Jump to content

To tri-level or not to tri-level...that is the question.


RPSharman

Recommended Posts

I think I am still missing something.

I get that if there is a risk of the "green flash" or other internal camera confusion, then tri-level is recommended.  Perhaps if there is some sort of live switcher being employed on set or on a tape show if the original tapes are being used to tape-edit the show (don't know if this is ever done anymore), that providing tri-level sync/genlock to multiple video cameras may be considered important.

But in a narrative form, with current NLE systems, in what circumstance in the post process can an error occur if tri-level sync was not fed to the multiple cameras?  Thinking of it like a multi-camera 35mm film shoot, with dailies and post handled in HD.  Don't they just transfer each camera individually?  As far as I know there is no concern with the multiple camera footage, now on video, being in "phase" with each other, or whatever it is the RED manual talks about.  How is it different with HD footage straight from the camera?

While this might have been foolish, I have never used tri-level sync, even on a 3-camera show I did a few years ago shot on F900s without ever cutting between reloads.  Perhaps they had flashes, but with 3 cameras capturing 7 hours of footage each for 4 days (84 hours) for a 21 minute show it was not an editorial issue, so we never heard of it happening.

I know that just about everyone here is thinking about Lockits or SBT or SB3, and for me it's the new Zaxcom ERX1.  It might be helpful when considering equipment to buy, or considering whether to hook two cables to camera versus just one, to know what sort of real world issues there are with NOT providing tri-level sync.

Thanks,

Robert

Link to comment
Share on other sites

  • Replies 57
  • Created
  • Last Reply

Top Posters In This Topic

You are more at risk for getting green flashes, the result of camera confusion between its internal sync clock and incoming TC by sending it external TC w/o external sync as well.  That doesn't mean it won't work, it just means that green flashes are more likely to happen.  When they DO happen, they are only visible on playback, not during record or E to E.  The situation w/ the RED camera is different in this regard--and actually I prefer their system of dealing w/ ext TC (jam on record) to the old-fashioned continuous ext TC +TriLevel method.  For the record, I like to avoid sending either TC or sync to cameras--I'd rather follow their TC, because I don't want responsibility for the possibility of green flashes that might be caused by a problem w/ the Lockit (unplugged, bad cable, dead batt).

Philip Perkins

Link to comment
Share on other sites

The situation w/ the RED camera is different in this regard--and actually I prefer their system of dealing w/ ext TC (jam on record) to the old-fashioned continuous ext TC +TriLevel method.

Philip Perkins

I am about to do my first job on the RED camera and from what I can gather the RED does not require Tri-level sync or gen lock ever and is not subject to any of the green flash thing. We are planning on everyone being on 23.98, Deva jams some sync box (lockit or Denecke supplied by camera department) and that will sit on the camera. Camera to be set at jam on record as you state.

Link to comment
Share on other sites

I am about to do my first job on the RED camera and from what I can gather the RED does not require Tri-level sync or gen lock ever and is not subject to any of the green flash thing. We are planning on everyone being on 23.98, Deva jams some sync box (lockit or Denecke supplied by camera department) and that will sit on the camera. Camera to be set at jam on record as you state.

No Genesis?

I have done quite a few RED shows with TC only.  Everyone at 23.98.  No calls from post.

Link to comment
Share on other sites

I am about to do my first job on the RED camera and from what I can gather the RED does not require Tri-level sync or gen lock ever and is not subject to any of the green flash thing. We are planning on everyone being on 23.98, Deva jams some sync box (lockit or Denecke supplied by camera department) and that will sit on the camera. Camera to be set at jam on record as you state.

That is not actually true.  I mostly use the method you describe and it works for

normal sorts of shot lengths: what's happening is that the Red jams its internal

TC generator to the incoming TC from the box you jammed earlier and attached to the camera.  The sync will hold ok for a short while--the length of most shots

at least.  If you were going to roll for 30 min, an hour etc w/o a cut, then you WOULD need to use Tri-Level sync in addition to the TC because the camera's clock will cause it to drift out of the jam it did when it rolled--it will be out of

sync with the TC box.  That is the drawback to this sync method, but for most shooting it isn't an issue, AND prevents any green flash or etc problems due to

discrepancies between camera clock and incoming TC.  There have been some reports of problems w/ the RED and Denecke SB2a/SB3 TC boxes, and I have witnessed some bad behaviour by the camera while hooked up to these.  My SBT and the Lockits I've rented never had a problem w/ the REDs.

