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). The extinction resolution measured 1600-1800 lph in the whole FL range, That's a dismal performance. The good news, everything else is very good about this lens. The colors and contrast are outstanding.
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. It's very soft across the frame wide open, and doesn't get much better until closed to f/8 or so. That pretty much true in the whole focal range.
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. I bought mine with a 3 year protection plan on another site because I read that Pentax had had some problems with the lens; they were supposed to have fixed it--but I will use it so much I just...
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. If you are looking to upgrade from the kit lens look no further. This is an SDM lens ONLY no screw focus, so it may not work on the very old DSLRs.
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. The zoom range is just about perfect, and the focusing is fast, accurate, and quiet. The hood is nice and works well, and the build quality is really excellent.
Summary: I had a K10 and upgraded to a K-7 a while back. The K-7 offered an extremely quiet shutter and I wanted to match it with a quiet lens. This is where the 17-70 comes in. It's extremely quiet b/c of the SDM and it complements the K-7's quiet shutter very well. I've had this lens for about 2 years and have had no problems with it. Have taken well over 15k pictures with it and am loving it more and more.
Pentax 17-70mm f/4 AL IF SDM SMC DA review by dawsonjm
27 March 2011
Summary: This lens has rarely been off of my K20D since I bought it last summer. It has a great range, and is a great upgrade from the kit lens. It is not as fast as good primes, but in our dusty climate, keeping the lens on the camera saves a lot of heartache about dust on the sensor. I just bought the DA*60-250, so this will be the perfect companion lens. I have not done any testing, but I think that the photos with this lens have been of superlative quality.
Pros: Sharp, reletively light, great color and IQ.
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. Just over a year later the lens has the same focus problems. I have since bought a third party lens to replace it. I've wanted to buy other Pentax lenses, but I'm afraid I will have the same problem.