The problem is that your detector is looking for changes in brightness, whereas you recorded sound amplitude as a _vertical_ displacement on the film. You could repeat your recording experiment by driving a white LED with the sound (so that it flickers on and off) as you wind the film past it. The film would record one straight line that fades in and out in brightness -- that would give a better signal to your detector, I'd think. That film trace from the oscilloscope is gorgeous, though!
The half modulated trace was supposed to give changes in light intensity but it wasn't modulated far enough. The problem with using a single LED is getting the exposure right, I have no idea if the film will come out entirely over or under exposed given the LED brightness and feed rate of the film. I do plan to revisit this setup again in the future.
Get an old double 8mm movie camera. Remove the lens and shutter, and shine your light through that. I think that's been done. Use black and white negative film. This will give you consistant speed.
You sir are amazing and awesome!! I am a weekend project afficionado myself: leyden jars, telescopes, camera obscura. But your vid is awesome and very entertaining.
Hey, thanks! Have you documented any of your projects? You should put them up for others to see and maybe they will get interested as well. Thanks for watching.
Can you show more in depth on how the modulator is made? I would think this system would be the easiest to make rather than bilateral variable area or variable density. Three isn't too much free information online unless you're a SMPTE member or something. Are there any good books on this topic?
I never really found anything on it. I used an AM modulator that gave me a unilateral area trace (it may be damaged) because it more closely resembles the original technology. Variable density probably would work a lot better and would be a lot easier to implement (throw an LED across a stereo's output.
Nick Moore How would you focus an LED to the film? There's an old film that shows the making of variable density using a "light valve" or magnetic ribbons. I don't know where or how to get one of those today. The best for my solution would be dual bilateral variable area tracks but all I can find online about that is some diagram drawings on some light and mirrors shining on the film. Not very helpful.
If you put the LED behind a slit (maybe with a little diffuser) you could use the same wind-the-film-by-hand method that I did. I'm not sure how the exposure should be calculated though, (which is probably why spatial modulation was used instead of density). For bilateral modulation you could feed your audio signal into an AM modulator with an extremely high carrier frequency then display the output on a scope with no sweep. The dot will expand and contract turning the audio signal into a bilaterally modulated line.
you need positive and negative hi contrast, or high and low filled-in hills, not empty line hills that don't vary in intensity. Those guys back in the days made it their life to get this stuff right. we are usually laid back , but this stuff is easier said than done. back to eating some pie and the drawing board.
I had tried to do a single sided modulated wave but it did't play back any better. Playing back the single trace is kind of like a zero-crossing detection and gave the most voice like results. If I ever tried again I would make a lot of changes.
You've probably done more research on the topic since trying to record sound optically on film, but here's an old video detailing how optical sound recording and reproduction was done in the movie industry. ua-cam.com/video/OjKQNykc_04/v-deo.html
The problem is that your detector is looking for changes in brightness, whereas you recorded sound amplitude as a _vertical_ displacement on the film. You could repeat your recording experiment by driving a white LED with the sound (so that it flickers on and off) as you wind the film past it. The film would record one straight line that fades in and out in brightness -- that would give a better signal to your detector, I'd think.
That film trace from the oscilloscope is gorgeous, though!
This is it
He recorded variable area, while his detector is looking for variable density sound
And not quite variable area either, since it's just the squiggle
Recording sound on to optical has been around since 1914.
Also playing back in the dark would probably help, as that will remove any light source that could potentially interfere.
So cool! Thanks for doing this. I always wondered how film optical audio worked.
I'd love to see more of this.
The half modulated trace was supposed to give changes in light intensity but it wasn't modulated far enough. The problem with using a single LED is getting the exposure right, I have no idea if the film will come out entirely over or under exposed given the LED brightness and feed rate of the film. I do plan to revisit this setup again in the future.
The results are amazing ! This is really cool experiment ! Sound like old wax cylinder dictation machine.
Get an old double 8mm movie camera. Remove the lens and shutter, and shine your light through that. I think that's been done. Use black and white negative film. This will give you consistant speed.
You sir are amazing and awesome!! I am a weekend project afficionado myself: leyden jars, telescopes, camera obscura. But your vid is awesome and very entertaining.
Hey, thanks! Have you documented any of your projects? You should put them up for others to see and maybe they will get interested as well. Thanks for watching.
Thank you! I completely forgot that, I use film as an IR passing filter in one of my other videos >_
So this is how really old telephone announcements worked
I think they used a glass disc or tube so it would last longer.
Genius.
awesome!
The playback quality is pretty rough but I was still happy with the result considering the kludge it took to make it work.
Thanks for the video.
Amazing!
my guess with the halogen light would be that halogen lamps have lots of infrared light as well which passes exposed film
Can you show more in depth on how the modulator is made? I would think this system would be the easiest to make rather than bilateral variable area or variable density. Three isn't too much free information online unless you're a SMPTE member or something. Are there any good books on this topic?
I never really found anything on it. I used an AM modulator that gave me a unilateral area trace (it may be damaged) because it more closely resembles the original technology. Variable density probably would work a lot better and would be a lot easier to implement (throw an LED across a stereo's output.
Nick Moore How would you focus an LED to the film? There's an old film that shows the making of variable density using a "light valve" or magnetic ribbons. I don't know where or how to get one of those today. The best for my solution would be dual bilateral variable area tracks but all I can find online about that is some diagram drawings on some light and mirrors shining on the film. Not very helpful.
If you put the LED behind a slit (maybe with a little diffuser) you could use the same wind-the-film-by-hand method that I did. I'm not sure how the exposure should be calculated though, (which is probably why spatial modulation was used instead of density).
For bilateral modulation you could feed your audio signal into an AM modulator with an extremely high carrier frequency then display the output on a scope with no sweep. The dot will expand and contract turning the audio signal into a bilaterally modulated line.
you need positive and negative hi contrast, or high and low filled-in hills, not empty line hills that don't vary in intensity. Those guys back in the days made it their life to get this stuff right. we are usually laid back , but this stuff is easier said than done. back to eating some pie and the drawing board.
I had tried to do a single sided modulated wave but it did't play back any better. Playing back the single trace is kind of like a zero-crossing detection and gave the most voice like results. If I ever tried again I would make a lot of changes.
If you have more doubt take a view on 35 mm flim movie projector sound head..
You've probably done more research on the topic since trying to record sound optically on film, but here's an old video detailing how optical sound recording and reproduction was done in the movie industry. ua-cam.com/video/OjKQNykc_04/v-deo.html
Awesome, thanks!