Thread: Timecode sync with shutter
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11-09-2008, 09:48 PM
When the RED is synced to an external timecode, does the shutter open at the beginning of each frame? For example:
If you're running 24fps, then each frame lasts 1/24 of a second. So, if you're at timecode 01:00:00:01, then only 1/2 of the period of time at this frame is being exposed (given a shutter of 1/48). Does this exposure occur during the first half of this frame or the second half?
11-09-2008, 10:04 PM
As far as I'm aware there's no guarantee either way, and indeed I've seen shots of TC slates showing two different frame numbers - i.e. exposure is bridging two TC frames.
The only way to guarantee frame timing is to genlock.
11-09-2008, 10:07 PM
what do you mean by genlock? im using an external timecode generator - isn't that genlock?
11-10-2008, 01:23 PM
No. Genlock is a frame synchronisation system using (in HD video and for the RED ONE) "tri-level sync" and you'll need a specific generator for that. The Denecke SB-T is a rare example of a device that generates both a TC signal and tri-level sync.Originally Posted by swellison
11-10-2008, 01:34 PM
Noob question here but whats wrong with having the camera control the shutter and timing? Lets say you have the camera set to exactly 24.000fps. Frame XXX should be exactly XXX/24 seconds from frame 1 assuming the clock inside the camera is precise. Within the frame itself, you also have a shutter open and shutter close time and their delays which are specific to the limitations of the camera but I'm not sure if that data is really worth anything in post other than the generic shutter angle/duration value.
#6
Sync
11-10-2008, 06:10 PM
Yes, that is true, but the question is when does the external timecode generator change its value relative to when the camera captures its next frame?
Both can be running at exactly 23.976 fps, but one may be running a fraction later than the other (i.e they are in sync but are out of phase)
That's why running Genlock and Timecode into the camera is the best sync solution.
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