actually, I was wrong about why the Mental Ray makes blotches :blush:

Its actually the particular method of Final Gathering used- tracing a single photon from the light to the point, doing that for all points, storing a photon map, and then averaging all of the results in a particular area (thus the FG radius). The higher radius and the less photons, the worse the img will be. Esentially the FG rays dont have to exceed 200-300 because they are each used as an addition to the photon map and they mean the amount of rays that are cast from each point used to correct the initial photon map.