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This topic comprises 2 pages: 1 2
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Author
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Topic: Align-O-Tron -- Problem Solving
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Tim Reed
Better Projection Pays
Posts: 5246
From: Northampton, PA
Registered: Sep 1999
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posted 08-22-2002 07:50 PM
quote:
The snood doesn't matter at all
The heck it doesn't. Try getting light out of a console with both the reflector mount and projector shifted to one side. I've always thought alignment kits should come with a means to find the center of the front of the lamphouse. Also, the front of the reflector should have the center defined as well, to ensure a true alignment. The mirrors in the plugs do this, if they're exactly perpendicular to the reflector optical axis (bumps and flash in the coatings can prevent this), but not all kits have mirrors. ------------------
Better Projection Pays!
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Rick Long
Jedi Master Film Handler
Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999
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posted 08-24-2002 11:21 PM
"Close dowser before servicing, snood" was on our Christie lamphouses. Always thought they were insulting me.As Gord says, we did visit a theatre with a light problem (ORC 4K). He found the front end of the lamphouse about a half-inch low, even tho the snood lined up fine with the Vic. 8. Correcting for optical height improved the light dramatically. In theory, if properly assembled, the lamphouse snood should be in alignment with everything else, but who is to say that the mirror assembly hasn't been disturbed in the past? I guess the three basic components of any projection system, (bulb, reflector and lens) all have to be in the same vertical as well as horizontal alignment if decent light is to be expected.
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Tim Reed
Better Projection Pays
Posts: 5246
From: Northampton, PA
Registered: Sep 1999
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posted 08-25-2002 01:22 AM
No, Gordon, it can and does matter. Only the extent depends on the size of the beam and snood. I'm not talking about just the projector and the snood - the entire optical train. You stated, unequivocally, that the snood didn't matter. When in fact it does, because it's in the path. It vignettes.I've gotten extremely high light readings after correcting these kinds of misalignment. If you've had lamphouse openings more than large enough, projectors lining up with the snood from the factory (automatically making a reflector-to-projector alignment correct), or reflectors slow enough, you've just been lucky. Otherwise, the center of the snood (opening) IS part of the optical train. If the opening didn't matter, it wouldn't be large at the rear and small at the front. Naturally, aligning the reflector with the projector will give an increase, that's like saying water is wet, but it's important that ALL the centers coincide - not just the front and the back elements. Quick test with a string from the outside of the reflector, all the way around, going to the respective corners of the aperture. If anything is in the way, the string will hit it.
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