The old definition of this unit was based on blackbody radiation at the freezing point of platinum.
The old definition of this unit was based on blackbody radiation at the freezing point of platinum. This unit is based on a source of monochromatic radiation of frequency 5.4 times ten to the twelfth hertz and that has a radiant intensity in that direction of 1/683 watt per steradian. Luminance can be measured in this SI unit per square meter. Multiplying this unit by steradians gives the SI unit of luminous flux, the lumen, and multiplying this unit times steradians and dividing by square meters gives the SI unit of illuminance, the lux. Name this base SI unit.
The old definition of this unit was based on blackbody radiation at the freezing point of platinum.
candela [or standard candle]