15mm limited
Hi there
Whilst testing out the 18-135, I popped the 15mm limited on the tripod as well. I have a nice test area which gives quite a lot of depth with detail at each depth.
As reported, this lens is soft on the corners at f4 - as Tom? suggested, I think this is more to do with curvature of field than an optical fault.
Basically, my test shot is of a shed, with the foreground coming towards you, and trees going away at the top.
The top corners (away from the point of focus) were actually quite sharp, whereas the bottom corners were very soft. This has improved by f5.6, and is really not an issue by f8.
The centre seems to be really good at all focal lengths, as others have said, colour and contrast is excellent, and the lens is a lovely thing. Definitely a keeper.
Either the 18-135 or the 15mm will fit in a coat pocket easily, which makes it great to go out with the K5 and these two lenses.
I put my feelings on the 18-134 in a different thread.
all the best