Measuring colour rendering—A new approach

This paper presents a method of measuring a coloured sample giving numbers which correlate highly with the appearance of the sample when it is viewed under a defined illuminant. It is shown how these numbers, relating to the hue, lightness, and chroma of the sample, can be combined to provide a measure of the differences between a set of coloured samples viewed first under a reference lamp and then under a test lamp. Four hue/chroma/lightness indices are calculated for each of the four unique hues, red, yellow, green, and blue. These indices are combined to give mean hue, chroma, and lightness indices, and an overall index. This final index may be considered analogous to the present CIE colour rendering index.