye you have instant double-vision that you just need to align.
Cross-eye also works across much larger distances, diverging fails when the images are too far apart.
It depends on the image. If the two images are too far apart then it could require your eyes to diverge, and not to just converge slightly less. That might be impossible.
Diverging is definitely harder, and might be out of focus. To keep in focus I found it easier to focus on the right image and then cross my eyes, rather than staring in the center and then staring through the screen into the distance while trying to make them line up.
I used to not be able to do the "magic eye" 3d images until recently, and this trick is pretty handy.
For crossing just focus on your finger and then remove it.
Looking far away may be harder, and afaik it’s near impossible to look “past infinity”, iow pictures must be less wide than the distance between your eyes.
Btw these two methods aren’t equivalent in watching stereograms. If you look at one and see something but it doesn’t really make sense, then it’s probably the opposite chirality.
Personally I hate the crossing method because it makes your eyes feel strange for a while.
how I approached crossing: first practice just crossing your eyes and observing how every object has two images in this case and when you slowly “uncross”, they merge back into one. you can use anything in your surroundings.
then for the stereogram you do the same, observe the out of focus edges of the left and right pictures, then slowly uncross until left and right image occupy the same spot as though they were the same object. now its out of focus, but one (ok, actually three, because there were two, you “doubled” that by crossing, then merged two of them. but ignore the other two and focus on the merged pair)
sometimes you will merge images of the same picture, in this case you are just back at your normal vision, repeat :)
then you try to keep them overlapped and focus the vision, try to “believe” that you are really looking at a single object.
Failed to perform the technique despite multiple retries, but didn't have any issues spotting differences the normal way for all except the impossible mode - which just felt like it would be tedious.
My usual method is just to brute-force linear scan from left to right, top-to-bottom. May not be elegant, but it works.
Fun fact- when I was a teenager, my friends and I set up a stand in a local mall selling those “magic eye”posters. We made bank for a few months. But, there are actually a lot of people that medically cannot use the technique, or at least for whom it is extremely difficult or less vivid. Severe astigmatism, (obviously) blindness in one or more eyes, and certain attention deficits or fidgety types often have a difficult time.
I, on the other hand, 37 years later,am basically permanently crosseyed from the experience lol. It somehow became a resting state for me from all of the practice, so I’m always doing it on any kind of repetitive patterns, and even “successfully” on random ones which does some really weird stuff in your visual cortex.
How bad does your astigmatism have to be? I've only ever been able to get one magic eye poster to work for me in my life, and I had no idea astigmatism had any impact until just now! I don't know if mine counts as severe, but this would explain a lot for me.
As it happens, I also can't focus on the images in TFA after crossing my eyes to get the shimmer the author refers to.
This is my peak fame as well. I had the high score on every one of these I've played using this method. My friends were always try to figure out how we could make money doing it...
We got a magic eye book when I was maybe 6 - some time early elementary school. After learning how to do it, and also trying it by crossing my eyes to see an "inverted" image, I started doing it whenever I saw some repeating pattern IRL. It was most interesting when it was slightly uneven, for example a fence with sloppily applied vertical planks. Doing the magic eye would make it seem like some of them are closer to you than others. Eventually I tried the same on those "spot the difference" games since well it seemed kinda obvious to try, and I was blown away that it accidentally gave me that "superpower". I think that was pretty smart for a 6yo. Has only gone downhill ever since. ;-)
Wow I feel like I've never seen anyone talk about this. Doing it with fences can feel pretty magical, like the object is more "real" than other things.
I wrote a paper about doing this using human eyes as the "repeating pattern" (either someone else's, or your own in a mirror): https://philpapers.org/archive/ALEDSK.pdf ...You can use this trick to make boring meetings or conversations mildly more amusing (but be careful not to look like a clown crossing your eyes).
If you're an expert at this, you can even do it to your own hands. Hold both hands in front of you but with one of them palm-away and one of them palm-toward you, so that they have the same shape, then cross- or parallel-view them to get an illusionary middle third hand. Walk around while focusing on the third hand and it's a seriously trippy effect.
Another "super power" application similar to OP: the ability to confirm whether or not two distant digital clocks' seconds-digits are perfectly in sync. Since they're distant, it takes time to shift one's gaze from one to the other, making it hard to confirm whether they're in sync. But cross your eyes so as to reduce the distance, and voila.
Yet another application: quickly assume the same head-tilt angle as your conversation partner. Suppose they tilt their head to the left by N degrees and you want to tilt yours the same way, how can you be sure you have the exact correct tilt? Easy: parallel-view their eyes (as described in the aforementioned paper). You will HAVE to tilt your head the same as them in order to see their "third eye" (and once you've locked on to their third eye, you can effortlessly adjust your head tilt as they do by using their third eye as the necessary guide)
If you're distant enough / the people are sitting close enough, you can stereogram two people's faces together. You usually only get fleeting moments of crispness when their heads are aligned correctly though.
Yep! If I knew someone IRL who was into this kind of stuff, I'd really love to experiment with this sort of thing and mirrors. Arrange so that you can stereogram your conversation partner's face with a mirror image of your own face (and that he can do the same with your face and a mirror image of his face). If anyone's in NYC and interested in these sorts of things, my email is in my HN profile "about".
Stereogramming your colleagues eyes during boring meetings.
Ha
Edit: I accidentally did something similar by imaging the crease on an N95 mask as a smile near their nose. It made them look like ducks and I had to bite my tongue so hard to not laugh. I could not unsee it.
That's amazing! Within 40 seconds I overlapped the two hard mode images and saw 8 shimmering objects set within a clear picture. It took me a little longer (maybe a minute), but the two impossible mode pictures snapped together and I saw a single shimmering star within an otherwise crystal clear photograph!
I discovered this trick independently about a decade ago, to use cross-eyed viewing to easily spot differences between two similar images. Like you said, the parts that mismatch appear to shimmer and be unstable, making them obvious.
However, I feel eye strain from doing it, so I prefer other methods. 99% of the time, I do https://en.wikipedia.org/wiki/Blink_comparator instead, just switching between two images with zero flicker and zero displacement offset. Also with both eyes, it's easier to spot certain kinds of subtle differences like color shifts, JPEG-like compression artifacts, tiny differences in antialiased renderings, etc.
One benefit of the cross-eyed method, though, is that you can difference videos. But the use case for that is rarer than differencing images.
I'll second the blink comparator method as a simple diff checker, or when comparing two chunks of code that are structured exactly the same way but somehow behave differently. (e.g. "what's the difference between these two functions" or "how is this yaml block different from that yaml block"?)
Line them up as two tabs in the editor, flip very rapidly between the two repeatedly, and usually the difference is apparent in 5-6 flips.
A simple trick to doing this, in case it's not clear how to do it, is to try focusing on an imaginary point behind the screen as you look at the images. You will see a third image between the two start to come into focus. Now relax your eyes and look at that image. Simple, and quite a bit more relaxing than crossing your eyes.
The only disadvantage to this method is that it seems there is a limit to how wide the middle image can be, i.e., the original images may not completely overlap.
If you do want to cross your eyes but do not know how to do it, do the opposite of the above: try to focus on an imaginary point closer to you than the screen as you look at the images. This method is far more taxing on the eyes though.
This is called “divergence” [1] and is less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR). I believe there’s a reddit covering the more prurient variety of that!
The only problem with divergence is that you can't go too much farther out than the distance between your eyes, whereas convergence works for larger images as well.
The problem I have with this is that instead of the images completely overlapping they overlap a section in the middle. I can't get both images to completely overlap and am getting some eye strain from trying to force them.
As a kid, I got a Magic Eye book and learned to see it by crossing my eyes (ie, focusing in front of the screen). I thought it was pretty interesting when I realized that I was seeing all the images inverted ("peaks" were "valleys" and vice versa) due to the way I was focusing. Alas, I never was able to see the images "correctly".
It's funny because even if you do the Magic Eye pictures "correctly" (focusing past them) you can still get funky images by going too far and locking the surrounding pattern a second time. If I remember right the first time I did this was on a heart picture (similar to [0]), which ends up looking like a big puffy W stacked on top of a slightly larger puffy W :D
Are you sure that's supposed to be a heart? I see the three peaks of a "W" as well -- I think it's supposed to be a tulip, no? That also matches the background theme.
Yep, well at least 98% sure anyway. But you're right, that 'second level' image does look a lot like a tulip, much better description than what I said about W's :) And of course this led me to try zooming out a bit and going for level 3+... kinda feels like I'm looking down at the top of a strangely shaped wedding cake, which would also go nicely with the flowers and heart theme. Thanks for giving me an excuse to take another look!
Instead of crossing your eyes to focus in front of the image, you have to uncross them and focus on something behind the image. Put your finger about six inches in front of your face and then look at the horizon. If the horizon is in focus you should see two fingers.
Nevertheless, I was astonished that "impossible mode" literally took me only 1-2 seconds to find the missing star.
Like, I knew our vision is good at interpreting depth from images. I figured it would be all right at finding large areas of differences. I had no idea a single freaking pixel could stand out like a sore thumb.
I had trouble finding the "shiny" pixels on that one simply because the stars also had that issue - but after enlarging the image a bit more and scanning back and forth I was able to pick things out a bit better.
Now, ask me to look at my code again for a couple minutes and it might be tough but it worked :)
I have a slightly lazy right eye, so this has always come naturally to me, but I will say it's considerably easier to achieve the false focal lock on printed material— something about screens, even quality ones with high refresh rates, just isn't the same.
I'm great at magic eyes / stereograms and have a ton of posters around my house with them, but I still had trouble with seeing the differences in the test images. I easily locked in my focus on the overlapping cat images but only one difference stood out to me. I eventually got them all but it wasn't that easy (maybe with practice I could get there). The differences are noticeable when I focus right on it, but when I'm looking at the whole image it's harder to tell what is missing from one eye.
Are you able to look around while keeping your "unified vision"?
To me, all the differences appeared to be flashing (probably my brain alternates between the pair of images it attempts to "lock in", or something to that effect).
I find there's a two step process, first overlapping the images (but which makes the images blurry), then letting my eyes refocus so the middle image is crisp. Only then does 3D or shimmer effect happen. Takes some practice to merge the images while maintaining focus for me.
Are you able to confirm the images are completely aligned? You can do this using landmarks, like the brightest stars on the telescope pic. I.e. if you see more than one of any landmark, it is not aligned. You may need to adjust zoom, and distance from face.
I’ve done Magic Eyes a lot, but I’m failing on this. (However, I found the difference in the coffee beans picture reasonably fast without the eye-crossing trick, and before reading what the difference is.)
It blows my mind that every human doesn't know this. I figured it out as a child. The easiest way to prevent this is to have one of the two images be slightly tilted. I can rotate my eyes but it's much harder than crossing them.
When auto stereograms were all the rage in the late 80's I had a program on my Mac Plus that let me make/edit them and I used to edit for hours WHILE looking at them in 3D. Then one time I was walking down a hallway with a repetitive wallpaper pattern, my eyes did the thing, the entire hallway appeared to shift in front of me, and I stumbled and fell. Still to this day my eyes will sometimes automatically snap into 'alternate' focus when viewing a repetitive pattern.
Then copy that and paste it a bunch of times to make it multi-line.
Cross your eyes so that the WORD's overlap (all except the leftmost and rightmost). You now see two cursors instead of one. Position your two cursors anywhere you want and then insert a space in order to make the corresponding WORD (or ORDW or RDWO or ORDW) sink into the screen. (Or rise if you parallel-view.)
We used to do this in the computer labs back in 6th grade.
This happens to me easily inside cars with these dotted-breathing roof interior patterns. (Edit: g “perforated vinyl fabric”)
Well, worse than easily - sometimes I cannot get back to normal and am not sure how far it actually is, because the nature of the pattern allows to re-lock at every few cm. I just don’t know where I’m really looking at unless there’s an irregular object nearby.
This happens to me too. Particularly when it's on a narrow horizontal repetition (like wooden slats on a wall).
I attribute mine to playing a lot of the game Magic Carpet from the mid to late 90's. It had some interesting graphics modes, including Red/Blue anaglyph 3D and a stereogram 3D mode. It was fun to try to play it, but it used noise for the pattern, so you didn't get textures, only blobby shapes.
I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.
I wonder what skills other people picked up that I didn't.
Some recent example of things I shared:
+ When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.
+ Putting a jacket or any open-front garment on quickly. I saw someone struggling to maneuver their second arm in a tight jacket behind their back. I explained that if they hold their jacket out in front of them, put their hands in the arm holds, and slide their arm in further as they swing it around their body they'll get it on in a moment. It's also more stylish. They were so surprised.
> I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.
Conversely, I'm amazed by the amount of things I discover as an adult are not common experiences or skills for people, despite being considered as such. This includes, for example, having an inner voice (which I do), or ability to visualize things in your head (which I don't).
Wrt. the latter, when I learned as an adult that some people actually can conjure up images in their mind on demand[0], and conversely that aphantasia is a thing, it took me few more years to connect that back to some early experiences in childhood - being bored out of my mind by some well-known novels that my parents and teachers found particularly engaging. Specifically, the ones rich in descriptions of scenery. They'd say that's the best part, what makes the story rich and immersive, and that's what imagination is for and those books are good for exercising it. Meanwhile, I'd feel ashamed and wonder what the fuck are they talking about, while skimming to find where the descriptions end so I can resume reading from there. Well, it turns out what they said was true for them, but is not true for people like me, who can't visualize to save their life.
Well, except in dreams. Which makes the whole thing even more fascinating.
> Some recent example of things I shared:
Interesting. I somehow managed to never learn either, so thanks! Ironically, I realize now I've probably seen people do the jacket swing trick hundreds of times, and yet it never registered in my mind as a distinct technique, much less one that I could learn.
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[0] - Fun fact: that makes "undressing someone with your eyes" a literal ability for them too.
> When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.
Yep. And there is a special vertical prong keeper tab on some trousers for exactly this purpose.
Some of us are born with small frenula of the tongue (or we undergo tongue-tie surgery as kids) and can thus perform Khecari mudra without the traditional self-mutilation used by yoga-masters. https://en.wikipedia.org/wiki/Khecar%C4%AB_mudr%C4%81 This can be useful for cleaning tonsil stones or post-nasal drip, but of course you must do so discretely since people would consider that absolutely disgusting
If you want to read out loud for long stretches of time and you hate taking breaks to catch your breath: you can read out loud while inhaling too! (It feels and sounds super weird though so this isn't very useful in practice.)
And here's a party trick related to OP's super power. Pick a distant object and cross your eyes so as to see it double, preferably with the two doubles distant from each other (i.e., cross your eyes significantly). Then, alternately switch between staring at the left double, and the right double. If you do it right, it will look like your eyes are moving in a bizarre alien way.
This whole "just cross your eyes" thing has never worked for me, not once. I've seen these strange patterns printed on the backs of notebooks that supposedly make some sort of 3D effect when you "just cross your eyes". Later, when I saw similar images online, I was able to at least visualize these hidden shapes by opening the image in photoshop, duplicating the layer, setting the copy to "difference" and moving it left or right. The regular texture would eventually disappear and the shape would emerge. It's still a mystery to me what it feels like to view these the intended way though.
