My render times was 13:08 for gamma and 13:30 without - that is, shorter WITH gamma. It seems reasonable to conclude that gamma correction is no-no for PC users (hey...another special effect). But we have only heard ONE Mac user, maybe Alleycat has the ONLY Bryce gamma compatible computer in existence;) BTW, the manual has a few words about gamma on page 307. starts to bleach his clothes to give them a colour more true to nature???;)