I have a 70-300 DO that I bought 2 years ago used with a known focus seeking problem. I sent it in to Canon in NJ and they fixed the seeking problem. I thoght is was pretty good. Only after looking at some pictures taken at distance did i discover that the lens was terrible at 300mm and distant objects (maybe a 15 pixel blur?). (sorry no examples) I did the testing at 1/1000s.
at 70 AOK close and far at 1:1 good
at 300 close focus is good, distant focus is terrible.
I've tried manual focusing on either side of the auto focus infinity point but no improvement.
Is there a name for this defect? Is it fixable?
Anybody with similar experience?