Color rendering index: Difference between revisions

Revision as of 03:52, 30 May 2022

Revision as of 20:03, 15 August 2022

Line 6:

[[File:AmbientLED.png|thumb|upright=1.35|right|Color rendering index shown as color accuracy]]

A '''color rendering index''' ('''CRI''') is a quantitative measure of the ability of a [[light source]] to reveal the [[color]]s of various objects faithfully in comparison with a natural or standard light source. Light sources with a high CRI are desirable in color-critical applications such as [[Neonatal nursing|neonatal care]]<ref>{{Cite web |title=Neonatal intensive care unit lighting: Update and Recommendations |url=https://www.researchgate.net/publication/305334032}}</ref> and [[Conservation and restoration of cultural property|art restoration]]. It is defined by the [[International Commission on Illumination]] (CIE) as follows:<ref>{{cite web |url=http://www.cie.co.at/publ/abst/17-4-89.html |title=CIE 17.4-1987 International Lighting Vocabulary |access-date=2008-02-19 |archive-url=https://web.archive.org/web/20100227034508/http://www.cie.co.at/publ/abst/17-4-89.html |archive-date=2010-02-27 |url-status=dead}}</ref>

<blockquote>

Line 16:

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 [[Solar spectrum|the spectrum of daylight]], very 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 light]]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 achieve a 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 of light sources, especially for sources below 5000&nbsp;[[kelvin]] (K).<ref>{{citation

| last1 = Guo

| first1= Xin

Line 43:

|archive-url = https://web.archive.org/web/20080103162323/http://www.cie.co.at/publ/abst/13-3-95.html

|archive-date = 2008-01-03

}}

|url-status = dead

}}

(A verbatim re-publication of the 1974, second edition. Accompanying disk [http://www.cie.co.at/publ/abst/d008.html D008: Computer Program to Calculate CRIs]. {{Webarchive|url=https://web.archive.org/web/20080327023340/http://www.cie.co.at/publ/abst/d008.html |date=2008-03-27 }})</ref> New standards, such as the [[IES TM-30]], resolve these issues and have begun replacing the usage of CRI among professional lighting designers.<ref>Illuminating Engineering Society. 2018. ''IES Method for Evaluating Light Source Color Rendition, IES Technical Memorandum (TM) 30-18''.</ref> However, CRI is still common among household lighting products.

Line 53 ⟶ 52:

Around the middle of the 20th century, color scientists took an interest in assessing the ability of [[artificial light]]s to accurately reproduce colors. European researchers attempted to describe illuminants by measuring the [[spectral power distribution]] (SPD) in "representative" spectral bands, whereas their North American counterparts studied the [[colorimetric]] effect of the illuminants on reference objects.<ref>American approach is expounded in {{harvtxt|Nickerson|1960}}, and the European approach in {{harvtxt|Barnes|1957}}, and {{harvtxt|Crawford|1959}}. See {{harvtxt|Schanda|Sándor|2003}} for a historical overview.</ref>

The [[International Commission on Illumination|CIE]] assembled a committee to study the matter and accepted the proposal to use the latter approach, which has the virtue of not needing [[spectrophotometry]], with a set of [[Munsell color system|Munsell]] samples. Eight samples of varying hue would be alternately lit with two illuminants, and the color appearance compared. Since no color appearance model existed at the time, it was decided to base the evaluation on color differences in a suitable color space, [[CIE 1964 color space|CIEUVW]]. In 1931, the CIE adopted the first formal system of [[colorimetry]], which is based on the trichromatic nature of the [[human visual system]].<ref name="Color rendering: Beyond pride and prejudice - Rea - 2010 - Color Research &amp; Application - Wiley Online Library" >{{cite journal |last1=Rea |first1=M. S. |last2=Freyssinier |first2=J. P. |title=Color rendering: Beyond pride and prejudice |journal=Color Research and Application |year=2010 |volume=35 |issue=6 |pages=401–409 |doi=10.1002/col.20562}}</ref><ref>{{cite magazine |title=Background |magazine=Guide to Light and Color in Retail Merchandising |volume=8 |issue=1 |date=March 2010 |page=5 |publisher=Alliance for Solid-State Illumination Systems and Technologies |url= http://www.lrc.rpi.edu/programs/solidstate/assist/pdf/AR-ColorGuideforRetailLighting-March2010.pdf}}</ref> CRI is based upon this system of colorimetry.<ref>{{cite web |last1=Rea |first1=M. |last2=Deng |first2=L. |last3=Wolsey |first3=R. |date=2004 |work=NLPIP Lighting Answers |title=Light Sources and Color |___location=Troy, NY |publisher=Rensselaer Polytechnic Institute |url=http://www.lrc.rpi.edu/nlpip/publicationDetails.asp?id=901&type=2 |access-date=2010-06-17 |archive-url= https://web.archive.org/web/20100611200908/http://www.lrc.rpi.edu/nlpip/publicationDetails.asp?id=901&type=2 |archive-date=2010-06-11 |url-status=dead}}</ref>

