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Topic: Projectionist worked to the bone

John Pytlak
Film God

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

posted 10-16-2000 12:24 PM

Jon Bartow said: "The Analog sound track is 19 1/2 frames ahead of the image".

Sorry, that is NOT correct! Standard SMPTE 40 states: "The audio record on the film shall be displaced from the center of the corresponding picture by a distance of 21 frames +/- 1/2 frame in the direction of film travel during normal projection."

So if a frame has an image of a gunshot, the corresponding "bang" on the analog track is 21 frames ahead of that frame. Because sound takes time to travel from the screen speakers to the audience (about 50 feet in 1/24 second), most projectors are designed to have 20 frames between the picture aperture and analog sound pickup to have the sound be "in sync" 50 feet from the screen. Your thread-up of 19 1/2 frames would put the sound in sync 75 feet from the screen.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

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Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 10-16-2000 01:52 PM

Sorry!! John, you of course are correct. I sit corrected.
Apparently I did not remember accurately.

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Tom Kroening
Expert Film Handler

Posts: 214
From: Janesville, WI USA
Registered: Oct 1999

posted 10-16-2000 02:29 PM

Yeah, I never really thought about the sync depending on the size of the auditorium and the distance the speakers are to the audiance til the other day. I had the port window open to listen to the sound level while i had the monitor slightly on still. ECHO!! oops. I assume there's also some sort of delay for the surrounds depending on where they are? Also, does that delay change for each surround speaker? (like the front surrounds less of a delay and the ones further back more of a delay?).

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Jon Bartow
Master Film Handler

Posts: 287
From: Massachusetts
Registered: Nov 1999

posted 10-16-2000 06:46 PM

Tom, most movie theaters have the same delay setting for all of the surround speakers. Unless the theater is a tunnel (very long and narrow) a single delay setting works fine. There are a couple of devices on the market for adding delay for the back of the auditorium (I don't remember for sure, but I think Smart makes one called an "afterburner")
If a "normal" sized movie theater tried to use different delay settings each speaker would be mere milliseconds apart. Not to mention that the current processors only have one delay setting. Also, one would have to have a different amp for every speaker.

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John Walsh
Film God

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

posted 10-16-2000 07:48 PM

I worked at a theater that had a 150 ft throw (28ft wide screen!) I tried to get people to thread the sound accordingly, but no one really cared.

A CP200 (with the optional accessary unit) can handle 3 seperate delays. Only place I ever saw it used was Radio City MH (they have three balconys.)

Long live the CP200!

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Randy Stankey
Film God

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

posted 10-16-2000 09:16 PM

At Mercyhurst the throw is 110 ft. The first couple of times I ran movies there I had to do a little experimenting to get the sound advance right.

(We used to call it "Chinese Disease" when the sound was out of sync. )

The boss would call me up on the phone and say that the lips don't match the words and I'd turn on the monitor and listen. It'd be right on. BUT... at the back of the auditorium there'd be a noticible diference.

Frank Prete
Film Handler

Posts: 55
From: Victoria, Australia
Registered: Sep 2000

posted 10-16-2000

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