TC divergence at DVinfo.net

Bill Ward · June 30th, 2012, 08:29 AM

Spent most of last week on a two camera shoot, using an XDCam as the primary camera, and an EX-3 as the 2nd unit. Most of the interviews, we jam synced the TC between the two cameras with a BNC cable left in place during the interview, which worked fine.

I was surprised, though, so see how fast the TC swam apart between the two units when not cabled together--often coming seconds apart from each other in just an hour or two...and 15+ seconds apart overnight while on free run.

I didn't expect a total lock...but that's a lot of TC drift. The EX-3 was largely running faster, if I recall.

Dave Sperling · June 30th, 2012, 03:11 PM

Seems like quite a bit of difference.
Were both cameras constantly powered and on during the period that this much drift occurred? Typically if running on battery power we plan to re-jam time code every time a battery is changed, since most cameras drift when disconnected from power, and many drift as well when powered down.

John DuMontelle · June 30th, 2012, 07:18 PM

Did both cameras have the same drop-frame time code setting? Cabled together for the entire time You were shooting would force them to be the same. However, if one camera had it's time-code set to "drop-frame" and the other camera's time-code was set to "no drop-frame" you would get the problem you describe. If you disconnect the cable from both cameras after the initial jam-synch...they would drift apart over the time periods you describe and that would explain the difference as well.

Doug Jensen · July 2nd, 2012, 05:36 AM

It's also recommended that you genlock them if you want perfect sync.

Bill Ward · July 3rd, 2012, 09:21 AM

Hmmmm....drop/non drop might be an issue.

On the EX-3 if you shoot progressive, the DF is a disabled choice. But the XDCam disc camera was still set to DF...so that is likely what was happening.

Funny part is that for some reason, I was under the impression that progressive was always non drop. I should probably know these things...

Dave Sperling · July 3rd, 2012, 11:57 AM

I thought that 24P was always non-drop, whereas 30p could be either...
The time differential should be a factor of about .001 (if I remember correctly) if that was the issue.

Bill Ward · July 3rd, 2012, 07:17 PM

Well, then, if so even more curious, since we were shooting 24p. Go figure.

June 30th, 2012, 08:29 AM	#1
Bill Ward Major Player Join Date: Jul 2005 Posts: 580	TC divergence Spent most of last week on a two camera shoot, using an XDCam as the primary camera, and an EX-3 as the 2nd unit. Most of the interviews, we jam synced the TC between the two cameras with a BNC cable left in place during the interview, which worked fine. I was surprised, though, so see how fast the TC swam apart between the two units when not cabled together--often coming seconds apart from each other in just an hour or two...and 15+ seconds apart overnight while on free run. I didn't expect a total lock...but that's a lot of TC drift. The EX-3 was largely running faster, if I recall.

June 30th, 2012, 03:11 PM	#2
Dave Sperling Major Player Join Date: Jan 2010 Location: Tinton Falls, NJ Posts: 780	Re: TC divergence Seems like quite a bit of difference. Were both cameras constantly powered and on during the period that this much drift occurred? Typically if running on battery power we plan to re-jam time code every time a battery is changed, since most cameras drift when disconnected from power, and many drift as well when powered down.

June 30th, 2012, 07:18 PM	#3
John DuMontelle Regular Crew Join Date: Dec 2005 Location: Miami, Florida USA Posts: 114	Re: TC divergence Did both cameras have the same drop-frame time code setting? Cabled together for the entire time You were shooting would force them to be the same. However, if one camera had it's time-code set to "drop-frame" and the other camera's time-code was set to "no drop-frame" you would get the problem you describe. If you disconnect the cable from both cameras after the initial jam-synch...they would drift apart over the time periods you describe and that would explain the difference as well. __________________ John DuMontelle - Freelance / Miami, Florida - USA http://www.latincamproductions.com/

July 2nd, 2012, 05:36 AM	#4
Doug Jensen Vortex Media Join Date: Jan 2009 Location: Florida Posts: 3,450	Re: TC divergence It's also recommended that you genlock them if you want perfect sync. __________________ Vortex Media http://www.vortexmedia.com/ Sony FS7, F55, and XDCAM training videos, field guides, and other production tools

July 3rd, 2012, 09:21 AM	#5
Bill Ward Major Player Join Date: Jul 2005 Posts: 580	Re: TC divergence Hmmmm....drop/non drop might be an issue. On the EX-3 if you shoot progressive, the DF is a disabled choice. But the XDCam disc camera was still set to DF...so that is likely what was happening. Funny part is that for some reason, I was under the impression that progressive was always non drop. I should probably know these things...

July 3rd, 2012, 11:57 AM	#6
Dave Sperling Major Player Join Date: Jan 2010 Location: Tinton Falls, NJ Posts: 780	Re: TC divergence I thought that 24P was always non-drop, whereas 30p could be either... The time differential should be a factor of about .001 (if I remember correctly) if that was the issue.

July 3rd, 2012, 07:17 PM	#7
Bill Ward Major Player Join Date: Jul 2005 Posts: 580	Re: TC divergence Well, then, if so even more curious, since we were shooting 24p. Go figure.