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RGB color spaces
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{{short description|Any additive color space based on the RGB color model}} {{more citations needed|date=December 2014}} [[File:CIE1931xy_gamut_comparison.svg |thumb|300px|1931 CIE chromaticity diagram showing some RGB color spaces as defined by their chromaticity triangles]] '''<abbr title="red–green–blue">RGB</abbr> color spaces''' are a category of [[Additive color|additive]] colorimetric [[color space]]s<ref>{{cite web |title=colorimetric colour space (definition) |url=https://cie.co.at/eilvterm/17-23-042 |location=France |publisher= International Commission on Illumination (CIE)|access-date=8 October 2023}}</ref> specifying part of its absolute color space definition using the [[RGB color model]].<ref>{{cite web|author=Pascale, Danny|url=http://www.babelcolor.com/download/A%20review%20of%20RGB%20color%20spaces.pdf|title=A Review of RGB color spaces...from xyY to R'G'B'|access-date=20 October 2021}}</ref> RGB color spaces are commonly found describing the mapping of the RGB color model to human perceivable color, but some RGB color spaces use imaginary (non-real-world) primaries and thus can not be displayed directly. Like any color space, while the specifications in this category use the RGB color model to describe their space, it is not mandatory to use that model to signal pixel color values. Broadcast TV color spaces like NTSC, PAL, Rec. 709, Rec. 2020 additionally describe a translation from RGB to YCbCr and that is how they are usually signalled for transmission, but an image can be stored as either RGB or YCbCr. This demonstrates using the singular term "RGB color space" can be misleading, since a chosen color space or signalled colour can be described by any appropriate color model. However the singular can be seen in specifications where storage signalled as RGB is its intended use. ==Definition== [[File:RGB Cube Show lowgamma cutout b.png|thumb|300px|RGB cube]] The normal human eye contains three types of color-sensitive [[cone cell]]s. Each cell is responsive to light of either long, medium, or short wavelengths, which we generally categorize as red, green, and blue. Taken together, the responses of these cone cells are called the [[CIE 1931 color space#Tristimulus values|Tristimulus values]], and the combination of their responses is processed into the psychological effect of color vision. RGB use in color space definitions employ primaries (and often a white point) based on the RGB color model, to map to real world color. Applying [[Grassmann's laws (color science)|Grassmann's law]] of light additivity, the range of colors that can be produced are those enclosed within the triangle on the chromaticity diagram defined using the primaries as [[Vertex (geometry)|vertices]].<ref>{{cite book|last=Hunt|first=R. W. G|title=The Reproduction of Colour (6th ed.)|year=2004|publisher=Chichester UK: Wiley–IS&T Series in Imaging Science and Technology|isbn=0-470-02425-9|url-access=registration|url=https://archive.org/details/reproductionofco0000hunt}}</ref> The primary colors are usually mapped to [[xyY]] chromaticity coordinates, though the '''uʹ,vʹ''' coordinates from the UCS chromaticity diagram may be used. Both xyY and uʹ,vʹ are derived from the [[CIE 1931 color space]], a device independent space also known as '''XYZ''' which covers the full [[gamut]] of human-perceptible colors visible to the [[CIE 1931 color space#CIE standard observer|CIE 2° standard observer]]. ==Applications== {{See also|List of color spaces and their uses|label 1 = List of Color Spaces}} [[Image:1Mcolors.png|thumbnail|100px|left|One million colors in RGB space, visible in full-size image]] <!