1. When you cross your eyes, gradually let them return to uncrossed. Try to do it as slow as possible. Along the way, try to line up any structures that you see in the image that are repeated from left/right half.
2. Once you are able to hold a cross-eyed gaze long enough with lined up left/right half, slowly move your eyes between different features near the middle. Your eyes will naturally want to start to focus and match up pieces.
3. Don't be too far or too close to the image; they are usually easily viewed from comfortable distances. If the image is too big, make it smaller. It's usually easier smaller.
4. Initially, when you cross your eyes, or look through the image, it will likely be blurry. This is because your brain naturally associates accomodation and convergence with also changing focus. You'll learn to decouple those things and you will more quickly be able to go from focusing on the 2D image to crossing it without changing focus much.
I've also always had a hard time with these. I suspect it's because one of my eyes was slightly lazy when I was a child, so my brain learned to put more importance on the signal from the other eye. When I cross my eyes, the image from the better eye tends to just totally override the other one, so it can be really hard to see these kinds of effects.
I have exactly this as well. My optician explained it as my brain would use the information from the lazier eye only if there wasn't any information from the good eye. Just tried the eyes crossed trick on the easy image in the article and the 3rd image in the middle is the right one. If I let them drift apart so there are 4 images I can see the left one and the difference (because I'd already found it), but as soon as I force them to overlap the left signal disappears and I'm only seeing the right image. I've also never managed to do a magic eye or anything, and 3d movies just give me a headache.
Same here, but I always imagined that for it to work, I would need to have roughly equal vision in both eyes, which I don't. Everything is blurry with my left eye, and no glasses or lenses have ever helped. I attribute this as the reason.
Note that there is a difference between crossview and parallel view. See this image [0] and try to overlap them. Depending on what you see in the foreground, that is the type of view you're able to see.
Basically, it determines whether the 3D view you're seeing from the stereoscopic pair is convex (pops out of the page) or concave (goes into the page). It is of course possible to learn both views but most people naturally see one or the other. You can go to r/crossview or r/parallelview depending on which one you see.
I find that there are different techniques to seeing both.
If I stare at the image and cross my eyes until focus lock I get crossview where the image goes back into the page.
If I bring the image right up to my eyes and stare through it into the distance, then slowly move the image backwards into my gaze until I get focus lock, then I get parallel view where the image pops out of the page.
I have always wondered the difference between the two and why it happens. Thanks for shedding some light on it :)
EDIT: I have just managed to achieve both without moving my head or the image for the first time in my life! Just by trying to look further 'past' the picture into the distance, and then by slightly crossing my eyes and focussing at a point in front of the picture.
I have been trying to do this for 30 years, and it is only your explanation which helped me to do it. Thanks so much!
I had never done the parallel view before either- spent 5 or so minutes at it and finally got it. For me it's still takes a fair amount of effort to maintain it (unlike cross view that takes effort to stop seeing it instead) but the 3d looks way more impressive somehow. Like the Toronto crowd one- hadn't seen so much depth in a "magic eye" before
I believe it’s better because it is more natural to eyes. You may also want to play with the perspective. E.g. the hall here looks much better from 0.4m than up close on my phone due to the picture’s perspective. https://triaxes.com/docs/3DTheory-en/522ParallelCrosseyedvie...
Note that for parallel viewing the left edges (or centers) of the images should not be farther apart than your own eye spacing aka interpupillary distance (IPD) sometimes just called PD.
That imgur may need to be shrunk depending on your screen for parallel to work.
my vision is so bad with nearsightedness that when I take corrective lenses off, I can focus on an ipad mini screen within 10" of my face and perceptually it is the same as focusing on a distant movie theater screen. No straining, eyes totally relaxed.
With the lights off, it's better than being in a theater. I tried an ipad pro in the Apple store and it felt like I had my own personal unfairly huge IMAX screen.
Unlike when focusing on a movie screen, your eyes have to turn inward to direct the pupils to converge at the physically near iPad. This can cause muscular eye strain (it does for me).
You can get clever and order a prismatic prescription that bends light out, so your eyes don't have to turn inward. I tried it too, but it gave me nausea.
I have really bad vision too (my prescription is left: -8.00, right: -7.50). Tried this out, and yeah, really works! And realized, you need the best resolution screen possible, because you can see every detail.
Not sure how much I'll use this is the future, but good to know it's always an option!
For anyone who wants to learn this, try this way using your finger as a helper.
Put the images in front of your eyes.
Bring your finger between your face and the image at almost middle of the distance.
Now look at your finger.
Move your finger back and forth and notice the background (where your picture is)
While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.
That's your moment.
Pull out your finger and look at that image.
--
It worked on everyone I have tried to teach. You may always need help of your finger or a tip of a pencil or whatever. But it's lot easier to get those images to merge this way.
My eyes seem to immediately refocus as soon as my finger moves away no matter how many times I try this. Before I move my finger away, everything in my peripheral vision is too blurry to be useful.
As I understand it, Magic Eye stereoscopic images were originally developed by brain scientists studying how we see in 3D (i.e., how the brain processes 2 eye inputs into a 3D image).
There were two competing theories:
1. The brain first does a recognition pass (that's a house, that's a person, etc.) and compares the two eyes to see which objects have moved.
2. The brain compares the two eye inputs first, at the "pixel" level and figures out which pattern of pixels has moved, then afterwards, applies recognition to the resulting 3D image.
Magic Eye would only work if #2 is the correct theory (because in Magic Eye, there is nothing to recognize until AFTER you convert to 3D).
Visual diff. The operation of finding differences between two files by eyeball search. The term optical diff has also been reported, and is sometimes more specifically used for the act of superimposing two nearly identical printouts on one another and holding them up to a light to spot differences. Though this method is poor for detecting omissions in the ‘rear’ file, it can also be used with printouts of graphics, a claim few if any diff programs can make. See diff.
An interesting variant of the vdiff technique usable by anyone who has sufficient control over the parallax of their eyeballs (e.g. those who can easily view random-dot stereograms), is to hold up two paper printouts and go cross-eyed to superimpose them. This invokes deep, fast, built-in image comparison wetware (the same machinery responsible for depth perception) and differences stand out almost immediately. This technique is good for finding edits in graphical images, or for comparing an image with a compressed version to spot artifacts.
I think the key is not "going cross-eyed" as much as it is relaxing your focus until the images merge. If you intentionally cross your eyes, it hurts. If you de-focus/relax your eyes until the images merge, it doesn't hurt.
i had the same thing where best i could get when i relaxed was a narrow merge, and when i crossed my focus was too close to my face to be helpful, plus strain.
sudden clicked after fully crossing 5 or 6 times and then relaxing and was able to hold the "3rd image" very easily. felt like magic, even hardest difficulty was obvious
For me it just does not work right now. Maybe I have bad eyesight, I wear glasses and am past 40. I believe I was able to do this trick in past though. At the very least on psychedelics (various kinds). This also made me able to relax my eyes more, wheras I normally have too much pressure on them according to optician.
That's more for traditional "magic eye" pattern stereograms where you want to relax your eyes to look off into the middle distance behind the subject instead of intensely focusing on something unnaturally close to your face.
I didn't spend the time reading the comments to see if this has been said already, but crossing your eyes works but learning to diverge your eyes is better in some situations. It's easier to learn to cross because you can just look at your nose, and you can bring together two images that are further away by crossing than by diverging. But diverging is the way we are normally (when looking across the room say instead of at a book in front of us) so it's more comfortable.
Wait, that's not crossing your eyes, it's uncrossing them. Ordinarily if you look at something nearby, your eyes aim at a common spot. But when viewing a stereogram, you need to convince your eyes to aim at a spot more distant than the subject.
This is easy with practice, however IMHO it helps to be significantly nearsighted. Then you simply take off your glasses, and can look at something nearby with infinity focus, which is naturally associated with uncrossed eyes.
I don't know whether it's possible to train yourself to diverge your gaze, i.e. stereoscopically see images that are separated more than your pupil distance. Certainly I can't do that.
For spot-the-difference, crossing your eyes is more effective and easier to "dial in" than uncrossing them. You're essentially making each eye look at the opposite image. If you try uncrossing, then you need to make sure the images are at the exact correct distance to cause them to overlap with that technique, because you can only uncross your eyes enough to look straight ahead.
Is that true? It seems that our eyes are mechanically capable of looking in divergent directions, what's the reason that we're not able to "uncross" them beyond looking straight ahead?
(Edit: Anecdotally I can confirm for myself that I'm not able to do it, so wondering if there's anyone that can.)
From a control system standpoint, if you have one control that rotates both eyes the same number of degrees left or right to determine gaze direction and another to rotate both eyes the same (positive) number of degrees inward to control fixation distance, you can't specify the left eye rotated left of center and the right eye right, even if each eye physically can rotate that way. Not sure if that's how eyes actually work though.
Looking uncrossed at the images in the article on my phone, I can easily achieve the effect uninterrupted between fully stretched arms and about half that.
That's because you have to find the distance between your eyes and the stereogram to make it work. Crossing your eyes is easier because your eyes can turn inwards far more than they can turn outwards, so it works at more distances.
While intuitive, I’m not so sure. I look at the center line and slowly cross my eyes until the 3rd image slides into place and then I get focus lock. At no time do I feel my eyes uncross and go the other way. Hmm!
Both work equally well if you just want to spot differences. Cross-eyed view is somewhat easier to do, since people naturally cross their eyes when looking at something close to their face, but there is no natural reason for one’s eyes to diverge. But cross-eyed view also gives a subjectively smaller image, and is also not the usual way autostereograms are made to be seen.
> but there is no natural reason for one’s eyes to diverge.
When you’ve finished looking at something close to your face and your eyes need to uncross. So you do that eye movement while still holding the image close to your face. Note you are looking “past” where the image is. As long as the image is closer than your infinity focal view you can do this, it doesn’t have to be close to your face necessarily, Magic Eye posters on walls do work.
Wow. Thanks to MarkusWandel I discovered I can focus images while crossing my eyes and finally understood your comment. I've always done the "uncrossing" since I was a kid.
1. Get a bit closer to the screen so you can see both images clearly.
2. Now, cross your eyes and aim to overlap both images.
3. Draw the rest of the fucking owl.
Seriously. Ever since my physics teacher in high school tried to get the class interested in stereograms, everyone and every article I see talking about it treat "crossing your eyes" as an atomic, trivial step. It isn't. I for one have no first clue how to do it, it's not a distinct operation I know how to perform. Perhaps this is because I am nearsighted and wear glasses.
Still, I wish articles like these focused on explaining how to do the whole cross-eye thing, because once you master that, everything else becomes instantly self-apparent and doesn't need further explanation (I know because I did manage to accidentally cross my eyes once or twice while looking at a stereogram, so I know how the effect looks like).
EDIT: FWIW, I compensate by using another trick for diffing documents with Mark I Eyeball - get them printed on separate pieces of paper, put one on top of the other, and hold in front of you with some bright light behind you (Sun, or your phone's flashlight, will do). Not as good as crossing your eyes, but something I can reliably do.
I have strabismus and have always been good at these games. I wonder if it helps me for similar reasons? The examples on his page were pretty easy for me, though the universe one took maybe 45 seconds.
human stereo vision processing has incredibly sophisticated noise filtering capabilities that are still hard to replicate in software. The shimmering effect people report is essentially your visual cortex highlighting areas where the stereo correspondence fails.
You can use this same technique to view glasses-less 3D (stereoscopic) images. It's also fairly easy to create your own. Take two photos but offset the camera lens by approximately eye-width. Open the image editor of your choice and place the images side-by-side. View the composite image cross-eyed and you are now viewing a 3D scene.
Also worth noting there are 2 versions of this kind of cross-eyed focus depending on whether your eyes are focusing on a point in front of or behind the actual image. This determines which side the left and right eye images should go on in the composite. I find it easier to focus on a point in front of the images but IME most examples online are for focusing on a point behind the image.
Well this is interesting. I was able to find the impossible one within 2 seconds without crossing my eyes. The easy one took about 5 seconds, 3 seconds for hard. I've always been hyper-vigilant with patterns (to a fault), so not sure if that's playing into this.
Is that what other folks are experiencing also? I see most comments are trying it with their eyes crossed, but what about without?
EDIT: ok I just watched the video. No eyes crossed. For the balloons one I beat out the girl in the video by 2-3 seconds. For the birds about the same. The skittles one tripped me up, couldn't find it. The other few I found around the same time, the lights at the end I didn't find in time either. It seems I'm quicker when there's not too many colors involved. Still that's spooky.
I've got -7.5 myopia/nearsightedness in both eyes, with astigmatism. As a result, my eyes can easily go out of focus to do Magic Eye or this type of thing. The bonus superpower is, if I take my contacts out and get really close up on something, it's like I'm looking through a microscope; if I happen to have glasses on, sometimes I can also catch the light and focus in just the right way to further magnify what I'm seeing already zoomed in. In those instances I see whatever's reflecting through the glasses, so mostly eyelashes and skin/pores, but it's fascinating nonetheless. Can't see a damn thing beyond the tip of my nose without corrective lenses though LOL
Weird timing. I dunno why this works but I've been using it to see mice.
You see, I noticed that I have a mouse problem in my garage. I figure if I've seen one mouse, there are probably more. So, I stood on some stairs in my garage and crossed my eyes to sort of blur the scene. It allowed me to catch movement more quickly and I was quickly watching multiple mice run around the edges of the area.
Hmm. I noticed in lectures, if I stilled my eyes, most of the field of view would grey out, except for areas of motion (eg a lecturer's head or writing arm) which appeared normal. After motion stopped in an area, it would slowly grey out. When a motion started, its area would snap to normal, making it easy to spot onsets of motion. Eventually my eyes would twitch, and the whole field would refresh.
I first read about this back in the 1980s, in an issue of Science Digest. Couldn't find a link or reference on short notice, but here's something from the American Academy of Ophthalmology that explains the phenomenon, with an experiment to see the blood vessels in your eye:
Apparently, the brain tends to ignore visual stimuli that don't change over a short period of time, which allows you see "around" the blood vessels passing through the middle of your eye. By closing your eye, and moving a penlight around against your eyelid, you can make the vessels cast a shifting shadow on your retina that makes them visible.
The reason you usually see everything out in front of you is that various actions cause your eye to shift about just a little, just enough to cause the image on your retina to shift about enough for the brain to notice.
I've done this in the past with bugs in the grass. If I stare at a fixed point, I start seeing each individual bug moving through the grass, whereas normally they would be really hard to spot among all the fine details of the ground and grass blades.
That seems like not the same thing though, right? You're not doing a diff on two images, you're just losing resolution so you can direct more attention to movement.
A ton of comments in here saying this is easy/old hat for them.
Well I'll be the one to say this blew my mind. somehow creating the third middle image, being able to relax my eyes and even scan around this composite image actually made me giggle out loud on my laptop, a very rare occurrence. Thank you to the author.
