Levels of Brightness Perception

Abstract

Much can be learnt about how we perceive brightness and lightness from the errors we make when doing so. Brightness and lightness perception involve a number of mechanisms operating at different levels of visual processing. One mechanism is low-level, and processes spatial variations in brightness via multiscale filtering. It serves to achieve lightness constancy with respect to the ambient level of illumination. However, it comes at a cost: errors such as simultaneous brightness contrast. A second, mid-level mechanism aims to achieve lightness constancy with respect to spatially varying illumination such as shading, shadows, highlights and transparency. The cost in this case is an enhancement of errors in brightness judgement.