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01-26-2010, 06:09 AM   #1
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Wireless P-TTL Question

How many flashes can be supported in Wireless P-TTL using the on-board flash as a commander? And if so, how many flashes can be supported?

I haven't seen any documentation on using multiple P-TTL flashes as wireless slaves, but sometimes there is a brief mention every now and then.

Does anyone have any experience shooting wireless P-TTL with multiple slaves? And if so, can they share?


Last edited by Kazy; 01-26-2010 at 06:18 AM.
01-26-2010, 09:25 AM   #2
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I'm not the true expert, but this is the way I understand it works:

1. The initiating flash (for instance the build in flash) does a pre-flash trigger, all flashes do the pre-flash.
2. After which the camera calculates the amount of output power needed.
3. Then the main flash trigger is send. All flashes that can see the trigger flash and are on the same channel will contribute.

Since the flashes don't know about each other, and the light calculation is done independent of the number of flashes used.

I can only wonder if with multiple flashes the output calculation is done right.
If it initiates a flash with -3 Ev based u pon the 3 flash preflash, will 2 or 3 flashes with -3Ev have the same effect if the setup was done with only 1 flash?
The more I try to reason the logic the more I cannot see what the difference is.
If you'd work with 3 flashes and they all contribute for 1/3 of the light on the subject, -3Ev for 3 flashes * 1/3 = -3Ev for 1 flash.
The same logic works for 5 of 99 flashes I guess...
01-26-2010, 10:10 AM   #3
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I have an AF540FGZ and a pair of AF360FGZ's and have used them all simultaneously. I don't know that there's a maximum. Note that the commander doesn't know anything about the flashes--you set each flash up separately with with flash comp and contrast-control ratio (e.g. 1/1, 2/3, 1/2, 1/3). You can control all together with flash comp on the body. Flashes don't "talk" back to body, and system is all optical so if the slave sees the controller/master, it will fire. Camera just observes at the effect of firing all flashes during pre-flash, then tells all flashes what the output level will be--not individually, just one level; each flash applies that level to its own configured contrast-control ratio & comp.
01-26-2010, 10:55 PM   #4
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Thanks for the quick answers. I've just ordered one P-TTL flash (Sigma EF-530 Super), and was wondering whether I could upgrade to another one and control them both using the on-board flash on my K200D.

01-27-2010, 02:59 AM   #5
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I use three Sigma flashes, and I've used all three of them together in wireless P-TTL mode without problems using the on board flash as master or controller.

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