Quality of the light sources and colour constancy

Abstract

Different strategies are suggested to update the Colour Rendering Index (CRI). Two experiments have been conducted to analyse the effect of different lights on the appearance of colours, with the assumption that the extent of relevant colour differences depends on the different hues. The first experiment starts from the concept of unique hues and analyses the constancy or variations of unique hues under different real light sources. The second experiment deals with colour difference and allows to evaluate local distortions of the colour space. Analysed sources include incandescent lamp, a simple realisation of D65 and three white LEDs. The samples used in the experiments are three dimensional to reproduce more realistic viewing conditions. The results show that the methods used in this research are effective in highlighting the colour variations induced by the different light sources without the need of direct comparisons by the same observer, and avoid the bias due to memory processes typical of other methodologies. They could be the basis for the improvement of the CRI.