Color Research and Application vol:36 issue:3 pages:192-200
The determination of the long-term memory colours of objects has been the subject of investigation for many years. Colour acceptance boundaries have been determined from the visual assessments of objects under variable illumination or by presenting manipulated images of objects on a calibrated computer display. However, a systematic and quantitative rating of the colour of real objects with respect to memory colour is not available at this moment. In this paper, nine familiar real objects with colours distributed around the hue circle, were positioned in a specially designed LED illumination box. For each object, approximately hundred real illumination spectra were synthesised in a random order keeping the luminance of the object approximately constant. Observers were asked to rate, on a five-point scale, the similarity of the perceived object colour to their idea of what the object looked like in reality. By avoiding specular reflections the observer was unable to identify any clues as to the colour of the illumination. For each object, similarity ratings showed a good intra- and inter-observer agreement. The ratings of all the observers were pooled and successfully modelled in IPT colour space by a bivariate Gaussian distribution. It was found that the chromaticity corresponding to the highest rating tended to be shifted towards higher chroma in comparison with the chromaticity calculated under D65 illumination. The bivariate distributions could be very useful in applications where the quantitative evaluation of the colour appearance of an object stimulus is required, such as in the evaluation of the colour rendering capabilities of a light source.