Quote - Same here, BB. Do any of us actually know what the number in the Irradience Caching slot actually means? I could maybe argue that the higher the number the more that is cached, meaning that fewer accurate values are actually used. If so, higher cahce means faster, not better. Hyothesis available for testing...

To quote the Poser 8 manual:
"Irradiance Caching : Determines the ratio of shading points where indirect light will be calculated by raytracing vs. those that will be interpolated.  Low values result in shorter render times, with more interpolation. 

High values achieve more precise results at the expense of increased render times."