Wireless off-camera flash is terrific for location portraits and shooting on the go. But sometimes a single flash just doesn't have enough output. A simple solution is the Lastolite Triflash Bracket for $65. The bracket works with your existing light stands and umbrellas. But it allows you to mount up to three flashes on a single stand. There's the pop you're looking for.
I also read about a new version of this device called the Lastolite TriFlash Sync. It "features a built in sync system allowing the photographer to fire up to three flash guns from one triggering device. Featuring a built-in slave cell, the Lastolite TriFlash Sync can be adjusted to allow for none, 1, 2 or 3 pre flashes if required." But I haven't been able to find a dealer for this device yet. Will keep you posted if I do.
If you like this kind of stuff, be sure to check out my Off Camera Flash title on Lynda.com. I show you all sorts of helpful lighting techniques that are especially good for portraits.
More Off Camera Flash Tutorials
Off Camera Flash - Basic Techniques for Pro Results
Light Modifiers for Off Camera Flash
Off Camera Flash - The Single Light Portrait
"More Off Camera Flash" - Digital Photography Podcast 233
I remember being surprised to discover that tying a second flash to my first gave me only one additional stop of light -- but of course, one stop is double the light. So I could bump my ISO down from 800 to 400 ISO, or open up from f/8 to 5.6, but it wasn't as earthshaking as I thought it would be.
So adding two flashes to your single flash does what -- gives you two more stops? That's pretty sweet -- ISO 800 to 200 is a big deal, as is opening up from, say, f/11 to 5.6.
What I like about using multiple flashes is not the doubling of the light, per se. I like that I can reduce my flash power by a full stop on each flash. This means I'm getting the same flash output but with a faster recycle time and less wear and tear on my batteries. Using a third flash would increase the recycle time even more while extending my battery life even more!
I rigged my own multiple flash set up, but decided to purchase two triple flash set ups through ebay for $25 and they're paying the postage from China.