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File:RGB illumination.jpg

Additive color mixing: adding red to green yields yellow; adding yellow to blue yields white.

An additive color model involves light emitted directly from a source or illuminant of some sort. The additive reproduction process usually uses red, green and blue light to produce the other colors. See also RGB color model. Combining one of these additive primary colors with another in equal amounts produces the additive secondary colors cyan, magenta, and yellow. Combining all three primary lights (colors) in equal intensities produces white. Varying the luminosity of each light (color) eventually reveals the full gamut of those three lights (colors). Computer monitors and televisions are the most common application of additive color.

Results obtained when mixing additive colors are often counterintuitive for people accustomed to the more everyday subtractive color system of pigments, dyes, inks and other substances which present color to the eye by reflection rather than emission. For example, in subtractive color systems green is a combination of yellow and blue, in additive color, red + green = yellow and no simple combination will yield green. It should be noted that additive color is a result of the way the eye detects color, and is not a property of light. There is a vast difference between yellow light, with a wavelength of approximately 580 nm, and a mixture of red and green light. However, both stimulate our eyes in a similar manner, so we do not detect that difference. (see eye (cytology), color vision.)

File:Tartan Ribbon.jpg

The first permanent color photograph, taken by James Clerk Maxwell in 1861.

File:J C Maxwell with top.jpg

James Clerk Maxwell with his color top that he used for investigation of color vision and additive color

James Clerk Maxwell is credited as being the father of additive color.[1] He had the photographer Thomas Sutton photograph a tartan ribbon three times, first with a red, then green, then blue color filter over the lens. The three 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 register, the three images formed a full color image, thus demonstrating the principles of additive color.[2]

See also


  1. James Clerk Maxwell. Inventor's Hall of Fame, Rochester Institute of Technology Center for Imaging Science.
  2. Robert Hirsch (2004). Exploring Colour Photography: A Complete Guide, Laurence King Publishing.

External links