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. The nervous system derives color by comparing the responses to light from the several types of cone photoreceptors in the eye. These cone photoreceptors are sensitive to different portions of the visible spectrum. For humans, the visible spectrum ranges approximately from 380 to 750 nm, and there are normally three types of cones. The visible range and number of cone types differ between species. For other uses, see Wavelength (disambiguation). ... For other uses, see Frequency (disambiguation). ... For other uses, see Light (disambiguation). ... Normalized responsivity spectra of human cone cells, S, M, and L types Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. ... Visible light redirects here. ...

A 'red' apple does not emit red light. Rather, it simply absorbs all the frequencies of visible light shining on it except for a group of frequencies that is perceived as red, which are reflected. An apple is perceived to be red only because the human eye can distinguish between different wavelengths. Three things are needed to see color: a light source, a detector (e.g. the eye) and a sample to view. For other uses, see Frequency (disambiguation). ... The optical spectrum (light or visible spectrum) is the portion of the electromagnetic spectrum that is visible to the human eye. ... This article refers to the sight organ. ... Color is an important part of the visual arts. ... For other uses, see Eye (disambiguation). ...

The advantage of color, which is a quality constructed by the visual brain and not a property of objects as such, is the better discrimination of surfaces allowed by this aspect of visual processing. color in minf jpg File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ...

In order for animals to respond accurately to their environments, their visual systems need to correctly interpret the form of objects around them. A major component of this is perception of colors.

Physiology of color perception

Normalized response spectra of human cones, S, M, and L types, to monochromatic spectral stimuli

Perception of color is achieved in mammals through color receptors containing pigments with different spectral sensitivities. In most primates closely related to humans there are three types of color receptors (known as cone cells). This confers trichromatic color vision, so these primates, like humans, are known as trichromats. Many other primates and other mammals are dichromats, and many mammals have little or no color vision. Image File history File links Cones_SMJ2_E.svg‎ Simplified human cone response curves, based on Dicklyons PNG version, itself based on data from Stockman, MacLeod & Johnson (1993) Journal of the Optical Society of America A, 10, 2491-2521d (log E human cone response, via http://www. ... Subclasses & Infraclasses Subclass †Allotheria* Subclass Prototheria Subclass Theria Infraclass †Trituberculata Infraclass Metatheria Infraclass Eutheria Mammals (class Mammalia) are warm-blooded, vertebrate animals characterized by the presence of sweat glands, including milk producing sweat glands, and by the presence of: hair, three middle ear bones used in hearing, and a neocortex... Although some radiations are marked as N for no in the diagram, some waves do in fact penetrate the atmosphere, although extremely minimally compared to the other radiations The electromagnetic (EM) spectrum is the range of all possible electromagnetic radiation. ... Families Cercopithecidae Hylobatidae Hominidae Catarrhini is the unranked group of the Primates, one of the three major divisions of the suborder Haplorrhini. ... Color receptors or retina receptors are light sensitive cells that the eye uses to detect light. ... Normalized responsivity spectra of human cone cells, S, M, and L types Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. ... 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. ... A trichromat 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 three different pure spectral lights. ... A dichromat 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 two different pure spectral lights. ...

In the human eye, the cones are maximally receptive to short, medium, and long wavelengths of light and are therefore usually called S-, M-, and L-cones. L-cones are often referred to as the red receptor, but while the perception of red depends on this receptor, microspectrophotometry has shown that its peak sensitivity is in the greenish-yellow region of the spectrum. Similarly, the S- and M-cones do not directly correspond to blue and green, although they are often depicted as such (such as in the graph to the right). It is important to note that the RGB color model is merely a convenient means for representing color, and is not directly based on the types of cones in the human eye. For other uses, see Red (disambiguation). ... This article is about the colour. ... For other uses, see Green (disambiguation). ... RGB redirects here. ...

The peak response of human color receptors varies, even amongst individuals with 'normal' color vision;^[1] in non-human species this polymorphic variation is even greater, and it may well be adaptive.^[2]

Theories of color vision

Two complementary theories of color vision are the trichromatic theory and the opponent process theory. The trichromatic theory as mentioned above states that the retina's three types of cones are preferentially sensitive to blue, green, and red. Ewald Hering proposed the opponent process theory in 1872.^[3] It states that the visual system interprets color in an antagonistic way: red vs. green, blue vs. yellow, black vs. white. We now know both theories to be correct, describing different stages in visual physiology. 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. ... Opponent colors based on experiment. ... Ewald Hering (full name Karl Ewald Konstantin Hering) (August 5, 1834 - January 26, 1918) was a German physiologist who did much research into color vision and spatial perception. ...

