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Rationale of Color Quality Scale



Yoshihiro Ohno, Wendy L. Davis


The color quality of solid state lighting (SSL) products is critical and is the subject of increasing attention. The CIE Color Rendering Index (CRI) [1] has been widely used for many years. However, the CRI is 35 years old and various problems of the CRI when used for light- emitting diode (LED) sources have been identified, as reported in many publications [2-7]. In particular, the report from CIE Technical Committee TC 1-62 “Color rendering of white LED light sources” [8] summarizes several problems of the CRI when applied to white LED sources. The problem is that the CRI score does not correlate well with visual evaluation in many cases. In response to the conclusions of TC 1-62, a technical committee TC 1-69 (Color rendition by white light sources, Chair: Wendy Davis) was established in 2006 to develop and recommend a new CIE metric. The new metric is intended to eventually replace the CRI, though not immediately. It should work well for both traditional lighting technologies and SSL sources. At NIST, we have developed the Color Quality Scale (CQS) [9,10], which addresses the problems of the CRI for SSL sources yet maintains good consistency in score with the CRI for traditional sources, and proposed it to TC 1-69. The CQS spreadsheet has been distributed to many users in the SSL industry and continues to gain support in the USA. However, the CQS is currently not gaining good support in the technical committee (TC), and the TC is inclined to adopt a different metric, which is a pure fidelity metric very similar to CRI. The traditional lamp industry also has concerns that the concept of CQS deviates from CRI. We are afraid that another pure fidelity metric will not solve the problems for SSL sources, and we believe a new concept metric as CQS is needed for the SSL industry.
Website of U.S. Department of Commerce


color quality, color rendering, color rendering index, light emitting diodes, solid-state lighting


Ohno, Y. and Davis, W. (2010), Rationale of Color Quality Scale, Website of U.S. Department of Commerce, [online], (Accessed April 16, 2024)
Created June 10, 2010, Updated June 7, 2017