Originally posted by cupic Yes I have also founf that after connecting my sigma 17-70 it too had AF problems
Went to take a shot of a piece of white paper to see if any dust is present and its going in out in out etc
Is this fixable with firmware updates
cheers
That isn't a firmware problem.
Shooting white paper with AF will cause problems as you found. Use Manual focus because the AF sensor often cannot find anything on smooth white paper to target.
I actually find that shooting at clear blue sky (with MF) to locate dust works better.
If you are worried about Front Focus FF or Back Focus BF issues, you will need to target a solid object, focus on it, shoot it and then look at the picture on your PC screen (better for detail than the in camera LCD). If your object is sharp, you don't have a problem, if whatever is behind your target is sharp instead of the target, then you have a BF issue and vice versa.
Hope this helps.
Edit Note: Forgot to say, if you think you have a BF or FF issue, I recommend you don't screw with reflashing earlier firmware versions to get that maintenance menu as many have done, some successfully, others not. Take the trouble to send it to Pentax for repair, otherwise you may not only void your warranty, but screw your camera as well.