If a person consciously takes a lens with max. aperture 1.4 - so, probably, he will shoot at 1.4! Therefore, during the checks, there was no question of tightening the diaphragm. So, on the well-deserved and proven D700 with a wonderful and tenacious autofocus, this Sigma even hit the right spot on the central point somewhere out of 3-4. Moreover, there was no stable front or back focus, each time either undershoot or overshoot. Both on the target and on people. Tried 2 lenses from 2 different stores. Same. Not a single Nikkor I had such jambs in autofocus, even a cheap screwdriver fifty dollars. Sigma's statements that quality control has grown a lot in the new series of lenses - I will leave without comment. I think that good reviews on this lens are written by: a) people who are really lucky with it, and I'm really happy for them! b) people who have familiar sellers and the opportunity to choose the least copy out of a dozen. I talked with the seller in one store - he confirmed that with this lens there are usually no complaints on Canon, but on Nikon - through one problem.
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