SMC Pentax-DA 17-70mm f/4 ED IF SDM Lens Review

SMC Pentax-DA 17-70mm f/4 ED IF SDM Handling and Features

The SMC Pentax-DA 17-70mm f/4 ED IF SDM lens is for the Pentax range of APS-C format DSLRs. The 35mm format equivalent is 26-107mm, a useful range to cover, taking in a reasonably wide angle through the standard focal length and on to a short telephoto. It is a compact design, weighing just 485g without hood, and making extensive use of high-quality plastics in its construction. The finish is to a high standard.

A lens hood is supplied as standard, but was not included with the test lens provided. The Pentax K-5 was used for the review and the lens balances very well with the camera body. Controls on the lens are minimal as there is no aperture ring, just a zooming ring and a manual focus ring towards the front. The zoom action is firm and smooth. The manual focusing is a very short throw of less than 90 degrees and is typical in its lack of feel for an AF lens. It is not too loose however, and can also be employed at any time when the AF point has been found, or as a full manual focus when the camera body is switched to MF. This QuickShift feature is very useful for final manual tweaks to the focusing point after AF has locked, especially in macro and other close up photography.

Lens construction is 17 elements in 12 groups, including two aspheric elements and ED (extra low dispersion) glass. Minimum focus is 0.28m (0.92 feet) and the lens achieves a maximum magnification of around 1:3, one third life size. That is not as close as a macro lens, but nonetheless a very useful magnification.

Focusing is via the Pentax SDM (Super-Dynamic Motor) motor, integral to the lens. This system is silent and finds focus very reliably, but is not the fastest to lock on. As the mount version on this lens is KAF3 there is no AF coupler to engage the in-body AF system that all Pentax camera bodies have. Later bodies (K10D with firmware 1.3, K20D and later) will support the SDM focusing via the Power Zoom contacts in the mount. If the lens is used on older bodies, it will be manual focus only. As time goes by and older bodies move out of circulation, this will be unlikely to be an issue.

The f/4 maximum aperture is constant, so using flash, for example, will be easier as the aperture does not change when zooming. The lens is SMC coated and adds SP (Super Protect) coating to the front element. This repels water, grease and dirt, making the lens easier to keep clean. The filter size is 67mm.

There are no issues with using the lens, it gives a crisp clear viewfinder image and is easy to focus manually as it matches the focusing screen very well. The zoom is firm enough not to creep when carried, so no lock is needed. The focal length range is excellent for general purpose shooting. 17mm is wide enough for much wide angle shooting and the 70mm end caters well for portraits and some closer sports photography.  

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