Originally posted by osv that lens is a bad choice for landscapes, the sides are a blurry mess at landscape distances... the heie review clearly shows the problems.
Here is a shot I (accidentally) took at f2.4. Its focused on the front row of the houses:
f2.4 landscape whoopsie
At f2.4 and focused near infinity, I wouldn't expect much from a lens under $220. But it surprised! DoF is way more shallow than at f8 of course, but it is full of detail, sharp. And if you check here, it works on FF as well:
https://www.pentaxforums.com/forums/54-pentax-lens-articles/31629-da-lenses-f...ts-thread.html
In the thread I linked earlier, there are plenty of great landscape shots. They seem to be sharp enough. I think your words "a blurry mess" are too harsh. Lenses like Industar 50-2, now
there is a blurry mess.
The FA 35mm has the basic same optical design if you look at the lens formula, but I guess its a little better suited for full frame (ie, might have sharper edges). That's why I mentioned it; some say its sharper.
The non-art Sigma had some kinds of problems:
https://www.pentaxforums.com/userreviews/sigma-30mm-f1-4-ex-dc.html
And the Sigma 30mm art has some cons, as well:
https://www.pentaxforums.com/reviews/sigma-30mm-f14-art/introduction.html
Is the DA 34mm f2.4 perfectly sharp across frame, free of CA? No. But (for my uses) its adequate and simple lens profiles can fix this really well. As far as I checked DXo, The Sigma 30mm has the same CA and higher distortion. But DXO didn't test the sigma on K-mount, so its difficult to compare CA and resolution directly.
Edit: I take the vast majority of my landscape photos with DA 35mm f2.4 and Samyang 14mm, and sometimes M 28mm f2.8. But of course I'm no pro. There is my bias