User preferences for LED lighting in terms of light spectrum

Abstract

A study was carried out in light booths to investigate user preference for different light spectra. Twenty-one LED spectra and three fluorescent lamps, all at three different correlated colour temperatures were used for the study. Sixty observers evaluated the lit scenes under different spectra for naturalness of selected objects, colourfulness of a Macbeth Colour Checker Chart, and the visual conditions of the lighting booths. The observers preferred the spectral power distributions (SPD) under which the chroma and colourfulness values of the object colours were higher. The CIE Colour Rendering Index was not a good indicator of the observers' preference for the LED SPDs. It seemed that light sources with a higher CQS Gamut Area Scale and CQS Colour Preference Scale values were preferred by the observers as far as LED spectra were concerned. However, the CQS Gamut Area Scale calculated with a new version of the software (version 9.2) and the Gamut Area Index were suitable as indicators of observers' preference for both the LEDs and the fluorescent lamp spectra. Because chroma and colourfulness values of object colours influence the observers' preference, they should be considered as important factors for the selection of a colour preference index for light sources.

Light dominates colour preference when correlated colour temperature differs

“…Colour preference has been reported to be impacted by several contextual factors which include the lighting application 19,21 , regional cultural difference [22][23][24] , illuminance level 25,26 and age difference 27 . Such research has contributed to the development of light quality evaluation but has also highlighted new problems.…”

Effect of Window Glazing on Colour Quality of Transmitted Daylight

“…their chromaticity coordinates lie above the black body curve. Theoretically, this transmitted light will not be preferred by the user, as Dangol et al [31] and Islam et al [32] found that the observer preferred LED SPDs (spectral power distribution) with D uv values of the light sources were either negative or close to the black body locus. D uv values of light sources affect subjective preference.…”

“…Moreover, from the studies [31][32][33][34], it was clear that R9 is not an indicator of subjective preference. However, the chroma and colourfulness values of object colours calculated using CAM02-UCS have a great influence on the subjective preferences, especially for the naturalness and colourfulness (subjective measure).…”

Performance of different metrics proposed to CIE TC 1-91

“…Seven LED SPDs and one fluorescent lamp SPDs each at CCTs of 2700 K, 4000 K and 6500 K (altogether 24 different SPDs) were used in the experiment. Altogether 60 observers with normal visual acuity and colour vision participated in the experiment evaluating seven objects related to office environment: a coloured picture, a sample of wood, a smartphone, observers own hand, printed text, a Coke can and a Macbeth Colour checker (MCC) chart (for more details see Islam et al, 2013)). …”