CRI2012: A proposal for updating the CIE colour rendering index

Abstract

The CIE colour rendering index (CRI) has been criticized for its poor correlation with the visual colour rendering of many spiked or narrowband sources, its outdated colour space and chromatic adaptation transform and the use of a small number of non-optimal reflectance samples that have enabled lamp manufacturers to tune the spectrum of a light source to yield, in some cases, inappropriately high general CRI values. The CRI2012 metric proposed in this paper addresses these criticisms by combining the most state of the art colorimetric colour difference model, i.e. CAM02-UCS, with a mathematical reflectance set that exhibits a highly uniform spectral sensitivity. A set of 210 real reflectance samples has also been selected to provide additional information on the expected colour shifts when changing illumination.

Colour fidelity for picture gallery illumination, Part 1: Determining the optimum light-emitting diode spectrum

“…16 The calculations show that the two sample sets show slightly different results, therefore in a subsequent paper the influence of real pigments, used by painters will be analysed. …”

“…At the time of writing this paper CIE TC 1-90 has not selected a new colour fidelity test method but one of the candidate methods is the CRI2012 model 16 that overcomes most of the problems of the current CIE test method, 10 and uses modern colorimetry. For museum lighting there are some further aspects that have to be considered.…”

“…The authors used the reference illuminants as described in the CIE publication 10 for their calculations. For testing the proposed colour fidelity optimisation program two sets of test samples have been used: the 15 saturated sample spectra recommended by Davis and Ohno in their CQS metric 23 and the 17 mathematical samples designed by Smet and Whitehead 16,25 for the CRI2012 metric.…”

Measuring, simulating and optimizing current LED phosphor systems to enhance the visual quality of lighting

“…This suitability means the ability to provide a white tone of good visual quality (with Δu'v' wtq ≤ 0.002 [15]) and a good general color rendering index (with Ra ≥ 86 [16]). To try to do so, two green phosphors and two red-orange phosphors were used: LuAG #2 (see Section LuAG) with a broad spectral emission curve (green 1, G1), an orthosilicate (green 2, G2) [Ba, Sr, Ca] 2 SiO 4 :Eu, a red-orange oxyorthosilicate (red 1, R1) [Sr, Ba]Si 3 O 5 : Eu and a red-orange nitride phosphor (red 2, R2).…”

“…Note that, for a more comprehensive, up-to-date analysis of the color renderingcolor quality issue, not only the general color rendering index but also a set of object specific color rendering indices shall be considered [15] but this is out of the scope of this article. Also note that the CIE CRI color rendering index computation method is currently being modernized in the CIE. A new color rendering index has been developed [16] as it has not been officially endorsed by the CIE at the time of writing, it is not dealt with in this paper. Warm white LEDs (2700 K, 3000 K) were obtained by adding a high amount of redorange phosphor to the mixture.…”