The Uniform Chromaticity Scale Diagram (UCS) is a modified version of the CIE 1931 chromaticity diagram , designed to improve perceptual uniformity. It is primarily used in color science, lighting, and imaging technology to represent colors visually and mathematically.
Why a UCS diagram?
The original CIE 1931 (x,y) chromaticity diagram has non-uniform color perception , meaning that equal distances on the diagram do not always correspond to equal visual differences. The UCS diagram corrects this by aligning the color distances more closely with human perception.
Main UCS diagrams:
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CIE 1960 (u,v) chromaticity diagram
- Developed as an improvement on CIE 1931.
- Used in colorimetric studies, but still had some non-uniform properties.
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CIE 1976 (u',v') chromaticity diagram (most commonly used)
- A further improvement on the 1960 diagram.
- u' = 4x / (x + 15y + 3z) and v' = 9y / (x + 15y + 3z) .
- Used in modern color standards such as sRGB, HDR, and lighting design.
- Provides better perceptual uniformity, especially for color accuracy in displays and lighting.
Applications of the UCS diagram:
- Color management in displays and printing technology .
- Lighting and LED color characterization .
- Evaluation of color differences in industrial applications .
- Research into color perception and color models such as CIELAB .