Cone cells in the human eye

A range of wavelengths of light stimulates each of these receptor types to varying degrees. Yellowish-green light, for example, stimulates both L and M cones equally strongly, but only stimulates S-cones weakly. Red light, on the other hand, stimulates L cones much more than M cones, and S cones hardly at all; blue-green light stimulates M cones more than L cones, and S cones a bit more strongly, and is also the peak stimulant for rod cells; and violet light stimulates almost exclusively S-cones. The brain combines the information from each type of receptor to give rise to different perceptions of different wavelengths of light. A nanometre (American spelling: nanometer, symbol nm) (Greek: νάνος, nanos, dwarf; μετρώ, metrό, count) is a unit of length in the metric system, equal to one billionth of a metre (or one millionth of a millimetre), which is the current SI base unit of length. ... 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). ...

The pigments present in the L and M cones are encoded on the X chromosome; defective encoding of these leads to the two most common forms of color blindness. The OPN1LW gene, which codes for the pigment that responds to yellowish light, is highly polymorphic (a recent study by Verrelli and Tishkoff found 85 variants in a sample of 236 men^[6]), so up to ten percent of women^[7] have an extra type of color receptor, and thus a degree of tetrachromatic color vision.^[8] Variations in OPN1MW, which codes for the bluish-green pigment, appear to be rare, and the observed variants have no effect on spectral sensitivity. A scheme of a condensed (metaphase) chromosome. ... Color blindness in humans is the inability to perceive differences between some or all colors that other people can distinguish. ... In biology, polymorphism can be defined as the occurrence in the same habitat of two or more forms of a trait in such frequencies that the rarer cannot be maintained by recurrent mutation alone. ... 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 in the human brain

Color processing begins at a very early level in the visual system (even within the retina) through initial color opponent mechanisms. Opponent mechanisms refer to the opposing color effect of red-green, blue-yellow, and light-dark. Visual information is then sent back via the optic nerve to the optic chiasm: a point where the two optic nerves meet and information from the temporal (contralateral) visual field crosses to the other side of the brain. After the optic chiasm the visual fiber tracts are referred to as the optic tracts, which enter the thalamus to synapse at the lateral geniculate nucleus (LGN). The LGN is segregated into six layers: two magnocellular (large cell) achromatic layers (M cells) and four parvocellular (small cell) chromatic layers (P cells). Within the LGN P-cell layers there are two chromatic opponent types: red vs. green and blue vs. green/red. This article is about the anatomical structure. ... Visual pathway with optic chiasm circled The optic chiasm (from the Greek χλαζειν to mark with an X, after the letter Χ chi) is the part of the brain where the optic nerves partially cross, those parts of the right eye which see things on the right side being connected to the... The optic tract is a part of the visual system in the brain. ... The thalamus (from Greek θάλαμος = bedroom, chamber, IPA= /ˈθæləməs/) is a pair and symmetric part of the brain. ... Grays FIG. 719– Hind- and mid-brains; postero-lateral view. ...

After synapsing at the LGN, the visual tract continues on back toward the primary visual cortex (V1) located at the back of the brain within the occipital lobe. Within V1 there is a distinct band (striation). This is also referred to as "striate cortex", with other cortical visual regions referred to collectively as "extrastriate cortex".It is at this stage that color processing becomes much more complicated. Illustration of the major elements in a prototypical synapse. ... Brodmann area 17 (primary visual cortex) is shown in red in this image which also shows area 18 (orange) and 19 (yellow) The visual cortex refers to the primary visual cortex (also known as striate cortex or V1) and extrastriate visual cortical areas such as V2, V3, V4, and V5. ... The occipital lobe is the visual processing center of the mammalian brain, containing most of the anatomical region of the visual cortex. ...

Visual pathways in the human brain. The ventral stream (purple) is important in color recognition. The dorsal stream (green) is also shown. They originate from a common source in the visual cortex.

