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Preferred term

illuminance  

Definition

  • In photometry, illuminance is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. Similarly, luminous emittance is the luminous flux per unit area emitted from a surface. Luminous emittance is also known as luminous exitance. In SI units illuminance is measured in lux (lx), or equivalently in lumens per square metre (lm·m⁻²). Luminous exitance is measured in lm·m⁻² only, not lux. In the CGS system, the unit of illuminance is the phot, which is equal to 10000 lux. The foot-candle is a non-metric unit of illuminance that is used in photography. (Wikipedia, The Free Encyclopedia, https://en.wikipedia.org/wiki/Illuminance)

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http://data.loterre.fr/ark:/67375/MDL-JJHGPN78-7

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