RGB color space
Encyclopedia
An RGB color space is any additive color space
based on the RGB color model
. A particular RGB color space is defined by the three chromaticities
of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors. The complete specification of an RGB color space also requires a white point
chromaticity and a gamma correction
curve.
RGB is an initialism for red–green–blue.
defined by those particular color lamps. Swap the red lamp for one of a different brand that is slightly more orange, and there will be slightly different, and more limited gamut, since the set of all colors that can be produced with the three lights will be changed.
An LCD display can be thought of as a grid of thousands of little red, green, and blue lamps, each with their own dimmer switch. The gamut of the display will depend on the three colors used for the red, green and blue lights. A wide-gamut display will have very saturated, "pure" light colors, and thus be able to display very saturated, deep colors.
because the human visual system works in a way that is similar — though not quite identical — to an RGB color space. The most commonly used RGB color spaces are sRGB
and Adobe RGB
(which has a significantly larger gamut
). Adobe has recently developed another color space called Adobe Wide Gamut RGB
, which is even larger, in detriment to gamut density.
As of 2007, sRGB
is by far the most commonly used RGB color space, particularly in consumer grade digital cameras, HD video cameras, and computer monitors. HDTVs use a similar space, commonly called Rec. 709, sharing the sRGB primaries. The sRGB space is considered adequate for most consumer applications. Having all devices use the same color space is convenient in that an image does not need to be converted from one color space to another before being displayed. However, sRGB's limited gamut leaves out many highly saturated colors that can be produced by printers or in film, and thus is not ideal for some high quality applications. The wider gamut Adobe RGB is being built into more medium-grade digital cameras, and is favored by many professional graphic artists for its larger gamut
.
. In the table below the three primary colors and white points for various RGB spaces are given. The primary colors are specified in terms of their CIE 1931 color space
chromaticity coordinates (x,y).
The CIE 1931 color space
standard defines both the CIE RGB space, which is an RGB color space with monochromatic primaries
, and the CIE XYZ color space, which works like an RGB color space except that it has non-physical primaries that cannot be said to be red, green, and blue.
Color space
A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components...
based on the RGB color model
RGB color model
The RGB color model is an additive color model in which red, green, and blue light is added together in various ways to reproduce a broad array of colors...
. A particular RGB color space is defined by the three chromaticities
Chromaticity
Chromaticity is an objective specification of the quality of a color regardless of its luminance, that is, as determined by its hue and colorfulness ....
of the red, green, and blue additive primaries, and can produce any chromaticity that is the triangle defined by those primary colors. The complete specification of an RGB color space also requires a white point
White point
A white point is a set of tristimulus values or chromaticity coordinates that serve to define the color "white" in image capture, encoding, or reproduction. Depending on the application, different definitions of white are needed to give acceptable results...
chromaticity and a gamma correction
Gamma correction
Gamma correction, gamma nonlinearity, gamma encoding, or often simply gamma, is the name of a nonlinear operation used to code and decode luminance or tristimulus values in video or still image systems...
curve.
RGB is an initialism for red–green–blue.
Intuition
An RGB color space can be easily understood by thinking of it as "all possible colors" that can be made from three colourants for red, green and blue. Imagine, for example, shining three lights together onto a white wall: one red light, one green light, and one blue light, each with dimmer switches. If only the red light is on, the wall will look red. If only the green light is on, the wall will look green. If the red and green lights are on together, the wall will look yellow. Dim the red light and the wall will become more of a yellow-green. Dim the green light instead, and the wall will become more orange. Bringing up the blue light a bit will cause the orange to become less saturated and more whitish. In all, each setting of the three dimmer switches will produce a different result, either in color or in brightness or both. The set of all possible results is the gamutGamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
defined by those particular color lamps. Swap the red lamp for one of a different brand that is slightly more orange, and there will be slightly different, and more limited gamut, since the set of all colors that can be produced with the three lights will be changed.
An LCD display can be thought of as a grid of thousands of little red, green, and blue lamps, each with their own dimmer switch. The gamut of the display will depend on the three colors used for the red, green and blue lights. A wide-gamut display will have very saturated, "pure" light colors, and thus be able to display very saturated, deep colors.
