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Title: Colour discrimination as a function of observer adaptation
Author: Pointer, Michael Richard
Awarding Body: University of London
Current Institution: Imperial College London
Date of Award: 1972
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A piece of apparatus was built to measure the size of just noticeable colour differences as a function of observer adaptation. The colorimeter used was of the Burnham type with 1.6 degree test and matching fields and a 15 degree adaptation field. Nine different types of adaptation were used: dark adaptation, five types of Plankian adaptations of different colour temperature and three coloured adaptations. Very little difference was found between the sets of results for the five white light adaptations, a slight increase in the size of the just noticeable colour difference with decreasing colour temperature being observed. To enable the data to be correctly represented in the u,v chromaticity diagram, which is only defined as uniform for daylight adaptation, the apparatus was modified to enable colour appearance shifts to be measured using a binocular matching technique. An appearance shift matrix was computed from the experimental results that could be applied to the sets of discrimination data obtained with adaptations other than daylight to give the relative appearance of the data in daylight adaptation. This enabled the data to be plotted in the u,v chromaticity diagram and the results considered in terms of absolute uniformity. The results for the white light adaptations showed that the data could be directly represented in this way since the discrimination data were invariant to the appearance transformation for any particular sampling point. This was also true for the results taken using dark adaptation but not true for the results observed using coloured adaptations. The implications of the results with respect to colour differences between points measured under various illuminants and represented in the u,v chromaticity diagram are considered. The possible location of the observed visual effects has been considered with respect to the physiological processes in the eye.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available