Hi. The white casing on a flash imitates an umbrella look and is good for that soft look in close shots. For larger shots it won't work.
Here's what I do and I have a shot to illustrate. I use two slave flash. Slaves are triggered by the light from the on-board flash. For large shots I space them, mounted on their own tripods, about 10-feet on either side of my SLR. When I fire the shot all three lights go at once, like this.
http://www.flickr.com/photos/jimsphotostuff/4212028989/sizes/l/
As you can see it's a large scene and I had three flash units, my on-board and two slave units. By the way these slaves are pretty reasonable. At Rits they're about $35. each. The tripods are from Wal Mart at about $30 each and the flash units take AAA batteries so power is never a problem.
There is one thing you need to know however, and we can discuss further if you wish via e-mail.
If you decide to go with slaves, there's a little trick you have to do to get a good result. You must
use red-eye. For some reason the camera wants to shut down the aperture on standard flash.
I suppose it's all the extra light but on red-eye it doesn't shut down.
Trust me you'll need to practice with these lights - position and camera settings can be critical to
good results. Good Luck.
