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 background,a new colour appearance model (CAM) for unrelated self-luminous stimuli, CAM15u, was previouslydeveloped. To extend the model to related self-luminous stimuli, the colour appearance of colouredself-luminous stimuli surrounded by a luminous background was evaluated using the magnitude estimationmethod. Experiments have been performed in Belgium and in Argentina using two different experimentalsetups. 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 werecollected. 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 theperception of brightness and amount of white of 32 coloured self-luminous stimuli surrounded by a luminousbackground were collected. Luminance levels of the stimuli and the background were respectively10 cd/m2 and 5.6 cd/m2 (positive contrast condition). For both experiments; the brightness scaling showsa clear and prominent Helmholtz-Kohlrausch effect. This effect describes the impact of the saturationof a stimulus on the perceived brightness and has been seriously underestimated in earlier CAMs. Bothbrightness, hue and amount of white are found to be well predicted by CAM15u, for this positive contrastcondition.