Spectral energy distribution of the International Commission on illumination light sources A, B and C

Standard light sources A, B, and C were adopted by the International Commission on Illumination (C.I.E.) in 1931 for the colorimetry of materials. Source A is an incandescent lamp operated at 2854°K. Sources B and C, representative of average noon sunlight and average daylight, respectively, are produced by passing radiant flux from source A through specified Davis-Gibson filters described in Bureau of Standards Miscellaneous Publication M114 (1931).The C.I.E. published relative energy data only from 370 to 720 mµ. The present paper gives data for these sources in the ultraviolet and extends the data in the red to 780 mµ. The new data were reported through the U. S. Secretariat Committee to the C.I.E. at its 1951 meeting. The values in the ultraviolet were reported to the Optical Society of America at its March, 1952, meeting.