Happy with the 600EX-RC

[RustBeltRaw]

Canon don't use IR for flash control - it's all visible light

Then why doesn't the ST-E2 have a flash tube? I'm under the impression that the red lenses over the flash eyes are either infrared-pass filters, or they they "listen" to instructions in the red wavelengths only. Ultimately, I suspect we're splitting hairs, because the actual communication band may be broad enough to include infrared, and at least a little visible red.

As usual, the truth is in the manual. From page 35 of the ST-E2 manual (note highlighted text):



On the other hand, the 600EX-RT and 580EX II manuals do not contain the word "infrared." Further proof that CiC gets into levels of information that only the manufacturer's engineers probably know.

[Colin Southern]

Then why doesn't the ST-E2 have a flash tube?

It does - pop off the red filter and you'll see it

The red filter biases the ST-E2 output towards the red/IR end of the spectrum, but with flashes like the 550EX, 580EX, 580EX II, and 600EX the transmitting is done by the main tube. If you test fire it in a dark room you can actually see the pulse. Nasty little units they were!

Many mistake the red LEDs for IR transmitters, but they're just AF assist lights.