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

Color or colour is a sensation which (in humans) derives from the ability of the fine structure of the eye to distinguish three differently filtered analyses of a view. The perception of color is influenced by long-term history (nurture) of the observer and also by short-term effects such as the colors nearby. The term color is also used for the property of objects or light sources that can be distinguished by differences in the receptors of the eye. Photo by abdullah. From http://www. ... Photo by abdullah. From http://www. ... Many times, the term art is used to refer to the visual arts. ... 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. ... An eye is an organ that detects light. ...


The science of color is sometimes called chromatics. It includes the perception of color by the human eye, the origin of color in materials, color theory in art, and the physics of color in the electromagnetic spectrum. An eye is an organ that detects light. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ... Resources Great Museums in the World (Louvre, Metropolitan Museum, MoMA, Picasso …) CGFA: A Virtual Art Museum Art-Atlas. ... The electromagnetic spectrum encompasses all possible wavelengths of electromagnetic radiation. ...

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 ~ 440-485 nm ~ 680-620 THz
violet ~ 380-440 nm ~ 790-680 THz

Continuous optical spectrum
Image:Spectrum441pxWithnm.png
Designed for monitors with gamma 1.5. Red is a color at the lowest frequencies of light discernible by the human eye. ... See also Orange (disambiguation) for other meanings of the word. ... Yellow is the color of light whose wavelength is between 565 nm and 590 nm. ... Look up Green in Wiktionary, the free dictionary Green is a color seen commonly in nature. ... Cyan is a pure spectral color, but the same hue can also be generated by mixing equal amounts of green and blue light. ... For other uses, see Blue (disambiguation) Blue (from Old High German blao shining) is one of the three primary additive colors; blue light has the shortest wavelength range (about 420-490 nm) of the three primary colors. ... Violet (named after the flower violet) refers to any of a group of reddish blue or bluish purple colors. ... Attempt at true-colour spectrum, although LMS cone stimulus is probably out of proportion, wavelength in nanometres marked Explanation: this image was generated based on published data regarding the sensitivities of the cones in the human retina, and the typical colors and the gamma of the R, G, and B... A gamma characteristic is a power-law relationship that approximates the relationship between the encoded luminance in a television system and the actual desired image brightness. ...

Computer "spectrum"
Image:Computerspectrum.png
The bars below show the relative intensities of the three
colors mixed to make the color immediately above.
A view of the computer color spectrum, with compartive strengths of the colors. ...

Color, frequency, and energy of light.

Color /nm /1014 Hz /104 cm-1 /eV /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 a mixture of radiation of different wavelengths and intensities. When this radiation has a wavelength inside the human visibility range (approximately from 380 nm to 740 nm), it is called light. The light's spectrum records each wavelength's intensity. The full spectrum of the incoming radiation from an object determines the visual appearance of that object, including its perceived color. As we will see, there are many more spectra than color sensations; in fact one may formally define a color to be the whole class of spectra which give rise to the same color sensation, although any such definition would vary widely among different species and also somewhat among individuals intraspecifically. Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... The wavelength is the distance between repeating units of a wave pattern. ... A nanometre (American spelling: nanometer, symbol: nm) is 1. ...


A surface that diffusely reflects all wavelengths equally is perceived as white, while a dull black surface absorbs all wavelengths and does not reflect (for mirror reflection this is different: a proper mirror also reflects all wavelengths equally, but is not perceived as white, while shiny black objects do reflect). The reflection of sunlight on water Reflection is the abrupt change in direction of a wave front at an interface between two dissimilar media so that the wave front returns into the medium from which it originated. ... White is a color (more accurately it contains all the colors of the visible spectrum and is sometimes described as an achromatic color—black is the absence of color) that has high brightness but zero hue. ... Black is a color with several subtle differences in meaning. ... A mirror is a reflective surface that is smooth enough to form an image. ...


The familiar colors of the rainbow in the spectrum—named from the Latin word for appearance or apparition by Isaac Newton in 1671—contains all those colors that consist of visible light of a single wavelength only, the pure spectral or monochromatic colors. RAINBOW is an album by Ayumi Hamasaki. ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... Latin is the language originally spoken in the region around Rome called Latium. ... Sir Isaac Newton in Godfrey Knellers 1689 portrait Sir Isaac Newton (25 December 1642 – 20 March 1727 by the Julian calendar in use in England at the time; or 4 January 1643 – 31 March 1727 by the Gregorian calendar) was an English physicist, mathematician, astronomer, philosopher, and alchemist who... Events May 9 - Thomas Blood, disguised as a clergyman, attempts to steal the Crown Jewels from the Tower of London. ...