To deal with the problem of having to compare light sources of different correlated color temperatures (CCT), the CIE settled on using a reference [[black body]] with the same color temperature for lamps with a CCT of under 5000&nbsp;K, or a phase of CIE [[standard illuminant]] D (daylight) otherwise. This presented a continuous range of color temperatures to choose a reference from. Any chromaticity difference between the source and reference illuminants were to be abridged with a von Kries-type [[chromatic adaptation transform]]. There are two extent versions of CRI: the more commonly used R_a of {{harvtxt|CIE|1995}} (actually from 1974) and R96_a of {{harvtxt|CIE|1999}}.

Line 470 ⟶ 469:

| archive-url = https://web.archive.org/web/20140903072219/http://www.gtc.org.uk/tlci-results.aspx

| archive-date = 2014-09-03

| url-status = dead

}}</ref> Some manufacturers say that their products have TLCI values of up to 99.<ref>

{{cite web

Line 482 ⟶ 480:

== Sources ==

<!-- Harvard citations used. Please do not correct "colour" to color in the references and quotes. -->

* {{citation|author=CIE |series=Publication 135/2|year=1999|url=http://cie.kee.hu/newcie/publ/abst/135-99.html|title=Colour rendering (TC 1-33 closing remarks) |isbnwebsite=3-900734-97-6|publisher=CIECommission internationale Centralde Bureaul'éclairage |___location=Vienna|access-date=2008-07-16 |archive-url=https://web.archive.org/web/20080922013149/http://cie.kee.hu/newcie/publ/abst/135-99.html|archive-date=2008-09-22|url-status=dead}}

* {{citation|author=CIE |title=CIE Colorimetric and Colour Rendering Tables |yearwebsite=2004|series=[http://www.colour.org/tc8-04/Data/Render.txtCommission Diskinternationale D002,de Rell'éclairage |year=2004 1.3] |url=http://www.cie.co.at/publ/abst/d002.html |access-date=2008-02-16 |archive-url=https://web.archive.org/web/20080305120337/http://www.cie.co.at/publ/abst/d002.html|archive-date=2008-03-05|url-status=dead}}

* {{citation|author=CIE |series=Publication 177:2007|year=2007|url=http://www.slg.ch/pdf/publikation177.pdf |title=Colour rendering of white LED light sources|isbn=978-3-901906-57-2 |publisher=CIE Central Bureau |___location=Vienna |via=Schweizer Licht Gesellschaft |isbn=978-3-901906-57-2}}{{Dead link|date=January 2019 |bot=InternetArchiveBot |fix-attempted=yes }}. Carried out by TC 1-69: color Rendering of White Light Sources.

