sampling contrast in XSI

[cryptosporidium]

hi there, i got a problem setting up a good antialiasing in XSI´s mR. I can set the min and max subdiv values, this works normally, but sampling contrast just doesnt seem to work as i would expect. it behaves very unexpectably - mostly changing the values has no effect, or, the change is quite a bit too drastic and corresponds to either all min samples value or all max samples value. I know its probably issue on my side, but according to manual and various articles simply setting darker values should tend to perform more sampling even for less contrast areas and vice versa. But this is not happening. Any hints?

[Intuition]

Usually I find that when your ready for a final render that a setting of min 1 and max 3 is good with a sampling value of around 0.05 'ish with the triangle filter set to size 3. Each filter has its own strengths but mitchell and triangle are my favorites and generally give a nice sharp image without too much charpening to the point it looks jagged again.

Can you post an image so I can see what it happening, in case these settings aren't helping?