Does anyone know how to use the 580EX flash to trigger a slave flash, without actually firiing the 580EX?
I've read in the manual that it can be done, but couldn't find how to do it.

Going from memory: Hold down the Zoom button until the flash head starts blinking in the picture. Roll the wheel until you see the Flash emitting from the picture disappear.

Awesome! thank you. I got it to work!!

Just out of curiosity, why not just use a Pocket Wizard?

Actually, I am using the radio popper...and I wanted to turn off the main flash...without having to switch over to my ST-E.

Did you get this to work?

Are you able to set the remote flash power manually while using the RPs or do you have to use ETTL?

Scott

Why didn't I think of this?
I have been using the ST-E2, but have thought of using my 2nd flash as the transmitter while connected to my camera. I chose to not try this because I prefer not to use on-camera flash when I can get away with it. By toggling between turning of the flash on & off, I now have a great solution to this concept.

Thanks.

Ugh...
I just got my 580EXII tonight and I've been trying to do this, too... and it won't work!
I moved the dial until it says "off".... just like it says here and in the manual... but it still fires!

Any ideas?

It is still going to flash but it's a preflash. Look at the pictures and you should see light only coming from the off camera flash.

Thank you Scottie!!
In the middle of the night, this occurred to me, and I had to get up out of bed right then and take a couple shots to see... and you're right. That's exactly what it was.
Duh!

You can do both with the built in Canon infrared system.

You can use it to pop the remote flash in manual mode. What's good is you can enable ETTL mode or Manual mode from the master unit. This means you don't have to go to each remote flash to change the power. You can even set each remote flash to a different slave group. And control the manual power output of each slave group independently from the master unit.

What the Radio Popper brings to the equation is the reliability of radio and thus ends the line of sight problem and extend the range of the system.

So to summarize. With the Radio Popper, you can shoot in manual mode like the pocket wizard but with the advantage of being able to dial up and down your remote flashes from your camera. And obviously, with the Radio Poppper, you can shoot your remote flashes in full ETTL mode.

Hope I make sense.

-David