Originally posted by MarkJerling A wide angle zoom does seem like a good idea.
I think for the K-1 the D-FA 15-30 is the ultra wide zoom with the best capabilities. They guy selling the 12-24 mostly uses a K-1, and said the limitations of the 12-24 on full frame was one of the reasons he was selling it. (Apart from the fact he likes to take lots of photos of waterfalls, and it's not WR).
My experience is a wide lens is particularly useful in narrow, steep sided valleys, for real estate where those tiny in-fill homes are made to look like country estates, and for urban architecture where there are a lot of tall buildings and confined spaces.
Here's an image I captured yesterday at 12mm.
It's under 10 minutes walk from home, and I was able to jump across the stream, and in some places just about get a foot on both banks. About 3/4 of the year there's not even any water in it.
It was late in the day when I took it, so light was a bit flat, but as a B&W conversion, I rather like it.
I had my tripod in the middle of the stream and I think I was balanced on a rock. I simply couldn't have taken this without an ultra wide lens.