Skip to Content

Department of Cognitive Science

Cogntive Science Alumni

Ralph Pridmore

Ralph Pridmore

Thesis Details

Roles of complementary colours in colour perception.

The thesis (available at Macquarie University library) is publications-based, comprising five publications in peer-reviewed journals. The general language and context of the thesis is psychophysical, i.e. colour is psychological (and difficult to measure quantitatively), and the colour stimulus is physical (thus accurately measurable). Complementary colours are defined as a pair of colour stimuli which, with appropriate complementary wavelengths and ratios of radiant powers, admix a selected white (e.g. that of the ambient illuminant). The Introduction describes the research of complementary colours since Isaac Newton (1700), in both colour appearance (e.g. simultaneous contrast) and colorimetry (e.g. the organisation of colour mixture diagrams with complementary wavelengths as opposites through the white point), and outlines the questionable views of the conventional multistage theory of colour vision: that is, that all things trichromatic or trimodal, including colorimetry [such as Red Green Blue (RGB) colour matching/mixture functions and complementary colour functions], are located with the trichromatic cones (e.g. three types of cone receptor) in the receptor layer of the retina, and thus play no part in colour appearance. The thesis main body gives evidence contradicting this conventional view, by describing recent research demonstrating ten roles of complementary colours in the colour vision process, including colour appearance; all roles have spectral-sharpened function curves (e.g. a Red peak about 600 nm), indicating a post-receptoral location. Added to the already known colorimetric role of complementary colours in colour matching/mixture (e.g. CIE chromaticity diagrams), this gives a total 11 roles. At least eight of these (i.e. wavelength/hue discrimination, spectral sensitivity, saturation, lightness, uniform hue difference, chromatic induction, colour constancy, and attribute contrast) concern colour appearance. In trying to deduce an overall role for these 11 roles of complementary colours, it is noted that all roles have function curves with complementary peaks and troughs (that is, RGB peaks and CMY troughs), which automatically/sensorily adjust to illuminant, thus ensuring colour constancy. In conclusion, complementary colours have at least 11 roles in colour vision, with an overall role of colour constancy. [Note: My subsequent paper, "Complementary colors theory of color vision: Physiology, color mixture, color constancy and color perception. Color Research & Application, 2011, vol 36, pp 394-412", expands the above to 40 minor functional roles within three general roles in colour vision, i.e. colour-mixture or -production, colour constancy, and colour perception.]

Further Information


Who is Visiting

Contact Details

Telephone: (02) 9850 9599
Fax : (02) 9850 6059
Email :
Web :