Brightness appearance of self‐luminous stimuli on a non‐uniform background

Abstract

AbstractColor appearance models (CAM) generate a set of visual correlates attributed to a stimulus such as hue, brightness, and saturation. However, most of their applicability is limited to stimuli perceived on a uniform background. Additionally, when focusing on brightness, multiple studies have been performed to model the mechanisms of brightness perception of a stimulus on a non‐uniform background. In this paper, experimental data are gathered and the insights of both approaches are combined. The influence of adding a neutral ring‐shaped luminous area in the background of a neutral circular stimulus has been investigated via a series of psychophysics experiments. The ring is presented at three luminance levels (90, 335, 1200 cd/m2) with three thicknesses (0.33, 0.67, and 1.00 cm) at four angular distances to the edge of the stimulus (1.2°, 6.4°, 11.3° and 16.1°). It is observed that when the ring is closer to the stimulus, the brightness inhibition becomes larger; obviously, the impact is also related to the ring's area and luminance. Inspired by the classical CAM, the cone excitations corresponding to the stimulus and the background are inserted in a compression‐adaptation formula to obtain a cone response proportional to the perceived brightness. The semi‐saturation constant occurring in this formula is modelled as a function of the cone excitation, the distance and the width of the ring. The results are overall promising, yet the model shows some shortcomings and more complex weighting functions might be needed. In the future, image‐based approaches should get more attention.