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{{short description|Any additive color space based on the RGB color model}}
{{short description|Any additive color space based on the RGB color model}}
{{more citations needed|date=December 2014}}
{{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.]]
[[File:CIE1931xy_gamut_comparison.svg |thumb|300px|1931 CIE chromaticity diagram showing some RGB color spaces as defined by their chromaticity triangles]]


An '''<abbr title="red–green–blue">RGB</abbr> color space''' is any [[Additive color|additive]] [[color space]] based on the [[RGB color model]].<ref>{{cite book |last1=Saini |first1= Harvinder Singh |last2=Sayal|first2=Rishi |last3= Buyya|first3= Rajkumar |last4=Aliseri |first4=Govardhan |date=2020 |title=Innovations in Computer Science and Engineering |url=https://www.google.com.tw/books/edition/Innovations_in_Computer_Science_and_Engi/t1TUDwAAQBAJ?hl=en&gbpv=1&dq=%22an+RGB+color+space+is%22&pg=PA235&printsec=frontcover |location=Singapore |publisher= Springer Singapore|page=235 |isbn=9789811520433}}</ref><ref>{{cite web|author=Pascale, Danny|url=http://www.babelcolor.com/download/A%20review%20of%20RGB%20color%20spaces.pdf|format=PDF|title=A Review of RGB color spaces...from xyY to R'G'B'|access-date=20 October 2021}}</ref> An RGB color space is defined by [[chromaticity]] coordinates of the red, green, and blue [[additive primaries]], the white point which is usually a [[standard illuminant]], and the [[transfer function]] which is also known as the [[tone response curve]] (TRC) or [[gamma]]. Applying [[Grassmann's laws (color science)|Grassmann's law]] of light additivity, a colorspace so defined can produce colors which are enclosed within the 2D triangle on the chromaticity diagram defined by those primary coordinates. The TRC and white point further define the possible colors, creating a volume in a 3D shape that never exceeds the triangular bounds.<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>
'''<abbr title="red–green–blue">RGB</abbr> color spaces''' is 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.
⚫
The primary colors are often specified in terms of their [[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 uses the 2° standard observer, an averaging of experimental data defining the limits of the human color [[gamut]].


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.
==Introduction==
⚫
[[File:RGB Cube Show lowgamma cutout b.png|thumb|300px|RGB-Cube]]
The normal human eye contains three type of photosensitive cells called [[Trichromacy|cones]], which are sensitive to wavelengths of light that we generally categorize as red, green, and blue.


==Definition==
An RGB color space uses illuminated primaries which are chosen to stimulate each cone type as independently as possible. In this way, mixing the three lights in different proportions can stimulate the cones in the eye and create a color perception.
⚫
[[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>
⚫
==Applications==
⚫
[[Image:1Mcolors.png|thumbnail|100px|left|One million colors in RGB space, visible in full-size image.]]


⚫
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]].
Color television was the first practical use of an RGB color space for presenting images. [[NTSC]] was adopted in 1953 in North America. Other parts of the world adopted either [[PAL]] or [[SECAM]]. While these RGB color spaces created colors using additive red, green, and blue primaries, the broadcast signal was encoded from RGB components to a composite signal such as [[YIQ]].


⚫
==Applications==
These early RGB spaces were defined in part by the phosphor used inside the [[cathode ray tube|CRT]] and the gamma of the electron beam. Today, [[LCD]] is among the most common technologies in use.
{{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]]
An LCD display can be thought of as a grid of millions of tiny red, green, and blue lights, each with their own dimmer control. The gamut of the display depends on how far apart the red, green, and blue color coordinates are on the chromaticity diagram, the nature of the TRC and the signal encoding of the 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 an RGB color space known as BT.709. A common standard for computer monitors is [[sRGB color space|sRGB]] which uses the same color primaries and white point as BT.709, but the transfer function is different as HDTV is intended for a dark living room, and sRGB is intended for a brighter office environment.


[[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}}.
At one time, sRGB was the most commonly used color space for computer displays, and having all devices use the same calibrated color space is useful so that color conversions do not need to take place before images are displayed. sRGB's limited gamut fits well into an 8-bit image, but also leaves out deeply saturated colors that might be available in an alternate RGB color spaces.


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 in development.
Some color spaces defined for this purpose with RGB primaries are and [[Adobe RGB color space|Adobe RGB]] (which has a larger [[gamut]]), and [[ProPhoto RGB color space|ProPhoto]], which is even larger in terms of gamut volume. However this does not mean the larger space has 'more colors," as 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.


