Color circle: Difference between revisions
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[[Image:Colorcircle.png|thumb|400px|right|Color circle (illustration based on Schiffman, 1990)]] |
[[Image:Colorcircle.png|thumb|400px|right|Color circle (illustration based on Schiffman, 1990)]] |
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A '''color circle''' is a way of representing the [[visible spectrum]] in a circular form, with [[color]]s |
A '''color circle''' is a way of representing the [[visible spectrum]] in a circular form, with [[color]]s ordered around the circumference by spectral frequency. It is a [[psychophysics|psychophysical]] tool used in the exploration of the [[visual perception|perception]] of color, perceptual anomalies and [[optical illusion]]s. |
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==Description== |
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| ⚫ | A normal color circle will appear with [[red]] at one end of the spectrum and [[Violet (color)|violet]] at the other, and with a wedge-shaped gap representing colors which have no unique spectral frequency, but are rather formed by the additive mixture of colors from the two ends of the spectrum, such as [[purple]]. |
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In normal human vision, wavelengths of between 420 nm and 720 nm are represented by this incomplete circle, with the longer wavelengths equating to the red end of the spectrum. Luminance complements are located directly opposite each other on this wheel. These complements are not identical to those in pigment mixing (such as are used in paint), but when mixed in the correct proportions will appear as a neutral grey or white.<ref name="complements">Krech ''et al.'' (1982), pp. 108-109.</ref><!-- what's a "luminance complement"? when mixed how in the correct proportions? Answer: A luminance complement is one used with additive - that is, emanative, colour, as opposed to the mormally accepted subtractive meaning of the term, as used with paint. As to which correct proportions, that all depends on the two lights being mixed. Generally, however, when a light of sufficient brightness is added to its luminance complement, a neutral grey or white will be produced. This is not true when two lights which are not luminance complements are mixed, irrespective of the brightness of the two lights --> |
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| ⚫ | Objects may |
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| ⚫ | The color circle is used for, among other purposes, illustrating [[additive color]] mixture. Combining two colored lights from different parts of the spectrum may produce a third color that appears like a light from another part of the spectrum, even though dissimilar wavelengths are involved. This type of color matching is known as [[Metamerism (color)|metameric]] matching.<ref name="metamer">Schiffman (1990), pp. 252-253.</ref> Thus a combination of green and red light might produce a color close to yellow in apparent hue. The newly-formed color lies between the two original colors on the color circle, but they are usually represented as being joined by a straight line on the circle, the location of the new color closer to the (white) centre of the circle indicating that the resulting hue is less saturated (i.e., paler) than either of the two source colors. The combination of any two colors in this way will always be less saturated then the two colors individually. |
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| ⚫ | Objects may be viewed under a variety of different lighting conditions. The human visual system is able to adapt to these differences by [[chromatic adaptation]]. This aspect of the visual system is relatively easy to mislead, and optical illusions relating to color are therefore a common phenomenon. The color circle is a useful tool for examining these illusions. |
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==History== |
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The theory behind the color circle dates to the early work of [[Thomas Young]] (later extended by [[Herman von Helmholz]]), who postulated that the eye contains receptors which responded to red, green, and blue light. All visible light of any color can be created from these three colors, if they are mixed in the right proportions. The [[Young-Helmholz theory]] is still seen as the most effective in modeling human color vision,{{cn}} though the perception color vision system is far more complex than differences in the retina alone, with different cells in the [[lateral geniculate nucleus]] also responding in [[opponent process|opponent]] fashion to [[complementary color]]s, as reported by DeValois, Abramov, and Jacobs in [[1966]]. Further color coding occurs in the visual cortex.<ref name="LGN">Carlson (1981), pp. 247-250.</ref> |
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The actual display of colors using a wheel in order to predict the admixture of light can be traced to work by Sir [[Isaac Newton]], who created a circle of color arranged around a triangle with its points matched to red, green, and blue.{{cn}} This triangle may itself have been an influence on Young's theory.{{cn}} |
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==The color circle and the color wheel== |
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The color circle is analogous to the use of a [[color wheel]] in art, though there are numerous notable differences between the two. The two most important of these differences are the nature of the colored light and the purpose for which it is used. |
