Unfortunately, two cucumbers caught at Amazon ...

No matter if you caught a good specimen (the available tests with high resolution sample images show it) get with the Sigma 18-35 a lens that loose six star has earned (sharp at maximum aperture at 18-35 mm, hellishly sharp at f = 2.8-5.6, has no equal). I have ordered the lens with high expectations. First of all: I tested the lens at rest on a stable tripod and images (were between the mirror moves and pressing the shutter button ~ 3 seconds waiting) shot both via the viewfinder as well as via LiveView each with mirror lockup and remote release when the camera was a Nikon D7100 uses. The first lens has the phase autofocus in good light at> 50% of all images completely wrong location (AF-C, single central focus area, relatively easy to be detected motifs without depth), images that have been made with the contrast AF (Live View) were all ok. Since I shoot images mainly with the viewfinder, the lens went back (yes, I know, you can Sigma lenses with the USB dock itself calibrated, but that should at most serve in my opinion for fine adjustment and not Sigma to induce in the AF to sluts adjustment, Nikon and other Fremhersteller get it indeed toward). The second lens (I have to praise Amazon here, the new was two days after the replacement application already there), the autofocus was now perfectly. Disillusionment turned quickly when I looked at my optical capabilities closer: this specific copy was in the range 35-24 mm with F = 1.8-3.2 strong chromatic aberrations (such an extent that I at the RAW files with DxO Optics Pro 9 could with the correction option "chromatic aberration" with values ​​at the stop not to an acceptable level reduced) and a pronounced directional (alignment of lens) and can not be eliminated by manual focus blur (I have it all Given Sunday long tried) to edges ( I suspect that both effects are caused by decentering / misalignment of a lens group had). Do not misunderstand, I do not expect extreme sharpness at maximum aperture, but with this lens, at least a good to very good, and above all an even picture focus. Raison d'être of this lens is that you can thus work with open aperture or slightly dimmed, so with a heavy heart No. 2 returned. I will not order again this objective at Amazon, at least for Nikon appear here "challenge cups" on the road to be (unfortunately the Sigma packaging not sealed, so you can not see whether the resulting lens is returned goods or factory).

Addendum of 5:04:15: I have now acquired the lens in the camera store and keep. This now third copy is visually perfect, but this time there were again problems with the AF (AF-phase), namely strong front focus on all distances at the long end, short end was fine, though not perfect. Then I have the lens with the camera (Nikon D7100) for Sigma for adjusting sent (free of charge, as within the warranty). The lens came in the same week back with the note that it was adjusted. The AF behaved indeed different, but of adjustment could not really be any question: This time backfocus at the short end over all distances, long end now ok. Now I was finally fed up and have ordered the USB dock of Sigma and the thing for a whole afternoon myself adjusted. Now finally it fits: Lens AF top and is located now precisely. Too bad that Sigma that hinbekommt not alone if there is a will, there seems to be feasible Yes. If now someone objecting that it could indeed be my D7100: The I before sending to Sigma Nikon check left, everything was ok.