I've had a k100 for a couple of years, and have now added a k200. I'm kind of unhappy with the quality (resolution, mainly) of the k200 photos. I have some comparisons here, same lens at iso 200 f8. The k100 originals were pef, the k200s were dng. These are small crops of the upper-left corner of the images as jpegs derived from raw via gimp/ufraw. It's probably obvious, but the top is the k100, the bottom is the k200.
These were shot at 16mm on the f4 Pentax 16-45mm lens (at f8.) There is a dramatic fuzziness on the left side of images taken with the 10-20 f4-5.6 Sigma at 10mm, which I had at first blamed on the Sigma, but now I'm not so sure, since, at similar image sizes, the problem is apparent with the k200 but barely with the k100. The fuzziness difference from side-to-side is much less dramatic with the 16mm than with the Sigma at 10mm.
I'm making all my comparisons after adjusting for relative magnifications, to avoid giving the k200 a disadvantage by viewing them both at 100% or whatever.
Besides resolution, the k200 appears noiser (here at 200.) And, not that it matters that much, but the color balance under all conditions seems to require a lot more manipulaton (again, based on raw), but there are a lot of variables there, so I'm not as concerned about that. Not that it might matter much at 10 or 16mm, but the focus was identical for both images. These are just a couple of about 20 tests I did - the results are pretty consistent.
I realize that there were some differences involved in resizing etc., due to the differences in the native resolution, but the difference visible here is very much similar to the differences reflected when viewing the original raw images.
Comments/suggestions?
Paul