The frequencies are approximations and given in terahertz (THz). The wavelengths, valid in vacuum, are given in nanometers (nm). A list of other objects of similar size is available. The hertz (symbol Hz) is the SI unit of frequency. ... This article is about absence of matter. ... A nanometre (American spelling: nanometer, symbol: nm) is 1. ... To help compare different orders of magnitude this page lists lengths between 100 nm and 1 µm (10-7 and 10-6 m). ...


Important note

The color table should not be interpreted as a definite list—the pure spectral colors form a continuous spectrum, and how it is divided into distinct colors is a matter of taste and culture; for example, Isaac Newton identified the seven colors red, orange, yellow, green, blue, indigo, and violet, remembered by many school children using mnemonics such as Roy G. Biv, Richard Of York Gave Battle In Vain and VIBGYOR. (Newton chose 7 colors because he believed each color corresponded to a note of the major musical scale. It was discovered much later that color and musical pitch do both involve frequency spectra; but there is no deeper relationship.) Sir Isaac Newton in Godfrey Knellers 1689 portrait Sir Isaac Newton (25 December 1642 – 20 March 1727 by the Julian calendar in use in England at the time; or 4 January 1643 – 31 March 1727 by the Gregorian calendar) was an English physicist, mathematician, astronomer, philosopher, and alchemist who... This article is about the color. ... A mnemonic (pronounced in American English, in British English) is a memory aid. ...


Similarly, 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 is a color produced by mixing small intensities of red and green, orange and blue, or yellow and purple pigment. ...


Spectral versus non-spectral colors

Most light sources are not pure spectral sources; rather they are created from mixtures of various wavelengths and intensities of light. To the human eye, however, there is a wide class of mixed-spectrum light that is perceived the same as a pure spectral color. In the table above, for instance, when your computer screen is displaying the "orange" patch, it is not emitting pure light at a fixed wavelength of around 600 nm (which is in fact not a thing most computer screens are even able to do). Rather, it is emitting a mixture of about two parts red to one part green light. Were you to print this page on a color printer, the orange patch on the paper, when lit with white light, would reflect yet another, more continuous spectrum. We cannot see those differences (although many animals can), and the reason has to do with the pigments that make up our color vision cells (see below). A computer is a device or machine for making calculations or controlling operations that are expressible in numerical or logical terms. ...


A useful quantification of this property is the dominant wavelength, which matches a wavelength of spectral light to a non-spectral source that evokes the same color perception. Dominant wavelength is the formal background for the popular concept of hue. Dominant wavelength example on the CIE color space The x marks the color in question. ... For the city in Vietnam, see Hue (city). ...


In addition to the many light sources that can appear to be pure spectral colors but are actually mixtures, there are many color perceptions that by definition cannot be pure spectral colors due to desaturation or because they are purples (which do not appear in the Newtonian pure spectrum). Some examples of necessarily non-spectral colors are the achromatic colors (black, gray and white) and other colors such as pink, tan and magenta. See metamerism (color) for a basic intro to why color matching challenges exist. This article is about the color. ... Magenta is a color that is not a spectral color: that is to say, the hue cannot be generated by light of a single wavelength. ... Metamerism is a psychophysical phenomenon commonly defined incompletely as two samples which match when illuminated by a particular light source and then do not match when illuminated by a different light source. ...


Color in the wave equation

The wave equation describes the behavior of light and so we should be able to describe color spectra in terms of the mathematical properties of the solutions of the wave equation. However, to understand which particular color perception will arise from a particular physical spectrum requires knowledge of the specific retinal physiology of the observer. For completeness, we include a simple equation for light traveling in a vacuum: The wave equation is an important partial differential equation which generally describes all kinds of waves, such as sound waves, light waves and water waves. ...

