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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. When this model is associated with a precise description of how the components are to be interpreted (viewing conditions, etc.), the resulting set of colors is called a color space. This section describes ways in which human color vision can be modeled. Image File history File links Question_book-3. ... Color is an important part of the visual arts. ... In mathematics, a tuple is a finite sequence (also known as an ordered list) of objects, each of a specified type. ... A comparison of different color spaces. ... Color vision is the capacity of an organism or machine to distinguish objects based on the wavelengths (or frequencies) of the light they reflect or emit. ...

Tristimulus color space

3D representation of the human color space.

One can picture this space as a region in three-dimensional Euclidean space if one identifies the x, y, and z axes with the stimuli for the long-wavelength (L), medium-wavelength (M), and short-wavelength (S) receptors. The origin, (S,M,L) = (0,0,0), corresponds to black. White has no definite position in this diagram; rather it is defined according to the color temperature or white balance as desired or as available from ambient lighting. The human color space is a horse-shoe-shaped cone such as shown here (see also CIE chromaticity diagram below), extending from the origin to, in principle, infinity. In practice, the human color receptors will be saturated or even be damaged at extremely-high light intensities, but such behavior is not part of the CIE color space and neither is the changing color perception at low light levels (see: Kruithof curve). Gamut of the human eye See also: source code: File links The following pages link to this file: Color Image:Gamut. ... Gamut of the human eye See also: source code: File links The following pages link to this file: Color Image:Gamut. ... Around 300 BC, the Greek mathematician Euclid laid down the rules of what has now come to be called Euclidean geometry, which is the study of the relationships between angles and distances in space. ... The CIE 1931 x,y chromaticity space, also showing the chromaticities of black-body light sources of various temperatures, and lines of constant correlated color temperature Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. ... 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. ... The CIE 1931 color space chromaticity diagram with wavelengths in nanometers. ... In color vision, the color experience of a given light mixture may vary with absolute luminosity, due to the fact that both rods and cones are active at once in the eye, with each having different color curves, and rods taking over gradually from cones as the brightness of the...

The most saturated colors are located at the outer rim of the region, with brighter colors farther removed from the origin. As far as the responses of the receptors in the eye are concerned, there is no such thing as "brown" or "gray" light. The latter color names refer to orange and white light respectively, with an intensity that is lower than the light from surrounding areas. One can observe this by watching the screen of an overhead projector during a meeting: one sees black lettering on a white background, even though the "black" has in fact not become darker than the white screen on which it is projected before the projector was turned on. The "black" areas have not actually become darker but appear "black" relative to the higher intensity "white" projected onto the screen around it. See also color constancy. Color is an important part of the visual arts. ...

The human tristimulus space has the property that additive mixing of colors corresponds to the adding of vectors in this space. This makes it easy to, for example, describe the possible colors (gamut) that can be constructed from the red, green, and blue primaries in a computer display. In color reproduction, including computer graphics and photography, the gamut, or color gamut (pronounced ), is a certain complete subset of colors. ...

CIE XYZ color space

Main article: CIE 1931 color space

CIE1931 Standard Colorimetric Observer functions between 380 nm and 780 nm (at 5 nm intervals).

One of the first mathematically defined color spaces is the CIE XYZ color space (also known as CIE 1931 color space), created by the International Commission on Illumination in 1931. These data were measured for human observers and a 2-degree field of view. In 1964, supplemental data for a 10-degree field of view were published. In the study of the perception of color, one of the first mathematically defined color spaces was the CIE XYZ color space (also known as CIE 1931 color space), created by the International Commission on Illumination (CIE) in 1931. ... Image File history File links Download high resolution version (1300x975, 146 KB) CIE 1931 XYZ color matching functions File links The following pages link to this file: Color models CIE 1931 color space ... Image File history File links Download high resolution version (1300x975, 146 KB) CIE 1931 XYZ color matching functions File links The following pages link to this file: Color models CIE 1931 color space ... The CIE 1931 color space chromaticity diagram with wavelengths in nanometers. ...

Note that the tabulated sensitivity curves have a certain amount of arbitrariness in them. The shapes of the individual X, Y and Z sensitivity curves can be measured with a reasonable accuracy. However, the overall luminosity curve (which in fact is a weighted sum of these three curves) is subjective, since it involves asking a test person whether two light sources have the same brightness, even if they are in completely different colors. Along the same lines, the relative magnitudes of the X, Y, and Z curves are arbitrary. One could as well define a valid color space with an X sensitivity curve that has twice the amplitude. This new color space would have a different shape. The sensitivity curves in the CIE 1931 and 1964 xyz color space are scaled to have equal areas under the curves.

The figure on the left shows the related chromaticity diagram with wavelengths in nanometers.

In this diagram, x and y are related to the X, Y, and Z tristimulus values under Human tristimulus color space above according to: Color is an important part of the visual arts. ...

x = X/(X + Y + Z),

y = Y/(X + Y + Z).

