Color Management by John T. Drew

Author:John T. Drew
Language: eng
Format: epub
Publisher: Some Kind of Garden Media
Published: 2016-04-07T04:00:00+00:00

Diagram 13 Stare at the green or red color for a minute or two, then look at the white squares. These will appear to have the afterimage of the two hues (green having red and red having green).

Opponent-process Theory

Ewald Hering’s opponent-process theory explains the function of the cones, rods, and optic nerves found around the fovea in the middle of the retina wall. No rods are located in the area of the fovea itself, but they become highly concentrated as we move outward to the perimeter of the retina. The mid-area of the retina, between the fovea and perimeter, has equal amounts of rods and cones. The receptor cells located in this area function differently from those found in the fovea or the perimeter of the retina wall, as explained by Hering’s theory. The receptor cells are grouped in pairs of three types: blue/yellow, green/red, and black/white. Each of the cells has a negative and a positive color sensor—blue, green, and black are negative, and yellow, red, and white positive. These colors do not contain any proportions of other colors and are therefore pure to the eye. The receptor cells do not have the capability of stimulating a response for both colors at once, except for black and white. Both the Young-Helmholtz and the opponent-process theories hold that white is created by the presence of a sensation and black by the absence of one; any type of gray would be created by a partial absence of light according to the Young-Helmholtz theory, and a combination of positive and negative responses according to the opponent-process theory.

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