p128fig04.04 When a gradient of light illuminates a McCann Mondrian, there is a jump in the total light that is reflected at nearby positions where the reflectances of the patches change,<BR>|| Compute reflectance changes at contours. Fill-in illuminant-discounted surface colors.<TABLE border="1"><TR><TD><B>left</td><TD><B>right</td></tr><TR><TD>I + ε</td><TD>I - ε</td></tr><TR><TD>A*(I + ε)</td><TD>B*(I - ε)</td></tr></table>A*(I + ε)/(B*(I - ε)) - 1 = A/B - 1