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!

Wow. Thanks to MarkusWandel I discovered I can focus images while crossing my eyes and finally understood your comment. I&#x27;ve always done the &quot;uncrossing&quot; since I was a kid.

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.

&gt; 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.

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.

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.

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.

Is that true? It seems that our eyes are mechanically capable of looking in divergent directions, what&#x27;s the reason that we&#x27;re not able to &quot;uncross&quot; them beyond looking straight ahead?
(Edit: Anecdotally I can confirm for myself that I&#x27;m not able to do it, so wondering if there&#x27;s anyone that can.)

For spot-the-difference, crossing your eyes is more effective and easier to &quot;dial in&quot; than uncrossing them. You&#x27;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.

Wait, that&#x27;s not crossing your eyes, it&#x27;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&#x27;t know whether it&#x27;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&#x27;t do that.

I had never done the parallel view before either- spent 5 or so minutes at it and finally got it. For me it&#x27;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&#x27;t seen so much depth in a &quot;magic eye&quot; before

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 &#x27;past&#x27; 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!

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.

Which one is in the foreground vs background?

Cannot figure out what is the difference. I can focus on both seemingly without changing anything, even though they aren&#x27;t both in focus at the same time. But I don&#x27;t know what I&#x27;m doing differently, I just move my eyes up or down, adjust a bit, and that&#x27;s it.

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&#x27;re able to see.Basically, it determines whether the 3D view you&#x27;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&#x2F;crossview or r&#x2F;parallelview depending on which one you see.[0] <a href="https:&#x2F;&#x2F;i.redd.it&#x2F;g5ilwgk99r781.jpg" rel="nofollow">https:&#x2F;&#x2F;i.redd.it&#x2F;g5ilwgk99r781.jpg</a>

If you’re already spending the computing effort to create the VR image…&#x2F;s

My thoughts exactly. Could be done with a git diff in a VR headset

I sure didn&#x27;t expect there to be a plausibly work-related angle when I came to this thread

There is a wonderful stable diffusion prompt here.

New business idea: git diff, but it uses Mechanical Turk to hire an army of cross-eyed diff spotters.

Somewhat related, but I&#x27;ve been using the Semantic Diff extension in VSCode, works better than standard git diff.

It sounds like you mock, but: you can do this, or near enough, and you can do it already, and it works really well!0. Pick suitable tool. Firefox works. Notepad++ works. GIMP works. Emacs, not so much, but if you use Emacs, you know that you can fix this1. Load file A into a tab2. Load file B into a tab3. Close all other tabs4. Hold down the tab switch shortcut key and note the resultFor images this is actually pretty decent and I&#x27;ve used it a lot. Good for figuring out what the differences actually are when your image-based tests fail, and similarly after making a speculative change. Let your eyes do the difference operation for you. That&#x27;s what they&#x27;re there for.For text: you&#x27;d be better served by some other kind of tool. But text is just an image with letters in it, so the same principle applies. It does work!(I&#x27;ve previously read a blog post, link to which I of course now can&#x27;t find, about how old-style Photoshop undo was designed with this sort of thing in mind. Instead of working through the operation queue like normal people, it simply switched repeatedly between previous state and current state - the idea being that you&#x27;d make a change that you weren&#x27;t certain of, then press the key repeatedly to see before and after. No need to think. Thinking isn&#x27;t appropriate here anyway. Just let your eyes look at what they&#x27;re seeing.)

A new way of doing git diff, leave both versions of the code side by side and cross your eyes.

I think thats the best part of this skill. Everyone did &#x27;Magic Eye&#x27; 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.

I was really good at the random dot stereograms. This is a really cool recasting of that skillset.

Dammit!I can&#x27;t uncross, now!<a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=qaz2hxZLycY" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=qaz2hxZLycY</a>

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.

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&#x27;d have a headache.

Having similar acuity in both eyes made a huge difference for me. I&#x27;m somewhat astigmatic but was able to do this eye &quot;uncrossing&quot; trick just fine. I had a significant loss of acuity in one eye and that&#x27;s what left me unable to do this (or to watch 3D movies).