In V1 the simple three-color segregation begins to break down. Many cells in V1 respond to some parts of the spectrum better than others, but this "color tuning" is often different depending on the adaptation state of the visual system. A given cell that might respond best to long wavelength light if the light is relatively bright might then become responsive to all wavelengths if the stimulus is relatively dim. Because the color tuning of these cells is not stable, some believe that a different, relatively small, population of neurons in V1 is responsible for color vision. These specialized "color cells" often have receptive fields that can compute local cone ratios. Such "double-opponent" cells were initially described in the goldfish retina by Nigel Daw;^[9][10] their existence in primates was suggested by David H. Hubel and Torsten Wiesel and subsequently proven by Bevil Conway.^[11] As Margaret Livingstone and David Hubel showed, double opponent cells are clustered within localized regions of V1 called blobs, and are thought to come in two flavors, red-green and blue-yellow.^[12] Red-green cells compare the relative amounts of red-green in one part of a scene with the amount of red-green in an adjacent part of the scene, responding best to local color contrast (red next to green). Modeling studies have shown that double-opponent cells are ideal candidates for the neural machinery of color constancy explained by Edwin H. Land in his retinex theory.^[13] Image File history File links Ventral-dorsal_streams. ... Image File history File links Ventral-dorsal_streams. ... The primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. ... The dorsal stream is a pathway for visual information which flows through the visual cortex, the part of the brain which provides visual processing. ... Brodmann area 17 (primary visual cortex) is shown in red in this image which also shows area 18 (orange) and 19 (yellow) The visual cortex refers to the primary visual cortex (also known as striate cortex or V1) and extrastriate visual cortical areas such as V2, V3, V4, and V5. ... David Hunter Hubel (b. ... Torsten Nils Wiesel (b. ... 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. ... Edwin Herbert Land Edwin Herbert Land (May 12, 1909 â€“ March 1, 1991) was an American scientist and inventor. ... Color constancy is a feature of the human color-perception system which ensures that the perceived color of objects remains (almost) constant under varying light conditions. ...

From the V1 blobs, color information is sent to cells in the second visual area, V2. The cells in V2 that are most strongly color tuned are clustered in the "thin stripes" that, like the blobs in V1, stain for the enzyme cytochrome oxidase (separating the thin stripes are interstripes and thick stripes, which seem to be concerned with other visual information like motion and high-resolution form). Neurons in V2 then synapse onto cells in area V4. Area V4 is a relatively large visual area, the largest by far cortical area outside V1, encompassing almost as much cortex as V1. Neurons in V4 were originally proposed by Semir Zeki to be exclusively dedicated to color, but this has since been shown not to be the case.^[14] Quantitative studies have argued that there is no higher concentration of color cells in V4 than in primary visual cortex, although this remains controversial. Independent of color sensitivity, V4 neurons have been shown to be very sensitive to the shape of stimuli, curvature, and stereo-scopic depth. V4 neurons have also been shown to be modulated by attention. The role of V4 neurons in color vision remains to be better characterized: indeed the vast majority of scientific papers examining the function of V4 do not concern color processing. Semir Zeki is Professor of Neurobiology at University College London. ...

Anatomical studies have shown that neurons in V4 provide input to the inferior temporal lobe . "IT" cortex is thought to integrate color information with shape and form, although it has been difficult to define the appropriate criteria for this claim. Despite this murkiness, it has been useful to characterize this pathway (V1 > V2 > V4 > IT) as the ventral stream or the "what pathway", distinguished from the dorsal stream ("where pathway") that is thought to analyze motion, among many other features. The temporal lobes are part of the cerebrum. ... The primate visual system consists of about thirty areas of the cerebral cortex called the visual cortex. ... The dorsal stream is a pathway for visual information which flows through the visual cortex, the part of the brain which provides visual processing. ...

In other animals

Other animals, such as tropical fish and birds, may have more complex color vision systems than humans.^[15] In the latter example, tetrachromacy is achieved through up to four cone types, depending on species. Brightly colored oil droplets inside the cones shift or narrow the spectral sensitivity of the cell. It has been suggested that it is likely that pigeons are pentachromats. Mammals other than primates generally have less effective two-receptor color perception systems, allowing only dichromatic color vision; marine mammals have only a single cone type and are thus monochromats. Many invertebrates have color vision. Honey- and bumblebees have trichromatic color vision, which is insensitive to red but sensitive in ultraviolet to a color called bee purple. Papilio butterflies apparently have tetrachromatic color vision despite possessing six photoreceptor types.^[16] The most complex color vision system in animal kingdom has been found in stomatopods with up to 12 different spectral receptor types which are thought to work as multiple dichromatic units.^[17] For other uses, see Fish (disambiguation). ... For other meanings of bird, see bird (disambiguation). ... Pigeon redirects here. ... A pentachromat 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 five different pure spectral lights. ... A dichromat 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 two different pure spectral lights. ... A Humpback whale (Megaptera novaeangliae), a member of Order Cetacea A Leopard seal (Hydrurga leptonyx), a member of infrafamily Pinnipedia A West Indian Manatee (Trichechus manatus), a member of Order Sirenia A pair of Sea Otters (Enhydra lutris), a member of family Mustelidae A Polar bear (Ursus maritimus), a member... A monochromat is an organism that is truly color blind. ... Families Andrenidae Anthophoridae Apidae Colletidae Ctenoplectridae Halictidae Heterogynaidae Megachilidae Melittidae Oxaeidae Sphecidae Stenotritidae This article is about the insect. ... Families Not necessarily a complete list: Alainosquillidae Bathysquillidae Coronididae Erythrosquillidae Eurysquillidae Gonodactylidae Hemisquillidae Indosquillidae Lysiosquillidae Nannosquillidae Odontodactylidae Parasquillidae Protosquillidae Pseudosquillidae Squillidae Takuidae Tetrasquillidae The Mantis shrimps are the order Stomatopoda of crustaceans. ...