Using this trick, I wrote a program for 3d plot visualization in the 80-s. It computed two projections of the plot, as if looked by left and right eye, and printed them side to side on the thermal printer. If you looked hard enough, you can bring the two pictures together and see a 3d picture!
I’m frequently baffled by how unaware most people seem to be about the absolute basics of how their eyes work. Like, people don’t even seem to be aware of how their stereo perception is largely made from two images, or any of the implications that has. I actively think about the two images maybe dozens of times per day.
Chill out, that's a bit of hyperbole isn't it? This is just a trick for doing a spot the difference puzzle. It's not exactly a daily task most people are thinking about.
Most people at least understand that stereographic vision has something to do with 3D perception because we've all closed 1 eye before.
I've used this to quickly read through a few hundred page documents given to us only as a scanned pdf which was too low quality to run ocr (at the time) on. The sleazy counter party was very upset when I came back with notes on them not adding the changes we asked for on the drafts they sent back within minutes of them sending them back.
There's a video game of this called QuickSpot. Back in 2008, this was one of my favorite games for the Nintendo DS. It trains the ability to spot little differences quickly. Sadly, outside of winning a barely known video game, it's not a super useful skill.
I can get the overlap to lock in, but the simmering effect is weak and difficult to pick out. Probably still faster than exhaustive search, but I don't feel like I'm at superpower level. Maybe my brain favors one eye more than the other? I know I have different glasses prescriptions for each eye.
2. This strip of cardboard has a number line on it. Put one end half way down your nose, perpendicular to your face. You will see two lines. Merge them at their furthest point, then merge the next nearest point, repeat. (I think this is called the 'Brock String Exercise', but can't find an image similar to the one I recall.)
Almost certainly a lot of the people saying they are ”crossing” their eyes are actually ”uncrossing” their eyes; focusing the eyes straighter than what would normally happen on the surface where the image is laid out.
This is also how the legendary ”Magic Eye” books were supposed to be viewed. Not by crossing the eyes.
Feel like people who are old enough to remember that 6 week period in the 90's where those Magic Eye 3d Stereogram pictures were everywhere have a big advantage here.
I've heard about this before, but I've never actually managed to do it until just now. I needed to sort of "tune the parameters" a lot so that my eyes were crossed but also focused, since I've had a lot of trouble actually getting them in focus when I'm doing it, and the effect isn't as pronounced as I expected it to be
Learned it from Magic Eye books too! But using it for spot-the-difference is way more practical - saves so much time compared to staring at two pictures. Kind of feels like having X-ray vision for finding differences
An alternative technique called “divergence” [1] (pulling your eyes apart) is significantly less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR)! I believe there’s a reddit covering the more prurient variety of that.
This is what I do, the only issue is that I don't have nearly as much "range" with divergence as I do with convergence, so I have to make the pictures as small as possible when using it to line up two images (as opposed to autostereograms, which usually have a much smaller divergence offset).
It's a little more abstract since you don't have handy moving-reference-object like your finger, but: Place the picture in front of something deep, like a long hallway. Look off at something in the distance behind the picture, like the end of the hallway. Notice how the edge of the picture is a double image. Focus on gradually resolving the edge of the picture down from double-image to single-image, and then do the reverse by looking down the hallway again and seeing the picture go back into double-vision. Just keep practicing that until you get the feel for controlling your depth perception and then try holding the same depth of the hallway while you turn your gaze to the picture and try the same action with your eyes.
The funny thing about the stars image is this is a common way to find asteroids, comets. It's not limited to just those. Only instead of a bunch of cross eyed astronomers, they overlay and align the images and do subtraction/difference filtering to see what's left. For comets/asteroids, the dot of interest will move between frames. Even just playing back the aligned images as a timelapse can reveal motion.
Nice to see someone discover this! I've always been partial to spot the differences and crossview images - I am able to cross each eye independently of one another, which makes overlapping these sorts of images very easy. For example, I could cross my right eye, while my left stays perfectly still. This causes instant double vision, and relaxing how crossed the eye is lets me line the images up very quickly. It's fun to do in places with a repetitive wall texture, too - seeing something in real life while adding a faux 3D effect on top of it is kind of trippy. Probably my most useless skill, but a fun one regardless.
This trick is interesting to me as someone who mixes records. I (and mixers in general) have a lot of different tricks for making mono audio objects in the mix feel stereo or have a sense of width or depth.
Examples include:
1. Delaying the left or right channel by a few ms (Haas effect).
2. De-tuning one of the channels by a few cents
3. Boosting an EQ band on one channel, with a complimentary cut on the opposite channel.
...and many more.
These are usually very subtle changes that our stereoscopic ears have no problem detecting.
In any case, when we need to do some forensic searching for possible differences between two near-identical channels we'll invert the polarity on one channel and then sum them. The resulting delta sticks out like a sore thumb and highlights even then tiniest differences between the files.
So it's fascinating to discover that we can easily do something similar with our eyes to find the differences.
You can also use this to display 3-D images. You have a stereographic projection of your image (like those kids' view-masters) and then just cross the eyes and look at the middle image. Only since the 2 images are slightly different, you can have the middle image be 3-D. It takes a bit of practice though and causes eye strain (at least for me)
It's not a great way of showing the image, but it'll do in a pinch.
I'm amazed that there's so many comments and yet not a single one is pointing out that the coffee bean is missing from the _right_ side of the image. Not the left.
This did not work for me. I was able to invoke a middle image, but there was no shimmering. After I found the difference the old-fashioned way, I realized that the middle image showed the distinguishing feature as it is on my non-dominant side.
To really blow peoples' minds use both hands to tap the differences, keeping the left hand for the left image and the right hand for the right image!
From your POV the images are merged so your hands will look like they're tapping a single image, but from the audience's point of view you look like a savant with multi-attention!
I spent weeks doing this, looking at stereoscopic (?) images of protein structures, while a grad student in molecular biophysics. I got so that I could see the overlapped images pretty much instantly. But I'm having a hard time getting it now, even on the easy one.
I've always thought that ability to unfocus the eyes might be related to mental focus. If you have difficulty staying on topic, or a diagnosis of ADD/ADHD or whatever {I'm not equate these} AND find it really hard to do magic eye images... Then please take part in my 'totally scientific study'TM.
I found it almost instantly, which was by dumb luck.
But in the following few moments, seeing two nearly identical photos side by side soon made me think of stereograms, since I'm into them, and have shot a few in my lifetime.
I then used my eyes to overlap the images.
In binocular overlapped view, the difference loudly draws attention to itself, because it flickers between the two eyes.
It's almost as if there were a blinking LED saying "here it is!"
Instead of crossing your eyes and attempting to focus, what can really help relax your ocular muscles is to do the opposite: look "past" the images into the distance until the images overlap.
Is the technique to this exactly the same as the technique to view a 3d stereogram image?
I was able to get a 3rd image to be clearly visible in the middle doing this, on the 2nd image I could definitely seem some spots appear that lead me straight to 3 of them but didn't work for me on the other 2 images.
The left-right full-image stereograms... but those are less common than the pattern-based "magic eye" stereograms. Those are the reverse of this - in the linked image and the left-right full-image stereograms, they're done by crossing your eyes to a point closer to your eyes than the original image.
The pattern-based "magic eye" stereograms are done by looking through the image to focus on a point deeper into the screen further from your eyes.
The latter I think are less painful because they use the more natural depth-perception distances of your eyes instead of using what feels like more unnatural positions, but that might be my bias because I'm a bit farsighted. Maybe they're just more common because they're visually inscrutable at first and so you get the "reveal" of the 3D contour from a single large image instead of two already-visible small ones.
I use this technique to get web layouts pixel-perfect with the mockup, just put both windows next to one another and superimpose them with your eyes. Works great. There are tools that do this by overlaying an image with 50% alpha but it doesn't work as well.
Last year when there was a bunch of fuss about Kate Middleton not having made any public appearances there was a minor flap where people claimed that a photo she'd released was just an edit of an earlier photo.
There was a tweet presenting two photos, one old and one purporting to be new, where she was holding strikingly similar poses. The claim was that the new one was just an edit of the older one. I used this technique and immediately the minor differences stuck out like a sore thumb- her hand was rotated more in one, her hair was laid differently, etc.
Any recommendations for when you can't get the images to quite overlap?
I feel like I can get 75% of the way there, but then they start going the other direction. I can do magic eye easily.
This does not work even in the slightest. When I cross my eyes, the image becomes wayyyy too blurry and its hard to keep it in the center for more than a second
I've been doing this since I was a kid as well. When I was younger some restaurants would have video monitors with games on them, and one of them was spot the difference. I essentially maxed out the score and still held the highest score when I came back in town years later. I wonder if its still around...
There are some great examples and detailed explanations IMO of this general phenomenon in the book "How the Mind Works" by Stephen Pinker. It essentially discusses how your brain is doing statistical work to build the 3D model from these 2 stereoscopic images.
i certainly used this trick back in my college days, prompted by a similar technique for "seeing" 3d stereoscopes on a computer monitor. I feel like i learned it somewhere on Eric Weisstein's Mathworld because the 3d objects viwer app let you split the image into two stereo images. Unfortunately java applets have been banished from the internet landscape.
Wow that's interesting — trying to cross my eyes produces hellish jitter.
I suspect it's because my left eye is slighty lazy.
But I was able to superimpose the right cat picture onto the left one (it's a lot harder for the more complex sky resort picture). It's pretty eerie, the right picture just slides right up the left one (I did need to figure out the right distance for it).
It doesn't help me pick out the differences though, I mostly only see the right picture, and if try to focus my left eye, the right picture slides out. Still, intersting.
I remember doing this as a child on our TV that had a picture-in-picture setting. I would set the same channel twice and cross my eyes pretending that it was 3d TV.
How does that work when the two images are different sizes and overlapping? Did your PiP mode have a split screen option? The ones I've seen only allowed moving where the insert was placed (which corner), but it was always a PiP and never a split screen.
I couldn't do the cross-eyed thing, but it took me maybe 20 seconds to spot the difference just by looking at sections of the images. But I'm not sure that would have worked had the missing bean been buried in the denser part of the photo.
If it's perfect, the overlapping regions just merge in color, i.e. the cat's paw becomes off-white. If it's not perfect, I still have to attend to which parts are popping in and out. In both cases I still have to compare the merged view to the left and right hand sides.
Although it is very nice for illustrating each eye's contributions to the merged view. Just not an attention-saver.
I tried crossing my eyes, but it’s not working for me; I keep seeing things blurry. Maybe I’m doing it wrong. However, I solved the first two puzzles. For the last one, I just guessed randomly. My guess wasn’t exactly correct, but it was close, just a little distance away.
One thing I noticed: because you're tricking your eyes into thinking they're observing at a different distance, your brain doesn't seem to correctly account for head tilt (my theory of the diagnosis). Anyway, I think you're head must be exactly level with the image or you'll get double-vision/blur
Claims have been made (outside the medical mainstream) that regularly practicing crossing your eyes helps stave off presbyopia. One does get better at seeing stereograms with practice, so it seems like it at least improves some type of muscle control.
25y ago, i was working behind a 30" tube monitor (a ~35kg hog), with 1 inch thick frontglass.. and one day, one of my eyes started to focus on the (closer)outside of the glass, the other on the (farther)inside of the glass. Could not shake that with closing/blinking. Worse, later, when i got into the car, the closer eye focused on the windshield - instead on the landscape ahead.
Took 1 week of everyday 1-2 hours staring far away at the ocean, to revive. AND removal of the monitor :/
My Piano teacher used to have this book on her coffee table with images like this. You could blur and cross your eyes, and the image would combine to become 3D.
But I never knew this technique could be used to spot the difference between images. Very cool discovery!
I always feel like I'll permanently see cross eyed if I keep doing that. It doesn't help that I was accidentally hit in the head by my double's partner racket in tennis and spent like a minute or two walking around seeing double. Not fun.
Some repeating tile patterns like stripes will cause my eyes to do this automatically and it's really weird and annoying because everything else gets blurry. Fun trick though.
I was hoping to get a new superpower today, but when I was young I was cross eyed. I got this corrected through surgery and can no longer cross my eyes.
I picked this up during the magic eye craze of the 90s, and I will never not find it hilarious how people get shocked at my ability to find the differences. I always share the skill too, it’s one of those things people find impossible until they get it and it’s easy.
After a short period of training, I got to the point where I can see the third image which I can focus on. However, the differences are very subtile and don't stick out at all :/
Validates a claim in the predictive processing paradigm. The diff between actual and expected is what matters to error correction. That's where all the relevant information is.
Doesn't work for me. Just like stereograms. I just don't know how to "tell" my eyes to cross. Maybe similar to how I didn't figure out until I was 20-something how finger snipping works. Maybe by the time I'm 50 I can cross my eyes...!
You dont 'tell' your eyes to cross, you just look closer or further away. Try looking at the image at normal distance, whilst imaginging that you are looking into the distance at a beautiful view or at the horizon on an ocean. It is this difference in distance focusing which causes the illusion.
Actually, given enough practice, you can literally just get your eyes to do it. I started doing magic eye puzzles as a kid and loved it, so just eventually learned how to control my eyes in that way. Even today, if I see any repeating pattern, or even anything vaguely similarly shaped, I can’t help but do it
Well actually, I've been telling my eyes to cross since I was a child. I can't describe it, it's like tensing a muscle in the eyes or something and you can control the angle with the tension.
I can even rotate my eyes! Did you know we have muscles for that? I trained it in the mirror - try tilting your head and look at your eyes REALLY closely: they rotate a bit to cancel out the tilt.
Whenever I try to do this, the most I get is that the two images touch. The cats in the example are holding paws, but they never overlap. I've been trying to make this work since the old magic images from the 90s, but I've never managed it. I wonder if there isn a hardware limitation related to my eye configuration.
The never work for me because my eyes don't work well together. Just not team players. I'm almost always looking through just one or the other, annoyingly usually the one that would least be preferable.
To do it with crossed-eye view, try looking at your finger and slowly moving the finger closer to your eyes until you see a third image come into view in between the two on the screen. At some point your brain will/might let you focus on that image.
i have ~1 diopter shortsightness. Was less before, slowly going up. So screens are getting blurrier. Have glasses but still try avoid using them.
If i put the (flat edged) TV remote control at about 10cm from my face so it horizontally shadows lower half of both eyes, i see perfectly (without any glasses).
I cannot do this by crossing my eyes (focusing on a point between you and the image), I have a hard time getting the cross to stay consistent and it never really "locks in" for me. Instead of crossing my eyes, I unfocus them, effectively look through the image. Once I get the repeating part to overlap cleanly, after a second or two, my pupils adjust their focus and the image fades from blurry to clear in a really satisfying way and kind of "locks in" in a way that takes little to no effort to maintain. With a bit of practice, I can even move my eyes around and look at different parts of the two overlayed images without distrupting the effect at all.
I don't know if it's just my brain working differently or if a there is some confusion in the discussion between crossing your eyes and focusing through an item.
That's so cool, thanks for sharing this. I managed to do all of them, in the impossible one I identified correctly the area, but couldn't pinpoint the difference.
