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Review by Klaus Schroiff and Markus Stamm, published March 2012
The "old" Sigma AF 17-70mm f/2.8-4.5 DC is/was one of the more popular standard zoom lenses. It provides a longer reach than the average "kit" zoom lenses (usually 18-55mm f/3.5-5.6 variants) yet it's a bit more affordable than the typical mid-grade zoom lenses a la Canon EF-S 17-85mm f/4-5.6 USM IS or Nikkor AF-S 16-85mm f/3.5-5.6 VR ... and it's 2/3 f-stops "faster".
In our previous tests it performed pretty well. But the initially released version relied on a fairly dated screw drive, which made it an unattractive choice for most Nikon DX users. Sigma upgraded the F-mount version of the lens to an HSM drive (the Canon variant uses a DC motor instead), but still the lens lacked one important feature: optical image stabilization. Well, it seems as if Sigma agreed here because they eventually released the Sigma AF 17-70mm f/2.8-4 DC HSM OS, that provides both the modern ultrasonic AF drive (HSM)as well as stabilization (OS).
In this review we will have a look at how the lens performs on our current DX test camera, the Nikon D7000.
The build quality of the Sigma lens is pretty good - it's made of tightly assembled combination of metal and high quality parts. Like its predecessor it uses a duo-cam system to extend the lens when zooming towards the tele setting. You may notice that it's actually quite long at 70mm especially when mounting the supplied lens hood. There's only a very marginal wobbling in the zoom mechanism even in the most extreme setting.
The two control rings have a smooth, pleasant action. The front element does not rotate, so using a polarizer remains easily possible. The focus ring is coupled to the AF mechanism so it rotates during focus operations. This is a point where the cost-cutting measurements get a little more obvious.
Both the zoom and the focus ring work in "Canon" style, which is the exact opposite of how these rings work on Nikkor lenses. If you're used to the Nikon way of zooming, the Sigma lens may be a challenge for your muscle memory.
The 17-70mm OS features the slightly simplified version of Sigma's HSM ("hypersonic AF motor"). It is still fast and nearly silent but full-time manual (FTM) override is not possible in one-shot AF mode. Unlike the predecessor, which relied on the camera's screw drive and had no internal motor at all, the OS lens provides full AF functionality on all current Nikon DX DSLRs, including the entry-level models.
It is worth to mention that the lens carries a "macro" in its name. You shouldn't expect the performance levels of a true macro lens here but the Sigma can focus down to 0.22m which translates to a max. object magnification of 1:2.7 at 70mm. This is good enough for some basic close-focus applications.
A major new feature is, of course, Sigma's OS ("Optical Stabilizer"). As already reported in previous reviews it is impressively efficient and as good as the corresponding genuine manufacturer implementations. Sigma claims a gain of 4-stops which doesn't seem to be unrealistic. Actual results will vary depending on the photographer, of course.
The Sigma is a G-type lens and does not have a dedicated aperture ring.
|Equiv. focal length||25.5-105 mm (full format equivalent)|
|Equiv. aperture||f/4.2-f/6 (full format equivalent, in terms of depth-of-field)|
|Optical construction||17 elements in 13 groups inc. 3 aspherical and 1 ELD elements|
|Number of aperture blades||7 (rounded)|
|min. focus distance||0.22 m (max. magnification ratio 1:2.7)|
|Dimensions||79 x 89 mm|
|Filter size||72 mm (non-rotating)|
|Hood||petal-shaped, bayonet mount (supplied)|
|Other features||Optical stabilization (OS), Hypersonic AF drive (HSM)|