I have one of these and have never been happy with its lack of sharpness, especially at low f/stop numbers.
Someone on another forum passed on a clue that frankly amazed me and might be the answer to my issue. He said that not infrequently, the rear element of this lens is full of tiny air bubbles that would obviously affect sharpness, no matter what they do to "calibrate" it.
Somewhat dubious, this morning I held my lens up to a light looking through the rear element - and there there were! Thousands of tiny bubbles acting like a diffusion filter. Its not subtle at all - the bubbles (or whatever they are) are easily seen.
Of course it will be on its way back to Canon shortly, but I'm still shaking my head over how this defect could have passed even the most rudimentary QC inspection process.
Someone on another forum passed on a clue that frankly amazed me and might be the answer to my issue. He said that not infrequently, the rear element of this lens is full of tiny air bubbles that would obviously affect sharpness, no matter what they do to "calibrate" it.
Somewhat dubious, this morning I held my lens up to a light looking through the rear element - and there there were! Thousands of tiny bubbles acting like a diffusion filter. Its not subtle at all - the bubbles (or whatever they are) are easily seen.
Of course it will be on its way back to Canon shortly, but I'm still shaking my head over how this defect could have passed even the most rudimentary QC inspection process.