02-10-2023 06:12 PM
I am filming a multi-day, 2-camera shoot - all in-studio interviews. In the past I have simply operated both cameras independently, and sync’d in post, however I am wanting to sync the cameras properly - so have both cameras share identical timecode, and also – ideally, have the shutters on both cameras opening and closing at precisely the same moment when recording each individual frame, so that each frame from each camera will be a true sync. It would also be helpful if the the B-camera could slave entirely to the A-camera, so pressing the record button on the A-camera triggered both cameras into recording, however this isn’t necessary as their will be a second camera operator. I’m also hoping to achieve the above by connecting the 2 cameras directly vs. using expensive peripherals or “sync” devices, if possible.
I have never properly syn’d cameras before, so please forgive my ignorance. So far, I think I have gathered that timecode can be easily shared between the 2 cameras using a BNC cable. As far as having the shutters in sync, I *think* this requires Genlock? I don’t know what this is exactly, so am looking for confirmation as to how I achieve all of the above via Genlock, or through other methods. Please don’t feel the need to explain every detail to a newbie, simply outlining the basic method and pointing me to some more detailed information on YouTube or elsewhere would be much appreciated.
Any other workflow advice for syncing these two cameras is also appreciated.
Thanks in advance!
02-10-2023 06:56 PM - edited 02-10-2023 06:59 PM
Jason, welcome to the the Sony forum.
I don't know anything about the C300, but I know the FX6 inside and out. It does not have a genlock connector, so you will not be able to sync the cameras in the way you describe. Fortunately, it makes no difference anyway. There is no reason to sync the shutters on the cameras. Outside of a "live" switching environment or a two-camera 3D rig, there will be no benefit to that kind of synchronization. Nor would you ever be able to detect any difference during your edit if you could jump through those hoops. So take that part of the plan off the table and you just made your job easier right there.
If the C300 has either timecode IN or OUT (which I assume it does) you will have no trouble syncing the timecode. I suggest using the FX6 as the master and the C300 as the slave. If you need more details on how to do that, let me know. But it is easy and takes just a few seconds. You should also leave the cameras connected during the shoot to prevent them from drifting a frame or two over the course of the shoot. But eEven if you didn't use timecode at all, syncing a two camera interview is super easy these days in the major NLEs if both cameras are being fed the same audio.
Putting extra effort into the lighting, composition, makeup, audio, having matched lenses, etc. will ultimately pay much bigger dividends on screen than sync.
If this is a super important interview, it might be worth it to rent a 2nd FX6 and have perfectly matching cameras. Could save a lot of time in Resolve.
That's my 2-bits, I hope it helps.
02-13-2023 08:29 AM
Hey Jason, going off what Doug said, @alisterchapman has a useful breakdown on syncing here. He's on these forums, so he may chime in himself! As he points out, and I'm sure you'd be doing, make sure you're using the frame rates on both cameras. 🤖
02-13-2023 12:22 PM
I'll try to simplify this as much as possible as there are some different concepts that are often miss-understood.
SYNC: Is when 2 devices are connected such that they run or operate at exactly the same rate, at the same time. On a video camera a reference signal is fed to a cameras Genlock port and then the "genlocked" camera runs at exactly the same frame rate as and locked to the reference signal. But as Doug has already commented, the FX6 cannot be Genlocked, so there is no way to regulate the frame rate to precisely match that of another camera. As a result when you have multiple cameras there is no guarantee that even if both cameras are started at exactly the same moment that over a period of more than a few minutes that both cameras will record exactly the same number of frames.
TIMECODE: Is a unique, sequential, numerical value given to each video frame by a video camera. Each frame in a sequence must have a timecode value that is 1 frame greater than the previous frame. If you record 1000 frames, the time code count must increase by 1000 in the clip.
EXTERNAL TIMECODE: It is not a sync signal. It is the output of the timecode clock of another device (which could be another camera) that is fed to the timecode input of a camera and then the timecode clock in the receiving camera will follow the external time code value. But this external timecode clock may be counting at a very slightly different rate to the number of frames the camera is actually recording. So to ensure every frame always has a unique sequential number what the camera does is the moment you press the record button the camera takes the last TC clock number that was seen on the external input and from that moment on counts the frames actually recorded and adds +1 to each frame, so each frame has a unique number that is 1 more than the frame before, regardless of the external TC number.
Where you sometimes (often?) get an issue is with long takes. The sync clock in most cameras will drift in frequency very slightly as the temperature of the camera changes or due to other factors. If during the record period the external TC clock counts to 1005, but the camera only records 1000 frames because it is running fractionally slower than the external clock source, there will be a 5 frame difference between the external TC and the TC recorded with the clip. Once you stop recording the cameras TC clock will re-sync with the external TC clock so the error becomes zero again. So, the first frame of every clip will match the external TC, but later in the clip the external TC value and clip TC value may be very slightly out. Generally this is only rarely an issue with clips under 10 minutes. But when trying to shoot long takes such as performances the drift can become significant.
If the cameras are genlocked, because the frame rates of all cameras will be identical, there will not be any timecode drift.
So, when shooting with cameras that can't be genlocked, but do accept external timecode it is a good idea to stop recording from time to time to allow the cameras timecode clock to re-sync with the external TC. If using 1 camera with a sound recorder, if you can feed the TC from the camera to the audio recorder because audio recorders don't have frames, they just place the external TC alongside the audio so going from camera to audio recorder there isn't a sync issue.
02-15-2023 08:59 AM
Thank you everyone for all of this helpful advice!
Reading Doug's advice that we gain little from having timecode sync given the powerful tools now accessible for syncing in post, and also seeing Alister's mention of the potential drift that can occur, especially when we will be recording long clips of 30+ mins, and Genlock bring impossible due to its absence on the FX6, should we forego the BNC cable syncing the 2 cameras timecode all together? Am I right in understanding such drift would cause more harm than good, so we should not risk it? Thank you!
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