I&#x27;m not sure this works if you have astigmatism

de-clickbaited:
to spot minor differences between two images, view them like stereograms

That&#x27;s fun, it worked for me as well. I could spot the difference in all images, including the &#x27;impossible mode&#x27;.

Chill out, that&#x27;s a bit of hyperbole isn&#x27;t it? This is just a trick for doing a spot the difference puzzle. It&#x27;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&#x27;ve all closed 1 eye before.

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.

We&#x27;ve had these stereoscopic books with hidden images and I never saw any. So I&#x27;ve been failing at this since 7 years old – does that count?

I figured everyone because I had a puzzle book that instructed readers to do this.

Yup I used to do this with tile floors as a child.

Who&#x27;s been doing this since they we&#x27;re maybe 7 years old :)

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.

Neat. If this isn&#x27;t working for you, try on mobile. It&#x27;s easier if the images are small.

For some reason when attempting this my neck starts cramping

Who&#x27;s been doing this since they were maybe 7 years old :)

I used to use that trick with some arcade game that was popular in bars in 00s Spain. People were just impressed!

Very cool. Even the impossible mode one was relatively easy!

That&#x27;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&#x27;t pinpoint the difference.

that&#x27;s why they mirror one of the images in &quot;find the differences&quot; in puzzle competitions, e.g. USPC <a href="https:&#x2F;&#x2F;wpc.puzzles.com&#x2F;uspc2024&#x2F;" rel="nofollow">https:&#x2F;&#x2F;wpc.puzzles.com&#x2F;uspc2024&#x2F;</a>

I&#x27;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...

It took me some attempts but I agree, it&#x27;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.

I think you&#x27;re still not doing it quite right. The effect is really quite obvious and pronounced.

I&#x27;ve heard about this before, but I&#x27;ve never actually managed to do it until just now. I needed to sort of &quot;tune the parameters&quot; a lot so that my eyes were crossed but also focused, since I&#x27;ve had a lot of trouble actually getting them in focus when I&#x27;m doing it, and the effect isn&#x27;t as pronounced as I expected it to be

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&#x2F;might let you focus on that image.

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

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&#x27;ve been trying to make this work since the old magic images from the 90s, but I&#x27;ve never managed it. I wonder if there isn a hardware limitation related to my eye configuration.

Well actually, I&#x27;ve been telling my eyes to cross since I was a child. I can&#x27;t describe it, it&#x27;s like tensing a muscle in the eyes or something and you can control the angle with the tension.

You dont &#x27;tell&#x27; 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.

The never work for me because my eyes don&#x27;t work well together. Just not team players. I&#x27;m almost always looking through just one or the other, annoyingly usually the one that would least be preferable.

Doesn&#x27;t work for me. Just like stereograms. I just don&#x27;t know how to &quot;tell&quot; my eyes to cross. Maybe similar to how I didn&#x27;t figure out until I was 20-something how finger snipping works. Maybe by the time I&#x27;m 50 I can cross my eyes...!

I have a slightly lazy right eye, so this has always come naturally to me, but I will say it&#x27;s considerably easier to achieve the false focal lock on printed material— something about screens, even quality ones with high refresh rates, just isn&#x27;t the same.

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.

Same -- much harder to get them to go the other way.  I&#x27;m surprised that cross-eyed random dot stereograms never took off; so much easier to do.

It&#x27;s funny because even if you do the Magic Eye pictures &quot;correctly&quot; (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] <a href="https:&#x2F;&#x2F;i0.wp.com&#x2F;www.magiceye.com&#x2F;wp-content&#x2F;uploads&#x2F;2018&#x2F;10&#x2F;stock_roses_800x656.jpg" rel="nofollow">https:&#x2F;&#x2F;i0.wp.com&#x2F;www.magiceye.com&#x2F;wp-content&#x2F;uploads&#x2F;2018&#x2F;1...</a>

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 (&quot;peaks&quot; were &quot;valleys&quot; and vice versa) due to the way I was focusing. Alas, I never was able to see the images &quot;correctly&quot;.

