Plastic "Ground Glass" Am I nuts?

Discussion in 'Camera Building, Repairs & Modification' started by Philip Taylor, Aug 4, 2006.

  1. Philip Taylor

    Philip Taylor Member

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    I'm starting to put together my ideas in preparation for a 4x5 monorail for field use. As part of this, I thought it may be better to use acrylic to cut down on weight however I've never seen anyone mention or do this. Is there any reason it wont work?

    Also, I forget right at the moment, is the film plane in the same position as the front (lens side) or back (viewing side) of the ground glass? - i.e. what surface needs to be in the same position?

    Thanks.
     
  2. Dave Parker

    Dave Parker Inactive

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    Your not crazy, people do it, the ground side of whatever you use needs to be tword the lens and the ground side is the same as the film plane. One thing to take into account, is the amount of weight savings in this size of camera is going to be virtually nothing, as a real ground screen in this size only weighs about 4oz and a plexi screen will weigh about 3oz. In the overall scope of things, 1 oz is nothing.

    Good luck....

    Dave Parker
    Satin Snow Ground Glass
     
  3. smieglitz

    smieglitz Subscriber

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    I recently replaced a broken ground glass screen of a homemade 8x10 box camera with a piece of 1/8" acrylic that is frosted on one side and smooth on the other. It worked fine and I did not notice any loss in brightness with it. I certainly will be replacing the GG of my 11x14 with the stuff at the first opportunity.

    Joe
     
  4. Roger Hicks

    Roger Hicks Member

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    Not nuts, no, but there is one small thing to watch out for. Plastic will flex far more than glass so don't press too hard in the middle of the screen with your loupe, or you'll be shifting the plane of focus. The bigger the format, the greater the risk, obviously.

    Cheers,

    Roger (www.rogerandfrances.com)
     
  5. Pragmatist

    Pragmatist Member

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    As Roger & Dave point out, there is no appreciable weight savings and the plastic is not optically stable. In some cameras, the fresnel (which is plastic) achieves part of its plane characteristics by the support of the GG it lies next to. There are also issued with focus grain definition, brightness, corner falloff, etcetera. Rather than plastic, look at one of the Satin Snow GG's, or bite the big-buck-bullet and think about a Beatty interscreen. Either choice will make you happy you did...
     
  6. tim atherton

    tim atherton Inactive

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    there are some weight savings for 8x10, but not really so much for 4x5 (it's also rather easier to smash an 8x10 gg...)

    plenty of info in a recent thread:

    http://www.apug.org/forums/showthread.php?t=29914

    (BTW - Maxwell screens are far superior to Beatty intenscreens. You might look at one of those rather than make your own plexi-GG?)
     
  7. Lachlan Young

    Lachlan Young Member

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    Has anyone ever put their head through a gg screen? :wink:

    Lachlan
     
  8. Roger Hicks

    Roger Hicks Member

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    No, but I've broken enough GGs -- from 6x9 cm to 11x14 inch over the years -- that the one reason I would consider Perspex or the like is that it's harder to break.

    Cheers,

    Roger
     
  9. jp80874

    jp80874 Subscriber

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    He is here isn't he? Gotta be nuts.

    John Powers
     
  10. jp80874

    jp80874 Subscriber

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    Philip is talking about a 4x5. That might be a challenging task.

    John Powers
     
  11. Roger Hicks

    Roger Hicks Member

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    Goooood point!

    Cheers,

    Polysporus O'Cohen
     
  12. David H. Bebbington

    David H. Bebbington Inactive

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    No, but I did hear once about an LF workshop where the participants were sleeping in bunk beds. With a particular couple of guys, guy A was sleeping in a lower bunk and placed his 4x5" field on the floor next to his bed, screen uppermost. Guy B, sleeping in the upper bunk, lept out of bed in the morning, full of motivation to go out and shoot 10 shots to beat Ansel Adams, and put his heel through guy A's GG, which formed an effective photographer trap, the various shards of glass around the central hole digging into his heel and preventing him from removing same. You could say that the moral of this story is - fit an acrylic screen if you don't want to be taken to A&E with an LF camera stuck on your foot. On the scale of things, this is considerably less embarrassing than a vacuum cleaner stuck to your **** (I speak only from hearsay evidence), but still an experience you might prefer to avoid.

    Regards,

    David
     
  13. Philip Taylor

    Philip Taylor Member

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    Well. I don't have a big head, so that's one reason for a plexiglass screen, number two is I'll be carrying the thing on trains, and knocking it around here and there, and number three is I'll be near Uni students who like to pinch nice ground glass.

    I think I'll give it a go.

    Thanks all for the reply's.