I think thats the best part of this skill. Everyone did 'Magic Eye' images as a kid, but to be able to take that useless skill and apply it to something more useful and interesting is really cool.
"
Someone called out Kevin Smith for this on one of his podcasts. According to Smith, on the day of filming, he asked if the picture really was a sailboat, and the prop master said no. When Smith started questioning this, the prop master said that a) it flashes on the screen too quickly for anyone in the theatre to notice, and b) VHS was too low-resolution for people to freeze-frame it to try it at home. So Smith let it slide.
Smith summed up, "Now, thanks to Blu-Ray, I get people pointing this out to me all the time!"
"
I appreciate the sentiment but "overlay the images by crossing your eyes" receiving that kind of incredulous reaction is really funny and kind of sad for me. I hope it's just amateur editorializing.
You can also just back away from the screen. For the 3rd one I had to back up about 6 feet from my monitor before it clicked into place, once it is in focus you can move closer to see the difference better.
This trick had been used in practice to detect fake banknotes and coins, with a device like a two-sided periscope. It allowed a bank worker to put a real coin on one side and the tested sample on the other, so that any differences can be immediately apparent.
This is also how I used to do Magic Eye images when I was a kid. Although the stereoscopic image was inverted on the z axis, it was a lot easier than to cross eyes by looking further out into the distance
This is how I help my family when they're stuck on "spot the difference" steam games. It also takes literally any fun out of them, the actual game has to come from not (just) spotting differences, because that task is trivial.
Yes, I didn’t think people would be so amazed by it either. Like it’s mind-blowing that this works or has been thought of. But we first did it once as well, some people just discover it late in life I guess (or not at all).
I found the toolbars and stuff around the edge of the image made it difficult for me to lock onto the crossview image in your example; surrounding it with more blank background makes it easier for me: https://imgur.com/a/NizzRgo
Having similar acuity in both eyes made a huge difference for me. I'm somewhat astigmatic but was able to do this eye "uncrossing" trick just fine. I had a significant loss of acuity in one eye and that's what left me unable to do this (or to watch 3D movies).
At a local bar they had a game machine, and if you got a high score on any of the games, your tab for the evening was free.
One of the games was a "spot the differences" between two pictures with an ever decreasing timer for each round. Using this trick I was able to easily surpass the high score, and garner a crowd watching me perform this mind numbing feat.
Probably my peak fame right there.
>Probably my peak fame right there.
My son and I always make jokes about everyone's 5 minutes of fame. Some random person on the jumbotron at a sporting event "Yup, there's his moment, it's over now."
At least yours got you something ;)
One of my dad's sayings when somebody in a film delivered a line and then disappeared was "6 months rehearsal for that."
I envision happy families watching the end credits for Dad's name as Third Assistant Caterer on a big budget film.
Totally indulging in this side discussion: I remember thinking in high school and college that fame was the end-all of life, telling people that my goal was to have my own Wikipedia page. I saw it as something like the combination of being a "cool kid" (but for, you know, the whole of society instead of just one's school) and a sort of immortality.
Anyway, over the last couple of decades as an adult, besides realizing the obvious - how terribly shallow that is, and missing so much of what's really good in life - I've realized how fleeting fame seems to be even for the truly famous. Even looking over the list of US Presidents (never mind lesser political figures like VPs, cabinet members, congressmen, etc.) as someone who has always been interested in history, I look at some names and think, "who?" or "I've heard the name, but know nothing about him." I mean, of course you can still read about them, but that even a US President can be largely forgotten as a household name within 250 years is really a stunning thing to think about; they are ultimately no more immortal than someone who only has their name in a genealogy database or on a grave marker.
I think the desire for fame isn't an inherently bad thing.
> He was the man most gracious and fair-minded, > Kindest to his people and keenest to win fame.
Those are the last lines of Beowulf. A man who won great fame among his people by slaying monsters and dragons. It's telling that the final line of the poem ends with his most dominant trait, "and keenest to win fame." Wanting fame is not wrong, and is far from shallow. The question is, "fame for what?" Regardless of whether you think Beowulf existed or not, it's telling that for a whole culture that the most important characteristic of a great man in one of their great poemsis "keenness to win fame," almost as a wink, with the bard saying "and if you want to be sung like this hero, you must desire fame just as keenly, and so do great deeds."
You may or may not be aware that Andy Warhol famously quipped that, "in the future, everyone will be famous for 15 minutes," back in the late 1960s. As media has gotten to be ever more ubiquitous and the cost of entry lower, he was clearly onto something decades before the internet!
And then there’s Banksy’s “in the future, everyone will be anonymous for 15 minutes“. For pretty much the same reasons you stated above, I assume.
To update this excellent quote to 2025, change minutes to seconds and you just described TikTok.
Yeah, I was thinking that the while modern social media has made the "cost of entry lower," and everyone can theoretically reach more people than ever, it's hard to even describe most of it as "fame" anymore. I mean, does content even "go viral" anymore, with users subdivided into the tiniest niche communities or audiences? Even if things get traction for a while, there's so much competition with so much other content that everything seems to get quickly drowned out and then can't even be found again later through search.
I can't overlap the images to save my life - they get like halfway there and that's it...
That was me at first.
I think the "cross eyed" phrase is a bit ambiguous.
What I ended up with (I think) is a focal point not closer than the screen but farther than it. My eyes didn't want to do it at first but then they did.
What is weird about it is the focusing and focal point are out of sync --- my brain can do it but the weird feeling is one of "gosh, this thing is a lot closer than it should be" where "should be" is based on focal point, and "is a lot closer" is based on focus.
Don't want to do this too much, feels like I could easily decalibrate my brain for real life lol.
Same as in autostereogram, the trick is to look to the distance. Close your eyes and imagine a mountain far away or some distant object, notice how your eyes adjust to see it. Open your eyes and try to look at this imaginary mountain while the image is in front of you. When you see the third Image, treat it as if its a distant 3d object somewhere on the horizon.
There is a way to help yourself.
Put the pair of images in front of your eyes.
Bring your finger between your face and the image.
Now look at your finger.
Move your finger back and forth.
While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.
That's your moment.
Pull out your finger and look at that image.
---
Should take lot less tries to learn doing it without finger. I have taught cross eye to my siblings and cousins using this method. But if you always need finger to focus it's fine.
The finger trick did it for me. As mentioned elsewhere, I used to do this academically (looking at protein structures), but I couldn't easily get back in the groove here without the finger.
When I was six, some older kid showed me this trick, but I could never really cross my eyes. These days, I wear glasses, so I guess no new superpowers for me.
I tried, this, and I can get it to overlap in the background, but as soon as I take my finger away, I lose it.
You may have a very slightly 'lazy eye' (I do) - it can be a lot less extreme (not at all noticeable to others) than the pointing-completely-different-directions that people imagine, and iirc is highly correlated with astigmatism.
Optician used to tell me to work the muscle by following my finger to my nose, trying to maintain a single image. At a certain point it will snap into two - the 'lazy' eye has given up and drifted slightly - the goal is to get the finger as close as possible. Obviously if you get very close or all the way, that's 'cross-eyed', but I just can't do it.
Here's another trick: open the image in a browser, then zoom out. The smaller the image (up to a point and you can find a sweet spot) the easier it is to get them to overlap. Once you've got it, slowly zoom in a bit at a time, re-acquiring the overlap at each stage.
It's like
https://triaxes.com/docs/3DTheory-en/522ParallelCrosseyedvie...
which some people struggle with, somebody posted a
https://en.wikipedia.org/wiki/Autostereogram
to HN yesterday which some people get and others don't. (That's different from the "cross-eyed stereogram" because one of them involves having two images and the other one has one image with two images hidden in it)
I can understand why it's hard for some. I've landed on that wiki page a while ago and couldn't figure it out. Then found a similar thing on an itch.io page that was easier for me to figure out.
In these later examples (starting with the easy puzzle of the OP, and your 3d examples), I find that I do the process in two stages.
Unfocus my sight until the third image shows up in the middle at the correct size (as a blurry mess). Then try to focus the center image.
What's more a lot of people (maybe 20%) don't benefit from things like
https://www.reald.com/
which is one reason why stereo movies have struggled. (That plus some people get sick... Having both a flat and 3-d movie in two different theaters comes across as money grubbing to the consumer but it is really a money sink to the theater.)
Yeah that's me. I lack stereoscopic vision so such tricks or 3d glasses etc do not work.
I have a big problem crossing my eyes too while having no problem with the parallel view way seeing stereograms. I am actually going to stop trying as my eyes started to hurt.
Which one makes things become bigger? I learned that one first and then later figured out the one that makes the mixed image smaller (cross eyed I think?). Now I cannot do the big one anymore.
For me, what's difficult is holding my right eye closed without my left eye drifting to look at my nose. My right eye's good, I can move it and focus on anything within my (now peripheral-limited) view... but the left is wonky. I think I learned how to wink (and hold it) with the right really early, by age 3 or 4, but the other side I never tried until I was pre-teen... some sort of muscle atrophy?
You can also tell if your head's level, just by crossing your eyes. If the two images are diagonal to each other, then your eyes/head aren't level. I have no idea what the possible use for that would be.
What really helped me was doing some sessions with an Orthoptist to reeducate my eyes. I used to see double when stressed sometimes and could never imagine to converge/cross my eyes and retain focus. With the reeducation I was able to see the Impossible one in focus after a couple tries.
I spent far too much time as a twenty-something generating autostereograms, which seems to have trained my eyes. I was able to "cross" the images on this page very quickly.
NB autostereograms require you to move your eyes away from each other, the opposite of crossing them. To put it another way, crossing your eyes is what your eyes do when you're looking at something close to you, while the opposite is when you're looking far away.
Which is why for ASGs people advise you to look past the picture. Or why you bring the pic close to your eyes (so close that you basically have no choice but to look beyond the picture)
Ever since I was a child addicted to the "magic eye" stereogram books, I've always diverged (not crossed) my eyes for spot-the-difference puzzles.
Also, if you're doing it on a piece of paper, hold a pen in each hand spaced right so you see the middle (3rd) hand in the middle combined image, and move both hands in sync to circle all the differences. Kind of a cool way to point them out to someone else.
The difficult puzzle took me about 10 seconds here since I was looking for more than one difference. I saw the first difference in about 1 second.
You can easily generate inverted ones that require crossing your eyes to appear properly, but they don't look as nice since they pop out instead of going into the screen/book.
Is that the crossy-eye porn?
When it works you get what seems like 3 images with the middle one showing the differences; you can then relax and peruse the middle image at will. I guess all the practice with SIRDS as a child probably helps.
Don’t CROSS them. Relax them, like you’re tired and can’t focus on a computer screen.
Also keep the size low. If you’re having a hard time at 20cm from a 4k 30” monitor, it won’t come easy. Zoom out.
You can actually do it both ways, but which is easiest for whom is different.
There are two methods, either you cross them either you do like you’re describing.
It helps me to see the depth and then properly focus to cross them very slightly to start, then as I see the image my eyes adjust to pull it in focus properly.
That happened to me too but I persisted and eventually succeeded. I think I needed to cross my eyes slightly more than I was initially. I have been diagnosed with a minor eye convergence issue which makes it difficult to focus on near field objects in motion -- gaining this superpower was difficult but I did it without a headache thankfully.
Same! I feel like I can get a fleeting moment and then it's gone. I swear I could cross my eyes when I was a kid - I wonder if with practice it'll come back or if I'm just old and this skill I didn't-know-I-wanted is lost
Treat it like a "Magic Eye" photo and just relax your eyes to a further focus point.
If you mean literally you can only bring them half way together, try just moving twice as far away.
Are you crossing your eyes (focusing nearer than the object) or diverging them (focusing past it)? Diverging is a harder skill to learn.
My whole life I've been doing stereograms by diverging, but I couldn't get the three images in the post (the pairs would get closer but never fully overlap), so I tried crossing based on your comment. It was way easier than diverging (obviously, since I couldn't do it otherwise), but it took me a few tries, because I think it's actually /too/ easy to cross your eyes compared to diverging - I was way overshooting when I crossed my eyes. The trick was to notice this, and then control the un-crossing until they lined up.
Is diverging harder? I find it easier. Maybe it is from long ago practice on stereograms, but I'm curious if it could be due to neurological/physiological differences.
Diverging is way way easier for me, but I am positive that's because of the 10's of hours (at least) that I spent staring at magic eye images as a child.
Crossing is easier because you can simply hold your finger in front of your eyes and look at that for practice.
Diverging requires you to look past the image, meaning you have nothing to really look at, which makes it difficult to figure out what your eyes are even supposed to do.
Those stereograms aren't helping much either, since they look like nothing until you get it right. With cross-eye you have instant double-vision that you just need to align.
Cross-eye also works across much larger distances, diverging fails when the images are too far apart.
It depends on the image. If the two images are too far apart then it could require your eyes to diverge, and not to just converge slightly less. That might be impossible.
Diverging is definitely harder, and might be out of focus. To keep in focus I found it easier to focus on the right image and then cross my eyes, rather than staring in the center and then staring through the screen into the distance while trying to make them line up.
I used to not be able to do the "magic eye" 3d images until recently, and this trick is pretty handy.
Not even sure which one I should try :) but yes tried both to no avail. Maybe it's just not something to achieve in the first try...
For crossing just focus on your finger and then remove it.
Looking far away may be harder, and afaik it’s near impossible to look “past infinity”, iow pictures must be less wide than the distance between your eyes.
Btw these two methods aren’t equivalent in watching stereograms. If you look at one and see something but it doesn’t really make sense, then it’s probably the opposite chirality.
Personally I hate the crossing method because it makes your eyes feel strange for a while.
how I approached crossing: first practice just crossing your eyes and observing how every object has two images in this case and when you slowly “uncross”, they merge back into one. you can use anything in your surroundings.
then for the stereogram you do the same, observe the out of focus edges of the left and right pictures, then slowly uncross until left and right image occupy the same spot as though they were the same object. now its out of focus, but one (ok, actually three, because there were two, you “doubled” that by crossing, then merged two of them. but ignore the other two and focus on the merged pair)
sometimes you will merge images of the same picture, in this case you are just back at your normal vision, repeat :)
then you try to keep them overlapped and focus the vision, try to “believe” that you are really looking at a single object.
You might be too close to the screen.
Try on mobile, it's easier if the images are smaller.
Wow, yeah it happened immediately for me on mobile while I couldn't get past half way on my monitor. Thanks!
Yeah, me either. My eyes really resist it. And after trying it a few times it messes up my focus for a bit.
Failed to perform the technique despite multiple retries, but didn't have any issues spotting differences the normal way for all except the impossible mode - which just felt like it would be tedious.
My usual method is just to brute-force linear scan from left to right, top-to-bottom. May not be elegant, but it works.
Fun fact- when I was a teenager, my friends and I set up a stand in a local mall selling those “magic eye”posters. We made bank for a few months. But, there are actually a lot of people that medically cannot use the technique, or at least for whom it is extremely difficult or less vivid. Severe astigmatism, (obviously) blindness in one or more eyes, and certain attention deficits or fidgety types often have a difficult time.
