On Sat, 1 Aug 2009 09:13:29 -0400 paul stenquist wrote: > > > From among many Pentax purchases, both used and new, I've only had >serious problems with one item. My first DA* 16-50 couldn't achieve a >flat focus field. It was replaced by B&H. The second one was excellent.
I still have my first one, it has a minor problem in that it does not focus perfectly to infinity at 16mm, otherwise it is great. I decided to keep it as is. The problem is easy to work arround. (and no problem at f/8 or so :-) >When I first bought my 20D I noticed front focus problems with the FA >50/1.4, so I tested all my lenses and fine tuned the focus. Most >required slight adjustment. I haven't noticed any focus discrepancy >with the K7D, so I have yet to perform any tests. But I'll probably do >a bit of testing when I have time. I had the K10D, before so no good way to correct. Now with the K-7, I did a check for my faster/longer lenses and was a bit shocked that the first try (with the FA 31mm) needed the FULL -10 correction (end of scale). Going through the rest, it got somewhat better, but many showed a quite noticable improvement in a brick-wall check after dialing in the measured correction. So it certainly it is worth the time and effort (took me about half a day for all lenses). Just FYI, these are te corrections I needed: FA 31mm 1.8 -10 FA 43mm 1.9 -2 FA 50mm 1.4 -7 DA 70mm 2.4 -6 FA 77mm 1.8 0 FA 85mm 1.4 -5 FA 50mm 2.8 macro -4 DFA 100mm 2.8 macro +2 FA 200mm 2.8 0 DA 300mm 4.0 +5 FA 400mm 5.6 +5 FA 28-105 PZ -4 FA 24-90 -4 DA 16-50 -7 DA 50-135 0 Front/Back focssing checked with a ruler-like A4 print under 45 degrees with a single bold line to focus on. Regards, JvW ------------------------------------------------------------------ Jan van Wijk; http://www.dfsee.com/gallery -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