-- There should probably be a mention of the CIE 1931 RGB space here, with an explanation of its use. --> RGB color spaces are well-suited to describing the electronic display of color, such as [[computer monitors]] and [[color television]]. These devices often reproduce colours using an array of red, green, and blue phosphors agitated by a [[cathode-ray tube]] (CRT), or an array of red, green, and blue [[LCD]]s lit by a backlight, and are therefore naturally described by an additive color model with RGB primaries. Early examples of RGB color spaces came with the adoption of the [[NTSC]] color television standard in 1953 across North America, followed by [[PAL]] and [[SECAM]] covering the rest of the world. These early RGB spaces were defined in part by the phosphor used by CRTs in use at the time, and the gamma of the electron beam. While these color spaces reproduced the intended colors using additive red, green, and blue primaries, the broadcast signal itself was encoded from RGB components to a composite signal such as [[YIQ]], and decoded back by the receiver into RGB signals for display. [[HDTV]] uses the [[BT.709]] color space, later repurposed for computer monitors as [[sRGB color space|sRGB]]. Both use the same color primaries and white point, but different transfer functions, as HDTV is intended for a dark living room while sRGB is intended for a brighter office environment.{{citation needed|date=January 2023}} The gamut of these spaces is limited, covering only 35.9% of the CIE 1931 gamut.<ref>{{cite web |last1=Yamashita |first1=Takayuki |last2=Nishida |first2=Yukihiro |last3=Emoto |first3=Masaki |last4=Ohmura |first4=Kohei |last5=Masaoka |first5=Kenichiro |last6=Masuda |first6=Hiroyasu |last7=Sugawara |first7=Masayuki |title=Super Hi-Vision as Next-Generation Television and Its Video Parameters |url=http://informationdisplay.org/IDArchive/2012/NovemberDecember/FrontlineTechnologySuperHiVisionasNextGen.aspx |website=Information Display|archive-url=https://web.archive.org/web/20180210024304/http://informationdisplay.org/IDArchive/2012/NovemberDecember/FrontlineTechnologySuperHiVisionasNextGen.aspx |archive-date=2018-02-10 }}</ref> While this allows the use of a limited bit depth without causing [[color banding]], and therefore reduces transmission bandwidth, it also prevents the encoding of deeply saturated colors that might be available in an alternate color spaces. Some RGB color spaces such as [[Adobe RGB color space|Adobe RGB]] and [[ProPhoto RGB color space|ProPhoto]] intended for the creation, rather than transmission, of images are designed with expanded gamuts to address this issue, however this does not mean the larger space has 'more colors". The numerical quantity of colors is related to bit depth and not the size or shape of the gamut. A large space with a low bit depth can be detrimental to the [[Color space#RGB density|gamut density]] and result in high <math> \Delta E </math> errors{{Explain|reason=Please define delta-E|date=January 2023}}. More recent color spaces such as [[Rec. 2020]] for UHD-TVs define an extremely large gamut covering 63.3% of the CIE 1931 space.<ref>{{cite web |last1=Baker |first1=Simon |title=The Pointer's Gamut - The Coverage of Real Surface Colors by RGB Color Spaces and Wide Gamut Displays |url=https://tftcentral.co.uk/articles/pointers_gamut |website=TFTCentral |access-date=13 January 2023 |language=en |date=19 February 2014}}</ref> This standard is not currently realisable with current LCD technology, and alternative architectures such as [[quantum dot]]<ref>{{cite journal |last1=Chen |first1=Haiwei |last2=He |first2=Juan |last3=Wu |first3=Shin-Tson |title=Recent Advances on Quantum-Dot-Enhanced Liquid-Crystal Displays |url=https://ieeexplore.ieee.org/document/7809081 |journal=IEEE Journal of Selected Topics in Quantum Electronics |pages=1–11 |doi=10.1109/JSTQE.2017.2649466 |date=September 2017|volume=23 |issue=5 |bibcode=2017IJSTQ..2349466C |s2cid=1400159 }}</ref> or [[OLED]]<ref>{{cite journal |last1=Huang |first1=Yuge |last2=Hsiang |first2=En-Lin |last3=Deng |first3=Ming-Yang |last4=Wu |first4=Shin-Tson |title=Mini-LED, Micro-LED and OLED displays: present status and future perspectives |journal=Light: Science & Applications |pages=105 |language=en |doi=10.1038/s41377-020-0341-9 |date=18 June 2020|volume=9 |issue=1 |pmid=32577221 |pmc=7303200 |bibcode=2020LSA.....9..105H |s2cid=235470310 }}</ref> based devices are currently{{When|date=March 2025}} in development. == Color space specifications employing the RGB color model == {| class="wikitable sortable" |- !rowspan=3| Color space !!rowspan=3| Reference Standard ! rowspan="3" |Primary Color Model!! rowspan="3" | Year !rowspan=3| [[Standard illuminant#White points of standard illuminants|White point]] !colspan=6| Color Primaries ! rowspan="2" |[[Gamma correction|Display]] [[Gamma correction|gamma]] ! colspan="5" |[[gamma correction|Transfer function parameters]] |- !colspan=2| Red !!colspan=2| Green !!colspan=2| Blue!! rowspan="2" title="decoding gamma" | ''γ'' ! title="offset 'a'" | α !! title="linear-domain threshold" | β !! title="linear gain" | δ !!title="transition point"| βδ |- ! x<sub>ʀ</sub> !! y<sub>ʀ</sub> !! x<sub>ɢ</sub> !! y<sub>ɢ</sub> !! x<sub>ʙ</sub> !! y<sub>ʙ</sub> !EOTF ! a + 1 !! K<sub>0</sub>/φ = E<sub>t</sub><!--= δ^(γ/(α-γ))--> !! φ<!--= α^γ*(γ-1)^(γ-1) / (a^(γ-1)*γ^γ)--> !! K<sub>0</sub><!--= a/(γ-1)--> |- ![[NTSC-J]] |''Based on NTSC(M)'' |Y′IQ, YCbCr |1987 |[[Standard illuminant#Illuminant series D|D93]] | rowspan="2" |0.63 | rowspan="3" |0.34 | rowspan="2" |0.31 | rowspan="3" |0.595 | rowspan="3" |0.155 | rowspan="3" |0.07 | rowspan="2" |Curved | | colspan="4" | |- ![[NTSC]], [[Multiple sub-Nyquist sampling encoding|MUSE]] |SMPTE RP 145 ([[SMPTE C|C]]), 170M, 240M |Y′IQ, YPbPr, YCbCr |1987 | rowspan="8" |[[Illuminant D65|D65]] |{{sfrac|20|9}} |1.1115 |0.0057 |4 |0.0228 |- !{{visible anchor|Apple RGB}} |''(Apple Computer)'' |RGB | |0.625 |0.28 |1.8 | | colspan="4" rowspan="2" | |- ![[PAL]] / [[SECAM]] |[[EBU]] 3213-E, [[Rec. 601|BT.470/601 (B/G)]] |Y′UV, YDbDr, YCbCr |1970 | rowspan="5" |0.64 | rowspan="9" |0.33 |0.29 | rowspan="4" |0.60 | rowspan="5" |0.15 | rowspan="5" |0.06 |Curved |{{sfrac|14|5}} |- ! [[sRGB]] | IEC 61966-2-1 |RGB|| 1996, 1999 | rowspan="3" |0.30 | rowspan="2" |2.2|| rowspan="2" title="2.4" | {{sfrac|12|5}} | rowspan="2" | 1.055 || rowspan="2" title="0.0031308049535" | 0.0031308 || rowspan="2" title="12.920020442059" | 12.92 || rowspan="2" title="0.040449936" | 0.04045 |- ![[scRGB]] |IEC 61966-2-2<!-- IEC 61966-2-4 xvYCC --> | |2003 |- ! [[High-definition television|HDTV]] | [[ITU-R]] [[Rec. 709|BT.709]] |YCbCr|| 1999 |Curved|| title="2.(2)" | {{sfrac|20|9}} | 1.099 || 0.004 || 4.5 || 0.018 |- ! [[Adobe RGB color space|Adobe RGB]] | ''(Adobe)'' |RGB|| 1998 | rowspan="5" | 0.21 || rowspan="5" | 0.71 |2.2|| title="≈ 2.2" | {{sfrac|563|256}} | colspan="4" rowspan="4" | |- ![[Multiplexed Analogue Components|M.A.C]]. |ITU-R BO.650-2<ref>{{Cite web |title=RECOMMENDATION ITU-R BO.650-2 *,** {{!}} Standards for conventional television systems for satellite broadcasting in the channels defined by Appendix 30 of the Radio Regulations |url=https://extranet.itu.int/brdocsearch/R-REC/R-REC-BO/R-REC-BO.650/R-REC-BO.650-2-199203-I/R-REC-BO.650-2-199203-I!!PDF-E.pdf#page=18 |website=}}</ref> |YPbPr |1985 | rowspan="4" |0.67 | rowspan="4" |0.14 | rowspan="4" |0.08 |2.8 | |- ! [[NTSC#Colorimetry|NTSC-FCC]] | [[Rec. 601|ITU-R BT.470/601 (M)]] |Y′IQ, YCbCr|| 1953 | rowspan="2" title="(0.3101, 0.3162)" | [[Standard illuminant#Illuminants B and C|C]] | rowspan="2" | 2.2<ref>47 CFR § 73.682 (20) (iv)</ref> | title="2.2" | {{sfrac|11|5}} |- ![[PAL-M]] |ITU-R BT.470-6<ref>{{Cite web |title=Recommendation ITU-R BT.470-6 {{!