The camera problems just don't seem to end this year. I'm really running out of gear to break or fail on me. So in need of a walk around zoom I ended up with a used 16-45. Initial inspection seemed ok on my k-5, but then my k-5 started to fail this past weekend. My k-7 needed a good mount ring so I took the one I had off the k-5. As a side note, getting ahold of the parts department is nearly impossible. Now with a good ring I should have good focus registration right? The mirror box was never moved. With a 50mm on the k-7 it looks sharp across the frame. The 16-45 is a wholly different story. First of all I had to adjust focus to +7, where my k-5 needed no adjustment. Then I the slightly soft right side I noticed with my k-5 seemed greatly magnified to the point of uselessness. It is only at infinity though which tells me that the lens isn't decentered (actually at close focus it is superb), but instead maybe tilted off the focal plane. I'm thinking I can just shim it? Anyone have any experience with shimming lenses? Also if I sent it into pentax does anyone know what they would charge to align the lens? I'm guessing its probably about the amount that it is worth. If I focus on the right side, it gets sharper but never sharp at infinity. The left side starts to lose focus then, so I'm guessing the planes aren't lining up. It is most certainly distance related. It would seem that if a 50 prime looks sharp across the frame that I could rule out the body, though without a k-5 to also test with some more (and looking back at the k-5 shots with the same mount ring they have similar problems to be honest) its kind of hard to say my mount swap didn't introduce any problems. Oddly the focus shifts are somewhat random. At times the right side doesn't look so bad, but it could be that I was just at infinity where it looks best at any distance. If it moves off infinity even stopped down it looks awful until the subject starts getting close. I know its a zoom and not the greatest ever to say the least, but where it is sharp in the frame it is actually very nice. If I could just the whole frame sharp....
I guess I experiment with some shims.
Here is a link to the last picture I took.
imgur: the simple image sharer
Its full resolution for the pixel peepers. Thats at 16mm and f10. Everything should be sharp. Even a decentered lens sharpens up a bit at high fstops. I focused on the right side and it threw the left out. If I focus at infinity the left sharpens more, but the right goes soft. At first I thought it was field curvature, but the 16-45 doesn't have many issues with curvature. This is maddening. I just want a camera with a zoom that works. My 18-55 and 28-80 both have decentering issues. Of my k-5 was out of alignment. Hard to say. I should test them on my k-7. I'm tempted to just round up everything and send it to pentax and say "make it work" but hate to think what that would cost right now. I also can't be without a working camera on my person and the k-7 was my backup. I'll unseat the mount tomorrow and reseat it and make sure that its sitting in there as best as possible. Wide angles make alignment issues more apparent. So my options are try shims, send lens and camera back to pentax for pairing, or toss lens in trash and lose a few hundred dollars. I'll just add it to the list of things to fix along with my k-5, 12-24 (broken mount), M 28 3.5 (sticky blades), M 50 1.4 (filter ring fell off and is now damaged..looking for a parts donor), metz 54mz4i (blown bulb). That's been my year so far. If it weren't for bad luck, I'd probably have none by now.
Sorry for the long post. Wish I was just out shooting pictures again and not worrying about why half my image is mush.
Oh I tried a zeiss star and the out of focus donut looked decent. Aparantly if a lens is decentered the donut hole will not be aligned in the center. In this case it was at both extremes. As one user has pointed out, moving the barrel that is wobbly does not seem to shift the focus plane or alter sharpness at all. I am convinced that this lens has somewhat complex field curvature, but I should not be getting the border I am getting on the right at F8-F11 at infinity. Would have been a half decent picture too. :/