Philip Perkins

Link to comment
Share on other sites

I've heard of issues with the RED and the various TC boxes, but these cause the camera to not be able to roll (locking up).  But once the camera rolls, I have never heard of any issues with the RED and green flashes or drifting time code.

Technically, I would assume, that if the RED uses the external TC from a lockit to write TC at the beginning of the roll, or if the RED uses it's own internal TC to write TC at the beginning of the roll, then the rest of the time it is using its own clock to maintain speed throughout a take.  There is no difference as to how it runs once the TC is written.  If what you are saying is true, Philip, then the RED should NEVER be without some type of external clock if they plan to run long takes, because the RED clock it too inaccurate.  The reality, however, is that tons of shoots use the RED without external sync, and without incident.

Robert

Link to comment
Share on other sites

An interesting ERX1TCD feature is that if the IFB100 is fed from a TC source that is locked to video sync then the ERX1TCD will be locked to video sync through the RF link and will not drift.

On a separate topic the problem with Red camera not booting with a time code input has been identified. It seems as if the internal electronics of the Red camera has a reset issue if the TC fed to the camera is to hot I.E greater than about 1VPP. The output of the ERX1TCD is software adjustable and this is not a problem for us.

Glenn Sanders

President Zaxcom Inc.

Link to comment
Share on other sites

There have been some reports of problems w/ the RED and Denecke SB2a/SB3 TC boxes, and I have witnessed some bad behaviour by the camera while hooked up to these.

I just want to clarify that the RED lock ups are caused be a high level TC signal at it's input. There are a few SB-2 that have 2.5v TC output which is too high for the RED. The SB-3 does not have this issue as well as the majority of the SB-2 boxes that are out there.
Link to comment
Share on other sites

I have an SB-T on the way that I chose over the SB3 for the tri level option.

But have to admit to also being a bit hazey about when the sync output should be employed.

It seems that often, not feeding video sync to a HD camera will not result in problems. But it seems like a good idea to feed both TC and sync where possible even if shooting short takes with one camera?? Right?

Also regarding the dip switch settings, I see on the SBT user guide:

The Sony F900 is a "Progressive Scan" camera, but its genlock input is SMPTE "Segmented Scan". The SB-T

should be set to position 4 (if shooting at 23.976 fps) and the dip switches set to 01 (Segmented Frames).

Are there any other known exceptions where you may be shooting "progressive" and need to feed "segmented" sync??

Link to comment
Share on other sites

I think it should be, but traditionally sync issues have always fallen on the sound dept. first, or that is the attitude of most productions I've been on.

Philip Perkins

I've had a lot of conversations with people about this before.  At what point did it become and the Sound Dept's responsibility.  Timecode is a reference of time based on a framerate based on what the camera is doing.  The audio isn't recorded based on that framerate.  Especially digital audio which is being recorded based on the sample rate.

J Hemmerlin 

Link to comment
Share on other sites

We provide them the proper timecode.  If their gear can't record it correctly then how is that our problem?

Because of my previous comment.  If post tells the producer that there are sound sync problems it reflects on us and may result in us not being hired again.  The producer sees our job as recording audio that doesn't cause him/her any problems.

So, yes, if you want to make a court case of it, it's not our area.  However, if you want to get hired again, if at all possible, you don't want the producer to hear, "The sound's out of sync" even if technically it's not our fault.

Most producers don't want to parse blame, they want to hire someone who sees that they have as few problems as possible, or they'll hire someone else.

None of this should preclude having a meeting with the producer during pre-production and discussing these issues.  However, keep in mind that the producer would much rather you solve problems for them than for you to bring problems to them.

I guess it boils down to, "Would you rather be right or working?"

John B.

Link to comment
Share on other sites

I've had a lot of conversations with people about this before.  At what point did it become and the Sound Dept's responsibility.  Timecode is a reference of time based on a framerate based on what the camera is doing.  The audio isn't recorded based on that framerate.  Especially digital audio which is being recorded based on the sample rate.

