So I ordered the lens on Amazon. This was at a distinct 17mm back focus at 50mm fit the focus, sharp crack. Ie I would. Not even to optimize on the fine adjustment of the focus 7d. The back focus was clearly visible, not only in the test set-up, but also in "normal shots". So I returned it. The return and refund was (as always with Amazon) exemplary.
To avoid that this lens I "accidentally" get back at an Amazon order, I bought the next glass in local retailers. This was (again) at 50mm knackscharf but this time had a clear focus on front 17mm. Therefore, this went back. A new trial, I have not started.
Sure some are now wondering why I did not each the glass from Sigma can adjust later. Firstly, there is no guarantee that the fehlfokus after adjustment also (fully) is resolved, because there are different views about tolerance limits. And even if then at 17mm fits the focus does not have to be true for the area between the. On the other had, even when focusing, the edge sharpness at 17mm significantly worse than my Tamron.
Conclusion: On paper, the lens offers exactly what I'm looking for. Sorry remained, despite very good processing (Picture) quality of the lens behind my expectations. What good is a fast autofocus, when the same has an incorrect focus and if the definition is worse than my current glass at full aperture, which half cost. Perhaps there are also good examples of this lens, I could personally experience (unfortunately) do not. For the price I would expect a lower quality but volatility (standard scattering). For the good workmanship, the extensive range of accessories incl. Geli and camera bag and the potential to be a fine glass with precise adjustment, I forgive (rounded) 3 points.
