Pentax has announced a new high-grade consumer zoom lens today, the Pentax DA 17-70mm f/4 [IF] SDM. Providing a new lens in the same class as Pentax's popular constant-aperture 16-45mm f/4, the 17-70mm adds a 4x zoom range as well as Pentax's quick and quiet Supersonic Motor Drive (SDM) lens-based focusing motor.
Other features and specs include Pentax's trademark Quick-Shift Focus System for on-the-fly transitioning between manual and auto focus, Super Protect coating to protect the exposed lens elements from dust and scratches, and an inner-focus optical design that "eliminates lens extension and retraction during focusing operation."
As noted, the new lens provides a maximum aperture of f/4 across its 26-107mm equivalent range. Minimum focusing distance throughout the zoom range is 11 inches.
One noteworthy change compared to Pentax's pro-grade DA* lenses with SDM is the use of the KAF3 (rather than previous SDM lenses' KAF2) lens mount on the 17-70mm. The KAF3 mount is almost functionally identical to the KAF2, with two contacts driving the internal focusing motor, but the new mount eliminates the secondary focus drive option via the body's focusing motor found on KAF2 lenses. Hence, rather than reverting to body-driven auto focus on older Pentax bodies (anything further back than the K10D or K100D Super), the new DA 17-70mm is manual focus only in these applications.
While users with older Pentax digital bodies may be disappointed at the loss of AF compatibility with the latest lens, the move to KAF3 spells good news for current Pentax shooters: outside of its dimunitive DA Limited glass (which will retain body-driven AF), look for new lenses from the manufacturer to feature SDM focus drive exclusively going forward.
At present, the DA 17-70mm f/4 lens is slated for U.S. retail release next month, with a suggested price of $599.95.