In terms of illumination, how is lighting measured?

Lighting is measured in foot-candles, which quantifies the amount of light received on a surface area from a light source. This measurement takes into account both the intensity of the light and the area over which the light is distributed, specifically describing how much light illuminates a specific surface. A foot-candle is defined as the illumination produced when a uniform light source of one candle is present on a surface that is one foot away from the source, measuring the light intensity as it relates to distance. This makes foot-candles particularly useful in assessing adequate lighting levels for safety, comfort, and visibility in various environments.

Other units of measurement like watts, lumens, and candelas focus on different aspects of lighting: watts measure power consumption of the light source, lumens measure the total quantity of visible light emitted by a source, and candelas indicate the intensity of light in a particular direction. Therefore, while these other measures are relevant in the context of lighting, foot-candles specifically address the practical application of how light impacts surfaces in terms of illumination.