Human perceptions of colour rendition vary with average fidelity, average gamut, and gamut shape

Abstract

An experiment was conducted to evaluate how subjective impressions of a light source’s colour quality depend upon the details of the shifts it causes in the colour appearance of illuminated objects. Twenty-eight participants each evaluated 26 lighting conditions in a 3.1 m by 3.7 m room filled with objects selected to cover a range of hue, saturation, and lightness. IES TM-30-15 Fidelity Index ( Rf) values ranged from 64 to 93, IES TM-30 Gamut Index ( Rg) values ranging from 79 to 117, and IES TM-30 red chroma shift ( Rcs,h1) values ranging from −19% to 26%. All lighting conditions had the same nominal illuminance and chromaticity. Participants were asked to rate each condition on eight point scales for saturated–dull, normal–shifted, and like–dislike, as well as classifying the condition as one of saturated, dull, normal, or shifted. The findings suggest that gamut shape is more important than average gamut area for modeling human preference, with red playing a more important role than other hues. Average fidelity alone is a weak predictor of human perception, especially CIE Ra. Nine of the top 12 rated products had a CIE Ra value of 73 or less, which indicates that the criteria of CIE Ra ≥ 80 may be excluding many preferred light sources.

Light dominates colour preference when correlated colour temperature differs

“…Considering the consistency among each trial as well as the results of related works 23,25,28 , such statistics seems to be reasonable.…”

“…It is clear that the gamut shape of these lights are quite similar, which obviously belies their huge difference in predicting colour preference. Therefore, it is very likely that such theory on gamut shape 21,28 may only validated in a metameric lighting domain. If two light sources have different CCTs, they will correlate to different reference lights and thus their gamut shapes are incomparable.…”

“…Some researchers invited the participants to perceive a single type of object under different lights, such as fruit and vegetables 2,9 , skin tones 38 , artworks 25,33 , printed images 36 , cosmetic products 10 , or consumer goods 4,11 . Meanwhile, in other contributions, groups of mixed objects were used 3,28,34 . ).…”

A color graphic informing on the impact of electric lighting and coated glazing in complex architectural scenes

“…These graphs show, in the a'b’ plane of CAM02‐UCS, the average color shifts of 99 samples divided into 16 hue bins (22.5° each). Since their publication, they have become the reference to test the hypothesis of psychophysical experiments and to illustrate experimental results …”

“…Since their publication, they have become the reference to test the hypothesis of psychophysical experiments and to illustrate experimental results. [25][26][27][28] All these graphical representations provide information on the magnitude of the color shift for a predefined set of samples, similar to the CIE special color rendering indices (CRI Ri). They also show the direction of the color shifts.…”