Window glass infront of my projector?

Discussion in 'Archived Threads 2001-2004' started by Jens Raethel, Jul 25, 2001.

  1. Jens Raethel

    Jens Raethel Second Unit

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    If I place a window glass in front of my projector lens, would that make any changes to the picture shown on the screen?
    I would do this to get rid of the fan nois from both the projector and the ventilation in the projector cabinet.
    Take a look at my homepage, to get the idéa!
    Thanks,
    Jens
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    [Edited last by Jens Raethel on July 25, 2001 at 02:35 AM]
     
  2. Leo Kerr

    Leo Kerr Screenwriter

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    Okay, here are the problems with window glass.
    Conventional window (soda) glass is not uniformly clear. It does bias slightly toward the green. In the long run, however, this is a minimal color shift. "Boro-silicate" glass may be less "harmful" to the color; I'm not sure.
    Most window glass, unless specifically specified as being "float-glass," is not really flat, having faint ripples in it. These ripples can and will cause focus and geometry distortions to the projected image.
    Uncoated glass can also kill your contrast ratio by adding multiple reflections from the air-glass interfaces. The glass itself will "emit" light and soften both the image and the contrast. Getting said glass coated is probably not a cheap proposition.
    Said glass also adds two more surfaces that would need to be cleaned on a regular basis.
    Now, on to the other sides of the coin.
    Most of these problems are probably minimal (The ever favorite "your milage may vary..." The most serious of the above is the one about the contrast ratio.
    An alternative to glassing in the box would perhaps be to cut a small hole in the front of the box from which the lens would protrude. Further isolation could be achieved by wrapping into that hole heavy black felt or velvet.
    Additional caveots:
    Said hole and wrap would also likely block infrared remote commands.
    Projectors need ventalation; don't wrap them up too tightly!
    Leo Kerr
    [email protected]
     
  3. Deane Johnson

    Deane Johnson Supporting Actor

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    I haven't tried it, but I wonder if Plexiglass would work. That's what we use instead of glass in framing black and white pictures where we don't want any kind of distortion or color shift.
    Deane
     
  4. TedD

    TedD Supporting Actor

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    Plexiglass "G" is water clear and will not distort the image. It can be cut with a saw. I have used it for years for this purpose. Note: only the "G" flavor of Plexiglass is suitable, not Lexan, or any other flavors of Plexiglass.
    The only issue is that it can be easily scratched. However there are Plexiglass polishes available from the dealers who sell Plexiglass to handle that problem.
    Ted
    [Edited last by TedD on July 25, 2001 at 08:42 AM]
     
  5. Steve Schick

    Steve Schick Stunt Coordinator

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  6. Parker Clack

    Parker Clack Schizophrenic Man
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    Jens:
    Another thing that I have seen is putting nothing in front of the lens of the projector. Just put a board up across the opening that you have now with a hole cut out of the board for the lens of the projector to shine through. Some people have taken the rings that are used for spot lights in your ceiling to put in the hole that is cut out to give it a cleaner look. That way the only item that that is visible is the hole in the wall and this cuts way down on the noise of the projector. You would want to make sure that the box that you have the projector setting in now is well ventilated too so as not to over heat the projector.
    Parker
     

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