Ambient colours are used to effect a very big difference in how your final render will appear. Usually the ambient colour is black, and even a very slight adjustment from this default black setting can radically alter the rendering of a texture. I'm a novice myself in the Artistic league, but If you've got any of the superb classic Japanese creations (Linlin, Tagosaku for example) you'll see just what a difference this subtle variation of Ambient colour can achieve. The data for such subtle variations is very often a major part of MAT files. With Poser 4 it was a simple matter to click on a MAT file and apply the changes. The colour alone achieved the desired effect. However, Poser 5 offers much greater possibilities, and. by default (set to 0) any variations in Ambient colour which a MAT file may have introduced are effectively rendered as redundant. If all Ambient Values were set to 1 then this wouldn't be the case.