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Encyclopedia > Color
Color is an important part of the visual arts.

Color (or colour, see spelling differences) is the visual perceptual property corresponding in humans to the categories called red, yellow, white, etc. Color derives from the spectrum of light (distribution of light energy versus wavelength) interacting in the eye with the spectral sensitivities of the light receptors. Color categories and physical specifications of color are also associated with objects, materials, light sources, etc., based on their physical properties such as light absorption, reflection, or emission spectra. Image File history File links Download high-resolution version (469x768, 91 KB) GNU image from German language Wikipedia at [1]. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Image File history File links Download high-resolution version (469x768, 91 KB) GNU image from German language Wikipedia at [1]. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1. ... Many times, the term art is used to refer to the visual arts. ... American and British English spelling differences are one aspect of American and British English differences. ... This does not cite any references or sources. ... Human beings are defined variously in biological, spiritual, and cultural terms, or in combinations thereof. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Photoreceptor cells are contained in the retina and are responsible for transducing, or converting, light into signals that can be ultimately transmitted to the brain via the optic nerve. ...


Typically, only features of the composition of light that are detectable by humans (wavelength spectrum from 400 nm to 700 nm, roughly) are included, thereby objectively relating the psychological phenomenon of color to its physical specification. Because perception of color stems from the varying sensitivity of different types of cone cells in the retina to different parts of the spectrum, colors may be defined and quantified by the degree to which they stimulate these cells. These physical or physiological quantifications of color, however, do not fully explain the psychophysical perception of color appearance. This article or section does not cite any references or sources. ... Psychology (ancient Greek: psyche = soul and logos = word) is the study of mind, thought, and behaviour. ... Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the branch of science concerned with the fundamental laws of the universe. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina which only function in relatively bright light. ... Human eye cross-sectional view. ... Physiology (in Greek physis = nature and logos = word) is the study of the mechanical, physical, and biochemical functions of living organisms. ... Psychophysics is the branch of psychology dealing with the relationship between physical stimuli and their perception. ...


The science of color is sometimes called chromatics. It includes the perception of color by the human eye and brain, the origin of color in materials, color theory in art, and the physics of electromagnetic radiation in the visible range (that is, what we commonly refer to simply as light). In the arts of painting, graphic design, and photography, color theory is a body of practical guidance to color mixing and the visual impact of specific color combinations. ... The Bath, a painting by Mary Cassatt (1844-1926). ... Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the branch of science concerned with the fundamental laws of the universe. ... It has been suggested that this article or section be merged with light. ...

Contents

Physics of color

The colors of the visible light spectrum
color wavelength interval frequency interval
red ~ 625–740 nm ~ 480–405 THz
orange ~ 590–625 nm ~ 510–480 THz
yellow ~ 565–590 nm ~ 530–510 THz
green ~ 500–565 nm ~ 600–530 THz
cyan ~ 485–500 nm ~ 620–600 THz
blue ~ 450–485 nm ~ 670–620 THz
violet ~ 380–450 nm ~ 790–670 THz
Continuous optical spectrum. Designed for monitors with gamma 1.5.
Computer "spectrum". The narrow red, green and blue bars below the main bar show the relative intensities of the three primary colors mixed to make the color directly above.
Computer "spectrum". The narrow red, green and blue bars below the main bar show the relative intensities of the three primary colors mixed to make the color directly above.
Color, wavelength, frequency and energy of light
Color lambda ,!/nm nu ,!/1014 Hz nu_b ,!/104 cm−1 E ,!/eV E ,!/kJ mol−1
Infrared >1000 <3.00 <1.00 <1.24 <120
Red 700 4.28 1.43 1.77 171
Orange 620 4.84 1.61 2.00 193
Yellow 580 5.17 1.72 2.14 206
Green 530 5.66 1.89 2.34 226
Blue 470 6.38 2.13 2.64 254
Violet 420 7.14 2.38 2.95 285
Near ultraviolet 300 10.0 3.33 4.15 400
Far ultraviolet <200 >15.0 >5.00 >6.20 >598

Electromagnetic radiation is characterized by its wavelength (or frequency) and its intensity. When the wavelength is within the visible spectrum (the range of wavelengths humans can perceive, approximately from 380 nm to 740 nm), it is known as "visible light." Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 625–750 nm. ... See also Orange (disambiguation) for other meanings of the word. ... A yellow Tulip. ... Mossy, green fountain in Wattens, Austria. ... 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. ... YOU SUCK!!!!! ... Violet (named after the flower violet) is used in two senses: first, referring to the color of light at the short-wavelength end of the visible spectrum, approximately 380–420 nanometres (this is a spectral color). ... Image File history File links Spectrum441pxWithnm. ... Gamma correction is the name of an internal adjustment made in the rendering of images through photography, television, and computer imaging. ... Image File history File links Computer_color_spectrum. ... Image File history File links Computer_color_spectrum. ... It has been suggested that this article or section be merged with light. ... The wavelength is the distance between repeating units of a wave pattern. ... FreQuency is a music video game developed by Harmonix and published by SCEI. It was released in November 2001. ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ...


