Viewing stereo photographs

How does it work?

To experience the stereo effect each eye has to see its own picture (like in reality). To create a stereo photograph two shots are taken, one for each eye. There are special cameras with two lenses or lens-add-ons for SLR cameras to create a stereo image with only one shot. I only have a standard camera, so my shots were taken one after the other. Therefore I cannot take a stereo photo of a moving object. The two pictures focus on the same subject but are taken from a slightly different viewpoint. A difference of a few centimeters creates a natural "eye-like" effect. For bigger objects like cities or even mountains, several meters are necessary. The subject will look like a small scale model (it's like you having a head of a few meters in diameter).

Using the cross-eye technique no special glasses or any other equipment is needed to see the effect. The right eye has to see the left image and the left eye has to see the right image. You need two fully functional eyes. If you need glasses wear them.

Why is it so hard?

The eye automatically focusses on any object you look at (pay attention to). You cannot control the lenses focus by will hence you will need to trick your eyes (or brain) to seperate focussing from the spot of attention.

First step: Use the thumb


Sit straight in your chair and look right onto the stereogram pair. Place your thumb in front of the screen, about 10 cm away from your nose. Keep the picture in focus. You will see one set of pictures (in focus) and two thumbs (out of focus).

Second step: Align the pictures


Now concentrate on your thumb. You will feel the muscles in your eyes contract. The thumb comes into focus (sharpens) and the set of pictures will blur. Now you see one thumb (in focus) and two sets of pictures (blurred). Move your head until the two set of pictures merge into three pictures: The stereogram pair overlays and create a third picture in the middle.

Third step: Locking the stereogram


Once the pictures are properly aligned the eyes will be fooled into seeing an actual scene. Stay focussed on the thumb but concentrate on the picture. You will see a 3d-image emerge. Now you can try to fully focus on the screen to sharpen the 3d-image without changing the eye's position. After a few tries you won't need the thumb's help anymore and viewing 3d-images will be as comfortable and normal as viewing any image.



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