External flashguns are great aren't they? As well as being far more powerful than the built in pop-flash on DSLR's, they usually come with a head that swivels, like in the above photo. This allows you to bounce the light off a nearby wall or ceiling. But why is it important to bounce the flash?
The smaller the light source, the harder the light.
Or to be more accurate, the smaller the light source in relation to the subject, the harder the light. Consider the light when he sun is shinning, you get strong shadows on the ground, and then when there is cloud cover, the light source spreads out and becomes larger, and consequently the shadows become much softer.
When you bounce the flash, instead of the small flashgun being the source, the wall becomes your light source, consequently the light is much softer.
What's the problem with hard light
For portraits, hard light is not very flattering as shadows on the face and on the background will have a very hard edge, plus hard light creates highlight on noses, cheeks and foreheads. Not what you want!
Compare these two photos of my wife Jane
Guess which one used bounce flash!
How to bounce the flash.
For individuals or small groups, the best way to bounce the flash is to turn the flash head around 30-45 degree (depending on distance your subject) so that the light bounce off a nearby wall. It doesn't have to be a wall, could be a pillar, a building, or even someone wearing a white shirt standing close by. Just make sure that whatever you're bouncing from is white or has a neutral bright colour.
If there are no nearby walls or when photographing a slightly larger group, consider bouncing the light off the ceiling. When I do this, I just just point the flash straight up and use a white card attached to the flash with a rubber band or velcro. You can make your own (in the UK the white card material I use is called 'Funky Foam').
You can also purchase professionally made bounce cards, here's one I recommend:-
Peter Gregg's Better Bounce Card