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Webvision: Color Perception Page 2 of 18 <br />Colour Matches <br />f <br />The trichromatic nature of colour vision will enable almost any colour to be matched by a" <br />t <br />mixture of three colours. This trichromacy of vision is also linear. This means that <br />colorimetric equations has properties of an ordinary equation. <br />The colour matches of quantity CS of a stimulus S can be expressed as: <br />Cs(S) = C1(11) + C2(12) + C(13) <br />where Ii are the three primary colours (not necessarily monochromatic spectral colours) and Ci are <br />tristimulus values. <br />Tristimulus values represent the quantities of each of the three primaries necessary to achieve a match <br />for colour and luminosity (figure 2). They can be expressed in units of luminous flux or radiant flux, or <br />even an arbitrary scale provided that the arbitrary scale conveys the relative proportions of the three <br />quantities. <br />Fi mire 2. �utsiecKs arc _aslccd to aciiusf ths_ee enlo�xi:s on the leis hand sicde of the�zrtite field to match a standard coJ.our presented on, t e sight hand side of the <br />bipar{i#e freld_ oi�%)P_� tmgg_2 <br />Additive and Subtractive Colour Mixtures <br />Two or more colours can be added together to produce a new colour composed of the <br />mixture of the initial colours used. This can be demonstrated on a white screen with three <br />colours: blue, green and red. Cyan, magenta, yellow and white are formed from the mixture of these <br />colours (figure 3). One of the requirements in choosing colours to be used in colour mixing experiments <br />is that two of them cannot be mixed to produce the third. <br />http://www.webvision.med.utah.edu/KallColor.html <br />6/18/01 <br />