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. In SI derived units these are measured in \(lux (lx)\) or \(lumens per square metre\) (\(cd \cdot m^{-2}\)). In the CGS system, the unit of illuminance is the \(phot\), which is equal to \(10,000 lux\). The \(foot-candle\) is a non-metric unit of illuminance that is used in photography. (http://qudt.org/schema/qudt/LatexString)