Help - how to sharpen my images

So, coming in from using Poser, I'm having great fun playing with DS 4.8 and Iray.

But.

My images are lacking sharpness, and, frankly, I can't fathom the Iray settings.

So.

I've increased Max Samples to 11,000; I've set Max Time to 22,000; Convered ratio to 98.7%, but it's still not sharp.

So:

Does Min Samples help? Set to what?

What about the filtering options?

How about tone mapping? I run ISO at 175; is that good?

Any clues and suggestions will be much appreciated.