funny this thread popped up when it did,as i feel im facing similar problems with mine.
although i dont get the loud grinding on af.
focusing on close subjets appears fine,but when i try autofocusing on something a little further away i can see quite clearly through the viewfinder its out of focus
i can turn the focus ring a little and it appears in focus,then half depress shutter
and it focuses slightly out?
manual focusing seems ok,but from what i hear this lens should be sharp.
and it doesnt really seem that sharp,especially at f/4.
im pretty sure im experiencing some sort of focus issue with this lens.
every other lens on my k-7 locks its af accurately...what gives.
well im going to send this to cr kennedy for a service anyway.
here is a sample of mine at f/4 1/500th autofocused on the piece of grass sticking up in the middle