Optical Film Soundtracks vs Magnetic Tape Recording

I’m thinking that this counts as a “general question” rather than one for Cafe Society because it’s a technical question. But if I’m wrong, and I need to redirect it, please let me know. That being said, my question is as follows:

I’ve known for years that in the early days of radio, many programs were distributed by way of transcription disk, and that if an actor blew a line in the middle of the transcription, they had to start all over again with a new disk.

I’ve also known that Bing Crosby was one of the initial investors in the development magnetic tape recorder, which would allow him to tape his shows at his leisure, easily edit out and re-record mistakes, and give him more time for golf. With the advent of tape recording, the transcription disk bit the dust.

But, it just occurred to me that there had been another possibility for a good 20 years before Ampex became a household word. Movies had been using optical sound since the late 20s, and while it definitely didn’t have the best sound fidelity in its early days, by the time “The Wizard of Oz” was made in 1939, the technology had advanced
sufficiently enough for them to lay down multitrack soundtracks and mix them down to just the right sound balance.

So, my question is, why didn’t radio producers (and others) use optical recordings as a method of distributing shows?


There really wouldn’t have been a point. An optical track needs to be printed on film and then the film needs to be processed in all sorts of nifty chemicals, and then you need a bright light and optical sensors to play it back. This makes perfect sense if you’re already printing a movie, since you’re going to be doing all of that anyway. But for an audio recording, physical and magnetic methods were a lot easier and cheaper.

Thanks. This sort of makes sense, and yet, in a way it confuses me more, because it implies that every time they recorded a new track for a movie, they had to process the film before they could hear the playback, and dubbing would be a total nightmare.

Now I’m wondering how the movie studios managed to do all that they did at all before the advent of magnetic tape.

interesting topic-those old optical soundtracks were played back via a device called a “selenophone”. It was a selenium photocell, whose resistance would vary according to the amount of light passing through the track. What a horrible systems to work with! I’m quite sute that most old movie prints got converted to magnetic sound tracks pretty quickly. In any event, I’ve noticed that the old movie sountracks are loaded with noise-60 cycle “hum”, pops, and hissing-one copy of the 1941 “MALTESE FALCON” was almost uintelligible. Can these be cleaned up?

Dubbing was done by filming the scene without sound. Then projecting it in a studio while the actor, or whatever, doing the sound watched and synchronized the sound with the action. It took practice, but then so does editing magnetic tape.