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The CIE 1976 color difference formula is the first formula that related a measured color difference to a known set of CIELAB coordinates. This formula has been succeeded by the 1994 and 2000 formulas because the CIELAB space turned out to be not as perceptually uniform as intended, especially in the saturated regions.
The CIELAB color space, also referred to as L*a*b*, is a color space defined by the International Commission on Illumination (abbreviated CIE) in 1976. [a] 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.
Illuminant E is not a black body, so it does not have a color temperature, but it can be approximated by a D series illuminant with a CCT of 5455 K. (Of the canonical illuminants, D 55 is the closest.) Manufacturers sometimes compare light sources against illuminant E to calculate the excitation purity. [26]
The CIE XYZ color space was deliberately designed so that the Y parameter is also a measure of the luminance of a color. The chromaticity is then specified by the two derived parameters x and y , two of the three normalized values being functions of all three tristimulus values X , Y , and Z : [ 14 ] [ further explanation needed ]
The CIE 1931 colour space chromaticity diagram with wavelengths in nanometers.The colors depicted depend on the color space of the device on which the image is viewed.. The International Commission on Illumination (usually abbreviated CIE for its French name Commission internationale de l'éclairage) is the international authority on light, illumination, colour, and colour spaces.
Colorimetry is "the science and technology used to quantify and describe physically the human color perception". [1] It is similar to spectrophotometry, but is distinguished by its interest in reducing spectra to the physical correlates of color perception, most often the CIE 1931 XYZ color space tristimulus values and related quantities.
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
J e,ν [nb 6] watt per square metre per hertz W⋅m −2 ⋅Hz −1: M⋅T −2: Radiosity of a surface per unit frequency or wavelength. The latter is commonly measured in W⋅m −2 ⋅nm −1. This is sometimes also confusingly called "spectral intensity". J e,λ [nb 7] watt per square metre, per metre W/m 3: M⋅L −1 ⋅T −3: Radiant ...