OK you pedants - what is the *exact* size of a 35mm image?

Discussion in 'Digital Photography' started by Alan F Cross, Aug 3, 2003.

  1. Alan F Cross

    Alan F Cross Guest

    So the 10D has a "magnification ratio of lens focal length of 1.6
    compared with 35mm usage. Then a pedant comes along and says it's 1.58,
    another says it's 1.59.

    I know this is purely academic (if you're bored, quit now!), but what
    are the *exact* dimensions of a 35mm image? Most of us say it's 36mm x
    24mm, but perhaps this is only an approximation. Anyone accurately
    calculating a dSLR 'ratio' from its sensor size needs to know exactly
    what size a 35mm image should be.

    Now, no guessing, no assumptions, who can point me at an authority where
    the precise 35mm size is recorded?
    --
    Alan F Cross
     
    Alan F Cross, Aug 3, 2003
    #1
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  2. Alan F Cross <> writes:

    > I know this is purely academic (if you're bored, quit now!), but what
    > are the *exact* dimensions of a 35mm image? Most of us say it's 36mm x
    > 24mm, but perhaps this is only an approximation. Anyone accurately
    > calculating a dSLR 'ratio' from its sensor size needs to know exactly
    > what size a 35mm image should be.


    See the following ANSI standards:
    ANSI PH7.1-1971
    ANSI PH3.41-1972(R1991)
    ANSI PH3.43-1969
    ANSI Y15.1-1959

    See the following URLs:
    http://www.imagingspectrum.com/cgi-local/SoftCart.exe/canon_eos_1ds_digital_camera.html?E scstore
    http://digilander.libero.it/comolli/resol2.htm
    http://www.panoguide.com/technique/digitising.html
    http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005HBS
    http://www.earthboundlight.com/phototips/20021215.html


    (Watch for wrapping on that first one.)
    --
    Philip Stripling | email to the replyto address is presumed
    Legal Assistance on the Web | spam and read later. email to philip@
    http://www.PhilipStripling.com/ | my domain is read daily.
     
    Phil Stripling, Aug 3, 2003
    #2
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  3. Alan F Cross

    Jim Townsend Guest

    Alan F Cross wrote:

    > So the 10D has a "magnification ratio of lens focal length of 1.6
    > compared with 35mm usage. Then a pedant comes along and says it's 1.58,
    > another says it's 1.59.
    >
    > I know this is purely academic (if you're bored, quit now!), but what
    > are the *exact* dimensions of a 35mm image? Most of us say it's 36mm x
    > 24mm, but perhaps this is only an approximation. Anyone accurately
    > calculating a dSLR 'ratio' from its sensor size needs to know exactly
    > what size a 35mm image should be.
    >
    > Now, no guessing, no assumptions, who can point me at an authority where
    > the precise 35mm size is recorded?



    All I've read shows the 35mm frame is 36mm wide. The 10D sensor is 22.7mm
    wide.

    So 36 / 22.7 = 1.585903083

    1.6 is so much easier to work with :)
     
    Jim Townsend, Aug 3, 2003
    #3
  4. Alan F Cross

    Alan F Cross Guest

    In message <>, Phil Stripling
    <> writes
    >Alan F Cross <> writes:
    >
    >> I know this is purely academic (if you're bored, quit now!), but what
    >> are the *exact* dimensions of a 35mm image? Most of us say it's 36mm x
    >> 24mm, but perhaps this is only an approximation. Anyone accurately
    >> calculating a dSLR 'ratio' from its sensor size needs to know exactly
    >> what size a 35mm image should be.

    >
    >See the following ANSI standards:
    >ANSI PH7.1-1971
    >ANSI PH3.41-1972(R1991)
    >ANSI PH3.43-1969
    >ANSI Y15.1-1959
    >
    >See the following URLs:
    >http://www.imagingspectrum.com/cgi-local/SoftCart.exe/canon_eos_1ds_digi
    >tal_camera.html?E+scstore
    >http://digilander.libero.it/comolli/resol2.htm
    >http://www.panoguide.com/technique/digitising.html
    >http://www.photo.net/bboard/q-and-a-fetch-msg?msg_id=005HBS
    >http://www.earthboundlight.com/phototips/20021215.html
    >

    Interestingly, the first link above has the following statements in
    respect of the Canon 1Ds

    "an imaging area of 24 x 36mm, the same dimensions used by full-frame
    35mm SLRs"

    "Image size: 35.8 x 23.8mm (1.4 x 1 in)"

    By deduction 4064 sensors at 8.8um comes to 35.7632 mm

    I suspect there's rounding off in some of these figures, so the question
    remains. Is the 1Ds *exactly* the same as 35mm film, or is film
    *exactly* 36mm x 24mm?

    --
    Alan F Cross
     
    Alan F Cross, Aug 3, 2003
    #4
  5. (David J Taylor) writes:

    > I bet that 35mm film is exactly 36 x 24mm, but that most manufacturers
    > will make their image area slightly smaller to allow for subsequent
    > processing. In the case of professional cameras, perhaps not smaller at
    > all.


    The real nuisance is that manufacturers make their viewfinder image
    smaller than full frame, and photo processors typically print at less
    than full frame. You pretty much have to do your own darkroom work to
    get a full frame print.


    --
    http://home.teleport.com/~larryc
     
    Larry Caldwell, Aug 3, 2003
    #5
  6. Alan F Cross

    Guest

    In message <>,
    Jim Townsend <> wrote:

    >All I've read shows the 35mm frame is 36mm wide. The 10D sensor is 22.7mm
    >wide.
    >
    >So 36 / 22.7 = 1.585903083
    >
    >1.6 is so much easier to work with :)


    Most converters ignore 12 horizontal pixels, and 8 vertical pixels, so
    it may actually be closer to 1.6 with a 3072*2048 image (the sensor
    actually records 3084*2056).
    --

    <>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<>
    John P Sheehy <>
    ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>><
     
    , Aug 5, 2003
    #6
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