Sigma AF 17-70mm f/2.8-4.5 DC macro - Review / Test Report
Lens Reviews - Canon EOS (APS-C)

Introduction

The new Sigma AF 17-70mm f/2.8-4.5 DC macro is a highly anticipated lens especially among Canon users seeking for a higher quality, affordable alternative to the original Canon EF-S 18-55mm f/3.5-5.6 or EF-S 17-85mm f/4-5.6 USM IS. In fact the interest in the Photozone forum was big enough to purchase the lens for testing rather than loaning it from users like you which is the usual approach for the local lens tests. The Sigma is a DC ("Digital Camera") lens specifically designed for the reduced image circle of today's APS-C DSLRs where its field-of-view is equivalent to 27-112mm on classic full frame SLRs. The lens is available in Canon EOS, Nikon and native Sigma mount.

The optical construction is made of 15 elements in 12 groups with 2 aspherical and one SLD (Special Low Dispersion) element. The aperture mechanism features 7 aperture blades. The min. focus distance of 0.20m resulting in a max. magnification of 1:2.3. The Sigma has no floating elements for close focus correction so don't expect wonders at extreme close focus settings. The lens extends significantly during zooming (see below) reaching its max. length at 70mm. Despite the quite large max. aperture the lens is still pretty compact and light-weight at only 79x83mm and 455g respectively. It's interesting that the AF 17-70mm DC is marginally bigger than the Sigma AF 18-50mm f/2.8 EX both regarding physical size as well as filter diameter (72mm vs 67mm) . A petal-shaped hood is part of the package.

Unlike its cousin the AF 17-70mm DC is not a designated EX lens (Sigma's pro grade lineup) but the build quality is still pretty good (tight controls, no wobbling) and only marginally worse than the AF 18-50mm EX. The lens has a slight crinkle finish (with a tendency to collect dust) and broad rubberized control rings. The focusing action feels smooth but a little lifeless (not damped) whereas the zoom mechanism has a slightly varying friction across the range. The lens doesn't show any tendency for zoom creeping but Sigma has provided a transport lock (17mm only). The front element does not rotate so using a polarizer remains easily possible. Unfortunately Sigma has still not managed to implement a focus ring that does not rotate in AF mode. The 17-70mm DC features a conventional AF micro motor so the AF operation is a little on the noisy side but thanks to an extremely short focus path (~45 degrees) the AF speed is very fast. The accuracy seems on par with the Canon kit zoom.




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