Editing Color rendering index (section)

==R96<sub>a</sub> method==
[[File:CIE CRI TCS chromaticities.svg|300px|right]]

In the CIE's 1991 Quadrennial Meeting, Technical Committee 1-33 (Color Rendering) was assembled to work on updating the color rendering method, as a result of which the R96<sub>a</sub> method was developed. The committee was dissolved in 1999, releasing {{harvtxt|CIE|1999}}, but no firm recommendations, partly due to disagreements between researchers and manufacturers.<ref>"Authors' response to SA Fotios and JA Lynes" in {{harvtxt|Sándor|Schanda|2005}}: "The main message of our investigations is an answer to the lamp industry, who still use the colour rendering index and the lamp efficacy as parameters for optimizing their lamp spectra, and have turned down the work of CIE TC 1-33 by stating that there are not enough visual experiments showing the shortcomings of the CIE colour rendering calculation method."{{failed verification|date=September 2020}}</ref>

The R96<sub>a</sub> method has a few distinguishing features:{{sfnp|Bodrogi|2004|p=11|loc=Past research to improve the CRI}}

* [[#New test color samples|A new set of test color samples]]
* Six reference illuminants: D65, D50, [[black bodies]] of 4200 K, 3450 K, 2950 K, and 2700 K.
* A new chromatic adaptation transform: CIECAT94.
* Color difference evaluation in CIELAB.
* Adaptation of all colors to [[CIE Standard Illuminant D65|D65]] (since CIELAB is well-tested under D65).

It is conventional to use the original method; R96<sub>a</sub> should be explicitly mentioned if used.

===New test color samples===
{| class="wikitable floatright" border="1"
|-
! 
! TCS01<sup>*</sup>
! TCS02<sup>*</sup>
! TCS03<sup>*</sup>
! TCS04<sup>*</sup>
! TCS05<sup>*</sup>
! TCS06<sup>*</sup>
! TCS07<sup>*</sup>
! TCS08<sup>*</sup>
! TCS09<sup>*</sup>
! TCS10<sup>*</sup>
|-
| L<sup>*</sup> || 40.9 || 61.1 || 81.6 || 72.0 || 55.7 || 51.7 || 30.0 || 51.0 || 68.7 || 63.9
|-
| a<sup>*</sup> || 51.0 || 28.8 || −4.2 || −29.4 || −43.4 || −26.4 || 23.2 || 47.3 || 14.2 || 11.7
|-
| b<sup>*</sup> || 26.3 || 57.9 || 80.3 || 58.9 || 35.6 || −24.6 || −49.6 || −13.8 || 17.4 || 17.3
|- 
| style="height:25px;" |
| style="background:#ad3139;" |
| style="background:#d17e27;" |
| style="background:#e0cb08;" |
| style="background:#92be38;" |
| style="background:#369842;" |
| style="background:#0089a5;" |
| style="background:#413c95;" |
| style="background:#bb5593;" |
| style="background:#c99e89;" |
| style="background:#b7837d;" |
|}

As discussed in {{harvtxt|Sándor|Schanda|2005}}, {{harvtxt|CIE|1999}} recommends the use of a [[ColorChecker]] chart owing to the obsolescence of the original samples, of which only [[Metamerism (color)|metameric]] matches remain.<ref>[http://www.xrite.com/product_overview.aspx?ID=820&Action=Library X-Rite ColorChecker Chart].</ref> In addition to the eight ColorChart samples, two skin tone samples are defined (TCS09<sup>*</sup> and TCS10<sup>*</sup>). Accordingly, the updated general CRI is averaged over ten samples, not eight as before. Nevertheless, {{harvtxt|Hung|2002}} has determined that the patches in {{harvtxt|CIE|1995}} give better correlations for any color difference than the ColorChecker chart, whose samples are not equally distributed in a uniform color space.