FREE VRAY HDRI LIGHTING TUTORIAL
Using HDRI for lighting will result many times in a lot of splotches and blurry shadows. Especially with high resolution HDRI maps containing a lot of contrast and/or small light sources, this can become a big issue.
This free Vray tutorial covers a quick and easy fix for the problem, without increasing rendertime too much, and without resizing or blurring the HDRI map. For more on this free 3d Vray tutorial go here