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Thread: Calumet 45n film plane/ground glass distance

  1. #1

    Calumet 45n film plane/ground glass distance

    Hello all. I am new here, I have lurked on the forum a few times in the past debating whether or not I should try out large format or just stick with 120. Today I finally acquired a 4x5 camera. A Calumet 45n box caught my eye at the local goodwill and the 8 dollar price tag persuaded me quickly to make the purchase.

    From what I can tell it seems to be in excellent condition. I do need to find a lens, lens board, and holders but with the 8 dollar price tag that won't be too much of an issue.

    The question I have is, after looking over everything I noticed that the ground glass seems to sit back a couple mm from where I think the film/film holder will actually sit. I do not have any holders to test and see if this is actually the case but I can't see how it wouldn't be. Also both the left and right side of the ground glass have a tiny(maybe 1mm) gap between the ground glass and the frame that it presses against. The top and bottom of the ground glass do not have this gap because they have the two metal pieces pressing them into place. Are both of the issues normal or is there something screwy going on? Sorry for my complete ignorance to all the large format. I've attached some pictures that hopefully help explain what I'm trying to get across. The red circle is to highlight the tiny gap on the sides of the ground glass.





    Thanks a bunch!

  2. #2

    Join Date
    Jul 2013
    Location
    Queensland, Australia
    Posts
    459

    Re: Calumet 45n film plane/ground glass distance

    Looks ok, but you can only tell with film holders and your first shot. The space is there to put a fresnel screen in front of the ground glass, which would make for easier focusing. I would suggest a certain amount of care when using the ground glass, as it is only supported on the ends it could easily fracture with weight put on the glass.

  3. #3

    Join Date
    Jan 2019
    Posts
    38

    Re: Calumet 45n film plane/ground glass distance

    There is a surface that the front face of a film holder will press against. The film in a holder actually sits about 5mm depth behind this plane (I think the ANSI standard for 4x5 is 4.8mm depth). IOW, the film sits much further back from the camera's fiducial surface than 35mm or 120 film sits relative to the film rails. Once you get a holder and examine it, how it works will become clearer. The GG position looks ok to me.

  4. #4

    Join Date
    Dec 2005
    Location
    Los Angeles, CA
    Posts
    4,686

    Re: Calumet 45n film plane/ground glass distance

    That’s the factory ground glass in the factory position.

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