Defining min and max radius
 

How can I define the best minimal and maximal radius for final gathering at the render settings?

Take the first number you think of .. that's your max. Divide it by 10, that's your min. j/k :D

I've heard that your max radius should be around 1/12 the size of your scene... but dont take that as a gospel truth. Rather you can caluclate that and then tweak from there.

If anyone knows a better answer I'd be very interested.

well if you leave the settings at zero mental Ray will automaticaly try to set the values for you. But, if you wish to change for better accuracy just take 10% of the over all scene unit size and enter that into the max radius. For minimum enter 10% of the Max Radius. This is just a general rule.

e.g. if your scene size is 100 units wide enter 10 for max radius. For min enter 1 which is 10 % of 10.

use the measure tool to find out the largest distance that your scene occupies. Then divide that by 10 and that will give you the max radius, then divide by 10 again for the min. That really is a rough guide though.

Alan