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In
color theory In the visual arts The visual arts are art forms such as painting Painting is the practice of applying paint Paint is any pigmented liquid, liquefiable, or solid mastic composition that, after application to a substrate in ...
, hue is one of the main properties (called color appearance parameters) of a
color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United States. Currently, American Engli ...

color
, defined technically in the
CIECAM02 In colorimetry Colorimetry is "the science and technology used to quantify and describe physically the human color perception". It is similar to spectrophotometry Spectrophotometry is a branch of electromagnetic spectroscopy concerned w ...
model as "the degree to which a
stimulus A stimulus is something that causes a physiological response. It may refer to: *Stimulation Stimulation is the encouragement of development or the cause of activity generally. For example, "The press provides stimulation of political discourse." ...

stimulus
can be described as similar to or different from stimuli that are described as
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...

red
,
orange Orange most often refers to: *Orange (colour), occurs between red and yellow in the visible spectrum *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Some other citrus or citrus-li ...
,
yellow Yellow is the color between green and Orange (colour), orange on the Visible spectrum, spectrum of visible light. It is evoked by light with a dominant wavelength of roughly 575585 Nanometre, nm. It is a primary color in subtractive color syst ...

yellow
,
green Green is the color between blue and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...

green
,
blue Blue is one of the three primary colours of pigments in painting and traditional colour theory In the visual arts The visual arts are art forms such as painting Painting is the practice of applying paint Paint is any pig ...

blue
,
violet Violet may refer to: Common meanings * Violet (color), a spectral color with wavelengths shorter than blue * One of a list of plants known as violet, particularly: ** Viola (plant), ''Viola'' (plant), a genus of flowering plants Places United ...
," which in certain theories of
color vision Color vision, a feature of visual perception Visual perception is the ability to interpret the surrounding environment (biophysical), environment through photopic vision (daytime vision), color vision, scotopic vision (night vision), and ...

color vision
are called
unique hues Unique primarily refers to: *Uniqueness Uniqueness is a state or condition wherein someone or something is unlike anything else in comparison. When used in relation to humans, it is often in relation to a person's personality, or some specific ch ...
. Hue can typically be represented quantitatively by a single number, often corresponding to an angular position around a central or neutral point or axis on a
color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whether such representation entails an analog signal, analog or a ...
coordinate diagram (such as a
chromaticity diagram Chromaticity is an objective specification of the quality of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red ...
) or
color wheel A color wheel or color circle is an abstract illustrative organization of color Color (American English) or colour (Commonwealth English) is the visual perception, visual perceptual Physical property, property corresponding in humans ...

color wheel
, or by its
dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color spaceThe "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, whi ...

dominant wavelength
or that of its
complementary color Complementary colors are pairs of color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native ...
. The other color appearance parameters are
colorfulness File:Saturation of digital colors.png, 300x300px, 7.5PB and 10BG Munsell hue pages of RGB colors, showing lines of uniform saturation (chroma in proportion to lightness) in red. Note that lines of uniform saturation radiate from near the black ...
, saturation (also known as intensity or chroma),
lightness Lightness is a visual perception of the luminance (L) of an object. It is often judged relative to a similarly lit object. In colorimetry and color appearance models, lightness is a prediction of how an illuminated color will appear to a stand ...

lightness
, and
brightness Brightness is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target. It is not necessarily proportional to lumina ...

brightness
. Usually, colors with the same hue are distinguished with adjectives referring to their lightness or colorfulness, such as with "light blue", "
pastel A pastel () is an in the form of a stick, consisting of powdered and a . The pigments used in pastels are similar to those used to produce some other colored visual arts media, such as s; the binder is of a neutral hue and low . The color e ...

pastel
blue", "vivid blue", "cobalt blue". Exceptions include
brown Brown is a composite color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English language native to the United State ...

brown
, which is a dark
orange Orange most often refers to: *Orange (colour), occurs between red and yellow in the visible spectrum *Orange (fruit), the fruit of the tree species '' Citrus'' × ''sinensis'' ** Orange blossom, its fragrant flower *Some other citrus or citrus-li ...
.C J Bartleson, "Brown". ''Color Research and Application'', 1 : 4, pp. 181–191 (1976). In
painting Painting is the practice of applying paint Paint is any pigmented liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient ...

painting
, a hue is a ''pure''
pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compound , CH4; is among the simplest organic compou ...
—one without tint or shade (added white or black pigment, respectively). Hues are first processed in the
brain A brain is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's tis ...

brain
in areas in the extended V4 called globs.


Deriving a hue

The concept of a color system with a hue was explored as early as 1830 with
Philipp Otto Runge, Hamburg en, Hamburgian(s) , timezone1 = Central European Time, CET , utc_offset1 = +1 , timezone1_DST = Central European Summer Time, CEST , utc_offset1_DST = +2 , ...
's color sphere. The
Munsell color system In colorimetry, the Munsell color system is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whethe ...
from the 1930s was a great step forward, as it was realized that
perceptual uniformityThe difference or distance between two colors is a metric (mathematics), metric of interest in color science. It allows quantified examination of a notion that formerly could only be described with adjectives. Quantification of these properties is of ...

perceptual uniformity
means the color space can no longer be a sphere. As a convention, the hue for
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...

red
is set to 0° for most color spaces with a hue.


