Originally posted by woolcotm Was there ever any conclusion to this? I am experiencing exactly the same issue. AF is spot on at shorter distances which is why I hadn't noticed it (cause I use it mainly for portraits) but it back focusses more and more the further away the subject is. This weekend I took quite a few shots at an athletics meet and even the static shots (subjects standing still) show quite bad back focussing. Using a K5 BTW.
I never updated the posting, so let me share a few things I learned along the way. First, I should thank Marc, and encourage you to pay attention to what he is saying here. In general, the problem was the user (me). I don't see it much anymore because of the following:
1) I purchased a magnification eyepiece and a split prism focusing screen for my K20D, and I shimmed the screen. While I did that to use my manual lenses, it also helped me to better see where the camera AF system was really focused. That, in turn, helped me to adjust my technique to operate within my camera's limitations. Incidentally, I still use the magnifier on my K-5, but I have not yet invested in a split prism.
2) For shots with distant targets (like my example), I typically use f/5.6-8 now to give myself a little more leeway. This is also helped (for indoor shots) by the great high-ISO capabilities of the K-5.
3) I switched to using the AF button to focus (in AF/C mode), then letting off when I am sure I have the target. I also pre-focus a lot more.
4) I practiced with the AF system on a plain background with a small high contrast target to understand the size of the focus points. I normally use center focus only, and was suprised to find that the center cross was larger than I expected, leading to it sometimes choosing the wrong target.
5) I read up on how the focus logic works, and started looking for high contrast items in my frame that could confuse it.
6) For tricky shots, I found out that prefocusing using zoomed LiveView and manual focusing never fails. This was very helpful for indoor diving events (low light, fast shutter, moving subject).