Originally posted by noelpolar Fwiw.... I have a view that... say.... from K5 to K3 to K1 to KP that the AFC has not been worth chasing through these camera models (to any great extent).... so I can understand this feeling. Off course.... I'm quite confident that this camera will provide a more pleasing AFC experience in combination with it's other refinements.... so I have purchased one.
I would differ somewhat with Noel, for my use I have found significant improvement in AFC across my cameras (K20, K5, K3, K1ii). Over the years, I have had regular need to photograph basketball (many games), track & field, soccer, Australian football, rowing. I generally use back-button focus with AFC 27 Sel centre point. My process is to centre the viewfinder on the athlete, hit and hold the back-button and hit and hold the shutter (continuous shooting). If the camera loses focus on the subject then re-hit the buttons. Since the K3, in my experience, AFS does not come close in performance to AFC for moving sports, I would never use AFS for sport (or BIF) and it surprises me that others find AFS preferable (I can only think that it is technique or setup or both?). I am looking forward to the K3iii and expecting a further decent upgrade in AFC performance (and 11 fps will be fantastic).
A few weeks ago I photographed some women's softball and took a sequence of 15 shots as a player ran from 3rd base to home. Using the K1ii and DFA 150-450 at 250mm/ 1/2000s/F7.1/iso 400-640, I was positioned (~25m) behind the runner (she was running away from me) and all 15 shots were sharp. The 1st , 5th, 10th and 15th shots are shown below. You can see in the 1st shot that the home base is clearly out of focus and the camera tracks the runner perfectly to beyond the home base.
I find, for my use, that the AFC in the K1ii works well (its not 100% but I am rarely disappointed by missing a shot due to focus).
The K3iii has been a long time coming but I am confident it will be worth the wait.