Originally posted by campdog Im still putting my lens kit together and thinking of getting a Pentax Prime wide angle lens or a wide angle zoom. I have a Sigma 10-20mm but thought someone might know of a better lens.
As has already been noted, the UWA lenses currently sold by Pentax are the DA 10-17, the DA 12-24, the DA 14, and DA 15. I have three of those four lenses (I don't have the DA 14). Of those lenses, the 15 is overall the best, although not by much. It has a little more sharpness and clarity than the DA 12-24, and is a slightly more consistent performer in terms of handling distance and lighting challenges. The DA 12-24 has impressive corner to corner resolution up close, even at 12mm; but at distances much longer than 20 feet, it quickly loses resolution toward the borders as the distance increases. The DA 10-17 is not as sharp as the 15 or the 12-24, but has the same stunning color rendition and overall rendering.
I don't have any first hand experience of either of the Sigma 10-20s. From images I've seen of the first Sigma 10-20, I would say the Pentax glass has better color rendition, with deeper, more brilliant blues and darker, richer greens. However, if you're satisfied with the images you're getting from the Sigma, I see absolutely no reason to exchange it for a lens with the Pentax label on it. Perhaps the best plan would be to get the DA 10-17 as a compliment to the Sigma. If you find yourself preferring the colors and rendering of the 10-17 to the Sigma, then replace the Sigma with either the DA 12-24 or the DA 15.