I love festivals. The light, the colour, the motion. It's this last element - the motion - that can often be the hardest to capture.
Too slow a shutter speed and everything is a big blur, too fast a shutter speed and you completely freeze the action, which makes it hard to tell whether something is moving or not.
The happy balance is to have a bit of movement (but not so much that it's all a big blur) while still retaining some frozen parts.
All sound a bit complicated? Well it's hard enough during the day, but just try it at night! To tell you the truth, I actually find it easier at night. But to make it easy for yourself you need to take control of your camera, move it out of auto-pilot and into manual mode.
First let's have a bit of a think about what our camera does at night when you use the flash in different modes. Now remember I shoot Canon but it will pretty much work the same, give or take a few minor differences, no matter what brand you shoot.
Firstly if you put your camera in one of the Automatic modes your camera will most likely default to around 1/60th second. That means that your flash will fire but because you have such a fast shutter speed (relative to how dark it is) that your background will be completely black. The shutter isn't open long enough for the background to be recorded. Not a good look.
So you think it might be better to put your camera into Aperture Priority mode, or maybe Night Portrait mode to ensure that your flash fires but the camera will take into consideration the ambient light and give you a long exposure. Sounds good in theory, but in practice you might find that because it's so dark you will get such a long exposure that everything is blurry. Too blurry to see what's going on.
So it's time to take control of your shutter speed and the best way to do that is to put your camera into Manual mode. I usually find that at a shutter speed of anywhere from 1/8th second to 1/15th second I can handhold a camera (with a wide-angle lens on it) pretty steady. I then experiment with my aperture to find a happy medium where I still have a pretty good depth of field but my background is nice and bright. For most situations around f5.6 to f8 works pretty well. This is assuming an ISO of 400.
So now that I have my ambient exposure set it's time to turn my flash on. No need to put your flash into Manual mode. Leave that in full TTL and let it do it's magic. I find that by aiming for a slight lull in really frenetic action I can pretty much freeze the motion of moving performers while still getting just a little bit of blur to show the movement.
Remember too that festivals at night are held under artificial lights which are usually a bright orange colour when they're recorded on your digital sensor (if it's on the Daylight setting). So stick that little piece of orange cellophane over your flash to get a more natural look.
Having your camera in Manual mode means that you're not constantly having to keep an eye on your shutter speed - it's already set. Your flash in TTL means that you don't have to worry about that because they're pretty much magic and get it right every time! So basically you have nothing to worry about except getting in the thick of the action and taking great photographs that capture the motion.