User preferences for LED lighting in terms of light spectrum

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.