The arrival of a Sigma 70-200mm f2.8 HSM yesterday and a bit of sun today meant I could see what the af and tracking abilities of the K-5 really are. Where the 55-300 desperately whirrs and attempts to keep the subject in focus as it comes towards you, the HSM of the Sigma just works...silently! Experimenting with what I had...dog running towards me...flying birds etc.... Not the fastest of subjects, but it was easy to capture a series of a dozen or more in focus shots as my dog ran towards me. I tried this three times and each time the camera was capturing this number of shots before totally losing focus for around 3 shots - re-capturing focus and producing more in focus pictures - I'm assuming this could be down to the very slow card I was using.
I also tried the 'Alice chasing ball' test again - not easy to do when you have to throw the ball and then try to get the camera to your eye in time to get the shots! Again no problems other than the usual user errors.
Compared to the D300s with AF-s or HSM the K-5 does'nt perform too badly at all - although I'm sure for the really fast stuff the Nikon is still the best option. The fast fps really feel nice and smooth thanks to the lovely feel of the shutter. I think Pentax have upped their game af wise with the K-5 but it probably means paying out a bit for lenses if you want to take full advantage of the increased performance.
a few mainly cropped shots
http://www.flickr.com/photos/greypoi...th/5252751986/