I, on the other hand, 37 years later,am basically permanently crosseyed from the experience lol. It somehow became a resting state for me from all of the practice, so I’m always doing it on any kind of repetitive patterns, and even “successfully” on random ones which does some really weird stuff in your visual cortex.
How bad does your astigmatism have to be? I've only ever been able to get one magic eye poster to work for me in my life, and I had no idea astigmatism had any impact until just now! I don't know if mine counts as severe, but this would explain a lot for me.
As it happens, I also can't focus on the images in TFA after crossing my eyes to get the shimmer the author refers to.
Took me about 10m total to get it all the way to impossible mode. I think you can do it!
...except as you say, it didn't work. The "eye-cross" trick gave the answer on the impossible one in ~10 seconds.
The impossible one was quite tricky, but I did find I was able to relax into the image and take my time. Probably took about 10 seconds.
The impossible one was sub-2-seconds for me. I had to do it over to make sure it wasn't more than one difference...
Makes you wonder if the kid he was talking about had a lazy eye or crossed eyes or something.
This is my peak fame as well. I had the high score on every one of these I've played using this method. My friends were always try to figure out how we could make money doing it...
The game is usually called 'Photo Hunt'
Those Megatouch systems run Linux! Lots of fun messages to read on the credits screen or when you reboot them.
I haven't seen one in several years, but they always used to run Red Hat, based on the boot screens.
I was about to post this same exact post :)
Was the high score holder on there for a few years.
Just got a funny visual of someone going crosseyed and focused on overcoming a challenge in front of them, with a crowd of people cheering them on.
We got a magic eye book when I was maybe 6 - some time early elementary school. After learning how to do it, and also trying it by crossing my eyes to see an "inverted" image, I started doing it whenever I saw some repeating pattern IRL. It was most interesting when it was slightly uneven, for example a fence with sloppily applied vertical planks. Doing the magic eye would make it seem like some of them are closer to you than others. Eventually I tried the same on those "spot the difference" games since well it seemed kinda obvious to try, and I was blown away that it accidentally gave me that "superpower". I think that was pretty smart for a 6yo. Has only gone downhill ever since. ;-)
Now try it with various colors, some people can see "impossible" colors [0].
[0] https://preview.redd.it/yaiyf2bi9aa31.png?width=640&auto=web...
Wow I feel like I've never seen anyone talk about this. Doing it with fences can feel pretty magical, like the object is more "real" than other things.
Or the side of a shopping cart.
I wrote a paper about doing this using human eyes as the "repeating pattern" (either someone else's, or your own in a mirror): https://philpapers.org/archive/ALEDSK.pdf ...You can use this trick to make boring meetings or conversations mildly more amusing (but be careful not to look like a clown crossing your eyes).
If you're an expert at this, you can even do it to your own hands. Hold both hands in front of you but with one of them palm-away and one of them palm-toward you, so that they have the same shape, then cross- or parallel-view them to get an illusionary middle third hand. Walk around while focusing on the third hand and it's a seriously trippy effect.
Another "super power" application similar to OP: the ability to confirm whether or not two distant digital clocks' seconds-digits are perfectly in sync. Since they're distant, it takes time to shift one's gaze from one to the other, making it hard to confirm whether they're in sync. But cross your eyes so as to reduce the distance, and voila.
Yet another application: quickly assume the same head-tilt angle as your conversation partner. Suppose they tilt their head to the left by N degrees and you want to tilt yours the same way, how can you be sure you have the exact correct tilt? Easy: parallel-view their eyes (as described in the aforementioned paper). You will HAVE to tilt your head the same as them in order to see their "third eye" (and once you've locked on to their third eye, you can effortlessly adjust your head tilt as they do by using their third eye as the necessary guide)
If you're distant enough / the people are sitting close enough, you can stereogram two people's faces together. You usually only get fleeting moments of crispness when their heads are aligned correctly though.
Yep! If I knew someone IRL who was into this kind of stuff, I'd really love to experiment with this sort of thing and mirrors. Arrange so that you can stereogram your conversation partner's face with a mirror image of your own face (and that he can do the same with your face and a mirror image of his face). If anyone's in NYC and interested in these sorts of things, my email is in my HN profile "about".
Peak HN.
Stereogramming your colleagues eyes during boring meetings.
Ha
Edit: I accidentally did something similar by imaging the crease on an N95 mask as a smile near their nose. It made them look like ducks and I had to bite my tongue so hard to not laugh. I could not unsee it.
That's amazing! Within 40 seconds I overlapped the two hard mode images and saw 8 shimmering objects set within a clear picture. It took me a little longer (maybe a minute), but the two impossible mode pictures snapped together and I saw a single shimmering star within an otherwise crystal clear photograph!
I discovered this trick independently about a decade ago, to use cross-eyed viewing to easily spot differences between two similar images. Like you said, the parts that mismatch appear to shimmer and be unstable, making them obvious.
However, I feel eye strain from doing it, so I prefer other methods. 99% of the time, I do https://en.wikipedia.org/wiki/Blink_comparator instead, just switching between two images with zero flicker and zero displacement offset. Also with both eyes, it's easier to spot certain kinds of subtle differences like color shifts, JPEG-like compression artifacts, tiny differences in antialiased renderings, etc.
One benefit of the cross-eyed method, though, is that you can difference videos. But the use case for that is rarer than differencing images.
I'll second the blink comparator method as a simple diff checker, or when comparing two chunks of code that are structured exactly the same way but somehow behave differently. (e.g. "what's the difference between these two functions" or "how is this yaml block different from that yaml block"?)
Line them up as two tabs in the editor, flip very rapidly between the two repeatedly, and usually the difference is apparent in 5-6 flips.
To reduce eye strain, don’t cross your eyes, but relax them (so, the other way). Instantly clear and snaps together as if magnetic.
A simple trick to doing this, in case it's not clear how to do it, is to try focusing on an imaginary point behind the screen as you look at the images. You will see a third image between the two start to come into focus. Now relax your eyes and look at that image. Simple, and quite a bit more relaxing than crossing your eyes.
The only disadvantage to this method is that it seems there is a limit to how wide the middle image can be, i.e., the original images may not completely overlap.
If you do want to cross your eyes but do not know how to do it, do the opposite of the above: try to focus on an imaginary point closer to you than the screen as you look at the images. This method is far more taxing on the eyes though.
This is called “divergence” [1] and is less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR). I believe there’s a reddit covering the more prurient variety of that!
[1] https://en.wikipedia.org/wiki/Vergence#Divergence
[2] https://en.wikipedia.org/wiki/Vergence#Convergence
The only problem with divergence is that you can't go too much farther out than the distance between your eyes, whereas convergence works for larger images as well.
The problem I have with this is that instead of the images completely overlapping they overlap a section in the middle. I can't get both images to completely overlap and am getting some eye strain from trying to force them.
If you've done Magic Eyes, this is straightforward. Was able to get all 3 of the test images quickly.
This is with focusing beyond the screen. Focusing in front of the screen is something I am unable to do, and not for want of effort.
Also, your eyes might accidentally do this if looking at tiled patterns, e.g. wallpaper.
Relative image size (e.g. view distance) is important.
As a kid, I got a Magic Eye book and learned to see it by crossing my eyes (ie, focusing in front of the screen). I thought it was pretty interesting when I realized that I was seeing all the images inverted ("peaks" were "valleys" and vice versa) due to the way I was focusing. Alas, I never was able to see the images "correctly".
It's funny because even if you do the Magic Eye pictures "correctly" (focusing past them) you can still get funky images by going too far and locking the surrounding pattern a second time. If I remember right the first time I did this was on a heart picture (similar to [0]), which ends up looking like a big puffy W stacked on top of a slightly larger puffy W :D
[0] https://i0.wp.com/www.magiceye.com/wp-content/uploads/2018/1...
I think I just locked the pattern also a third time where it looks like pillars but I’m not sure if I saw it correctly.
When I first looked at this picture I saw the W pattern and then blinked and suddenly saw the intended pattern.
When you lock on the non-intended ones it feels somehow like a secret/forbidden path you shouldn’t go, like consuming drugs.
Are you sure that's supposed to be a heart? I see the three peaks of a "W" as well -- I think it's supposed to be a tulip, no? That also matches the background theme.
Yep, well at least 98% sure anyway. But you're right, that 'second level' image does look a lot like a tulip, much better description than what I said about W's :) And of course this led me to try zooming out a bit and going for level 3+... kinda feels like I'm looking down at the top of a strangely shaped wedding cake, which would also go nicely with the flowers and heart theme. Thanks for giving me an excuse to take another look!
If you see 3 peaks you went too far - which is really easy to do on mobile. I had to be careful to go only "once deep".
The background is flowers, but the hidden image is most certainly the classic heart shape.
Thanks that's one of the beautifully crafted magic eye images, bring me back memories about 20 years ago when it was a craze.
Instead of crossing your eyes to focus in front of the image, you have to uncross them and focus on something behind the image. Put your finger about six inches in front of your face and then look at the horizon. If the horizon is in focus you should see two fingers.
Focusing behind is much easier because you can get yourself started by focusing on an actual object.
Focusing in front can be done by focusing on an actual object too? Many people e.g. put a finger between them and the picture and then remove it.
The finger method interferes more with the third image in my experience.
Same -- much harder to get them to go the other way. I'm surprised that cross-eyed random dot stereograms never took off; so much easier to do.
Yup, I loved Magic Eyes as a kid. This was easy.
Nevertheless, I was astonished that "impossible mode" literally took me only 1-2 seconds to find the missing star.
Like, I knew our vision is good at interpreting depth from images. I figured it would be all right at finding large areas of differences. I had no idea a single freaking pixel could stand out like a sore thumb.
I had trouble finding the "shiny" pixels on that one simply because the stars also had that issue - but after enlarging the image a bit more and scanning back and forth I was able to pick things out a bit better.
Now, ask me to look at my code again for a couple minutes and it might be tough but it worked :)
Maybe we are the opposite. As a kid, I could only do cross-eyed-focus-in-front-of-screen, but not "focus beyond the screen". Or a book at the time.
So I was able to see the 3D in Magic Eyes, but the 3D effect was inverted.
Today as an adult I am able to focus beyond the screen, but it's still much easier for me to do it cross-eyed.
I also got all the images in the post almost right away. But my eyeballs focused in front instead > _ <
I have a slightly lazy right eye, so this has always come naturally to me, but I will say it's considerably easier to achieve the false focal lock on printed material— something about screens, even quality ones with high refresh rates, just isn't the same.
I'm great at magic eyes / stereograms and have a ton of posters around my house with them, but I still had trouble with seeing the differences in the test images. I easily locked in my focus on the overlapping cat images but only one difference stood out to me. I eventually got them all but it wasn't that easy (maybe with practice I could get there). The differences are noticeable when I focus right on it, but when I'm looking at the whole image it's harder to tell what is missing from one eye.
Are you able to look around while keeping your "unified vision"?
To me, all the differences appeared to be flashing (probably my brain alternates between the pair of images it attempts to "lock in", or something to that effect).
I can get the images to merge but the differences don't stand out.
I find there's a two step process, first overlapping the images (but which makes the images blurry), then letting my eyes refocus so the middle image is crisp. Only then does 3D or shimmer effect happen. Takes some practice to merge the images while maintaining focus for me.
Are you able to confirm the images are completely aligned? You can do this using landmarks, like the brightest stars on the telescope pic. I.e. if you see more than one of any landmark, it is not aligned. You may need to adjust zoom, and distance from face.
I’ve done Magic Eyes a lot, but I’m failing on this. (However, I found the difference in the coffee beans picture reasonably fast without the eye-crossing trick, and before reading what the difference is.)
It blows my mind that every human doesn't know this. I figured it out as a child. The easiest way to prevent this is to have one of the two images be slightly tilted. I can rotate my eyes but it's much harder than crossing them.
When auto stereograms were all the rage in the late 80's I had a program on my Mac Plus that let me make/edit them and I used to edit for hours WHILE looking at them in 3D. Then one time I was walking down a hallway with a repetitive wallpaper pattern, my eyes did the thing, the entire hallway appeared to shift in front of me, and I stumbled and fell. Still to this day my eyes will sometimes automatically snap into 'alternate' focus when viewing a repetitive pattern.
No need for the Mac Plus program, you can make these in any text editor. Use a fixed-width font and fill a line with a repeating word eg
WORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORD
Then copy that and paste it a bunch of times to make it multi-line.
Cross your eyes so that the WORD's overlap (all except the leftmost and rightmost). You now see two cursors instead of one. Position your two cursors anywhere you want and then insert a space in order to make the corresponding WORD (or ORDW or RDWO or ORDW) sink into the screen. (Or rise if you parallel-view.)
We used to do this in the computer labs back in 6th grade.
This happens to me easily inside cars with these dotted-breathing roof interior patterns. (Edit: g “perforated vinyl fabric”)
Well, worse than easily - sometimes I cannot get back to normal and am not sure how far it actually is, because the nature of the pattern allows to re-lock at every few cm. I just don’t know where I’m really looking at unless there’s an irregular object nearby.
This happens to me too. Particularly when it's on a narrow horizontal repetition (like wooden slats on a wall).
I attribute mine to playing a lot of the game Magic Carpet from the mid to late 90's. It had some interesting graphics modes, including Red/Blue anaglyph 3D and a stereogram 3D mode. It was fun to try to play it, but it used noise for the pattern, so you didn't get textures, only blobby shapes.
I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.
I wonder what skills other people picked up that I didn't.
Some recent example of things I shared:
+ When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.
+ Putting a jacket or any open-front garment on quickly. I saw someone struggling to maneuver their second arm in a tight jacket behind their back. I explained that if they hold their jacket out in front of them, put their hands in the arm holds, and slide their arm in further as they swing it around their body they'll get it on in a moment. It's also more stylish. They were so surprised.
> I'm frequently surprised by the amount of seemingly ordinary skills I picked up as a bored child that other people didn't. This was an obvious way to solve those "spot the difference" pictures in magazines.
Conversely, I'm amazed by the amount of things I discover as an adult are not common experiences or skills for people, despite being considered as such. This includes, for example, having an inner voice (which I do), or ability to visualize things in your head (which I don't).
Wrt. the latter, when I learned as an adult that some people actually can conjure up images in their mind on demand[0], and conversely that aphantasia is a thing, it took me few more years to connect that back to some early experiences in childhood - being bored out of my mind by some well-known novels that my parents and teachers found particularly engaging. Specifically, the ones rich in descriptions of scenery. They'd say that's the best part, what makes the story rich and immersive, and that's what imagination is for and those books are good for exercising it. Meanwhile, I'd feel ashamed and wonder what the fuck are they talking about, while skimming to find where the descriptions end so I can resume reading from there. Well, it turns out what they said was true for them, but is not true for people like me, who can't visualize to save their life.
Well, except in dreams. Which makes the whole thing even more fascinating.
> Some recent example of things I shared:
Interesting. I somehow managed to never learn either, so thanks! Ironically, I realize now I've probably seen people do the jacket swing trick hundreds of times, and yet it never registered in my mind as a distinct technique, much less one that I could learn.
