Perceptual psychology is a branch of science concerned with the various aspects of visual perception, especially neural reception and the processing of sensory stimuli. To comprehend optical perception, the process of building up visual impressions is of particular importance. Apparent 'mistakes' enable an analysis of the modes of action and objectives of perception.
On the one hand we have constancy phenomena. Constant objects generate images of different shape, size and brightness distribution on the retina due to changes in e.g. lighting, distance or perspective. The mechanisms of constancy perception compensate for these deviating retinal images.
Before objects are assigned properties, they must first be recognised, i.e. distinguished from their surroundings. From the process of interpretation, laws of shape perception can be formulated, according to which particular arrangements are grouped into figures or objects. The laws of shape
are also of practical interest to lighting designers: each lighting installation consists of an arrangement of luminaires, be these on the ceiling, on the walls or within the space. However, such arrangements are not perceived directly but organised into figures according to the rules of shape perception. The surrounding architecture and lighting effects of the luminaires create further patterns integrated into the perception.