Luminaires come in many shapes and sizes. They are usually classified according to source, mounting, construction, application and/or by photometric characteristics.
These luminaires can provide general or ambient lighting with the added feature that some of the light can be emitted upward to produce some ceiling brightness, making the space look more open and larger. Lamps are often concealed behind glass or plastic diffusers or other types of lenses which help to reduce glare and distribute the light into the space below.
Recessed downlights are almost entirely hidden in the ceiling. The electrical components are contained in "housings" which conceal mechanical parts above the ceiling or behind the wall. A discrete aperture attaches to the housing, from which the light is directed into the room below. Recessed downlights often provide general or ambient lighting, but are also available as adjustable luminaires which may be used to deliver intense beams for accent lighting.
Recessed luminaires can be used to add subtle accent lighting while adding warm and dimension to living spaces.
Track lighting refers to a system that includes luminaires (track heads) and a track or rail that is designed to provide mounting and deliver power. Track systems can be used in homes or in a range of commercial applications. These adjustable luminaires can be moved anywhere along the track system. This provides the flexibility required for lighting dynamic displays in galleries, museums and retail stores.
Wallwash luminaires are used to produce a distribution of light that changes gradually from high levels at the top of the wall to lower levels at the bottom of the wall. Wall washers can be recessed, track mounted or surface mounted and are a common luminaire choice for perimeter lighting. These are very common in retail and other light commercial applications, as well as some residential applications.
Luminaire manufacturers generally provide spacing criteria required for the even distribution of light along the length of a wall or large vertical surface.