Applications
RGB is a convenient color model for computer graphicsComputer graphics
Computer graphics are graphics created using computers and, more generally, the representation and manipulation of image data by a computer with help from specialized software and hardware....
because the human visual system works in a way that is similar — though not quite identical — to an RGB color space. The most commonly used RGB color spaces are sRGB
SRGB color space
sRGB is a standard RGB color space created cooperatively by HP and Microsoft in 1996 for use on monitors, printers, and the Internet.sRGB uses the ITU-R BT.709 primaries, the same as are used in studio monitors and HDTV, and a transfer function typical of CRTs...
and Adobe RGB
Adobe RGB color space
The Adobe RGB color space is an RGB color space developed by Adobe Systems in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, but by using RGB primary colors on a device such as the computer display...
(which has a significantly larger gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
). Adobe has recently developed another color space called Adobe Wide Gamut RGB
Adobe Wide Gamut RGB color space
The wide-gamut RGB color space is an RGB color space developed by Adobe Systems, that offers a large gamut by using pure spectral primary colors....
, which is even larger, in detriment to gamut density.
As of 2007, sRGB
SRGB color space
sRGB is a standard RGB color space created cooperatively by HP and Microsoft in 1996 for use on monitors, printers, and the Internet.sRGB uses the ITU-R BT.709 primaries, the same as are used in studio monitors and HDTV, and a transfer function typical of CRTs...
is by far the most commonly used RGB color space, particularly in consumer grade digital cameras, HD video cameras, and computer monitors. HDTVs use a similar space, commonly called Rec. 709, sharing the sRGB primaries. The sRGB space is considered adequate for most consumer applications. Having all devices use the same color space is convenient in that an image does not need to be converted from one color space to another before being displayed. However, sRGB's limited gamut leaves out many highly saturated colors that can be produced by printers or in film, and thus is not ideal for some high quality applications. The wider gamut Adobe RGB is being built into more medium-grade digital cameras, and is favored by many professional graphic artists for its larger gamut
Gamut
In color reproduction, including computer graphics and photography, the gamut, or color gamut , is a certain complete subset of colors. The most common usage refers to the subset of colors which can be accurately represented in a given circumstance, such as within a given color space or by a...
.
Specifications
RGB spaces are generally specified by defining three primary colors and a white pointWhite point
A white point is a set of tristimulus values or chromaticity coordinates that serve to define the color "white" in image capture, encoding, or reproduction. Depending on the application, different definitions of white are needed to give acceptable results...
. In the table below the three primary colors and white points for various RGB spaces are given. The primary colors are specified in terms of their CIE 1931 color space
CIE 1931 color space
In the study of color perception, one of the first mathematically defined color spaces is the CIE 1931 XYZ color space, created by the International Commission on Illumination in 1931....
chromaticity coordinates (x,y).
| Color Space | Gamut | White Point | Primaries | |||||
|---|---|---|---|---|---|---|---|---|
| xR | yR | xG | yG | xB | yB | |||
| ISO RGB | Limited | floating | floating | |||||
| Extended ISO RGB | Unlimited (signed) | floating | floating | |||||
| HDTV High-definition television High-definition television is video that has resolution substantially higher than that of traditional television systems . HDTV has one or two million pixels per frame, roughly five times that of SD... (ITU-R ITU-R The ITU Radiocommunication Sector is one of the three sectors of the International Telecommunication Union and is responsible for radio communication.... BT.709 Rec. 709 ITU-R Recommendation BT.709, more commonly known by the abbreviations Rec. 709 or BT.709, standardizes the format of high-definition television, having 16:9 aspect ratio. The first edition of the standard was approved in 1990.... ), sRGB SRGB color space sRGB is a standard RGB color space created cooperatively by HP and Microsoft in 1996 for use on monitors, printers, and the Internet.sRGB uses the ITU-R BT.709 primaries, the same as are used in studio monitors and HDTV, and a transfer function typical of CRTs... |
CRT | D65 | 0.64 | 0.33 | 0.30 | 0.60 | 0.15 | 0.06 |
| scRGB | Unlimited (signed) | D65 | 0.64 | 0.33 | 0.30 | 0.60 | 0.15 | 0.06 |
