Reverse engineering how Canon flashes communicate
This is an incredibly geeky topic, but it’s a subject I find absolutely fascinating. It involves how flashes communicate with the camera and reverse engineering the “language” they use to talk with each other. In this video, Roger Nieh of Science’n’me takes a look at the Canon flash protocol using an oscilloscope to eavesdrop on that communication.
What makes the Canon system so interesting, and Nikon’s AWL system is that they don’t use radio. They use optical signals. This is what’s commonly referred to as the “pre-flash”. That quick burst of flash that appears before the shutter opens and causes some subjects to blink by the time the real exposure actually happens.
It’s something I’d started to delve into myself a few years ago with Nikon speedlights in order to create my own custom AWL/CLS commander. I had no real practical use for it except, perhaps, to hook it up to laser or sound triggers. But it just seemed like a fun and interesting project at the time.
Unfortunately, I wasn’t able to fully reverse engineer everything before I started moving away from Nikon speedlights and towards other brands of flash which supported radio communication. And my learning process was much slower, without access to an oscilloscope.
Roger, however, delves right into Canon’s protocol in order to figure out the protocol and cause a custom LED to remotely control his Canon speedlight.
It’s far too complex to try and explain here, but if this is something that interests you, watch the video above.
John Aldred is a photographer with over 20 years of experience in the portrait and commercial worlds. He is based in Scotland and has been an early adopter – and occasional beta tester – of almost every digital imaging technology in that time. As well as his creative visual work, John uses 3D printing, electronics and programming to create his own photography and filmmaking tools and consults for a number of brands across the industry.