--
[0] - Fun fact: that makes "undressing someone with your eyes" a literal ability for them too.
> When your belt buckle hangs a little loosely on the front of your pants. You can hook the buckle's prong onto the front button of your pants and it'll stay put. So many people are excited to learn this.
Yep. And there is a special vertical prong keeper tab on some trousers for exactly this purpose.
Ear rumbling: https://www.reddit.com/r/earrumblersassemble/
Eye shaking: https://old.reddit.com/r/Eyeshakers/
Some of us are born with small frenula of the tongue (or we undergo tongue-tie surgery as kids) and can thus perform Khecari mudra without the traditional self-mutilation used by yoga-masters. https://en.wikipedia.org/wiki/Khecar%C4%AB_mudr%C4%81 This can be useful for cleaning tonsil stones or post-nasal drip, but of course you must do so discretely since people would consider that absolutely disgusting
If you want to read out loud for long stretches of time and you hate taking breaks to catch your breath: you can read out loud while inhaling too! (It feels and sounds super weird though so this isn't very useful in practice.)
And here's a party trick related to OP's super power. Pick a distant object and cross your eyes so as to see it double, preferably with the two doubles distant from each other (i.e., cross your eyes significantly). Then, alternately switch between staring at the left double, and the right double. If you do it right, it will look like your eyes are moving in a bizarre alien way.
This whole "just cross your eyes" thing has never worked for me, not once. I've seen these strange patterns printed on the backs of notebooks that supposedly make some sort of 3D effect when you "just cross your eyes". Later, when I saw similar images online, I was able to at least visualize these hidden shapes by opening the image in photoshop, duplicating the layer, setting the copy to "difference" and moving it left or right. The regular texture would eventually disappear and the shape would emerge. It's still a mystery to me what it feels like to view these the intended way though.
Here are some tips;
1. When you cross your eyes, gradually let them return to uncrossed. Try to do it as slow as possible. Along the way, try to line up any structures that you see in the image that are repeated from left/right half.
2. Once you are able to hold a cross-eyed gaze long enough with lined up left/right half, slowly move your eyes between different features near the middle. Your eyes will naturally want to start to focus and match up pieces.
3. Don't be too far or too close to the image; they are usually easily viewed from comfortable distances. If the image is too big, make it smaller. It's usually easier smaller.
4. Initially, when you cross your eyes, or look through the image, it will likely be blurry. This is because your brain naturally associates accomodation and convergence with also changing focus. You'll learn to decouple those things and you will more quickly be able to go from focusing on the 2D image to crossing it without changing focus much.
There's a whole bunch on this site: https://www.magiceye.com/stwkdisp.htm
I've also always had a hard time with these. I suspect it's because one of my eyes was slightly lazy when I was a child, so my brain learned to put more importance on the signal from the other eye. When I cross my eyes, the image from the better eye tends to just totally override the other one, so it can be really hard to see these kinds of effects.
I have exactly this as well. My optician explained it as my brain would use the information from the lazier eye only if there wasn't any information from the good eye. Just tried the eyes crossed trick on the easy image in the article and the 3rd image in the middle is the right one. If I let them drift apart so there are 4 images I can see the left one and the difference (because I'd already found it), but as soon as I force them to overlap the left signal disappears and I'm only seeing the right image. I've also never managed to do a magic eye or anything, and 3d movies just give me a headache.
Same here, but I always imagined that for it to work, I would need to have roughly equal vision in both eyes, which I don't. Everything is blurry with my left eye, and no glasses or lenses have ever helped. I attribute this as the reason.
Doesn't work for me either. I just made myself queasy while trying to cross my eyes for ten minutes haha
The most mind-bending example of the magic eye effect I've found is people using it in videos.
Of course, the internet being what it is, someone made a version of Bad Apple with it: https://www.youtube.com/watch?v=RLuGJGyCS90
Note that there is a difference between crossview and parallel view. See this image [0] and try to overlap them. Depending on what you see in the foreground, that is the type of view you're able to see.
Basically, it determines whether the 3D view you're seeing from the stereoscopic pair is convex (pops out of the page) or concave (goes into the page). It is of course possible to learn both views but most people naturally see one or the other. You can go to r/crossview or r/parallelview depending on which one you see.
[0] https://i.redd.it/g5ilwgk99r781.jpg
I find that there are different techniques to seeing both.
If I stare at the image and cross my eyes until focus lock I get crossview where the image goes back into the page.
If I bring the image right up to my eyes and stare through it into the distance, then slowly move the image backwards into my gaze until I get focus lock, then I get parallel view where the image pops out of the page.
I have always wondered the difference between the two and why it happens. Thanks for shedding some light on it :)
EDIT: I have just managed to achieve both without moving my head or the image for the first time in my life! Just by trying to look further 'past' the picture into the distance, and then by slightly crossing my eyes and focussing at a point in front of the picture.
I have been trying to do this for 30 years, and it is only your explanation which helped me to do it. Thanks so much!
I had never done the parallel view before either- spent 5 or so minutes at it and finally got it. For me it's still takes a fair amount of effort to maintain it (unlike cross view that takes effort to stop seeing it instead) but the 3d looks way more impressive somehow. Like the Toronto crowd one- hadn't seen so much depth in a "magic eye" before
I believe it’s better because it is more natural to eyes. You may also want to play with the perspective. E.g. the hall here looks much better from 0.4m than up close on my phone due to the picture’s perspective. https://triaxes.com/docs/3DTheory-en/522ParallelCrosseyedvie...
Note that for parallel viewing the left edges (or centers) of the images should not be farther apart than your own eye spacing aka interpupillary distance (IPD) sometimes just called PD.
That imgur may need to be shrunk depending on your screen for parallel to work.
I can do both pretty comfortably, but there’s a definite bias to parallel, way easier for me.
I have a true vision-based super power.
my vision is so bad with nearsightedness that when I take corrective lenses off, I can focus on an ipad mini screen within 10" of my face and perceptually it is the same as focusing on a distant movie theater screen. No straining, eyes totally relaxed.
With the lights off, it's better than being in a theater. I tried an ipad pro in the Apple store and it felt like I had my own personal unfairly huge IMAX screen.
Unlike when focusing on a movie screen, your eyes have to turn inward to direct the pupils to converge at the physically near iPad. This can cause muscular eye strain (it does for me).
You can get clever and order a prismatic prescription that bends light out, so your eyes don't have to turn inward. I tried it too, but it gave me nausea.
I have really bad vision too (my prescription is left: -8.00, right: -7.50). Tried this out, and yeah, really works! And realized, you need the best resolution screen possible, because you can see every detail. Not sure how much I'll use this is the future, but good to know it's always an option!
Natures own VR goggles.
For anyone who wants to learn this, try this way using your finger as a helper.
Put the images in front of your eyes.
Bring your finger between your face and the image at almost middle of the distance.
Now look at your finger.
Move your finger back and forth and notice the background (where your picture is)
While doing this, notice that at a particular distance, the images in background will perfectly overlap each other.
That's your moment.
Pull out your finger and look at that image.
--
It worked on everyone I have tried to teach. You may always need help of your finger or a tip of a pencil or whatever. But it's lot easier to get those images to merge this way.
My eyes seem to immediately refocus as soon as my finger moves away no matter how many times I try this. Before I move my finger away, everything in my peripheral vision is too blurry to be useful.
As I understand it, Magic Eye stereoscopic images were originally developed by brain scientists studying how we see in 3D (i.e., how the brain processes 2 eye inputs into a 3D image).
There were two competing theories:
1. The brain first does a recognition pass (that's a house, that's a person, etc.) and compares the two eyes to see which objects have moved.
2. The brain compares the two eye inputs first, at the "pixel" level and figures out which pattern of pixels has moved, then afterwards, applies recognition to the resulting 3D image.
Magic Eye would only work if #2 is the correct theory (because in Magic Eye, there is nothing to recognize until AFTER you convert to 3D).
Good old vdiff: https://catb.org/jargon/html/V/vdiff.html
Visual diff. The operation of finding differences between two files by eyeball search. The term optical diff has also been reported, and is sometimes more specifically used for the act of superimposing two nearly identical printouts on one another and holding them up to a light to spot differences. Though this method is poor for detecting omissions in the ‘rear’ file, it can also be used with printouts of graphics, a claim few if any diff programs can make. See diff.
An interesting variant of the vdiff technique usable by anyone who has sufficient control over the parallax of their eyeballs (e.g. those who can easily view random-dot stereograms), is to hold up two paper printouts and go cross-eyed to superimpose them. This invokes deep, fast, built-in image comparison wetware (the same machinery responsible for depth perception) and differences stand out almost immediately. This technique is good for finding edits in graphical images, or for comparing an image with a compressed version to spot artifacts.
Front page of HN. Funny to imagine thousands of people sitting in the office crossing their eyes at their computer screen right now.
All it did was hurt my eyes. I'll opt out of playing, superpower be damned.
I think the key is not "going cross-eyed" as much as it is relaxing your focus until the images merge. If you intentionally cross your eyes, it hurts. If you de-focus/relax your eyes until the images merge, it doesn't hurt.
Relaxing focus for me doesn't cause merging or cross-eyed effects, it causes my vision to go too blurry to do anything lol
i had the same thing where best i could get when i relaxed was a narrow merge, and when i crossed my focus was too close to my face to be helpful, plus strain.
sudden clicked after fully crossing 5 or 6 times and then relaxing and was able to hold the "3rd image" very easily. felt like magic, even hardest difficulty was obvious
For me it just does not work right now. Maybe I have bad eyesight, I wear glasses and am past 40. I believe I was able to do this trick in past though. At the very least on psychedelics (various kinds). This also made me able to relax my eyes more, wheras I normally have too much pressure on them according to optician.
That's more for traditional "magic eye" pattern stereograms where you want to relax your eyes to look off into the middle distance behind the subject instead of intensely focusing on something unnaturally close to your face.
I didn't spend the time reading the comments to see if this has been said already, but crossing your eyes works but learning to diverge your eyes is better in some situations. It's easier to learn to cross because you can just look at your nose, and you can bring together two images that are further away by crossing than by diverging. But diverging is the way we are normally (when looking across the room say instead of at a book in front of us) so it's more comfortable.
Interesting, what kind of situations does it come in handy?
Wait, that's not crossing your eyes, it's uncrossing them. Ordinarily if you look at something nearby, your eyes aim at a common spot. But when viewing a stereogram, you need to convince your eyes to aim at a spot more distant than the subject.
This is easy with practice, however IMHO it helps to be significantly nearsighted. Then you simply take off your glasses, and can look at something nearby with infinity focus, which is naturally associated with uncrossed eyes.
I don't know whether it's possible to train yourself to diverge your gaze, i.e. stereoscopically see images that are separated more than your pupil distance. Certainly I can't do that.
For spot-the-difference, crossing your eyes is more effective and easier to "dial in" than uncrossing them. You're essentially making each eye look at the opposite image. If you try uncrossing, then you need to make sure the images are at the exact correct distance to cause them to overlap with that technique, because you can only uncross your eyes enough to look straight ahead.
Is that true? It seems that our eyes are mechanically capable of looking in divergent directions, what's the reason that we're not able to "uncross" them beyond looking straight ahead? (Edit: Anecdotally I can confirm for myself that I'm not able to do it, so wondering if there's anyone that can.)
From a control system standpoint, if you have one control that rotates both eyes the same number of degrees left or right to determine gaze direction and another to rotate both eyes the same (positive) number of degrees inward to control fixation distance, you can't specify the left eye rotated left of center and the right eye right, even if each eye physically can rotate that way. Not sure if that's how eyes actually work though.
Looking uncrossed at the images in the article on my phone, I can easily achieve the effect uninterrupted between fully stretched arms and about half that.
Sure, but that's the limit. I didn't say it was impossible, just that crossing your eyes basically works all the way up to your nose.
It’s a good thing that properly designed stereograms take this into account and don’t require you to uncross your eyes past that point.
That's because you have to find the distance between your eyes and the stereogram to make it work. Crossing your eyes is easier because your eyes can turn inwards far more than they can turn outwards, so it works at more distances.
While intuitive, I’m not so sure. I look at the center line and slowly cross my eyes until the 3rd image slides into place and then I get focus lock. At no time do I feel my eyes uncross and go the other way. Hmm!
Both work equally well if you just want to spot differences. Cross-eyed view is somewhat easier to do, since people naturally cross their eyes when looking at something close to their face, but there is no natural reason for one’s eyes to diverge. But cross-eyed view also gives a subjectively smaller image, and is also not the usual way autostereograms are made to be seen.
> but there is no natural reason for one’s eyes to diverge.
When you’ve finished looking at something close to your face and your eyes need to uncross. So you do that eye movement while still holding the image close to your face. Note you are looking “past” where the image is. As long as the image is closer than your infinity focal view you can do this, it doesn’t have to be close to your face necessarily, Magic Eye posters on walls do work.
See my other comment about cross view vs parallel view, looks like you can do one vs the other and the author can do the opposite.
Wow. Thanks to MarkusWandel I discovered I can focus images while crossing my eyes and finally understood your comment. I've always done the "uncrossing" since I was a kid.
1. Get a bit closer to the screen so you can see both images clearly.
2. Now, cross your eyes and aim to overlap both images.
3. Draw the rest of the fucking owl.
Seriously. Ever since my physics teacher in high school tried to get the class interested in stereograms, everyone and every article I see talking about it treat "crossing your eyes" as an atomic, trivial step. It isn't. I for one have no first clue how to do it, it's not a distinct operation I know how to perform. Perhaps this is because I am nearsighted and wear glasses.
Still, I wish articles like these focused on explaining how to do the whole cross-eye thing, because once you master that, everything else becomes instantly self-apparent and doesn't need further explanation (I know because I did manage to accidentally cross my eyes once or twice while looking at a stereogram, so I know how the effect looks like).
EDIT: FWIW, I compensate by using another trick for diffing documents with Mark I Eyeball - get them printed on separate pieces of paper, put one on top of the other, and hold in front of you with some bright light behind you (Sun, or your phone's flashlight, will do). Not as good as crossing your eyes, but something I can reliably do.
Super cool. It works for me. I love magic eye stuff.
I have strabismus and have always been good at these games. I wonder if it helps me for similar reasons? The examples on his page were pretty easy for me, though the universe one took maybe 45 seconds.
human stereo vision processing has incredibly sophisticated noise filtering capabilities that are still hard to replicate in software. The shimmering effect people report is essentially your visual cortex highlighting areas where the stereo correspondence fails.
You can use this same technique to view glasses-less 3D (stereoscopic) images. It's also fairly easy to create your own. Take two photos but offset the camera lens by approximately eye-width. Open the image editor of your choice and place the images side-by-side. View the composite image cross-eyed and you are now viewing a 3D scene.
Also worth noting there are 2 versions of this kind of cross-eyed focus depending on whether your eyes are focusing on a point in front of or behind the actual image. This determines which side the left and right eye images should go on in the composite. I find it easier to focus on a point in front of the images but IME most examples online are for focusing on a point behind the image.
