SI unit of illuminance and luminous emittance (symbol lx) measures the intensity of light. One lux is one lumen of luminous flux of light incident on an area of one square meter.
Non-SI unit of illuminance and luminous emittance (symbol fc). One footcandle is one lumen of luminous flux of light incident on an area of one square foot. It is equivalent to 10.764 lux.
The unit of illuminance in CGS system (symbol oh). One phot is equal to 10,000 lux.
A unit of illumination used in Germany during World War II. It describes permitted levels of lighting during air raids. "Nox" is the Latin word for "nacht" - night. One nox equals 0.001 lux.
SI derived unit of illumination in other SI units (symbol ca·sr/m²).