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 find there&#x27;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.

I can get the images to merge but the differences don&#x27;t stand out.

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.)

Maybe we are the opposite. As a kid, I could only do cross-eyed-focus-in-front-of-screen, but not &quot;focus beyond the screen&quot;. 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&#x27;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 &gt; _ &lt;

Are you able to look around while keeping your &quot;unified vision&quot;?To me, all the differences appeared to be flashing (probably my brain alternates between the pair of images it attempts to &quot;lock in&quot;, or something to that effect).

I&#x27;m great at magic eyes &#x2F; 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&#x27;t that easy (maybe with practice I could get there).  The differences are noticeable when I focus right on it, but when I&#x27;m looking at the whole image it&#x27;s harder to tell what is missing from one eye.

I had trouble finding the &quot;shiny&quot; 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 :)

Yup, I loved Magic Eyes as a kid. This was easy.Nevertheless, I was astonished that &quot;impossible mode&quot; 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.

You know how you can make your eyes see double when you cross your eyes a bit? Do this and you get 4 images. Combine align the center 2 images and your eyes will automatically “lock on”.

How do you do this focusing beyond the screen!?I&#x27;m trying so hard to make this happen. Stare really far in the distance and then move the image in front of my face on my phone. No matter the distance between my face and my phone i can&#x27;t overlap the images.Focus in front of the screen is the easy one. How do you get beyond....

I can do magic eyes, but this technique doesn&#x27;t work for me. My left eye is dominant enough that the whole image just looks like what my left eye is seeing.

I challenge you to use this refocusing ability to pass the Stroop Test: <a href="https:&#x2F;&#x2F;faculty.washington.edu&#x2F;chudler&#x2F;words.html" rel="nofollow">https:&#x2F;&#x2F;faculty.washington.edu&#x2F;chudler&#x2F;words.html</a>You are given a list of color names, written in font colors that are incongruous with the written word. E.g. &quot;Red&quot; will be written in a blue font, and &quot;Green&quot; will be written in a yellow font.You have to say the font color and not the written word.It&#x27;s challenging, but it&#x27;s yet another application where going cross-eyed confers an advantage.

If you&#x27;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.

This same technique can be used for a 3D effect: <a href="https:&#x2F;&#x2F;old.reddit.com&#x2F;r&#x2F;CrossView&#x2F;" rel="nofollow">https:&#x2F;&#x2F;old.reddit.com&#x2F;r&#x2F;CrossView&#x2F;</a>

Every Asshole knows this trick for targeting spacecraft<a href="https:&#x2F;&#x2F;youtu.be&#x2F;XGdjKvivJA8?si=lRrfl6rHzAsE7nEO" rel="nofollow">https:&#x2F;&#x2F;youtu.be&#x2F;XGdjKvivJA8?si=lRrfl6rHzAsE7nEO</a>

Every 80’s kid knows this trick from those old books where you cross your eyes to reveal images.

I may originally have stumbled across this trick looking at repetitive patterns. I distinctly recall automobile upholstery (with a regular recurring ventilation pattern). In particular, abberations in the pattern (dirt, missed holes, etc.) stood out.Similarly, acoustic ceiling tiles, repeating patterns on wallpaper, rugs, or draperies, building faces, etc.This may be a superpower to some, or a supertorment to those with OCD ;-)

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&#x2F;at the same angle?””Is the wallpaper pattern aligned everywhere?””Is that surface using a repeating texture?”

This is called &#x27;vdiff&#x27; in the Jargon File: <a href="https:&#x2F;&#x2F;jargonfile.johnswitzerland.com&#x2F;vdiff.html" rel="nofollow">https:&#x2F;&#x2F;jargonfile.johnswitzerland.com&#x2F;vdiff.html</a>

I didn&#x27;t know this had a name or was considered a skill. I&#x27;ve done this since the 90&#x27;s when those magic eye books became popular.I even managed &quot;impossible mode&quot; in 2 or 3 seconds.

