I bought a 2nd hand 16-45. At first since I had to swap mount rings from my k-5 to my k-7, I assumed that there was something wrong with my mount or that it was not parallel to the sensor plane. I then tried a bunch of other lenses and none exhibited the sharpness issues on the right edge that this 16-45 is showing. I loosened the mount very slightly and tried taking some pictures with some pressure one either side to see if shimming would have any effect and it did nothing to improve quality. When I point the lens at a zeiss star chart the out of focus donut looks like it might be shifting very slightly in the center. I should have tested the edges though.... but I don't believe in charts at close distance tells the whole story of how a lens might perform. I believe in real world results and to my eyes, I definitely have a problem. I attached a crop of the extreme edge with the left and right side. I finally tried the classic take one picture, rotate the camera and shoot upside down trick. Couldn't be clearer than day. This is at f10. At f8, the right edge is almost unusably soft. It goes from being pretty sharp entirely through the left to falling off in sharpness from the center to the right.
I had a chance to test this lens and when I did, I did not try distant objects, which is something I will do in the future. The street and building shots didn't look as bad, but looking back at images I took with my k-5 and this lens, it had issues on that body as well, so I can rule that out. I contacted the seller and he suggested that I just throw it up on e-bay and make a profit over the relatively low price I paid for it. I may do that, but in a lot of ways I don't feel honest or comfortable doing that. Someone less discerning would likely never mind or notice. Someone that routinely prints over 20" wide would be somewhat understandably upset. I've had this lens for a week. I find it discouraging that the seller didn't offer for me to just send it back to them. It is what I would do, and probably is the right thing to do.
There are a lot of sample variations on this particular lens, and selling it and buying another used is going to be like playing russian roulette I'm afraid. I'm really at a loss of what I should do. My 12-24 is in need of repairs and both my kit lenses, the 18-55 and 28-80 are showing some pretty serious decentering these days which is why I bought this 16-45 in the first place to give me a usable walk around zoom again. What would you all do in this situation? Now I have a non-working k-5 and a k-7 with dust under the sensor's AA filter and no wide to normal lenses. Kind of hard to do landscapes with just telephotos. I'm tempted to just buy a plastic mount 18-55 off keh. They used to be like 50 and now they are 80 or so. Grrrrr. I'm also tempted to just send this lens off to CRIS, but I am not confident they will fix it and worry they will just return it as in spec. It still is cheaper than a new 16-45 to have it repaired, but then I would have invested over 400 and for that amount I likely could just buy a used 17-70 which is probably even sharper at the wide end. I swore off zooms, but then my M28mm 3.5 quit snapping its aperture blades and I really missed having wide angles. I thought the 16-45 would be a good fit for a lot of what I shoot. Where it is sharp it is really nice and the left side of the frame is pretty sharp right up to the edges. That is the kind of lovely performance I was expecting, but instead just disappointment and frustration.
And yeah, sorry if I'm venting a bit. Its a beautiful day. I want to go take some pictures and not have to worry about image quality or come home like I did the other night and have to throw away most of my shots because they were just unusable. Maybe I'm just too picky? When the one side is exhibiting half the resolution as the other edge that's pretty noticable to me and would show right up in a large print. Especially when the rest of the frame is so sharp. I can live with uniform uneveness towards the edges. I'm sure I'm not the only one that would feel this way. I have pretty high standards of image quality, which is what initially attracted me to this lens. What to do....