p126fig04.03 A McCann Mondrian is an excellent display with which to illustrate how our brains discount the illuminant to compute the "real" colors of objects.  See the text for details.<BR>|| Color constancy: compute ratios. McCann Mondrian. Biological advantage: never see in bright light, eg tropical fish<TABLE border="1"><TR><TD><B>Discount the illuminant</td><TD><B>Compute lightness</td></tr><TR><TD><I>Different</i> colors seen from the <I>same</i> spectrum<BR>... similar to those seen in white light</td><TD>Physical basis: reflectance RATIOS!</td></tr></table>