[Jukebox-list] Movie Sound

[Ed Inman]

Variable density (and the later improved variable area) soundtracks, are basically analog tracks printed onto the film alongside the picture frames. They are projected by an "exciter lamp" inside a projector's "soundhead" onto a "solar cell" which is located just below the projection mechanism.  A typical classroom 16mm projector from the 70s is more or less a minature example of a full-sized 35mm theatrical projector. Both project 24 frames per second at sound speed with rotating shutters blocking out the light each time the "intermittant" advances a frame.

Analog soundtracks and projector heads have remained remarkably unchanged since the 30s except that most modern projectors have replaced exciter lamps with infrared LED's in order to play "cyan" color printed tracks which are cheaper to mass produce than the traditional B&W opaque silver tracks.

Virtually all new 35mm prints still contain these photographically printed analog tracks as a default system. Ironically, however, many films today also employ something of a modern-day incarnation of the old "Vitaphone" system to employ multi-channel improved digital soundtracks. Essentially a "time code" is now printed alongside the analog track to keep an "SDDS" disc (much like a regular music CD) in perfect sync with the picture. If the SDDS disc skips or has some timing problem (as we all know discs often do) the projector will then automatically default to the old fashioned analog track, and the audience will for the most part never know the difference.

Ed


-----Original Message-----
>From: Ron Rich <ronnnrich at yahoo.com>
>Sent: Dec 3, 2007 9:35 PM
>To: Ed Inman <edinman at earthlink.net>, Jukebox mailing list <jukebox-list at lists.netlojix.com>
>Subject: Re: [Jukebox-list]  Movie Sound
>
>Ed, 
>  Wasn't "Vitaphone" a news reel type short--or am I getting it mixed up with "Movie Tone"--or did Movie Tone use Vitaphone?
>  What are "variable density soundracks"--the sound on film process??
>  Ron Rich
>
>Ed Inman <edinman at earthlink.net> wrote:
>  I believe playing records in sync to produce a film's soundtrack was called the "Vitaphone" system and was largely phased out by the 30s when variable density soundtracks became common.
>Ed