Color rendering index: Difference between revisions

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The value often quoted as "CRI" on commercially available lighting products is properly called the CIE R_a value, "CRI" being a general term and CIE R_a being the international standard color rendering index.

Numerically, the highest possible CIE R_a value is 100 and would only be given to a source whose [[spectrum]] is identical to standardized[[Solar spectrum|the spectrum of daylight]], orvery close to that of a [[black body]] (incandescent lamps are effectively black bodies), dropping to negative values for some light sources. [[Low-pressure sodium light]]ing has a negative CRI; [[fluorescent lightslight]]s range from about 50 for the basic types, up to about 98 for the best multi-phosphor type. Typical white-color [[LEDs]] have a CRI of 80 or more, while some manufacturers claim that their LEDs haveachieve achieveda CRI of up to 98.<ref>{{Cite web |url=http://www.ledengin.com/files/products/LZC/LZC-00GW00.pdf |title=LZC-00GW00 Data Sheet |date=March 16, 2015 |website=ledengin.com |publisher=LED ENGIN |archive-url=https://web.archive.org/web/20170105235216/http://www.ledengin.com/files/products/LZC/LZC-00GW00.pdf |archive-date=January 5, 2017 |url-status=dead}}</ref>

CIE R_a's ability to predict color appearance has been criticized in favor of measures based on [[color appearance model]]s, such as [[CIECAM02]] and for [[daylight]] simulators, the CIE [[metamerism index]].<ref>{{citation |first2=János |last2=Schanda |first1=Norbert |last1=Sándor |journal=Lighting Research and Technology |volume=38 |issue=3 |title=Visual colour rendering based on colour difference evaluations |date=September 1, 2006 |pages=225–239 |doi=10.1191/1365782806lrt168oa |s2cid=109858508}}.<br />Conference version of this article:<br />{{citation |first2=János |last2=Schanda |first1=Norbert |last1=Sándor |title=Visual colour-rendering experiments |journal=AIC Colour '05: 10th Congress of the International Colour Association |year=2005 |pages=511–514 |url=http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/521.pdf |url-status=dead |archive-url=https://web.archive.org/web/20110721114551/http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/521.pdf |archive-date=2011-07-21}}</ref> CRI is not a good indicator for use in visual assessment, especially for sources below 5000&nbsp;[[kelvin]] (K).<ref>{{citation