Luminance gradients and colour appearance

Investigations of luminance-gradient effects can be classified into two lines of research. The first explores the direct effects of luminance gradients on colour appearance, while the second explores how the colours of surfaces are indirectly influenced by other surfaces that are directly affected by luminance gradients. Studies of direct luminance-gradient effects concentrate on the role of shaded edges on the perception of shadows, on colour and texture appearance, and on phenomenal glare. Studies of indirect luminance-gradient effects focus on how the spatial arrangement of luminance gradients affects lightness and brightness, and can be classified in two ways. One is primarily concerned with understanding and modelling the perceptual mechanisms that determine colour appearance by manipulating different kinds of luminance gradients. The other is mainly concerned with the relationship between luminance gradients and perceived illumination measured by judging lightness and brightness as a function of articulation and the spatial organisation of luminance gradients. New experimental evidence in constancy-type conditions provide additional evidence that luminance gradients play an important role in the perception of illumination even with conflicting edge information.