In B5 using superfine you can set the "rays per pixel" from 4 up to 256 in the render options. Normal will give you default setting of 1. Not sure if version 4 is the same, as I started with version 5. It depends on the scene and materials used to notice a differance between the two. I remember there was a good explanation given to this quite a while back with some screen shots etc, try doing a search in the Forum, I believe it was Agent Smith who offered up the explanation.