The CRI‐CAM02UCS colour rendering index

Abstract

A new colour rendering index, CRI‐CAM02UCS, is proposed. It predicts visual results more accurately than the CIE CIR‐Ra. It includes two components necessary for predicting colour rendering in one metric: a chromatic adaptation transform and uniform colour space based on the CIE recommended colour appearance model, CIECAM02. The new index gave the same ranks as those of CIE‐Ra in the six lamps tested regardless the sample sets used. It was also found that the methods based on the size of colour gamut did not agree with those based on the test‐sample method. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2012

Categorical color constancy under RGB‐LED light sources

“…The general color rendering index R a of the LED lamp, calculated by using 8 samples recommended by CIE, 42 was 30. This value is close to that of the RGB-LED supplied by the Zumtobel Group (R a 5 31), which was used in a previous study, 38 lower than those of 5 RGB-LED lamps (R a 5 33-56) in Discussion part, and a little higher than F IG UR E 1 Schematic diagram illustrates the viewing geometry FIGU RE 2 Normalized spectral power distributions of the neutral, red, green, blue, and yellow illuminants produced by the LED lamp. The color of each curve corresponds to the color of the illuminant it indicates.…”

“…The color rendering index of the RGB-LED was much lower than that (Ra 5 70-99) of a broad band fluorescent lamp, a white phosphor LED or the LED lamp consisting of several LEDs. 37,38 Under a lighting system with such a low color rendering index, color constancy performance was initially expected to be extremely poor. However, the results reveal that the color constancy was generally good for all color categories under red and green illuminants.…”

“…The reason for the existence of color constancy under RGB-LED lamps is explained by the fact that a 3 narrow band light can increase red-green saturation and red-green color contrast compared to daylight illuminant, as reported by McCann et al 31 as well as other researchers. [38][39][40]58 The RGB-LED lamp used by Li et al, 38 which peaked at approximately 453, 515, and 630 nm and has a rendering index CIE-R a of 31 was found to elongate the color gamut in the directions of red and green. In 2 other studies, 39,40 the RGB-LED lamps had peak wavelengths at approximately 450, 520, and 635 nm (CIE-R a 5 22) 39 and at approximately 452, 527, and 644 nm (CIE-R a 5 23).…”

“…It has been reported, however, that the RGB-LED has a much lower color rendering index than other LED-based light sources, such as the MB-LED and fluorescent lamps. 38,39 Furthermore, the color discrimination capability under an RGB-LED light source is worse than that under other LED-based light sources, 39 as well as that under fluorescent and tungsten halogen lamps. 40 Conversely, it is determined that the RGB-LED produces a larger color gamut than the reference illumination 38,40 and that the RGB-LED light source is more often preferred regardless of its lower color rendering index.…”

The impact of LED lighting parameters on viewing fine art paintings

“…Only the data from nine illuminants having d uv ¼ 0 were analysed. The results showed that the values of the preference-based CRIs such as gamut area index, 21 memory colour rendering index 22 and feeling of contrast index 23 are all significantly (p50.01) affected by CCT in the present experimental setting, in which gamut area index and feeling of contrast index had a negative relationship to the fidelity-based CRIs such as CRI-CAM02UCS, 24 CRI2012, 25 the colour quality scale 26 as well as CIE-R a . It was found that the lower CIE-R a lighting conditions were Figure 9 The components of the factor analysis plotted in the rotated space and forming two factors, 'visibility' (dots) and 'warmth' (diamond) Spearman correlation coefficient to the factor visibility CIE-Ra 0.633 Figure 11 The Spearman correlation coefficients between the various CRIs and the factor 'visibility.…”