Basic, dumb question about using multiple speedlites

I'm typically shooting with studio strobes in manual mode, and I wanted to try an experiment now that I have two speedlites (580EX II and an older 580EX). After reading both manuals, I'm not sure how to do what I had in mind, and it's probably very simple!

My plan was to use the 580EX II on the camera hotshoe as my fill flash, with the 580EX off-camera as my key light. I wanted to use ETTL with a 2:1 ratio of key light to fill. The manual describes how to set ratios between different slave units off-camera and how to turn the master on and off, but I didn't see a way to do what I want. What am I missing?

If the master on the camera is firing it is in group A.

So does that mean I can put the one off-camera slave in group B and then set the A:B ratio to 1:2 and have the right thing happen?

Yup. I've done it a few times now - just testing the functionality. However, the couple times I have used this for actual shooting, I end up using manual settings so I can set the power to specific levels. It is really nice to be able to do this from the back of the camera vs. shooting with manual wireless triggers and having to walk to the flash each time you want to adjust power.

That's what I did here and used the full moon for a rim light.

Wow, that full moon gives off a lot of light! I played around with it last night, and it worked just as you guys said it would. Imagine that! My guinea pig was probably seeing spots before his eyes after my test shoot with direct flashes, but a little food, and he'll forget all about that. Now that I see how that works, I'll try it with some modifiers on the flashes. I've got a mini softbox for the fill flash, and I want to use a beauty dish for my key light. I know I can use the Kacey 22" BD, but I haven't yet tried the speedlite with the Mola Setti. I'm not sure if the Kacey Elinchrom adapter will work with the Setti. If it does, that'll be my next experiment.

sdipirro wrote in post #14208999
Wow, that full moon gives off a lot of light!

Some lotion on my neck and bald spot and I'm all better. Naw, I had an old Sunpak 5000AF in optical slave mode above and behind me and I had it set a little hot. But power was low enough that it fired with the E-TTL and command preflashes and also the main pulse.