bruno, I now tested this setting with same results:
radiosity photon - 100.000
max photon trace level 50
Advanced effects quality - 100%

What I'm after is a sharp and crisp picture as possible with not too long render time, anything up to 12 hrs is acceptable (on a 3Ghz, 3Gb ram, single core machine) . This is because I have hundreds of images to render and they need to be done before I get too old.

Can the Global illumination , or any of the other settings, give a crisp and sharp picture? What settings should I have to accomplish that?