Lens review

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM

10 June 2009
Arkadiusz Olech

3. Build quality

Pentax 17-70 mm has typical dimensions for similar lenses. The picture below shows it clearly, with the tested lens lying next to Sigma 17-70 mm, you can also consult the chart with its immediate competitors’ data. Although Pentax is the heaviest and the biggest of all the differences are small and you must take into account the fact that Pentax is sealed and has an ultrasonic autofocus motor which some of its competitors lack.

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM - Build quality

The quality is difficult to flaw. The lens starts with a metal bayonet which is followed by a quite solid, black metal barrel; most part of it is occupied by a big, rubber-coated zoom ring. It moves smoothly and with due resistance. We can’t say that much about the manual focus ring, though. It is small, too narrow to suit me and, what’s the worst, it moves too easy. In fact it’s enough to wave the lens horizontally for the ring to change its position. Obviously, even by accidentally touching the ring very lightly you might jump the whole scale. It is decidedly an oversight.

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Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM - Build quality

The lens finishes with a non-rotating filter thread 67 mm in diameter. The fitting doesn’t rotate either by focusing or by focal length setting, when the front element extends on a telescopic tubus and the physical length of the lens is almost doubled.

Pentax is the most optically complicated instrument from all described here. It contains as much as 17 lenses in 12 groups. The similar number of elements have only stabilized lenses 17-85 mm Canon and 16-85 mm Nikon. Two lenses are aspherical. Pentax was equipped with a round seven blades aperture, which can be stopped down to f/22.

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM - Build quality

The buyer gets front and rear caps and a petal-type lens hood in the set.

Pentax smc DA 17-70 mm f/4.0 AL [IF] SDM - Build quality