City Research Online

Abstract

An experimental study was undertaken whose object was the investigation of colour appearance changes undergone by chromatic stimuli viewed with achromatic surrounds of variable luminance. Another source of appearance changes arose from variations in stimulus subtense. Magnitueds estimation techniques were used to give the hue, saturation (or colourfulness) and brightness of the stimuli.

The most significant variability is evident in the saturation data. For a colour of constant luminance, saturation is maximized near a brightness match between stimulus and surround. Saturation is decreased by increases or decreases in induction level arising from changes in surround luminance.

Changes in stimulus subtense also produced significant changes in estimated saturation. For "related" colours, saturation was maximized in 1° stimulus fields. For "unrelated" colours (without a light surround) this effect was totally absent; here was only a slow increase of saturation with subtense.

It is felt that an explanation of this effect may be found if a 1° chromatic field is regarded as the "fundamental" stimulus. It is shown that this leads to qualitative predictions of saturation changes which can include the maximization of the saturation function under given conditions of viewing. Furthermore, it is shown that the exact properties of the saturation changes are dependent on the general adaptation level; at high adaptation levels, appearance changes are approximately independent of stimulus excitation purity; this is not the case for dark adaptation, when low-purity stimuli are affected more than others.

Finally, appearance data were obtained for very small (0.4 min) stimuli. These were subject to small-field tritanopia, but observers were still able to estimate saturation,

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > Q Science (General) R Medicine > R Medicine (General) R Medicine > RE Ophthalmology
Departments:	School of Health & Medical Sciences > Department of Optometry & Visual Science School of Health & Medical Sciences > School of Health & Medical Sciences Doctoral Theses Doctoral Theses

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