Interactive effect of illuminance and correlated colour temperature on colour preference and degree of white light sensation for Chinese observers

The aim of this study was to explore the interactive effect of Illuminance (E) and Correlated Colour Temperature (CCT) on the visual appreciation of the colour rendition of lighting (termed as colour preference), as well as on a newly defined visual attribute termed the degree of white light sensation, which describes the Chinese understanding on a loosely-defined but widely-used concept: 'white light'. Thirty E-CCT combinations, that included six E values from 50 lx to 1800 lx and five CCT values from 2500 K to 6500 K, were used to illuminate a pair of highly coloured Jiaozhi artefacts, as well as the neutral space of an empty light booth. Thirty observers, fifteen males and fifteen females, were invited to take part in the visual experiments to rate the colour preference and the white light sensation. The results indicated that both E and CCT significantly influenced both visual attributes. For colour preference, the impact of E was greater while for the degree of white light sensation, stronger influence of CCT was observed. Based on the psychophysical results, the existing metrics that are used to evaluate the colour preference of E-CCT combinations were validated and a new model was proposed to characterize the degree of white light sensation. In addition, gender difference was investigated and it was found that male and female observers behaved similarly in assessing white light but unlike male observer, female observers did not prefer light sources with the highest degree of white light sensation.