Most light sources emit light at many different wavelengths; a source's spectrum is a distribution giving its intensity at each wavelength. Although the spectrum of light arriving at the eye from a given direction determines the color sensation in that direction, there are many more possible spectral combinations than color sensations. In fact, one may formally define a color as a class of spectra that give rise to the same color sensation, although such classes would vary widely among different species, and to a lesser extent among individuals within the same species. In each such class the members are called metamers of the color in question. It has been suggested that this article or section be merged with Sensation and perception psychology. ... Metamerism is a psychophysical phenomenon commonly defined as the situation when two samples match in color under one condition, but fail to match under another condition. ...


Spectral colors

The familiar colors of the rainbow in the spectrum – named for the Latin word for appearance or apparition by Isaac Newton in 1671 – include all those colors that can be produced by visible light of a single wavelength only, the pure spectral or monochromatic colors. The table at right shows approximate frequencies (in terahertz) and wavelengths (in nanometers) for various pure spectral colors. The wavelengths are measured in vacuum (see refraction). Full featured double rainbow in Wrangell-St. ... The visible spectrum is the portion of the optical spectrum (light or electromagnetic spectrum) that is visible to the human eye. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Sir Isaac Newton, (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist, regarded by many as the greatest figure in the history of science. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... The hertz (symbol: Hz) is the SI unit of frequency. ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ... Look up Vacuum in Wiktionary, the free dictionary. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ...


The color table should not be interpreted as a definitive list – the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors is a matter of culture, taste, and language. A common list identifies six main bands: red, orange, yellow, green, blue, and violet. Newton's conception included a seventh color, indigo, between blue and violet – but most people do not distinguish it, and most color scientists do not recognize it as a separate color; it is sometimes designated as wavelengths of 420–440 nm. The chart shown here, however, does identify a seventh main color band: cyan, located between green and blue. In most modern usages of the word spectrum, there is a unifying theme of between extremes at either end. ... Indigo (or spectral indigo) is the color on the spectrum between 440 and 420 nanometres in wavelength, placing it between blue and violet. ... 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. ...


The intensity of a spectral color may alter its perception considerably; for example, a low-intensity orange-yellow is brown, and a low-intensity yellow-green is olive-green. Brown, when used as a general term, is a color which is a dark orange, red or rose, of very low intensity. ...


As discussed in the section on color vision, a light source need not actually be of one single wavelength to be perceived as a pure spectral color.


For discussion of non-spectral colors, see below. Color is an important part of the visual arts. ...


Color of objects

The orange disk and the brown disk have exactly the same objective color, and are in identical gray surrounds; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see same color illusion.
The orange disk and the brown disk have exactly the same objective color, and are in identical gray surrounds; based on context differences, humans perceive the squares as having different reflectances, and may interpret the colors as different color categories; see same color illusion.

The color of an object depends both on physics and on perception. Physically, surfaces can be said to have the color of the light reflecting off them, which depends on the spectrum of the incident illumination and on the reflectance spectrum of the surface, as well as potentially on the lighting and viewing angles. However, a viewer's perception of the object color depends not only on the reflected light spectrum, but also on a host of contextual cues, such that an object's color tends to be perceived as relatively constant, that is, relatively independent of the lighting spectrum, viewing angle, etc. This effect is known as color constancy. Image File history File links This is a lossless scalable vector image. ... Image File history File links This is a lossless scalable vector image. ... Squares A and B are the same color. ... Color constancy is an example of subjective constancy and a feature of the human color-perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. ...


Some generalizations of the physics can be drawn, neglecting perceptual effects for now:

  • Light arriving at an opaque surface is either reflected "specularly" (that is, in the manner of a mirror), scattered (that is, reflected with diffuse scattering), or absorbed – or some combination of these.
  • Opaque objects that do not reflect specularly (which tend to have rough surfaces) have their color determined by which wavelengths of light they scatter more and which they scatter less (with the light that is not scattered being absorbed). If objects scatter all wavelengths, they appear white. If they absorb all wavelengths, they appear black.
  • Opaque objects that specularly reflect light of different wavelengths with different efficiencies look like mirrors tinted with colors determined by those differences. An object that reflects some fraction of impinging light and absorbs the rest may look black but also be faintly reflective; examples are black objects coated with layers of enamel or lacquer.
  • Objects that transmit light are either translucent (scattering the transmitted light) or transparent (not scattering the transmitted light). If they also absorb (or reflect) light of varying wavelengths differentially, they appear tinted with a color determined by the nature of that absorption (or that reflectance).
  • Objects may emit light that they generate themselves, rather than merely reflecting or transmitting light. They may do so because of their elevated temperature (they are then said to be incandescent), as a result of certain chemical reactions (a phenomenon called chemoluminescence), or for other reasons (see the articles Phosphorescence and List of light sources).
  • Objects may absorb light and then as a consequence emit light that has different properties. They are then called fluorescent (if light is emitted only while light is absorbed) or phosphorescent (if light is emitted even after light ceases to be absorbed; this term is also sometimes loosely applied to light emitted due to chemical reactions).

