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The additive RG color space can produce shades of black, red, green, and yellow.
The subtractive RG color space can produce shades of transparent (not white), red, green, and black.

The RG or red–green color space is a color space that uses only two primary colors: red and green. It was used on early color processes for films.[1][2]

It was used as a additive format, similar to the RGB color model but without a blue channel, on processes such as Kinemacolor,[3] Prizma, Technicolor I,[4][5][6][7] Raycol,[8] etc., producing shades of black, red, green and yellow. Alternatively, it was used as a subtractive format on Brewster Color I,[9][10][11][12] Kodachrome I,[13][14][15] Prizma II,[16] Technicolor II,[17][18][19] etc., producing shades of transparent, red, green and black.

By comparison with a full spectrum color space, its poor color reproduction made it undesirable. The system cannot create white naturally, and many colors are distorted. No color containing a blue component can be replicated accurately in the RG color space (thus, blue is said to be out of gamut).

A similar color space, called RGK adds a black channel.[20] Outside of a few low-cost high-volume applications, such as packaging and labelling, RG and RGK are no longer in use because devices providing larger gamuts such as RGB and CMYK are in widespread use.

Until recently, its primary use was in low-cost light-emitting diode displays in which red and green tended to be far more common than the still nascent blue LED technology, but full-color LEDs with blue have become more common in recent years.

ColorCode 3-D,[21][22] a anaglyph stereoscopic color scheme, uses the RG color space to simulate a broad spectrum of color in one eye, while the blue portion of the spectrum transmits a black-and-white (black-and-blue) image to the other eye to give depth perception.

See also


  1. ^ Corporation, Bonnier (February 13, 1923). "Popular Science". Bonnier Corporation – via Google Books.
  2. ^ Thomas, Elway (1923). "First Successful Color Movie". Popular Science (Feb 1923): 59.
  3. ^ "Kinemacolor".
  4. ^ Trenholm, Richard. "The first Technicolor film was a total disaster a century ago". CNET.
  5. ^ Cinematographic Multiplex Projection, &c. U.S. Patent No. 1,391,029, filed February 20, 1917.
  6. ^ "Moving Pictures in Color", The New York Times, February 22, 1917, p. 9.
  7. ^ "The first Technicolor film was a total disaster a century ago". CNET. September 9, 2017. Retrieved June 27, 2018.
  8. ^ "Raycol".
  9. ^ Cherchi Usai, Paolo (2000). Silent Cinema. British Film Institute. p. 35.
  10. ^ Nowotny, Robert Allen (January 1, 1983). The Way of All Flesh Tones: A History of Color Motion Picture Processes, 1895-1929. pp. 127–129. ISBN 9780824051099. Retrieved May 29, 2015.
  11. ^ "Patent 1,145,968 - Photographic Film" (PDF). United States Patent Office. July 13, 1915. Retrieved May 29, 2015.
  12. ^ "Brewster".
  13. ^ Capstaff, a former portrait photographer and physics and engineering student had already worked on colour photography before he joined C.K. Mees and other former Wratten and Wainright employees in their move to Rochester in 1912–1913 after Eastman had bought that company to persuade Mees to come and work for him.
  14. ^ "Complete National Film Registry Listing". Library of Congress. Library of Congress. Retrieved January 2, 2017.
  15. ^ "2012 National Film Registry Picks in A League of Their Own". Library of Congress. Retrieved 2020-05-13.
  16. ^ "Prizma II".
  17. ^ Trenholm, Richard. "The first Technicolor film was a total disaster a century ago". CNET. Retrieved October 14, 2019.
  18. ^ "The First Successful Color Movie", Popular Science, Feb. 1923, p. 59.
  19. ^ "Kalmus, Herbert. "Technicolor Adventures in Cinemaland", Journal of the Society of Motion Picture Engineers, December 1938"
  20. ^ "Application filed by Germann & Gsell Ag".
  21. ^ "Ogon - The company behind the ColorCode 3-D&#00AE; System".
  22. ^ "Announcements". 3D Week. 2009-10-11. Retrieved 2009-11-18. glasses that will work for Channel 4’s 3D week are the Amber and Blue ColourCode 3D glasses