Originally posted by mattieyp3 Good points. I did think of the depth of field issue due to the fast lens. Originally I used a test chart for focus accuracy. This got me to place my AF fine adjust at +10. But as I investigated my images more recently, it revealed that items closer to the camera were in slightly better focus. That was my clue to the continued problem. And I thought this meant I needed to got to +12 in the adjustment menu (which is impossible in Pentax). As the first reply above mentioned, I needed to dial back to maybe +8, thus moving the plane of focus backwards.
At this point, I'll experiment and pay close attention to my images hoping that this helps. I still wonder if a labs' lens calibration is valuable. Hopefully +8 will get me better focus. Thanks.
What camera are you using? My guess is, before you answer, that you are using a K5, K20 or K10.
I have the same lens and know the same problem. I tried adjustment etc but never really got that consistent sharp shot that I 'know' you can get (just as you say).
Then, by chance, I had to use my K30 body one day. BANG, focus every time. Sharp and consistent.
My bet is the AA filter is playing a role, as are the AF inaccuracies reported for the K5. The K30 has a weaker AA filter (so I hear) as does the K01 and, if true, I can say it makes a difference. Both the K30 and K01 deliver sharper shots than my K5 - although the K5 does give me more in other areas .....
Anyway keen to know what camera you are using.
Mark