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Author Topic: Strange Port Glass Reflections Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-06-2005 07:06 PM                     I have noticed once in a while that we get a strange reflection on our screen. As the credits roll up, there is a dim but definitely noticeable mirror image rolling down. Also, if there are still words somewhere on the screen, that also gives a mirror image. It does not happen on all the screens and I am not sure that it happens with every movie. We are using optical glass in the ports. It seems somehow that the image is bouncing off the glass, back to the projector or lens, and back out again. Any ideas?  |  IP: Logged Peter Mork Expert Film Handler Posts: 181 From: Newton, MA, USA Registered: Jun 2002 posted 10-06-2005 07:17 PM                     You may have to pay attention to what's behind your screen. Those itty bitty holes in the surface let light through and create a dimmer version of the image on the wall behind the screen which is visible, especially from more direct viewing angles. Putting in black baffling, or just painting everything behind the screen flat black, is the cure for this.  |  IP: Logged Jesse Skeen Phenomenal Film Handler Posts: 1517 From: Sacramento, CA Registered: Aug 2000 posted 10-06-2005 08:29 PM                     It's usually the speakers behind the screen.  |  IP: Logged Brad Miller Administrator Posts: 17775 From: Plano, TX (36.2 miles NW of Rockwall) Registered: May 99 posted 10-06-2005 09:45 PM                     From your description, the image is hitting the port glass, bouncing back to the projector, and then something reflective on the front of your projector...usually the turret...is reflecting the image back. I've seen this in many Century projector installations, and frequently people have taken a black marker and inked out the entire silver portion of the turret to aleviate the problem.  |  IP: Logged Phillip Grace Expert Film Handler Posts: 164 From: ACMI. Melbourne. Australia. Registered: Mar 2004 posted 10-06-2005 10:16 PM                     The same thing can happen with Victoria 5's in front of large ports. The makers plate on the motor is an effective reflector. The ghost image always tracks a bright object in a dark scene. Same cure. Paint it black.  |  IP: Logged Rick Long Jr Expert Film Handler Posts: 211 From: Toronto, Canada Registered: Jul 2000 posted 10-06-2005 10:32 PM                     I've seen this many times with many different projectors, but never when the glass is angled. Except for one theatre, where the theatre had the ports installed with the top edge instead of the bottom toward the auditorium against our wishes - his reasoning was that less dust could settle on the outside. Problem was that in one cinema it turned out that the projection angle was almost identical to the glass tilt. This phenomenon of the inverted image was very noticeable.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 10-07-2005 06:45 AM                     Rick hit the nail on the head...odds are, your port glass is not angled or not angled opposite to the projector. That is, if your projector is pointing straight or down to the screen, the port should be angled such that any reflected image points to the ground (with coated glass it may only be a blue or puple image but that should be hitting the ground, not the back wall of the booth or worse, the theatre on the other side. If you have double ports (something I think is essential to keep noise down), then they should be angled in opposite directions so they don't bounce off each other. Ideally, any reflection on the theatre side glass should hit the inside of the port and not get back into the booth.  |  IP: Logged Richard May Phenomenal Film Handler Posts: 1057 From: Floral Park, NY USA Registered: Aug 2004 posted 10-09-2005 07:44 PM                     That sounds like the answer Steve and Rick. The projectors are not angled at all. They shoot straight on. The glass is also not angled. Next time I am there, I am going to tilt the glass and see if it changes. Thanks guys.  |  IP: Logged

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