IEVref:112-02-10ID:
Language:enStatus: Standard
Term: candela
Synonym1:
Synonym2:
Synonym3:
Symbol: cd
Definition: SI unit of luminous intensity, equal to the luminous intensity in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 Hz and has a radiant intensity in that direction of 1/683 W/sr

Note 1 to entry: The definition in the SI Brochure is: "The candela, symbol cd, is the SI unit of luminous intensity in a given direction. It is defined by taking the fixed numerical value of the luminous efficacy of monochromatic radiation of frequency 540 × 1012 Hz, Kcd, to be 683 when expressed in the unit lm W−1, which is equal to cd sr W−1, or cd sr kg−1m−2 s3, where the kilogram, metre and second are defined in terms of h, c and ΔνCs."

Note 2 to entry: This definition implies that 683 lm/W is the exact value of the luminous efficacy of monochromatic radiation Km.

Note 3 to entry: The candela is one of the seven SI base units: second (s), metre (m), kilogram (kg), ampere (A), kelvin (K), mole (mol) and candela (cd).


Publication date:2020-12
SourceSI Brochure, 9th edition, 2019, 2.3.1, modified – The definition in the SI Brochure has been revised to comply with the IEV rules. Notes 1 to 3 to entry have been added.
Replaces:112-02-10:2010-01
Internal notes:2020-12-10: Correction to Note 1 to entry: "minus" deleted in "monochromatic radiation of frequency 540 × 10−12 Hz". The French is already correct. JGO
CO remarks:
TC/SC remarks:
VT remarks:
Domain1:
Domain2:
Domain3:
Domain4:
Domain5: