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Comment by JeremyHerrman | Hacker News Reader

Is it just me or are some of these examples not actually stereo image pairs?

I'm just crossing my eyes to see the "negative" depth image but some like "McLean’s House" and "Lincoln visits General McClellan at Antietam" don't appear to have any depth changes between them.

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You need to swap left and right images to use the cross-eyed method on these. You can try downloading as an image, use an app like Preview to Flip Horizontal (that will work).

Otherwise you're seeing a kind of inverse stereo image.

(EDIT: Having said that, I tried a few of the images and the stereo effect is subtle. The soldier on the horse — I was not even able to get that to "snap" for me. I am not great with cross-eyed stereo though.)

yes understood that cross-eyed method inverts the depth. My point was that some of the image pairs are from the exact same perspective - so there is no stereo depth no matter if you're using cow-eyed or cross-eyed.

Yeah, if there is depth, it was pretty subtle on the few I got to work.

Here are some videos trying to show what I mean. I overlapped the two images on top and crossfaded between the two. Aside from some minor distortion I don't see any major differences normally found between stereo pairs.

https://imgur.com/a/RMy3QA3

These images were prepared for insertion into a stereogram in which the left eye looks at the left image and right eye looks at the right image, through a magnifying lens. When viewing with the naked eye, you must stare past the images into the distance to get them to converge that way.

Thanks, I understand how stereograms work and have quite a few of these IRL. I use cross-eyed method to quickly view them (albeit inverted depth) when shown on screen.

I've tried to show my point in these videos which show basically no difference between the two images when overlapped and crossfaded between the two. https://imgur.com/a/RMy3QA3

I agree that particular image is a dud; I was not able to perceive any depth.

The creator mistakenly used the same image twice.

The two men in a tent image is likewise a dud. If we look at the pole at the tent entrance, there is no difference in parallax between that and objects at the back wall.

The Abe Lincoln doesn't pop out much for me.

The dead soldiers in the field also seems to be identical images.

The clearly genuine ones are the horse-drawn carriage in the forest, and the horseman in front of the cannon.

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