For further treatment of the color of objects, see structural color, below. The term reflection (also spelt reflexion) can refer to several different concepts: In mathematics, reflection is the transformation of a space. ... In ordinary English, to scatter is to distribute randomly. ... In physics, absorption is the process by which the energy of a photon is taken up by another entity, for example, by an atom whose valence electrons make a transition between two electronic energy levels. ... Molten glassy material glows orange with incandescence in a vitrification experiment. ... Lightsticks Chemoluminescence (sometimes chemiluminescence) is the emission of light (luminescence) as the result of a chemical reaction. ... Phosphorescent powder under visible light, ultraviolet light, and total darkness. ... A Standard Household Light bulb This page is a list of sources of light. ... Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ...


To summarize, the color of an object is a complex result of its surface properties, its transmission properties, and its emission properties, all of which factors contribute to the mix of wavelengths in the light leaving the surface of the object. The perceived color is then further conditioned by the nature of the ambient illumination, and by the color properties of other objects nearby, via the effect known as color constancy and via other characteristics of the perceiving eye and brain. Color constancy is an example of subjective constancy and a feature of the human color-perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. ...


Color perception

Normalized typical human cone responses (and the rod response) to monochromatic spectral stimuli
Normalized typical human cone responses (and the rod response) to monochromatic spectral stimuli

Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ... Spectral absorption curves of the short (S), medium (M) and long (L) wavelength pigments in human cone and rod (R) cells. ...

Development of theories of color vision

Main article: Color theory

Although Aristotle and other ancient scientists had already written on the nature of light and color vision, it was not until Newton that light was identified as the source of the color sensation. In 1810, Goethe published his comprehensive Theory of Colors. In 1801 Thomas Young proposed his trichromatic theory, based on the observation that any color could be matched with a combination of three lights. This theory was later refined by James Clerk Maxwell and Hermann von Helmholtz. As Helmholtz puts it, "the principles of Newton's law of mixture were experimentally confirmed by Maxwell in 1856. Young's theory of color sensations, like so much else that this marvellous investigator achieved in advance of his time, remained unnoticed until Maxwell directed attention to it."[1] In the arts of painting, graphic design, and photography, color theory is a body of practical guidance to color mixing and the visual impact of specific color combinations. ... Aristotle (Greek: AristotélÄ“s) (384 BC – March 7, 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ... 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. ... Sir Isaac Newton, (4 January 1643 – 31 March 1727) [ OS: 25 December 1642 – 20 March 1727][1] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist, regarded by many as the greatest figure in the history of science. ...  , IPA: , (28 August 1749 – 22 March 1832), commonly known as Goethe, was a German poet, novelist, theorist, and scientist who is considered one of the giants of the literary world. ... Theory of Colours (Zur Farbenlehre in German) was a work published by Johann Wolfgang von Goethe in 1810. ... Thomas Young, English scientist // Young belonged to a Quaker family of Milverton, Somerset, where he was born in 1773, the youngest of ten children. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Trichromatic color vision is the ability of humans and some other animals to see different colors, mediated by interactions among three types of color-sensing cone cells. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist. ... Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ...


At the same time as Helmholtz, Ewald Hering developed the opponent process theory of color, noting that color blindness and afterimages typically come in opponent pairs (red-green, blue-yellow, and black-white). Ultimately these two theories were synthesized in 1957 by Hurvich and Jameson, who showed that retinal processing corresponds to the trichromatic theory, while processing at the level of the lateral geniculate nucleus corresponds to the opponent theory.[2] Ewald Hering (August 5, 1834 - January 26, 1918) was a German physiologist who did much research into color vision and spatial perception. ... Opponent colours based on experiment. ... Grays FIG. 719– Hind- and mid-brains; postero-lateral view. ...


In 1931, an international group of experts known as the Commission Internationale d'Eclairage (CIE) developed a mathematical color model, which mapped out the space of observable colors and assigned a set of three numbers to each. 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. ...


