The different impressions produced by daylight can be imitated with artificial light. In situations where the natural light is insufficient, there is an opportunity for artificial light to make perception possible while creating the required atmosphere. This may mean projection using patterned light, directed or diffuse light or specific directions of light. So vis-à-vis sunlight and an overcast sky, there are spotlights, wallwashers, projectors and ceiling washlights.
The versatility of daylight with its constantly changing direction of light, changing colour of light as well as the change from diffuse to directed light continuously reveals the space in a new way. For instance, the low morning light casts long shadows that penetrate translucent structures and create a striking shadow pattern on the surfaces. If the contrast is strong, the pattern can dominate other visual information, as the light superimposes shadows as a layer over other objects and conceals their texture.
Patterns of light can be produced with artificial lighting by using spotlights fitted with gobos. The gobo design can reproduce the shapes made by shadows of leaves and cast a lively pattern of light on the surfaces. The contrasts result in the room appearing to be less uniform than with ambient lighting. Due to the striking pattern, the strong contrasts of light attract more attention than the sculpture in the centre of the room.
As the direction of light changes during the course of the day, the perception of buildings and objects changes and spatial elements, such as vertical surfaces, take on a different appearance. This property of light is based on directed light, which can create harsh shadows. Direct sunlight also causes a phenomenon whereby leaves appear to shine on the tree as luminescent elements. A characteristic feature of daylight is a brightness contrast that has much more brightness above the horizon than on the ground.
Artificial lighting which corresponds to sunlight can be replicated using luminaires that produce directed light, accentuate objects or add washlighting over surfaces. By then selecting the appropriate lamps or filters, the colour of light in the indoor area can be adapted to match cool daylight.
With an overcast sky, the shadows almost completely vanish and textures and shapes appear less three-dimensional.
A lighting scenario comparable to a day with a bright, diffuse sky can be produced either with ceiling washlights or a luminous ceiling. Each produces a very diffuse light with virtually no modelling which would have helped to reveal the shape.
In the intense light of a sunset, the colours of materials seem to change. However, our faculty of perceptual constancy enables us to appreciate that the material itself does not change colour compared with its daytime appearance. We know that it is just the light that has changed. The yellowish light enhances the warmth of the atmosphere and the shadows confirm that the sun is close to the horizon.
Dimming, colour control and various distributions of light allow the colour of light to be altered. When combined with a specific light distribution, the perceptual focus in the room can also be changed. The contrast in colour and in brightness matches the importance of the sculpture. The warm colours of the wallwashing and accent lighting replicate the warm atmosphere at sunset. However, using several luminaires casts multiple shadows and creates a contrast to the daylight, which has the sun as its only source. By using lighting control, the atmosphere can be adjusted to produce very different results and, in contrast to daylight, can be maintained producing a specific lighting effect.
