Illumination or lighting is playing a huge role in environment design in which the deliberate application of light to achieve some aesthetic or practical effect. Lighting includes use of both artificial light sources such as lamps and natural illumination of interiors from daylight. Day lighting (through windows, skylights, etc.) is often used as the main source of light during daytime in buildings given its low cost.
Lighting represents a major component of energy consumption, accounting for a significant part of all energy consumed worldwide. Artificial lighting is most commonly provided today by electric lights, but gas lighting, candles, or oil lamps were used in the past, and still are used in certain situations. Proper lighting can enhance task performance or aesthetics, while there can be energy wastage and adverse health effects of poorly designed lighting. Indoor and outdoor lighting is a form of fixture or furnishing, and a key part of environmental design. Lighting can also be an intrinsic component of landscaping.
With the development of high efficiency and high power light-emitting diode (LED) it has become possible to incorporate LED in lighting and illumination. Replacement light bulbs have been made as well as dedicated fixtures and LED lamps. LED are used as street lights and in other architectural lighting where color changing is used. The mechanical robustness and long lifetime is used in automotive lighting on cars, motorcycles and on bicycle lights.
Lighting is classified by intended use as general, localized, or task lighting, depending largely on the distribution of the light produced by the fixture.
Task lighting is mainly functional and is usually the most concentrated, for purposes such as reading or inspection of materials. For example, reading poor-quality reproductions may require task lighting levels up to 1500 lux (150 foot-candles), and some inspection tasks or surgical procedures require even higher levels.
Accent lighting is mainly decorative, intended to highlight pictures, plants, or other elements of interior design or landscaping. General lighting fills in between the two and is intended for general illumination of an area. Indoors, this would be a basic lamp on a table or floor, or a fixture on the ceiling. Outdoors, general lighting for a parking lot may be as low as 10-20 lux (1-2 foot-candles) since pedestrians and motorists already used to the dark will need little light for crossing the area.
There are various method of lighting we can use today such as down lighting which is most common, with fixtures on or recessed in the ceiling casting light downward. This tends to be the most used method, used in both offices and homes. Although it is easy to design it has dramatic problems with glare and excess energy consumption due to large number of fittings.
Up lighting is less common, often used to bounce indirect light off the ceiling and back down. It is commonly used in lighting applications that require minimal glare and uniform general luminance levels. Up lighting (indirect) uses a diffuse surface to reflect light in a space and can minimize disabling glare on computer displays and other dark glossy surfaces. It gives a more uniform presentation of the light output in operation. However indirect lighting is completely reliant upon the reflectance value of the surface. While indirect lighting can create a diffused and shadow free light effect it can be regarded as an uneconomical lighting principal.
Front lighting is also quite common, but tends to make the subject look flat as its casts almost no visible shadows. Lighting from the side is the less common, as it tends to produce glare near eye level. Backlighting either around or through an object is mainly for accent.