the candela is the luminous intensity, in a given direction, of a source which emits monochromatic rays with a frequency of 540 x 1012 hertz and whose energy intensity in that direction is 1/683 watt per steradian, 1 kandela on valgustugevus, millega teatavas kindlas sihis kiirgab 540 x 10 12-hertsise sagedusega monokromaatilise kiirguse allikas, kui tema kiirgustugevus selles sihis on 1/683 W/sr