Olympus OM lenses on 4/3 bodys? Quick question

Discussion in 'Photography Beginners' Forum' started by KKJUN, May 16, 2010.

  1. KKJUN

    KKJUN TPF Noob!

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    Hi Folks,

    I'm looking and searching for a 50mm Olympus OM lens to use on my e520 for about 2 weeks. Now I have one question (I hope I can put it in an understandable way as I don't know the english terms for the stuff I need to describe):

    If I'm informed correctly, the crop factor of 4/3 bodies is about 2; would that mean that a 50mm OM lens on my e520 gives me a "real" focal length of 100mm? Do I have to multiply with two when attaching an OM lens to a 4/3 body?
     
  2. Dallmeyer

    Dallmeyer TPF Noob!

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    Yes. 4/3 is 2x crop factor. The lens remains 50mm focal length, but the field of view becomes like a 100mm.
     
  3. Dwig

    Dwig TPF Noob!

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    NO ! !

    The focal length does not change. It is a fixed property of the lens and can't be altered by simply mounting the lens on a different body.

    What changes is the field of view (FOV). FOV is a product of the combination of the focal length and the size of the image (film or sensor). The "crop factor" term refers to FOV and not focal length, and by modern convention involves comparison to 35mm full frame, though it does so rather inaccurately.

    The 2x crop factor associated with 4/3rd and m4/3 means that "any 50mm lens used on a 4/3rd format body will yield about the same FOV as any 100mm lens on a 35mm full frame body." Since 35mm film is almost never reproduced without some cropping the comparison is only approximate (error is about 5-10%). Also it compares the angular FOV on the image diagonal. The horizontal or vertical FOV comparisons will be different if the aspect ratios of the two formats differ as they do when comparing 4/3 with 35mm FF.
     
  4. KKJUN

    KKJUN TPF Noob!

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    Yeah, of course. By "real", I meant if the field of view I would get would be similar to a 100mm 4/3 lens on a 4/3 body. I did know that the focal length of the lens wouldn't change, sorry for being unclear.
     

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