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Numerically, the highest possible CIE R<sub>a</sub> 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 }}</ref>
CIE R<sub>a</sub>'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
| last1 = Guo
| first1= Xin
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| pages = 183–199
| doi = 10.1191/1365782804li112oa
}}</ref><ref name="CIE1995">{{citation
|author = CIE
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{{harvtxt|Smet|2011}} reviewed several alternative quality metrics and compared their performance based on visual data obtained in nine psychophysical experiments. It was found that a geometric mean of the GAI index and the CIE Ra correlated best with naturalness (r=0.85), while a color quality metric based on memory colors (MCRI<ref>Smet K. A. G., Ryckaert W. R., Pointer M. R., Deconinck G., Hanselaer P. Colour Appearance Rating of Familiar Real Objects. Colour Research and Application 2011; 36(3):192–200.</ref>) correlated best for preference (''r'' = 0.88). The differences in performance of these metrics with the other tested metrics (CIE Ra; CRI-CAM02UCS; CQS; RCRI; GAI; geomean (GAI, CIE Ra); CSA; Judd Flattery; Thornton CPI; MCRI) were found to be statistically significant with ''p'' < 0.0001.<ref>Smet K. A. G., Ryckaert W. R., Pointer M. R., Deconinck G., Hanselaer P. [http://www.opticsinfobase.org/view_article.cfm?gotourl=http%3A%2F%2Fwww.opticsinfobase.org%2FDirectPDFAccess%2F3AAAA211-C63E-79CC-4E0A0772E17419BA_212731.pdf%3Fda%3D1%26id%3D212731%26seq%3D0%26mobile%3Dno&org= Correlation between color quality metric predictions and visual appreciation of light sources].</ref>
Dangol, et al., performed psychophysical experiments and concluded that people's judgments of naturalness and overall preference could not be predicted with a single measure, but required the joint use of a fidelity-based measure (e.g., Qp) and a gamut-based measure (e.g., Qg or GAI.).<ref>{{
Due to the criticisms of CRI many researchers have developed alternative metrics, though relatively few of them have had wide adoption.
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* {{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}}
* {{citation|first=K.A.G.|last=Smet|title=Correlation between color quality metric predictions and visual appreciation of light sources|journal=[[Optics Express]]|year=2011|volume=19|issue=9|pages=8151–8166 |doi=10.1364/oe.19.008151|pmid=21643065|bibcode=2011OExpr..19.8151S|doi-access=free}}
* {{citation|first1=R.|last1=Dangol|first2=M.|last2=Islam|first3=M.|last3=Hyvärinen|first4=P.|last4=Bhusal |first5=M.|last5=Puolakka|first6=L.|last6=Halonen|title=Subjective preferences and colour quality metrics of LED light sources |journal=Lighting Research and Technology|volume=45|issue=6|pages=666–688|date=December 2013 |issn=1477-1535|doi=10.1177/1477153512471520
* {{citation|first1=M.S.|last1=Islam|first2=R.|last2=Dangol|first3=M.|last3=Hyvärinen|first4=P.|last4=Bhusal |first5=M.|last5=Puolakka|first6=L.|last6=Halonen|title=User preferences for LED lighting in terms of light spectrum |journal=Lighting Research and Technology|volume=45|issue=6|pages=641–665|date=December 2013 |issn=1477-1535|doi=10.1177/1477153513475913
* {{cite journal |last1=Baniya |first1=R.R. |last2=Dangol |first2=R. |last3=Bhusal |first3=P. |last4=Wilm |first4=A. |last5=Baur |first5=E. |last6=Puolakka |first6=M. |last7=Halonen |first7=L. |year=2015| title=User-acceptance studies for simplified light-emitting diode spectra
* {{cite journal |last1=Dangol |first1=R. |last2=Islam |first2=M. |last3=Hyvärinen |first3=M. |last4=Bhusal |first4=P. |last5=Puolakka |first5=M. |last6=Halonen |first6=L. |year=2015| title=User acceptance studies for LED office lighting: Preference, naturalness and colourfulness |journal=Lighting Research and Technology |volume=47 |issue=1| pages=36–53 |doi= 10.1177/1477153513514424
* {{cite journal |last1=Islam |first1=M. |last2=Dangol |first2=R. |last3=Hyvärinen |first3=M. |last4=Bhusal |first4=P. |last5=Puolakka |first5=M. |last6=Halonen |first6=L. |year=2013| title=User acceptance studies for LED office lighting: lamp spectrum, spatial brightness and illuminance level
==External links==
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