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Thread: Smarter material for ground glass shim?

  1. #1

    Join Date
    Oct 2021
    Posts
    4

    Smarter material for ground glass shim?

    I have a beat-up Crown Graphic that I removed the fresnel screen from. In addition to being well scratched, I also did not care for seeing the ridges when focusing through a loupe.

    My solution to shim the ground glass to the right depth was to cut thin strips of masking tape and layer them up. But I'm not getting uniform depth using this method, not to mention it's ugly.

    Is there a better way? I need approx. 1.1mm of shim to get to a total 5mm depth.

  2. #2

    Join Date
    Sep 1998
    Location
    Buford, GA
    Posts
    14,216

    Re: Smarter material for ground glass shim?

    If you use a proper focusing loupe and focus it on the grain of your gg the fresnel lines will no longer bother you.

  3. #3

    Join Date
    Aug 2004
    Location
    NYC
    Posts
    575

    Re: Smarter material for ground glass shim?

    get some thin brass from a hobby store. a pack of 5 assorted 4x5 sheets. you can cut the stuff with a regular pair of scissors.

    https://www.amazon.com/Goodson-Shim-...009RGYZO&psc=1

  4. #4

    Re: Smarter material for ground glass shim?

    I used paper cut into strips about a half inch long and stacked to the correct thickness. I measured with a micrometer to make sure that the total thickness was ok, stuck a dot of glue on each length, put the paper shims under where the clamps for the ground glass are with another dot of glue.
    Then I put the gg in place checking out the distance, let the glue dry and if the paper was black left it alone. If it is white…magic marker.
    Paper is very consistent in thickness and is a quick and easy fix for an incorrect gg position.

  5. #5
    Drew Wiley
    Join Date
    Sep 2008
    Location
    SF Bay area, CA
    Posts
    16,661

    Re: Smarter material for ground glass shim?

    Real shim stock is available from machinist and industrial supply companies like McMaster Carr. At the simpler level, I greatly prefer mylar shims to paper, since it doesn't absorb water and is quite dimensionally stable. I keep on hand some old leftover sheets of Cibachrome for this very purpose. It's great for shims, cutout masks for the ground-glass, enlarger carriers, etc.

  6. #6

    Join Date
    Jul 2008
    Posts
    3,246

    Re: Smarter material for ground glass shim?

    Cleared film base can work as GG shims, add as much layers as needed.

    Bernice

  7. #7

    Join Date
    Oct 2021
    Posts
    4

    Re: Smarter material for ground glass shim?

    Quote Originally Posted by Bob Salomon View Post
    If you use a proper focusing loupe and focus it on the grain of your gg the fresnel lines will no longer bother you.
    I have a 4x Rodenstock Aspärische Lupe. I still see outlines from the fresnel even with the loupe focus backed all the way out. Either way, the fresnel was heavily scratched when I acquired the camera.

  8. #8
    Eric Woodbury
    Join Date
    Dec 2003
    Posts
    1,568

    Re: Smarter material for ground glass shim?

    I used black paper. It was a heavy stock, probably 2 point. It can be sanded or peeled thinner if needed. Or it can be stacked; glued with rubber cement, if thicker is needed. A piece of film works for thinner shims.

  9. #9

    Join Date
    Nov 2017
    Posts
    277

    Re: Smarter material for ground glass shim?

    your numbers don't sound right. the original gg and fresnel should both be 1/16" (1.6mm). frame depth should be 2/16" (3.2mm). flipping the gg around so the ground surface is towards you should be all that's required to get the ground surface to the correct depth, 3/16" (4.8mm).

  10. #10

    Join Date
    Nov 2017
    Posts
    277

    Re: Smarter material for ground glass shim?

    Quote Originally Posted by Bob Salomon View Post
    If you use a proper focusing loupe and focus it on the grain of your gg the fresnel lines will no longer bother you.
    grain and fresnel lines are right against each other on a crown graphic.

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