utt=c2(uxx+uyy+uzz)

where the subscripts denote partial derivatives and c is the speed of light. If we fix (x,y,z) a point in space and look at the solution u(x,y,z,t) as a function of t, we obtain a signal. If we take the Fourier transform of this signal, we obtain a frequency decomposition as described above. Each frequency has an amplitude and phase. The frequency multiplied by Planck's constant h determines the energy of a photon of the relevant component. The square of the amplitude represents the intensity, which is the amount of energy transmitted per second through a unit area of a surface perpendicular to the light propagation. The phase information is much more mysterious because it is difficult to measure and observe. Humans cannot perceive phase effects of light except in special cases of interference (e.g. see thin-film optics) where phase effects lead to perceptible amplitude changes. Most light has randomly distributed phases, but lasers are more efficient when the photons all have the same phase. In mathematics, a partial derivative of a function of several variables is its derivative with respect to one of those variables with the others held constant. ... Signal processing is the processing, amplification and interpretation of signals. ... The Fourier transform, named after Jean Baptiste Joseph Fourier, is an integral transform that re-expresses a function in terms of sinusoidal basis functions, i. ... Plancks constant, denoted h, is a physical constant that is used to describe the sizes of quanta. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ... Thin-film optics is the branch of optics which deals with very thin structured layers of different materials. ...


Color vision

Though the exact status of color is a matter of current philosophical dispute, color is arguably a psychophysical phenomenon that exists only in our minds. (See Qualia, for some of that dispute.) A "red" apple does not give off "red light", and it is misleading to think of things that we see, or of light itself, as objectively colored at all. Rather, the apple simply absorbs light of various wavelengths shining on it to different degrees, in such a way that the unabsorbed light which it reflects is perceived as red. An apple is perceived to be red only because normal human color vision perceives light with different mixes of wavelengths differently—and we have language to describe that difference. This article is about the philosophical concept. ... Color vision is a psychophysical phenomenon that exists only in our minds. ...

In 1931, an international group of experts called the Commission Internationale d'Eclairage (CIE) developed a mathematical color model. The premise used by the CIE is that color is the combination of three things: a light source, an object, and an observer. The CIE tightly controlled each of these variables in an experiment that produced the measurements for the system. color is all in your brain pic not showing up??? File links The following pages link to this file: Color Categories: GFDL 1. ... C ras Iompair ireann (CI ) (English: Irish Transport Company, pronounced CHORUS UM-PAIR AIR-INN) is a statutory authority which is owned by the Irish Government, and since the enactment of Transport (Reorganisation of C ras Iompair ireann) Act, 1986 CI is the shareholding company of Bus Atha Cliath - Dublin...


Although Aristotle and other ancient scientists speculated on the nature of light and color vision, it was not until Newton that light was correctly identified as the source of the color sensation. Goethe studied the theory of colors, and in 1801 Thomas Young proposed his trichromatic theory which was later refined by Hermann von Helmholtz. That theory was confirmed in the 1960s and will be described below. Aristotle (sculpture) Aristotle (Greek: Αριστοτέλης AristotelÄ“s) (384 BC – March 7, 322 BC) was an ancient Greek philosopher. ... Prism splitting light Light is electromagnetic radiation with a wavelength that is visible to the eye, or in a more general sense, any electromagnetic radiation in the range from infrared to ultraviolet. ... Color vision is a psychophysical phenomenon that exists only in our minds. ... Sir Isaac Newton in Godfrey Knellers 1689 portrait Sir Isaac Newton (25 December 1642 – 20 March 1727 by the Julian calendar in use in England at the time; or 4 January 1643 – 31 March 1727 by the Gregorian calendar) was an English physicist, mathematician, astronomer, philosopher, and alchemist who... Johann Wolfgang von Goethe Johann Wolfgang von Goethe (pronounced [gø tÉ™]) (August 28, 1749 – March 22, 1832) was a German writer, politician, humanist, scientist, and literary philosopher. ... Thomas Young, English scientist Thomas Young (June 13, 1773 – May 10, 1829) was an English scientist and researcher. ... Hermann Ludwig Ferdinand von Helmholtz (August 31, 1821 – September 8, 1894) was a German physician and physicist. ...

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

The retina of the human eye contains three different 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, most commonly but quite misleadingly, blue cones). The other two types are closely related genetically, and in chemistry and response, and each type is most responsive to light that we perceive as green or greenish. One of these types (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 green cones) is most sensitive to light perceived as green, with wavelengths around 534 nm. The term "red cones" for the long-wavelength cones is deprecated as this type is actually maximally responsive to light we perceive as greenish, albeit longer wavelength light than that which maximally excites the mid-wavelength/"green" cones. 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. ... 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 which only function in relatively bright light. ... Nm or NM may stand for: nanometre (nm) nautical mile (nm) New Mexico newton-metre, properly written N m or N·m, see joule nm (UNIX), the UNIX command never mind or not much (nm), see Internet slang This is a disambiguation page — a navigational aid which lists other pages...


