Illuminance Illuminance (also know as luminous emittance or luminous flux per area), is the total luminous flux incident on a surface, per unit area. It is a measure of the intensity of the incident light, wavelength-weighted by the luminosity function to correlate with human brightness perception. Photometry QUDT http://qudt.org/vocab/quantity#Illuminance ODM2 Units Type Controlled Vocabulary ODM2 Working Group A vocabulary for describing the type of the Unit or the more general quantity that the Unit represents.