}} Conventional Television Systems |url=https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.470-6-199811-S!!PDF-E.pdf#page=2}}</ref> |Y′UV, YCbCr |1972 | |- ! [[eciRGB]] | ISO 22028-4 | || 2008, 2012 | title="(0.34567, 0.35850), ISO 22028: (0.3457, 0.3585) " | [[Standard illuminant#Illuminant series D|D50]] |1.8|| 3 | 1.16 || 0.008856 || 9.033 || 0.08 |- ![[DCI-P3]] |SMPTE RP 431-2 |YCbCr |2011 |6300K | rowspan="2" |0.68 | rowspan="2" |0.32 | rowspan="2" |0.265 | rowspan="2" |0.69 | rowspan="2" |0.15 | rowspan="2" |0.06 |2.6 |{{sfrac|13|5}} | colspan="4" | |- ![[Display P3]] |SMPTE EG 432-1 |RGB |2010 | rowspan="2" |D65 |~2.2 |{{sfrac|12|5}} | rowspan="1" |1.055 | rowspan="1" |0.0031308 | rowspan="1" |12.92 | rowspan="1" |0.04045 |- ![[Ultra-high-definition television|UHDTV]] |[[ITU-R]] [[Rec. 2020|BT.2020]], [[Rec. 2100|BT.2100]] |YCbCr |2012, 2016 |0.708 |0.292 |0.170 |0.797 |0.131 |0.046 |Curved | |1.0993 |0.018054 |4.5 |0.081243 |- ! [[Wide-gamut RGB color space|Wide Gamut]] | ''(Adobe)'' |RGB|| | rowspan="3" title="(0.34567, 0.35850), ISO 22028: (0.3457, 0.3585) " | [[Standard illuminant#Illuminant series D|D50]] | title="700 nm" | 0.7347 || 0.2653 || title="525 nm" | 0.1152 || 0.8264 || title="450 nm" | 0.1566 || 0.0177 |2.2|| title="= 2.19921875" | {{sfrac|563|256}} | colspan="4" | |- ! RIMM | ISO 22028-3 | || 2006, 2012 | 0.7347 || 0.2653 || 0.1596 || 0.8404 || 0.0366 || 0.0001 |2.222|| title="2.(2)" | {{sfrac|20|9}} || 1.099|| 0.0018 || 5.5 || 0.099 |- ! [[ProPhoto RGB color space|ProPhoto (ROMM)]] | ISO 22028-2 | || 2006, 2013 | 0.734699 || 0.265301 || 0.159597 || 0.840403 || 0.036598 || 000105 |1.8|| title="1.8" | {{sfrac|9|5}} | 1 || title="1/512" | 0.001953125 || 16 || 0.031248 |- ! [[CIE 1931 color space#CIE RGB color space|CIE RGB]] | rowspan="2" |[[CIE 1931 color space]] | | rowspan="2" | 1931 | rowspan="2" title="(1/3, 1/3)" | [[Standard illuminant#Illuminant E|E]] | 0.73474284 || 0.26525716 || 0.27377903 || 0.7174777 || 0.16655563 || 0.00891073 | | | colspan="4" rowspan="2" | |- title="mot RGB!" ! [[CIE 1931 color space|CIE XYZ]] ! | 1 || 0 || 0 || 1 || 0 || 0 | || 1 |} <!--JEDEC P22 / EIA397 (JC-22.1) FFmpeg -color_primaries jedec-p22 | D65 || 0.63 || 0.34 || 0.295 || 0.605 || 0.155 || 0.077 -->The [[CIE 1931 color space]] standard defines both the CIE RGB space, which is a color space with monochromatic [[Primary color|primaries]], and the CIE XYZ color space, which is functionally similar to a linear RGB color space, however the primaries are not physically realizable, thus are not described as red, green, and blue. M.A.C. is not to be confused with MacOS. Here, M.A.C.refers to [[Multiplexed Analogue Components]]. ==See also== *[[CIELUV color space]] *[[Web colors]] *[[RGB color model]] *[[RGBA color model]] ==References== {{Reflist}} ==External links== * [https://codenameart.com/downloads/free-rgb-color-chart/ RGB Color Chart.] * {{cite web|publisher=International Color Consortium (ICC) |url=https://www.color.org/chardata/rgb/rgb_registry.xalter |title=Three component color encoding registry |access-date=2022-02-11}} *{{cite web|author=Susstrunk, Buckley and Swen|url=http://infoscience.epfl.ch/getfile.py?mode=best&recid=34089|title=Standard RGB Color Spaces|format=PDF|access-date=November 18, 2005}} *{{cite web|author=Lindbloom, Bruce|url=http://www.brucelindbloom.com/index.html?WorkingSpaceInfo.html|title=RGB Working Space Information|access-date=November 18, 2005}} *{{cite web|author=Colantoni, Philippe|url=http://www.couleur.org/index.php?page=rgbcube|title=RGB cube transformation in different color spaces|url-status=dead|archive-url=https://web.archive.org/web/20080505081130/http://www.couleur.org/index.php?page=rgbcube|archive-date=2008-05-05}} {{Color space}} [[Category:Color space]]
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