Originally posted by clackers Odd. I don't have any camera focusing problems with either my K-30 and K-S1 at events (including a wedding workshop at a real ceremony). Any errors are mine. The cross point in your K-3 is as good as it gets in the industry, rated to f2.8 at light levels down to -3eV, so who would do this better?
I'm sure that you are fine with the K-30 and K-S1.... except when in low light or speed required, I never experienced focusing issues with my K200D, then I had the K-5 who wouldn't lock AF with DA300 but anytime it would lock the AF would be spot on. Then I got the K-3 who would lock AF much better than the K-5... but also the K-3 don't mind releasing the shutter when not in focus. My opinion on this: there were several repeated comments about Pentax AF that Pentax AF was too conservative versus Canikon AF, so I guess Ricoh relaxed the lock conditions. You don't seem to have a K-3, but if you had one, you could play a bit with AFC 27/9 points to see how it works compared to the former 11 points AF. Now, I also have to be honest: what I found out is that the Pentax AF works very well when the system is fixed (not hand held).
So I believe two things:
1) sensor based stabilization is a disadvantage, as far as AF lock and tracking are concerned, especially true with long lenses where any camera shake translate into huge pattern shift for the AF module
2) K-3 AFC algorithm is not what it could be. For example, AFC is unable to focus in continuous shooting if the defocus isn't close enough to focus position. The camera can't handle a direct press of the shutter when the focus is way off target and what it does is take photos out of focus. In burst mode, AFC, you can take 20 out of focus photos, the camera does it without question. So, what works a bit better is AFA: the camera likely starts with AFS (does not take out of focus shots if AFS is set to focus prio), and then switches to AFC tracking once the AF is in range and if the target is moving. Other solution is to use AFC mode and the back button AF to prefocus and then use the shutter.