Originally posted by luftfluss It looks like the photo with the smokestacks was severely underexposed. Picasa will boost the exposure to what it feels is the correct level, but this will of course increase noise.
Yes, that's a big problem, Picasa auto adjusts levels when displaying raw images, and is very heavy handed with it. Aside from that, Picasa is designed for processing jpegs, not raw files. It is only working on 8 bits, losing the extra bits the raw file contains and therefore compromising noise levels in processing.
Immunogirl, you need a proper raw conversion program. I suggest you use Pentax Lab that came with the camera. It does a great job and diretly translates camera settings. The new version also has a Dodge control for boosting mid tones that is extremely useful and is not available in Picasa.
I clicked on this thread because I have an 18-135 that performs very well. By that I mean it slightly outperforms my 18-55 and 18-250, both well respected for what they are. I have to run +10 on my auto-focus. Maybe you need to calibrate as well. So far it's very unclear whether you have a lens problem. I see possible motion blur and exposure issues, and poor conversion. The smokestack photo looks like the focus was in the foreground and the industrial plant is in the bokeh. You're going to have to do a proper lens test before you can determine what is going on.
Get out your tripod or set the camera on a table. Shoot in jpeg to level the playing field. You won't be ajusting any parameters, so raw is unnecessary. Set the shutter for 2s delay and shoot a target with a clear focal point. Mount a couple of comparable lenses and repeat. Check focus performance and adjust if necessary. Until you do that, you're just guessing.