Excerpt: I bought this lens in the May of 2012, it was used. And I bought it for my brother, who is also Pentaxian. Because he has Me as his elder Bro. Before making this purchase I already had FA 16-45 and Kit lens and some others, so I had an alternative and also tried and was looking after other Third party lenses, and actually was thinking about Sigma as a better choice.
Summary: I needed a weather-resistant wide-angle for my K-5, and certainly got it. It features a fast, quiet autofocus, and takes sharp, well-coloured images. On the downside, it's pretty heavy, and a little hard on the pocketbook. I bought it because I needed the weather sealing, but if that's not an issue to you, a third-party lens might serve you just as well, for a fraction of the coin.
Excerpt: The good news is that with the new k5iis there is an improve in focus speed. It is now comparable to 18-135 testing them one after another. Ca @ f2.8 has also reduced using the new body. Overall sharpness increased as well.
Excerpt: I had a copy of this lens for work. The first thing you notice about it is that it is big and solid with a lot of inertia. It seems to weigh more than the camera body, possibly because much of the weight is towards the front of the lens.
Excerpt: I believe my copy back-focuses 1/2 to 1 inch, so I can't provide strong comments on its performance below f5.6. It strikes me as soft at 2.8, even accounting for back focus. At f4.0 its good and at f5.6 fantastic. My suspicion is that its excellent down to f4.0 and good at f2.8, but I haven't gone through the trouble yet to adjust the K-x.
Excerpt: I want to tell my story. It has the happy end but sad beginning. At the moment I mounted this lens I thought "wow!". That "wow" was more about its appearance, build quality, big front element compared to the crappy 18-55 DA L (it was given me for free while I was awaiting for the 16-50 arrival). First sessions, however, faded the impression quite a bit. Sharpness was.. average when stopped down to f8-f11 and very poor wide-open.
Excerpt: Very sharp for a zoom, contrasty, great colour rendition and bokeh is good most of the time depending on subject matter. It seems that bokeh suffers a little with highlights, but overall it is very good for a zoom.