Originally posted by timo A common problem with the Z. Yes it is fixable - I don't know about this forum, but there have been threads on it on dpreview. It's a bit fiddly but with the right screwdriver easily done. Unfortunately I destroyed one of the screw heads, so having slightly over-adjusted mine I cannot easily redo it. I haven't got time now to type out the step-by-step but it's very simple. Do a search on DPR.
There are good directions at the pentax-lens-and-japanese-doll-site:
Zenitar 16mm f/2.8 Fisheye
(look under "Don't Panic")
A few things to note:
(0) If in doubt, consider returning it.
(1) Don't expect this lens to be sharp at f/2.8. If you get an acceptable result at f/4 and slower, you're done.
(2) The infinity marker will hit the index mark whether this lens is properly adjusted or not.
(3) Use the properly sized screwdriver and press firmly to seat the screwdriver in the screw slot
(4) There's a good chance you can get the focus ring loose even and make the adjustment if you can loosen only two out of three screws.