Mathematically, x and y are projective coordinates and the colors of the chromaticity diagram occupy a region of the real projective plane. Because the CIE sensitivity curves have equal areas under the curves, light with a flat energy spectrum corresponds to the point (x,y) = (0.333,0.333). Projective plane - Wikipedia, the free encyclopedia /**/ @import /skins-1. ...

The values for X, Y, and Z are obtained by integrating the product of the spectrum of a light beam and the published color-matching functions. Blue and red wavelengths do not contribute strongly to the luminosity, which is illustrated by the following example:

For someone with normal color vision, green is brighter than red, which is brighter than blue. Even though the pure blue appears to be very dark and hardly discernible from black when observed from a distance, blue has a strong coloring power when mixed with green or red.

With some forms of "red-green color blindness" the green is very slightly brighter than the blue, and the red is so dark it can barely be made out. Red traffic lights in bright daylight appear broken (no light). The green traffic light appears dirty white and hard to distinguish from night street lights. Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ...

The CIE-xyz color space is a prism, as opposed to the cone-shaped tristimulus space above. In the two-dimensional xy representation, all possible additive mixtures of two colors A and B form a straight line. However, the additive mixture of two colors does generally not lie on the mid-point of this line. In geometry, an n-sided prism is a polyhedron made of an n-sided polygonal base, a translated copy, and n faces joining corresponding sides. ... This article is about the geometric object, for other uses see Cone. ...

RGB color model

Main article: RGB color model

Media that transmit light (such as television) use additive color mixing with primary colors of red, green, and blue, each of which stimulates one of the three types of the eye's color receptors with as little stimulation as possible of the other two. This is called "RGB" color space—see also RGB color model. Mixtures of light of these primary colors cover a large part of the human color space and thus produce a large part of human color experiences. This is why color television sets or color computer monitors need only produce mixtures of red, green and blue light. See Additive color. RGB redirects here. ... Image File history File links RGBCube_b. ... Image File history File links RGBCube_b. ... Additive color mixing: adding red to green yields yellow; adding yellow to blue yields white. ... This article is about colors. ... For other uses, see Red (disambiguation). ... For other uses, see Green (disambiguation). ... This article is about the colour. ... REDIRECT RGB color model ... RGB redirects here. ... Additive color mixing: adding red to green yields yellow; adding yellow to blue yields white. ...

Other primary colors could in principle be used, but with red, green and blue the largest portion of the human color space can be captured. Unfortunately there is no exact consensus as to what loci in the chromaticity diagram the red, green, and blue colors should have, so the same RGB values can give rise to slightly different colors on different screens. The International Commission on Illumination (usually known as the CIE for its French-language name Commission Internationale de lEclairage) is the international authority on light, illumination, colour, and colour spaces. ...

HSV and HSL representations

Main article: HSL color space

Recognizing that the geometry of the RGB model is poorly aligned with the color-making attributes recognized by human vision, computer graphics researchers developed two alternate representations of RGB, HSV and HSL (hue, saturation, value and hue, saturation, lightness), in the late 1970s, formally defined and described in Alvy Ray Smith’s 1978 paper “Color Gamut Transform Pairs”. HSV and HSL improve on the color cube representation of RGB by arranging colors of each hue in a radial slice, around a central axis of neutral colors which ranges from black at the bottom to white at the top. The fully saturated colors of each hue then lie in a circle, a color wheel. The HSL color space, also called HLS or HSI, stands for Hue, Saturation, Lightness (also Luminance or Luminosity) / Intensity. ... HSV color space visualization; HSV as a conical object. ... HSV color space visualization; HSV as a conical object. ... Image File history File links Download high resolution version (1905x2025, 1193 KB)color cones Hello I contributed with this image to wikipedia. ... Image File history File links Download high resolution version (1905x2025, 1193 KB)color cones Hello I contributed with this image to wikipedia. ... Alvy Ray Smith III (born 8 September 1943) is a noted pioneer in computer graphics. ... This article does not cite any references or sources. ...

HSV models itself on paint mixture, with its saturation and value dimensions resembling mixtures of a brightly colored paint with, respectively, white and black. HSL tries to resemble more perceptual color models such as NCS or Munsell. It places the fully saturated colors in a circle of lightness ½, so that lightness 1 always implies white, and lightness 0 always implies black.

HSV and HSL are both widely used in computer graphics, particularly as color pickers in image editing software. The mathematical transformation from RGB to HSV or HSL could be computed in real time, even on computers of the 1970s, and there is an easy-to-understand mapping between colors in either of these spaces and their manifestation on a physical RGB device.
A screenshot of the Yahoo Color Picker. ... In computer graphics, graphics software or image editing software is a program or collection of programs that enable a person to manipulate visual images on a computer. ...

CMYK color model

Main article: CMYK color model

A comparison of RGB and CMYK color models.

