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.
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.
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.
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!
That imgur may need to be shrunk depending on your screen for parallel to work.
/s
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 this
1. Load file A into a tab
2. Load file B into a tab
3. Close all other tabs
4. Hold down the tab switch shortcut key and note the result
For images this is actually pretty decent and I'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's what they're there for.
For text: you'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've previously read a blog post, link to which I of course now can'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'd make a change that you weren't certain of, then press the key repeatedly to see before and after. No need to think. Thinking isn't appropriate here anyway. Just let your eyes look at what they're seeing.)
I can't uncross, now!
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.
Most people at least understand that stereographic vision has something to do with 3D perception because we've all closed 1 eye before.
My eyes get very watery after just a few seconds though, curious to hear from others how common this side-effect is.
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.
[0] https://i0.wp.com/www.magiceye.com/wp-content/uploads/2018/1...
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.
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 > _ <
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).
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.
Now, ask me to look at my code again for a couple minutes and it might be tough but it worked :)
I'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't overlap the images.
Focus in front of the screen is the easy one. How do you get beyond....
What's the beyond?
”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?”
I even managed "impossible mode" in 2 or 3 seconds.
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.
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.
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.
I used to not be able to do the "magic eye" 3d images until recently, and this trick is pretty handy.
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.
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)
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.)
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.
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)
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.
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.
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 is what worked for me. I used my laptop, zoomed in a bit on the images and brought the screen fairly close to my face. I ensured that the image was crisp using each eye (I also have astigmatism, and I probably also need reading glasses, but there is a sweet spot where both eyes have good focus, and I ensured I was there.) While crossing my eyes a bit, I start to see a third image in the center of the two images, but it's either out of focus (like two overlapping images), or it's very thin, like it's not the full image. I relax and keep my attention on this imperfect image and try to focus on it without trying too hard. Using this approach the image suddenly comes into focus and I no longer have to try to keep it there.
I feel like the key might be to notice the very beginning of the desired image in the center and then to try and focus on it, but in a bit of a relaxed way.
Incidentally when it works it is extremely weird! The other images essentially disappear and it's like you've travelled to another dimension.
I have otherwise good vision, I can read small text from farther than most people (I didn't realize not everyone could read all the small letters on an eye test), I don't have a problem seeing things up close either, etc. but I lack the ability to properly cross my eyes for some reason.
It's too bad because I've spent a decent amount of time at bars with those spot the difference machines lol
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.
For most people, having the images resolve in front of the plane of the page such that in resolved overlaid image the right eye sees the left image, and the left eye sees the right image, will work ... and it can work even if the images are farther apart than the interpupillary distance.
Are the eyes mechanically capable of pointing outward (so the interpupillary distance is not longer a constraint)? If so, is the problem then neurological not mechanical (brain doesn't want to send signal so they do that)?
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 ;)
The guy famously trained for months for the fight scene and a tired Harrison Ford just pulled out the gun and shot him. Everybody thought it was hilarious and that became the scene.
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.
> 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."
This may be something I'm making up, but I have the feeling that the fame = immortality concept came out of legacy: people wanting to create a family that continues on after themselves (and is rich, powerful, etc). Which makes sense, because then we're talking about a logical extension of the reproductive instinct. But in the modern world even that seems unreachable to me: we're so utterly different from our grandparents that we might as well be aliens, and the same will probably hold true for our own grandchildren.
I guess all that puts me in the Mike Tyson school of thought on legacy: "We're just dead. We're dust. We're absolutely nothing."
> we remember factoids... I might remember 7 things about Teddy Roosevelt... but those things do nothing to represent the complex individual he actually was.
I've thought this before when looking at Wikipedia pages. Especially for less famous people with thin pages, they'll cite just a handful of news articles or press releases in which the person appeared. If there were a page like that for me, or the people that I know best, the collection of factoids would be a laughably inaccurate reflection of who we really are. Someone told me that it's important to write an autobiography for this reason.
Was the high score holder on there for a few years.
The game is usually called 'Photo Hunt'
My usual method is just to brute-force linear scan from left to right, top-to-bottom. May not be elegant, but it works.
Makes you wonder if the kid he was talking about had a lazy eye or crossed eyes or something.
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.
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.
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.
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 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.
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.
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.
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.
Divergence only worked for me in the cat bear image. For the others, I could see a combined image but I could not see any differences highlighted, even though I knew what to look for.
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.
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.
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 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.
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.
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.
Maybe this: https://en.wikipedia.org/wiki/Blink_comparator
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
(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.)
" 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...
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 :/
But I never knew this technique could be used to spot the difference between images. Very cool discovery!
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)
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.
[0] https://preview.redd.it/yaiyf2bi9aa31.png?width=640&auto=web...
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.
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..
Similar to the finger moving closer and closer to the upper nose technique, for convergence.
I actually "practiced" a lot like this because I was always amused to notice how we could basically "see through" objects with this double-image thingy (see experiment below).
So I decided to film myself... and I was actually already doing a divergence! Not convergence!
Thanks a lot for your comment which made me realize that.
Experiment:
1. place your phone (handy size/shape for the experiment) in front of one eye (X), at about 20cm.
2. close the other eye (Y) and look at your phone
3. Open Y and look straight without focusing on the phone. By blinking Y, the double-image should appear/disappear, as if it was unveiling what's behind your phone.
4. By closing X and with Y open, looking at your phone, you should see it displaced from where it was when X was open and Y was closed. The size of this displacement is equal to the size of the double-image transparent part.
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.
So cool!
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.
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.
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.
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!"
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.
The cross eyed method seems more amenable to different image sizes. With my regular method, I can't merge images if they're too large (unless I step back).
