My K-5 recently took a warranty serivce trip as it had a tendency to back focus in daylight (PDAF). With the DFA 100 a +10 AF micro-adjustment was just about enough, but the DAL 55-300 would have needed considerably more. The piece of paper that was in the box when I got a camera back (*) stated that they had updated the firmware (now at 1.11, was 1.03 I'd recall) and tested the AF with the result that it was performing fine and a remark that my problems may be 'caused by the lens'.
I was quite miffed by this as it seemed that in essence nothing had been done and this would mean that running out of AF fine adjustment range with a Pentax lens is apparently no issue as far as warranty service is considered. However I thought I'd test once more with a paper target, tripod etc (before getting in touch with the seller again). Turns out the DAL now is fine with +8 and that +4 is enough for the DFA 100. (Tamron 17-50 1:2.8 : -5 BTW).
It *could* be that they in fact did something else besides upgrading the firmware and testing AF to fix the reported problem and failed to put that in the service report. However, if the latter is to be taken at face value, it would seem that just the firmware upgrade to 1.11 had a profound positive effect on my problem with backfocus.
(*) This took just a couple of days which was a huge positive surprise
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Last edited by jolepp; 11-15-2011 at 04:14 AM.
Reason: typo