A phot (ph) is a photometric unit of illuminance, or luminous flux through an area. It is not an SI unit but rather is associated with the older centimetre–gram–second system of units. The name was coined by André Blondel in 1921. Metric equivalence: Metric dimensions: Illuminance = luminous intensity × solid angle / length2 See also Illuminance Lumen (unit) Lux Photometry (optics) Light References External links Knowledgedoor, LLC (2005). Library of Units and Constants: Illuminance Quantity. Retrieved 2006-07-21. Illuminance Converter. Retrieved 2006-07-21. Units of illuminance Centimetre–gram–second system of units