Stereograms and Salitsky Dots

[Kullervo]

Just a poll.

[CurtC]

My mom bought me the one of the B2 bomber 11 years ago, when those things were new, 'cause she figured I would like it. Since then, I have showed hundreds of people how to see it, and they all have been able to.

Trouble is, I can't see it myself. I've spent countless hours trying, and sometimes I can make out a shape in one small corner of the picture, but it doesn't last long, and I can never see more than one little piece at a time.

[mindless]

RE: curtc

sounds like your putting to much effort into seeing the picture, if your doing it correctly ther eis no effort required at all. I am pretty quick at seeing stereograms can focus in in about 10/20 seconds.

I have many friends that still can not see sterograms. What methods have you tried so far?

I have to go slightly cross eyed to see the pattern, you just have to find the right distance to stand away from the picture and then get your focus correct.

Unfortunatly its not something you can be told, you have to see it for yourself (hmmm, i'm going off on a bit of a matrix tangent here)

[Kullervo]

One method that works sometimes is to put the picture behind a piece of glass and use the reflection as a plane of reference for focusing.

Alternatively you might try and find some pornographic images for that additional motivation.

[arcticpenguin]

You're talking about the "magic eye' pictures? I can see them, but I think they're stupid. We work with better stereoimages in the lab all the time.

[Kullervo]

Can you post some of your lab images?

(Yeah, the Magic Eye images, but also things like the old stereopticon slides, which you can see in 3d without a viewer with some practice)

[davidhorman]

My brother-in-law's brother-in-law worked at a printer's who were one of the first to publish the posters, so that's how I got to see them, and I can see them straight away.

Eventually I wrote a program to make them and even got it published, and a whole page on my program in the magazine - this was back in the days when computer magazines had coverdiscs :) And that's pretty much my only clame to "fame" so far...

If you've seen Mallrats, one character spends most of the movie trying to "see" an autostereogram, only to be told by a kid that it's a yacht. Only it's not, it's some geometric shapes.

David

[Torlack]

If you have trouble seeing sterograms (if I am thinking of the right thing), you might have a slight case of strabismus (eye alignment problems). It is a LOT more common than people think. In my family, strabismus runs about 1 out of 5. But only one of us you can tell without an exam. For the world population, it is around 1 in 20.

Ultimately, if you have strabismus, the brain will just ignore the signals from one eye even though both eyes might be fully functional and used at different times.

[malaka]

There is a running gag in Mallrats (http://us.imdb.com/Title?0113749) about a kid (William Black) who can't see a "magic eye" picture.


Little Girl: [looking at a Magic Eye poster] Wow! It's a scooner!
William Black: Ha ha ha ha! You dumb bastard! It's not a scooner...it's a Sailboat!
Little Boy: A scooner IS a sailboat Stupid Head!
William Black: [becoming enraged] Well ya know what! There is NO Easter Bunny!! Over there? That's just a Guy in a Suit

[arcticpenguin]

Originally posted by whitefork
Can you post some of your lab images?

Here's one.

Let your eyes diverge (wall-eyed) to see the three dimension properly. If you are near-sighted, take off your glasses and bring the image close to your eyes.

This is probably about the best I can put up here, given the file size limits. We use color to clarify the image, not to obscure it like they do with magic eye.

[Cecil]

I can "uncross" my eyes at will, so I can see the pictures pretty much instantly. It's pretty cool. :cool:

[Kullervo]

Very nice one, AP. Thank you.

[toddjh]

I've never been able to see the stereograms the way I'm supposed to, although I haven't tried seriously. It's much easier for me to see the image by crossing my eyes to bring the images into alignment; it's effortless and takes maybe 5 seconds; the only problem is that you see the reverse of the image, with the item sticking out of the page instead of appearing recessed into it. Still, works fine for me. :)

Jeremy

[rwald]

I can view stereograms using the divergant method very easily; 5 seconds would be an unusually long time for me to get one ;). I can also do the cross-eyed method, but only when I put my finger in front of my face to help me. That takes more like 10 seconds.

Here's a more mathematical example of a 3D stereogram...

(Pictures outright stolen from KnotPlot (http://www.pims.math.ca/knotplot/), a great program for playing around with the topology of knots.)

http://www.pims.math.ca/knotplot/stereo/inlines/10.102L.gifhttp://www.pims.math.ca/knotplot/stereo/inlines/10.102R.gif

[Cecil]

Originally posted by toddjh
I've never been able to see the stereograms the way I'm supposed to, although I haven't tried seriously. It's much easier for me to see the image by crossing my eyes to bring the images into alignment; it's effortless and takes maybe 5 seconds; the only problem is that you see the reverse of the image, with the item sticking out of the page instead of appearing recessed into it. Still, works fine for me. :) That's the same thing as what I can do; it's also the "normal" way. The images are supposed to stick out from the page.

