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Old May 1, 2011, 8:54 PM   #11
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Quote:
Originally Posted by peterbj7 View Post
- after all the flash does go off, but at low intensity...
It has to go off, the low intensity pulses from the built-in flash are what control the other wireless slaves... Check the green timings below, these low intensity bursts do not contribute to the overall lighting:

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Old May 1, 2011, 9:46 PM   #12
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It needs to produce a wireless signal, but why does that necessitate a visual one?
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Old May 1, 2011, 9:54 PM   #13
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Because it's not infrared (IR) they are visible pulse of light!
-> Only the ST-E2 transmit wireless IR, your Di-866 (or 580EX) 'Master' will transmit the same visible light as the built-in flash!

See here: http://www.learn.usa.canon.com/resou...le.shtml#page4

"PLEASE NOTE: Even if the master unit's flash firing is 'disabled', the flash will still appear to go off. However, it will NOT in any way affect the image exposure, because the flash you see is simply a pulse light signal that the master flash emits to transmit settings/shooting data to any slave flashes. This pulse light flashes a fraction of a second BEFORE the photo is taken."

and

"The only real limitation you need to keep in mind is that because the Wireless Speedlite System relies on flash pulses for control and communication, each slave unit you use has to be able to “see” the pulses from the master flash unit (this is why the master flash appears to go off, whether or not you have 'enabled' it)"
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Last edited by NHL; May 2, 2011 at 6:46 AM.
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