This really is a sleeper among vintage wide angle offerings. I own and use it on both a K-5 and K-1, and it holds up nicely on the K-1. It's a bargain for a lens that wide and with this quality of optics. It is beautifully made and has that solid feel. Pentax never made an "M" version of this lens. They jumped from the "K" version to the "A," preserving the excellent optics that the K-series is known for. It is also a small lens creates a compact rig even on the K-1. This Nikon lens hood is the best one; no vignetting and still inobtrusive. All in all, someone ought to buy this lens; I'm perplexed that it hasn't been snapped up. We are not allowed to comment on prices per forum rules, so I can't say the positive things I wanted to say in that regard
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Let's give a seller and a fine lens a free bumpity bump.
Oh, and it takes 52mm filters, which is a real plus for landscape work. Unlike the new big wides and ultra wides that don't take standard filters.