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Title: Colour naming and luminosity in normal and defective colour vision
Author: Kinnear, Paul R.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1977
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The aims of this research were, as follows: (1) To study the luminosity curves of people with various types of congenital colour vision anomalies and defects, as well as those of normal subjects. By differentiating extreme anomaly from simple anomaly, it was predicted that a gradation should be observable in the pattern of curves from normal trichromatism through the two stages of anomalous colour vision to the dichromatic state for both protan and deutan subjects. (2) With the first aim in mind, to develop a simpler minimum flicker method for determining luminosity curves which would be less demanding on the observer and yet at the same time still generate reliable data. (3) To study the effects of various coloured adaptation fields on the appearance of colours as measured by the colour naming technique developed by Boynton et al., and also on the shape of the luminosity curve. It was predicted that such adaptation procedures should expose weakened or altered colour mechanisms. The apparatus consisted of a 3-channel tachistoscope with modifications. A special unit with a fifteen filter colour wheel and a neutral density wedge controlled by a stepping motor system provided the narrow-band test stimuli for colour naming and the coloured component of the flickering stimuli for the luminosity determinations. The visual angles subtended by the test stimuli and the adaptation fields were 48 and 2 18 respectively. The luminance of the adaptation field varied from 0.2 to 11 fL. The test stimuli luminance was of the order of 1 fL. The simplification of the minimum flicker method was achieved by fixing the rate of flicker at a constant level and setting the density wedge into continual movement. The subject had a push button which reversed the direction of motion of the wedge each time it was pressed. Subjects were asked to scan backwards and forwards across the region of minimum flicker during which time a continuous record of the wedge positions was punched on paper tape for subsequent computer analysis. The colour naming experiments showed that colour naming was considerably affected by a coloured adaptation field whether it extended across the test stimuli area or merely surrounded it. Typically the colour response nearest in colour to the adaptation field was diminished and the response nearest in colour to the complementary colour of the adaptation field extended in terms of the extent of the spectrum for which the various responses were used. Over three hundred luminosity curves were determined under various adaptation conditions using seventy-six subjects who had been classified as normal, simple protanomalous, extreme protanomalous, protanopic, simple deuteranomalous, extreme deuter-anomalous or deuteranopic on the basis of their results with various standard tests of colour vision including the 100-Hue test and the red-green anomaloscope equation. Some preliminary experiments conducted with a neutral adaptation field that extended over the area where the flickering stimuli were presented resulted in a luminosity curve with a maximum at 550 nm. However, most of the curves determined in the presence of a surrounding adaptation field were more mesopic in form with a maximum at 538 nm. No change in the shape of the luminosity curve could be correlated with the colour of the surrounding adaptation field. The luminosity data for the protan subjects demonstrated very clearly the gradation of the loss of luminosity for red from simple protanomaly through extreme protanomaly to protanopia. Statistical differences were also found between the various deutan curves in the lower half of the spectrum. Although the curves were more scotopic in form, the overall pattern of protan, deutan and normal curves was similar to that of Verriest (1970, 1971). The conclusions were that the luminosity channel did appear to reflect the alterations, reductions, and losses in colour mechanisms but that it was not affected by colour adaptation. In contrast, the colour channels as reflected by colour naming were very susceptible to colour adaptation. The high degree of reliability of the data confirmed the success of the modified form of the minimum flicker method used for determining luminosity curves.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available