Colorimetrie

Colorimetry is the science and technology that quantifies human color perception by measuring and describing color stimuli using standardized color spaces and instruments. It aims to relate physical properties of light, such as spectral power distribution, to the way the human eye perceives color, enabling objective comparisons across devices, materials, and conditions.

Historically, colorimetry developed from the need to reproduce colors consistently. The International Commission on Illumination (CIE) defined a model based on a standard observer, using color matching functions that describe the average human eye response to light of different wavelengths. From these functions, the CIE XYZ color space was derived as a device-independent representation of color, with chromaticity coordinates (x, y) and luminance Y computed from X, Y, and Z.

Measurements are performed with colorimeters or spectrophotometers. A colorimeter often provides tristimulus values X, Y, Z (or equivalent RGB triplets) for a sample under a defined illuminant and geometry. The data can be converted to perceptual spaces such as CIE Lab or CIE Luv for color difference calculations (Delta E). These spaces support more uniform perceptual distances than raw tristimulus values.

Applications span display and printer calibration, color quality control in textiles and plastics, food color measurement, art conservation, and dermatology. Colorimetry must consider illumination, viewing geometry, metamerism, and device dependence. Device-dependent spaces (RGB) require color management to match different devices, while device-independent spaces (XYZ, Lab) enable cross-device color comparisons. Limitations include observer variability, metamerism, and measurement accuracy dependent on instruments and standard conditions.