The Quantification of Small Visual Colour Differences

The Shademaster system, developed by UMIST, was used to explore the use of on-screen colours in order to assess the reliability of the CMC(l:c) formula as a measurement of small colour differences. Differences limited to almost pure hue, chroma and lightness changes around nine colour centres were judged by a group of ten observers. Each colour difference pair was presented on-screen in the form of a divided tile. The colour difference between each pair was measured using a Bentham telespectroradiometer and by a method using revers transformation of RGB to CIE coordinates. The data obtained from the judgements were used to construct perceptibility boundaries around each colour centre