ground glass for ULF

Discussion in 'Large Format' started by emile_de_leon|9, Oct 21, 2002.

  1. Hi all,
    Was thinking about replacing my older GG on my Korona 12x20,For
    hopefully more brightness. Is there a plexiglass substitute that
    might be lighter in weight and breakproof also.... who makes and
    sells this kind of thing? Or is glass the best way to go?
    Thanks.
     
  2. Emile,

    I recently replaced by 4x5 GG so have spent a bit of time looking around. You might find SRB in Luton (UK) might be able to help as they specialise in resin and plastic filters and will make things to order.

    www.srbfilm.co.uk

    I ended up buying a couple of sheets of 4x5 GG from Stephen Shuart.

    www.stephenshuart.com

    Good luck
     
  3. Short answer on the lexan/plexiglass: Run away!! I have a 14x17 with an
    acrylic ground glass, and it has possibly the worst hot spot problem I have
    ever encountered. I also have a sneaking suspicion that it flexes when i put
    the loupe on it to focus the camera. And believe me, the loupe is absolutely
    necessary with this glass. It is impossible to get a view of the full image area,
    not matter how I dance around under the darkcloth. It is maddening. I have
    ordered a replacement 'real' ground glass from Shuart. The other person I
    know who has the same acrylic ground glass has purchased a 16x20 fresnel
    from Edmund Scientific, which he then cut to fit the camera. He says this helps
    a great deal. Of course a great, though expensive, option would be to order a
    Boss Screen from Bromwell Marketing. The only problem is that it may take 3-
    6 months or longer to get the order fulfilled. Plus, there is the temperature
    sensitivity to worry about with Boss Screens. I have a traditional GG on my
    Korona 12x20, and I find it to be about the best compromise in terms of cost,
    availability, and brightness. As far as I am concerned , the only advantage to
    a plastic screen is its' breakproof nature, but this is far overshadowed by the
    difficulty in using it.

    Good luck!

    Clay
     
  4. After using a custom made Plastic "brightscreen" in the Original
    Polaroid 20x24 cameras for years, and hearing of a couple of
    ground glass breaks when shipping the new portable Wisner
    system, I did some looking around and found P-95 Plex. It is
    lightly diffused on one side, and if used without a fresnel the hot
    spot is awful. I replaced the New York Polaroid studios ground
    glass with a Plex and Fresnel sandwich, and ordered the same
    to install in my 14x17(I'm the other guy Clay mentioned) I LOVE
    THIS COMBINATION. You just NEED the fresnel.
    I was worried about deflection in heat and with loup pressure,
    but I doubt it will have any serious efffect. My only gripe is fine
    focusing with the fresnel in place, I'm going to make the fresnel
    removable to solve this. Good luck deciding, I'm real curious to
    hear what other folks have tried. I just never want to be stuck out
    somewhere with a 27LB camera, bleeding fingers, not able to
    shoot. : ) Tracy Storer
     
  5. In my zeal to praise the Plex/Fresnel combo I neglected to
    mention...the fresnel in this size from Edmund Optical is about
    $200.00. I would not want to use the Plex without the fresnel. If
    anyone wants to go this route, I can give you pointers on cutting
    the fresnel, I've cut three or four of them now for various big
    cameras. Best, Tracy
     
  6. I have a fresnel on my standard 12X20 GG which was supplied by Wisner with the camera and I think comes from Edmund Scientific. It is really quite bright and convenient to use, and the fastest lens in my current arsenal is f9. I'm very happy with the combo for everything from 210 to 750 in focal length (but then I'm not shooting a lot of church interiors...) You might ask Wisner what he supplies for his ULF cameras. I assume it's no trade secret. Another high end option for BEAUTIFUL bright ground glass in any size is Maxwell Precision Optics (404-244-0095), but be prepared to pay. And wait.

    Regards,

    Nathan
     
  7. Clay mentioned the real problem with plexiglass - it is less rigide than glass and flexes under loupe pressure. To have the desired rigidity you would need thick plexiglass which would give you the same weight as glass but also unpleasent optical effects due to its thickness.
     
  8. Thanks all for the info regarding the GG! I have yet to decide on this.Cheers!
     
  9. I have seen plexi ground glass on a camera made by scratching it with emery cloth. Worked OK for the 8x10 & 11x14 the guy had them on but not too even. I have stuck with the traditional glass because it works & is not expensive to have a few spares. I blow my own with a large commercial sandblaster. A bit more coarse than acid etched but nice & bright. Those who have purchased the one I have made like them. I always point out the sand/metal blasted glass is not as good for very fine detail as the acid etched glass is. It is a trade off now matter how you go. Brighter us usually a bit more coarse than dimmer. The glass doesn't flex & as some pointed out above this is a consideration, especially with larger cameras. Heat & cold will also play a part. A lot of plexi shatters easily in freezing weather. Temps of 10 below zero & more (farenheit) are death on some of them. Then trying to clean frozen breath of them tends to scratch the heck out of them as well.
    Glass still works well and if you can, get a few extra just in case yours gets broken.
     

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