Nit (unit symbol nt) is a unit of the light density. The word derives from Latin “nitere”: to shine. Nit is another expression for Candela per square meter. Candela (lat. candle) is an SI unit for light intensity. The light density of an area determines with what brightness the eye witnesses this area; it has a direct reference to the optical sensory perception. The human eye can realize a light density of a maximum of 20,000 cd/m2.