Thanks (again) for the reply :bow:
I'll do some testing for reflection/refraction amount now. This scene contains enough reflections and refractions for a super computer to calculate for a few weeks so I thought It needs to be high. I don't know why I haven't thought about checking what actually helps...

About the max sampling - for a value of 2 I get the result I got in the first post of this page(2). Genny's advise about reflection and refraction rays didn't help much.

just a few more questions:
*Since I've never touched BSP I don't really know how to optimize it. What settings do you recommend I use for a scene like this? 'large scenes' in Maya help isn't really specific...
*What exactly is exr? I found all sort's of mixed up stuff in Google, not much help... was also mentioned a few times in Maya help together with OpenEXR which probably isn't it...
Anyway, What's exr?

Thanks in advance,
Benny