Canon off camera flash power question

First of all:
When a canon flash fires in ETTL it sends out a pre-flash of about 1/32 power. This signal is then bounced back interpreted and the flash calculates the correct exposure setting and then fires.

First question: why are flashes made so that we don't know what this setting was.
Why can I not see what power it just flashed on ( 1/8 1/4 1/2 ??)
My usually procedure is to adjust the FEB up or down, but if I wanted to switch the flash to manual mode it would be nice to know what this setting was.
Ok so I can live with it.

My real question is:

When I use off camera flash in ETTL, say the on camera flash is A and there is a single off camera flash B.
On camera is the master A and B is the slave.
Ok fire in ETTL. Pre-flash. Instantly calculates correct exposure just like if there was only one on camera flash, and then both flashes fire.

Question: When the info returns from the pre-flash (assuming the balance is 1:1) does 1/2 of the calculated exposure go to each flash or does each get a full dose.
If they both get a full dose, why am I not constantly overexposed when using A:B flash?

I think off camera flash, when not using ETTL, is mostly trial and error. I set my aperture, ISO, and flash power based off of what I think a particular shot needs then evaluate the results. If the results weren't what I had intended then I make changes and try again.

My flash isn't capable of ETTL (Lumopro LP160) so I use manual control exclusively.

Dave

Quote:

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Originally Posted by Dave Throgmartin

I think off camera flash, when not using ETTL, is mostly trial and error. I use manual control exclusively.

Dave

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I also use manual control exclusively, however, I do not see it as trial and error. I use a Sekonic L-358 Flash Master Meter. Just make sure your ETTL flash is in manual or the pre-flash will cause error.

Quote:

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Originally Posted by clemmb

I also use manual control exclusively, however, I do not see it as trial and error. I use a Sekonic L-358 Flash Master Meter. Just make sure your ETTL flash is in manual or the pre-flash will cause error.

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Mark,

I didn't mean to imply that it takes 10 shots to get one decent one, just that in my particular case it is trial and error. The process usually only takes a couple shots and maybe 20-30 seconds to figure out then you're good.

Dave

I don't have two flashes but would assume that both dump light until the exposure is met. You can have one flash six feet away lighting only one side of the victim and the main lighting the other. Once exposure is met, they kick off. Of course one side of the face will be over exposed compared to the other. Then you kick in a different ratio to fix the power to give a more pleasing look. Like I said though, I don't own two flashes and barely know how to handle one.