MASTER AND SLAVE QUESTION

ok guys....when we have 2 flashes (1 master 1 slave)its easy......
so the question is.....
When we have a slave in group C,can we adjust its power from the master flash (as we do with group B slaves with ratios) or we must set its power from the slave it self by adjusting FEC...? ? ? ? ?

The Master over-rides the Slaves EC value unless you have both in manual mode then you're adjust Flash Power to compensate. The EC value applies to all flashes in the rig not just one.

If you need to adjust the Slave power use the ratios, remember for Canon Ratios they are the reverse of the Studio nomenclature.

Yes, you can adjust the ratio to group C from the master unit, in "A B:C".

Lotto wrote in post #5432138
Yes, you can adjust the ratio to group C from the master unit, in "A B:C".

how......? ? ? ? ? there are no ratios between a:c.....

Ratio for group C is measured and compared to group A and B combind. for instance, ratio of 1:1 for "A:B C" means group C's power is the same as group A + group B. 1:2 means group C has half the power of group A and B combind.

If your question is for how to turn on ration for group C--after using the Mode button to turn on A:B and while it still flashing, turn the wheel on the 580 clockwise one more click.

no..my question is how to set the fec on group C via the master flash....i dont see something like that on my masters screen...
what do i press....? ? have i turn or push something....? ? ?

OK. Let start from the beginning.

1. Switch to master
2. Press Zoom button till Ratio flashing
3. Turn Adjusting Wheel clockwise to A:B C
4. Press center Set button. There, that's where you set the the ratio A+B verse C. Just turn the wheel to the ratio you want.
5. You can go back to adjust the A:B ratio too. Just press the Set button, you will see "Ratio A:B" flashing, turn the wheel while it's flashing to adjust ratio for group A and B.

By the way, I am using the 580EX, not the EX II, but I think they opreates the same way.

I think i confused you alot....
my only concern is what to press,hold,turn, ect to adjust the fec ONLY in group C via the master......
when i turn the wheel it adjust ratios between a:b....
but from where i adjust fec in group C.. ?? ? ? ?

LOL, yes I am confused. Let me ask this: What do you mean "fec" in "adjust fec in group C..."

Ah, just reread the OP, I think you mean adjust FEC on the master unit. If that's the case, you can not. But you can do it from the camera.

i adjust fec on group C via the camera..? ? ? ? no via the master flash...? ? how do i adjust the fec via the camera.......? ? ?

Adjusting FEC on camera affect all groups at the same time. On your 40D, press the iso/FEC button, and turn the back wheel. But to control group C independently from A/B, you can do it 3 ways: 1) A:B C 2)FEC on group C flash, or 3) put flash C to manual mode.

Lotto wrote in post #5432423
1) A:B C or 2)FEC on group C flash,

please lotto....iam intrested only in these 2 ways....can you explain the prossedure with detail for each one...? ? thanks a lot....

Sure! for 1), read post #7 , remember that all the adjustments are made on the master unit, the slave flashes are in ETTL mode and in their own groups. 2) it's easy, press SET button on group C slave flash, turn the wheel to adjust FEC, but you still have to turn on A:B C ratio so the master can fire group C flashes. (After you figure out how #1 works, you will find #2 is not that useful).

you mean theres no a separate setting on the master flash for group C....you mean that by just setting the ratio between A:B the exposure on group C seems weaker or stronger according to what setting we have on groups A and B....so we can adjust the whole exposure by setting the ratio togroups A and B and set the exposure value into the camera to adjust the whole's image exposure......am i right..? ? ? ?

(ps....i understood the way no2......i just have to clear up the way no1.....
is the explanation above correct..? ? ? ?)