# How are these 3d images made?

Just recently, Yahoo.com posted images that have a 3d effect without any glaesses and here is an example of one of them:

How is this done? I searched all over but can't find any good tutorial. I know it has something to do with distorting an image a certain way.

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While technically this isn't a "3D" photo, it does simulate a three-dimensional look by exploiting parallax displacement. Cameras are what we call "monocular" devices, in that they have a single lens system and single sensing device. As such, they are not parallax devices, and cannot sense depth directly...only indirectly via other effects such as depth of field. The human eye is "binocular", in that there are two lenses and two sensing devices offset from each other along a single plane. This gives us the ability to detect depth for the very same reason the image in your question has a pseudo-3D appearance.

The sample image simulates a binocular device, or perhaps even used a binocular camera setup, to achieve a modicum of depth perception and provide the photographer with the ability to simulate 3D. You could achieve the same effect with a camera on a tripod, and the use of a macro focusing rail set up parallel to the scene would probably make the job a bit easier. Set up the camera on the tripod, and point it at a scene that has a variety of objects at varying depths. If you shoot a scene with most objects far, and no objects near, you won't really see any kind of "3D" effect if you created a 2-frame GIF like the sample you posted. Set the camera to manual, configure your exposure, and take a photograph. Now, shift the camera to the left or right a small amount...say maybe 5-6 inches (you might need to experiment to find an ideal amount of shift to perfect the effect). Using the exact same exposure settings, take another photograph. These two photographs should essentially be the same, with only a slight shift parallel to the scene.

Near objects will appear more shifted in the second photograph relative to the first than far objects. This is parallax motion, and demonstrates a facet of perspective. You will need to fine tune the images, crop them identically, and scale them down a ways (probably to the size of the sample image you posted). In a tool like photoshop, you can create a two-layer, two-frame GIF image using the animation panel. Show only the first layer for 1/2 a second, then show only the second layer for another 1/2 of a second. Play back the animation, and you should see something similar to the flying alligator and that poor little girl.

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Is it the same as if you hold your finger up in front of your face, close your left eye and then close the right eye while opening the left and keep alternating opening and closing of each? – Rob Apr 29 '12 at 8:58
It's not a flying alligator. It's a jumping alligator. Poor alligator was quiet on its own, when all of a sudden a BABY, and what's more a baby with a pink hat, strolled by. It was so scarying that he jumped away, screaming to alert every other alligator of the terrible danger. – Francesco Apr 29 '12 at 11:53
@Francesco: Jumping would be the act that set the alligator a-flying. ;) Poor, poor little girl in pink. She is probably 90% scared to death! :o – jrista Apr 29 '12 at 15:44

To add to jrista's excellent answer, this technique is commonly known as "Wiggle 3D" or "Wiggle Anaglyph", so google for that to come up with more information and examples.

Adorama has a tutorial on how to make them.

Also, there are several 3D camera apps for iOS and Android that make these.

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 What should I search for to find an app like this for iOS? – dpollitt Apr 29 '12 at 21:24 @dpollitt: your search should include "3d" and "wiggle". I didn't do a search on an iOS device, but on Google I've got "ShowMe3D", "3D Camera Studio" and "iCam3Ra Lite" among top results when searching for "3D camera wiggle iOS". – Miguel Apr 30 '12 at 0:00