This was what I found out when calibrating my DS (applies to all Pentax DSLRs with 11 points
AF sensor), and might help you a little. I strongly suggest using a standard prime lens and outdoor near infinity target as a starting point. If you try to calibrate the camera with close-up distance printed target, you will soon run into inconsistant and unreliable results. Mind you that these screws have been threadlocked from the factory so you might do so too once you are certain the recalibration was accurate.
