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Vivitar 135mm f/2.8 focus problem

Discussion in 'Adapted Lenses' started by Asenath Waite, Aug 16, 2015.

  1. Asenath Waite

    Asenath Waite Mu-43 Regular

    34
    Jun 7, 2015
    It won't focus past about 15 ft. Is it more likely to be a problem with the lens or the adapter (Fotga MD-M43)?
     
  2. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    Do you mean it cannot reach infinity, or it cannot focus closer than 15 ft?
     
  3. Asenath Waite

    Asenath Waite Mu-43 Regular

    34
    Jun 7, 2015
    It can't focus farther than about 15ft, and can't reach infinity.
     
  4. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    The adapter is too thick, it needs to be machined to remove some thickness.
     
  5. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    Doing some quick math the difference between 15ft and infinity is 4mm of extra length for a 135mm f2.8 lens, to be out by 4mm is scarily bad as far as tolerances go.

    Do you have another adapter or lens to test?
     
  6. Asenath Waite

    Asenath Waite Mu-43 Regular

    34
    Jun 7, 2015
    I don't have another adapter, and the only other MD mount lens I have is the Sima SF. It's hard to tell how well it focuses because of the soft focus effect, but I think the focus gets even softer before it reaches infinity. Is there any way to make sure the adapter is the problem, short of buying a new one?
     
  7. Asenath Waite

    Asenath Waite Mu-43 Regular

    34
    Jun 7, 2015
    Ok. Thank you for your help!
     
  8. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    Measure it with a caliper, it should be 24.25mm flange to flange (Minolta MD is 43.5mm flange focal distance, m4/3 is 19.25mm).

    I would be really surprised if it were out by that much though, the lens may have an adjustment which has taken a knock or something like that... The lenses most likely to show problems with an adapter are shorter focal lengths, wide angle lenses etc. Even a tiny amount with a wide angle can result in a huge focus shift.
     
    • Agree Agree x 1
  9. tjdean01

    tjdean01 Mu-43 Top Veteran

    842
    Feb 20, 2013
    Wrong adapter for that lens possibly?
     
  10. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Hmm, that's very surprising. Typically adapters are designed to allow a lens to focus beyond infinity to avoid just this problem...
     
    • Agree Agree x 1
  11. eteless

    eteless Mu-43 All-Pro

    Jun 20, 2014
    I'm guessing they measured from the wrong flange, IIRC the Minolta MD mount has a stepped flange on the bayonet. If they measured on the wrong step for the adapter I can imagine a very precise error being made.