The sensitivity curves of the cones are roughly bell-shaped, and overlap considerably. The incoming signal spectrum is thus reduced by the eye to three values, sometimes called tristimulus values, representing the intensity of the response of each of the cone types.


Because of the overlap between the sensitivity ranges, some combinations of responses in the three types of cone are impossible no matter what light stimulation is used. For example, it is not possible to stimulate only the mid-wavelength/"green" cones: the other cones must be stimulated to some degree at the same time, even if light of some single wavelength is used (including that to which the target cones are maximally sensitive). 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, although the identification of a specific color is highly subjective, since even the two eyes of a single individual perceive colors slightly differently. This is discussed in more detail below.


The rod system (which vision in very low light relies on exclusively) does not by itself sense differences in wavelength; therefore it is not normally implicated in color vision. But experiments have conclusively shown that in certain marginal conditions a combination of rod stimulation and cone stimulation can result in color discriminations not based on the mechanisms described above.


While the mechanisms of color vision at the level of the cones in the retina are well described in terms of tristimulus values (see above), color processing and perception above that base level are organized differently. A dominant theory of the higher neural mechanisms of color vision proposes three opponent processes, or opponent channels, constructed out of the raw input from the cones: a red-green channel, a blue-yellow channel, and a black-white ("luminance") channel. This theory does something to account for the structure of our subjective color experience (see discussion below). Blue and yellow are considered complementary colors, or opposites: you could not experience a bluish yellow (or a greenish red), any more than you could experience a dark brightness or a hot coldness. The four "polar" colors proposed as extremes in the two opponent processes other than black-white have some natural claim to being called primary colors. This is in competition with various sets of three primary colors proposed as "generators" of all normal human color experience (see below). This article or section should be merged with Opponent process Opponent process is observable in neuro impulses (Garbor wavelets), color illusions of seeing an opposite color after habituation, physiological homeostatis reactions for temperature, oxygen, food, and stimuluation control. ... There are two separate but equally valid sets of complementary colors, depending on whether youre referring to additive systems, where light is emitted, or subtractive systems, where (ideally white) light is reflected. ...


Clinical issues

If one or more types of a person's color-sensing cones are missing or less responsive than normal to incoming light, that person has a smaller or skewed color space and is said to be color deficient. Another term frequently used is color blind, although this can be misleading; only a small fraction of color deficient individuals actually see completely in black and white, and most simply have anomalous color perception. Some kinds of color deficiency are caused by anomalies in the number or nature of cones of the various types, as just described. 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. ...


Some animals may have more than three different types of color receptor (most marsupials, birds, reptiles, and fish; see tetrachromat, below) or fewer (most mammals; these are called dichromats and monochromats). 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. ... Atlantic herring, Clupea harengus, the most abundant fish species in the world. ... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals characterized by the presence of mammary glands...


An unusual and elusive neurological condition sometimes affecting color perception is synaesthesia. Does a form of synaesthesia exist in everyone? It appears that people may not attach sounds to shapes arbitrarily. ...


Tetrachromat

A normal human is a trichromat (from Greek: tri=three, chroma=color). In theory it may be possible for a person to have four, rather than three, distinct types of cone cell. If these four types are sufficiently distinct in spectral sensitivity and the neural processing of the input from the four types is developed, a person may be a tetrachromat (tetra=four). Such a person might have an extra and slightly different copy of either the medium- or long-wave cones. It is not clear that such people exist or that the human brain could actually process the information from such an extra cone type separately from the standard three. However, strong evidence suggests such people do exist, are all female by genetic imperative, and their brain gladly adapts to use the additional information. For many species, tetrachromacy is the normal case, although the cone cells of animal tetrachromats have a very different (more evenly-spaced) spectral sensitivity distribution than those of possible human tetrachromats. 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. ...


Color perception

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.


