Distance flash photography

I'm often trying to take pictures at karate tournaments from 30-40 feet away standing on a chair with a telephoto lens. I'm wanting to get a 580EX just because it gets such rave reviews, but I'm wondering about one of those big, professional, handle-mounts like Sunpak makes.

It's kind of awkward for normal shooting and I'd have to have a smaller flash, of course, but for what I've just described, should I consider one of those units? I've perused the forum here and apparently, almost nobody uses these things, or at least posts about them.

Anyone have any experience with them, or thoughts/suggestions? Can I get a module that mounts on the Digital Rebel XT that will do E-TTL II metering with a handle mount?

Thanks much, in advance.

John Collins

If you get the 580EX, you can bump up the ISO to 400 or 800 to easily get the 30 to 40 feet working distance. You can also attach a flash extender, such as the Better Beamer {http://birdsasart.com/​accs.html#BEAMER}, to extend the flash range when using lower ISOs and the lens isn't fast enough.

have a look at the guide number calculations
heres a cheat sheet showing distance @ various ISO and F stops
http://www.night-ray.com/photores/Photo​CheatSheet.pdf