Originally posted by MAS_ttl Oh, oh. My wife gave me the funds for my birthday that would just about cover this! But I was just about to pull the trigger on a used Pentax 12-24. I have seen some great photos with both and read so many reviews that I am completely confused. Anybody have real life experience with both lenses who can weigh in? (BTW, the 8-16 seems like it fits so perfectly with my set-up - Siggy 17-70, Siggy 70mm macro and Pentax 60-250. No overlap like the 12-24, but sharpness and ultimate flexibility - arghh!)
Based on what you own (a number of Sigmas), you probably want the 8-16. The only reason I sold mine was I don't like Sigma rendering as much (the next time I need WA I'm considering a Q7 (or later) and the 08, believe it or not). But in every way, including build quality, I was extremely impressed by Sigma 8-16. About the only advantage of the Pentax 12-24 is it has a faster aperture and rendering more typical of Pentax or Tokina. But I just don't think it's as good a lens. The only competition for the Sigma 8-16 is the Tokina 11-16, but of course that's not available in Pentax mount. All the other WA zooms fall short of producing pleasing images, IMO. To do any better, you have to go to a FF lens (and the corresponding body), such as the Nikon 14-24 or the Sony 16-35. But now you're talking at least 3 times as much for the lens alone. The only other top-quality options I can think of are the DA15 or a Fuji with a Fuji 14mm or Zeiss Touit 12mm. But the 8-16 fits in perfectly with your kit.
Just be aware that you'll usually be shooting it around f/6.3 for optimal IQ, so you're not getting faster apertures like your other lenses have. But when you see the IQ I doubt you'll have a problem with it. Shooting is easy - manually set focus to between 3' and infinity (usually right at infinity), f/6.3, zoom, and compose. That's it. Very sharp images come out. Can't beat this lens between 9.5mm and 16mm (and what other lens goes wider than 10mm anyway?).