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The Color Quality Scale



Wendy L. Davis, Yoshihiro Ohno


The Color Rendering Index (CRI) has been shown to have deficiencies when applied to white light-emitting diode (LED) based sources. Further, evidence suggests that the restricted scope of the CRI unnecessarily penalizes some light sources with desirable color qualities. To solve the problems of the CRI and include other dimensions of color quality, the Color Quality Scale (CQS) has been developed. While the CQS uses many of elements of the CRI, there are a number of fundamental differences. Like the CRI, the CQS is a test samples method that compares the appearance of a set of reflective samples when illuminated by the test lamp to their appearance under a reference illuminant. The CQS uses a larger set of reflective samples, all of high chroma, and combines the color differences of the samples with a root-mean-square. Additionally, the CQS does not penalize light sources that cause increases in the chroma of object colors, but does penalize sources with smaller rendered color gamut areas. The scale of the CQS is converted to span zero to 100 and the uniform object space and chromatic adaptation transform used in the calculations are updated. Supplementary scales have also been developed for expert users.
Optical Engineering


colorimetry, color rendering, light-emitting diodes


Davis, W. and Ohno, Y. (2010), The Color Quality Scale, Optical Engineering (Accessed June 21, 2024)


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Created March 15, 2010, Updated January 9, 2018