Summary: Bought this lens with some trepidation because of concern over SDM failures. I "needed" a lens in this range and 3rd party lens makers really didn't have what I wanted. There were reports that the SDM was remodeled in 2012 (hope that was true and not industry talk) because of the failures in both the 16-50 and 50-135 models (shared the same SDM design). It was well into 2013 when I bought this lens.
If you are considering buying this lens dont hesitate, highly recommended.
9 June 2013
Summary: Purchased this lens to replace a 70-200 f2.8 which I found to be heavy and difficult to handle. I use a K5 camera with grip, this lens is just perfect, balances beautifully with this camera and the 50-135 focal length is so much more useful than the previous lens. The IQ is simply fantastic and has that certain quality that make images really pop. Autofocus on the K5 is fast, virtually silent and very accurate.
Incredible lens. Makes a great k-30 body into a stellar performer.
4 June 2013
Summary: Bought the lens following the glowing reviews. Never been happier. Lens is on a k-30. Had to adjust focal distance. Mine is at -4, following which the pictures are absolutely breathtaking. The colors are vivid, coloration is natural, not yellowish as on canon L lenses, and sharpness is unbelievable. I can count dimples on a subject's face, and sift through individual hairs. Took a few pics of woodpeckers. Can count the feathers.
The best mid-range zoom lens made for Pentax DSLR cameras, period.
14 December 2012
Summary: I used to own this lens, along with a K-7, and a K20D, until they fell victim to someone who felt that they deserved them more than I did. I will spare you all the details. All I will say is this: Protect your camera equipment! That being said, the lens was the best mid-range telephoto lens I have used in over 40 years of taking pictures, 35 of them with Pentax SLR cameras. I don't worry much about what a computer can see, but my eye can't.
Summary: I was using pentax limit lens (DA 40 and 70mm), which gives great result in small body. Then decided to try star lens; works well, gives good result and provide different view with prime lens. Although I am still takes DA40 for going out mostly, use of this zoom lens is increasing. Most satisfying factor is telezoom with good IQ, to summarize.
Summary: It is the second copy of my purchase. The first copy has problem on focusing and I return to Amazon. Amazon has prompt response and returned a new copy to me just after "THREE DAYS" I have sent my "return goods" email! This is a wonderful service for me. For the lens, it is not fast focusing as my other lens DA180-135mm, DA70mm. But the others aspects are much better. The focal length is perfect for a walk around lens if you take no much wide shot.