RG color models#Subtractive RGK

The additive RG color model uses red and green primaries. It was used in several processes during the early innovations of color photography, including Kinemacolor,{{Cite web|url=https://filmcolors.org:443/timeline-entry/1214/?_sf_s=Prizma+I&post_types=timeline_entry|title=Kinemacolor}} Prizma, Technicolor I,{{Cite web |last=Trenholm |first=Richard |title=The first Technicolor film was a total disaster a century ago |url=https://www.cnet.com/news/technicolor-100-years-the-gulf-between/ |website=CNET}}[https://patents.google.com/patent/US1391029 Cinematographic Multiplex Projection, &c]. U.S. Patent No. 1,391,029, filed February 20, 1917."Moving Pictures in Color", The New York Times, February 22, 1917, p. 9.{{Cite news |date=September 9, 2017 |title=The first Technicolor film was a total disaster a century ago |language=en |work=CNET |url=https://www.cnet.com/news/technicolor-100-years-the-gulf-between/ |access-date=June 27, 2018}} and Raycol.{{Cite web|url=https://filmcolors.org:443/timeline-entry/1244/?_sf_s=raycol&post_types=timeline_entry|title=Raycol}}

File:Redgreen.png

The primaries are added together in varying proportions to reproduce a linear gamut of colors, which can reproduce only a fraction of the colors possible with a trichromatic color space.

The appearance of the color gamut changes depending on the primary colors chosen. When the primaries are complementary colors (e.g. red and cyan), then an equal mixture of the primaries will yield a neutral color (gray or white). However, since red and green are not complementary colors, an equal mixture of these primaries will yield yellow, and a neutral color cannot be reproduced by the color space.

Until recently, its primary use was in low-cost LED displays in which red and green LEDs were more common and cheaper than the still nascent blue LED technology. However, this preference no longer applies to modern devices.{{cn|date=November 2022}} In modern applications, the red and green primaries are equal to the primaries used in typical RGB color spaces. In this case, the RG color model can be achieved by disabling the blue light source.

{{Multiple image

| image1 = Venn diagram for additive RG color.svg

| caption1 = The additive RG color model showing the primary colors. Overlap area is an equal mixture thereof (yellow), not white.

| image2 = RG 16bits palette sample image.png

| caption2 = Additive RG (modern example image).

| image3 = G. A. Smith, Two Clowns.jpg

| caption3 = Additive RG Kinemacolor frame from Two Clowns (c.1907).

| image4 = Ktype-variable-message-sign.jpg

| caption4 = Red and green LED traffic sign.

| align = center

}}

The subtractive RG color model uses red and green filters for film exposure, but complementary cyan-green (for red) and orange-red (for green) for the developed prints. This allows the generation of white, although the color model cannot achieve black, regardless of the primaries chosen. It was used in several processes during the early innovations of color photography, including on Brewster Color I,{{Cite book |last=Cherchi Usai |first=Paolo |title=Silent Cinema |publisher=British Film Institute |year=2000 |page=35}}{{cite book |last=Nowotny |first=Robert Allen |url=https://books.google.com/books?id=NrYaytLfSJYC&pg=PA127 |title=The Way of All Flesh Tones: A History of Color Motion Picture Processes, 1895-1929 |date=January 1, 1983 |isbn=9780824051099 |pages=127–129 |accessdate=May 29, 2015 }}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}{{cite web |date=July 13, 1915 |title=Patent 1,145,968 - Photographic Film |url=http://zauberklang.ch/filmcolors/wp-content/uploads/2013/11/Brewster_Brewster_US000001145968A.pdf |accessdate=May 29, 2015 |publisher=United States Patent Office}}{{Cite web|url=https://filmcolors.org:443/timeline-entry/1229/?_sf_s=Prizma+I&post_types=timeline_entry|title=Brewster}} Kodachrome I,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.{{cite web |author= |title=Complete National Film Registry Listing |url=https://www.loc.gov/programs/national-film-preservation-board/film-registry/complete-national-film-registry-listing/ |access-date=January 2, 2017 |website=Library of Congress }}{{Cite web |title=2012 National Film Registry Picks in A League of Their Own |url=https://www.loc.gov/item/prn-12-226/cinematic-firsts-enshrined-in-2012-film-registry/2012-12-19/ |access-date=2020-05-13 |website=Library of Congress}} Prizma II,{{Cite web|url=https://filmcolors.org:443/timeline-entry/1235/?_sf_s=Prizma+I&post_types=timeline_entry|title=Prizma II}} and Technicolor II.{{Cite web |last=Trenholm |first=Richard |title=The first Technicolor film was a total disaster a century ago |url=https://www.cnet.com/news/technicolor-100-years-the-gulf-between/ |access-date=October 14, 2019 |website=CNET |language=en}}"[https://books.google.com/books?id=XSoDAAAAMBAJ&pg=PA59 The First Successful Color Movie]", Popular Science, Feb. 1923, p. 59."[http://www.widescreenmuseum.com/oldcolor/kalmus.htm Kalmus, Herbert. "Technicolor Adventures in Cinemaland", Journal of the Society of Motion Picture Engineers, December 1938]"