Try on mobile, it&#x27;s easier if the images are smaller.

Are you crossing your eyes (focusing nearer than the object) or diverging them (focusing past it)? Diverging is a harder skill to learn.

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.

It&#x27;s like<a href="https:&#x2F;&#x2F;triaxes.com&#x2F;docs&#x2F;3DTheory-en&#x2F;522ParallelCrosseyedviewingmetho.html" rel="nofollow">https:&#x2F;&#x2F;triaxes.com&#x2F;docs&#x2F;3DTheory-en&#x2F;522ParallelCrosseyedvie...</a>which some people struggle with, somebody posted a<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Autostereogram" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Autostereogram</a>to HN yesterday which some people get and others don&#x27;t. (That&#x27;s different from the &quot;cross-eyed stereogram&quot; because one of them involves having two images and the other one has one image with two images hidden in it)

I spent far too much time as a twenty-something generating autostereograms, which seems to have trained my eyes.  I was able to &quot;cross&quot; the images on this page very quickly.

Don’t CROSS them. Relax them, like you’re tired and can’t focus on a computer screen.

If you mean literally you can only bring them half way together, try just moving twice as far away.

Yeah, me either. My eyes really resist it. And after trying it a few times it messes up my focus for a bit.

Same! I feel like I can get a fleeting moment and then it&#x27;s gone. I swear I could cross my eyes when I was a kid - I wonder if with practice it&#x27;ll come back or if I&#x27;m just old and this skill I didn&#x27;t-know-I-wanted is lost

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&#x27;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&#x27;s fine.

Treat it like a &quot;Magic Eye&quot; photo and just relax your eyes to a further focus point.

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.

Here&#x27;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&#x27;ve got it, slowly zoom in a bit at a time, re-acquiring the overlap at each stage.

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&#x2F;cross my eyes and retain focus. 
With the reeducation I was able to see the Impossible one in focus after a couple tries.

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.

That was me at first.I think the &quot;cross eyed&quot; 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&#x27;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 &quot;gosh, this thing is a lot closer than it should be&quot; where &quot;should be&quot; is based on focal point, and &quot;is a lot closer&quot; is based on focus.Don&#x27;t want to do this too much, feels like I could easily decalibrate my brain for real life lol.

Works for me, I see 3 images if I try hard and the differences pop out

I have just figured that using kitchen towel rolls as a binoculars is the easiest way to do a parallel eye on these kind of images.Try that.Hold the rolls like binoculars where right roll is pointing at right image and left is at left image.It&#x27;s like a DIY VR headset where your brain&#x2F;eyes only gets two same looking things to focus. No outside noise.

I can&#x27;t overlap the images to save my life - they get like halfway there and that&#x27;s it...

One of my dad&#x27;s sayings when somebody in a film delivered a line and then disappeared was &quot;6 months rehearsal for that.&quot;

You may or may not be aware that Andy Warhol famously quipped that, &quot;in the future, everyone will be famous for 15 minutes,&quot; 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!

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 &quot;cool kid&quot; (but for, you know, the whole of society instead of just one&#x27;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&#x27;s really good in life - I&#x27;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, &quot;who?&quot; or &quot;I&#x27;ve heard the name, but know nothing about him.&quot; 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 once accidentally dropped a glass that was about half full of water and I somehow managed to catch it with the side of my foot without spilling any.Sadly no one saw this &#x27;feet&#x27;.

&gt;Probably my peak fame right there.My son and I always make jokes about everyone&#x27;s 5 minutes of fame. Some random person on the jumbotron at a sporting event &quot;Yup, there&#x27;s his moment, it&#x27;s over now.&quot;At least yours got you something ;)

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.

I was about to post this same exact post :)Was the high score holder on there for a few years.

Those Megatouch systems run Linux! Lots of fun messages to read on the credits screen or when you reboot them.

This is my peak fame as well. I had the high score on every one of these I&#x27;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 &#x27;Photo Hunt&#x27;

...except as you say, it didn&#x27;t work. The &quot;eye-cross&quot; trick gave the answer on the impossible one in ~10 seconds.

