Towards a New Colour Appearance Model for Self-luminous Stimuli

Abstract

Based on the experimental visual data obtained for self-luminous stimuli surrounded by a dark back- ground, a new colour appearance model (CAM) for unrelated self-luminous stimuli, CAM15u, was previ- ously developed. To extend the model to related self-luminous stimuli, the colour appearance of coloured self-luminous stimuli surrounded by a luminous background was evaluated using the magnitude estima- tion method. Experiments have been performed in Belgium and in Argentina using two different experi- mental setups. With a LED setup in the Belgian laboratory, visual data on the perception of brightness, hue and amount of white of 30 coloured self-luminous stimuli surrounded by a luminous background were collected. Luminance levels of the stimuli and the background were respectively 50 cd/m2 and 28 cd/m2 (positive contrast condition). With a projector setup in the Argentinian laboratory, visual data on the perception of brightness and amount of white of 32 coloured self-luminous stimuli surrounded by a lumi- nous background were collected. Luminance levels of the stimuli and the background were respectively 10 cd/m2 and 5.6 cd/m2 (positive contrast condition). For both experiments; the brightness scaling shows a clear and prominent Helmholtz–Kohlrausch effect. This effect describes the impact of the saturation of a stimulus on the perceived brightness and has been seriously underestimated in earlier CAMs. Both brightness, hue and amount of white are found to be well predicted by CAM15u, for this positive contrast condition.