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Olympus 12-40 f2.8

Discussion in 'Native Lenses' started by thepiecesfit, Aug 28, 2016.

  1. thepiecesfit

    thepiecesfit New to Mu-43

    7
    Mar 8, 2016
    Having a weird issue sometimes where images seem to be decentered in focus. What I mean is that either the right side or the left side of the frame are sharp. Has anyone experienced this before? Even at apertures like F5.6

    I'm also finding that if I bump the zoom ring after locking focus the image will be completely out of focus. I haven't experienced this on other camera's from Canon for example. Is this just a thing? For example on my Canon body I can zoom in focus and zoom out and still be sharp, on my EM10 II this is not the case.

    Any feedback and thoughts on these issues? I purchased the lens refurbished from Olympus.
     
    Last edited: Aug 28, 2016
  2. wjiang

    wjiang Mu-43 Hall of Famer

    I haven't had a noticeably decentred lens before... but yours might be. Try a brick wall test with all the lines lined up straight and orthogonal.

    As far as focus change on zoom - that's pretty normal for most modern non-video lenses, they are usually not par focal. The only lens that I've had which seems even remotely close to par focal is the Panasonic 45-175, which is a pretty video oriented lens judging by the fact it has a power zoom too.
     
  3. Carbonman

    Carbonman Mu-43 All-Pro

    Jul 10, 2014
    Vancouver BC
    Graham
    With film cameras it used to be an important point of differentiation between varifocal and zoom lenses. Now the word 'zoom' is used much more generically.
     
  4. RAH

    RAH Mu-43 Veteran

    269
    Dec 1, 2013
    New Hampshire
    Rich
    I also shoot Canon (80D). I don't think I have any lenses for it that don't require refocusing after changing the focal length (zoom in or out). As wjiang says, that's the way most modern lenses work.
     
  5. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    I always heard the distinction being between "varifocal" and "parfocal" with both being a subset of "zoom" lenses.
     
  6. thepiecesfit

    thepiecesfit New to Mu-43

    7
    Mar 8, 2016
    That's interesting to hear my 17-40L and 28-70L both allow me to do this on my 5d3. As long as the DOF accommodates it i can zoom in i can zoom out after focusing, no change in sharpness. I never looked at the technical details as to why that was.
     
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