Opponent colors based on experiment. Protanopes will see little difference between the top and bottom colors in the central column.

The opponent process is a color theory that states that the human visual system interprets information about color by processing signals from cones in an antagonistic manner. The three types of cones have some overlap in the wavelengths of light to which they respond, so it is more efficient for the visual system to record differences between the responses of cones, rather than each type of cone's individual respone. The opponent color theory suggests that there are three opponent channels: red versus green, blue versus yellow, and black versus white (the latter type is achromatic and detects light-dark variation, or luminance). Responses to one color of an opponent channel are antagonistic to those to the other color. Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ... The visual system is what allows us to see. ... Color is an important part of the visual arts. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina of the eye which only function in relatively bright light. ... The wavelength is the distance between repeating units of a wave pattern. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye (visible light) or, in a technical or scientific setting, electromagnetic radiation of any wavelength. ... Red is a color at the lowest frequencies of light discernible by the human eye. ... Look up green in Wiktionary, the free dictionary. ... For other uses, see Blue (disambiguation) Blue is one of the three primary additive colors; blue light has the shortest wavelength range (about 420–490 nanometers) of the three additive primary colors. ... Yellow is a color with a wavelength 565-590 nanometers. ... Black is a color with several subtle differences in meaning. ... White is a color (more accurately it contains all the colors of the visible spectrum and is sometimes described as an achromatic color—black is the absence of color) that has high brightness but zero hue. ... Chromatic aberration is caused by the dispersion of the lens material, the variation of its refractive index n with the wavelength of light. ... The word luminance, a synonym for luminosity, means emitting or reflecting light. ...

Athough, according to the trichromatic theory, the retina of the eye allows the visual system to detect color with three types of cones, the opponent process theory accounts for mechanisms that receive and process information from cones. Though the trichromatic and opponent processes theories were initially thought to be at odds, it later came to be understood that the mechanisms responsible for the opponent process receive signals from the three types of cones and process them at a more complex level (Kandel et al., 2000). Human eye cross-sectional view. ... This article needs to be cleaned up to conform to a higher standard of quality. ...

The three types of cones, S, M, and L, respond best to short-, medium- and long-wavelength light respectively. Information from the cones is passed to bipolar cells in the retina, which may be the cells in the opponent process that transform the information from cones. The information is then passed to ganglion cells, of which there are two major classes: magnocellular, or large-cell, and parvocellular or small-cell layers (Kandel et al., 2000). Parvocellular cells, or P cells, are the major cells to handle information about color. They fall into two groups, one that processes information about differences between firing of L and M cones, and one that processes differences between S cones and a combined signal from both L and M cones (Kandel et al., 2000). These two subtypes are responisble for processing red-green and blue-yellow differences respectively. Cells in the parvocellular pathway transmit information not only about color, but also about intensity of light (how much of it there is) because of their receptive fields. As a part of the retina, the bipolar cell exists between photoreceptors (rod cells and cone cells) and ganglion cells. ... A ganglion cell (or sometimes called a gangliocyte) is a type of neuron located in the retina that receives visual information from photoreceptors via various intermediate cells such as bipolar cells, amacrine cells, and horizontal cells. ... Cells in culture, stained for keratin (red) and DNA (green) The cell is the structural and functional unit of all living organisms, and are sometimes called the building blocks of life. ... Receptive fields are areas of the retina, producing a change in the firing of cells in the visual system. ...

History

The opponent color theory was first proposed by Ewald Hering in 1872 (Hering, 1964). He thought that the colors red, yellow, green, and blue are special in that any other color can be described as a mix of them, and that they exist in opposite pairs. That is, either red or green is perceived and never greenish-red. (Note that although yellow is a mixture of red and green in the RGB color theory, the eye does not perceive it as such.) Ewald Hering (August 5, 1834 - January 26, 1918) was a German physiologist who did much research into color and spatial perception. ... 1872 was a leap year starting on Monday (see link for calendar). ...

In 1957 Leo Hurvich and Dorothea Jameson provided quantitative data for Hering's color opponency theory (Hurvich et al., 1957). 1957 (MCMLVII) was a common year starting on Tuesday of the Gregorian calendar. ...

The opponent color theory can be applied to computer vision and implemented as the Gaussian color model (Geusebroek et al., 2001). Computer vision is the study of methods which allow computers to understand images, or multidimensional data in general. ...

See also

• Color vision

Color vision is the capacity of an organism or machine to distinguish objects based on the wavelength of the light they reflect or emit. ...

References

• Geusebroek J. M., van den Boomgaard R., Smeulders A. W. M., Geerts H., Color invariance, IEEE Trans. Pattern Anal. Machine Intell., 2001; 23(12):1338-1350.
• Hering E., Outlines of a Theory of the Light Sense, Cambridge, Mass., Harvard Univ. Press, 1964.
• Hurvich LM, Jameson D, An opponent-process theory of color vision, Psychol Rev 1957; 64:384-404.
• Kandel E.R., Schwartz, J.H., Jessell, T.M., Principles of Neural Science, 4th ed., pp.577-580. McGraw-Hill, New York (2000).