Took me about 10m total to get it all the way to impossible mode. I think you can do it!

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.

Same here. I can get the images to overlap; it feels like a stereoscopic image that lies a bit beyond the screen. But the differences don&#x27;t pop out to me. I have less trouble finding them looking normally.

Failed to perform the technique despite multiple retries, but didn&#x27;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.

Sadly I was never able to gain anything from this trick other than my kids admiration.  Often times kids menus at restaurants will have a spot the difference and I can see everything instantly doing this. Impressive to a kid but this girl in the video was obviously doing the same thing and does not impress me.

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 &quot;spot the differences&quot; 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.

I think it&#x27;s because our peripheral vision is able to observe movements faster.

That seems like not the same thing though, right? You&#x27;re not doing a diff on two images, you&#x27;re just losing resolution so you can direct more attention to movement.

I&#x27;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.

I first read about this back in the 1980s, in an issue of Science Digest. Couldn&#x27;t find a link or reference on short notice, but here&#x27;s something from the American Academy of Ophthalmology that explains the phenomenon, with an experiment to see the blood vessels in your eye:<a href="https:&#x2F;&#x2F;www.aao.org&#x2F;eye-health&#x2F;tips-prevention&#x2F;experiment-see-blood-vessels-in-your-eye" rel="nofollow">https:&#x2F;&#x2F;www.aao.org&#x2F;eye-health&#x2F;tips-prevention&#x2F;experiment-se...</a>Apparently, the brain tends to ignore visual stimuli that don&#x27;t change over a short period of time, which allows you see &quot;around&quot; 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.

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&#x27;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.

Weird timing. I dunno why this works but I&#x27;ve been using it to see mice.You see, I noticed that I have a mouse problem in my garage. I figure if I&#x27;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.

I feel old knowing <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Magic_Eye" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Magic_Eye</a>

You can also now free-view stereo image pairs. Congratulations.

This happens to me too. Particularly when it&#x27;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&#x27;s. It had some interesting graphics modes, including Red&#x2F;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&#x27;t get textures, only blobby shapes.

I don’t share a lot of comments from HN with my spouse, but this made me crack up so much that I just had to. Thanks for the story!

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.

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 egWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDWORDThen copy that and paste it a bunch of times to make it multi-line.Cross your eyes so that the WORD&#x27;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.

When auto stereograms were all the rage in the late 80&#x27;s I had a program on my Mac Plus that let me make&#x2F;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 &#x27;alternate&#x27; focus when viewing a repetitive pattern.

The problem I have with this is that instead of the images completely overlapping they overlap a section in the middle. I can&#x27;t get both images to completely overlap and am getting some eye strain from trying to force them.

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&#x2F;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] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vergence#Divergence" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vergence#Divergence</a>[2] <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vergence#Convergence" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Vergence#Convergence</a>

A simple trick to doing this, in case it&#x27;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.

By ready your comment, I just realised that this is what I’m doing instinctively, instead of crossing my eyes :o

To reduce eye strain, don’t cross your eyes, but relax them (so, the other way). Instantly clear and snaps together as if magnetic.

I&#x27;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. &quot;what&#x27;s the difference between these two functions&quot; or &quot;how is this yaml block different from that yaml block&quot;?)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.

Fun fact: it&#x27;s a different device, but the principle is the same as the device used in the documentary Tim&#x27;s Vermeer. It results in the images overlapping between your left and right eye and you simply paint until the difference goes away.

A blink comparator would be a much better GUI tool for comparing photos (for example original vs. post-processed) than the standard &quot;left half-right half&quot; with a movable divider. Alas, it’s rarely used (eg. Lightroom’s compare view doesn’t have one).