| ROMM RGB ProPhoto RGB color space The ProPhoto RGB color space, also known as ROMM RGB , is an output referred RGB color space developed by Kodak. It offers an especially large gamut designed for use with photographic output in mind... |
Wide | D50 | 0.7347 | 0.2653 | 0.1596 | 0.8404 | 0.0366 | 0.0001 |
| Adobe RGB 98 Adobe RGB color space The Adobe RGB color space is an RGB color space developed by Adobe Systems in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, but by using RGB primary colors on a device such as the computer display... |
CRT | D65 | 0.64 | 0.33 | 0.21 | 0.71 | 0.15 | 0.06 |
| CRT | D65 | 0.625 | 0.34 | 0.28 | 0.595 | 0.155 | 0.07 | |
| NTSC NTSC NTSC, named for the National Television System Committee, is the analog television system that is used in most of North America, most of South America , Burma, South Korea, Taiwan, Japan, the Philippines, and some Pacific island nations and territories .Most countries using the NTSC standard, as... (1953) (FCC Federal Communications Commission The Federal Communications Commission is an independent agency of the United States government, created, Congressional statute , and with the majority of its commissioners appointed by the current President. The FCC works towards six goals in the areas of broadband, competition, the spectrum, the... 1953, ITU-R BT.470 System M) |
CRT | C | 0.67 | 0.33 | 0.21 | 0.71 | 0.14 | 0.08 |
| NTSC (1987) (SMPTE RP 145 "SMPTE C", SMPTE 170M) |
CRT | D65 | 0.63 | 0.34 | 0.31 | 0.595 | 0.155 | 0.07 |
| PAL PAL PAL, short for Phase Alternating Line, is an analogue television colour encoding system used in broadcast television systems in many countries. Other common analogue television systems are NTSC and SECAM. This page primarily discusses the PAL colour encoding system... /SECAM SECAM SECAM, also written SÉCAM , is an analog color television system first used in France.... (1970) (EBU Tech. 3213, ITU-R ITU-R The ITU Radiocommunication Sector is one of the three sectors of the International Telecommunication Union and is responsible for radio communication.... BT.470 System B, G) |
CRT | D65 | 0.64 | 0.33 | 0.29 | 0.60 | 0.15 | 0.06 |
| Adobe Wide Gamut RGB Adobe Wide Gamut RGB color space The wide-gamut RGB color space is an RGB color space developed by Adobe Systems, that offers a large gamut by using pure spectral primary colors.... |
Wide | D50 | 0.735 | 0.265 | 0.115 | 0.826 | 0.157 | 0.018 |
| CIE (1931) CIE 1931 color space In the study of color perception, one of the first mathematically defined color spaces is the CIE 1931 XYZ color space, created by the International Commission on Illumination in 1931.... |
Wide | E | 0.7347 | 0.2653 | 0.2738 | 0.7174 | 0.1666 | 0.0089 |
| CIE XYZ (not RGB) | Unlimited | E | 0 | 1 | 1 | 0 | 0 | 0 |
The CIE 1931 color space
CIE 1931 color space
In the study of color perception, one of the first mathematically defined color spaces is the CIE 1931 XYZ color space, created by the International Commission on Illumination in 1931....
standard defines both the CIE RGB space, which is an RGB color space with monochromatic primaries
Primary color
Primary colors are sets of colors that can be combined to make a useful range of colors. For human applications, three primary colors are usually used, since human color vision is trichromatic....
, and the CIE XYZ color space, which works like an RGB color space except that it has non-physical primaries that cannot be said to be red, green, and blue.
See also
- CIE 1931 XYZ color spaceCIE 1931 color spaceIn the study of color perception, one of the first mathematically defined color spaces is the CIE 1931 XYZ color space, created by the International Commission on Illumination in 1931....
- CIEInternational Commission on IlluminationThe International Commission on Illumination is the international authority on light, illumination, color, and color spaces...
L*a*b* color spaceLab color spaceA Lab color space is a color-opponent space with dimension L for lightness and a and b for the color-opponent dimensions, based on nonlinearly compressed CIE XYZ color space coordinates.... - Wide-gamut RGB color space
- ProPhoto RGBProPhoto RGB color spaceThe ProPhoto RGB color space, also known as ROMM RGB , is an output referred RGB color space developed by Kodak. It offers an especially large gamut designed for use with photographic output in mind...
- Adobe RGB color spaceAdobe RGB color spaceThe Adobe RGB color space is an RGB color space developed by Adobe Systems in 1998. It was designed to encompass most of the colors achievable on CMYK color printers, but by using RGB primary colors on a device such as the computer display...
- scRGB
- sRGB
- Web colorsWeb colorsWeb colors are colors used in designing web pages, and the methods for describing and specifying those colors. Hexadecimal color codes begin with a hash ....