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Whereas the color circle is only ever used with additive (emissive) color, the color wheel is primarily used with [[subtractive color|subtractive]] (pigment) color. As such, the centre of a color wheel, if depicted in the same way as a color circle, would be black. Any color formed by the mixture of two pigments is darker, not lighter, than the individual pigments mixed.{{cn}}<!-- I'm not sure that subtractive color is inherent to the concept of a color wheel. That's not the point - that it is ''primarily'' used with subtractive colour (and every colour wheel I've ever heard described deals with pigment, and is thus inherently subtractive) does not rule out the possibility of it being used with additive colour. The colour circle is NEVER EVER used with subtractive colour--> |
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Furthermore, there is no straight-line relationship between the colors mixed in pigment, which will vary from medium to medium. Whereas with a psychophysical color circle, the resulting hue of any mixture of two colored light sources can be determined simply by the relative brightness and wavelength of the two lights<ref name="predictive">Schiffman (1990), pp. 252-253.</ref>, a similar calculation cannot be performed with two paints. As such, a color wheel is indicative rather than predictive, being used to compare existing colors rather than calculate exact colors of mixtures. Because of differences relating to the medium, different color wheels may be created according to the type of paint or other medium used, and many artists develop their own individual color wheels. These will often contain only blocks of color rather than the gradation between tones which is characteristic of the color circle.<ref name="paint">Rodwell (1987), pp. 94-95.</ref> |
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A further difference between the color circle and the color wheel is the location of individual colors on the wheel. Though both circles order their colors around the spectrum from red through yellow, green and blue to violet, the color wheel completes the circle by going through purple and back to red. The arcs connecting the different colors around the wheel and circle are also of slightly different sizes, so that a specific hue of green, for example, may be at a slightly different point on the color wheel and color circle.<!-- this rather depends on the specifics of the color wheel being used, doesn't it? A munsell hue wheel is going to look different than an RYB one. Answer: Well, that's exactly my point. There is a specific colour circle, but there is not a specific colour wheel. A Munsell hue wheel, a Winsor and Newton oil colour wheel, a Faber aquarelle wheel, an individual artist's wheel - all will be different. A colour circle is the colour circle of normal human vision and has no variant forms.--> |
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==See also== |
==See also== |
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*[[Color theory]] |
*[[Color theory]] |
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*[[Visual perception]] |
*[[Visual perception]] |
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*[[ |
*[[Gamma correction]] |
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*[[Psychophysics]] |
*[[Psychophysics]] |
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==References== |
==References== |
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*Carlson, N.R. (1981) ''Physiology of behavior'' (2nd ed.). Boston, MA: Allyn and Bacon. |
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*Gregory, R.L. (1966) ''Eye and brain''. London: Weidenfeld and Nicholson. |
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*Krech, D., Crutchfield, R.S., Livson, N., Wilson, W.A. jr., Parducci, A. (1982) ''Elements of psychology'' (4th ed.). New York: Alfred A. Knopf. |
*Krech, D., Crutchfield, R.S., Livson, N., Wilson, W.A. jr., Parducci, A. (1982) ''Elements of psychology'' (4th ed.). New York: Alfred A. Knopf. |
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*Rodwell, J. (1987) ''The complete watercolour artist''. London: Paul Press. |
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*Schiffman, H.R. (1990) ''Sensation and perception: An integrated approach'' (3rd ed.). New York: John Wiley & Sons. |
*Schiffman, H.R. (1990) ''Sensation and perception: An integrated approach'' (3rd ed.). New York: John Wiley & Sons. |
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==Notes== |
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{{reflist}} |
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[[Category:Vision]] |
[[Category:Vision]] |
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Revision as of 07:50, 20 September 2007
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A color circle is a way of representing the visible spectrum in a circular form, with colors ordered around the circumference by spectral frequency. It is a psychophysical tool used in the exploration of the perception of color, perceptual anomalies and optical illusions.
Description
A normal color circle will appear with red at one end of the spectrum and violet at the other, and with a wedge-shaped gap representing colors which have no unique spectral frequency, but are rather formed by the additive mixture of colors from the two ends of the spectrum, such as purple.
