The V(Λ) function accepted in 1924 is valid for photopic vision. It was long recognized that for para-foveal vision this function does not describe luminance perception correctly. In 1964 the CIE accepted a large field colorimetric observer, but this system had no photometric counterpart. Subsequent research has shown that y10(Λ) function can be used as the spectral luminous efficiency function of a 10° photometric observer. The present report provides guidance when and how this large field photometric observer could be used, especially if luminance has to be determined para-foveally.

Based on the detailed evaluation of the available literature data TC 1-59 came to the conclusion that the adoption of a 10° photopic photometric observer [V10(Λ)] can be recommended to the CIE and that this system should be based - according to the original recommendations of the CIE Colorimetric Committee - on the y10(Λ) function of the CIE 1964 standard colorimetric observer.

The report is written in English, with a short summary in French and German. It consists of 23 pages with 3 tables.