Color in the eye

Main article: Color vision

The ability of the human eye to distinguish colors is based upon the varying sensitivity of different cells in the retina to light of different wavelengths. The retina contains three types of color receptor cells, or cones. One type, relatively distinct from the other two, is most responsive to light that we perceive as violet, with wavelengths around 420 nm. (Cones of this type are sometimes called short-wavelength cones, S cones, or, misleadingly, blue cones.) The other two types are closely related genetically and chemically. One of them (sometimes called long-wavelength cones, L cones, or, misleadingly, red cones) is most sensitive to light we perceive as yellowish-green, with wavelengths around 564 nm; the other type (sometimes called middle-wavelength cones, M cones, or misleadingly, green cones) is most sensitive to light perceived as green, with wavelengths around 534 nm. 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. ... Eyes are organs of vision that detect light. ... Human eye cross-sectional view. ... Normalised absorption spectra of human cone (S,M,L) and rod (R) cells Cone cells, or cones, are cells in the retina of the eye which only function in relatively bright light. ... NM may stand for: National Master, a chess title Nautical mile, a unit of length used for maritime and aviation purposes Neal Morse, an American multi-instrumentalist Network marketing, a business model that combines direct marketing with franchising Neurofiber mitosis, a nerve disease, sometimes confused with neurofibromatosis New Mexico, in...


Light, no matter how complex its composition of wavelengths, is reduced to three color components by the eye. For each location in the visual field, the three types of cones yield three signals based on the extent to which each is stimulated. These values are sometimes called tristimulus values.


The response curve as a function of wavelength for each type of cone is illustrated above. Because the curves overlap, some tristimulus values do not occur for any incoming light combination. For example, it is not possible to stimulate only the mid-wavelength/"green" cones; the other cones will inevitably be stimulated to some degree at the same time. The set of all possible tristimulus values determines the human color space. It has been estimated that humans can distinguish roughly 10 million different colors.[citation needed]


The other type of light-sensitive cell in the eye, the rod, has a different response curve. In normal situations, when light is bright enough to strongly stimulate the cones, rods play virtually no role in vision at all.[3] On the other hand, in dim light, the cones are understimulated leaving only the signal from the rods, resulting in a monochromatic response. (Furthermore, the rods are barely sensitive to light in the "red" range.) In certain conditions of intermediate illumination, the rod response and a weak cone response can together result in color discriminations not accounted for by cone responses alone. Normalised absoption spectra of human rod (R) and cone (S,M,L) cells. ...


Color in the brain

Main article: Color vision
The visual dorsal stream (green) and ventral stream (purple) are shown. The ventral stream is responsible for color perception.
The visual dorsal stream (green) and ventral stream (purple) are shown. The ventral stream is responsible for color perception.

While the mechanisms of color vision at the level of the retina are well-described in terms of tristimulus values (see above), color processing after that point is organized differently. A dominant theory of color vision proposes that color information is transmitted out of the eye by three opponent processes, or opponent channels, each constructed from the raw output of the cones: a red-green channel, a blue-yellow channel and a black-white "luminance" channel. This theory has been supported by neurobiology, and accounts for the structure of our subjective color experience. Specifically, it explains why we cannot perceive a "reddish green" or "yellowish blue," and it predicts the color wheel: it is the collection of colors for which at least one of the two color channels measures a value at one of its extremes. 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. ... Image File history File links Ventral-dorsal_streams. ... Image File history File links Ventral-dorsal_streams. ... The dorsal stream is a pathway for visual information which flows through the visual cortex, the part of the brain which provides visual processing. ... The primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. ... Opponent processes are observable in neuro impulses (Garbor wavelets), simmilar to qualia in philosophy. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ...


The exact nature of color perception beyond the processing already described, and indeed the status of color as a feature of the perceived world or rather as a feature of our perception of the world, is a matter of complex and continuing philosophical dispute (see qualia). Redness is the canonical quale. ...


Nonstandard color perception

Color deficiency

If one or more types of a person's color-sensing cones are missing or less responsive than normal to incoming light, that person can distinguish fewer colors and is said to be color deficient or color blind (though this latter term can be misleading; almost all color deficient individuals can distinguish at least some colors). Some kinds of color deficiency are caused by anomalies in the number or nature of cones in the retina. Others (like central or cortical achromatopsia) are caused by neural anomalies in those parts of the brain where visual processing takes place. Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ...


Tetrachromacy

While most humans are trichromatic (having three types of color receptors), many animals, known as tetrachromats, have four types. These include some species of spiders, most marsupials, birds, reptiles, and many species of fish. Other species are sensitive to only two axes of color or do not perceive color at all; these are called dichromats and monochromats respectively. A distinction is made between retinal tetrachromacy (having four pigments in cone cells in the retina, compared to three in trichromats) and functional tetrachromacy (having the ability to make enhanced color discriminations based on that retinal difference). As many as a half of all women, but only a small percentage of men, are retinal tetrachromats. The phenomenon arises when an individual receives two slightly different copies of the gene for either the medium- or long-wavelength cones (which are carried on the x-chromosome). For some of these retinal tetrachromats, color discriminations are enhanced, making them functional tetrachromats.[4] 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. ... Families Suborder Mesothelae     Liphistiidae (primitive burrowing spiders) Suborder Mygalomorphae     Atypidae (atypical tarantula)     Antrodiaetidae (folding trapdoor spider)     Mecicobothriidae (dwarf tarantulas)     Hexathelidae (venomous funnel-web tarantula)     Dipluridae (funnel-web tarantula)     Cyrtaucheniidae (wafer trapdoor spider)     Ctenizidae (trapdoor spider)     Theraphosidae (tarantula) Suborder Araneomorphae     Hypochilidae (lampshade spider)     Filistatidae (crevice weaver)     Sicariidae (recluse spider)     Scytodidae (spitting... Orders Superorder Ameridelphia Didelphimorphia Paucituberculata Superorder Australidelphia Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Marsupials are mammals in which the female typically has a pouch (called the marsupium, from which the name Marsupial derives) in which it rears its young through early infancy. ... For other meanings of bird, see bird (disambiguation). ... Orders  Crocodilia - Crocodilians scary crocodiles. ... A giant grouper at the Georgia Aquarium Fish are aquatic vertebrates that are typically cold-blooded; covered with scales, and equipped with two sets of paired fins and several unpaired fins. ...


