Genlock has been a tool used in the broadcast world for years for multi-camera shoots. It does have a place in the feature film world for 3D, but doesn’t hit the radar very often. The Red Epic Camera is a common choice for Feature films, episodic television, and commercials, and happens to be an ideal choice for 3D for it’s form factor. 3D may or may not be a passing phase, and really only viable for the large theatrical feature, so why should we all know how to Genlock the camera?
A lot of productions will use multiple cameras and the time code should match frame accurately across the board between cameras and sound. In post, re-syncing every take does take time, and costs money. A lot of cameras, the Red Epic included, are not accurate enough when it comes to the frame accuracy of holding the time code between devices. Even with a Lockit Box mounted on the camera, the initiation timing of when the camera starts each frame will cause the code to drift by one or two frames. Without the Lockit Box, the camera will drift up to a few seconds over the course of the day. Now I’m not suggesting that there is a problem with Reds camera and don’t mean to single it out, I’m just suggesting that there is a difference between phasing on different cameras and there is a solution.
So what is Genlock?
There are several different flavors of “generation lock” or synchronization of the initiation of each frame, but a very common one in HD video is called Tri-level Sync. The source of the Genlock signal will generate a composite standard definition video signal. A black frame with no picture info at the frame rate you wish to lock to. If you look at that signal on an oscilloscope to read the electrical signal, you would see a black video frame at 0 or neutral, and at the end of each frame it drops to negative to initiate the end of the frame. It then jumps to positive to initiate the start of frame and then back to neutral. It’s called tri-level for the three states: neutral, negative, and positive. The camera syncs to the negative to positive transition to initiate the start of each frame.
The combination of a Lockit Box attached full time to the camera with a time code signal as well as a genlock signal will give you frame accurate time code and fewer calls from post.
To set up the Red Epic with an Ambient Lockit:
1. Epic: Set the project rate on the camera to 23.98 (as the most common setting)
2. Epic: Set Sync to Genlock and Brain. (settings, setup, GPIO/Sync)
3. Epic: Set Time code to external:brain. (settings, project, time code)
4. Plug the break out sync cable into the Sync port on the back of the camera.
5. Attach a Lockit box. The green “Genlock” lead goes to the sync or “video/word” connector on the lockit. The yellow “Time Code” lead goes to the “Timecode Out” connector on the lockit.
6. Lockit: Set to 23.98, P, Tri-level sync. On an Ambient ACL-202 the switches are: on, off, on, on, off, off, off, with the two switches on the right to the right. On the ACL-203: switch 1 to position 3, switch 2 to position 0, switch 3 to 0. The most important part here, no mater what model or brand you have, is the Progressive signal. The Epic will not read a PSF or interlaced sync signal.
7. If set up and jammed correctly, the TC marker on the Red LCD will light up green, and the Sync and Gen markers will also light up as green.
8. Your time code should now be in perfect synchronous.