When the eye shifts attention after viewing a color for some time, then an after-image of the complement of that color (the color opposite to it in the color wheel) is perceived by the eye for some time wherever it moves. This effect of color perception was utilised by Vincent van Gogh, a Post-Impressionist painter. There are two separate but equally valid sets of complementary colors, depending on whether youre referring to additive systems, where light is emitted, or subtractive systems, where (ideally white) light is reflected. ... Self-portrait (1886) Vincent Willem van Gogh (March 30, 1853–July 29, 1890) was a Dutch painter, generally considered one of the greatest painters in European art history. ... A Hundred Years of Independence by Henri Rousseau Post-impressionism is a term applied to painting styles of the late 19th and early 20th centuries — after impressionism. ...


Effect of luminosity

Note that the color experience of a given light mixture may vary with absolute luminosity, because 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 scene is reduced. This effect leads to a change in color rendition with absolute illumination levels that can be summarised in the "Kruithof curve". // In General Physics In general physics, luminosity (more properly called luminance) is the density of luminous intensity in a given direction. ... 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...


Cultural influences

Different cultures have different terms for colors, and may also assign some color names to slightly different parts of the spectrum, or have a different color ontology: for instance, the Han character 青 (pronounced qīng in Mandarin and aoi in Japanese) has a meaning that covers both blue and green; blue and green are considered shades of 青. A color name is a linguistic label that humans attach to a color. ... Technical note: Due to technical limitations, some web browsers may not display some special characters in this article. ... Standard Mandarin refers to the official Chinese spoken language used by the Peoples Republic of China, the Republic of China on Taiwan, Malaysia and Singapore. ...


Similarly, languages are selective when deciding which hues are split into different colors on the basis of how light or dark they are. Apart from the black-grey-white continuum, English splits some hues into several distinct colors according to lightness: such as red and pink or orange and brown. To English speakers, these pairs of colors, which are objectively no more different that light green and dark green, are conceived as totally different. An Italian will make the same red-pink and orange-brown distinctions, but will also make a further distinction between blu and azzurro, which English speakers would simply call dark and light blue. To Italian speakers, blu and azzurro are as separate as red and pink or orange and brown.


Color terms evolve. It is argued that there are a limited number of universal "basic color terms" which begin to be used by individual cultures in a relatively fixed order. For example, a culture would start with only two terms, meaning roughly 'dark' (covering black, dark colors and cold colors such as blue ) and 'bright' (covering white, light colors and warm colors such as red), before adding more specific color names, in the order of red; green and/or yellow; blue; brown; and orange, pink, purple, and/or gray. Older arguments for this theory also stipulated that the acquisition and use of basic color terms further along the evolutionary order indicated a more complex culture with more highly developed technology.


A somewhat dated example of a universal color categories theory is Basic Color Terms: Their Universality and Evolution (1969) by Brent Berlin and Paul Kay. A more recent example of a linguistic determinism theory might be Is color categorisation universal? New evidence from a stone-age culture (1999) by Jules Davidoff et al. The idea of linguistically determined color categories is often used as evidence for the Sapir-Whorf hypothesis (Language, Thought, and Reality (1956) by Benjamin Lee Whorf). In linguistics, the Sapir-Whorf hypothesis (SWH) states that there is a systematic relationship between the grammatical categories of the language a person speaks and how that person both understands the world and behaves in it. ... Benjamin Lee Whorf (April 24, 1897 - July 26, 1941) was an American linguist. ...


Additionally, different colors are often associated with different emotional states, values, or groups, but these associations can vary between cultures. In one system, red is considered to motivate action; orange and purple are related to spirituality; yellow cheers; green creates cosiness and warmth; blue relaxes; and white is associated with either purity or death. These associations are described more fully in the individual color pages, and under color psychology. Color psychology is a field of study devoted to analyzing the effect of color on human behavior and feeling. ...


See also: National colors National colours are frequently part of a countrys set of national symbols. ...


Color constancy

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 discovered by Edwin Land in the 1970s and led to his retinex theory of color constancy. Edwin Herbert Land (May 7, 1909 – March 1, 1991) was an American scientist and inventor. ... This article provides extensive lists of events and significant personalities of the 1970s. ... Color constancy is a feature of the human color-perception system which ensures that the perceived color of objects remains relatively constant under varying illumination conditions. ...