It is possible to achieve a large range of colors seen by humans by combining cyan, magenta, and yellow transparent dyes/inks on a white substrate. These are the subtractive primary colors. Often a fourth black is added to improve reproduction of some dark colors. This is called "CMY" or "CMYK" color space. Cyan, magenta, yellow, and key (black). ... Image File history File links RGB_CMYK_4. ... Image File history File links RGB_CMYK_4. ... Cyan (from Greek κυανοs, meaning blue) may be used as the name of any of a number of a range of colors in the blue/green part of the spectrum. ... Magenta is a color made up of equal parts of red and blue light. ... A yellow Tulip. ... Subtractive color mixing An 1877 color photo by Louis Ducos du Hauron, a French pioneer of color photography. ... This article is about colors. ... This article is about the color. ... Cyan, magenta, yellow, and key (black) CMYK (or sometimes YMCK) is a subtractive color model used in color printing. ...

The cyan ink will reflect all but the red light, the yellow ink will reflect all but the blue light and the magenta ink will reflect all but the green light. This is because cyan light is an equal mixture of green and blue, yellow is an equal mixture of red and green, and magenta light is an equal mixture of red and blue.

Color systems

There are various types of color systems that classify color and analyse their effects. The American Munsell color system devised by Albert H. Munsell is a famous classification that organises various colors into a color solid based on hue, saturation and value. Other important color systems include the Swedish Natural Color System (NCS) from the Scandinavian Color Institute, the Optical Society of America's Uniform Color Space (OSA-UCS), and the Hungarian Coloroid system developed by Antal Nemcsics from the Budapest University of Technology and Economics. Of those, the NCS is based on the opponent-process color model, while the Munsell, the OSA-UCS and the Coloroid attempt to model color uniformity. The American Pantone and the German RAL commercial color-matching systems differ from the previous ones in that their color spaces are not based on an underlying color model. Munsell Color Wheel In colorimetry, the Munsell color system is a color system that specifies colors based on three color dimensions. ... Albert Henry Munsell was a painter and a teacher of art. ... The Natural Color System (NCS) is a perceptual color model published by the Scandinavian Colour Institute of Stockholm, Sweden. ... The Optical Society of America (OSA) is a scientific society dedicated to advancing the study of light—optics and photonics—in theory and application, by means of worldwide research, scientific publishing, conferences and exhibitions, partnership with industry, and the education of new generations of scientists. ... The Budapest University of Technology and Economics (in Hungarian, Budapesti Műszaki és Gazdaságtudományi Egyetem or in short Műegyetem) is the most significant University of Technology in Hungary. ... Opponent colors based on experiment. ... For the record label, see Pantone Music. ... RAL is a color space system developed in 1927 by Reichsausschuß für Lieferbedingungen (und Gütesicherung)—German for Commission for Delivery Terms and Quality Assurance, nowadays called . ...

Other uses of "color model"

Models of mechanism of color vision

We also use "color model" to indicate a model or mechanism of color vision for explaining how color signals are processed from visual cones to ganglion cells. For simplicity, we call these models color mechanism models. The classical color mechanism models are Young-Helmholtz's trichromatic model and Hering's opponent-process model. Though these two theories were initially thought to be at odds, it later came to be understood that the mechanisms responsible for color opponency receive signals from the three types of cones and process them at a more complex level.^[1] Thomas Young, English scientist Thomas Young (June 13, 1773-May 10, 1829) was an English polymath, contributing to the scientific understanding of vision, light, solid mechanics, energy, physiology, and Egyptology. ... Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ... The Young-Helmholtz theory (proposed in the 19th century by Thomas Young and Hermann von Helmholtz) is a theory of trichromatic colour vision - the manner in which the photoreceptors in the eyes of humans and other primates worked to enable color vision. ... Ewald Hering (full name Karl Ewald Konstantin Hering) (August 5, 1834 - January 26, 1918) was a German physiologist who did much research into color vision and spatial perception. ... Opponent colors based on experiment. ...

Vertebrate evolution of color vision

Vertebrate animals were primitively tetrachromatic. They possessed short, mid, long wavelength cones, and ultraviolet sensitive cones. Today, fish, reptiles and birds are all tetrachromatic. Placental mammals lost both the short and mid wavelength cones. Thus, most mammals do not have complex color vision but they are sensitive to ultraviolet light. Human trichromatic color vision is a recent evolutionary novelty that first evolved in the common ancestor of the Old World Primates. Our trichromatic color vision evolved by duplication of the long wavelength sensitive opsin, found on the X chromosome. One of these copies evolved to be sensitive to green light and constitutes our mid wavelength opsin. At the same time, our short wavelength opsin evolved from the ultraviolet opsin of our vertebrate and mammalian ancestors. This article does not cite any references or sources. ... This article is about evolution in biology. ... A tetrachromat is an organism for which the perceptual effect of any arbitrarily chosen light from its visible spectrum can be matched by a mixture of no more than four different pure spectral lights. ... A rhodopsin molecule in the cell membrane. ... A rhodopsin molecule in the cell membrane. ...

Human red-green color blindness occurs because the two copies of the red and green opsin genes remain in close proximity on the X chromosome. Because of frequent recombination during meiosis, these gene pairs can get easily rearranged, creating versions of the genes that do not have distinct spectral sensitivities.

References

1. ^ Kandel ER, Schwartz JH and Jessell TM, 2000. Principles of Neural Science, 4th ed., McGraw-Hill, New York. pp. 577–80.

See also

• Color space
• Color