Originally posted by sibyrnes It looks like it's going to be a long time before Pentax comes out with a new wide angle prime.
i think Pentax is working on a prime between 20mm and 28mm, and it should come out by [
extreme speculation, do not quote] sometime 2018, after the 50mm and 85mm. But yes, that is still far away.
Ultra wide angle FF primes:
Samyang 14mm, 20mm, 24mm, (and others, but those are telephoto)
Irix 11mm, 15mm
Venus 15mm
Zenitar 16mm (fisheye, old, but some people produce good photos with it. Very affordable)
I think a couple users on this forum mentioned the Samyang 20mm being pretty good. You can check the Samyang lens club thread?
I have M 28mm. Some say its the worst 28mm that Pentax ever made, but I still find it good! It is acceptably sharp on APSC. If you buy F 28mm you should be doing fine. Those are sharp and have AF.
I also have Samyang 14mm. Super sharp lens! But buy it from a reputable store, because QC was a problem with Samyang. Many of us had to return a Samyang 14mm because it was decentered (part of frame being unusually blurred because a lens element is out of alignment). This is often a problem with Ultra wide lenses in general, but you should still hope for a good copy of the lens.
One final thing, Samyang is also sold under some other names like Rokinon, Bower, ProOptic, Walimex, Falcon.. sometimes even the same store will sell the same lens, with different brand label and different price. Optically, these are all the same. Usually they even look the same on the outside, just with a different brand label.
That said, if I had FF and was looking for ultra wide, I would go with Samyang 20mm. I trust their optics. 14mm on FF is awkwardly wide, and 20mm is more useful. You will have to get all the others anyway, some day