Pentax SMC DA* 16-50mm f/2.8 ED [IF] SDM - Review / Test Report
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Review by Klaus Schroiff, published November 2008

Lens kindly provided by Oliver Kirchner!


The Pentax SMC-DA* 16-50mm f/2.8 ED [IF] SDM is part of the professional grade DA* lens lineup by Pentax. At around 600-700 &eur;/US$ it is surprisingly affordable when considering its direct counterparts like the Canon EF-S 17-55mm f/2.8 USM IS or the Nikkor AF-S 17-55mm f/2.8 ED. Typical for Pentax DA lenses it has been designed for APS-C DSLRs only where its field-of-view is equivalent to about 24-75mm on full-format DSLRs.

The build quality of the Pentax lens is very high thanks to quality materials and weather-sealing. The broad, rubberized zoom and focus control rings operate very smooth. Thanks to an internal focusing system (IF) the front element does not rotate so using a polarizer is no problem. The lens uses a duo-cam system (2 inner lens tubes) to extend when zooming towards longer focal lengths. This may sound a bit worrisome but the tested sample showed no significant wobbling whatsoever here. The Pentax Super Protect (SP) coating on the front element has been optimized to repel dust, water and grease.

The DA* 16-50mm f/2.8 features the new Supersonic Dynamic Motor (SDM) AF (*) although it also offers the old AF drive screw for legacy DSLR support. In terms of technology the Pentax SDM is pretty much comparable to Canon's USM or Nikon's SWM. Ultrasonic AF motors operate near silent and usually faster than conventional AF motors but don't expect from the Pentax implementation - it may be a bit faster but it's not a speed daemon. Thanks to a Quick-Shift system manual focus override is instantly possible in Single-Shot AF mode. The AF accuracy of the tested sample was mediocre with a quite significant back-focus problem at 50mm (which has no impact on the test figures below). FWIW this is the 3rd sample tested by Photozone - the previous 2 samples had centering problems. The quality control of the DA* 16-50mm is a rather frequently discussed topic within the Pentax community. However, it seems as if the optical alignment problems have been resolved by now.

Equiv. focal length24-75 mm (full format equivalent)
Equiv. aperturef/4.2 (full format equivalent, in terms of depth-of-field)
Optical construction15 elements in 12 groups inc. 2? aspherical elements and 1 SD element
Number of aperture blades9
min. focus distance0.30 m (max. magnification ratio ~1:4.88)
Dimensions84 x 99 mm
Weight565 g
Filter size77 mm (non-rotating)
Hoodsupplied, petal-shaped
Other featuresSDM