Pentax SMC DA 17-70mm f/4 AL [IF] SDM lens for DSLR, K-5,

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Pentax SMC DA 17-70mm f/4 AL [IF] SDM lens for DSLR, K-5,

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 Pentax SMC DA 17-70mm f/4 AL [IF] SDM lens for DSLR, K-5,
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Date Added: 07/01/2017
Last Updated: 07/01/2017

Price : 239

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Pentax SMC DA 17-70mm f/4 AL [IF] SDM lens for DSLR, K-5, - Dunoon, , United Kingdom

Boxed Pentax SMC DA 17-70mm f/4 AL [IF] SDM lens for Pentax K-mount DSLRs. Includes lens hood, caps and info. sheets.

Widely regarded as best of Pentax's prosumer zoom lens line up, with v. good reviews. I found it sharp, contrasty, relatively bright, nice to use, and the motor is nearly silent. V. nice lens - better optically IMO than e.g. Canon equivalents. Bought in 2012 but rarely used due to lack of time. All's working as it should. Has been stored sealed with silica gel.

Also selling my Pentax SMC-DA 16-45mm f/4 ED AL and Pentax smc DA 55-300mm f/4.0-5.8 ED - see my other listings. Will bundle 2 or all 3 lenses if anyone's interested.

Happy to post at cost. Any questions, please ask.

Here's the Phtozone review:

"Introduction
As of the time of this review Pentax is offering no less than 5 lenses covering the standard zoom range and the Pentax SMC DA 17-70mm f/4 AL [IF] SDM is the latest addition to this series. It can be seen as the sweet spot lens here because it offers the most attractive combination of range, speed, technology and price - on paper at least. It is a dedicated APS-C format lens with a field-of-view equivalent to 26-107mm (full format).

The build quality of the Pentax lens is very high thanks to quality materials and tight build tolerances - this positive impression is actually typical for the majority of the Pentax DA lenses. 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 at first but the tested sample showed no significant wobbling whatsoever here. Both the broad, rubberized zoom control ring as well as the smaller focus control rings operate very smooth. The lens has an internal focusing system (IF) resulting in a non-rotating front element. The Pentax Super Protect (SP) coating on the front element has been optimized to repel dust, water and grease.

The DA 17-70mm f/4 features the new near-silent Supersonic (ultrasonic) Dynamic Motor (SDM) AF. Unlike the DA* 16-50mm f/2.8 SDM it does not offer the old AF drive screw for legacy DSLR support but that's forgivable by now. Thanks to a very short focus path (make it 3-4cm for the whole range) the AF speed is very high. However, on the downside this approach has also the consequence that manual focusing is extremely difficult - a minor adjustment on the focus ring has a major impact on the focus. The AF accuracy was fine in field condition though. Thanks to a Quick-Shift system manual focus override is instantly possible in Single-Shot AF mode.

Specifications
Equiv. focal length 25.5-105 mm (full format equivalent)
Equiv. aperture f/6 (full format equivalent, in terms of depth-of-field)
Optical construction 17 elements in 12 groups inc. 2 aspherical elements
Number of aperture blades 7
min. focus distance 0.28 m (max. magnification ratio ~1:3.2)
Dimensions 75 x 94 mm
Weight 485 g
Filter size 67 mm (non-rotating)
Hood supplied, petal-shaped
Other features SDM

Distortion
The DA 17-70mm f/4 is a fairly typical representative of its class. It shows relatively heavy barrel distortion (~3.1%) at the wide end of the range (17mm). The 24mm setting provides distortion-free images whereas you can observe slight to medium pincushion distortions at 40mm and 70mm.

Move the mouse cursor over the focal length text marks below to observe the respective distortion
17mm 24mm 40mm 70mm

The chart above has a real-world size of about 120x80cm.

Vignetting
The Pentax lens is a dedicated APS-C lens and like most of its kind it shows a fairly pronounced degree of vignetting at large aperture settings. Unsurprisingly the weakest spot is at 17mm @ f/4 (~1.1EV). Stopping down to about f/5.6 resolves the most of the critical vignetting.

MTF (resolution)
The Pentax lens was capable of delivering very impressive resolution figures in the MTF lab. At 17mm and 24mm the center performance is superb and the border quality is easily on a very good level. At f/4 the extreme borders are a little softer at 17mm but stopping down resolves the problem. At 40mm we've an evenly high center to border resolution distribution. There's a little performance drop at the extreme tele end of the zoom range. The center performance is still very good here whereas the border quality suffers a bit although it's still perfectly Ok even at max. aperture. The global sweet spot of the lens is reached around f/8.

The tested sample showed a slight centering defect at 70mm - a perfect sample may even be slightly better at this setting.

Chromatic Aberrations (CAs)
Many of the recent Pentax zoom lenses struggle somewhat regarding the amount of lateral CAs (color shadows at harsh contrast transitions) at the image borders. The DA 17-70mm f/4 is far from being perfect here as well but it manages to do a better job. As expected the 17mm setting produces the most pronounced CAs peaking beyond 2px at f/4. However, stopping down reduces the problem to acceptable levels here. You may also spot some CAs at 24mm but it's not really objectionable anymore and beyond it's a non-issue in most situations.

Verdict

The Pentax DA SMC 17-70mm f/4 AL [IF] SDM is undoubtedly the most desirable standard zoom lens in the current Pentax lens lineup. The resolution characteristic is very good without any significant weakness. The vignetting and distortion are about average for a lens in this class. The lateral CAs are relatively well-controlled although you may spot some traces in field conditions when using wide-angle settings. The quality of the bokeh (out-of-focus blur) seems to be very fine albeit limited compared to fast prime lenses naturally. Contra-light situations are handled fairly well with comparatively underdeveloped ghosting problems. Typical for most Pentax DA lenses the build quality is on a very high level. The fast and near-silent ultrasonic AF is also a very welcome new feature. All-in-all a very harmonious package."


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