Opponent color spaces

In opponent color spaces in which two of the axes are perceptually orthogonal to lightness, such as the CIE 1976 (''L''*, ''a''*, ''b''*) (
CIELAB The CIELAB color space also referred to as ''L*a*b*'' is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations o ...
) and 1976 (''L''*, ''u''*, ''v''*) (
CIELUV In colorimetry, the CIE 1976 ''L''*, ''u''*, ''v''* color space, commonly known by its abbreviation CIELUV, is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical de ...
) color spaces, hue may be computed together with chroma by converting these coordinates from
rectangular In Euclidean plane geometry, a rectangle is a quadrilateral A quadrilateral is a polygon in Euclidean geometry, Euclidean plane geometry with four Edge (geometry), edges (sides) and four Vertex (geometry), vertices (corners). Other names for ...

rectangular
form to
polar Polar may refer to: Geography Polar may refer to: * Geographical pole, either of two fixed points on the surface of a rotating body or planet, at 90 degrees from the equator, based on the axis around which a body rotates *Polar climate, the clim ...

polar
form. Hue is the angular component of the polar representation, while chroma is the radial component. Specifically, in CIELAB''Colorimetry,'' second edition: CIE Publication 15.2. Vienna: Bureau Central of the CIE, 1986. :h_ = \mathrm(b^*, a^*), while, analogously, in CIELUV :h_ = \mathrm(v^*, u^*) = \mathrm(v', u'), where,
atan2 The function Function or functionality may refer to: Computing * Function key A function key is a key on a computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automati ...

atan2
is a two-argument inverse tangent.


Defining hue in terms of RGB

PreucilFrank Preucil, "Color Hue and Ink Transfer … Their Relation to Perfect Reproduction, ''TAGA Proceedings,'' p 102-110 (1953). describes a color hexagon, similar to a trilinear plot described by Evans, Hanson, and Brewer,Ralph Merrill Evans, W T Hanson, and W Lyle Brewer, ''Principles of Color Photography.'' New York: Wiley, 1953 which may be used to compute hue from
RGB s The RGB color model is an additive color, additive color model A color model is an abstract mathematical model describing the way colors can be represented as tuples of numbers, typically as three or four values or color components. When ...

RGB
. To place
red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color ...

red
at 0°,
green Green is the color between blue and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 Nanometre, nm. In subtractive color systems, used in painting and color printing, it is created by ...

green
at 120°, and
blue Blue is one of the three primary colours of pigments in painting and traditional colour theory In the visual arts The visual arts are art forms such as painting Painting is the practice of applying paint Paint is any pig ...

blue
at 240°, : h_ = \mathrm\left( \sqrt \cdot (G - B)/ 2 \cdot R - G - B \right). Equivalently, one may solve : \tan( h_) = \frac. Preucil used a polar plot, which he termed a color circle. Using R, G, and B, one may compute hue angle using the following scheme: determine which of the six possible orderings of R, G, and B prevail, then apply the formula given in the table below. Note that in each case the formula contains the fraction \frac, where ''H'' is the highest of R, G, and B; ''L'' is the lowest, and ''M'' is the mid one between the other two. This is referred to as the "Preucil hue error" and was used in the computation of mask strength in photomechanical color reproduction.Miles Southworth, ''Color Separation Techniques'', second edition. Livonia, New York: Graphic Arts Publishing, 1979. Hue angles computed for the Preucil circle agree with the hue angle computed for the Preucil hexagon at integer multiples of 30° (red, yellow, green, cyan, blue, magenta, and the colors midway between contiguous pairs) and differ by approximately 1.2° at odd integer multiples of 15° (based on the circle formula), the maximal divergence between the two. The process of converting an RGB color into an
HSL color space HSL (hue, saturation, lightness) and HSV (hue, saturation, value, also known as HSB or hue, saturation, brightness) are alternative representations of the RGB color model, designed in the 1970s by computer graphics researchers to more closely align ...
or
HSV color space HSL (hue, saturation, lightness) and HSV (hue, saturation, value, also known as HSB or hue, saturation, brightness) are alternative representations of the RGB color model s The RGB color model is an additive color, additive color model in which ...
is usually based on a 6-piece piecewise mapping, treating the HSV cone as a hexacone, or the HSL double cone as a double hexacone. The formulae used are those in the table above.


24 hues of HSL/HSV

The hue angles below only apply to the two Preucil-style transformations of RGB, and does not apply to the more uniform Lab/LUV-based colorspaces. As illustrated by the variance in luminance, the RGB-based transformations separate the color-making attributes poorly.


