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how long is a second?

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Richard Sutcliffe
how long is a second?
on Apr 8, 2009 at 3:49:00 am

I'm having some issues in post that I suspect I cant do much about but I don't really understand it.

We shot some athletics on the HPX500. the race was recorded as a single clip and the duration of the clips does not even come close to matching the duration of the race. The stopwatch stopped at 03:50:63 sec but the duration of my clip from gun to crossing the line is 03.54.50 sec.

Shot PAL 720/50p, editing on PAL 720/50p

The cameras were shot iso without any genlock or sync and I wasn't expecting accuracy to 100th of a second but a 4 second discrepancy seems very high, shouldn't a second be a second? Anyone else experience something similar? How could I avoid this in the future?



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Shane Ross
Re: how long is a second?
on Apr 8, 2009 at 4:06:41 am

Are you timing from when the stop watch started to when it stopped? Or the entire clip duration? Because I am sure you started rolling before the camera started, and a bit after it stopped.



Shane



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Jeremy Garchow
Re: how long is a second?
on Apr 8, 2009 at 6:27:27 am

In your case, 50 frames


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Noah Kadner
Re: how long is a second?
on Apr 8, 2009 at 7:15:00 am

I wouldn't get too concerned about this, over 3 minutes you're bound to see some timecode drifting between two completely unconnected clock sources. Unless someone is watching your video with a timecode reader display on screen they will never know the difference.

Noah

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Jeff Brown
Re: how long is a second?
on Apr 8, 2009 at 12:19:15 pm

Maybe -- but a 1.7% time difference? I think there's something else going on. Don't know what. Anyone? Buehler? Anyone?

-jeff


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Noah Kadner
Re: how long is a second?
on Apr 8, 2009 at 2:26:28 pm

Yeah I'm surprised it's not much more to be honest. As someone who works with timecode smart slates and sync boxes there's really nothing shocking at all that two unconnected devices count seconds completely differently. That's reality folks. A second is not the same to every electronic device...

Noah

Check out my new RED Blog. Unlock the secrets of the DVX100, HVX200 and Apple Color.
Now featuring the Lens Adapter Guidebook, Sony EX1 Guidebook,
DVD Studio Pro and How to Light Interviews.
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Chris Cardno
Re: how long is a second?
on Apr 8, 2009 at 3:13:04 pm

Does the HPX500 have the Pre-Record function? If so, and that was on, that would explain the additional recorded time.

Chris Cardno
Visual Edge Productions
Bethesda, MD

Chris Cardno
Visual Edge Productions
Bethesda, MD


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Michael Sacci
Re: how long is a second?
on Apr 8, 2009 at 5:45:36 pm

I think he is timing from the time the start gun goes off, to the time the runner breaks the ribbon at the end of the run, and not the duration of the clip. The question I would ask is the stopwatch just in a guys hand and he is starting and stopping it? If so could he not be late on the start and early on the finishes? Or is this timing gear that is set up big track events?






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David Coleman
Re: how long is a second?
on Apr 9, 2009 at 9:50:32 pm

Is your time code drop frame or non-drop?


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Matthew Romanis
Re: how long is a second?
on Apr 9, 2009 at 10:35:00 pm

There is no drop frame capable in PAL recordings. Even if the option is toggled it has no effect. Besides the time offset would be more like 7.8 seconds difference.



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Richard Sutcliffe
Re: how long is a second?
on Apr 15, 2009 at 9:42:21 pm

Thanks for the responses, been away on a job and wasn't able to check the forums.

Yeah, the timing gear was pro track timing, I cut the clip at the gun going off and winner crossing the line so its as close to the official timing duration as I could get it.

This is PAL so yeah, no drop frame issues.

I'm glad to hear its not me who thinks the drift is excessive.

I'm wondering whether its a problem/limitation with the HPX500, unfortunately the other cameras buttoned on and off so I have no other continuous clips.

Anyone willing to put their HPX500 against the clock and see if it drifts by as much?



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Matthew Romanis
Re: how long is a second?
on Apr 15, 2009 at 10:46:29 pm

Just a quick experiment to try.
Get your own stopwatch (or clock with a second hand, you could use the computer clock too), roll the footage and start your own stopwatch and compare the result.



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