CIE1931model

The CIE 1931 color space is a color space specified by the International Commission on Illumination in 1931. It was the first scientifically defined quantitative system for describing human color perception. The model is based on the tristimulus values X, Y, and Z, which represent the response of the three types of cone cells in the human eye. These values are not directly observable but are derived from the spectral power distribution of a light source and the CIE color matching functions.

The CIE 1931 color space is often visualized using a chromaticity diagram, which plots the chromaticity coordinates x and y. These coordinates are derived from the tristimulus values X, Y, and Z by normalizing them: x = X / (X + Y + Z) and y = Y / (X + Y + Z). The chromaticity diagram displays all the colors perceivable by the average human observer as a horseshoe-shaped region. The spectral colors lie along the curved boundary, and the non-spectral purple colors lie along the straight line connecting the ends of the spectrum.

The Y tristimulus value in the CIE 1931 model is often used as a measure of luminance, representing the perceived brightness of a color. The X and Z values contribute to the color's hue and saturation. The CIE 1931 color space serves as a foundational standard for color measurement and reproduction, influencing many other color spaces and color management systems. It provides a framework for objectively defining and comparing colors, crucial in fields such as photography, printing, and display technology.