Resolution 5 of the 13th CGPM

SI unit of luminous intensity (candela)

The 13th Conférence Générale des Poids et Mesures (CGPM),


  • the definition of the unit of luminous intensity ratified by the 9th CGPM (1948) and contained in the "Resolution concerning the change of photometric units" adopted by the Comité International des Poids et Mesures in 1946 (PV, 20, 119) in virtue of the powers conferred by the 8th CGPM (1933),
  • that this definition fixes satisfactorily the unit of luminous intensity, but that its wording may be open to criticism,

decides to express the definition of the candela as follows:
"The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600 000 square metre of a black body at the temperature of freezing platinum under a pressure of 101 325 newtons per square metre."

reference The reader should note that the official version of this Resolution is the French text


This definition was abrogated by the 16th CGPM in 1979 (Resolution 3).

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