Shooting 3D with 2 Cameras and Synchronisation (Camera Rigs)

It is important to understand that no matter how much you slip and slide the clips from you cameras in the edit suite timeline to bring them into sync, if the images captured by the two cameras sensors are not in sync, you may have some big problems. Even if you press the record buttons on the cameras at exactly the same moment, they may not be running in sync. In the edit suite you can only adjust the sync by whole frames while the cameras may be running half a frame out and this can be impossible to correct in post production.
Remember that from the moment you turn a camera on it is capturing frames. When you press the record button the recording doesn’t start instantly, but at the start of the next full frame, so the synchronisation of the camera is dependant on when the camera was turned on and how long it takes to start working, not when you press the record button….. Unless you have Genlock, which overrides the cameras own internal clock and matches it to an external reference signal, forcing the camera to run in sync with the sync source which can be the second camera or a sync generator.
It is possible to shoot 3D with non-sync cameras, but any motion in the scene, or camera movement such as a pan may lead to strange stereoscopic effects including distortion of the 3D space, un wanted depth changes and moving objects appearing to float in front or behind where they should really be.
This doesn’t mean that you can’t use a non sync camera, just that it is less than ideal and it’s use will limit the kinds of shots you are able to do.
If you don’t have genlock a further option is to use a pair of Canon or Sony camcorders with LANC control. It is possible to get special LANC controllers such as LANC Shepherd or the controllers I have listed below:
These work with most camcorders that have a LANC port or AV/R port and provide good sync for periods of up to around 15 minutes at a time. To reset the sync the cameras must be powered off and back on. They work by synchronising the start up of both cameras and then measuring the sync error. The sync won’t be perfect, but it will be good enough for most 3D applications. However as there will always be slight variations in the master oscillators in the cameras, over time the sync will start to drift apart. The controller will tell you how far apart the sync is and when it becomes excessive you will need to re start the cameras to bring them back into sync, typically you get between 10 minutes and 20 minutes of useful synchronisation.

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