Help evaluate my oly 12mm f2

Started Feb 16, 2014 | Discussions thread
Anders W Forum Pro • Posts: 21,468
Re: Help evaluate my oly 12mm f2

You should do the test Paul suggests. When you do, remember to switch to MF before you start shooting and be careful not to touch the focus ring when you turn the camera upside down for the second shot. It's important that the focus remains identical for the two shots.

But based on the evidence you already posted, I agree with eques that the left side looks a bit worse than the right (perhaps especially the upper left, but that may be because the objects in that part of the frame are more distant so that the ideal focus distance differs).

I've had similar problems with the 12. I tried three copies and all were a bit weaker in one or other part of the frame (not the same part on all three copies). I ended up keeping the third copy and solved the problem by shimming the lens slightly at the mount by means of aluminum tape. It's pretty much OK now.

Note that this lens has a bit of field curvature, which isn't unusual with WAs. When shooting landscapes or distant targets, I therefore prefer to set focus at a point about midway between center and the left or right edge. In essence, this mean that the lens will backfocus slightly in the center and front-focus slightly at the corners (but less so than would otherwise be the case). The loss in the center (where the lens is very good) is hardly visible but the edges/corners improve noticeably.

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