== RGB color space specifications ==
== Color space specifications employing the RGB color model ==
{| class="wikitable"
{| class="wikitable sortable"
|+ RGB color spaces
|-
|-
!rowspan=3| Color space !!rowspan=3| Reference Standard !! rowspan="3" | Year
!rowspan=3| Color space !!rowspan=3| Reference Standard
! rowspan="3" |Primary Color Model for Signalling!! rowspan="3" | Year
!rowspan=3| [[Standard illuminant#White points of standard illuminants|White point]]
!rowspan=3| [[Standard illuminant#White points of standard illuminants|White point]]
!colspan=6| Primaries
!colspan=6| Color Primaries
! rowspan="2" |[[Gamma correction|Display]]
! rowspan="2" |[[Gamma correction|Display]]
[[Gamma correction|gamma]]
[[Gamma correction|gamma]]
Line 48: Line 49:
![[NTSC-J]]
![[NTSC-J]]
|''Based on NTSC(M)''
|''Based on NTSC(M)''
|YCbCr
|1987
|1987
|[[Standard illuminant#Illuminant series D|D93]]
|[[Standard illuminant#Illuminant series D|D93]]
Line 56: Line 58:
| rowspan="3" |0.155
| rowspan="3" |0.155
| rowspan="3" |0.07
| rowspan="3" |0.07
| rowspan="2" |2.5
| rowspan="2" |Curved
|
|
| colspan="4" |
| colspan="4" |
Line 62: Line 64:
![[NTSC]], [[Multiple sub-Nyquist sampling encoding|MUSE]]
![[NTSC]], [[Multiple sub-Nyquist sampling encoding|MUSE]]
|SMPTE RP 145 ([[SMPTE C|C]]), 170M, 240M
|SMPTE RP 145 ([[SMPTE C|C]]), 170M, 240M
|YCbCr
|1987
|1987
| rowspan="8" |[[Illuminant D65|D65]]
| rowspan="8" |[[Illuminant D65|D65]]
Line 72: Line 75:
!{{visible anchor|Apple RGB}}
!{{visible anchor|Apple RGB}}
|''(Apple Computer)''
|''(Apple Computer)''
|RGB
|
|
|0.625
|0.625
Line 81: Line 85:
![[PAL]] / [[SECAM]]
![[PAL]] / [[SECAM]]
|[[EBU]] 3213-E, [[Rec. 601|BT.470/601 (B/G)]]
|[[EBU]] 3213-E, [[Rec. 601|BT.470/601 (B/G)]]
|YCbCr
|1970
|1970
| rowspan="5" |0.64
| rowspan="5" |0.64
Line 88: Line 93:
| rowspan="5" |0.15
| rowspan="5" |0.15
| rowspan="5" |0.06
| rowspan="5" |0.06
|Curved
|2.8
|{{sfrac|14|5}}
|{{sfrac|14|5}}
|-
|-
! [[sRGB color space|sRGB]]
! [[sRGB]]
| IEC 61966-2-1 || 1996, 1999
| IEC 61966-2-1
|RGB|| 1996, 1999
| rowspan="3" |0.30
| rowspan="3" |0.30
| rowspan="2" |2.2|| rowspan="2" title="2.4" | {{sfrac|12|5}}
| rowspan="2" |2.2|| rowspan="2" title="2.4" | {{sfrac|12|5}}
Line 99: Line 105:
![[scRGB]]
![[scRGB]]
|IEC 61966-2-2<!-- IEC 61966-2-4 xvYCC -->
|IEC 61966-2-2<!-- IEC 61966-2-4 xvYCC -->
|
|2003
|2003
|-
|-
! [[High-definition television|HDTV]]
! [[High-definition television|HDTV]]
| [[ITU-R]] [[Rec. 709|BT.709]]|| 1999
