> I've read numerous mails about using simple slave flash
> units with EX550 in master slave configuration.
> My understanding is that any preflash triggers the
> "simple" slave (too early).
>
yes it does
>
> I'm now trying to find out if it is possible to use
> two EX550s (one on-camera and the other not) and an
> additional "simple" slave flash (thus 3 flashes total)
> successfully. All flashes in Manual exposure mode.
>
It is possible, but still with pre flash to trigger the slaves if master set to ETTL.
If master set to manual also then you're OK but you will need a flash meter to set
exposure (aperture)
>
> The camera is EOS-3 in Manual exposure mode as well.
>
> 1) Do I still get preflash (for communications between
> EX550s) if the two EX550s are in "Manual" mode but the
> on-camera is set to "master" and the other one is set
> to "slave"?
>
As above
>
> I don't even know if I can set anything in the slave
> if it is set as "slave" or does it get all instructions
> from the master flash only?
>
In slave and manual mode the 550s are only triggered from the master, no
power/exposure info is sent. However you can set all manual parameters by pressing
and holding the mode button until you get manual and then multi modes selected whilst
in slave mode. you still need manual flash metering though as the slaves only receive
trigger, no other info. Bear in mind that all ratio control is available with the
EOS3. Have you considered triggering the other non speedlight/EX flash from the sync
socket via cable as this only fires at time of film exposure (as I understand?!).
>
> 2) Does the slave EX550 flash if it is set to "M" (Manual)
> AND the Master/Slave-switch in master-EX550 is set to OFF and
> the same switch in slave-EX550 is set to "OFF" (or "slave")?
> Thus is there any setting when the second EX550 acts as a
> dumb manual slave only?
I the master is set to off (flash output - not the master/slave switch) it will fire
the control pre-flash, This is true in all modes as it will always act as a master if
set to master - hence pre-flash. If you set the master/slave switch to off this sets
separate individual flash units and thus no wireless control at all.
Thus for any sort of master slave control you will need a single master unit and one
or more slaves. If a master is active then there will be a pre-flash.
And yes it can be very confusing. What I strongly recommend is that you wait 'till
you have finished your current film then with an empty camera body test all the
possibilities (it is just about possible to see the pre-flash - especially if you
focus on a close light subject so that main flash isn't too bright. I still think the
sync (PC) socket may be your answer, just be careful of metering!!!
Cheers, Braham.
>
>
> Maybe this was already answered but I may have missed it.
> Sorry if so.
>
> Vesa
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