Parallax

:This article is about parallax, the perspective shift. For the DC comic book character see Parallax (comics).

Parallax of the human eye

Parallax allows humans and other animals, such as cats, to see depth and perspective.

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Binocular parallax

Binocular parallax is a binocular clue to depth perception, especially of near objects. Each eye views an object from a slightly different position, so the image seen by each is slightly different; fusion of the two images in the brain creates perception of depth. http://www.eyeglossary.net/

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If a person alternates between covering one eye and the other while fixating in the distance with a nearby object in front of them, the nearby object will appear to "jump" horizontally.

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Parallax is used in simple stereo viewing devices, such as the View-Master used to view stereoscopic scenery in the form of two images taken from adjacent locations. The Apollo astronauts on the Moon knew how to take such stereo pairs, clicking two frames of the same object in locations shifted slightly horizontally with respect to each other.

Related Topics:
View-Master - Stereoscopic - Apollo - Moon

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A way to allow a crowd of people simultaneously to view a stereoscopic scene is to provide them with anaglyph glasses. One glass is red, the other green or blue, and the stereo scene is produced by the printing process in a corresponding fashion. It is generally believed that such scenes are of necessity monochrome — red for the left image, green/blue for the right — but this is not quite true: working colour anaglyphic scenes have been produced http://axon.physik.uni-bremen.de/research/stereo/color_anaglyph/.

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Instructions for self-producing anaglyphic glasses by copying colour onto an overhead projector sheet can be easily obtained. Better quality glasses can also be purchased inexpensively from many science shops or internet mail orders.

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Autostereograms exploit the effect of parallax to allow viewers to see 3D shapes in a single 2D image.

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Monocular parallax

Monocular parallax is an important monocular clue to depth perception. As the head or the eye is moved from side to side, distance objects appear to move more slowly than do closer objects. http://www.eyeglossary.net/

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