I've never had a problem with sharpness on my 90mm C. I've blown negatives up to 20x24 without any loss in quality and that's from me using it handheld. Though, this was in the middle of the day, with full sun, but I stopped the lens down to f/11 to give me more depth of field and bring out detail in my subject. I've found that shooting wide open is kinda sketch because you need to be dead on with your focus.