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Oly 50-200 MKI AF behavior and accuracy

Discussion in 'Adapted Lenses' started by charleychen, Oct 3, 2012.

  1. charleychen

    charleychen Mu-43 Regular

    May 13, 2012
    New York
    I just purchased a used 50-200mm MKI with the MMF3 adapter. The image quality seems very nice.

    The AF behaves in a certain pattern:
    1) Quickly focus pass the AF spot (Can hear motor)
    2) Quickly focus pass the AF spot again in the other direction (Can hear motor)
    3) Goes into snail mode and slowly focuses until locked
    The whole process takes about 2 secs. Is this normal behavior? Is there any settings that I can change to speed up the AF? I am using it on the EM-5.

    After the focus locks, I would say 30% of the time the focus is off. When it does nail it, it's very sharp. Is this normal behavior? I think I can live with the AF speed, but the accuracy is a pain, as you have to refocus, sometimes a couple of times.

    Any thoughts and suggests on how I can improve the usability of the lens?

  2. Bhupinder2002

    Bhupinder2002 Mu-43 Hall of Famer Subscribing Member

    Unfortnately most of the 43 lenses will have AF issues on MFT bodies with only expecption of Zuiko 14-54 mm MarkII which is okay with AF .
  3. KBeezie

    KBeezie Mu-43 All-Pro

    Sep 15, 2012
    Grand Rapids, Mi
    Karl Blessing
    As I understand the E-System lenses are not designed to work as well on the micro-4/3 camera. The Pens for example use Contrast Detection AF, the lens designed for the E system uses a Phase Difference detection which isn't optimized for contrast AF.

    I don't even know which AF the OM-D uses as it just says "High Speed imager AF".

    So simply put, autofocus wise, that lens may not be a good fit with your specific camera using that adapter (as said above most of the 4/3 lens were not designed to work with contrast detection).

    edit: yea the OM-D system is also contrast-detection.
  4. charleychen

    charleychen Mu-43 Regular

    May 13, 2012
    New York
    Thanks for the responses. I still can't understand why CDAF with a phase detect lens would result in an inaccurate focus. My nikon CDAF, while slow, is very accurate. Oh well, will have to wait for the mFT phase detect camera. I really like the size of the 50-200. It's much smaller than my Sigma 100-300 f4.
  5. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    It is a pain. Regarding accuracy, have you tried switching to the small AF point?

    2 seconds sounds about normal.
  6. Promit

    Promit Mu-43 All-Pro

    Jun 6, 2011
    Baltimore, MD
    Promit Roy
    I've seen even the 14-54 II miss focus blatantly in ways that make no sense. It'll behave like it was pointed at a lens cap, give up, and lock into close focus.
  7. dhazeghi

    dhazeghi Mu-43 Hall of Famer

    Aug 6, 2010
    San Jose, CA
    Particularly odd considering that the 14-54II is supposed to be CDAF optimized, unlike the 50-200. Guess I shouldn't be too disappointed by the occasional odd miss with my 12-60 then.
  8. justin4192

    justin4192 Mu-43 Regular

    Dec 27, 2011
    Fairfax, VA, USA
    I sold my 50-200 SWD due to such inaccurate focusing. My experience seemed to be ~75% or so was missing focus, so your ~30% isn't that bad. I could deal with the speed, but not the inaccuracy, therefore I reluctantly sold the amazing lens. My 12-60 SWD works great though. It takes a second or so to focus, but seems to be 90+ percent accurate.
  9. Eirik

    Eirik Mu-43 Regular

    Aug 20, 2012
    Oslo, Norway
    I have used the 50-200/2.8-3.5 (Old non-SWD version) extensively on my OM-D, and in my experience it misses focus very rarely. The trick is to limit AF to just the "AF-box" in the middle, that seems to do the trick. That said, it does sometimes miss focus on full tele, this can be fixed by keeping it just off the 200mm stop on the zoom range. Also, the E-M5 really doesn't like to be used with the EC-20 teleconverter on the 50-200, with that, it tends to miss focus consistently.

    I have also used the 12-60mm f2.8-4 SWD quite a lot, that behaves similarly, the same goes for the old 14-54mm f2.8-3,5, which I have used briefly...
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