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Alexa drop frames because of time code?


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I have a dumb question, does the Alexa hold TC during battery changes? or do jam after every batt change ?

In addition, I don't understand why people put a box on the outside which performs the same function as the box on the inside.

I say jam the Alexa and leave it be.

Robert

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In regards to the battery change timecode question. In theory the Alexa will maintain the Internal timecode for about 10 minutes.

In production, that has worked for me.

At this morning's Ambient briefing at Coffey/Trew Audio, Sebastian, their rep, said that he was getting reports from users that the capacitor in the Alexa would not reliably hold code for more than a few seconds. His theory was that operator error was drastically reducing the expected ten-minute safety window. If the camera is shut down prior to the battery exchange, it should hold code reliably. If everything stays powered on, the demands of the viewfinder, operator displays, etc. will quickly drain the capacitor. Its an untested theory but it makes some sense.

David

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I recently did two Alexa projects: one, the assistant jammed from the SB-T box; the other, the AC went external in all day (no jam). Both methods worked fine.

I usually prefer for them just to jam every so often, just because I worry if the cable is bumped or something, there might be a momentary "burp" in the code, which will cause a glitch. Under controlled conditions, it should be perfect.

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Thanks for all the replies. We changed to jamming. By drop frames I meant that single frames were lost, happened maybe twice a day. Still wondering what that has to do with TC.

In theory if the camera is aligning its TC to its "frames" then by not supplying both sync and TC you could cause a glitch in the recording by the camera trying to follow two non-synchronized clocks. This issue dates back to the Sony F900, and was controversial then as it is now. This was why Arri really preferred us to jam sync and then let the camera run on its own clock. I prefer this method as it is simpler and thus less failure prone than adding the Lockit to the camera.

phil p

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So according to that theory if I use an ERX1TCD there should be no glitches because it never loses TC?

This is not correct. An ERX1TCD will accomplish continuous timecode just as a jammed sync box attached to the camera does this. I think the glitches being referred to, as Phil P. mentions, come from only TC being input to the camera without sync (gen lock).

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This is not correct. An ERX1TCD will accomplish continuous timecode just as a jammed sync box attached to the camera does this. I think the glitches being referred to, as Phil P. mentions, come from only TC being input to the camera without sync (gen lock).

The Arri guy wasn't keen on feeding the camera either sync or TC all the time from an external source (a la RED). In my recent shoots with Alexa we've jam synced TC (w/o sync) then disconnected the external TC gen. from the camera and it ran on its own clock.

phil p

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The Arri guy wasn't keen on feeding the camera either sync or TC all the time from an external source (a la RED). In my recent shoots with Alexa we've jam synced TC (w/o sync) then disconnected the external TC gen. from the camera and it ran on its own clock.

phil p

Another reason to like the Arri approach. Seems like the best idea, jam the camera TC system and walk away. Evidently this works. I wish my next movie was using the Arri Alexa --- no such luck: RED Epic.

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