CMC（l:c）公式是对相应CIELAB色差公式的修改。它有色差符号DEcmc。尽管CIELAB 1976 L*a*b*（CIELAB）方程式的使用为行业提供了一种“标准”方法来计算和传达试验的色差（见8.1），但人们认识到，CIELAB色差值（DE*）与视觉评估的相关性很差。缺乏相关性是由CIELAB颜色空间的不均匀性造成的（见图。 1). CMS（l:c）色差公式给出了视觉评估和仪器测量色差之间显著改善的相关性。通过CMC（l:c）方程得出的视觉色差报告和仪器色差报告之间的相关性改善，通常允许在大多数情况下，采用单个数字公差来判断颜色匹配的可接受性，而不管标准的颜色和任何试验的色差方向。 考虑了另一个等式CIE94，但它没有显示出比CMC有任何显著改善（见8.2）。CMC（l:c）公式以修改后的形式保留了将整体色差划分为亮度、色度和色调成分差异（见图2）的功能，这在CIELAB色差公式中是存在的。使用椭球半轴（lSL、cSc和SH）使CMC（l:c）方程适用于广泛的用途。

The CMC (l:c) formula is a modification of the corresponding CIELAB color-difference formula. It has color-difference symbol DEcmc. Even though use of CIELAB 1976 L*a*b* (CIELAB) equation provides industry with a "standard" means of calculating and communicating color differences of trials from their standards (see 8.1), it is recognized that CIELAB color difference values (DE*) correlate poorly with visual assessments. The lack of correlation is caused by the non-uniformity of CIELAB colorspace (see Fig. 1). Significantly improved correlation between visual assessments and instrumentally measured color differences is given by the CMS (l:c) color difference formula. The improvement in correlation between visual and instrumental color-difference reports yielded by the CMC (l:c) equation will usually permit the adoption of a single-number tolerance for judging the acceptability of a color match in most situations, regardless of both the color of the standard and the direction of the color difference of any trial from it. Another equation, CIE94 has been considered, but it has not shown any significant improvement over CMC (see 8.2).The CMC (l:c) formula retains, in modified form, the partitioning of overall color difference into differences in lightness, chroma, and hue components (see Fig. 2) which is present in the CIELAB color-difference formula. Using the ellipsoidal semi-axes (lSL, cSc, and SH) makes the CMC (l:c) equation suitable for a wide range of uses.