holy f** moly!

I think I figured it out finally.

the glossy reflection grain was a result of 2 (1/2) factors.


the first and minor thing was, I had areaLight samples set to max 20 which was too low and I needed around 50 samples. this made the material look about 20% cleaner.

secondly and that´s the big surprise for me, I was trying to fake a fresnel effect in the BRDF settings:

0 degree - 0.9
90 degree - 1.0
BRDFcurve - 30

where the material looked and behaved the same way (grain) when I was just checking on the fresnel effect. now, after lowering the BRDF curve back to 5 the grain is almost gone! glossy samples back to 64.

the only remaining thing is - it would be great to have an per object or per material override for the Anti Aliasing Contrast and the metal would look perfectly fine without effecting the whole sceene and increasing rendertime too much.

all best!