About 2000 Samples per pixel yields this rendering via Lux.
(Modeled in Blender)

I rendered rings a while back in yafray. This time I know
the software a lot better as well as the theory. Or at least,
I'm learning the theory and it's a good sign I'm on my way.

By the way that same image can be rendered like this...

This version lacks the environmental map and the number of samples
per pixel.
Big difference isn't it?