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Thread: Equivalent focal lenght

  1. #1

    Join Date
    Jun 2000
    Posts
    21

    Equivalent focal lenght

    Could anyone tell me what the equivalent focal lenght of a 90mm and 110mm (4x5) lens would be in 6x7cm or 35mm camera?

    Thank you.

  2. #2

    Join Date
    Mar 1998
    Posts
    1,987

    Equivalent focal lenght

    This has been covered many times and those threads are in the archives. The major debate is whether you should consider the angle of view covered by the diagonal across the various formats which is applicable in some circumstances, or the angle of view along the long side of the formats, which is applicable in other circumstances. Calumet Photo also has published a chart comparing these and many other formats.

  3. #3

    Join Date
    May 2001
    Posts
    29

    Equivalent focal lenght

    VERY roughly, I generally divide by three and subtract 10% to go from 4x5 to 35mm. Thus a 90 would equal about a 27mm and a 110 would equal about a 37mm.

    Most manufacturers double 35mm focal lengths to get 6x7 equivalents (thus, in the above example, 55mm and 75mm).

    As Ellis points out though, you can't do direct or exact comparisons across formats that have different aspect ratios.

    ....................

  4. #4

    Join Date
    May 2001
    Posts
    29

    Equivalent focal lenght

    'Course, you gotta subtract the 10%, meaning that "37mm" above should read 33 or 34mm, and "75mm" should read 66 or 68mm.... oops.

    ............

  5. #5

    Join Date
    Sep 1999
    Posts
    454

    Equivalent focal lenght

    Multiply by focal length by 0.3 for 35mm, by 0.6 for 6x7.

  6. #6

    Join Date
    Dec 2000
    Location
    Tonopah, Nevada, USA
    Posts
    5,204

    Equivalent focal lenght

    Your 90 will seem very much like a 65mm in 6X7, and a 28mm in 35. The 110 will seem like a 75 in 6X7 and a 35-40 in 35.
    He is no fool who gives what he cannot keep..to gain that which he cannot lose. Jim Elliot, 1949

    http://tonopahpictures.0catch.com

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