Classic Optical Sound Recording

This is a 1943 film production explaining how optical sound was recorded for film. The audio was very low quality as you can see but was an effective way of getting the job done at the time. To learn more about the history of sound recording, visit en.wikipedia.org/wiki/History_....
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[@BarnacleButtock]

Even more amazing to consider all those hand painted graphic aids, frame by frame...

[@titmouse-distribution]

For those wondering what the song at the end of the video (which starts at 9:04) is, it is "Danse Macabre" by Camille Saint-Saëns.

[@kdegru]

Thanks for posting this rare film. This subject has fascinated me since grammar school where I formed an immediate love for the Bell & howell 16mm classroom projector we used to show sound film in class.

[@tadonplane8265]

We had both B&H auto threaders and RCA Victor machines that were hand threaded when I was in middle school AV club. When I learned that sound waves were actually photographed on the film and played back with an exciter lamp and photocell, I was blown away! In high school we had a full auditorium with a projection booth and in it was a 16mm RCA Porto-Arc projector. The transport and film gates were like the classroom machines but the separate lamp house contained a carbon arc lamp. In the base of the integrated stand it stood on was the transformer for the arc lamp and it resembled an arc welder. I took to running it quickly because I already knew how to hand thread an RCA. I got really good as a reliable projectionist and have many fond memories running movies for the whole school while watching that machine put on a beautiful show.

[@Dillinify]

It's surprising that an optical sound recorder in the vein of a reel-to-reel tape deck was never mass-produced.

[@td3993]

Magnetic tape can be easily erased and recorded over. A mercury compound coated film was produced which ran under a stylus that was wide perpendicular to film movement, but narrow in cross-section, with a broad V shape with an angle of, say, 100 degrees. This stylus was impressed upon the film surface in a perpendicular manner, and etched away the mercury compound to leave a wider or narrower opening of light depending on the pressure it imposed due to the magnetic transducer driving it from an amplifier. The result could be immediately played back, but could not be recorded over.

[@polymetric2614]

You'd have to do it in complete darkness, and then develop it. If magnetic tape hadn't come along, that might have happened. But my guess is that the amount of time between this invention (late 1920s) and the introduction of modern tape (~1945) was not long enough for it to be developed into a mass-produced product.

[@RayPointerChannel]

Actually it was. But for secret uses. Phone conversations by President FDR were optically recorded.

[@RyanSchweitzer77]

@@td3993Are you referring to the Philips-Miller audio film recording system introduced in the late 1930s? What you've described sounds a lot like how that format worked.

[@stuartmarks8844]

The music at the end was so damn cool. Ethereal I guess....always loved that sound from old media. And this has to be the most fascinating and interesting video on KZbin. ThAnX!!

[@Mercurius73]

Camille Saint-Saëns - Danse macabre

[@stuartmarks8844]

@@Mercurius73 right on......thx ......Donato!!

[@polymetric2614]

This is really cool. Wish they'd explained the variable area recorder, though

[@NickMoore]

Awesome video, I've been playing with the idea of making an audio film recording DIY style and this video had some interesting info that I didn't think about earlier.

[@td3993]

This is a very good demonstration, but sadly a very poor example of the quality of optical soundtracks. They can sound quite good. 16mm film has a limit of 6 or 7 KC, but 35mm can go up to 12 KC, and various "noiseless" soundtracks were developed that blackened out the unused part of the track for quiet passages. Both variable area and variable density soundtrack can sound quite good. However, variable density is highly vulnerable to non-linear response of the emulsion, as well as over or under exposure.

[@td3993]

@Domen Gregorčič this is likely a poor quality 16mm dupe. 16mm optical soundtrack has a frequency limit of 6 or 7 KC, no matter what era. Throw in poor quality duplication, and you have worse sound quality, particularly when duplicating variable density. I have seen and heard 1930s and 1940s 35mm films (with a max frequency of 12KC) with excellent sound quality, and I own 16mm films from the 30s and 40s that sound pretty darn good, better than this. I assure you that with all the advancements of the 50s and 60s, they were fully capable of producing excellent results in the 1940s if good equipment and technique were used.

