Dominant wavelength

Last updated January 05, 2024

Dominant/complementary wavelength example on the CIE color space
The "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, while the complementary wavelength is opposite, around 485 nm. Intuitively, the dominant wavelength of "x" corresponds to the primary hue of "x". Dominant wavelength.png — **Dominant/complementary wavelength example on the CIE color space**
The "x" marks the color in question. For the white point indicated, the dominant wavelength for "x" is on the nearer perimeter, around 600 nm, while the complementary wavelength is opposite, around 485 nm. Intuitively, the dominant wavelength of "x" corresponds to the primary hue of "x".

In color science, the dominant wavelength is a method of characterizing a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. A color's dominant wavelength is the wavelength of monochromatic spectral light that evokes an identical perception of hue.^[1]

Determination

Helmholtz coordinates

The Helmholtz coordinates are a polar coordinate system for defining a 2D chromaticity plane. The circumferential coordinate is the dominant wavelength, which is analogous to hue of the HSL and HSV color spaces. The radial coordinate is the purity, which is analogous to saturation of the HSL and HSV color spaces.^[2]

Color space

Any chromaticity diagram from any color space can be used for calculating the dominant wavelength as long as it is bound by a spectral locus defined by wavelength. However, the values will change depending on which color space is used. Unless otherwise stated, the CIE 1931 color space (CIEXYZ) is used.,^[3] but the CIELUV color space is sometimes used.^[1]^: 66

Calculation

To calculate the dominant wavelength of a chromaticity (or color), a straight line is drawn on the chromaticity diagram between the chromaticity's coordinates and the white point. The line is then extrapolated so it intersects the perimeter of the diagram at two points, where the perimeter comprises the spectral locus and/or line of purples. The point of intersection that is nearer to the chromaticity in question defines its dominant wavelength.^[4] The purity can then be calculated as defined here.^[1]

White point

The white point is generally defined as—or assumed to be—equal energy white. This is defined as [x,y]=(0.33,0.33) in CIEXYZ color space and is analogous to the HSV white point at (0,0). However, other white points may be used, generally defined by "white" standard illuminants or a color temperature such as 6500 K.^[1]

Complementary wavelength

When the chromaticity lies within the triangle with vertices at the white point, spectral blue (~400 nm) and pure spectral red (~700 nm), the dominant wavelength is indeterminate because the point of intersection that is nearer to the chromaticity lies on the line of purples instead of the spectral locus. The colors on the line of purples cannot be defined by wavelength because they do not represent monochromatic light.^[1]

Instead, the dominant wavelength is replaced with the complementary wavelength, which will represent the complementary color. To calculate it, the point of intersection that is further from the chromaticity in question is used. If the nearer intersection is on the line of purples, the further intersection must be on the spectral locus.^[1]

Application

Dominant wavelength is used to define the color of light sources, such as the LEDs, that do not lie along the Planckian locus (which would otherwise be defined by color temperature). These light sources are also often described by their peak wavelength—the wavelength of highest radiometric spectral flux (highest peak in the power spectrum)—but the dominant wavelength is a photometric quantity, and therefore intuitively conveys what color the light will appear without relying on inexact color naming.^[5]

Related Research Articles

Color or colour is the visual perception based on the electromagnetic spectrum. Though color is not an inherent property of matter, color perception is related to an object's light absorption, reflection, emission spectra and interference. For most humans, colors are perceived in the visible light spectrum with three types of cone cells (trichromacy). Other animals may have a different number of cone cell types or have eyes sensitive to different wavelength, such as bees that can distinguish ultraviolet, and thus have a different color sensitivity range. Animal perception of color originates from different light wavelength or spectral sensitivity in cone cell types, which is then processed by the brain.

A set of primary colors or primary colours consists of colorants or colored lights that can be mixed in varying amounts to produce a gamut of colors. This is the essential method used to create the perception of a broad range of colors in, e.g., electronic displays, color printing, and paintings. Perceptions associated with a given combination of primary colors can be predicted by an appropriate mixing model that reflects the physics of how light interacts with physical media, and ultimately the retina.

<span class="mw-page-title-main">Hue</span> Property of a color

In color theory, hue is one of the main properties of a color, defined technically in the CIECAM02 model as "the degree to which a stimulus can be described as similar to or different from stimuli that are described as red, orange, yellow, green, blue, violet," within certain theories of color vision.

HSL and HSV are alternative representations of the RGB color model, designed in the 1970s by computer graphics researchers. In these models, colors of each hue are arranged in a radial slice, around a central axis of neutral colors which ranges from black at the bottom to white at the top.

<span class="mw-page-title-main">Chromaticity</span> Specification of color hue and saturation

Chromaticity is an objective specification of the quality of a color regardless of its luminance. Chromaticity consists of two independent parameters, often specified as hue (h) and colorfulness (s), where the latter is alternatively called saturation, chroma, intensity, or excitation purity. This number of parameters follows from trichromacy of vision of most humans, which is assumed by most models in color science.

The CIELAB color space, also referred to as L*a*b*, is a color space defined by the International Commission on Illumination in 1976. It expresses color as three values: L* for perceptual lightness and a* and b* for the four unique colors of human vision: red, green, blue and yellow. CIELAB was intended as a perceptually uniform space, where a given numerical change corresponds to a similar perceived change in color. While the LAB space is not truly perceptually uniform, it nevertheless is useful in industry for detecting small differences in color.

The RGB chromaticity space, two dimensions of the normalized RGB space, is a chromaticity space, a two-dimensional color space in which there is no intensity information.

