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Thread: Extension tubes confusion

  1. #1
    Member
    Join Date
    Dec 2003
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    Singapore, Singapore, Singapor
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    Thumbs up Extension tubes confusion

    Hi all,

    Would like some advice on whether the use of extension tubes affects the DOF of the macro lens at a given focal length?

    As already known that extension tubes causes light loss and a commensurate exposure compensation is necessary.

    eg. Tamron 90mm @f2.8 + extension tube may end up giving an exposure reading as if it were @f/4 or smaller for the same f2.8 aperture ring setting on the lens.

    So.... Given that the DOF of the same lens is XX cm at F/2.8 @ any pseudo focusing distance, will the actual DOF with extension tube attached follow the DOF of the actual aperture setting (ie. DOF @f/2.8 = XXcm) or the apparent aperture setting (ie. DOF @f/4 = more than XX cm)?

    Appreciate any kind souls that may offer a solution to my confusion.



    cheers
    Last edited by cphile; 2nd September 2005 at 10:42 PM.

  2. #2

    Default Re: Extension tubes confusion

    Hi,

    you may want to read this excellence article about extension tube

    http://www.oncloserinspection.com/Ph...es/extubes.htm

  3. #3
    Member
    Join Date
    Dec 2003
    Location
    Singapore, Singapore, Singapor
    Posts
    362

    Default Re: Extension tubes confusion

    a very informative link.... Thanks a million

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