Syncing (Genlocking) Arri Alexas from a Tentacle

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As all the current Arri cameras (Alexa, Alexa Mini and Amira) can Genlock or sync from the timecode stream from a lock box, they can of course do so from a Tentacle. For long concert recordings where sync is important to prevent drift, I normally use another brand of lock box for this, and a client of mine is a bit worried about trying it with something so small as a Tentacle. We see a lot of Alexa Minis on hand held or steadicam rigs lately. The camera operators would prefer Tentacles!

I’d like to be able to tell him of people that are using Tentacles to Sync Arris in real life.Is anyone here doing this over longer takes (10min-90min) with success? The only post here I could find about this they were having trouble with green flashes, but I think their Tentacles were on the wrong framerate.


A way to find out the drift when not using genlock is to record also audio on the camera, preferably a duplicate of the separate audio recorder. Record a long take, for at least an hour. Then align the head of both camera audio and separate audio in ProTools sample accurate. Then look at the end how far they are apart.
Temperature may have an influence on this test but nowadays most clocks are good temperature compensated.

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