Originally posted by Just1MoreDave I have the Sigma that's one (I think) generation older than what's available new. It's got a 58mm filter, 7 blade aperture and focuses to a more ordinary 0.3m. Mine happens to be manual focus. Yesterday there was an AF version of this lens in the marketplace, but it looked like it was going to be sold. It has taken me a while to warm up to this lens but the more I use it, the more I like it. It's very sharp, as sharp as anything else I've seen at 28 (mostly the cheaper end but still). It doesn't fall off on the corners dramatically like the Sigma 30/1.4, and works well. I even like the focus ring despite its short throw. Because the lens is so sharp, the viewfinder has a real snap into focus feel that you don't get in ordinary 28s. Now the only dislike I have is size, though this lens is not huge.
I wouldn't ever use the new one, it is just too big, but that is just a personal thing. Otherwise it's supposed to be better, and focuses closer. It's pretty easy to find a use for a fast sharp AF 28mm lens, and not a lot of Pentaxes to look at here.
I have the AF version of this lens. I kinda am thinking about selling it since I got a DA 35/2.4. The Sigma is faster and I think 28mm is a little more useful focal length on APS-C, but the Sigma just isn't all that sharp below f/4. It also has somewhat muted colors. My Tamron 17-50/2.8 is sharper, whereas the DA 35/2.4 is definitely sharper than the Tamron. So while the Sigma is faster, the DA 35/2.4 at its widest aperture is way sharper than the Sigma at the same aperture.