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Author Topic: Port Hole Question Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 05-31-2002 10:05 PM                     that is why glass is coated with an anti reflective coating it works both ways  |  IP: Logged Frank Angel Film God Posts: 5305 From: Brooklyn NY USA Registered: Dec 1999 posted 06-03-2002 01:22 AM                        Hmmm...but if the double reflection was caused by the thickness of the glass, wouldn't we get the same double image with the 35mm & 16mm projectors? The double image only happened with the slide projectors when they were placed close to the window. My understanding is that the need for angling the windows is to prevent parallel glass surfaces, but that is only hearsay (and I have no idea where I heard this). I never heard about reflections into other theatres; that's something we single booth operators never have to worry about.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 06-03-2002 05:56 AM                     When the projector was close to the port the image on it was smaller so the double image effect was in fact representing a larger percentage of the total image Angled glass was to minimize the internal reflection within the glass itself where it starts to act like a prism  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 06-03-2002 06:33 AM                     Try and experiment using a flashlight.... Stand in front of your glass and point the flashlight (with it on) at the glass and stand right behind the flashlight (with your eyes at flashlight level). See the reflection nice and bright? Now angle the flashlight (since angling the port glass will be more difficult at this point)...notice it isn't so bad? If it was coated glass, about all you would see is a faint violet reflection at that point. Therefore, the key is coated, angled glass. Steve ------------------ "Old projectionists never die, they just changeover!"  |  IP: Logged Bill Enos Film God Posts: 2081 From: Richmond, Virginia, USA Registered: Apr 2000 posted 06-04-2002 12:47 AM                     In response to an earler post about Brenographs. We still have our 1928 Brenograph Model F7 in use every night at the Byrd. We do our screen ads on it. The slides are two pieces of 8 x 9.5 ince window glass with an ink jet printed transparency sandwiched between and taped around the edges. Since the two projectors are about 4 feet apart vertically and about 12 feet off center of the screen the transparencies are rotated considerably from horizontal and are not interchangable between the two machines. We still have 10 of the original glass effects slides and the clockwork operated colorwheel. A 30 amp carbon arc thru a 4.5 aperture blows away 35 mm slide projectors in brightness. Is anybody else still using one of these monsters every day?  |  IP: Logged Fred Georges Master Film Handler Posts: 257 From: Lombard, IL, USA Registered: Jun 2000 posted 06-04-2002 12:22 PM                     The Fox in Atlanta uses their ancient Brenagraph anytime they have a film show. They show ads & singalong slides with the Pipe Organ.  |  IP: Logged

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