A few years ago, I had a decent copy of the FA* 24mm f2 AL with a K-3II, and very much liked the combination although I found the croped angle of view (~35mm) did not suit me that well.
I really liked the build, speed, sunstars/lack of flare and just general look of the photos. Yes you have to stop down to ~f11 for corner to corner sharpness but I would anyway for landscape. My old copy was very sharp from wide open which I never had an issue with.
Some of the K-3II/FA*24 below
Pentax SMC FA* 24mm f2 AL [IF] | Flickr
Now I have a K-1, I have searched but did not find too many samples of photos with this combination. I have a D-FA28-105 and FA43 which get the most use on it, but looking for a wide-angle.
I have looked at the FA20, Voigtlander 20mm f3.5, FA20-35 f4 etc but I think the FA*24 should be ideal.
What are peoples real-world experience with the FA*24 on the full-frame K-1?
Cheers, Rob