sync issues between tape footage

arie wrote on 10/23/2003, 11:17 PM
I shoot bands with two camaras. Both are decent cameras (JVC 820 & 2000U), but sometimes I notice that the footage will get out of sync by 4 to 6 frames. It's easy enough to fix since I'm cutting back and forth anyway, but it's annoying.

I don't know if that's to be expected when shooting with two different cams, or if it's important that I use high quality miniDV tape. Does anyone have any suggestions? Maybe pro tapes, or better equipement?

Thanks!

Comments

Spot|DSE wrote on 10/23/2003, 11:42 PM
It's the clocks in the cams that creates this problem. Doesn't matter if you have good tape or not, that's not relevant to sync. If it's digital, either all the ones and zeros are there or they're not. If not, no image, no sound which shows up as a glitch, not sync. Canopus used to have an ini file repair for the 820, don't know about the 2000U though. An EPM might pop in on this one...
SonyEPM wrote on 10/24/2003, 9:00 AM
If you aren't dropping frames during capture (worth checking), there should be ZERO sync drift. We have not tested with these particular cameras so its hard to say for sure what's happening.
arie wrote on 10/24/2003, 9:06 AM
So, the quality of tape doesn't have anything to do with sync? I'm still thinking analogue.

By "clocks", do you mean the clocks that tell the cam to record x number of samples to the tape?
farss wrote on 10/24/2003, 9:17 AM
Cameras use quartz clocks to lock to which are pretty good however over a period of an hour or so I'd imagine that although the A/V in each camera will always be in sync relative to each other there will be some drift.

The only way around this is to have a sync connection between them or better still a sync pulse generator. I seem to recall also seeing a back box that does a local sync gen. You fit one to each camera but before the shoot you temporarily hook them together and they adjust all the clocks to run at exactly the same frequency. Other solutions are RF links but that doesn't appeal to me.

Now I remember how the black box works. You need one less black box than you have cameras. The one without becomes the master and you line all the other black boxes up so that they run in sync with the master camera.

The black box will also tell you how far out two cameras are.
John_Cline wrote on 10/24/2003, 9:42 AM
In order to ensure absolute sync between multiple cameras, you must genlock them together. No consumer cameras have this capability, a few industrial cameras do and all professional cameras have it.

Otherwise, you're just going to have to live with it, it's the nature of the beast.

John