Can anyone out there tell me how the resolution and contrast compares between the 80 and the 60. I do lots of reproduction work of art with my 80 on my cm and am pleased with results but sometimes it seems to be a bit soft...(yes I uncock the mirror before the shot) I have heard both that it is a sharper lens and a softer lens... . what do you all think? (ps never used a 60, ever.) thanks!