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Old May 17th, 2008, 03:44 AM   #1
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Free Run Time Code out of sync

After reseting the time code on two EX1s the free run time code indications fall out of sync. For the first five minutes everything works fine (completely in sync) with cameras on and off. As time goes by the two EX1s start to fall out of sync, in the beginning in maters of a few frames and in a day or two in matters of hours. Could that be the internal battery? Could that be the turning on and of causes the cameras to draw power from the internal battery more or less each time thus causing the malfunction?
One of the two cameras is a loaner from Sony because my second one is at service.
Any suggestions?
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Old May 17th, 2008, 09:30 AM   #2
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A small amount of drifting is typical of cameras which are not Genlocked. Sony specs for professional cameras have typically had a +- 10 frames an hour difference when not genlocked. This can add up. I am not sure how it can add up to hours easily without something else going on. One of the cameras may actually have a problem but one should only expect complete accuracy for a short time using the method you describe. Some cameras lose a few frames powering off and on and this adds up over time. The best practice requires a fair amount of checking the timecode and resetting as needed.
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Old May 17th, 2008, 09:41 AM   #3
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I had the same issue with two cameras. They were set up identically (by transferring settings) and they were off by several seconds each running hour.

This was using clock time code.

I am amazed that my twenty year old (admittedly, Swiss) self-winding watch keeps better time that the EX1. I mentioned this to a DIT at Panavision and he said it is not unusual for the larger Sony cameras to do this as well. He says he has to jam sync F900's every hour or two to keep them locked. Unfortunately you can't jam sync the EX1.

The answer, I guess, is the EX3 with an external time code generator.
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Old May 18th, 2008, 10:03 AM   #4
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Eric,
You would have to have two twenty year old watches next to each other to see how well they stay in sync with each other. Also I don't think watches are very good at capturing moving pictures. The cameras crystals for the video frame rate makes the cameras clock run at different speeds than pure clock time. Turn off the camera and you turn of the sync for the clock. Add in Non Drop and you already have a system which will drift from real time at 3 seconds and 8 frames an hour if my memory serves me correctly.
But Seriously my solution to this would be cameras and recorders would have a way to use GPS time in free run although this would not necessarily solve the genlock issue without some nifty engineering
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Old May 18th, 2008, 10:59 AM   #5
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Daniel,

There are plenty of external timecode generators that can stay within a frame or two for half a day. +/- 1ppm.

The EX1's TCG is not even close to those specs. Drop Frame has nothing to do with it.

Not a big deal - but the facts of my experience.
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Old May 18th, 2008, 07:00 PM   #6
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Eric,
You are right the EX 1 is not close to an external timecode generator specifications. Since those external Timecode boxes don't generate or record pictures they don't really stay in Sync with the cameras and recorders which they are the clock for without Genlock either. The external timecode boxes are very good clocks however and video cameras are usually not good clocks. My experience with video cameras has been they drift apart from each other unless they are genlocked and fed timecode and the causes are not clear why one camera drifts farther than another and using one manufacturers cameras over another has not always been the answer either. I have had DVX 100s drift with Free Run timecode wildly as well as Sony Betacam cameras. Using two of my Panasonic SDX-900s on a reality show last year we used an external box for timecode and both cameras drifted in different directions through out the day based on battery changes powering up and down etc. The budget determined how much Sync was worth to us per day and we lived with the drift rather than get external boxes for each camera. Whether there is a problem with Ex 1's or not I would not expect them to stay in Sync for long based on the design and lack of External sync input.
My point about Drop and Non Drop is Video cameras don't really keep clock time as they make frames at set rates which have a relation to a frequency rate which has a relationship to the clock. If you count every frame of a camera running at 59.97 you end up with 1 hour and 3 seconds and 8 frames over an hour of clock time. This is when it is working correctly. Any small variations over time are perfectly within the manufacturers specs and will leave you with footage with different timecodes.
Bringing this back to the original question the best practice for syncing cameras which don't genlock and take external timecode is to check them after syncing often and don't expect perfection because you will hardly ever achieve it until it makes enough financial sense for the manufacturers to make it more accurate.
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Old May 19th, 2008, 01:43 AM   #7
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Quote:
Originally Posted by Daniel Epstein View Post
Eric,
You are right the EX 1 is not close to an external timecode generator specifications.
That was my point regarding the original poster's concerns and all that really matters on this thread - that, right or wrong, you should expect drift when shooting with multiple EX1's in clock sync mode.




I am well aware of what drop frame does. But it's wrong to assume that the EX1 needs to pull down its internal clock and cause it to drift when recording video. The internal time-of-day clock and the timecode recorded are only loosely linked.

If you look at the behavior of the time-of-day clock compared to the recorded timecode in clock sync mode, you will see that they are synced when convenient but by no means completely tied to one another.

When undercranking, the EX1 uses clock time as a starting point but allows clip time code to progress more slowly, drifting behind time-of-day. 29.97 NDF is treated the same way, as a slight undercrank. 29.97 DF code allows the recorded time code to keep up with the time of day.

In NDF mode, recorded time code can drift between cameras with synced clocks depending on when the record trigger was pressed on each camera. But with the EX1, it's not just the recorded code that drifts - it's the clocks themselves.

There is really no reason why the time-of-day clock in the EX1 or any camera cannot be more accurate, even though self-defined "manufacturer's specs" don't require it. I reiterate that my mechanical watch does better.

As an off-topic aside, when overcranking, the EX1 leaves clock sync mode completely and temporarily switches to record run mode. It uses the ending timecode from the last recorded clip as its starting point and records from there at a rate faster than real time. The goal, I assume, is to keep recorded timecode from creeping into the future, which would present a problem in the form of duplicate code when returning to time-of-day recording.

It is theoretically possible to record "future" timecode when overcranking. I have not tested how the EX1 handles this to prevent duplicate code. It has piqued my curiosity and I will test it at some point.
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Old May 21st, 2008, 05:29 PM   #8
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All of which bring us to the use of the good old slate for non stop recording with two EX1s or strobe synchronization when doing event video.
Then what is the use of free run time code? Just to have a rough synchronization? Any way to avoid the hard work at the timeline especially when one camera goes on and off all the time thus making the use of a slate (especially during weddings and events) unusable?
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Old May 24th, 2008, 08:22 PM   #9
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synching two EX1s

Assuming I'm going to slate each shot to get a hard sync point, how does one get the free run time codes to match, at least at the begining?
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Old May 24th, 2008, 09:00 PM   #10
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There is no way to jam sync them that I know of, but you can get them pretty close with the clock setting menu. You preset the time (even the second) and the clock starts the moment you press "set"
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Old May 25th, 2008, 05:47 AM   #11
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I remember seeing a a posting somewhere in the past about 2 X Z1 syncing with the remote control. I wonder if the same thing will apply to the EX1.
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Old May 25th, 2008, 07:44 PM   #12
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Yes you can sync them with the remote. Thing is that after a few minutes the two free run time codes get out of sync due to the fact that each one runs a bit faster or slower than the other. You may get out of sync in five minutes in a matter a frame. As time goes by frames (of difference) start to add up.
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