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

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.

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

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

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

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

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.)

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.

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!

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.

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

My pleasure!

28:49 - There's an episode of Columbo called "Make Me a Perfect Murder" in which you get to see this reel change technique done. Also, I have to say, it's crazy to me that people were able to figure out how to make this stuff work as well as it did so long ago. Not just the reel change technique. Everything. Every part of this just seems amazing.

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

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.

31:41 "And you probably recognize our old friend dual-bilateral variable-area! Later renamed Shrek ..."

80s kids like me who watched plenty of these in elementary school will have waves of nostalgia from this video! What amazes me is how clean and crisp the sound is from the film.

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!

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

I was a projectionist in 97-98 at a 10 theater house. One of the things not really detailed was how film was transported. Movies came on reels in canisters and a 2 hour movie used about 4-5 reels. They had to be spliced together and fed to the platter system and then broken back down after the film release had run its course. I was hoping to see some footage of how the multiple reels had to be daisy chained together as well as the trailers. One benefit of putting together was being able to do a “run down” on Thursday nights after hours before a typical Friday release. We had to make sure that there were no mistakes during the splicing to insure that a reel wasn’t offset by miscounting the sprocket holes during a splice. All in all this was very informative and it brought back some good memories. I really enjoy your channel and the topics you choose. All of the research you put into your topics, shows in the final product. Kudos.

I don't know how you manage to make super engaging videos like this. My guess is by default many people would find that 3 minute film demonstration at 18:00 boring, but I was so goddamn happy you showed that material