Evolution

Color perception mechanisms are highly dependent on evolutionary factors, of which the most prominent is thought to be satisfactory recognition of food sources. In herbivorous primates, color perception is essential for finding proper (mature) leaves. In hummingbirds, particular flower types are often recognized by color as well. On the other hand, nocturnal mammals have less-developed color vision, since adequate light is needed for cones to function properly. There is evidence that ultraviolet light plays a part in color perception in many branches of the animal kingdom, especially insects. In zoology, an herbivore is an animal that is adapted to eat primarily plants (rather than meat). ... For other uses, see Hummingbird (disambiguation). ... A nocturnal animal is one that sleeps during the day and is active at night - the opposite of the human (diurnal) schedule. ... For other uses, see Ultraviolet (disambiguation). ... See Animal. ... Orders Subclass Apterygota Archaeognatha (bristletails) Thysanura (silverfish) Subclass Pterygota Infraclass Paleoptera (Probably paraphyletic) Ephemeroptera (mayflies) Odonata (dragonflies and damselflies) Infraclass Neoptera Superorder Exopterygota Grylloblattodea (ice-crawlers) Mantophasmatodea (gladiators) Plecoptera (stoneflies) Embioptera (webspinners) Zoraptera (angel insects) Dermaptera (earwigs) Orthoptera (grasshoppers, etc) Phasmatodea (stick insects) Blattodea (cockroaches) Isoptera (termites) Mantodea (mantids) Psocoptera...

Trichromatic color vision evolved in the ancestors of modern monkeys, apes, and humans as they switched to diurnal (daytime) activity and consumption of fruits from flowering plants.^[18] A diurnal animal (dī-ŭrnəl) is an animal that is active during the daytime and sleeps during the night. ...

Mathematics of color perception

A "physical color" is a combination of pure spectral colors (in the visible range). Since there are, in principle, infinitely many distinct spectral colors, the set of all physical colors may be thought of as an infinite-dimensional vector space, in fact a Hilbert space. We call this space H_color. More technically, the space of physical colors may be considered to be the (mathematical) cone over the simplex whose vertices are the spectral colors. A spectral color is a color that is evoked by the optical spectrum; every wavelength of light yields a different spectral color, in a continuous spectrum. ... In mathematics, a vector space (or linear space) is a collection of objects (called vectors) that, informally speaking, may be scaled and added. ... The mathematical concept of a Hilbert space (named after the German mathematician David Hilbert) generalizes the notion of Euclidean space in a way that extends methods of vector algebra from the plane and three-dimensional space to spaces of functions. ... In topology, especially algebraic topology, the cone CX of a topological space X is the quotient space: of the product of X with the unit interval I = [0, 1]. Intuitively we make X into a cylinder and collapse one end of the cylinder to a point. ...

An element C of H_color is a function from the range of visible wavelengths—considered as an interval of real numbers [W_min,W_max]—to the real numbers, assigning to each wavelength w in [W_min,W_max] its intensity C(w).

A humanly perceived color may be modeled as three numbers: the extents to which each of the 3 types of cones is stimulated. Thus a humanly perceived color may be thought of as a point in 3-dimensional Euclidean space. We call this space R³_color. Around 300 BC, the Greek mathematician Euclid laid down the rules of what has now come to be called Euclidean geometry, which is the study of the relationships between angles and distances in space. ...

