How the Stereoscopic Phenomena is Produced

When you look at an object with both eyes, two objects are actually seen; one with the right eye and one with the left. Each of these images, because it is viewed from a slightly different angle, is a little different from the other. To demonstrate, take a standard hexagonal lead pencil and hold it vertically about six inches directly in front of the nose.

When you close the left eye and look at the pencil with only the right eye, you appear to have moved over to the right of the pencil. You are looking at the pencil from an angle and the left side of the hexagonal pencil disappears from view. When you close the right eye and look at the pencil with only the left, you seem suddenly to jump to the other side of the pencil. Now, you are looking at it from another angle and the hexagonal plane on the right side of the pencil disappears or is foreshortened.

When both eyes are used to view the pencil, the two separate images are blended into one. The perception of relief, depth or third dimension results.

The same effect is gained in stereoscopic photography by taking two separate, simultaneous pictures with lenses spaced approximately the same distance apart as one’s eyes.

Blending the picture is accomplished by the use of an instrument called the stereoscope. This device allows the right eye to view only the image photographed through one lens of the stereo camera. The left eye sees only the similar image taken by the other lens. The two images are carried to the brain where they are automatically blended into one with the same resulting perception of relief, depth or third dimension.