[rwald]

When I use the divergant method, the pictures stick out of the page...

Maybe we've been looking at different pictures.

[Cecil]

Originally posted by rwald
When I use the divergant method, the pictures stick out of the page...

Maybe we've been looking at different pictures.

Yeah, divergance = sticking out.

When I cross my eyes, they are recessed.

[rwald]

Actually, it depends on how the pictures are arranged. I'm going to repost my images from above, only now so that the cross-eyed method will work right, not the divergant method:

http://www.pims.math.ca/knotplot/stereo/inlines/10.102R.gifhttp://www.pims.math.ca/knotplot/stereo/inlines/10.102R.gif

See? Now, if you use the divergant method, it'll be recessed into the page. The only reason divergant often equals popping out is because most people can see divergant images better than cross-eyed ones, so they print them thusly.

Hmm, should I start a poll asking about divergant vs. cross-eyed?

Edit: I decided to post the poll. It's at http://www.randi.org/vbulletin/showthread.php?s=&threadid=13459

[RichardR]

I can see them easily. Just focus your eyes 10 to 12 inches behind the picture and the image pops out.

[jj]

I have less than great binocular vision (both eyes work fine, but i was nearsighted in one and farsighted in the other as a kid, and nobody noticed until I was in 5th grade).

And I can't see (*&(* in the dot plots. Sigh.

[davidhorman]

Hey rwald, your last post shows two identical images :)

Yeah, divergance = sticking out.

When I cross my eyes, they are recessed.

Don't think that's right...

When your eyes diverge, they are focusing on a point behind the physical image (poster, monitor, etc). The whole of the 3d image lies recesses behind the screen. Likewise, when you go cross-eyed, everything appears closer than the screen.

Now, what the images look like once they are there depends on the image. You could construct a cross-eye stereogram of a hole in the ground, and although it would be a hole, it would be entirely in front of the screen.

David

[BillyJoe]

Sorry, rwald, but the difference between the divergence and cross-eyed methods is far easier to see with articpenguin's picture.

[rwald]

Interesting note...

When you use the cross-eyed method, everything will appear smaller than if you use the divergant method. After all, in the cross-eyed method, your brain thinks the image is in front of the screen, so it will appear smaller than it actually is. With the divergant method, the brain thinks the image is farther away, so it makes it seem bigger.

Oh, and while you're right, david, about whether the image appears in front of the page or behind it, the rest of us were thinking about how the image was constructed (i.e., a picture of a hole vs. a picture of a mountain), not where the picture appeared.

[KillerX]

This site has explainations of why 3D pictures work. It has some things to try if you can't see them and some 3D pictures and optical illusions.
http://www.vision3d.com/
It also has a lot of general optical information.

[arcticpenguin]

Originally posted by davidhorman

When your eyes diverge, they are focusing on a point behind the physical image (poster, monitor, etc). The whole of the 3d image lies recesses behind the screen. Likewise, when you go cross-eyed, everything appears closer than the screen.

Now, what the images look like once they are there depends on the image. You could construct a cross-eye stereogram of a hole in the ground, and although it would be a hole, it would be entirely in front of the screen.

David
The knack to using stereodiagrams, which you should be able to improve with practice, is to decouple focus from angular divergence. If you are nearsighted like me, you can take off your lenses and hold the image up close to your eyes to ease divergence.

[Soapy Sam]

I recall using simple stereoscopes to examine aerial photo stero pairs in Geography classes long ago. We never had enough scopes to go around, so some in the class quickly learned to do without them. Constructing a simple stereoscope from a couple of cardboard tubes might help to get the feel of "how to do it."

Years later, I saw my first art stereogram - in the Smithsonian gift shop. There was a Japanese family staring at it in puzzlement. The teenaged daughter suddenly "got it", and jumped up and down in excited enthusiasm, desperately trying to explain the effect to her parents, who didn't get it at all. I saw it more or less straight away- (an aircraft, but I can't say what type) and grinned and made flying motions at her.
She was so pleased to share the effect with someone else that she gave me a big hug. Quite made my day.

[davidhorman]

The knack to using stereodiagrams, which you should be able to improve with practice, is to decouple focus from angular divergence.

That's one reason they don't make 3d movies any more, right? It gives people headaches.

I saw a 3d film recently at an IMAX theatre. To me, the experience of the immensity of the IMAX screen was completely lost, because with the glasses on it seemed to be about 4 times closer.

David

[xouper]

bump