Since each wavelength w stimulates each of the 3 types of cone cells to a known extent, these extents may be represented by 3 functions s(w), m(w), l(w) corresponding to the response of the S, M, and L cone cells, respectively.

Finally, since a beam of light can be composed of many different wavelengths, to determine the extent to which a physical color C in H_color stimulates each cone cell, we must calculate the integral (with respect to w), over the interval [W_min,W_max], of C(w)*s(w), of C(w)*m(w), and of C(w)*b(w). The triple of resulting numbers associates to each physical color C (which is a region in H_color) to a particular perceived color (which is a single point in R³_color). This association is easily seen to be linear. It may also easily be seen that many different regions in the "physical" space H_color can all result in the same single perceived color in R³_color, so a perceived color is not unique to one physical color.

Thus human color perception is determined by a specific, non-unique linear mapping from the infinite-dimensional Hilbert space H_color to the 3-dimensional Euclidean space R³_color.

Technically, the image of the (mathematical) cone over the simplex whose vertices are the spectral colors, by this linear mapping, is also a (mathematical) cone in R³_color. Moving directly away from the vertex of this cone represents maintaining the same chromaticity while increasing its intensity. Taking a cross-section of this cone yields a 2D chromaticity space. Both the 3D cone and its projection or cross-section are convex sets; that is, any mixture of spectral colors is also a color. Chromaticity is the quality of a color as determined by its purity and dominant wavelength. ...

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.

In practice, it would be quite difficult to measure an individual's cones' three responses to various physical color stimuli. So instead, three specific benchmark test lights are typically used; let us call them S, M, and L. In order to calibrate human perceptual space, scientists allowed human subjects to try to match any physical color by turning dials to create specific combinations of intensities (I_S, I_M, I_L) for the S, M, and L lights, resp., until a match was found. This needed only to be done for physical colors that are spectral (since a linear combination of spectral colors will be matched by the same linear combination of their (I_S, I_M, I_L) matches). Note that in practice, often at least one of S, M, L would have to be added with some intensity to the physical test color, and that combination matched by a linear combination of the remaining 2 lights. Across different individuals (without color blindness), the matchings turned out to be nearly identical. Image File history File links CIExy1931. ... Image File history File links CIExy1931. ...

By considering all the resulting combinations of intensities (I_S, I_M, I_L) as a subset of 3-space, a model for human perceptual color space is formed. (Note that when one of S, M, L had to be added to the test color, its intensity was counted as negative.) Again, this turns out to be a (mathematical) cone—not a quadric, but rather all rays through the origin in 3-space passing through a certain convex set. Again, this cone has the property that moving directly away from the origin corresponds to increasing the intensity of the S, M, L lights proportionately. Again, a cross-section of this cone is a planar shape that is (by definition) the space of "chromaticities" (informally: distinct colors); one particular such cross section, corresponding to constant X+Y+Z of the CIE 1931 color space, gives the CIE chromaticity diagram. 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. ...

It should be noted that this system implies that for any hue or non-spectral color, there are infinitely many distinct physical spectra that are all perceived as that hue or color. So, in general there is no such thing as the combination of spectral colors that we perceive as (say) yellow-green; instead there are infinitely many possibilities.

(The only exceptions to this rule are the perceptual colors corresponding to the boundary of the cone: in other words, those chromaticities on the simple closed curve that is the boundary of the 1931 C.I.E. diagram depicted in the figure. These comprise precisely all spectral colors plus the "line of purples" connecting the ends of the spectral colors: for each of these, there is only one physical color in H_color that can create that perceived color.)

The CIE chromaticity diagram is horseshoe-shaped, with its curved edge corresponding to all spectral colors (the spectral locus), and the remaining straight edge corresponding to the most saturated purples—mixtures of red and violet. In mathematics, a locus (Latin for place, plural loci) is a collection of points which share a common property. ... This article is about the color. ... For other uses, see Red (disambiguation). ... 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). ...

Chromatic adaptation

An object may be viewed under various conditions. For example, it may be illuminated by sunlight, the light of a fire, or a harsh electric light. In all of these situations, human vision perceives that the object has the same color: an apple always appears red, whether viewed at night or during the day. On the other hand, a camera with no adjustment for light may register the apple as having varying color. This feature of the visual system is called chromatic adaptation, or color constancy; when the correction occurs in a camera it is referred to as white balance. 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. ... White light is commonly described by its color temperature. ...

Chromatic adaptation is one aspect of vision that may fool someone into observing a color-based optical illusion, such as the same color illusion. An optical illusion. ... Squares A and B are the same color. ...

