DeltaE2000

DeltaE2000, also known as CIEDE2000, is a color-difference metric designed to quantify perceptual differences between colors in the CIE L*a*b* color space. Developed to improve upon the earlier CIE76 (ΔE*ab) formula, it provides better correlation with human vision across a range of colors, including variations in lightness, chroma, and hue. The formula was published in 2001 by Gaurav Sharma, Wen-Yong Wu, and Arun N. Patel and has since been adopted by the CIE as the standard CIEDE2000 method.

The calculation of DeltaE00 involves several steps and introduces perceptual weighting functions for lightness (SL), chroma (SC), and hue (SH), as well as a rotation term RT to account for cross-coupling between chroma and hue in certain color regions. Colors are first converted to CIE L*a*b*. Differences in lightness, chroma, and hue are computed, with a corrected hue difference to handle angular wrap-around. A set of weighting factors, typically with kL, kC, and kH equal to 1 for standard viewing conditions, scales these components. The final DeltaE00 value is obtained from a square-root combination of the weighted components, including the RT term that adjusts for uneven perceptual sensitivity in some hues.

DeltaE2000 is widely used in color quality control, printing, textiles, digital imaging, and color management to assess color fidelity between samples and references. While it generally provides improved perceptual accuracy over ΔE*ab, it is not perfect for all conditions, and differences in lighting or observer conditions can affect results. A DeltaE00 near 1.0 is often cited as a just-noticeable difference under standard viewing conditions.