"tri-level" sync on multi-cam EFP video shoots

[Larry Kaltenbach]

Assuming no double-sound in this question, just multiple video cameras each recording sound...

I've been doing ENG/EFP sound for 23 years and haven't "genlocked" a multi-camera shoot in over a decade. I recently picked up the Wolf Seeberg "24P For Sound And Video Assist", which was published in 2005, and am reading about all sorts of "green flashes" and missing frames in video if one doesn't "tri-level sync" all 24P cameras on a multi- camera shoot with either a Ambient or Denecke sync box.

Can anyone tell me if I should REALLY be using such devices and practices on all multi-camera ENG/EFP shoots, and if so, why? What career-ending things will occur? I haven't received a single phone call ever regarding sync problems, missing video frames, or anything similar. Have I just gotten lucky, at someone else's expense?

Thanks,

Larry K.

[RPSharman]

Larry, there have been lots of threads about this.  You can search some key words and find lots of information.

My short opinion is that I have never run tri-level either, and have never had a problem.  With the RED (and perhaps other file-based systems), TC is dropped in as a marker, so continuous sync has no affect on sound issues or EXT/INT clock issues.  Genlock might matter for some multiple camera high-tech/3D shoots, but in those cases it'll be a DIT that handles it.

Robert

[Philip Perkins]

I'm about 50/50 on this issue now, after years of insisting that cameras be genlocked if they are taking external TC.  On the job yesterday, (Pana 3700s), the DIT and the rental house spec'ed that we use both the Trilevel and the TC outs of the Lockits.  We were shooting an event that lasted nearly 2 hours--a good test for any TC system.  Not long ago I worked on a multicam shoot w/ the same cameras where all the shooters, ACs and DITs were from LA and worked together as a team on episodics: they specified that I NOT hook up the Trilevel output of the Lockits--TC only.  I haven't heard of a greenflash in a long time now--but I don't know for sure if that problem was fixed on newer cameras, it wasn't ever such a big deal, or we've just been lucky.  I always ask if they want to genlock (either cable or via Lockits), and let people at higher pay-grades than me make the call.

Philip Perkins

[Marc Wielage]

I believe that Robert Kennedy at Coffey Sound told me awhile back that tri-level sync is only an issue if the camera is in external timecode 100% of the time. If the camera just momentarily jams to the external timecode source, then goes back to internal sync, there shouldn't be a green flash (sync instability).

The chief engineer of Technicolor verified the same workflow for me about a year ago, and I think this is the way most of the projects have been done. The only exception would be in multicam projects where all the cameras have to be in sync with each other, so the leading edge of timecode has to be precisely aligned with picture. For that, the only way to go is with external timecode and tri-level sync, or else you run the risk of one camera getting slightly ahead or behind the other.

In truth, the editor(s) can always tweak the picture to get it back in sync, but if you're dealing with, say, a dozen cameras and a major concert project, it quickly becomes a major pain to fix. If it's a feature or commercial shooting short (under 3-minute) takes, I don't think it's going to matter.

But I would also get the post crew involved, ask their opinion, and check the workflow the day before the shoot to be sure.

--Marc W.