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Webvision: Color Perception Page 7 of 18 ' <br />Haar) Comgl=multzr)r and dominantActrai cy_velcngtha of colour "t. Colour B is also gQ ementar to colour :i, Einac_uz aft ro_ E.m e of the ting <br />tazreleti�thn wiltprnduce �xhile.(2? I',jpe�i � <br />The achromatic point varies depending upon the standard illuminant that is used (figure 12). A shift in <br />the x and co-ordinates occurs as colour temperature increases. For standard illuminant C, there is no <br />complimentary wavelengths for green (between wavelengths 492 nm to 567 nm) However, white light <br />can be formed with a suitably chosen purple light (figure 12). <br />Figura 12. Variation nns;fian oft e achromatic point accordin to colour tcmp_raturc. (From PcnLnti _W. J. )�Bori };'s Ciirdcz Refraction Pbiladgjl ia: W. P_ <br />Saunders Cosa _ an . 19991.{9 ri apcg�magej <br />Colour Discrimination Functions. <br />The three variables in colour vision, hue, saturation and brightness, all depend on <br />wavelength. Colour discrimination experiments allow us to know how much change in <br />wavelength is required to detect a difference in hue, saturation and brightness. <br />Hue discrimination describe the amount of change in wavelength (1 + A 1) that is required to be able <br />detect a change in hue. For blue and red light; a large change in wavelength is required to detect a <br />change in hue while less than 2 nm change in wavelength is needed'for most of the spectrum for a <br />person with normal colour vision (figure 13). <br />Qu coni` tial' NA.0 bog t <br />'kJ�i .ss �t�tsz <br />http://www.webvision.med.utah.edu/KallColor.html 6/18/01 <br />