First thing that springs to mind when I talk about freezing action is shutter speed. To be honest you’d normally be absolutely spot on, but there’s one very important thing you really need to know about shutter speed and flash.
Every heard the term “sync speed”? It’s the fastest shutter speed your camera can handle where the shutter is open long enough to expose the whole sensor to the flash of light. It’s most likely to be 1/125th 1/200th or even 1/250th second at the most. Go faster then that and you’ll get a horrible black strip over the image. To put it another way, in the studio setting a faster shutter speed isn’t the answer.
So how do you freeze action? Simple, make the burst of light last for less time.
A burst of light from a typical studio flash head will last for around 1/500th second. It’s called the flash duration and you can think of it as the effective shutter speed. 1/500th sec is pretty fast, but that’s a walk in the park for a speedlite which can reach easily speeds of 1/8000th second or faster.
As you’ll see in the video below a speedlite is easily fast enough to freeze my daughter bouncing on a mini trampoline.
As is often the case there was a lot more I could have shown you in the video, so here’s some extra content for my blog readers…
So you’re probably thinking there must be a down side, and you’d be right. First the speedlite isn’t as powerful as a studio flash head, so I increased the iso to 400 to compensate a little. The second problem is the speedlite takes a while to get up to full power which meant several missed shots.
In the studio I use multiple lights to achieve the look I want, but as I only have a couple of speedlites I had to be a bit more careful about where they were placed. The main light was put in a Lastolite ezybox at 45 degrees to the model. To fill in the shadows I placed a large white reflector on the opposite side.
The Pocket Wizard radio flasg triggers are amazing devices allowing you to maintain full E-TTL even off camera. The practical up shot of that is you can forget about setting the flash strength and concentrate on the other stuff, like focus, posing and aperture.
You’ll probably have noticed that I used a second speedlite to light the white background. Although I could have also set that to E-TTL control, experience has taught me that the white background fools the system. So I set the second speedlite to manual and dialled in 1/8th power. I also deployed the flash diffuser to give a big spread of light.