Synesthesia

In certain forms of synesthesia, perceiving letters and numbers (grapheme → color synesthesia) or hearing musical sounds (music → color synesthesia) will lead to the unusual additional experiences of seeing colors. Behavioral and functional neuroimaging experiments have demonstrated that these color experiences lead to changes in behavioral tasks and lead to increased activation of brain regions involved in color perception, thus demonstrating their reality, and similarity to real color percepts, albeit evoked through a non-standard route. Synesthesia (also spelled synæsthesia or synaesthesia, plural synesthesiae or synaesthesiae)—from the Ancient Greek (syn), meaning with, and (aisthÄ“sis), meaning sensation—is a neurological condition in which two or more bodily senses are coupled. ... How someone with grapheme → color synesthesia might perceive (not see) certain letters and numbers. ... Functional neuroimaging is the use of neuroimaging technology to measure an aspect of brain function, often with a view to understanding the relationship between activity in certain brain areas and specific mental functions. ...


Afterimages

After exposure to strong light in their sensitivity range, photoreceptors of a given type become desensitized. For a few seconds after the light ceases, they will continue to signal less strongly than they otherwise would. Colors observed during that period will appear to lack the color component detected by the desensitized photoreceptors. This effect is responsible for the phenomenon of afterimages, in which the eye may continue to see a bright figure after looking away from it, but in a complementary color. Complementary colors are pairs of colors that are in some way opposites of each other. ...


Afterimage effects have also been utilized by artists, including Vincent van Gogh. Vincent Willem van Gogh (Dutch pronunciation: ) (March 30, 1853 – July 29, 1890 ) was a Dutch Post-Impressionist artist. ...


Color constancy

There is an interesting phenomenon which occurs when an artist uses a limited color palette: the eye tends to compensate by seeing any grey or neutral color as the color which is missing from the color wheel. E.g.: in a limited palette consisting of red, yellow, black and white, a mixture of yellow and black will appear as a variety of green, a mixture of red and black will appear as a variety of purple, and pure grey will appear bluish. A palette, in computer graphics, is a designated subset of the total range of colours supported by a computer graphics system. ... Eyes are organs of vision that detect light. ...


The trichromatric theory discussed above is strictly true only if the whole scene seen by the eye is of one and the same color, which of course is unrealistic. In reality, the brain compares the various colors in a scene, in order to eliminate the effects of the illumination. If a scene is illuminated with one light, and then with another, as long as the difference between the light sources stays within a reasonable range, the colors of the scene will nevertheless appear constant to us. This was studied by Edwin Land in the 1970s and led to his retinex theory of color constancy. Edwin Herbert Land (May 7, 1909 &#8211; March 1, 1991) was an American scientist and inventor. ... Color constancy is an example of subjective constancy and a feature of the human color-perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. ...


Color naming

Main article: Color naming

Colors vary in several different ways, including hue (red vs. orange vs. blue), saturation, brightness, and gloss. Some color words are derived from the name of an object of that color, such as "orange" or "salmon", while others are abstract, like "red". This article does not cite its references or sources. ... An image with the hues cyclically shifted The hues in the image of this Painted Bunting are cyclically rotated with time. ... It has been suggested that this article or section be merged with Chromaticity. ... Brightness is an attribute of visual perception in which a source appears to emit a given amount of light. ... Gloss is an optical property, which is based on the interaction of light with physical characteristics of an object. ...


Different cultures have different terms for colors, and may also assign some color names to slightly different parts of the spectrum: for instance, the Chinese character 青 (rendered as qīng in Mandarin and ao in Japanese) has a meaning that covers both blue and green; blue and green are traditionally considered shades of "青." A color name is a linguistic label that humans attach to a color. ... 漢字 / 汉字 Chinese character in Hanzi, Kanji, Hanja, Hán Tá»±. Red in Simplified Chinese. ... Standard Mandarin – also known as Standard Chinese or Standard spoken Chinese – is the official Chinese spoken language used by the Peoples Republic of China, the Republic of China (Taiwan), and Singapore. ... Ao is a Japanese word including what Westerners would call, separately, blue and green. ... The English language makes a distinction between blue and green but some languages do not. ...


