Originally posted by jms698 As for diffusers: are they really necessary? Do you only need a diffuser if you are taking a picture with a wider lens than the flash range covers, or do diffusers have other uses?
It depends on what you are trying to do. I use mine to soften the light just a bit when I'm using the flash on-camera. When I'm shooting an event (like a reception or wedding), having the diffuser spreads the light out a bit so it isn't quite as harsh.
The theory is that the larger your light source appears to be, the softer the light will be on your subject. This is why large softboxes and umbrellas can make things look good, because they are spreading the light all around. My little diffuser does the same thing, just on a much smaller scale.
It all depends on the effect you are going for.
Since you are are new to flashes, check out
Strobist Read through the Lighting 101 and 102 articles. It's geared toward off-camera flash, but the principles are the same for on-camera flash.