Frederic Ives Medal paper. History and current status of a physiologically based system of photometry and colorimetry.

The CIE chromaticity diagram, which has been in common use for more than 60 years, disguises essential relations among cone excitations that become transparent in a system developed with D. I. A. MacLeod and initially proposed by the author to the CIE in 1979. This proposal led to the formation of a CIE committee to consider an ideal version of the system, to be employed either as a supplement to, or an alternative for, the 1931 "standard observer". After 15 years, the task remains unfinished. The history of debate within the original committee and that of its successor (which is still active today) is briefly reviewed. Among cone fundamentals that might be chosen, a set derived and published by Stockman, MacLeod, and Johnson [J. Opt. Soc. Am. A 10, 2491 (1993)] is favored here, and some of the advantages for displaying visual data in a system based on these fundamentals are illustrated.