In the 1969 study Basic Color Terms: Their Universality and Evolution, Brent Berlin and Paul Kay describe a pattern in naming "basic" colors (like "red" but not "red-orange" or "dark red" or "blood red", which are "shades" of red). All languages that have two "basic" color names distinguish dark/cool colors from bright/warm colors. The next colors to be distinguished are usually red and then blue or green. All languages with six "basic" colors include black, white, red, green, blue and yellow. The pattern holds up to a set of twelve: black, grey, white, pink, red, orange, yellow, green, blue, purple, brown, and azure (distinct from blue in Russian and Italian but not English). Brent Berlin is an anthropologist. ... Paul Kay is a linguist. ... Categories: Stub | Colors ...


Associations

Individual colors have a variety of cultural associations such as national colors (in general described in individual color articles and color symbolism). The field of color psychology attempts to identify the effects of color on human emotion and activity. Chromotherapy is a form of alternative medicine attributed to various Eastern traditions. National colours are frequently part of a countrys set of national symbols. ... Color Symbolism describes the use of color as a symbol throughout cultures and religions. ... Color psychology is a field of study devoted to analyzing the effect of color on human behavior and feeling, distinct from phototherapy (the use of ultraviolet light to cure infantile jaundice). ... This does not cite its references or sources. ... Alternative medicine describes practices used in place of conventional medical treatments. ...


Health effects

When the color spectrum of artificial lighting is mismatched to that of sunlight, material health effects may arise including increased incidence of headache. This phenomenon is often coupled with adverse effects of over-illumination, since many of the same interior spaces that have color mismatch also have higher light intensity than desirable for the task being conducted in that space. Prism splitting light High Resolution Solar Spectrum Sunlight in the broad sense is the total spectrum of the electromagnetic radiation given off by the Sun. ... A headache is a condition of pain in the head; sometimes neck or upper back pain may also be interpreted as a headache. ... This cosmetics store has lighting levels over twice recommended levels and sufficient to trigger headaches and other health effects Over-illumination is the presence of lighting intensity (illuminance) beyond that required for a specified activity. ...


Measurement and reproduction of color

Relation to spectral colors

The CIE 1931 color space chromaticity diagram. The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. Note that the colors depicted depend on the color space of the device on which you are viewing the image, and therefore may not be a strictly accurate representation of the color at a particular position, and especially not for monochromatic colors.
The CIE 1931 color space chromaticity diagram. The outer curved boundary is the spectral (or monochromatic) locus, with wavelengths shown in nanometers. Note that the colors depicted depend on the color space of the device on which you are viewing the image, and therefore may not be a strictly accurate representation of the color at a particular position, and especially not for monochromatic colors.

Most light sources are mixtures of various wavelengths of light. However, many such sources can still have a spectral color insofar as the eye cannot distinguish them from monochromatic sources. For example, most computer displays reproduce the spectral color orange as a combination of red and green light; it appears orange because the red and green are mixed in the right proportions to allow the eye's red and green cones to respond the way they do to orange. Image File history File links Download high resolution version (1140x1260, 327 KB) CIE 1931 xy chromaticity diagram The colors for this diagram were generated using the RGB color space in Adobe photoshop. ... Image File history File links Download high resolution version (1140x1260, 327 KB) CIE 1931 xy chromaticity diagram The colors for this diagram were generated using the RGB color space in Adobe photoshop. ... 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 (e. ...


A useful concept in understanding the perceived color of a non-monochromatic light source is the dominant wavelength, which identifies the single wavelength of light which produces a sensation most similar to the light source. Dominant wavelength is roughly akin to hue. Dominant/complementary wavelength example on the CIE color space The x marks the color in question. ... An image with the hues cyclically shifted The hues in the image of this Painted Bunting are cyclically rotated with time. ...


Of course, there are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (mixtures of red and violet light, from opposite ends of the spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray and white) and colors such as pink, tan, and magenta. It has been suggested that this article or section be merged with Chromaticity. ... PinkIt can be described as a light red, but it is more bright, undersaturated red. ... Magenta is a color made up of equal parts of red and blue light. ...