Well this is interesting. I was able to find the impossible one within 2 seconds without crossing my eyes. The easy one took about 5 seconds, 3 seconds for hard. I've always been hyper-vigilant with patterns (to a fault), so not sure if that's playing into this.
Is that what other folks are experiencing also? I see most comments are trying it with their eyes crossed, but what about without?
EDIT: ok I just watched the video. No eyes crossed. For the balloons one I beat out the girl in the video by 2-3 seconds. For the birds about the same. The skittles one tripped me up, couldn't find it. The other few I found around the same time, the lights at the end I didn't find in time either. It seems I'm quicker when there's not too many colors involved. Still that's spooky.
I've got -7.5 myopia/nearsightedness in both eyes, with astigmatism. As a result, my eyes can easily go out of focus to do Magic Eye or this type of thing. The bonus superpower is, if I take my contacts out and get really close up on something, it's like I'm looking through a microscope; if I happen to have glasses on, sometimes I can also catch the light and focus in just the right way to further magnify what I'm seeing already zoomed in. In those instances I see whatever's reflecting through the glasses, so mostly eyelashes and skin/pores, but it's fascinating nonetheless. Can't see a damn thing beyond the tip of my nose without corrective lenses though LOL
Same vision, and I found it hard to do at first- but super cool when the image appeared crystal clear!
Weird timing. I dunno why this works but I've been using it to see mice.
You see, I noticed that I have a mouse problem in my garage. I figure if I've seen one mouse, there are probably more. So, I stood on some stairs in my garage and crossed my eyes to sort of blur the scene. It allowed me to catch movement more quickly and I was quickly watching multiple mice run around the edges of the area.
Hmm. I noticed in lectures, if I stilled my eyes, most of the field of view would grey out, except for areas of motion (eg a lecturer's head or writing arm) which appeared normal. After motion stopped in an area, it would slowly grey out. When a motion started, its area would snap to normal, making it easy to spot onsets of motion. Eventually my eyes would twitch, and the whole field would refresh.
I first read about this back in the 1980s, in an issue of Science Digest. Couldn't find a link or reference on short notice, but here's something from the American Academy of Ophthalmology that explains the phenomenon, with an experiment to see the blood vessels in your eye:
https://www.aao.org/eye-health/tips-prevention/experiment-se...
Apparently, the brain tends to ignore visual stimuli that don't change over a short period of time, which allows you see "around" the blood vessels passing through the middle of your eye. By closing your eye, and moving a penlight around against your eyelid, you can make the vessels cast a shifting shadow on your retina that makes them visible.
The reason you usually see everything out in front of you is that various actions cause your eye to shift about just a little, just enough to cause the image on your retina to shift about enough for the brain to notice.
I've done this in the past with bugs in the grass. If I stare at a fixed point, I start seeing each individual bug moving through the grass, whereas normally they would be really hard to spot among all the fine details of the ground and grass blades.
That seems like not the same thing though, right? You're not doing a diff on two images, you're just losing resolution so you can direct more attention to movement.
I think it's because our peripheral vision is able to observe movements faster.
A ton of comments in here saying this is easy/old hat for them.
Well I'll be the one to say this blew my mind. somehow creating the third middle image, being able to relax my eyes and even scan around this composite image actually made me giggle out loud on my laptop, a very rare occurrence. Thank you to the author.
Using this trick, I wrote a program for 3d plot visualization in the 80-s. It computed two projections of the plot, as if looked by left and right eye, and printed them side to side on the thermal printer. If you looked hard enough, you can bring the two pictures together and see a 3d picture!
Who's been doing this since they we're maybe 7 years old :)
Checking in!
I’m frequently baffled by how unaware most people seem to be about the absolute basics of how their eyes work. Like, people don’t even seem to be aware of how their stereo perception is largely made from two images, or any of the implications that has. I actively think about the two images maybe dozens of times per day.
Chill out, that's a bit of hyperbole isn't it? This is just a trick for doing a spot the difference puzzle. It's not exactly a daily task most people are thinking about.
Most people at least understand that stereographic vision has something to do with 3D perception because we've all closed 1 eye before.
It’s a useful way to compare visual things, which comes up in all kinds of contexts other than these puzzles.
Yup I used to do this with tile floors as a child.
I figured everyone because I had a puzzle book that instructed readers to do this.
We've had these stereoscopic books with hidden images and I never saw any. So I've been failing at this since 7 years old – does that count?
I didn't know this had a name or was considered a skill. I've done this since the 90's when those magic eye books became popular.
I even managed "impossible mode" in 2 or 3 seconds.
I've used this to quickly read through a few hundred page documents given to us only as a scanned pdf which was too low quality to run ocr (at the time) on. The sleazy counter party was very upset when I came back with notes on them not adding the changes we asked for on the drafts they sent back within minutes of them sending them back.
I can’t parse your second sentence.
Uncross your eyes! :-)
(They're saying that the person who send the contract was trying to trick them, and that they were upset when the trick was caught.)
a counterparty is the other person you're signing a contract with who sometimes lies to you and says they changed things when they didn't
It was the grammar I had trouble with, not the vocabulary. A comma before “within” would have helped a bit.
There's a video game of this called QuickSpot. Back in 2008, this was one of my favorite games for the Nintendo DS. It trains the ability to spot little differences quickly. Sadly, outside of winning a barely known video game, it's not a super useful skill.
https://en.wikipedia.org/wiki/QuickSpot
As a kid I learned to see stereograms in 3D by crossing my eyes. Exact same technique. Comes in handy for Mars images today.
I can get the overlap to lock in, but the simmering effect is weak and difficult to pick out. Probably still faster than exhaustive search, but I don't feel like I'm at superpower level. Maybe my brain favors one eye more than the other? I know I have different glasses prescriptions for each eye.
It tried just after waking up, using my phone's screen, and it worked immediately. Not exactly a pleasant thing to do, but it does work as described.
I find it very easy to overlap images, I think because of the eye exercises I had to do as kid.
I don't recall what these exercises were for, but there were two:
1. Stare at this image of two incomplete cats, and merge them together into a single complete cat: https://www.google.com/search?q=eye+muscle+cat+card
2. This strip of cardboard has a number line on it. Put one end half way down your nose, perpendicular to your face. You will see two lines. Merge them at their furthest point, then merge the next nearest point, repeat. (I think this is called the 'Brock String Exercise', but can't find an image similar to the one I recall.)
Almost certainly a lot of the people saying they are ”crossing” their eyes are actually ”uncrossing” their eyes; focusing the eyes straighter than what would normally happen on the surface where the image is laid out.
This is also how the legendary ”Magic Eye” books were supposed to be viewed. Not by crossing the eyes.
Feel like people who are old enough to remember that 6 week period in the 90's where those Magic Eye 3d Stereogram pictures were everywhere have a big advantage here.
You can also use this method to watch 3d movies without vr googles.
I've heard about this before, but I've never actually managed to do it until just now. I needed to sort of "tune the parameters" a lot so that my eyes were crossed but also focused, since I've had a lot of trouble actually getting them in focus when I'm doing it, and the effect isn't as pronounced as I expected it to be
I think you're still not doing it quite right. The effect is really quite obvious and pronounced.
It took me some attempts but I agree, it's very obvious, the 2nd image made it glaringly obvious after I managed it well on the 1st one.
My eyes get very watery after just a few seconds though, curious to hear from others how common this side-effect is.
Wow! It really works. The missing bean "pops" out at you. The hardest part is getting your brain to focus on the cross-eyed virtual center image.
Learned it from Magic Eye books too! But using it for spot-the-difference is way more practical - saves so much time compared to staring at two pictures. Kind of feels like having X-ray vision for finding differences
An alternative technique called “divergence” [1] (pulling your eyes apart) is significantly less straining on your eyes than crossing them (“convergence” [2]) while being equally as effective spotting differences, even on video. It’s also what your eyes naturally do when you watch stereoscopic 3D with tinted glasses—the stereoscopic images are pulled out (divergence) not pushed in (convergence/cross-eyed). I’ve been doing this since I childhood. If you get good at it, you can watch side-by-side 3D videos in 3D with just your naked eye (e.g. VR)! I believe there’s a reddit covering the more prurient variety of that.
[1] https://en.wikipedia.org/wiki/Vergence#Divergence
[2] https://en.wikipedia.org/wiki/Vergence#Convergence
This is what I do, the only issue is that I don't have nearly as much "range" with divergence as I do with convergence, so I have to make the pictures as small as possible when using it to line up two images (as opposed to autostereograms, which usually have a much smaller divergence offset).
Do you have a training method for divergence?
Similar to the finger moving closer and closer to the upper nose technique, for convergence.
It's a little more abstract since you don't have handy moving-reference-object like your finger, but: Place the picture in front of something deep, like a long hallway. Look off at something in the distance behind the picture, like the end of the hallway. Notice how the edge of the picture is a double image. Focus on gradually resolving the edge of the picture down from double-image to single-image, and then do the reverse by looking down the hallway again and seeing the picture go back into double-vision. Just keep practicing that until you get the feel for controlling your depth perception and then try holding the same depth of the hallway while you turn your gaze to the picture and try the same action with your eyes.
The stars puzzle helped me find a speck of dirt on my phone screen.
The funny thing about the stars image is this is a common way to find asteroids, comets. It's not limited to just those. Only instead of a bunch of cross eyed astronomers, they overlay and align the images and do subtraction/difference filtering to see what's left. For comets/asteroids, the dot of interest will move between frames. Even just playing back the aligned images as a timelapse can reveal motion.
Nice to see someone discover this! I've always been partial to spot the differences and crossview images - I am able to cross each eye independently of one another, which makes overlapping these sorts of images very easy. For example, I could cross my right eye, while my left stays perfectly still. This causes instant double vision, and relaxing how crossed the eye is lets me line the images up very quickly. It's fun to do in places with a repetitive wall texture, too - seeing something in real life while adding a faux 3D effect on top of it is kind of trippy. Probably my most useless skill, but a fun one regardless.
This whole time it's been a Magic Eye problem? Geeeeez. This would've won me so many random challenges over the years.
This trick is interesting to me as someone who mixes records. I (and mixers in general) have a lot of different tricks for making mono audio objects in the mix feel stereo or have a sense of width or depth.
Examples include:
1. Delaying the left or right channel by a few ms (Haas effect).
2. De-tuning one of the channels by a few cents
3. Boosting an EQ band on one channel, with a complimentary cut on the opposite channel.
...and many more.
These are usually very subtle changes that our stereoscopic ears have no problem detecting.
In any case, when we need to do some forensic searching for possible differences between two near-identical channels we'll invert the polarity on one channel and then sum them. The resulting delta sticks out like a sore thumb and highlights even then tiniest differences between the files.
So it's fascinating to discover that we can easily do something similar with our eyes to find the differences.
You can also use this to display 3-D images. You have a stereographic projection of your image (like those kids' view-masters) and then just cross the eyes and look at the middle image. Only since the 2 images are slightly different, you can have the middle image be 3-D. It takes a bit of practice though and causes eye strain (at least for me)
It's not a great way of showing the image, but it'll do in a pinch.
I can't seem to do this, it seems impossible for me to cross my eyes. Hmmm.
I'm amazed that there's so many comments and yet not a single one is pointing out that the coffee bean is missing from the _right_ side of the image. Not the left.
that's why they mirror one of the images in "find the differences" in puzzle competitions, e.g. USPC https://wpc.puzzles.com/uspc2024/
This did not work for me. I was able to invoke a middle image, but there was no shimmering. After I found the difference the old-fashioned way, I realized that the middle image showed the distinguishing feature as it is on my non-dominant side.
To really blow peoples' minds use both hands to tap the differences, keeping the left hand for the left image and the right hand for the right image!
From your POV the images are merged so your hands will look like they're tapping a single image, but from the audience's point of view you look like a savant with multi-attention!
Jokes on you, my eyes don't work together so I can only see out of one at a time!
There's dozens of us!
I spent weeks doing this, looking at stereoscopic (?) images of protein structures, while a grad student in molecular biophysics. I got so that I could see the overlapped images pretty much instantly. But I'm having a hard time getting it now, even on the easy one.
Every Asshole knows this trick for targeting spacecraft
https://youtu.be/XGdjKvivJA8?si=lRrfl6rHzAsE7nEO
I've always thought that ability to unfocus the eyes might be related to mental focus. If you have difficulty staying on topic, or a diagnosis of ADD/ADHD or whatever {I'm not equate these} AND find it really hard to do magic eye images... Then please take part in my 'totally scientific study'TM.
Upvotes, I agree, I have mental focus issues and can't do magic eye (upvote)
I have mental focus problems, magic eye is easy for me. (downvote)
Downvotes, I disagree (downvote)
{I should have done an actual survey, sorry; felt cute might delete.}
I found it almost instantly, which was by dumb luck.
But in the following few moments, seeing two nearly identical photos side by side soon made me think of stereograms, since I'm into them, and have shot a few in my lifetime.
I then used my eyes to overlap the images.
In binocular overlapped view, the difference loudly draws attention to itself, because it flickers between the two eyes.
It's almost as if there were a blinking LED saying "here it is!"
Instead of crossing your eyes and attempting to focus, what can really help relax your ocular muscles is to do the opposite: look "past" the images into the distance until the images overlap.
Wow! That was amazing!
I've been using this to do quick source code diffs for years. I started back on the days of printouts.
Is the technique to this exactly the same as the technique to view a 3d stereogram image?
I was able to get a 3rd image to be clearly visible in the middle doing this, on the 2nd image I could definitely seem some spots appear that lead me straight to 3 of them but didn't work for me on the other 2 images.
The left-right full-image stereograms... but those are less common than the pattern-based "magic eye" stereograms. Those are the reverse of this - in the linked image and the left-right full-image stereograms, they're done by crossing your eyes to a point closer to your eyes than the original image.
The pattern-based "magic eye" stereograms are done by looking through the image to focus on a point deeper into the screen further from your eyes.
The latter I think are less painful because they use the more natural depth-perception distances of your eyes instead of using what feels like more unnatural positions, but that might be my bias because I'm a bit farsighted. Maybe they're just more common because they're visually inscrutable at first and so you get the "reveal" of the 3D contour from a single large image instead of two already-visible small ones.
I that not the entire point with those "find the difference" pictures? To teach kids how to do just this ?
I use this technique to get web layouts pixel-perfect with the mockup, just put both windows next to one another and superimpose them with your eyes. Works great. There are tools that do this by overlaying an image with 50% alpha but it doesn't work as well.
Last year when there was a bunch of fuss about Kate Middleton not having made any public appearances there was a minor flap where people claimed that a photo she'd released was just an edit of an earlier photo.
There was a tweet presenting two photos, one old and one purporting to be new, where she was holding strikingly similar poses. The claim was that the new one was just an edit of the older one. I used this technique and immediately the minor differences stuck out like a sore thumb- her hand was rotated more in one, her hair was laid differently, etc.
Any recommendations for when you can't get the images to quite overlap? I feel like I can get 75% of the way there, but then they start going the other direction. I can do magic eye easily.
Use your browser to zoom out and make the images slightly smaller
That's how I used to help my grandmother when I was a little child. She always used to remark that the last one (5th) was the most difficult to find.