* {{citation|title=Band Systems for Appraisal of Color Rendition|journal=[[JOSA]]|volume=47|issue=12|date=December 1957|first=Bentley T.|last=Barnes|pages=1124–1129|doi=10.1364/JOSA.47.001124|bibcode=1957JOSA...47.1124B}}

* {{citation|first=Peter|last=Bodrogi|contribution=Colour rendering: past, present(2004), and future |year=2004|title=CIE Expert Symposium on LED Light Sources|pages=10–12 |url=http://cie2.nist.gov/LED_Sympo_2004/CIE_LED_symp04_prog_abstr.pdf|access-date=2008-07-18|archive-url=https://web.archive.org/web/20110721055141/http://cie2.nist.gov/LED_Sympo_2004/CIE_LED_symp04_prog_abstr.pdf|archive-date=2011-07-21|url-status=dead}}

* {{citation|title=Measurement of color rendering tolerances|first=Brian Hewson|last=Crawford|journal=[[JOSA]]|date=December 1959|volume=49|issue=12|pages=1147–1156|doi=10.1364/JOSA.49.001147|bibcode=1959JOSA...49.1147C}}

* {{citation|url=http://physics.nist.gov/Divisions/Div844/facilities/vision/color.html |first1=Wendy |last1=Davis |first2=Yoshi |last2=Ohno |date=December 2006 |title=Color Rendering of Light Sources |publisher=[[NIST]] |url-status=dead |archive-url=https://web.archive.org/web/20090825230627/http://physics.nist.gov/Divisions/Div844/facilities/vision/color.html |archive-date=August 25, 2009 }}

* {{cite conference |mode=cs2 |chapter=Sensitivity metamerism index digital still camera |volume=4922 |title=Proceedings of the SPIE: Color Science and Imaging Technologies |editor=Dazun Zhao |editor2=Ming R. Luo |editor3=Kiyoharu Aizawa |date=September 2002 |pages=1–14 |doi=10.1117/12.483116 |first=Po-Chieh |last=Hung |bibcode=2002SPIE.4922....1H}}

* {{citation|title=Light sources and color rendering|first=Dorothy|last=Nickerson|journal=[[JOSA]]|date=January 1960|volume=50|issue=1|pages=57–69|doi=10.1364/JOSA.50.000057|bibcode=1960JOSA...50...57N}}

* {{cite conference |title=Optical metrology for LEDs and solid state lighting |last=Ohno |first=Yoshi |series=Fifth Symposium Optics in Industry |year=2006 |book-title=Proceedings of SPIE: Fifth Symposium Optics in Industry |volume=6046 |pages=604625-1–604625-8 |editor=E. Rosas |editor2=R. Cardoso |editor3=J.C. Bermudez |editor4=O. Barbosa-Garcia |url=http://www.nist.gov/manuscript-publication-search.cfm?pub_id=840989 |doi=10.1117/12.674617 |bibcode=2006SPIE.6046E..25O}}

* {{citation|first1=Nicolas|last1=Pousset|first2=Gael|last2=Obein|first3=Annick|last3=Razet|title=Visual experiment on LED lighting quality with color quality scale colored samples|journal=Proceedings of CIE 2010 : Lighting Quality and Energy Efficiency, Vienna, Austria|year=2010|pages=722–729 |url=http://nicolas.pousset.pagesperso-orange.fr/Recherche/Article/CQS.pdf}}

* {{citation|first=János|last=Schanda|contribution=The concept of colour rendering revisited|title=First European Conference on Color in Graphics Imaging and Vision|___location=Poitiers, France|date=April 2–5, 2002 |url=http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/462.pdf|archive-url=https://web.archive.org/web/20110721113839/http://www.knt.vein.hu/staff/schandaj/SJCV-Publ-2005/462.pdf |url-status=dead|archive-date=July 21, 2011}}

* {{cite conference |first1=János |last1=Schanda |first2=Norbert |last2=Sándor |year=2003 |title=Colour rendering, past – present – future |pages=76–85 |conference=International Lighting and Colour Conference, Cape Town, South Africa, Nov 2–5, 2003}}

* {{citation|first=William A.|last=Thornton|title=Color-Rendering Capability of Commercial Lamps|journal=[[Applied Optics]]|year=1972|volume=11|issue=5|pages=1078–1086|doi=10.1364/AO.11.001078|pmid=20119099|bibcode=1972ApOpt..11.1078T}}