Summary: I'm Mary's husband, and the lens was purchased for me. Some of the reviews this lens has received mention a lot of color fringing at edges of high contrasts in the scene. This individual lens exhibits very little of this optical fault. At 12mm on an P:entax K5, the 90 degree wide angle is very good, and 24mm it's a moderate wide angle and excellent. It will be very useful for building interiors and wide overall scenic views.
Summary: I don't know why there isn't more love for this lens. For shooting landscapes you can't beat it - typical Pentax IQ rendering and super sharp. I am not much of a prime lens person, so this works out perfectly for landscapes for me. I read many reviews, and this lens is supposed to rival or even beat the great DA 15 Limited. Yes the lens is pretty big, but I am used to larger lenses since I shoot mostly with my DA* 60-250 and DA* 300 on my gripped K-5IIs.
Summary: Works perfectly. In my case though I find it too big and I use the 15mm from Pentax instead although this one is more versatile. Guess it's a matter of preference, so if you can live with the size I'd say this is not only more versatile than the 15mm, the pictures are also sharper on this beast.
Summary: I am still learning how to use it, but this is a wonderful wide angle lens and takes fantastic pics of landscapes and structures. I shopped around quite a bit and did lots of research. I always kept coming back to the DA 12-24 for my Pentax K-x digital. The only thing that kept holding me back was the price..... much more than anything else. I have a wonderful zoom lens made for Pentax and like the feel and weight of it.
Excerpt: I use this lens a lot for landscapes and it works great for me (mostly). The only problem is the front light flare, that in some cases is disturbing.It is a big and heavy lens compared to DA15, but it's also more versatile. The field curvature is quite well handled if shooting horizontally, but starts to bother if the camera is inclined.
Pros: Consistent Output, Durable, Fast / accurate auto-focus
Summary: Very useful zoom range for digital. Very little distortion. Very sharp, except in the very corner. Excellent color rendition. Bad purple fringing but very easy to fix in pp. 5 stars because pf is so easy to fix.