Comparison of perceived chromatic differences with colorimetric colour-differences for colour chips with constant value and hue

Abstract

In order to study the perceptual scaling of chroma, perceived chroma-differences of colour chips are subjectively estimated by means of ratio estimation method under standard illuminant A and daylight D65. The subjectively estimated values are compared with their colorimetric colour-differences in the CIE 1976 L*u*v* and L*a*b* uniform colour spaces. The set of colour chips used in the experiment consists of eight hues (5R, 5YR, 5Y, 7.5GY, 3.5G, 10BG, 2.5PB and 5RP) with constant vlue 6, and chromas are form 0.3 to 13.7 at intervals of about 0.5 in the Munsell renotation system. Results obtained are summarized as follows:(1) Relative values of perceived colour-differences change little even when the illuminant is changed from the daylight D65 to the illuminant A, and the constancy of perceived colour-difference holds as well as in the case of hue-difference.(2) Colorimetric chroma-differences in the L*u*v* and L*a*b* spaces generally do not change much when the illuminant is changed.But, because of the insufficient compensation of chromatic adaptation, those of colours of 3.5G in both spaces change slightly.(3) Except for colours of 5Y and 3.5G, relative values of perceived colour-differences to colorimetric ones tend to become small generally with the increase in saturation.(4) For colours of 5Y and 7.5GY, the correlation between perceived colour-differences and colorimetric ones is slightly low in both colour spaces irrespective of the illuminant.