Summary: First off, I rarely give a product one star, but I believe this warrants a heads-up for anyone thinking of buying this lens. I bought mine in 2010, as a replacement for the kit 18-55. I was impressed with the build quality and the images it produced.
Summary: I purchased this lens about four years ago. I am not a professional photographer and take very good care of my lenses. After about three and a half years the focus motor went bad. I sent it to C.H.R.I.S. camera repair and got a new focus motor put in the lens.
Pentax 17-70mm f/4 AL IF SDM SMC DA review by cali4nia
7 January 2014
Summary: This lens produces very pleasing colors and delivers good contrast. The AF was working flawlessly, quick and precise, no hunting even in dimply lit conditions. Lens is well built, but somewhat heavy. The Achilles heel of this lens is the resolution.
Summary: Depending on your criteria you will either love or hate this lens. First the negatives. This lens is soft at f/4 and improves little when closed. How soft is soft? Noticeably softer than the kit DAL 18-55 wide open even when resized to ~2MP (24" monitor).
Summary: I use this lens more than any other. It is a wonderful lens that I would call all purpose. I mainly use it for portraits. It is so much nicer than the standard kit lens. This is bigger, heavier, and the circumference is a lot wider than the kit--you can tell that it is a pro lens.
Summary: This lens is super sharp, has a very useful focal length, focuses fast and quietly, and looks great on the camera. I used it in a night club environment on my k-r and focusing was no issue in the dark even with ISO200. Pictures have a very nice 3D effect just like my DA* 50-135 produces.
SDM type Auto Focus motor quit working and known to be a problem
B. Breshears, Amazon
19 November 2012
Summary: I'm usually reluctant to give low ratings and write negative reviews. Unfortunately and to Pentax's shame, I have to warn users about this Pentax lens with the built-in SDM drive motor for the auto focus.
Summary: If you had to buy only one lens to use with your Pentax camera, this one would be hard to argue with. It really hits in a lot of areas - that 1 extra mm on the wide end is nice, the macro is really decent, the sharpness is adequate in some cases and excellent in others throughout the zoom range.