Checking ground glass/film holder tolerances

Discussion in 'Large Format Cameras and Accessories' started by sanking, Aug 20, 2004.

  1. sanking

    sanking Member

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    Can anyone point me to articles on the web or in print that describe practical techniques for testing ground glass/film plane tolerances. I am aware of an article on the subject that appeared in PhotoTechniques in 1999 but would like to know of any others that may be out there, perhaps in View Camera? or in on-line sites.

    Sandy King
     
  2. mark

    mark Member

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    There was one in VC, or shutterbug, maybe, that described using a tooth pick and a pencil. Pretty informative and it works well. I remember the techniques but not where the article appeared, sorry.
     
  3. Poco

    Poco Member

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    Sorry, no article, but FWIW this works for me: put a post-it pad inside the film holder and peel away sheets until a ruler lies flush across both it and the edge of the film holder. Then put the pad against the inside of the ground glass and see if the depth is the same. Not a perfect system, but pretty good.
     
  4. sanking

    sanking Member

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    Thanks, I believe that is the one in Photo Techniques.

    Sandy
     
  5. glbeas

    glbeas Member

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    I've done it using a steel rule from a carpenters square and a caliper with a depth feeler. laid the ruler across the seat area and the caliper against the rule and pushed the feeler down to contact the bed or the glass. It's best to check your filmholder with film in it naturally and careful not to scratch the GG with the feeler. Don't just check one spot but the center and four corners if at all possible.
     
  6. sanking

    sanking Member

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    Yes, ANSI specifications state that the T-dimension should be the same everwhere on the septum 1/4" outside of the film retaining lip.


    Sandy
     
  7. DrPhil

    DrPhil Member

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    Lambrecht and Woodhouse describe the toothpick method in their book "Way Beyond Monochrome"
     
  8. wfwhitaker

    wfwhitaker Member

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    Sandy,

    It's not clear to me what you're asking. Are you looking for a method to adjust the ground glass to match the film plane of a holder? Or are you asking how to determine what is a realistic tolerance? Or something else?...
     
  9. sanking

    sanking Member

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    Just looking for references to articles that may have been published on the subject. Don't need the how to or tolerances, just references to what others may have already published on the subject, either in print or on the web.

    Sandy
     
  10. wfwhitaker

    wfwhitaker Member

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    I think that falls under "something else". ;-)

    Good luck!
     
  11. cjarvis

    cjarvis Member

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    I think it falls under "potential bibliography".
     
  12. Mateo

    Mateo Subscriber

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    If this is true, Mr King would you be sure to keep us posted on when the book would be available. I'm sure I'd like to have a copy.
     
  13. sanking

    sanking Member

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    Well, that too but more importantly I am just trying to get an idea of the kinds of ideas that have been proposed. I am trying to write something on this but I don't want to reinvent the wheel if there is already a better wheel out there than the one I have in mind.


    Sandy
     
  14. JHannon

    JHannon Member

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    In Barry Thornton's book "The Edge of Darkness" (P41-48) he describes testing camera focus accuracy using a board with a series of 1cm spaced vertical lines drawn on it. The center line is marked and is the point of focus. Distance is 2 feet from the board and all cameras had full aperture.

    Upon developing the film he has several photos showing how far off the focus is for each camera tested. I thought it was an interesting test and I am going to try it. It does involve using rolls of film, developing and printing etc.

    I hope this helps.
    John