Originally posted by normhead Thanks for posting, I have Pentax 10-17. It has lots of distortion, I'm looking for correction for both CA and barrel distortion, for landscapes.
Any camera after the K20D will do CA and distortion corrections. When I was trying to decide between the 14 and 15mm, I read somewhere on these boards that the 15mm barrel distortion is corrected by Pentax software, whereas the 14mm's moustache distortion is only partially corrected. I don't know for sure if that's accurate.
I ended up choosing the DA 15mm Ltd based on size and the rabid fan club here. Frankly I don't see that it's as wonderful as the fans. Mostly I like it because it's small compared to other choices like 12-24, 16-45 or 14mm. I often carry the 15mm, but I don't mount it all that often. If 16 or 18mm is not wide enough, 15 won't likely be either. The 15mm has lower distortion, better flare resistance, lower CA and more contrast than my 16-45, 10-17 and 18-135. These are nice features, but are secondary to FOV, IMO.
I believe you have an 18-135mm. These samples might help put the DA 15mm Ltd into perspective:
https://picasaweb.google.com/bonhommed/Comparo?authkey=Gv1sRgCLOD9LjmoOKTlAE#
I'm not trying to dissuade you from the 15mm, but to be happy with it, choose it for its particular strengths. I won't be getting rid of mine, it's nice to have a compact, high quality superwide to throw in the bag.