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It is a truth, universally ignored, that a single metric of color rendering must be in want of another. Evidence presented here, together with those from an earlier study, strongly suggest that the quest for a single metric to quantify color rendering will be in vain. Rather, the strengths of color rendering index (CRI) and of gamut area index (GAI) y seem to counteract the weaknesses of one another, such that together they can be used to guide lighting practitioners in choosing a source that will provide good color rendering of most objects in most applications. The present study was conducted to determine whether sources, both warm and cool, with high levels of both CRI (above 80) and GAI (above 80 and less than 100) were judged better than ones with high levels of just CRI or just GAI. The results support the conclusion that a two-metric system of color rendering is needed for general illumination applications.

White is a color sensation absent hue. Manufacturers describe practical light sources used for illumination as tinted warm‐white or cool‐white, but these informal designations do not seem to be based upon measured human color perceptions of white illumination. This article describes the results of a series of psychophysical experiments that more precisely measured subjective perceptions of white illumination from light sources of different correlated color temperatures (CCTs). Generally, perceptions of untinted white illumination for sources with high CCTs (above 4000 K) are associated with chromaticities that fall above the blackbody locus. In contrast, perceptions of untinted white illumination for sources with low CCTs (below 4000 K) are associated with chromaticities that lie well below the blackbody locus. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2013

This study set out to understand the benefits of improved illuminance uniformity in parking lots in terms of user perception and acceptability, as well as energy use, and to demonstrate that light-emitting diodes (LEDs) can achieve uniform distributions more efficiently than traditional light sources. The results from a field evaluation showed that more uniform illuminance distributions are favourably perceived by people in terms of goodness of illumination, ability to see around and at a distance, and perception of safety – all of this at a much lower average horizontal illuminance. Thus, improving uniformity alone can translate into lower energy use and potential for less glare and light pollution. Optical modelling showed that LEDs have a much greater potential to efficiently produce uniform illuminance distributions than larger light sources such as high pressure sodium or metal halide.

Lighting plays an important role in supporting retail operations, from attracting customers, to enabling the evaluation of merchandise, to facilitating the completion of the sale. Lighting also contributes to the identity, comfort, and visual quality of a retail store. With the increasing availability and quality of white LEDs, retail lighting specifiers are now considering LED lighting in stores. The color rendering of light sources is a key factor in supporting retail lighting goals and thus influences a light source's acceptance by users and specifiers. However, there is limited information on what consumers' color preferences are, and metrics used to describe the color properties of light sources often are equivocal and fail to predict preference. The color rendering of light sources is described in the industry solely by the color rendering index (CRI), which is only indirectly related to human perception. CRI is intended to characterize the appearance of objects illuminated by the source and is increasingly being challenged because new sources are being developed with increasingly exotic spectral power distributions. This paper discusses how CRI might be augmented to better use it in support of the design objectives for retail merchandising. The proposed guidelines include the use of gamut area index as a complementary metric to CRI for assuring good color rendering.

The lighting industry relies on colour-rendering index (CRI) and correlated colour temperature (CCT) to communicate the colour properties of light sources. While advances have been made in recent years to develop new metrics for colour rendering, not much attention has been given to the validity or utility of CCT for communicating the appearance of illumination. Recently, it was shown that a wide range of chromaticities can appear 'white' or with minimal perceived 'tint'. Importantly, these chromaticities do not follow the line of blackbody radiation, the reference for CCT. The present study builds on this previous research to determine whether 'white' illumination is preferred in simulated residential applications. Results presented here support the hypothesis that people prefer 'white' or minimally 'tinted' sources of illumination.

No abstract

Recently, a line of minimum tint in chromaticity space for sources of illumination of different correlated color temperatures (CCTs) from 2700 K to 6500 K has been reported. This line of minimum tint did not correspond to the line of blackbody radiation implicitly associated with sources of white illumination used in architectural applications. It was noted that chromaticities along the line of minimum tint were not metamers but, rather, should represent, for a given CCT, chromaticities where the neural signals from the two spectral opponent channels were minimized. Earlier work provided a theoretical framework for representing the four unique hues where the neural signals from one spectral opponent channel are minimized. This framework was used here to quantitatively represent the line of minimum tint and then to empirically test whether this representation could predict the amount of tint perceived in six different sources of "white" Illumination." Based on these results, a provisional model is proposed for describing the tint and the amount of tint perceived in "white" Illumination used in architectural applications. V