| [[ITU-R]] [[Rec. 709|BT.709]]
|YCbCr|| 1999
|2.4|| title="2.(2)" | {{sfrac|20|9}}
|Curved|| title="2.(2)" | {{sfrac|20|9}}
| 1.099 || 0.004 || 4.5 || 0.018
| 1.099 || 0.004 || 4.5 || 0.018
|-
|-
! [[Adobe RGB color space|Adobe RGB]]
! [[Adobe RGB color space|Adobe RGB]]
| ''(Adobe)''|| 1998
| ''(Adobe)''
|RGB|| 1998
| rowspan="5" | 0.21 || rowspan="5" | 0.71
| rowspan="5" | 0.21 || rowspan="5" | 0.71
|2.2|| title="≈ 2.2" | {{sfrac|563|256}}
|2.2|| title="≈ 2.2" | {{sfrac|563|256}}
Line 113: Line 122:
|-
|-
![[Multiplexed Analogue Components|M.A.C]].
![[Multiplexed Analogue Components|M.A.C]].
|ITU-R BO.650-2<ref>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 {{Bare URL PDF|date=March 2022}}</ref>
|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>
|
|1985
|1985
| rowspan="4" |0.67
| rowspan="4" |0.67
Line 122: Line 132:
|-
|-
! [[NTSC#Colorimetry|NTSC-FCC]]
! [[NTSC#Colorimetry|NTSC-FCC]]
| [[Rec. 601|ITU-R BT.470/601 (M)]]|| 1953
| [[Rec. 601|ITU-R BT.470/601 (M)]]
|YCbCr|| 1953
| rowspan="2" title="(0.3101, 0.3162)" | [[Standard illuminant#Illuminants B and C|C]]
| 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>
|2.5|| title="2.2" | {{sfrac|11|5}}
| title="2.2" | {{sfrac|11|5}}
|-
|-
![[PAL-M]]
![[PAL-M]]
|ITU-R BT.470-6<ref>https://www.itu.int/dms_pubrec/itu-r/rec/bt/R-REC-BT.470-6-199811-S!!PDF-E.pdf#page=2 {{Bare URL PDF|date=March 2022}}</ref>
|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>
|YCbCr
|1972
|1972
|2.2
|
|
|-
|-
! [[eciRGB]]
! [[eciRGB]]
| ISO 22028-4 || 2008, 2012
| ISO 22028-4
| || 2008, 2012
| title="(0.34567, 0.35850), ISO 22028: (0.3457, 0.3585) " | [[Standard illuminant#Illuminant series D|D50]]
| title="(0.34567, 0.35850), ISO 22028: (0.3457, 0.3585) " | [[Standard illuminant#Illuminant series D|D50]]
|1.8|| 3
|1.8|| 3
Line 140: Line 153:
![[DCI-P3]]
![[DCI-P3]]
|SMPTE RP 431-2
|SMPTE RP 431-2
|YCbCr
|2011
|2011
|6300K
|6300K
Line 154: Line 168:
![[Display P3]]
![[Display P3]]
|SMPTE EG 432-1
|SMPTE EG 432-1
|RGB
|2010
|2010
| rowspan="2" |D65
| rowspan="2" |D65
Line 165: Line 180:
![[Ultra-high-definition television|UHDTV]]
![[Ultra-high-definition television|UHDTV]]
|[[ITU-R]] [[Rec. 2020|BT.2020]], [[Rec. 2100|BT.2100]]
|[[ITU-R]] [[Rec. 2020|BT.2020]], [[Rec. 2100|BT.2100]]
|YCbCr
|2012, 2016
|2012, 2016
|0.708
|0.708
Line 172: Line 188:
|0.131
|0.131
|0.046
|0.046
|Curved
|2.4
|
|
|1.0993
|1.0993
Line 180: Line 196:
|-
|-
! [[Wide-gamut RGB color space|Wide Gamut]]
! [[Wide-gamut RGB color space|Wide Gamut]]
