frame|right|Dominant/complementary wavelength example on the CIE color space<br>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 approximating a color's hue. Along with purity, it makes up one half of the Helmholtz coordinates. The dominant wavelength of a given color is defined to be the wavelength of monochromatic spectral light that lies on the straight line passing through the white point and the given colour in the chromaticity diagram.
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 HSV color space. The radial coordinate is the purity, which is analogous to saturation of the HSV color space.
Color space
Not all color spaces can be used for determining the dominant wavelength of a color, because in most approximately perceptually uniform color spaces (such as CIELAB, Oklab, CIECAM02, etc) two colors with the same hue can have slightly different dominant wavelengths. Unless otherwise stated, the CIE 1931 color space (CIEXYZ) is used., but the CIELUV color space is sometimes used. If the line intersects with the line of purples and not the spectral locus, the complementary wavelength is used. The purity can then be calculated as defined here.
See also
- Hue
- Colorfulness
- White point