Movies made sound with a light bulb: Sound-on-film

Just like the movies in a theater!
Links 'n' stuff:
The Engineer Guy did a fantastic explainer on the mechanism of film projectors - much deeper than I went as I was focused mainly on sound. Check it out if you want to learn more!

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[OVMEBReed]

I worked for 9 years back in the 1970's as a sound engineer in a film laboratory. I spent many hours recording optical sound tracks for 16mm film. As for the nice dark track on the prints; the film processor had a thickened developer that was applied to just the sound track area by a narrow wheel. This allowed the sound track area to retain the silver and make a nice dark track. The same was done for reversal films. It was important to have the track be as sharp as possible. While recording the sound negative, some of the light would scatter into the unexposed area. The same would happen when the negative was printed onto the final print. We would run exposure tests to get this effect to cancel and leave a nice sharp sound image on the print. If it was wrong, noise and intermodulation distortion would result. Another point you many notice is that the slits narrow down during the quiet parts. A DC bias was placed on the galvanometer to keep it as narrow as possible for quiet sections and then open up for the louder parts. This greatly reduced the film grain noise during projection. Great video as usual.

[ADVISOR]

De-synchronizing your voice while pointing out the de-synchronization issues of old phonographs in conjunction with projectors, was a very nice touch.

[fellvarg]

Deeply appreciate the de-sync and drift moments in the said explanation moments! Always wonderful!

[wky]

As someone that almost always watches with closed captions on, I appreciate all the extra work that goes into adding those in. I especially liked the captions during rewind

[TheMan]

I love that you edited in all the little analogue cues into the video. Very well done.

[AshleyFoxo]

I feel Alec is going to slam a full IMAX projection system onto that table next month.

[rogermwilcox]

When I saw _Star Trek II: The Wrath of Khan_ in a movie theater in 1982, the projectionist missed one of the reel changes, and the movie ended (and the lights came up automatically) RIGHT in the middle of the heart-rending Spock-is-dying scene. Nothing kills the mood faster. Among the groans heard in the audience, someone called out, "Well, that's it. They ran out of money." (Referring to the film's producers.)

[MadScientist]

20:53 "Code unto others as you would have others code unto you." Programming parable soundly stood the test of time. :)

[tadonplane]

This made me nostalgic, I was in AV club in HS in the early 70s. We had a full auditorium with a projection booth, in it was a 16mm RCA Porto-Arc projector from the 50s. It was hand thread with a separate lamp house containing an arc lamp. A transformer that looked like an arc welder lived on the floor underneath the projection stand which powered the lamp. The projectionist had to learn to manually strike an arc to get it started. A clock mechanism fed the carbon rods together at the rate they burned away and a prism in the side of the lamp house projected an image of the arc onto a glass scale so that the projectionist could monitor the proper gap between the rods to ensure that the adjustable clock speed stayed correct.

If the clock speed was too slow the gap got wide and the picture went dim and turned yellow. If the speed was too fast the gap narrowed causing the picture to dim and turn blue. Properly adjusted the projector produced a really beautiful and very bright picture.

Each year our club would rent a feature film and charge admission to a “movie night” as a fundraiser. 16mm features came on two huge reels, we couldn’t show a feature without a break because we had one projector. Instead we watched for the cue marks and switched to a slide projector that contained an “intermission” slide. The tail out of these films was black so that the projectionist didn’t have to close the window on the film projector, the slide projected right over the blackout giving enough time to kill the arc. We also had a hand cranked rewinder that was much faster than the projector rewind.

I absolutely loved being a projectionist and got really good at it. That quirky sound of a 16mm optic soundtrack always brings back memories.

[_EVANERV_]

I love it when you are explaining the process of audio video syncing, the section is intentionally off-sync.

[daar]

I was a projectionist back in the early 90's and I remember when we got the Dolby Digital and DTS systems retrofitted to our projectors. We never got the Sony system though. The systems would instantly fail-over to the analog track if the digital signal experienced temporary corruption and switch back as soon as it got a good digital signal again. And yes, you could totally hear the difference when that happened but at least the audio didn't completely drop out if too much dust got on a section of digital squares. Also, try pointing an infrared remote at the light sensor behind the sound drum and press one of the buttons. You'll get a nice burst of digital noise pulses!

[xpehkto]

The another advantage of DTS's off-film approach that you didn't mention is an ability to switch soundtrack language without changing the film, which made it very useful in countries where movies could be released in different language versions.

[brianhawthorne]

I haven’t worked as a projectionist since 1984, but when that cue mark popped up, the countdown timer started in my head and I switched to the next projector with my hands just as you had that cut. You freaked me out! Thanks!

