Pentax K-30 Digital Camera Review
We tested the Pentax K-30 with the weather-sealed 18-135mm lens, which is available kitted with the camera for a little over $1100 (as opposed to the $899 standard 18-55mm kit). The 18-135mm lens follows designs similar to those from other manufacturers, and we found some of the same problems. Its longer focal length exacerbates diffraction, especially at longer focal lengths and smaller apertures. At f/40 and 135mm, sharpness is practically nonexistant away from the center of the image.
If you're going to shoot with the 18-135mm lens, we suggest trying to keep the aperture around f/8-14, as wide open and closed down we found the lens had significant issues in the corners. This kept the K-30's sharpness score down, but we found the camera had no problems when shooting with a sharper lens, such as the 35mm f/2.4 prime lens. More on how we test sharpness.
Stabilization was quite good on the Pentax K-30, showing significant improvement with the feature activated as opposed to leaving it off. We tested stabilization with a repeated shake pattern at 1/30th of a second. With stabilization off the average image was not sharp at all, but that was relatively improved with the stabilization active. When shooting handheld in limited light at that shutter speed you should see similar results.