Solid color measurement

Color Difference Equations for Solid Colors

It is now almost 100 years since, in 1931, the CIE Yxy chromaticity color space was defined by the "International Commission on Illumination (CIE)". To overcome its limitations of not being uniform, the CIE recommended two alternate color spaces since then: CIELAB (or CIE 1976 L*a*b*) and CIELUV (or CIE L*u*v*). They are based on the opponent color theory of color vision, which says that two colors cannot be both green and red at the same time, nor blue and yellow at the same time. During the last years developments of new color difference equations and color spaces were carried out. Their goal was to improve the correlation between visual perception and instrumentally measured values. Additionally, they wanted to permit the use of a single number tolerance for all colors.

The basic building blocks of color measurement

Visual color perception is influenced by our individual color preferences, which are dependent on personal factors (mood, age, gender etc.), environment (lighting, surrounding etc.) as well as our ability to communicate color and color differences. A color looks different in the department store (cool white fluorescent lighting) than at home (warm, incandescent lighting). In order to guarantee consistent color and appearance under all possible circumstances, it is essential to standardize light source, observer and understand the spectral remission data of the object. This information will be the basis for calculation of colorimetric data as it is used for color communication and color QC in production.