A color photograph of a sunset
A color photograph of a sunset

Two different light spectra which have the same effect on the three color receptors in the human eye will be perceived as the same color. This is exemplified by the white light that is emitted by fluorescent lamps, which typically has a spectrum consisting of a few narrow bands, while daylight has a continuous spectrum. The human eye cannot tell the difference between such light spectra just by looking into the light source, although reflected colors from objects can look different. (This is often exploited e.g. to make fruit or tomatoes look more brightly red in shops.) Download high resolution version (1280x960, 153 KB)A dramatic sunset Taken by User:Fir0002 File links The following pages link to this file: Color Rayleigh scattering Sunset Sky Wikipedia:Featured picture candidates/Sunsets Wikipedia:Featured pictures candidates/April-2005 User:Fir0002/Fir0002 gallery Categories: GFDL images ... Download high resolution version (1280x960, 153 KB)A dramatic sunset Taken by User:Fir0002 File links The following pages link to this file: Color Rayleigh scattering Sunset Sky Wikipedia:Featured picture candidates/Sunsets Wikipedia:Featured pictures candidates/April-2005 User:Fir0002/Fir0002 gallery Categories: GFDL images ... For other uses, see Fruit (disambiguation). ... Binomial name Solanum lycopersicum L. Percentages are relative to US recommendations for adults. ...


Similarly, most human color perceptions can be generated by a mixture of three colors called primaries. This is used to reproduce color scenes in photography, printing, television and other media. There are a number of methods or color spaces for specifying a color in terms of three particular primary colors. Each method has its advantages and disadvantages depending on the particular application. 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 (e. ...


No mixture of colors, though, can produce a fully pure color perceived as completely identical to a spectral color, although one can get very close for the longer wavelengths, where the chromaticity diagram above has a nearly straight edge. For example, mixing green light (530 nm) and blue light (460 nm) produces cyan light that is slightly desaturated, because response of the red color receptor would be greater to the green and blue light in the mixture than it would be to a pure cyan light at 485 nm that has the same intensity as the mixture of blue and green. 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. ...


Because of this, and because the primaries in color printing systems generally are not pure themselves, the colors reproduced are never perfectly saturated colors, and so spectral colors cannot be matched exactly. However, natural scenes rarely contain fully saturated colors, thus such scenes can usually be approximated well by these systems. The range of colors that can be reproduced with a given color reproduction system is called the gamut. The CIE chromaticity diagram can be used to describe the gamut. Color printing is the reproduction of an image or text in color (as opposed to simpler black and white or monochrome printing). ... In computer graphics, the gamut, or color gamut (pronounced ), is a certain complete subset of colors. ... 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. ...


Another problem with color reproduction systems is connected with the acquisition devices, like cameras or scanners. The characteristics of the color sensors in the devices are often very far from the characteristics of the receptors in the human eye. In effect, acquisition of colors that have some special, often very "jagged," spectra caused for example by unusual lighting of the photographed scene can be relatively poor.


Species that have color receptors different from humans, e. g. birds that may have four receptors, can differentiate some colors that look the same to a human. In such cases, a color reproduction system 'tuned' to a human with normal color vision may give very inaccurate results for the other observers. “Aves” redirects here. ...


The next problem is different color response of different devices. For color information stored and transferred in a digital form, color management technique based on color profiles attached to color data and to devices with different color response helps to avoid deformations of the reproduced colors. The technique works only for colors in gamut of the particular devices, e.g. it can still happen that your monitor is not able to show you real color of your goldfish even if your camera can receive and store the color information properly and vice versa. Color management is a term used in computer environments which describes a controlled conversion between the colors of various color devices, such as scanners, digital cameras, monitors, TV screens, film printers, printers, offset presses, and corresponding media. ... Color management is a term used in computer environments which describes a controlled conversion between the colors of various color devices, such as scanners, digital cameras, monitors, TV screens, film printers, printers, offset presses, and corresponding media. ... In computer graphics, the gamut, or color gamut (pronounced ), is a certain complete subset of colors. ...


Pigments and reflective media

Main article: Pigment

Pigments are chemicals that selectively absorb and reflect different spectra of light. When a surface is painted with a pigment, light hitting the surface is reflected, minus some wavelengths. This subtraction of wavelengths produces the appearance of different colors. Most paints are a blend of several chemical pigments, intended to produce a reflection of a given color. Natural Ultramarine pigment in powdered form. ...


Pigment manufacturers assume the source light will be white, or of roughly equal intensity across the spectrum. If the light isn't a pure white source (as in the case of nearly all forms of artificial lighting), the resulting spectrum will appear a slightly different color. Red paint, viewed under blue light, may appear black. Red paint is red because it reflects only the red components of the spectrum. Blue light, containing none of these, will create no reflection from red paint, creating the appearance of black. This article is about the color. ... Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 625–750 nm. ... YOU SUCK!!!!! ... Black cat, thought by some to cause bad luck Black is the shade of objects that do not reflect light in any part of the visible spectrum. ...