| ''(Adobe)''||
| ''(Adobe)''
|RGB||
| rowspan="3" title="(0.34567, 0.35850)" | [[Standard illuminant#Illuminant series D|D50]]
| rowspan="3" title="(0.34567, 0.35850), ISO 22028: (0.3457, 0.3585) " | [[Standard illuminant#Illuminant series D|D50]]
| title="700 nm" | 0.735 || 0.265 || title="525 nm" | 0.115 || 0.826 || title="450 nm" | 0.157 || 0.018
| 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}}
|2.2|| title="= 2.19921875" | {{sfrac|563|256}}
| colspan="4" |
| colspan="4" |
|-
|-
! RIMM
! RIMM
| ISO 22028-3 || 2006, 2012
| ISO 22028-3
| || 2006, 2012
| rowspan="3" | 0.7347 || rowspan="3" | 0.2653 || rowspan="2" | 0.1596 || rowspan="2" | 0.8404 || rowspan="2" | 0.0366 || rowspan="2" | 0.0001
| 0.7347 || 0.2653 || 0.1596 || 0.8404 || 0.0366 || 0.0001
|2.222|| title="2.(2)" | {{sfrac|20|9}}
|2.222|| title="2.(2)" | {{sfrac|20|9}}
|| 1.099|| 0.0018 || 5.5 || 0.099
|| 1.099|| 0.0018 || 5.5 || 0.099
|-
|-
! [[ProPhoto RGB color space|ProPhoto (ROMM)]]
! [[ProPhoto RGB color space|ProPhoto (ROMM)]]
| ISO 22028-2 || 2006, 2013
| ISO 22028-2
| || 2006, 2013
| 0.734699 || 0.265301 || 0.159597 || 0.840403 || 0.036598 || 000105
|1.8|| title="1.8" | {{sfrac|9|5}}
|1.8|| title="1.8" | {{sfrac|9|5}}
| 1 || title="1/512" | 0.001953125 || 16 || 0.031248
| 1 || title="1/512" | 0.001953125 || 16 || 0.031248
Line 199: Line 219:
! [[CIE 1931 color space#CIE RGB color space|CIE RGB]]
! [[CIE 1931 color space#CIE RGB color space|CIE RGB]]
| rowspan="2" |[[CIE 1931 color space]]
| rowspan="2" |[[CIE 1931 color space]]
|
| rowspan="2" | 1931
| rowspan="2" | 1931
| rowspan="2" title="(1/3, 1/3)" | [[Standard illuminant#Illuminant E|E]]
| rowspan="2" title="(1/3, 1/3)" | [[Standard illuminant#Illuminant E|E]]
| 0.2738 || 0.7174 || 0.1666 || 0.0089
| 0.73474284 || 0.26525716 || 0.27377903 || 0.7174777 || 0.16655563 || 0.00891073
|
|
|
|
Line 207: Line 228:
|- title="mot RGB!"
|- title="mot RGB!"
! [[CIE 1931 color space|CIE XYZ]]
! [[CIE 1931 color space|CIE XYZ]]
!
| 1 || 0 || 0 || 1 || 0 || 0
| 1 || 0 || 0 || 1 || 0 || 0
| || 1
| || 1
Line 212: Line 234:
<!--JEDEC P22 / EIA397 (JC-22.1)
<!--JEDEC P22 / EIA397 (JC-22.1)
FFmpeg -color_primaries jedec-p22
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 an RGB 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.
| 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]].
M.A.C. is not to be confused with MacOS. Here, M.A.C.refers to [[Multiplexed Analogue Components]].
Line 227: Line 249:


==External links==
==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|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=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}}

Latest revision as of 17:46, 18 November 2024

1931 CIE chromaticity diagram showing some RGB color spaces as defined by their chromaticity triangles

RGB color spaces is a category of additive colorimetric color spaces[1] specifying part of its absolute color space definition using the RGB color model.[2]

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

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RGB cube

The normal human eye contains three types of color-sensitive cone cells. 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 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 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 vertices.[3]

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 2° standard observer.

Applications

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See also: List of Color Spaces
One million colors in RGB space, visible in full-size image

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 LCDs 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. 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] The gamut of these spaces is limited, covering only 35.9% of the CIE 1931 gamut.[4] 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 and 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 gamut density and result in high errors[further explanation needed].

More recent color spaces such as Rec. 2020 for UHD-TVs define an extremely large gamut covering 63.3% of the CIE 1931 space.[5] This standard is not currently realisable with current LCD technology, and alternative architectures such as quantum dot[6] or OLED[7] based devices are currently in development.

Color space specifications employing the RGB color model

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Color space Reference Standard Primary Color Model for Signalling Year White point Color Primaries Display

gamma

Transfer function parameters
Red Green Blue γ α β δ βδ
xʀ yʀ xɢ yɢ xʙ yʙ EOTF a + 1 K0/φ = Et φ K0
NTSC-J Based on NTSC(M) YCbCr 1987 D93 0.63 0.34 0.31 0.595 0.155 0.07 Curved
NTSC, MUSE SMPTE RP 145 (C), 170M, 240M YCbCr 1987 D65 ⁠20/9⁠ 1.1115 0.0057 4 0.0228
Apple RGB (Apple Computer) RGB 0.625 0.28 1.8
PAL / SECAM EBU 3213-E, BT.470/601 (B/G) YCbCr 1970 0.64 0.33 0.29 0.60 0.15 0.06 Curved ⁠14/5⁠
sRGB IEC 61966-2-1 RGB 1996, 1999 0.30 2.2 ⁠12/5⁠ 1.055 0.0031308 12.92 0.04045
scRGB IEC 61966-2-2 2003
HDTV ITU-R BT.709 YCbCr 1999 Curved ⁠20/9⁠ 1.099 0.004 4.5 0.018
Adobe RGB (Adobe) RGB 1998 0.21 0.71 2.2 ⁠563/256⁠
M.A.C. ITU-R BO.650-2[8] 1985 0.67 0.14 0.08 2.8
NTSC-FCC ITU-R BT.470/601 (M) YCbCr 1953 C 2.2[9] ⁠11/5⁠
PAL-M ITU-R BT.470-6[10] YCbCr 1972
eciRGB ISO 22028-4 2008, 2012 D50 1.8 3 1.16 0.008856 9.033 0.08
DCI-P3 SMPTE RP 431-2 YCbCr 2011 6300K 0.68 0.32 0.265 0.69 0.15 0.06 2.6 ⁠13/5⁠
Display P3 SMPTE EG 432-1 RGB 2010 D65 ~2.2 ⁠12/5⁠ 1.055 0.0031308 12.92 0.04045
UHDTV ITU-R BT.2020, 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 (Adobe) RGB D50 0.7347 0.2653 0.1152 0.8264 0.1566 0.0177 2.2 ⁠563/256⁠
RIMM ISO 22028-3 2006, 2012 0.7347 0.2653 0.1596 0.8404 0.0366 0.0001 2.222 ⁠20/9⁠ 1.099 0.0018 5.5 0.099
ProPhoto (ROMM) ISO 22028-2 2006, 2013 0.734699 0.265301 0.159597 0.840403 0.036598 000105 1.8 ⁠9/5⁠ 1 0.001953125 16 0.031248
CIE RGB CIE 1931 color space 1931 E 0.73474284 0.26525716 0.27377903 0.7174777 0.16655563 0.00891073
CIE XYZ 1 0 0 1 0 0 1

The CIE 1931 color space standard defines both the CIE RGB space, which is a color space with monochromatic 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

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References

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  1. ^ "colorimetric colour space (definition)". France: International Commission on Illumination (CIE). Retrieved 8 October 2023.
  2. ^ Pascale, Danny. "A Review of RGB color spaces...from xyY to R'G'B'" (PDF). Retrieved 20 October 2021.
  3. ^ Hunt, R. W. G (2004). The Reproduction of Colour (6th ed.). Chichester UK: Wiley–IS&T Series in Imaging Science and Technology. ISBN 0-470-02425-9.
  4. ^ Yamashita, Takayuki; Nishida, Yukihiro; Emoto, Masaki; Ohmura, Kohei; Masaoka, Kenichiro; Masuda, Hiroyasu; Sugawara, Masayuki. "Super Hi-Vision as Next-Generation Television and Its Video Parameters". Information Display. Archived from the original on 2018-02-10.
  5. ^ Baker, Simon (19 February 2014). "The Pointer's Gamut - The Coverage of Real Surface Colors by RGB Color Spaces and Wide Gamut Displays". TFTCentral. Retrieved 13 January 2023.
  6. ^ Chen, Haiwei; He, Juan; Wu, Shin-Tson (September 2017). "Recent Advances on Quantum-Dot-Enhanced Liquid-Crystal Displays". IEEE Journal of Selected Topics in Quantum Electronics. 23 (5): 1–11. Bibcode:2017IJSTQ..2349466C. doi:10.1109/JSTQE.2017.2649466. S2CID 1400159.
  7. ^ Huang, Yuge; Hsiang, En-Lin; Deng, Ming-Yang; Wu, Shin-Tson (18 June 2020). "Mini-LED, Micro-LED and OLED displays: present status and future perspectives". Light: Science & Applications. 9 (1): 105. Bibcode:2020LSA.....9..105H. doi:10.1038/s41377-020-0341-9. PMC 7303200. PMID 32577221. S2CID 235470310.
  8. ^ "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" (PDF).
  9. ^ 47 CFR § 73.682 (20) (iv)
  10. ^ "Recommendation ITU-R BT.470-6 | Conventional Television Systems" (PDF).
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