Hi all -

I was wondering whether there was anyone here who could help me with a little problem.

I've just bought three of the Canon Speedlight 600EX-RT's. These are not actually going to be used with a Canon camera, but with my ALPA FPS.

I'd read that these have radio transmitters built-in, but since I won't be mounting them on a Canon, I thought that if I got a wireless trigger and connected that up to the flash set as the master, then when the master was triggered, it would fire the two slaves.

Now this is when it gets confusing.

With just one flash set-up, and the wireless trigger (Phottix Aster) connected to my ALPA FPS, with the receiver connected to the sync port on the 600EX - success. I fire the shutter on the camera, and the flash fires.

Set up the first 600EX as the master, and the second two as slaves, in radio mode, manual exposure.

Press the test button on the back of the master, and all three fire.

However, fire the shutter on the camera, and only the master flash fires.

Set the flashes to communicate on IR, and not radio, and all three fire when I fire the camera shutter. Unfortunately though given how these are going to be used, I don't think I can rely on the IR communication.

Now I'm assuming I can get around this simply by buying another couple of receivers, and ignoring the radio facility in the 600EX's completely, but I can't for the life of me work out why the current set-up doesn't work.

If anyone could provide some advise on where I might be going wrong, it would be much appreciated!

Kind regards,