Originally posted by Kevin1961 I did not engage the 2-timer for mirror lockup.
You should when using a tripod, if at all possible. Not overly convenient for portraits, of course, but for landscapes & architectures, absolutely. I suspect that's why one of your shots (70mm, I think?) was noticeably softer than the rest. Oh, and engaging the 2-second timer has the side effect of disabling SR for you. Also, I forget what aperture you were at, but most lenses do better stopped down a bit.
Between all that and what could be some atmospheric effects, I don't doubt that the lens is capable of a bit better.
Quote: One thing I did notice that the pentax does seem a little more open to haze.
Haze is haze - no camera can eliminate something that is really there. Ditto with heat effects. If they are there, your camera will record it. If it didn't, it wouldn't be very good! You wouldn't the camera similarly deciding it just didn't like the nose on one of your portrait subejcts similarly deciding not to include it in the picture, either.
I think you just had the misfortune of doing test shots on days when atmospheric effects were especially problematic.