You can actually see 3D pictures without 3D glasses. This is called “free-viewing.” Here you can learn and experience it.
Unlike horses, human’s eyes are located side-by-side in the front of their heads. Thanks to this close side-by-side positioning, each eye takes a view of the same area from a slightly different angle. Although the two eyes have plenty in common, each eye picks up visual information the other doesn’t.
Both eyes capture their own view and the two separate images are sent on to the brain for processing. When the two images arrive simultaneously in the back of the brain, they are united into one picture by combining the two images by matching up the similarities and adding in the small differences. And those small differences between the two images add up to a big difference in the final picture! The combined image is more than the sum of its parts. It’s a three-dimensional stereo picture.
With stereo vision you see an object as solid in three spatial dimensions – width, height and depth – or x, y and z. It is the added perception of the depth dimension that makes stereo vision so rich and special.
How to view a 3D Stereogram
Normally, when we look at or read something on the computer monitor, we aim your eyes directly at the surface of the monitor, like this:
With the parallel viewing method (a.k.a. the divergence or Magic Eye method), the lines of sight of your eyes move outward toward parallel and meet in the distance at a point well beyond the image. When you parallel-view, the muscles inside your eye that control the focusing lens relax and lengthen.
Another 3D viewing methodis called cross-viewing or the cross-eyed method. You aim your eyes so that the lines of sight of your eyes cross right in front of the image. When you cross-view, the muscles inside your eye that control the focusing lens contract strongly and shorten. Just don’t try too hard!
If you’re not trained to look at stereograms, it might take you some time to be able to see 3D images quickly. But with time, you can master it. First time I’ve looked at a stereogram it took me like an hour to finally be able to focus the eyes correctly to see the 3D image.
Anyway, let’s start with the easier ones:
And here are the somewhat trickier ones that take a bit more gazing: