HD Pentax-DA 21mm F3.2 Limited
Distortions
At typical shooting distances, the DA 21mm Limited shows a small but noticeable amount of barrel distortion.
Compared to other fixed-focal length wide angle lenses, the amount of barrel distortion is average for the DA 21mm Limited. The distortion is higher than many zooms at 21mm, which typically move from strong barrel distortion at the wide end to pincushion at the long end. The 18-55 or 18-135 WR lenses will likely show stronger barrel distortion at 18mm but less at 21mm.
In a brick wall test using automatic distortion correction on the K-5 IIs, the original image shows a typical effect, most obviously in the corners. The before-and-after shots below were taken from about 2 meters away. Larger versions of the shots below are available here (uncorrected from RAW) and here (corrected JPEG).
Verdict
The DA 21mm Limited shows average barrel distortion, in-line with most other wide prime lenses but perhaps worse than comparable zooms at 21mm.