[@moldyoldie7888]

@@td3993 16mm films may be capable of 6kHz or so, but when I was in Jr. High school in the late 50's, we ran 16mm prints of the Bell Telephone Science films made by Frank Capra. On the B&H projectors, they sounded worse than a telephone, no hIgh frequencies at all. Looking back, I wish we had projectors like the Kodak Pageants that had sound track focusing adjustments. They can make a huge difference in the top end.

[@td3993]

@@moldyoldie7888 Part of that is also amplifier design. My 1941 Victor Animatophone model 40, however, with its wide depth of field sound head, facilitated by a slit iris between the cylinder and circular lenses, has rather crisp sound reproduction. S still comes out as SH because of the space limitations of 16mm film, but my films, the better ones that were printed using optimal processes, sound far more detailed than what you hear in this video.

[@td3993]

@@moldyoldie7888 Here is a better example of its performance capabilities: instagram.com/tv/CAaMey-gUSc/?igshid=197i9u5zpdm9d

[@moldyoldie7888]

@@td3993 Toot-Toot's sound is pretty good. Back in the late 50's, The Bell Telephone series didn't sound anywhere that good, no sibilants at all. I still say it was bad soundtrack focusing, for whatever reason. I'd like to think B&H knew how to design sufficiently good amps. They managed to keep motor hash out of the audio! I have heard an inexpensive Kodak Pageant with a series heater tube amp that sounds very good. You want to talk about limitations of Kodak Pageant projectors with solid state amps? That's for another time.

[@M1GarandMan3005]

Would this have been the way that Jim McDonald would have recorded that puma sound effect back in 1951-52? That sound is still being used by television and video games to this day.

[@rubenmelias3073]

very good material Sir. Greeting from Argentina.

[@lizichell2]

very wonderful and informative.

[@masterandservant8021]

9:05 "Danse Macabre" Camille Sant-Saëns.

[@ericpham8205]

air pressure make a better pick up than magnetic? because to create pressure hacking to the internal recorder is harder than magnetic with wire which can be interfered by magnetic field of emf

[@jotape1960]

Something is wrong with the variable density area audio section samples of this video. There wasn't/isn't/won't be any reason to the noticeable audible distortion of those parts we can get hear here.

[@user-xs6vl7gr9w]

Did that 'ribbon light valve' later moved inside the motion picture film camera as the technology advanced? There are some 'circumstantial evidences' but no direct proof.

[@royjf10]

I have one question: How does the sound playback smoothly when the film is constantly freezing in place for the duration of each frame?

[@RichardBreivogel]

because it's also recorded with the film moving like that

[@royjf10]

@@RichardBreivogel Excellent observation.

[@junes_gloom]

As an alternative explanation, the sound is probably offset from the frame being shown; outside of the film gate, the film moves at a constant speed (in turn converted to the start-stop motion by loops of slack); this allows for smooth recording and playback.

[@har234908234]

@@junes_gloom 20 frames

[@scotpens]

The soundtrack is actually about 1 second (24 frames) ahead of the picture. The film is threaded in the projector with loops before and after it enters the film gate, where it's pulled down frame-by-frame by the claw engaging the sprocket holes. When the film passes over the photocell that reads the optical soundtrack, it's moving at a constant smooth speed. It's easier to understand if you look at a tutorial video showing how an old classroom 16mm projector works.

[@Aniketbabar]

Whats the photographic film made up of? I find it very fascinating

[@TangoSixFive]

Directly from Wikipedia, "Photographic film is a strip or sheet of transparent plastic film base coated on one side with a gelatin emulsion containing microscopically small light-sensitive silver halide crystals."

[@sammerritt730]

I believe it’s usually high contrast fine grain black and white film

[@scotpens]

Before 1950, the film base was highly flammable and chemically unstable cellulose nitrate. Later came cellulose acetate -- so-called "safety film" -- which is much more stable but will still start to decompose after a few decades if not stored under proper conditions. The emulsion (the light-sensitive coating that forms the image) contains silver salts that turn dark when exposed to light.

[@luckyroomhd6334]

film projector