I have been doing this forever, if you get the high score over a certain threshold you can get a free game (400,000?)
I would usually get accused of memorizing all the pictures.
You will get bored or a headache before you stop getting free games using this technique.
You can get stifled by the older machines with faded CRT screens. The newer LCD (that's how old these games are...) are usually better to play on.
“Impossible mode” was the easiest for me - took a few seconds. Probably due to the aspect ratio and the size of the images on my phone screen.
This does not work even in the slightest. When I cross my eyes, the image becomes wayyyy too blurry and its hard to keep it in the center for more than a second
Wife was not impressed. That hit home haha.
I've been doing this since I was a kid as well. When I was younger some restaurants would have video monitors with games on them, and one of them was spot the difference. I essentially maxed out the score and still held the highest score when I came back in town years later. I wonder if its still around...
There are some great examples and detailed explanations IMO of this general phenomenon in the book "How the Mind Works" by Stephen Pinker. It essentially discusses how your brain is doing statistical work to build the 3D model from these 2 stereoscopic images.
This is exactly the same skill needed to see 3d pictures (aka autostereograms).
i certainly used this trick back in my college days, prompted by a similar technique for "seeing" 3d stereoscopes on a computer monitor. I feel like i learned it somewhere on Eric Weisstein's Mathworld because the 3d objects viwer app let you split the image into two stereo images. Unfortunately java applets have been banished from the internet landscape.
Wow that's interesting — trying to cross my eyes produces hellish jitter.
I suspect it's because my left eye is slighty lazy.
But I was able to superimpose the right cat picture onto the left one (it's a lot harder for the more complex sky resort picture). It's pretty eerie, the right picture just slides right up the left one (I did need to figure out the right distance for it).
It doesn't help me pick out the differences though, I mostly only see the right picture, and if try to focus my left eye, the right picture slides out. Still, intersting.
I remember doing this as a child on our TV that had a picture-in-picture setting. I would set the same channel twice and cross my eyes pretending that it was 3d TV.
How does that work when the two images are different sizes and overlapping? Did your PiP mode have a split screen option? The ones I've seen only allowed moving where the insert was placed (which corner), but it was always a PiP and never a split screen.
Yes, it had a split screen option where the two images were the same size and side by side. Can't recall what kind of TV it was... perhaps a Sony?
I couldn't do the cross-eyed thing, but it took me maybe 20 seconds to spot the difference just by looking at sections of the images. But I'm not sure that would have worked had the missing bean been buried in the denser part of the photo.
More things you can use this for:
”Are these two things the same size?”
”Are these things that are supposed to be evenly spaced actually evenly spaced?”
”Are all these things straight/at the same angle?”
”Is the wallpaper pattern aligned everywhere?”
”Is that surface using a repeating texture?”
Autostereogramming it doesn't help me lol
If it's perfect, the overlapping regions just merge in color, i.e. the cat's paw becomes off-white. If it's not perfect, I still have to attend to which parts are popping in and out. In both cases I still have to compare the merged view to the left and right hand sides.
Although it is very nice for illustrating each eye's contributions to the merged view. Just not an attention-saver.
This same technique can be used for a 3D effect: https://old.reddit.com/r/CrossView/
Stereograms have been used in structural biology publications for many decades now. Google 'stereogram structural biology'
I tried crossing my eyes, but it’s not working for me; I keep seeing things blurry. Maybe I’m doing it wrong. However, I solved the first two puzzles. For the last one, I just guessed randomly. My guess wasn’t exactly correct, but it was close, just a little distance away.
One thing I noticed: because you're tricking your eyes into thinking they're observing at a different distance, your brain doesn't seem to correctly account for head tilt (my theory of the diagnosis). Anyway, I think you're head must be exactly level with the image or you'll get double-vision/blur
It’s way trickier if you have astigmatism
Claims have been made (outside the medical mainstream) that regularly practicing crossing your eyes helps stave off presbyopia. One does get better at seeing stereograms with practice, so it seems like it at least improves some type of muscle control.
Okay, but my eyes hurt now.
uh dunno.
25y ago, i was working behind a 30" tube monitor (a ~35kg hog), with 1 inch thick frontglass.. and one day, one of my eyes started to focus on the (closer)outside of the glass, the other on the (farther)inside of the glass. Could not shake that with closing/blinking. Worse, later, when i got into the car, the closer eye focused on the windshield - instead on the landscape ahead.
Took 1 week of everyday 1-2 hours staring far away at the ocean, to revive. AND removal of the monitor :/
My Piano teacher used to have this book on her coffee table with images like this. You could blur and cross your eyes, and the image would combine to become 3D.
But I never knew this technique could be used to spot the difference between images. Very cool discovery!
I always feel like I'll permanently see cross eyed if I keep doing that. It doesn't help that I was accidentally hit in the head by my double's partner racket in tennis and spent like a minute or two walking around seeing double. Not fun.
Some repeating tile patterns like stripes will cause my eyes to do this automatically and it's really weird and annoying because everything else gets blurry. Fun trick though.
This is effectively how Pluto was discovered (not cross-eyed, but with a tool to help): https://airandspace.si.edu/stories/editorial/finding-pluto-b...
I was hoping to get a new superpower today, but when I was young I was cross eyed. I got this corrected through surgery and can no longer cross my eyes.
Wait, this is news? that's how I always solved those puzzles, I thought everyone did that
Dammit!
I can't uncross, now!
https://www.youtube.com/watch?v=qaz2hxZLycY
It works for me like every tenth time I cross my eyes to look at a "spot the difference" picture. I don't know how it works for people instantly.
I picked this up during the magic eye craze of the 90s, and I will never not find it hilarious how people get shocked at my ability to find the differences. I always share the skill too, it’s one of those things people find impossible until they get it and it’s easy.
Please stop using that RSS icon on your "Subscribe" button if you don't intend to provide an RSS feed.
I can produce the third image by crossing my eyes, but one eye dominates and all I see is a cat with three stripes on its head. :(
After a short period of training, I got to the point where I can see the third image which I can focus on. However, the differences are very subtile and don't stick out at all :/
Try the second test image (the one labelled "Hard", with the snow). That one was far easier for me than the first (the cat one).
Easily defeated by arranging the images vertically.
Or at least, makes it a LITTLE bit harder.
I used to use that trick with some arcade game that was popular in bars in 00s Spain. People were just impressed!
Validates a claim in the predictive processing paradigm. The diff between actual and expected is what matters to error correction. That's where all the relevant information is.
This is just incredible!
I’ve tried this in the past without luck, but suddenly I can do it now after reading about the subtle “shimmer” effect. Very cool!
I've never been able to 'lock' the two images together like this with my eyes focus. That was incredible.
Doesn't work for me. Just like stereograms. I just don't know how to "tell" my eyes to cross. Maybe similar to how I didn't figure out until I was 20-something how finger snipping works. Maybe by the time I'm 50 I can cross my eyes...!
You dont 'tell' your eyes to cross, you just look closer or further away. Try looking at the image at normal distance, whilst imaginging that you are looking into the distance at a beautiful view or at the horizon on an ocean. It is this difference in distance focusing which causes the illusion.
Actually, given enough practice, you can literally just get your eyes to do it. I started doing magic eye puzzles as a kid and loved it, so just eventually learned how to control my eyes in that way. Even today, if I see any repeating pattern, or even anything vaguely similarly shaped, I can’t help but do it
When they snap together it feels soo good…
Well actually, I've been telling my eyes to cross since I was a child. I can't describe it, it's like tensing a muscle in the eyes or something and you can control the angle with the tension.
I can even rotate my eyes! Did you know we have muscles for that? I trained it in the mirror - try tilting your head and look at your eyes REALLY closely: they rotate a bit to cancel out the tilt.
Whenever I try to do this, the most I get is that the two images touch. The cats in the example are holding paws, but they never overlap. I've been trying to make this work since the old magic images from the 90s, but I've never managed it. I wonder if there isn a hardware limitation related to my eye configuration.
The never work for me because my eyes don't work well together. Just not team players. I'm almost always looking through just one or the other, annoyingly usually the one that would least be preferable.
To do it with crossed-eye view, try looking at your finger and slowly moving the finger closer to your eyes until you see a third image come into view in between the two on the screen. At some point your brain will/might let you focus on that image.
half-off-topic..
i have ~1 diopter shortsightness. Was less before, slowly going up. So screens are getting blurrier. Have glasses but still try avoid using them.
If i put the (flat edged) TV remote control at about 10cm from my face so it horizontally shadows lower half of both eyes, i see perfectly (without any glasses).
go figure..
de-clickbaited: to spot minor differences between two images, view them like stereograms
Image worked but when I tried with text it did not work. Is there some trick to it?
I used to play this game with a friend when we were at the pub, once we start struggling spotting the differences we know we’re drunk
This is called 'vdiff' in the Jargon File: https://jargonfile.johnswitzerland.com/vdiff.html
Wonderful! with your write-up, I was able to “see”.
This is incredible! Works unbelievably well. Thanks for sharing!
I cannot do this by crossing my eyes (focusing on a point between you and the image), I have a hard time getting the cross to stay consistent and it never really "locks in" for me. Instead of crossing my eyes, I unfocus them, effectively look through the image. Once I get the repeating part to overlap cleanly, after a second or two, my pupils adjust their focus and the image fades from blurry to clear in a really satisfying way and kind of "locks in" in a way that takes little to no effort to maintain. With a bit of practice, I can even move my eyes around and look at different parts of the two overlayed images without distrupting the effect at all.
I don't know if it's just my brain working differently or if a there is some confusion in the discussion between crossing your eyes and focusing through an item.
You can also now free-view stereo image pairs. Congratulations.
I feel old knowing https://en.wikipedia.org/wiki/Magic_Eye
This is exactly why I read HN
That's so cool, thanks for sharing this. I managed to do all of them, in the impossible one I identified correctly the area, but couldn't pinpoint the difference.
The superpower being writing clickbait titles for trivial posts
I knew some people who used it to compare aerial photos (though generally a special device with mirrors was used).
> though generally a special device with mirrors was used
Maybe this: https://en.wikipedia.org/wiki/Blink_comparator
No, a modification of this: https://en.wikipedia.org/wiki/Stereoscope
This is a game mechanic in one of the trials in Ace Attorney Chronicles.
I can overlap. But still need to match overlap with anyone.anyway interesting
Woah that is amazing how quickly I was able to apply this.
So cool!
That's fun, it worked for me as well. I could spot the difference in all images, including the 'impossible mode'.
Learned this at a young age with the Highlights magazines at the dentist.
Fuck it does work...
okay, this is so cool. thank you for the new superpower!
Wow. That’s insane! With the trick I can somehow solve them all!
Every 80’s kid knows this trick from those old books where you cross your eyes to reveal images.
This is the coolest thing I have seen on here!!
I was really good at the random dot stereograms. This is a really cool recasting of that skillset.
I think thats the best part of this skill. Everyone did 'Magic Eye' images as a kid, but to be able to take that useless skill and apply it to something more useful and interesting is really cool.
Hah, old trick, I read pull requests this way for years
It's a sailboat!
Hah, Kevin Smith caught some flak for that one:
" Someone called out Kevin Smith for this on one of his podcasts. According to Smith, on the day of filming, he asked if the picture really was a sailboat, and the prop master said no. When Smith started questioning this, the prop master said that a) it flashes on the screen too quickly for anyone in the theatre to notice, and b) VHS was too low-resolution for people to freeze-frame it to try it at home. So Smith let it slide.
Smith summed up, "Now, thanks to Blu-Ray, I get people pointing this out to me all the time!" "
https://www.reddit.com/r/MovieDetails/comments/9lf52b/in_the...
A parallel processor is you!
Damn, it works exactly that well.
all i managed to do was make myself very dizzy
Who's been doing this since they were maybe 7 years old :)
Do people not know about this?
Very cool. Even the impossible mode one was relatively easy!
For some reason when attempting this my neck starts cramping
dang it i just did this on a zoom meeting. hopefully no one saw me trying to cross my eyes
I've done this on these game machines 30 years ago when I was 10. I'm baffled that there are still people who have to figure this out.
I was able to do it for the first time after reading this webpage with the technique, cool!
I appreciate the sentiment but "overlay the images by crossing your eyes" receiving that kind of incredulous reaction is really funny and kind of sad for me. I hope it's just amateur editorializing.
Neat. If this isn't working for you, try on mobile. It's easier if the images are small.
This helped, thanks.
You can also just back away from the screen. For the 3rd one I had to back up about 6 feet from my monitor before it clicked into place, once it is in focus you can move closer to see the difference better.
ITT: everyone telling us their stories about how great they are at stereograms. We get it, you're all super special.
This trick had been used in practice to detect fake banknotes and coins, with a device like a two-sided periscope. It allowed a bank worker to put a real coin on one side and the tested sample on the other, so that any differences can be immediately apparent.
yep it’s just like those magic eye pictures that were big in the 90s, once you learn how to see those instantly you can do this trick also
This is also how I used to do Magic Eye images when I was a kid. Although the stereoscopic image was inverted on the z axis, it was a lot easier than to cross eyes by looking further out into the distance
This is how I help my family when they're stuck on "spot the difference" steam games. It also takes literally any fun out of them, the actual game has to come from not (just) spotting differences, because that task is trivial.
Come on, I've been doing this since I was like 4 years old, this can't be news for anyone, Am i right???
Yes, I didn’t think people would be so amazed by it either. Like it’s mind-blowing that this works or has been thought of. But we first did it once as well, some people just discover it late in life I guess (or not at all).
Incredible! This technique is also used for the 3d visualization of protein structures, it was called "cross viewing": https://imgur.com/cross-views-are-commonly-used-to-view-prot...
You cross your eyes to get the two images to line up, hold it there and then try to adjust the focus of your eyes. It's a neat skill to have.
I found the toolbars and stuff around the edge of the image made it difficult for me to lock onto the crossview image in your example; surrounding it with more blank background makes it easier for me: https://imgur.com/a/NizzRgo
I'm not sure this works if you have astigmatism
Having similar acuity in both eyes made a huge difference for me. I'm somewhat astigmatic but was able to do this eye "uncrossing" trick just fine. I had a significant loss of acuity in one eye and that's what left me unable to do this (or to watch 3D movies).
I have a small astigmatism (and wear glasses) and I was able to do it, but I feel like if I did any more today I'd have a headache.
I did until it was corrected with LASIK a year ago, and I could still do magic eyes, both with and and without my glasses on.
Not working for me
Thanks! now I have a migraine
and now my eyes are stuck this way forever
A new way of doing git diff, leave both versions of the code side by side and cross your eyes.
New business idea: git diff, but it uses Mechanical Turk to hire an army of cross-eyed diff spotters.
There is a wonderful stable diffusion prompt here.
I sure didn't expect there to be a plausibly work-related angle when I came to this thread
Somewhat related, but I've been using the Semantic Diff extension in VSCode, works better than standard git diff.
My thoughts exactly. Could be done with a git diff in a VR headset
If you’re already spending the computing effort to create the VR image…
/s