Unit of measure that corresponds to the photometric equivalent of a watt. It refers to the luminous lux (in other words the quantity of luminous energy emitted by a light source) visible by the human eye. In general, what relates the intensity with the lux (candela with lumen) is the angle of emission of light. To calculate the lumen/ candela conversion, you have to convert the radiation angle of the beam (supplied by the manufacturer in degrees) in a solid angle (unit of measure: steradians). Thus we can calculate, for instance, that a LED with an intensity of 2.4 cd and a diffusion angle of 120 ° will present a lux of about 7.5 lm.