illumination

Illumination refers to the deliberate provision or distribution of light to make objects and spaces visible. It encompasses natural daylight as well as artificial light and is concerned with the quantity, distribution, color, and quality of light reaching surfaces and observers. In professional practice, illumination design seeks to ensure visibility, safety, and comfort while managing energy use and the environmental impact of lighting systems.

Key photometric quantities include luminous flux (lumens), illuminance (lux), and luminance (candelas per square meter). Illuminance measures incident light on a surface, while luminance describes the brightness of a surface as perceived by the eye. Luminous intensity, CRI, and color temperature describe color characteristics. Luminous efficacy expresses how much light output is produced per unit of electrical power (lm/W).

Historically, illumination began with daylight and grew through candles, oil and gas lamps, and early electric lamps. The 20th century brought incandescent, fluorescent, and high-intensity discharge lighting; the 21st century has seen rapid adoption of light-emitting diodes and solid-state lighting, which offer greater efficiency and control. Daylighting remains an important strategy in architecture for reducing artificial energy use.

Design considerations include uniform lighting distribution, glare control, color rendering, and adaptability to tasks. Standards and guidelines from bodies such as the CIE and national authorities influence lumen levels, glare limits, color quality, and emergency lighting requirements. Applications span indoor spaces, street and outdoor illumination, photography and film, horticulture, and laboratory work.

Illumination science continues to integrate sensor networks, wireless controls, and daylight-responsive systems to optimize energy use and user experience.