Wireless Slave Settings Needed.

[GovtLawyer]

I just brought home my 580, and will use it on my Rebel XT(on a Stroboframe bracket) with a 420 as an off-camera slave. I've read th manuals twice and during lunch tomorrow, I'll read them a third time. I also read an excellent EOS flash article I found by following a link in one of these forums.

My intention is to shoot pets indoors. I'm sure I'll find some less than ideal lighting situations, as I'll be shooting in pet owner's homes, not a studio. I'm sure there will be times which require the slave to be off camera and filling in some shadows or other uses. I understand that the camera is set for the ambient light, and the flash is automatically set for fill, and I can control the output of the flash either on camera, or in the case of the 580, on flash. (FEC)

If I set the 420 as the slave, they are both in group A, or so I understand. What is the setting I need to use to make sure the off camera flash puts out less flash than the on camera? I know there is a way of setting a ratio between the two, but the group lettering confuses me. I believe that if I simply set the 420 as a slave to the 580, and et them both to A, then the slave puts out the exact same flash as the on-camera. This may be okay, but I'd like to know how to vary them.

Thanks for your help, in advance.

[PacAce]

To use the slave with the master with different ratios, you need to set the slave to Group B. The master will always be set to Group A. Once you've set the slave to Group B, you can adjust the ratios by setting the group ratio on the master. See page 38 of the 580EX manual on how to do this. References to Group A in the manual, although shown as a separate slave flash, in your case would refer to your 580EX which is the master. The Group B flash is the 420EX.

[scottbergerphoto]

There are two ways to do this:
1. Ratios: Master in Group A by default, set slave (420EX) to B. Set your wireless ETTL ratios on the back of the flash.
2. FEC: If you have a slave flash that allows you to set FEC directly on the flash (not 420EX), you can put both Master and Slave in Group A and set FEC directly on the backs of each flash. If you try to do this with each in different groups, the FEC on the Master will control both.

[GovtLawyer]

There are two ways to do this:
1. Ratios: Master in Group A by default, set slave (420EX) to B. Set your wireless ETTL ratios on the back of the flash.
2. FEC: If you have a slave flash that allows you to set FEC directly on the flash (not 420EX), you can put both Master and Slave in Group A and set FEC directly on the backs of each flash. If you try to do this with each in different groups, the FEC on the Master will control both.

If I do as you suggest using FEC, won't both flashes have the same FEC? Are you suggesting that I set both to A and then set an FEC directly on the slave, the 420? Doesn't the master control the slave's output?

[scottbergerphoto]

If I do as you suggest using FEC, won't both flashes have the same FEC? Are you suggesting that I set both to A and then set an FEC directly on the slave, the 420? Doesn't the master control the slave's output?
If you re read what I wrote, you will see that I specifically stated that the 420EX won't work in this method because it doesn't have the ability to set FEC on the flash. If on the other hand you use 2 or more 550EX's as I do, if you set them all to Group A, you can individually dial in FEC on each flash. If you set them to different groups as you normally would with ratios, the Master FEC will override the FEC on the slaves. I know this because I spent the better part of three hours figuring out how Vincent LaForet of the NY Times does it. You can read his article at www.sportshooter.com .

[Jon]

So that's what he does. I remember your post asking about that a while ago. All of them in Group A, then. Note to self, must try setting FEC on the master and stirring a 420EX into the mix. Sounds like that should accept FEC from the Master while a separate 550/580 slave would take its own FEC value setting if I'm understanding you right.