Christian Flemm Posted January 26, 2023 Share Posted January 26, 2023 Hi everyone - In the last six months I've had two 16mm release prints from my personal collection scanned in 2K. The picture and optical sound track files were returned separately, and in both cases have proven impossible to re-sync digitally (if I sync one shot perfectly, the next shot, or the scene two minutes previous, is suddenly out of sync by roughly a half second or more). I thought it was a fluke on the part of the lab in the first case, but now that it's happened a second time, I'm really not sure what the issue could be. Any ideas? While I cannot confirm how the optical track on the first print was digitized, due to an issue with the lab's scanner the optical track on the most recent print was recorded by hooking up a Zoom H4n audio recorder to a 16mm projector that was running the print. Any clue as to what the problem could be? Both prints were scanned at 24fps, with both optical tracks at a sample rate of 44.1 kHz. Best, Christian Link to comment Share on other sites More sharing options...
Perry Paolantonio Posted January 26, 2023 Share Posted January 26, 2023 (edited) The soundtrack needs to be scanned on the same machine, at the same time as the picture - OR - the device used to capture the sound needs to be exactly 24fps. A projector is not. It's the same as shooting film and recording double system sound: the camera and recorder both need a common, accurate, and consistent speed. This is achieved in cameras with a crystal controlled motor. In digital recorders, the clock inside the recorder ensures it's in sync. Projectors have no such mechanism (at least none I've ever used), so it's no wonder the sound is drifting from picture. Edited January 26, 2023 by Perry Paolantonio Link to comment Share on other sites More sharing options...
Mark Dunn Posted January 26, 2023 Share Posted January 26, 2023 I think the only way to do this without a rescan would be cutting up the sound into separate shots and, matching sync by eye, shot-by-shot. It would be very laborious. Only certain projectors were externally speed-controlled, when running separate magnetic sound in sync, but even then the requirement was that they ran frame-for-frame- the speed could still vary. +/- 0.3% is quoted for my Steenbeck. That's about 0.1fps, potentially a few seconds over your 2-minute scene. Link to comment Share on other sites More sharing options...
Premium Member Frank Wylie Posted January 26, 2023 Premium Member Share Posted January 26, 2023 Sounds like they used a mains-locked or otherwise non-sync transfer system for the soundtrack. If they charged you for this, I would ask them to "make it good"... Link to comment Share on other sites More sharing options...
Mark Dunn Posted January 27, 2023 Share Posted January 27, 2023 I agree- if you were promised an in-sync sound transfer, you should get one. Sounds (!) like the picture scan and sound transfer have been done separately. Link to comment Share on other sites More sharing options...
Christian Flemm Posted January 27, 2023 Author Share Posted January 27, 2023 1 hour ago, Mark Dunn said: I agree- if you were promised an in-sync sound transfer, you should get one. Sounds (!) like the picture scan and sound transfer have been done separately. They were done separately, owing to a problem with the scanner. I've a long relationship with this lab and we are all friends. Resyncing the sound won't be as laborious as you might think. Thanks again for all the advice! 1 Link to comment Share on other sites More sharing options...
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