Without light, objects are not visible at all; without shadows, only two-dimensional images are visible. Only the interplay of light and shadow gives objects the necessary depth; bodies, surfaces and structures can be easily recognized. At the same time, the right mix of light direction and shade ensures visual comfort and a pleasant lighting atmosphere. The direction of light is responsible for the formation of shadows. It is determined by the radiation characteristics of the luminaires and their arrangement in the room.

Ideal: combination of diffuse and directional light.

A bright room with only diffuse light without shadows looks monotonous and uncomfortable: objects and distances are difficult to recognize, orientation is difficult. In contrast, point light sources with extremely directional light form deep shadows with hard shadow edges. In these \"cast shadows\", almost nothing can be recognized. This can also create dangerous optical illusions, for example when handling tools or climbing stairs. According to DIN EN 12464-1, the ideal shadow effect - shadows with soft edges - consists of a balanced relationship between directional and diffuse lighting. For example, luminaires with indirect light components provide diffuse light, while downlights or direct-beam louvre luminaires for offices provide directional light.