Though the human visual system generally does maintain constant perceived color under different lighting, there are situations where the relative brightness of two different stimuli will appear reversed at different illuminance levels. For example, the bright yellow petals of flowers will appear dark compared to the green leaves in dim light while the opposite is true during the day. This is known as the Purkinje effect, and arises because the peak sensitivity of the human eye shifts toward the blue end of the spectrum at lower light levels. Illuminance is the total luminous flux incident per unit area. ... The Purkinje effect (sometimes called the Purkinje shift, or dark adaptation) is the tendency for the peak sensitivity of the human eye to shift toward the blue end of the color spectrum at low illumination levels. ...

It has been suggested that this section be split into a new article. (Discuss)

Image File history File links No higher resolution available. ...

Von Kries transform

The von Kries chromatic adaptation method is a technique that is sometimes used in camera image processing. The method is to apply a gain to each of the human cone cell spectral sensitivity responses so as to keep the adapted appearance of the reference white constant. The application of Johannes von Kries's idea of adaptive gains on the three cone cell types was first explicitly applied to the problem of color constancy by Herbert E. Ives,^[19][20] and the method is sometimes referred to as the Ives tranform^[21] or the von Kries–Ives adaptation.^[22] Normalized responsivity spectra of human cone cells, S, M, and L types Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. ... Johannes von Kries (1853–1928) was a German physiological psychologist[1] who formulated the modern duplicity or duplexity theory of vision mediated by rods at low light levels and three types of cones at higher light levels. ... Normalized responsivity spectra of human cone cells, S, M, and L types Cone cells, or cones, are photoreceptor cells in the retina of the eye which function best in relatively bright light. ... Dr. Herbert Eugene Ives (1882–1953) was a scientist and engineer who headed the development of facsimile and television systems at AT&T in the first half of the twentieth century. ...

The von Kries coefficient rule rests on the assumption that color constancy is achieved by individually adapting the gains of the three cone responses, the gains depending on the sensory context, that is, the color history and surround. Thus, the cone responses c' from two radiant spectra can be matched by appropriate choice of diagonal adaptation matrices D₁ and D₂^[23]: 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. ...

where S is the cone sensitivity matrix and f is the spectrum of the conditioning stimulus. This leads to the von Kries transform for chromatic adaptation in LMS color space (responses of long-, medium-, and short-wavelength cone response space): A Color space represented by the trichromatic response of the three type of cones: Long, Middle and Short wavelength. ...

This diagonal matrix D maps cone responses, or colors, in one adaptation state to corresponding colors in another; when the adaptation state is presume to be determined by the illuminant, this matrix is useful as an illuminant adaptation transform. The elements of the diagonal matrix D are the ratios of the cone responses (Long, Medium, Short) for the illuminant's white point. A white point is one of a number of reference illuminants used in colorimetry which serve to define the color white. Depending on the application, different definitions of white are needed to give acceptable results. ...

The more complete von Kries transform, for colors represented in XYZ or RGB color space, includes matrix transformations into and out of LMS space, with the diagonal transform D in the middle.^[24] 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. ... An RGB color space is any additive color space based on the RGB color model. ...

References

Ewald Hering (full name Karl Ewald Konstantin Hering) (August 5, 1834 - January 26, 1918) was a German physiologist who did much research into color vision and spatial perception. ... Edwin Herbert Land Edwin Herbert Land (May 12, 1909 â€“ March 1, 1991) was an American scientist and inventor. ... Steven Pinker Steven Arthur Pinker (born September 18, 1954) is a prominent Canadian-born American experimental psychologist, cognitive scientist, and popular science writer known for his spirited and wide-ranging advocacy of evolutionary psychology and the computational theory of mind. ... How the Mind Works is a book by American cognitive scientist Steven Pinker, published in 1996. ... The CRC Press, LLC is a publishing group which specializes in producing technical books in a wide range of subjects. ...

See also

• Color theory
• Primary color
• Visual perception

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. ... This article is about colors. ... In psychology, visual perception is the ability to interpret visible light information reaching the eyes which is then made available for planning and action. ...

External links

• "Evidence that men, women literally see the world differently: Study shows color vision may have been adaptive during evolution."
• Spectral Sensitivity of the Eye.
• Vision may not be what we thought.
• Overview of color vision.
• The decoding model: a symmetrical model of color vision.
• Working examples of Chromatic Adaptation.
• Egopont color vision test
• What the eyes really see: brain image enhancement