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| p.1 #1 · Speedlite Communication - How does it work? |
I watched a video by Syl Arena where he was discussing using multiple Canon speedlites. It was very informative. One point he made was that the master speedlite communicates to the slaves using pulses of visible light from the flashtube which encode timing and power instructions for each slave group. He then demonstrated this by disabling the master speedlite from firing, and taking a picture. The master still made a flash of light using its flashtube, but it did not show up in the photo.
This guy is a pro and has his own Speedliting book, so I consider him somewhat of an authority on the matter. However, the ST-E2 transmitter doesn't have a strobe and emits infrared light to communicate to the speedlites.
So, what's going on at a low level? Do flashtubes naturally emit infrared light along with visible light, so the speedlites simply use what's available rather than having a separate, unnecessary IR transmitter? Or are the receivers on the speedlites sensitive to visible light and IR, and the ST-E2 uses IR because it's cheaper, less distracting, and visible light is simply not needed?
Here's the video. It's worth watching if you want to learn about using multiple speedlites. http://www.youtube.com/watch?v=hk7IRg1ApGE
Here's his book: http://amzn.com/032171105X
Edited on Dec 10, 2012 at 04:52 PM · View previous versions