{{Multiple image

| image1 = Venn diagram for subtractive RG color.png

| caption1 = The subtractive RG color model showing the primary colors. Overlap area is dark brown, not true black.

| image2 = RG 16bits subtractive.png

| caption2 = Subtractive RG (modern example image).

| image3 = Anna May Wong holds child in The Toll of the Sea.jpg

| caption3 = Subtractive RG Technicolor II frame from The Toll of the Sea (1922)

| align = center

| height = 150px

}}

File:Venn diagram for subtractive RG color.svg

A similar color model, called RGK adds a black channel, which allows for the reproduction of black and other dark shades.{{Cite web |title=Application filed by Germann & Gsell Ag |url=https://patents.google.com/patent/CH670713A5/en}} However, it does not allow the reproduction of neutral colors (gray/white) because the primaries are not complementary.

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 CMYK are in widespread use.

{{Main|Anaglyph 3D}}

In 1858, in France, {{Interlanguage link|Joseph D'Almeida|fr|Joseph-Charles d'Almeida|vertical-align=sup}} delivered a report to l'Académie des sciences describing how to project three-dimensional magic lantern slide shows using red and green filters to an audience wearing red and green goggles.{{cite news |last1=D'Almeida |first1=Joseph Charles |year=1858 |title=Nouvel appareil stéréoscopique |language=fr |trans-title=A New Stereoscopic Device |page=61 |website=Gallica |type=Lecture |format=image |url=https://gallica.bnf.fr/ark:/12148/bpt6k3004t/f61.image}} Subsequently he was chronicled as being responsible for the first realisation of 3D images using anaglyphs.{{cite news |last1=Picard |first1=Emile |date=December 14, 1931 |title=La Vie et L'œuvre de Gabriel Lippmann (membre de la section de physique générale) |language=fr |trans-title=The Life and Work of Gabriel Lippmann |page=3 |website=academie-sciences.fr |publisher=Institut de France. Académie des Sciences |type=Public Lecture |url=http://www.academie-sciences.fr/pdf/dossiers/Picard/Picard_pdf/Picard_Lippmann.pdf}}

{{Multiple image

| image1 = 3D-glasses.png

| caption1 = Red-green anaglyph glasses

| image2 = Red Green anaglyph picture.jpg

| caption2 = Red/Green anaglyph picture

| image3 = Scorpius 3D red-green.png

| caption3 = Constellation of Scorpius in 3D anaglyph for red-green glasses. The perception of depth depends on how the image is scaled.

| align = center

| height = 150px

| image5 = 3D HRSC image, Martian equator ESA221925.jpg

| caption5 = 3D image taken by ESA's Mars Express orbiter. The location is on the Martian equator north of Valles Marineris between 1° South to 2.5° North and 323° East. The area is 50 km across and shows mesas and cliffs as well as flow features indicating erosion by the action of flowing water. In this landscape view North is on the right. The 3D effect is only seen with the use of red/green 3D glasses.

}}

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• List of monochrome and RGB color formats
• List of motion picture film formats
• List of color film systems
• rg chromaticity
• Anaglyphic color channels

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{{reflist}}

• [https://web.archive.org/web/20040611010855/http://www.iscc.org/aic2001/abstracts/poster/Zoch.doc Even Proportional Color Triangle]
• [https://patents.google.com/patent/US1391029 Cinematographic Multiplex Projection, &c]. U.S. Patent No. 1,391,029, filed Feb. 20, 1917.
• "Moving Pictures in Color", The New York Times, February 22, 1917, p. 9.
• [https://books.google.com/books?id=XSoDAAAAMBAJ&pg=PA59 The First Successful Color Movie]", Popular Science, Feb. 1923, p. 59.
• [http://filmmakeriq.com/lessons/the-history-and-science-of-color-film-from-isaac-newton-to-the-coen-brothers/ filmmakeriq.com, The History and Science of Color Film: From Isaac Newton to the Coen Brothers]

{{Color space|state=collapsed}}

Category:Color space