NIST proposes replacement for LED color rendering index (CRI)

Gaithersburg, MD--The National Institute of Standards and Technology (NIST) issued a paper dated June 8, 2010 by Yoshi Ohno and Wendy Davis with the purpose to solicit comments from the solid-state lighting (SSL) industry on the Color Quality Scale (CQS) being developed by NIST as a replacement for the Color Rendering Index (CRI). NIST says that the CQS is being discussed as one of the proposals in the International Commission on Illumination (CIE) Technical Committee (TC) 1-69 and final discussions are in progress in the TC toward selecting a new metric. NIST adds that since the SSL industry is not well represented in the TC, it hopes to convey the opinions of the SSL industry to the committee members.

The paper goes on to say that the color quality of SSL products is critical and is the subject of increasing attention and although the CIE CRI has been widely used for many years, the index is 40 years old and various problems with the CRI when used for light-emitting diode (LED) sources have been identified, as reported in many publications; in general, NIST says the CRI score does not correlate well with visual evaluation in many cases.

Fixing the problems of the CRI is critical for the SSL industry, says NIST. Although traditional lamp companies have known about the problems of CRI for a long time and have found ways to work around these problems, the SSL industry is young and consists of numerous small companies that often do not have expert knowledge on color rendering and colorimetry. NIST says they tend to design products that simply maximize the lumens per watt and the score of the color rendering metric. As products are optimized for the metrics, standards are important.

The paper, which explains CQS metrics, can be viewed at http://apps1.eere.energy.gov/buildings/publications/pdfs/ssl/cqs_rationale_06-10.pdf and opinions and comments can be sent to [email protected].

SOURCE: LIGHTimes Online; http://www.solidstatelighting.net/news/?date=2010-06-17&id=119404

--Posted by Gail Overton; [email protected]; www.laserfocusworld.com