In normal human vision, wavelengths of between 420 nm and 720 nm are represented by this incomplete circle, with the longer wavelengths equating to the red end of the spectrum. Luminance complements are located directly opposite each other on this wheel. These complements are not identical to those in pigment mixing (such as are used in paint), but when mixed in the correct proportions will appear as a neutral grey or white.[1]
The color circle is used for, among other purposes, illustrating additive color mixture. Combining two colored lights from different parts of the spectrum may produce a third color that appears like a light from another part of the spectrum, even though dissimilar wavelengths are involved. This type of color matching is known as metameric matching.[2] Thus a combination of green and red light might produce a color close to yellow in apparent hue. The newly-formed color lies between the two original colors on the color circle, but they are usually represented as being joined by a straight line on the circle, the location of the new color closer to the (white) centre of the circle indicating that the resulting hue is less saturated (i.e., paler) than either of the two source colors. The combination of any two colors in this way will always be less saturated then the two colors individually.
Objects may be viewed under a variety of different lighting conditions. The human visual system is able to adapt to these differences by chromatic adaptation. This aspect of the visual system is relatively easy to mislead, and optical illusions relating to color are therefore a common phenomenon. The color circle is a useful tool for examining these illusions.
History
The theory behind the color circle dates to the early work of Thomas Young (later extended by Herman von Helmholz), who postulated that the eye contains receptors which responded to red, green, and blue light. All visible light of any color can be created from these three colors, if they are mixed in the right proportions. The Young-Helmholz theory is still seen as the most effective in modeling human color vision,[citation needed] though the perception color vision system is far more complex than differences in the retina alone, with different cells in the lateral geniculate nucleus also responding in opponent fashion to complementary colors, as reported by DeValois, Abramov, and Jacobs in 1966. Further color coding occurs in the visual cortex.[3]
The actual display of colors using a wheel in order to predict the admixture of light can be traced to work by Sir Isaac Newton, who created a circle of color arranged around a triangle with its points matched to red, green, and blue.[citation needed] This triangle may itself have been an influence on Young's theory.[citation needed]
The color circle and the color wheel
The color circle is analogous to the use of a color wheel in art, though there are numerous notable differences between the two. The two most important of these differences are the nature of the colored light and the purpose for which it is used.
Whereas the color circle is only ever used with additive (emissive) color, the color wheel is primarily used with subtractive (pigment) color. As such, the centre of a color wheel, if depicted in the same way as a color circle, would be black. Any color formed by the mixture of two pigments is darker, not lighter, than the individual pigments mixed.[citation needed]
Furthermore, there is no straight-line relationship between the colors mixed in pigment, which will vary from medium to medium. Whereas with a psychophysical color circle, the resulting hue of any mixture of two colored light sources can be determined simply by the relative brightness and wavelength of the two lights[4], a similar calculation cannot be performed with two paints. As such, a color wheel is indicative rather than predictive, being used to compare existing colors rather than calculate exact colors of mixtures. Because of differences relating to the medium, different color wheels may be created according to the type of paint or other medium used, and many artists develop their own individual color wheels. These will often contain only blocks of color rather than the gradation between tones which is characteristic of the color circle.[5]
A further difference between the color circle and the color wheel is the location of individual colors on the wheel. Though both circles order their colors around the spectrum from red through yellow, green and blue to violet, the color wheel completes the circle by going through purple and back to red. The arcs connecting the different colors around the wheel and circle are also of slightly different sizes, so that a specific hue of green, for example, may be at a slightly different point on the color wheel and color circle.
See also
References
- Carlson, N.R. (1981) Physiology of behavior (2nd ed.). Boston, MA: Allyn and Bacon.
- Gregory, R.L. (1966) Eye and brain. London: Weidenfeld and Nicholson.
- Krech, D., Crutchfield, R.S., Livson, N., Wilson, W.A. jr., Parducci, A. (1982) Elements of psychology (4th ed.). New York: Alfred A. Knopf.
- Rodwell, J. (1987) The complete watercolour artist. London: Paul Press.
- Schiffman, H.R. (1990) Sensation and perception: An integrated approach (3rd ed.). New York: John Wiley & Sons.