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Om-D focal length question with Rokinon 7.5mm

Discussion in 'Olympus Cameras' started by kevinaldo, Mar 23, 2013.

  1. kevinaldo

    kevinaldo Mu-43 Regular

    77
    Nov 30, 2012
    CA, USA
    Hey brothers and sisters, I currently bought the Rokinon 7.5mm, first time using manual focus and people told to change the focal length on IS setting to 8mm. If I change to another Len like 45mm or 12-50mm, do I have to change the focal length every time?

    Or is that a default focal length I can use?

    Thanks!
     
  2. fluberman

    fluberman Mu-43 Top Veteran

    502
    Sep 19, 2012
    Indonesia
    Alex
    The 12-50 and 45mm are native m43 lenses with electronic contact between the lens and the camera. You don't have to set the FL manually. You need to set the FL if you use adapted lenses or manual lenses without electronic contact, such as Samyang/Rokinon 7.5mm or other legacy manual lenses.
     
  3. Mikefellh

    Mikefellh Mu-43 Top Veteran

    939
    Jun 7, 2012
    Toronto, Canada
    Actually, the 7.5mm is also a native m4/3 lens since no adapter is required!
     
  4. Blastop

    Blastop Mu-43 Regular

    92
    Jun 20, 2011
    Sure, but with no electronics there's no way for the lens to self-identify to the camera, so Fluberman distinguishing it from "native m43 lenses with electronic contact" is still accurate.

    BTW, this is something I often forget to do - I often have an OM50 on my E-P2, and after a week without shooting anything I'll swap on the OM100 and start shooting pictures without remembering to change the focal length for the IS :doh:
     
  5. kevinaldo

    kevinaldo Mu-43 Regular

    77
    Nov 30, 2012
    CA, USA
    So what was actually happened if you didn't change?
     
  6. Blastop

    Blastop Mu-43 Regular

    92
    Jun 20, 2011
    The IS in an Olympus works by trying to hold the sensor in the original position from shutter opening until it closes. The amount of movement required varies slightly, on a given amount of shake, depending on the focal length. Depending on whether you set the IS on a materially longer or shorter focal length, the sensor will shift either too much or too little, resulting in reduced sharpness either way. Alternatively, if your hands were steady enough and the shutter speed was fast enough, you might never notice the difference.
     
  7. mussomusso

    mussomusso Mu-43 Regular

    48
    Nov 17, 2012
    Riva Del Garda
    Is it not perhaps worth switching IBIS off on the 7.5mm fishe-eye?

    Seems like it is of little use on a fishe-eye...
     
  8. homerusan

    homerusan Mu-43 Regular

    130
    Dec 25, 2012
    izmir, TURKEY
    So do you need to change the IS fc to 7.5mm or 15mm on samyang fisheye?
    Because i sometimes got blurry results even on screen with sy fisheye eith 1/60 s.
     
  9. fluberman

    fluberman Mu-43 Top Veteran

    502
    Sep 19, 2012
    Indonesia
    Alex
    Choose according the FOCAL LENGTH of the lens, not the equivalent focal length.

    From the manual, page 49.
    "Choose the value that most closely matches to the one that is printed on the lens."
     
  10. yehuda

    yehuda Mu-43 Veteran

    200
    Mar 14, 2013
    I once took an indoor video with the em5+rokinon 7.5mm lens and it was horribly wobbly and unbearable to watch.
    After changing the focal length manually videos came out stabilized and sharp.
    Makes a HUGE difference in video.
     
  11. Tee Why

    Tee Why New to Mu-43

    8
    Mar 28, 2013
    Probably not camera shake then. I'd consider MF issues or the IS messing things up b/ it has no idea what the focal length is.
    IIRC, I turn mine off b/c usually the shutter speed is fast enough in most situations. Plus you can just increase the ISO.