Sigma AF 17-70mm f/2.8-4.5 DC macro - Review / Test Report
Lens Reviews -
Canon EOS (APS-C)
Thursday, 27 December 2007 08:32
Page 1 of 3
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.