I just got a 5D II camera and I am unhappy with the performance of my new Canon 17-40 L with vignetting at 17MM even stopped down, and pretty bad softness and chromatic fringing on the edges. I am going to return it to B&H. Since I bought this lens just for the wide end and since I won't use it often, just for landscapes that require a super wide, I was thinking of a prime wide angle. The Canon 20MM F 2.8 is probably not wide enough (I have a 24-105) and gets horrible reviews. The 16-35 is not much better than the 17-40 from what I've read. However, I am interested in the Zeiss 18MM. manual focus only, but who cares in an 18MM? Kind of expensive, but cheaper than the Canon 16-35. The only other option I see is the Sigma 12-24. Anyone use either the Sigma 12-24 or the Zeiss 18MM?