International Commission on Illumination R 1 - 43 Standard Deviate Observer Report

Observer metamerism was investigated in two colour matching settings. One was the classical large-field bipartite field matching with the use of narrow-band lights. The other was the cross-media setup typical for soft-proofing, with the use of reflective stimuli and two types of computer monitors. In the first experiment, five observers made repeated maximum saturation colour matches with a 6° bipartite field, and one observer made similar matches with a 2° field. Variability of colour matching functions within our group of observers was very similar to the variability within the Stiles and Burch colour matching dataset. In the second experiment, eleven observers made repeated cross-media colour matches between two computer displays and surface colour stimuli. Observer metamerism is shown to be an insignificant factor in the variability of colour matches in all colours except neutrals. The properties of distribution of individual judgements suggest that the precision of cross-media colour matches is governed by thresholds of colour discrimination, thus it can be modelled well by advanced colour difference formulae with suitably adjusted parametric coefficients. As the result of our findings, we conclude that: 4 1. Additional colour matching data is not required for successful modelling of observer metamerism. Stiles and Burch colour matching dataset for 2 and 10 degrees viewing field provide a reliable and repeatable data for such modelling. 2. Most importantly: Observer metamerism can not be assumed to govern the individual differences in matches in conditions different from quasisymmetric colour matching. Thus, any model based on variability of colour matching functions alone cannot account for variability of colour matching in real-world situations. Recommendation to the CIE We do not recommend investing more resources in the study of variability of quasisymmetric colour matching, and into the development of the Standard Deviate Observer in its present form. Rather, we recommend investing into gaining new knowledge of the practical effect of variations in colour vision in real life situations and, perhaps, forming a CIE Technical Committee on the subject.