Colour Measurement Committee CMC

AG (now Datacolor International) software. Finally, the Colour Measurement Committee (CMC) of the Society of Dyers and Colourists in the United Kingdom made some compromises and published a formula based on the J P Coates work but incorporating the CIELAB coordinates [53], This was made a British standard (BS 6923) and soon was adopted by textile associations around the world. The usefulness of such an equation has been demonstrated many times in the textile industry and in some papers from manufacturers of textured, molded polypropylene as well. 

There are other minor nonequivalencies of ISO test procedures compared to ASTM standards, but for color difference the ISO Test Procedure No. 105 is unique. Those who use Colour Measurement Committee (CMC) procedures—particularly CMC 2 1 Lightness to Color ratio—claim that it facilitates a uniform description for acceptability decisions that is better than any other system in existence. These equations permit the use of a single number tolerance, DEcmc, in a nearly uniform color space. The CMC formula is a modification to the perceptibility CIELAB formula. It is fully described elsewhere in this book, but it deserves some brief notice here because, after all, it is an ISO procedure. The CMC developed the basic British Standard No. 6923, Calculation of Small Color Differences. Soon afterward, in 1989, the American Association of Textile Chemists and Colorists (AATCC) adopted AATCC Test Method 173, CMC Calculation of Small Color Differences for Acceptability. Ford Motor Company indicated a preference for using CMC 2 1 ratio color difference for plastics weathering data for plastics interior trim materials. 

In 1994 following extensive studies by the Colour Measurement Committee (CMC) the CIE94 total colour-difference was defined. In the equation, lightness, chroma and hue are weighted and corrected to account for variation in perceived colour magnitude and for sensitivity and variation in experimental conditions. Recently, the most prominent UK workers in the area of colour equation development combined under a technical committee to determine a generalised and reliable formula (Luo et al. 2000). They have also come up with an equation... 

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