[jacobbaer]

Alec's Christmas present to me is the knowledge of where the word "footage" comes from

[cowboyfrankspersonalvideos]

Three stories:
In the late 1960s, I managed the AV department in my high school. I also ran Bell and Howell projectors, all though newer than yours. After a while, I got to where I could change reels and get the next reel going in under 15 seconds. If I could get two projectors, the audience could hardly tell when I switched, except for the fact I was standing in the middle of the classroom.

During the same period, my Father was a photographer for the Smithsonian Institution. One project he was involved in was to try to reproduce photographically some of Alexander Bell's original optical sound disk experiments. They were trying to retrieve the sound without doing any damage to the originals. I don't think that method worked, otherwise I think dad would have been more exited about it.

My dad was also into 8mm movies. He eventually obtained equipment to place the magnetic stripe along the edge between the sprocket holes and the edge of the film. There was a problem though. This made that side of the film thicker and caused the picture to be out of focus across the screen. Then someone came out with a device which would carve a groove under where the stripe would sit to flatten out the film. The device was basally just a slot with a tiny chisel which scraped the grove. The trademark name was "Cut-A-Rut" made by R.& D. Carnall & Company.

[kylejramstad]

I was the last trained projectionist at my theater in 2009. I remember we had Dolby and DTS on all our Christie projectors. Some reels came to us with discs and some did not. We used whatever sound the distributor gave us

[Fedorchik]

Your audio desync work is on point!
Brings back memories...

[CinemaSynesthesia]

Great video! A few things that might be of interest:
- Magnetic sound on film was more of a feature of cinema sound than you might have realised. When CinemaScope premiered in 1953, the wide image was only half of the selling point - the other was the 4 channel high fidelity soundtrack, which was achieved by putting 4 magnetic strips on the edges of the film.
This 4 channel layout (Left, Centre, Right, Surround) is what Dolby would emulate when they came up with their Dolby A encoding system utilising the optical soundtrack. (btw Stereo sound for cinema has always meant at least 4 channels, not 2 as is the case in the home).
The original Cinemascope was also a wider ratio (2.55:1) than what became the 'Scope standard (1.35:1) because it originally widened the image into the previous optical soundtrack area.

This "Mag-strip" was also utilised for the 70mm format, with 6 channels recorded onto the edges of the film. 70mm never had an optical soundtrack. Even once filming natively for 70mm became a rarity, big films were still often optically 'blown up' onto 70mm release prints pretty much purely to take advantage of the better soundtrack. 5.1 in the layout we know it today was already in cinemas since 1979 thanks to 6-track mag strip 70mm when Apocalypse Now premiered. Also, it sounds awesome.
- When doing traditional double-projector presentation, projectionists would often put some splicing tape on the edge of the film in the lead up to a reel change - the clacking sound the tape would make as it passed through the rollers / gate would serve as an audible warning that the reel was soon to end.
- SDDS utilised ATRAC encoding - the same compression format Sony had invented for the MiniDisc! Also, whilst it was 8 channels in its premiere format (which added two more channels behind the screen - the same as the original Todd AO 70mm Format), SDDS also had a standard 5.1 mode. For many years prints with all 3 soundtrack formats like the trailer you have were very common. What was less common was studios opting to upmix to the full 8 channel format. The advantage of having those extra 2 screen channels is again being utilised by Dolby Atmos.
- DTS didn't ever utilise higher capacity DVD Roms. However part of the original design of the system had allowed the timecode to also be used to trigger in-theatre effects. And from memory there was also provisions in the DTS bitstream itself to accomodate triggering other than the soundtrack. For this reason, DTS did get some limited use in special venue scenarios. It was also the only one of the 3 digital sound formats that had a 70mm version. Which was easy because the SMPTE timecode was just added to a 70mm print.

[mikenco]

I went into this video thinking it "wasn't for me", but the 40 minutes flew by and I found it all genuinely fascinating. Part of my job over two decades ago was splicing damaged film in a museum on these little displays. Everything in this video answered so many questions that I didn't know that I wanted answering! Thank you T-shirt-Tweed-jacket-guy! New sub!

[Darkmatterdwarf]

Another fact that is often overlooked in the states with DTS is that having the audio on a separate medium makes DUBs so much easier as you only need to swap the audiodisc so switch to another language. I think around this time cinamas started to tver alot more variations here in germany, making runs with original language, than one with dub and sometimes even a third language when there was a large group of potential customers of that language near a specific cinema.Noone would have dealt with that chaos in the older days.