lighting

Lighting is the use of light to illuminate spaces for visibility, safety, and ambience. It includes daylight, which is natural illumination, and artificial light produced by electrical sources. Lighting design considers quantity, distribution, color, and control to support tasks and mood while managing energy use.

Key quantities describe light in human terms. Luminous flux, measured in lumens, expresses total light output; illuminance, in lux, is lumens per square meter on a surface. Luminance describes brightness as seen by the eye. Color characteristics are described by color temperature (kelvin) and color rendering index (CRI). Efficacy, measured in lumens per watt, indicates efficiency.

Lighting technology has evolved from flame and gas to electric sources. Major categories include incandescent, fluorescent, high-intensity discharge (HID), and light-emitting diode (LED) lighting, with organic LEDs (OLEDs) expanding some applications. Modern lighting often employs controls—dimmers, occupancy and daylight sensors, and networked systems—that adjust output in response to task needs and daylight availability.

Applications span residential, commercial, industrial, and outdoor settings. Design aims to ensure adequate visibility, avoid glare, render colors faithfully, and minimize skyglow and energy use. Lighting can affect health and circadian rhythms; some designs incorporate warmer color temperatures at night. Standards address safety, performance, and energy codes, guiding calculations of lighting power density, uniformity, and flicker limits.