Abstract. An experimental determination of the maximum spectral luminous efficacy of radiation has been made. The method uses luminous intensity standard lamps calibrated in "World mean candela 1952", thermopiles calibrated by absolute radiometers of electrical substitution type and filters of which the spectral transmittance is approximately proportional to the relative spectral luminous efficiency. An average value of 683 lm/W has been obtained, and the result is compared with that obtained at the NPL.

Print publication: Issue 4 (October 1975)
Received 27 January 1975