Hi Mark, I thought about this a bit. Are you testing with autofocus? Are you letting the camera select the focus point? That would result in the kind of inconsistency you report. In any case, the centering problem has nothing to do with autofocus. It's an element alignment problem. Test at f2.8 or f3.5 and use manual focus. Focus on a target on the right side of frame. If your lens has a centering problem, the left side of frame should be consistently out of focus. Multipoint autofocus can't be depended on to produce consistent results, particularly if your target is somewhat uniform. Paul On May 24, 2008, at 4:41 PM, Mark Erickson wrote:
> Paul, > > I tested the lens using my K10D on a tripod. Test shots were done > at F/8. > During both sessions (before I sent it back and after), I did a > comparison > test with a prime lens. The first time, it was my FA 50 F/1.7. > The second > time it was my FA 43 F1.9 ltd. In both cases, the prime lens tests > came out > with essentially even sharpness across the frame. So I don't think > it's my > K10D. > > The lens and its mechanism seem solid, but I think that there is > something > about it (either design or manufacturing defect) that is just not > mechanically stable. > > --Mark > > Paul Stenquist wrote: >> If the problem was a centering defect, it should be consistent. How >> does it perform wide open? I'm surprised you're seeing any softness >> at f8. How about the camera your testing it on? Are you sure you >> don't have a mirror box problem? Have you tested other lenses on the >> same camera? >> >> I'm don't want to be a contrarian, but the inconsistency of the >> problem suggests it's not a centering defect. Of course I could be >> wrong, and I frequently am. >> Paul > > -- > 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. -- 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.
