Having just shot and processed my first batch of K-5 photos over the last couple days, here are my first impressions:
1. AF speed and accuracy are both much improved over the K-7 and other Pentax dSLRs. There's very little of the "doublechecking" found in previous Pentax AF systems. It just finds the lock and sticks it in one motion. NICE.
2. Noise levels are spectacular at base ISO (as you'd expect) and all the way up to ISO 3200. ISO 6400 is plenty usable with minimal NR, and 12,800 and 25,600 are useful with work from something like Topaz DeNoise.
3. In RAW, the headroom is roughly equivalent to that of my D700. This is simply amazing from an APS-C sensor.
4. The Sony sensor seems to render slightly cooler images than the Samsung sensor in the K-7 and K20D. I have the feeling it's more realistic, but having "seen" color in a certain way for a few years it's interesting trying to adapt. (I had a similar experience with the K-x's color output.)
5. I don't see any softness at 100% due to the 16mp resolution. Really quite stunning in the sharpness department with the right glass--lookin' at you, DA35 Macro.
6. The shutter is even quieter than that of the K-7. Seriously quiet and quick.
7. More to come as I do more shooting, I'm sure...
Here are some images. These are all processed in LR3, some quite heavily. I'm not going for test shots here. I'm just going out and using it and developing the photos as I would from any other camera:
(Thanks, Kristin)
(Thanks again)
(100% crop from color version of above photo)