Quote - > Quote - Shadow Min Bias = 1.0

This is OK for the test scene with a sphere and a couple of planes, but when you introduce very small geometry, you'll find that a high shadow min bias means that the small geometry will not cast shadows - which is probably why the smoothed polygons in the curved part of the backdrop aren't showing artifacts, they aren't casting a shadow.

Yes, I know the problem. I discovered (actually was told, I think) that Shadow Min Bias worked with raytraced shadows while I was getting a good result with a displacement mapped version of body hair. That needed a very small value of the bias to eliminate tiny polygonal self-shadowing. My point mostly was that Shadow Min Bias does effectively what BB was suggesting and confirms his analysis of the problem. Any individual render will vary.

Whichway