Colorfulness, chroma and saturation are attributes of perceived color relating to chromatic intensity. As defined formally by the International Commission on Illumination (CIE) they respectively describe three different aspects of chromatic intensity, but the terms are often used loosely and interchangeably in contexts where these aspects are not clearly distinguished. The precise meanings of the terms vary by what other functions they are dependent on.

A color wheel or color circle is an abstract illustrative organization of color hues around a circle, which shows the relationships between primary colors, secondary colors, tertiary colors etc.

<span class="mw-page-title-main">Spectral color</span> Color evoked by a single wavelength of light in the visible spectrum

A spectral color is a color that is evoked by monochromatic light, i.e. either a spectral line with a single wavelength or frequency of light in the visible spectrum, or a relatively narrow spectral band. Every wave of visible light is perceived as a spectral color; when viewed as a continuous spectrum, these colors are seen as the familiar rainbow. Non-spectral colors are evoked by a combination of spectral colors.

<span class="mw-page-title-main">Planckian locus</span> Locus of colors of incandescent black bodies within a color space

In physics and color science, the Planckian locus or black body locus is the path or locus that the color of an incandescent black body would take in a particular chromaticity space as the blackbody temperature changes. It goes from deep red at low temperatures through orange, yellowish, white, and finally bluish white at very high temperatures.

A white point is a set of tristimulus values or chromaticity coordinates that serve to define the color "white" in image capture, encoding, or reproduction. Depending on the application, different definitions of white are needed to give acceptable results. For example, photographs taken indoors may be lit by incandescent lights, which are relatively orange compared to daylight. Defining "white" as daylight will give unacceptable results when attempting to color-correct a photograph taken with incandescent lighting.

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 this model is associated with a precise description of how the components are to be interpreted, taking account of visual perception, the resulting set of colors is called "color space."

The CIE 1931 color spaces are the first defined quantitative links between distributions of wavelengths in the electromagnetic visible spectrum, and physiologically perceived colors in human color vision. The mathematical relationships that define these color spaces are essential tools for color management, important when dealing with color inks, illuminated displays, and recording devices such as digital cameras. The system was designed in 1931 by the "Commission Internationale de l'éclairage", known in English as the International Commission on Illumination.

CIE standard illuminant D65 (sometimes written D₆₅) is a commonly used standard illuminant defined by the International Commission on Illumination (CIE). It is part of the D series of illuminants that try to portray standard illumination conditions at open-air in different parts of the world.

A standard illuminant is a theoretical source of visible light with a spectral power distribution that is published. Standard illuminants provide a basis for comparing images or colors recorded under different lighting.

In colorimetry, the CIE 1976L*, u*, v*color space, commonly known by its abbreviation CIELUV, is a color space adopted by the International Commission on Illumination (CIE) in 1976, as a simple-to-compute transformation of the 1931 CIE XYZ color space, but which attempted perceptual uniformity. It is extensively used for applications such as computer graphics which deal with colored lights. Although additive mixtures of different colored lights will fall on a line in CIELUV's uniform chromaticity diagram, such additive mixtures will not, contrary to popular belief, fall along a line in the CIELUV color space unless the mixtures are constant in lightness.

<span class="mw-page-title-main">Coloroid</span> Color space

The Coloroid Color System is a color space developed between 1962 and 1980 by Prof. Antal Nemcsics at the Budapest University of Technology and Economics for use by "architects and visual constructors". Since August 2000, the Coloroid has been registered as Hungarian Standard MSZ 7300.

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 or a digital representation. A color space may be arbitrary, i.e. with physically realized colors assigned to a set of physical color swatches with corresponding assigned color names, or structured with mathematical rigor. A "color space" is a useful conceptual tool for understanding the color capabilities of a particular device or digital file. When trying to reproduce color on another device, color spaces can show whether shadow/highlight detail and color saturation can be retained, and by how much either will be compromised.

References

1 2 3 4 5 6 Schanda, Janos (2007). Colorimetry : understanding the CIE system. [Vienna, Austria]: CIE/Commission internationale de l'eclairage. pp. 65–66. ISBN 978-0-470-04904-4.
↑ "Language of Light - Helmholtz Coordinates". Konica Minolta. Retrieved 16 September 2022.
↑ Commission internationale de l'éclairage (2004). "Chapter 5.1". Colorimetry. Vienna: Central Bureau of the CIE. ISBN 978-3-901906-33-6.
↑ Post, David L. (1997). "Color and human-computer interaction". In Helander, Martin G.; Landauer, Thomas K.; Prabhu, Prasad V. (eds.). Handbook of Human-Computer Interaction (2nd ed.). Burlington: Elsevier. pp. 583–584. ISBN 9780080532882.
↑ Sims, Paul. "What's the difference between peak wavelength and dominant wavelength?". Luminus Devices. Retrieved 16 September 2022.

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[schanda-1] 1 2 3 4 5 6 Schanda, Janos (2007). Colorimetry : understanding the CIE system. [Vienna, Austria]: CIE/Commission internationale de l'eclairage. pp. 65–66. ISBN 978-0-470-04904-4.

[KM-2] "Language of Light - Helmholtz Coordinates". Konica Minolta. Retrieved 16 September 2022.

[CIE15-3] Commission internationale de l'éclairage (2004). "Chapter 5.1". Colorimetry. Vienna: Central Bureau of the CIE. ISBN 978-3-901906-33-6.

[4] Post, David L. (1997). "Color and human-computer interaction". In Helander, Martin G.; Landauer, Thomas K.; Prabhu, Prasad V. (eds.). Handbook of Human-Computer Interaction (2nd ed.). Burlington: Elsevier. pp. 583–584. ISBN 9780080532882.

[5] Sims, Paul. "What's the difference between peak wavelength and dominant wavelength?". Luminus Devices. Retrieved 16 September 2022.

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