Specialized hues

The hues exhibited by
caramel color Caramel color or caramel coloring is a water-soluble food coloring. It is made by heat treatment of carbohydrate is a disaccharide found in animal milk. It consists of a molecule of D-galactose and a molecule of D-glucose bonded by beta-1-4 g ...
ings and
beer Beer is one of the oldest and most widely consumed alcoholic drinks in the world, and the third most popular drink overall after water and tea. Beer is brewing, brewed from cereal, cereal grains—most commonly from malted barley, though wh ...

beer
s are fairly limited in range. The Linner hue index is used to quantify the hue of such products.


Usage in art

Manufacturers of pigments use the word hue, for example, "cadmium yellow (hue)" to indicate that the original pigmentation ingredient, often toxic, has been replaced by safer (or cheaper) alternatives whilst retaining the hue of the original. Replacements are often used for
chromium Chromium is a chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science tha ...

chromium
,
cadmium Cadmium is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical eleme ...

cadmium
and
alizarin Alizarin (also known as 1,2-dihydroxyanthraquinone, Mordant Red 11, Colour Index International, C.I. 58000, and Turkey Red) is an organic compound with formula that has been used throughout history as a prominent red dye, principally for dyeing ...

alizarin
.


Hue vs. dominant wavelength

Dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color spaceThe "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, whi ...

Dominant wavelength
(or sometimes equivalent wavelength) is a physical analog to the perceptual attribute hue. On a
chromaticity diagram Chromaticity is an objective specification of the quality of a color Color ( American English), or colour ( Commonwealth English), is the characteristic of visual perception described through color ''categories'', with names such as red ...
, a line is drawn from a
white point A white point (often referred to as reference white or target white in technical documents) is a set of tristimulus values or chromaticity coordinates that serve to define the color " white" in image capture, encoding, or reproduction. Depending ...
through the coordinates of the color in question, until it intersects the spectral locus. The wavelength at which the line intersects the spectrum locus is identified as the color's
dominant wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color spaceThe "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, whi ...

dominant wavelength
if the point is on the same side of the white point as the spectral locus, and as the color's
complementary wavelength Image:dominant wavelength.png, frame, Dominant/complementary wavelength example on the CIE color spaceThe "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, whi ...
if the point is on the opposite side.Deane B Judd and Günter Wyszecki, ''Color in Business, Science, and Industry.'' New York: Wiley, 1976.


Hue difference: \Delta h or \Delta H^*?

There are two main ways in which hue difference is quantified. The first is the simple difference between the two hue angles. The symbol for this expression of hue difference is \Delta h_ in CIELAB and \Delta h_ in CIELUV. The other is computed as the residual total color difference after Lightness and Chroma differences have been accounted for; its symbol is \Delta H^*_ in CIELAB and \Delta H^*_ in CIELUV.


Names and other notations

There exists some correspondence, more or less precise, between hue values and
color term A color term (or color name) is a word In linguistics, a word of a spoken language can be defined as the smallest sequence of phonemes that can be uttered in isolation with semantic, objective or pragmatics, practical meaning (linguistics), meani ...
s (names). One approach in color science is to use traditional color terms but try to give them more precise definitions. See spectral color#Table of spectral or near-spectral colors for names of highly saturated colors with the hue from ≈ 0° (red) up to ≈ 275° (violet), and line of purples#Table of highly-saturated purple colors for color terms of the remaining part of the color wheel. Alternative approach is to use a systematic notation. It can be a standard
angle In Euclidean geometry Euclidean geometry is a mathematical system attributed to Alexandrian Greek mathematics , Greek mathematician Euclid, which he described in his textbook on geometry: the ''Euclid's Elements, Elements''. Euclid's method ...

angle
notation for certain color model such as HSL/HSV mentioned above,
CIELUV In colorimetry, the CIE 1976 ''L''*, ''u''*, ''v''* color space, commonly known by its abbreviation CIELUV, is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical de ...
, or
CIECAM02 In colorimetry Colorimetry is "the science and technology used to quantify and describe physically the human color perception". It is similar to spectrophotometry Spectrophotometry is a branch of electromagnetic spectroscopy concerned w ...
. Alphanumeric notations such as of
Munsell color system In colorimetry, the Munsell color system is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whethe ...
, NCS, and
Pantone Matching System Pantone LLC is a limited liability company headquartered in Carlstadt, New Jersey. The company is best known for its Pantone Matching System (PMS), a patent, proprietary color space used in a variety of industries, notably graphic design, fashion ...
are also used.


See also

*
Lightness (color) In colorimetry and color theory, lightness, also known as value or tone, is a representation of a color's brightness. It is one of the Color appearance model#Color appearance parameters, color appearance parameters of any color appearance model ...
*
Chromaticity Chromaticity is an objective specification of the quality of a color Color (American English) or colour (Commonwealth English) is the visual perception, visual perceptual Physical property, property corresponding in humans to the cate ...
*
Munsell color system In colorimetry, the Munsell color system is a color space A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of color -- whethe ...
* Bezold–Brücke shift


References


External links


Editing of hue in photography
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Color Artistic techniques Graphic design Image processing Visual perception Qualia Vision {{CatAutoTOC ...