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This topic comprises 2 pages: 1 2
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Author
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Topic: Analog sound question
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Charles Greenlee
Jedi Master Film Handler
Posts: 801
From: Savannah, Ga, U.S.
Registered: Jun 2006
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posted 07-02-2006 03:34 AM
Yeah, but as someone mentioned fantasound. Surround has been around since 1940. Fantasound had 4 optical tracks on film. 3 descreet audio, and 1 control. From that the togad, driven from the control track, was able to, ehh, kinda matrix out 3 more channels. Actually, all it did was pan the same 3 tracks to alternate speakers. But you could have a car drive by on the right, hear it approach on the center, pass to the right stage, and then via panning, pass to the right surround. I enjoyed reading the technical atricles on fantasound at the widescreen museum. Doly NR allowed the optical tracks to become small enough that 2 would fit in the same space and sound....acceptable. The matrixing is mostly for the optical, because there was 4 and later 6 channel magenetic before optical was matrixed to 5 channels.
Sum? Is that how a 3-stereo setup derives it's center channel?
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Stephen Furley
Film God
Posts: 3059
From: Coulsdon, Croydon, England
Registered: May 2002
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posted 07-02-2006 06:11 AM
Michael, I'm not sure when matrix became available; your date sounds about right for a commercial product, but, very often, commercial products are based in ideas from long before. I don't know in this case. However, Dolby stereo could still have been introduced several years before it was. Even then, there was not a sudden rush by the cinemas to install it; many remaind mono for years. Quite a few installed Dolby 364/E2 mono systems, even after stereo prints were introduced. The Phoenix, East Finchley (later removed) and Screen 1 at the Odeon, Watford come to mind. Presumably this was done to avoid the cost of a stereo installation.
Dolby stereo didn't really offer anything much in technical terms which wasn't available before; what it did do was to offer it at lower cost and complexity than previous systems, which relied on either separate interlocked tracks, or mag striped prints*. Even though the prints were cheap, the cost to the cinema of a stereo installation was still considerable, as it had been for all previous systems, including Perspecta.
* The exception being the two channel Blumlein tracks, and the similar '50s Photostereo system, but the lack of a centre channel in these systems was s serious problem in a theatre auditorium.
Several of the early optical sound systems allocated a much greater film area to the sound; one used roughly half the width for each. The best-known of these systems was probably the 42mm Tri-ergon. For anybody who hasn't seen it, take a normal 35mm silent film, add an extra 7mm of film outside the perforations on one edge, print a wide VD track on this extra film area. It's a pity such a system wasn't adopted; the extra space available would have been useful a few years later when stereo experiments started.
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Charles Greenlee
Jedi Master Film Handler
Posts: 801
From: Savannah, Ga, U.S.
Registered: Jun 2006
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posted 07-03-2006 04:03 AM
Hmm, I haden't notice the drift, but it makes sense. I mean, you can buy a semiconductor here, and buy supposedly the exact same thing somewhere else, and because it's simply from a different batch, it may be off. Good point. Either way, I'm writeing my ideas dow, so I can remember them, and it makes it easier when you can go back a reread. Sometimes you find stuff you didn't before. Well, I guess drop me a line if you're interested in helping, or at least interested in listening. Maybe you can find something I haven't yet, or counter something I have.
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Charles Greenlee
Jedi Master Film Handler
Posts: 801
From: Savannah, Ga, U.S.
Registered: Jun 2006
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posted 07-04-2006 03:06 AM
Ha-ha, yeah. We've had someone burn one of our lenses (remember kiddies, if the lamp is lit, the motor should be running. And limit the amount of time the lens is exposed to the unfiltered light), so we pulled a flat lens of the same stats from another projector that wasn't using the flat (was a scope feature) and put in there. Well we did it by simply unscrewing the lens from its collar, rather than fuss with pulling the collar and lens out of the turret, and having to refocus and all when we put it back. So collar and lens from the recepiant house were already at a position of being in focus and aligned and all. It should be a simple matter of unscrewing the bad lens and screwing the good one on the collar. Ths should work since, on paper, the lenses were identical. Not! The image size was slightly larger, and the focus was off more than just a smidge. Evidently, even if the lenses have the same stats, there's a difference from lens to lens, even if unintentional.
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