Canon ETTL question - multiple slaves, angle, distance etc

Discussion in 'Canon' started by BD, Dec 10, 2007.

  1. BD

    BD Guest

    Hey, all.

    Here's my setup:

    Canon 30D
    70-200 f/2.8L IS
    550 EX (as master)
    2x 430EX (as slaves).

    I have the master directly on the camera; I have the slaves on stands.
    I am using flash umbrellas.

    In my home environment, I had no problem configuring the flashes to do
    what I wanted - using the master for metering only, using a ratio on
    the slaves, etc. ... all seemed well.

    I got to my 'real' shoot yesterday, and had no end of problems getting
    the flashes to communicate. I just stuck in fresh batteries, and was
    about 15 feet away from each slave.

    It seemed as though the angle that the slave was oriented was a real
    picky point. I haven't confirmed this, but I gather that ETTL is not
    RF, and so orientation of the slaves is critical. But half the time,
    the slave would not fire. I'd move the master by half a foot in one
    direction, and the left-hand slave would fire, but the right-hand one
    would not.

    Eventually, I had to give up, as I was not getting reliable results in
    this room. I pulled the flash off, opened up my lens all the way (f/
    2.8 - yay), set my ISO to 1000, and got reasonably decent hand-held
    results with no flash.

    Question - what the heck is going on here? It's almost as if when you
    use umbrellas on these slaves, you have a teeny angle of useable
    orientation where the slave sensor is visible to the master, but is
    not blocked by the umbrella!

    And then, I flipped the camera to portrait orientation - the lens was
    completely blocking the signal between the master and the right-hand
    slave. It was ludicrous.

    I see two possible options here: 1: put my master on a stand (having
    found it's 'sweet spot', and connect the body to it with a off-shoe
    cord; and 2: buy one of those dedicated flash triggers. Maybe that has
    more power to the signal or something.

    Can anyone offer any suggestions here? Am I completely out to lunch
    with respect to what I was seeing with the flashes' behavior?

    Thanks for all wisdom!!

    BD, Dec 10, 2007
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  2. BD


    Communication between your flashes is IR so anything blocking line-of-sight
    between them would cause you issues. Also, distance between master and
    slaves and the angle between IR pick-ups and transmitters can create issues.

    I think you could tie them together with a sync cord...

    Better option would be to get some real flash heads with RF remotes. Check
    out Alien Bees... You would loose the ability to use ETTL but you will get
    the hang of it....
    DBLEXPOSURE, Dec 10, 2007
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  3. BD

    Ali Guest

    Ali, Dec 10, 2007
  4. BD

    BD Guest

    I wonder if it would be too 'hokey' to rig a little mirror on the
    slave flash - have the signal bounce off it between master and
    slave... might be silly, but if I'm not in a place to put another
    $500 into gear just now, it might be a stopgap option...
    BD, Dec 10, 2007
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