Author Topic: EXT Master Clock  (Read 1741 times)

Tom C. Hall

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EXT Master Clock
« on: October 30, 2013, 09:12:46 PM »
I have been wishing to use Canon EOS cameras with genlock setting for awhile now. Being able to use them cheaply for Stereo 3D as well as 360 video panorama, lightfield research, video stitching, time slice, HDR video and other odd applications could be revolutionary.

Both cameras in order to scan continuously in perfect sync require an external reference clock. While I have ton plenty of tests with the dual photo trigger method, for anything more than slow moving subjects it's unusable. Using audio input on a single channel you could feed the cameras a square wave at the appropriate Hz. (the drop slope being the trigger point for the clock.) Signals for other frame rates could also be easily generated. I found this to generate short test tones.

The camera listening to this audio input would only trigger photos or video start recording in time with the pulse. For video the camera could be trusted to run an arbitrary number of frames (24) before waiting and rechecking the pulse during a closed shutter. I'm not sure if that is possible without some very complicated timer0 / timer1 mathematics or just stop/rec - new video file mess. With this in theory the cameras sensor phase should be very close. It may be nessesary to include very fine phase adjustments anyway to account for lags from sending the signal through DAs, wireless sound or very long cables. Adjusting the phase would be very easy by just viewing a strobe and comparing the rolling shutters.

  • External Clock source via audio input
  • Switchable sync modes. NTSC 23.976hz, 29.98hz PAL 25hz
  • per camera phase adjustment
  • Video and timelapse intervalometer slaving
  • A more advanced function would have headphone jack generating a sync signal

An interesting application would be to slave the intervalometer to this sync for locked timelapse photography if the cameras are too far apart to be tethered, for photographing very time sensitive moments and multiple focal lengths or positions.

I am not a programmer in the slightest, just a Camera Technician and Stereographer but I have some programmer friends and am trying to wrap my head around how these cameras work. I am still trying to read very heavily into the magic lantern wiki to pull as much understanding as I can and approach this in the most intelligent way.