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Topic: Masking Stops

Paul Rich
Film Handler

Posts: 56
From: Murfreesboro, TN, 37128
Registered: Nov 1999

posted 11-05-2001 03:33 PM

On two of our screens, the masking seems to stop in the wrong places. On one screen, the left side is back too far in flat and both seem to go too far back in scope.

On the other, the masking is too far back in flat on both sides.

I'm not familiar with how to adjust masking, and we'll get a tech to come out in a few years. Anyone have any tips?

-Paul

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 11-05-2001 05:27 PM

Before you go tinkering with the rigging, are you sure it's the masking and not the projector alignment? It has happened to me several times where somebody bumps into the console with something heavy and moves it a hair bit. Depending on your setup, a couple of milimeters of displacement of the console could end up being a couple of FEET of displacement of the picture.

That's not including the lens eccentricity and the aperture plate stops and junk like that. Have you tried opening the masking as far as it will go and projecting a picture (with test film) onto the screen to see if the projector is lined up the way it should be?

Elimanate all the easy things before going behind the screen and altering the settings of the masking gear. I have seen some people who have tinkered with things they shouldn't have and totally F***ed the rigging.

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John Walsh
Film God

Posts: 2490
From: Connecticut, USA, Earth, Milky Way
Registered: Oct 1999

posted 11-05-2001 10:58 PM

Really, listen to Randy. Years ago I did exactly what he said; In my case, someone had put in a "filed wrong" aperture they found in the junk pile (why some projectionists save worthless parts is beyond me!) and I thought the masking was wrong.

You need a test alignment film to verify the projector position first.

It depends on the masking motor type, but usually there are two adjustable levers inside the masking motor assembly. These levers are geared to the pulley/sprocket that operates the masking pull cord. As the motor operates, the levers move around until they press on a switch- which shuts off the motor. One lever sets where you want the motor (hence the masking) to stop for flat, the other for scope.

Unless you're sure of how to adjust it, I'd suggest you wait for a tech. Moving those levers only a few degrees can equal several feet of masking travel; perhaps farther than the masking track will allow. I've seen motors pulled up out of the floor because the masking was opened all the way, but the motor kept going. And masking track and rigging pulled down to the floor, too.

There are several different kinds of masking motors. There are newer ones with electronic controls that replace the old lever types.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 11-06-2001 09:56 AM

I agree that if the masking stops were set correctly in the first place, it's more likely that the projector was bumped, the lens mount shifted, or the wrong aperture is being used. Irregardless, ALWAYS use the SMPTE 35-PA (RP 40) Projector Alignment film to verify the projected image area:
SMPTE: Setting the Standards
Caring About Composition

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Cell: 716-781-4036 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com
Web site: http://www.kodak.com/go/motion

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