Is it possible to reverse optical sound reproduction to...

Post by **thebrowniecameraguy** » Sun Jan 16, 2005 3:02 am

record instead?

Jordan

Post by **Herb Montes** » Sun Jan 16, 2005 3:35 am

If you mean having an optical sound projector record an optical track? No. You need a device specifically made for making optical tracks like the recording head inside certain models of the Auricon camera. Film labs would have an optical recording camera for that purpose.

Post by **FILM-THURSO** » Sun Jan 16, 2005 9:45 pm

ACTUALLY- Technically YES YOU CAN! BUT you would need raw film to expose to the light signal. It is very easy to make an 'optical' sound and you can even do it in stereo. The track method would be Variable Density type although it may inherit charactoristics of bi-lateral tracks.
Try this!- Disconect the the speakers from your stereo system and attach a single screw-in 3.5v torch bulb fitting to each speaker wire. Start your playback with the volume turned right down, then bring it up slowly. As the sound plays into the light bulb it will flicker according to how mow sound volume and pitch the light receives. All you have to do is focus the light into a narrow horizontal slit beam onto fresh un-exposed film to record a sound. The results would be a little crude but it is possible providing you can place the soundtrack fairly precisely on the film. A shutterring system would refine the sound quality and make it more coherant.
A variable density soundtrack is read on the basis of how much light hits the solar cell which is the reverse of what you see when playing sound into a light bulb. Optical principles are the same as speakers and microphones- you can play sound back on a microphone. Try plugging a mic into the headphone socket on you minidisc player.

Post by **portosuper8** » Mon Jan 17, 2005 5:17 pm

Is this the lamp tou're talking about?

http://www.snipebrook.dyndns.org/ShowPr ... PartNo=605

Post by **portosuper8** » Mon Jan 17, 2005 5:20 pm

I also assume you would only get a single track with this method, it might be posible to make stereo too, but it would need 2 lamps and some other method to control the both lights, right? As anyone tried this with some sucess?

Post by **FILM-THURSO** » Mon Jan 17, 2005 7:05 pm

Read it again, I said a torch bulb fitting to EACH speaker wire. This would give stereo signals.

The lights only need to be focused into a sharp beam. The amount of 'sound' reaching the lamp causes it to flicker accordingly. i.e, instead of the electric current coverting to sound vibrations in speakers, it becomes light variations instead. I haven't built a rig to record but then it does require some precision engineered parts. As such, light being photographable, the system will work.
If you are really clever with the patience of a saint, you could make an electro magnetic micro shutter to feed the sound into whilst the lamp stays the same brightness. This is normal method of recording variable density. If you can build one, and they are very simple electronics, then you'll be well on your way. Either sytem acheives the results though.

Post by **fritzcarraldo** » Tue Jan 18, 2005 5:40 am

Has anyone here in the forum had a sucessfull result with a similar method?

It would be very interesting for us to exchange experience in this subject, it might sound crazy to explore such ways of creating sound, but it's also very amusing, returning to the past can be very interesting, even in technology matters.

I'll try to get something out of it

Regards,

Post by **studiocarter** » Tue Jan 18, 2005 2:19 pm

http://www.archive.org/movies/details-d ... onid=01150

This old movie shows clearly how optical sound, mostly variable density, but also variable area, works in graphic form. I've downloaded many of these movies and made two DVDs of them. Hey, I was an art teacher don'tchaknow.

Michael Carter

Post by **FILM-THURSO** » Tue Jan 18, 2005 6:29 pm

I sure do agree, old technology is well worth toying with. It sometimes opens up new avenues of thought and inventiveness by looking at old ways with new eyes.
I've been thinking that the diafram (hmm, spelling?) of a low impedance microphne could be adapted to create a shutter if used as a speaker instead. Alas no time to go into it now though.

Post by **fritzcarraldo** » Tue Jan 18, 2005 8:34 pm

It might not be easy to build such a system, it involves microscopic precision, do you think that with a simple system we could achieve satisfatory results?

A system like the one in that little movie might be hard to make.

But not impossible of course,

regards

Post by **FILM-THURSO** » Wed Jan 19, 2005 6:19 pm

The thought with the mic diaphram certainly needs precision. My first thought on optical sound was when Kodak stopped their sound films. I recon you could fit a pigmy bulb in the camera where where the sound head is and it's wires could be connected directly to the bulb. The film would need to be completely shielded from the light except for a hair-line slit on the film edge for the sound recording. I guess 1/10th of a millimetre would be enough to get a decent dialogue track at 24fps on super 8. Of course as I said earlier, it might be a little crude in quality givin the lack of scientific precision. Dialogue is generally the only sound that needs to be filmed in sync unless there is a close-up or medium shot of an exact action. The optical track could be re-recorded with a pulse afterwards for mixing onto mag tracks in the final print.