Contrast

Note: the following comparison requires an all-digital display setup (commonly, a laptop or DVI-connected LCD) to avoid errors caused by an unfortunate interaction between frequency response and gamma curves. Laptop with touchpad. ... DVI Connector The digital visual interface or digital video interface (DVI) is a video connector designed to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors. ... LCD redirects here. ... Frequency response is the measure of any systems response to frequency, but is usually used in connection with electronic amplifiers and similar systems, particularly in relation to audio signals. ... A gamma characteristic is a power-law relationship that approximates the relationship between the encoded luminance in a television system and the actual desired image brightness. ...


Compare the visibility of the RGB primary and secondary colors against a white background:

red green blue red+green green+blue red+blue red+green+blue zero light

Again, compare variations on gray backgrounds—#7f7f7f, #5f5f5f & #9f9f9f—the eight RGB primaries are equidistant from #7f7f7f in a 3-d geometrical representation of RGB color space—a reminder of the importance of background color for color perception. Color vision is a psychophysical phenomenon that exists only in our minds. ...


Background = #7f7f7f

red green blue red+green green+blue red+blue red+green+blue zero light


And let's look at black again, for completeness. (Note that your monitor background probably is not perfectly black. Turn it off and see for yourself.) The word monitor, depending on context, may have one of the following meanings: A Hall monitor, one who patrols the hall of a school. ...


Background = #00000

red green blue red+green green+blue red+blue red+green+blue zero light

Measurement and Reproduction of color

A colored photo of a sunset
A colored photo 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 ... Fruit stall in Barcelona, Spain. ... Binomial name Solanum lycopersicum L. The tomato (Solanum lycopersicum) is a plant in the Solanaceae or nightshade family, native to South and Central America. ...


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


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, 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. Orders Many - see section below. ...


Pigments and reflective media

When producing a color print or painting a surface, the applied paint changes the surface; if the surface is then illuminated with white light (which consists of equal intensities of all visible wavelengths), the reflected light will have a spectrum corresponding to the desired color. If a dab of paint looks red in white light, that is because the reflection of all non-red wavelengths is interrupted by the pigment, such that only red light is reflected into one's eye. White is a color (more accurately it contains all the colors of the visible spectrum and is sometimes described as an achromatic color—black is the absence of color) that has high brightness but zero hue. ...


Structural color

Structural color is a property of some surfaces that are scored with fine parallel lines, formed of many thin parallel layers, or otherwise composed of periodic microstructures on the scale of the color's wavelength, to make a diffraction grating. The grating reflects some wavelengths more than others due to interference phenomena, causing white light to be reflected as colored light. Variations in the pattern's spacing often give rise to an iridescent effect, as seen in peacock feathers, films of oil, and mother of pearl, because the reflected color depends upon the viewing angle. The wavelength is the distance between repeating units of a wave pattern. ... A huge diffraction grating. ... Interference of two circular waves - Wavelength (decreasing bottom to top) and Wave centers distance (increasing to the right). ... Peacock re-directs here; for alternate uses see Peacock (disambiguation). ... 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). ...


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. ...


See also

Metamerism is a psychophysical phenomenon commonly defined incompletely as two samples which match when illuminated by a particular light source and then do not match when illuminated by a different light source. ... Chromophore is a term that describes the moiety of a molecule responsible for its color. ... The following is a partial list of colors with associated articles. ... This article is about the philosophical concept. ... White light is commonly described by its color temperature. ... In the arts of painting, and photography, color theory is a set of basic rules for mixing color to achieve a desired result. ... A political party is a political organization that subscribes to a certain ideology and seeks to attain political power within a government. ... Political colours are colours used to represent a political stance, a political ideology, or — in a telling use of terminology — a position on the political spectrum. ... Color psychology is a field of study devoted to analyzing the effect of color on human behavior and feeling. ... Theory of Colours was a work published by Johann Wolfgang von Goethe in 1810. ... Authors of web pages have a variety of options available for specifying colors for elements of web documents. ... In computing, HyperText Markup Language (HTML) is a markup language designed for the creation of web pages and other information viewable in a browser. ... The World Wide Web Consortium (W3C) is a consortium that produces standards—recommendations, as they call them—for the World Wide Web. ... In mathematics and computer science, hexadecimal or simply hex is a numeral system with a radix or base of 16 usually written using the symbols 0–9 and A–F or a–f. ... Decimal, or less commonly, denary, usually refers to the base 10 numeral system. ... Authors of web pages have a variety of options available for specifying colors for elements of web documents. ... 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. ...

External links


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