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 <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Blink_comparator" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Blink_comparator</a> instead, just switching between two images with zero flicker and zero displacement offset. Also with both eyes, it&#x27;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 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: <a href="https:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;NizzRgo" rel="nofollow">https:&#x2F;&#x2F;imgur.com&#x2F;a&#x2F;NizzRgo</a>

Incredible! This technique is also used for the 3d visualization of protein structures, it was called &quot;cross viewing&quot;: <a href="https:&#x2F;&#x2F;imgur.com&#x2F;cross-views-are-commonly-used-to-view-protein-structures-3d-UR69BKY" rel="nofollow">https:&#x2F;&#x2F;imgur.com&#x2F;cross-views-are-commonly-used-to-view-prot...</a>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&#x27;s a neat skill to have.

The funny thing about the stars image is this is a common way to find asteroids, comets. It&#x27;s not limited to just those. Only instead of a bunch of cross eyed astronomers, they overlay and align the images and do subtraction&#x2F;difference filtering to see what&#x27;s left. For comets&#x2F;asteroids, the dot of interest will move between frames. Even just playing back the aligned images as a timelapse can reveal motion.

The stars puzzle helped me find a speck of dirt on my phone screen.

Wow that&#x27;s interesting — trying to cross my eyes produces hellish jitter.I suspect it&#x27;s because my left eye is slighty lazy.But I was able to superimpose the right cat picture onto the left one (it&#x27;s a lot harder for the more complex sky resort picture). It&#x27;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&#x27;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.

Autostereogramming it doesn&#x27;t help me lolIf it&#x27;s perfect, the overlapping regions just merge in color, i.e. the cat&#x27;s paw becomes off-white. If it&#x27;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&#x27;s contributions to the merged view. Just not an attention-saver.

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&#x27;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&#x27;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.

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.

dang it i just did this on a zoom meeting. hopefully no one saw me trying to cross my eyes

This is how I help my family when they&#x27;re stuck on &quot;spot the difference&quot; 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.

No, a modification of this: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Stereoscope" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Stereoscope</a>

&gt; though generally a special device with mirrors was usedMaybe this: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Blink_comparator" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Blink_comparator</a>

I knew some people who used it to compare aerial photos (though generally a special device with mirrors was used).

I&#x27;ve done this on these game machines 30 years ago when I was 10. I&#x27;m baffled that there are still people who have to figure this out.

This is effectively how Pluto was discovered (not cross-eyed, but with a tool to help):
<a href="https:&#x2F;&#x2F;airandspace.si.edu&#x2F;stories&#x2F;editorial&#x2F;finding-pluto-blink-comparator" rel="nofollow">https:&#x2F;&#x2F;airandspace.si.edu&#x2F;stories&#x2F;editorial&#x2F;finding-pluto-b...</a>

I think the key is not &quot;going cross-eyed&quot; as much as it is relaxing your focus until the images merge. If you intentionally cross your eyes, it hurts. If you de-focus&#x2F;relax your eyes until the images merge, it doesn&#x27;t hurt.

All it did was hurt my eyes. I&#x27;ll opt out of playing, superpower be damned.

Front page of HN. Funny to imagine thousands of people sitting in the office crossing their eyes at their computer screen right now.

Uncross your eyes! :-)(They&#x27;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&#x27;re signing a contract with who sometimes lies to you and says they changed things when they didn&#x27;t

Oh wow you can also use this for contract diffing when signing in person!

I&#x27;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.

Yes, it had a split screen option where the two images were the same size and side by side. Can&#x27;t recall what kind of TV it was... perhaps a Sony?

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&#x27;ve seen only allowed moving where the insert was placed (which corner), but it was always a PiP and never a split screen.

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.

Hah, Kevin Smith caught some flak for that one:&quot;
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, &quot;Now, thanks to Blu-Ray, I get people pointing this out to me all the time!&quot;
&quot;<a href="https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;MovieDetails&#x2F;comments&#x2F;9lf52b&#x2F;in_the_movie_mallrats_the_magic_eye_poster_was&#x2F;" rel="nofollow">https:&#x2F;&#x2F;www.reddit.com&#x2F;r&#x2F;MovieDetails&#x2F;comments&#x2F;9lf52b&#x2F;in_the...</a>

all i managed to do was make myself very dizzy

Validates a claim in the predictive processing paradigm. The diff between actual and expected is what matters to error correction. That&#x27;s where all the relevant information is.

