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Lens size

Discussion in 'Native Lenses' started by nseika, Dec 21, 2010.

  1. nseika

    nseika Mu-43 Veteran

    260
    Nov 22, 2010
    Jakarta, Indonesia
    Lois
    From the internet, there is this two premises
    - Minimum size for front lens element is focal length / max aperture
    - Smaller sensor system such as m4/3 could have smaller lens design than full frame

    How does these two premises fit each others ? Same fatness but less volume ?

    Thanks for the answer. Just being curious :)
     
  2. Hikari

    Hikari Mu-43 All-Pro

    Nov 26, 2010
    Not really. You also need to take field of view and acceptable level of vignetting into the equations. Wide-angle lenses will always have a front element larger than the f-number would suggest.

    Optics to a certain point is a geometric problem. Given an equal angle of coverage, angle of view, and design, an m4/3 lens will be smaller. But, like most generalizations, that can be taken so far.

    Both length and diameter can be reduced to a point.

    Then there are other considerations. Physically, a 4x5 135mm lens is smaller than a 35mm 135mm lens. That is just because the way the cameras are made--a 4x5 does not need a helical focus mechanism nor does the lens construction have anything to do with lens-to-image plane distance (4x5 cameras have bellows).

    A few more thoughts. A lens can be shorter than the focal length would suggest--that is what a "telephoto" is--or longer, a reverse telephoto. You do not need to change the lens to sensor distance to focus, you can do that by changing focal length--that is what an IF (internal focus) lens is.
     
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