Many computer-generated images claim to be in 3D, but despite the illusion of depth given by clever perspective (especially when the image is moving) they are still flat. They are not truly three- dimensional.
Real 3D images are much more exciting to look at! This is because they have an extra dimension, depth. The scene is no longer flat but extends away into the distance, as in real life. People viewing a true 3D image often say: “It’s just like being there!” If you have ever seen a 3D film at an IMAX cinema you will probably have said the same thing!
Stereoscopic (stereo for short) images are not confined to moving subjects, of course. Most are in the form of photographic prints or slides. These are just as rewarding to view.
How does 3D photography work?
It works by imitating what we see with our eyes. When we look at a scene, the left and right eyes see slightly different images, because they are separated laterally by about 65mm. The brain combines these two images and creates a 3D representation of the original scene in the mind.
Anyone can make a stereo picture with an ordinary camera. You simply take two pictures from two viewpoints, ideally about 65mm apart horizontally. The camera must be moved sideways, parallel to itself, and not twisted in any way. Also, nothing in the scene must move between the two exposures or there will be a discrepancy in part of the final 3D image.
If you mount the two images side-by-side and view them in such a way that the left eye sees only the left image and the right eye only the right image then the brain does the rest and you will observe a 3D reconstruction of the original subject.
Here is an example of a stereo image pair.
Some people can free-view such images (the same technique used for viewing the popular Magic Eye pictures) but it takes practice. You might find it easier to see the 3D effect by placing a strip of card (12 inches or more in length) vertically between the left and right images and viewing from above with one eye on each side of the card, as illustrated below.