Originally posted by house Tweak the design to prevent wobble over time. All my limited wobble a fair bit and could be a bit more robust.
I wouldn't change any of them optically. For the size they are well judged. I'm annoyed with my da 15 but I realise I should just get another, non limited, lens. But there isn't a wide angle prime for pentax FF or apsc. I would consider FF if there was a good AF wide/uw prime.
The DA 21 and DA 14 are both wide angle primes available new today. There are a lot of options on the used market from 28mm and wider; 20, two 24's, and 28 from Sigma, a 24 and two 28's from Pentax, and the Tamron 14 FF lens (that is probably quite rare, I never hear anyone talk about it). Maybe something I'm not thinking of but those all exist and all have autofocus.
What annoys you about the DA 15? It seems like a polarizing lens, that people either quite like or quite don't. Those kinds of situations exist with other lenses, like the FA 43 or DA 35 f2.4, where as there are some lenses that everyone seems to like, like the FA 77 or M 50 1.7.