J Hemmerlin

Well, I've been doing sound for film and video since the early 1970s, and it was true then....  Post always blames sync problems on sound first--over the years I've had to do research and then presentations to producers on problem projects where it turned out the CAMERA was running at the wrong speed....  Guilty until we prove ourselves innocent.

Philip Perkins

Link to comment
Share on other sites

We provide them the proper timecode.  If their gear can't record it correctly then how is that our problem?

I'm sympathetic, but the reality is that timecode, reference sync, and video are all related. If they aren't all in the right place at the same time, bad things can happen.

I just got off the phone with an engineer/friend of mine who told me that one place where this can really wreak havoc is with 3D video productions, where two cameras have to be 100% in sync with each other. When no genlock is provided with timecode, essentially what happens is that the video frames starts getting fractionally out of sync with each other -- not a full frame, but just a piece of a frame. If the frame starts drifting one way or the other, eventually the camera will "hiccup," and that's where the green flash hits.

He agreed with me that this should not be a problem on most standard shows, especially with takes of 10 minutes or less. That means jammed code should work for 98% of most productions. I would get more nervous on long-take concerts or 3D capture.

And I also agree that in a perfect world, the D.I.T. should be responsible for all sync, and all mixers would have to do is just supply a momentary TC jam source (or send it via reliable wireless).

--Marc W.

Link to comment
Share on other sites

Because post doesn't tell the producer, "The picture's out of sync." 

They tell the producer, "The sound's out of sync."

John B.

You betcha. Had a situation like that a while ago. Turned out the 16mm camera with a vari speed attachment would not lock up to 24fps and would wander +/-

3-4 frames during a take. To this day the producer still thinks it was the audio that's out of sync even though post proved to him that it was a camera problem.

Eric

Link to comment
Share on other sites

" "Would you rather be right or working?" "

" Because post doesn't tell the producer, "The picture's out of sync." 

They tell the producer, "The sound's out of sync." "

and they don't call the DP in the middle of the night (after a long day, a minimum turnaround!) and tell them they are having a problem syncing the camera.

at least with the issue of keeping 3D cameras in sync with each other, it is all on the camera folks!

Link to comment
Share on other sites

  • 2 weeks later...

Ok, i have a project coming up.  Two F35s and i am going to be recording primary tracks to my PD-606, mono scratch track to the cameras.  If i understand the Tri-level issue correctly, I need two SBTs or lockits feeding both cameras and TC and Word to my PD-606.  I could use just TC from a SB3 to feed PD-606 or use the PD-606 clock as my master clock but Word(or video sync if using a SBT)  would be better to keep tighter sync. 

Am I understanding this correctly? 

Thanks,

Link to comment
Share on other sites

Hey John

I dont know the PD-606 but the Fostex timecode circuitry is usually rock solid. I would go with 2 Lockits or SB-T's jammed from your PD-606 (master)

And then feed both TC and Genlock from the boxes to the cameras.

Doing a test with the whole setup would be good and may help you sleep better:)

JC

Link to comment
Share on other sites

We'll certainly do a test, but i was curious if i need to have sync reference for my PD-606. 

TC stability with PD-606 is very good. I am guessing that it would not make any difference whether i reference the recorder with  word/video or not. 

I think i am getting a handle on this. 

Thanks,

john

Link to comment
Share on other sites

We'll certainly do a test, but i was curious if i need to have sync reference for my PD-606. 

TC stability with PD-606 is very good. I am guessing that it would not make any difference whether i reference the recorder with  word/video or not. 

I think i am getting a handle on this. 

Thanks,

john

If your Fostex is operating properly then the clocks in the SBT/Lockits are no better than the onboard clock in the recorder.  In these sorts of situations I've used the onboard clock/TC generator of my recorder as the master and jammed the camera sync boxes and slates to it.

Philip Perkins

Link to comment
Share on other sites

I like the idea of an SB3 as a master TC.  It allows you to walk around and jam all of your other bits without having to bring them all to the cart.

My experience with Fostex (granted 4-5 years ago) is that if you power them down the TC becomes inaccurate.  This may have changed.  But having an SB3 as a master (jam it with the Fostex for time of day ease, then switch Fostex to external TC), seems like a good idea on any HD shoot.

Robert

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


×
×
  • Create New...