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SB-T & Ambient


bperlman

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I'm renaming and bumping a thread that began as SB-T vs SB-3. Still hoping to get more opinions on the SB-T vs the Ambient Lockit. I'm leaning towards the locally made and supported product - Deneke SB-T, but still see many more Lockits on the job.

Also, curious about what people are getting for rental - book rate at the rental houses is $50. a day.  It seems a shame to let the camera houses get money for something that is handed to us to deal with on the set. Of course production never seems to question the rentals for the camera department. - i.e. that expensive lense that sits unused for the entire shoot. Ah, but that is a topic for another time.  Most importantly, there is also the element of having confidence in the condition of the unit. If the magic numbers aren't right, we get the early morning call.

Bruce

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For the majority of applications, there isn't any significant difference between a Lockit and a SB-T when considered as an individual timecode or genlock/trilevel sync source.

It's when you add an Ambient Master Controller to the equation that the Lockit comes into it's own. Rather than just jamming, the Controller interrogates the Lockits with the Aaton ASCII protocol when setting and checking timecode. The Controller also provides for the user to tune the timebase of each Lockit so that they have the best sync accuracy available short of using physical cables between units for genlock/trilevel sync and timecode.  Typically, you can tune the system so the sync drift over 10 hours between any number of Lockits to 0.1 frame or better. The limiting factor then becomes the audio recorder but even then you can reverse tune the Master Controller to best match the timecode generator (of the recorder).

As to the use of genlock or trilevel sync, the world is divided into two schools of thought.

The first group believe that timecode is a sync signal that glues everything together and all you need is to squirt it around between devices and all is well. Genlock/Trilevel sync / wordclock is ignored. This group relies on post to tell them everything is OK and for the most part, given that editing systems are frame based, all seems well. One of the fundamental flaws of this approach is that the timecode value has to wait until the start of the next video frame to be registered to a frame. The wait period could be practically anywhere from 0.1 to 0.9 of a frame. It's a lottery.

The second group are of the opinion that timecode is merely a time address for a video frame or audio sample.  They regard the absolute timing and stability of genlock/trilevel sync and audio wordclock timebases as the fundamental necessities of quality camera and audio recorder sync. This group always use trilevel sync from Lockit's or SB-T's to ensure the timecode will be perfectly aligned with the start of the current video frame.

David M

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As to the use of genlock or trilevel sync, the world is divided into two schools of thought.

The first group believe that timecode is a sync signal that glues everything together and all you need is to squirt it around between devices and all is well. Genlock/Trilevel sync is ignored. This group relies on post to tell them everything is OK and for the most part, given that editing systems are frame based, all seems well. One of the fundamental flaws of this approach is that the timecode value has to wait until the start of the next video frame to be registered to a frame. The wait period could be practically anywhere from 0.1 to 0.9 of a frame. It's a lottery.

The second group are of the opinion that timecode is merely a time address for a video frame or audio sample.  They regard the absolute timing and stability of genlock/trilevel sync and audio wordclock timebases as the fundamental necessities of quality camera and audio recorder sync. This group always use trilevel sync from Lockit's or SB-T's to ensure the timecode will be perfectly aligned with the start of the current video frame.

David M

Thank you, thank you, David! This is the clearest and most concise explanation, comprehensible by all and really summing up the current thinking about SYNC. In the real world, of course, even armed with this level of understanding, the implementation of a viable and trouble free workflow is often still quite a mess.

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I think it's pretty well accepted if you're just dealing with one camera, there's no need to use tri-level sync for jamming. But if you're using multiple cameras (like for 3D or for a concert), tri-level is "theoretically" supposed to get everything more-precisely synced.

Every time I've offered to give the assistant another cable for tri-level sync on my SB-T, they always shrug and said, "naaaa, we only use the timecode," and that's the end of the conversation. But I haven't done a multiple Red Camera shoot yet.

--Marc W.

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