Structural color

Structural colors are colors caused by interference effects rather than by pigments. Color effects are produced when a material is scored with fine parallel lines, formed of a thin layer or of two or more parallel thin layers, or otherwise composed of microstructures on the scale of the color's wavelength. If the microstructures are spaced randomly, light of shorter wavelengths will be scattered preferentially to produce Tyndall effect colors: the blue of the sky, the aerogel of opals, and the blue of human irises. If the microstructures are aligned in arrays, for example the array of pits in a CD, they behave as a diffraction grating: the grating reflects different wavelengths in different directions due to interference phenomena, separating mixed "white" light into light of different wavelengths. If the structure is one or more thin layers then it will reflect some wavelengths and transmit others, depending on the layers' thickness. The wavelength is the distance between repeating units of a wave pattern. ... Shot of sunbeams breaking through nebula bank The term Tyndall effect is usually applied to the effect of light scattering on particles in colloid systems, such as suspensions or emulsions. ... A 2. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ...


Structural color is responsible for the blues and greens of the feathers of many birds (the blue jay, for example), as well as certain butterfly wings and beetle shells. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, soap bubbles, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. Peter Vukusic[citation needed] has carried out research in butterfly wings and beetle shells using electron micrography, and has since helped develop a range of "photonic" cosmetics using structural color. Peacock re-directs here; for alternate uses see Peacock (disambiguation). ... Soap bubbles can easily merge A soap bubble A soap bubble is a very thin film of soap water that forms a hollow spherical shape with an iridescent surface. ... A piece of nacre Nacre, also known as mother of pearl, is an organic mixture of calcium carbonate (CaCO3) in the form of platy crystals of aragonite and conchiolin (a scleroprotein). ... This article does not cite its references or sources. ... This article is in need of attention from an expert on the subject. ...


Structural color is studied in the field of thin-film optics. A layman's term that describes particularly the most ordered structural colors is iridescence. Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ... The iridescence of the Blue Morpho butterfly wings. ...


Additional terms

  • Hue: the color's direction from white, for example in the CIE chromaticity diagram.
  • Saturation: how "intense" or "concentrated" a color is; also known as chroma or purity.
  • Value: how light or dark a color is.
  • Tint: a color made lighter by adding white.
  • Shade: a color made darker by adding black.

An image with the hues cyclically shifted The hues in the image of this Painted Bunting are cyclically rotated with time. ... It has been suggested that this article or section be merged with Chromaticity. ... Value is how dark or how light something looks. ... In color theory, a tint is the mixture of a color with white, and a shade is the mixture of a color with black. ... In color theory, a tint is the mixture of a color with white, and a shade is the mixture of a color with black. ...

References

  1. ^ Hermann von Helmholtz, Physiological Optics – The Sensations of Vision, 1866, as translated in Sources of Color Science, David L. MacAdam, ed., Cambridge: MIT Press, 1970.
  2. ^ Palmer, S.E. (1999). Vision Science: Photons to Phenomenology. Cambridge, MA: MIT Press. ISBN 0-262-16183-4
  3. ^ "Under well-lit viewing conditions (photopic vision), cones...are highly active and rods are inactive." Hirakawa, K, and Parks, TW, Chromatic adaptation and the white-balance problem, [1]
  4. ^ Jameson, K. A., Highnote, S. M., & Wasserman, L. M. (2001). Richer color experience in observers with multiple photopigment opsin genes. Psychonomic Bulletin and Review, 8(2), 244-261.

See also

Metamerism is a psychophysical phenomenon commonly defined as the situation when two samples match in color under one condition, but fail to match under another condition. ... A chromophore is part (or moiety) of a molecule responsible for its color. ... This article does not cite its references or sources. ... Redness is the canonical quale. ... Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... Color temperature is a characteristic of visible light that has important applications in photography, videography, publishing and other fields. ... In the arts of painting, graphic design, and photography, color theory is a body of practical guidance to color mixing and the visual impact of specific color combinations. ... A color scheme is the choice of colors used in design for a range of media. ... Color psychology is a field of study devoted to analyzing the effect of color on human behavior and feeling, distinct from phototherapy (the use of ultraviolet light to cure infantile jaundice). ... Color Symbolism describes the use of color as a symbol throughout cultures and religions. ... Political parties Part of the Politics series Politics Portal This box:      A political party is a political organization that seeks to attain political power within a government, usually by participating in electoral campaigns. ... Political colours are colours used to represent a political stance, a political ideology, or &#8212; in a telling use of terminology &#8212; a position on the political spectrum. ... Synesthesia (also spelled synæsthesia or synaesthesia, plural synesthesiae or synaesthesiae)—from the Ancient Greek (syn), meaning with, and (aisthÄ“sis), meaning sensation—is a neurological condition in which two or more bodily senses are coupled. ... Theory of Colours (Zur Farbenlehre in German) was a work published by Johann Wolfgang von Goethe in 1810. ... 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 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. ... Thermochromics are temperature sensitive inks, developed in the 1970s, that temporarily change color with exposure to temperature. ... For a list of words with definitions, see the Heraldic tincture category of words in Wiktionary, the free dictionary In heraldry, tinctures are the colours used to blazon a coat of arms. ...

External links and sources

David John Chalmers (born April 20, 1966) is a philosopher in the area of philosophy of mind. ...


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