I bought a used copy or perhaps I should have bought a new one. This instance had many problems. Center sharpness was only comparable to my 12-40 @ f/2.8 and there wasn't much of a difference between the two lenses at smaller apertures. It was a soft, wide opening. Off-center sharpness was very poor, much worse than my 12-40. It wasn't decentered as the left side looked the same as the right side. I've never held such a bad lens in my hands. I have had very good experiences with the Sigma - 60 f/2.8, 70 f/2.8 (APSc), 70-200 f/2.8 (APSc). I especially like 60 f/2.8. This made me think that this specimen is simply defective. I have decided not to buy another copy as I do not need this focal length.
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