Learned this at a young age with the Highlights magazines at the dentist.

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 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

Hah, old trick, I read pull requests this way for years

I always feel like I&#x27;ll permanently see cross eyed if I keep doing that.  It doesn&#x27;t help that I was accidentally hit in the head by my double&#x27;s partner racket in tennis and spent like a minute or two walking around seeing double.  Not fun.

Try the second test image (the one labelled &quot;Hard&quot;, with the snow). That one was far easier for me than the first (the cat one).

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&#x27;t stick out at all :&#x2F;

Wow. That’s insane! With the trick I can somehow solve them all!

One thing I noticed: because you&#x27;re tricking your eyes into thinking they&#x27;re observing at a different distance, your brain doesn&#x27;t seem to correctly account for head tilt (my theory of the diagnosis). Anyway, I think you&#x27;re head must be exactly level with the image or you&#x27;ll get double-vision&#x2F;blur

It’s way trickier if you have astigmatism

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.

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).

Come on, I&#x27;ve been doing this since I was like 4 years old, this can&#x27;t be news for anyone, Am i right???

I can overlap. But still need to match overlap with anyone.anyway interesting

this made all the difference in the world.

Use your browser to zoom out and make the images slightly smaller

Any recommendations for when you can&#x27;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.

uh dunno.25y ago, i was working behind a 30&quot; 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&#x2F;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 :&#x2F;

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.

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!

ITT: everyone telling us their stories about how great they are at stereograms. We get it, you&#x27;re all super special.

This is a game mechanic in one of the trials in Ace Attorney Chronicles.

This is the coolest thing I have seen on here!!

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.

Peak HN.Stereogramming your colleagues eyes during boring meetings.HaEdit: 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.

If you&#x27;re distant enough &#x2F; the people are sitting close enough, you can stereogram two people&#x27;s faces together. You usually only get fleeting moments of crispness when their heads are aligned correctly though.

I wrote a paper about doing this using human eyes as the &quot;repeating pattern&quot; (either someone else&#x27;s, or your own in a mirror): <a href="https:&#x2F;&#x2F;philpapers.org&#x2F;archive&#x2F;ALEDSK.pdf" rel="nofollow">https:&#x2F;&#x2F;philpapers.org&#x2F;archive&#x2F;ALEDSK.pdf</a> ...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&#x27;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&#x27;s a seriously trippy effect.Another &quot;super power&quot; application similar to OP: the ability to confirm whether or not two distant digital clocks&#x27; seconds-digits are perfectly in sync. Since they&#x27;re distant, it takes time to shift one&#x27;s gaze from one to the other, making it hard to confirm whether they&#x27;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 &quot;third eye&quot; (and once you&#x27;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)

Wow I feel like I&#x27;ve never seen anyone talk about this. Doing it with fences can feel pretty magical, like the object is more &quot;real&quot; than other things.

Neat, the colors only blade when perfectly aligned.

Now try it with various colors, some people can see &quot;impossible&quot; colors [0].[0] <a href="https:&#x2F;&#x2F;preview.redd.it&#x2F;yaiyf2bi9aa31.png?width=640&amp;auto=webp&amp;s=81e8a8384e219ac95145ff512134cedef6f17234" rel="nofollow">https:&#x2F;&#x2F;preview.redd.it&#x2F;yaiyf2bi9aa31.png?width=640&amp;auto=web...</a>

I have never been able to see stereograms (I think because I have an eye which is far &quot;stronger&quot; than the other) and that movie made me feel seen.

Yep, this is exactly what came to mind with this &quot;newly unlocked superpower&quot;.I wonder if OP is aware they made a joke about the inability to use this superpower to identify a sailboat in a 90s indie movie.

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 &quot;inverted&quot; 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 &quot;spot the difference&quot; games since well it seemed kinda obvious to try, and I was blown away that it accidentally gave me that &quot;superpower&quot;. I think that was pretty smart for a 6yo. Has only gone downhill ever since. ;-)

I've acquired a new superpower