Additive color oradditive mixing is a property of acolor model that predicts the appearance ofcolors made by coincident componentlights, i.e. the perceived color can be predicted by summing the numeric representations of the component colors.[1] Modern formulations ofGrassmann's laws[2] describe the additivity in the color perception of light mixtures in terms of algebraic equations. Additive color predicts perception and not any sort of change in the photons of light themselves. These predictions are only applicable in the limited scope of color matching experiments where viewers match small patches of uniform color isolated against a gray or black background.
Additive color models are applied in the design and testing of electronic displays that are used to render realistic images containing diverse sets of color usingphosphors that emit light of a limited set ofprimary colors. Examination with a sufficiently powerful magnifying lens will reveal that each pixel inCRT,LCD, and most other types of color video displays is composed of red, green, and blue light-emitting phosphors which appear as a variety of single colors when viewed from a normal distance.
Additive color, alone, does not predict the appearance of mixtures of printed color inks, dye layers in colorphotographs onfilm, or paint mixtures. Instead,subtractive color is used to model the appearance ofpigments ordyes, such as those inpaints andinks.
The combination of two of the common three additiveprimary colors in equal proportions produces an additivesecondary color—cyan,magenta oryellow. Additive color is also used to predict colors from overlapping projected colored lights often used in theatrical lighting for plays, concerts, circus shows, and night clubs.[3]
The fullgamut of color available in any additive color system is defined by all the possible combinations of all the possibleluminosities of each primary color in that system. Inchromaticity space, a gamut is a planeconvex polygon with corners at the primaries. For three primaries, it is atriangle.
Systems of additive color are motivated by theYoung–Helmholtz theory oftrichromatic color vision, which was articulated around 1850 byHermann von Helmholtz, based on earlier work byThomas Young. For his experimental work on the subject,James Clerk Maxwell is sometimes credited as being the father of additive color.[4] He had the photographerThomas Sutton photograph a tartan ribbon on black-and-white film three times, first with a red, then green, then blue color filter over the lens. The three black-and-white images were developed and then projected onto a screen with three different projectors, each equipped with the corresponding red, green, or blue color filter used to take its image. When brought into alignment, the three images (a black-and-red image, a black-and-green image and a black-and-blue image) formed a full-color image, thus demonstrating the principles of additive color.[5]
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