Tuesday, 22 July 2008

Fast flash

One of the challenges when using flash with action shots is coping with the slow recycle times. Hotshoe flashguns such as the Canon 580 or Nikon SB800 take 3 or 4 seconds to recharge after a full power flash, by which time your subject is long gone.

Even with high powered battery flash such as the Profoto 7b you are only going to get a shot every second or so. This essentially means you only get one chance to get a shot before you have to send your model back for another go.

There are normally only two ways around this problem. If you’ve got the budget, use HMI lights. These are continuous lights (i.e. they don’t flash, so you can shoot as fast as you like) and they are also daylight balanced (unlike much cheaper tungsten ‘redheads’), so they are good for use outdoors. They’re what the movie industry uses, and if they can shoot at 25fps then its good enough for us at 8fps. The only problem is that they’re big, heavy, expensive and need to be run off a generator.

The poor man’s answer is to use reflectors. The recycle time on a reflector is pretty fast (humour alert), but they’re only good for fill light. If you need controllable light as your main light then you’re out of luck.

So I found it pretty interesting when the guys over at Competitive Image recently posted about how they used regular Canon and Nikon hotshoe flashes to shoot fast action. They managed to grab runners crossing the finish line at the end of a 1 mile race while still sprinting at full tilt. By running 4 flashes powered down to 1/16th power they were able to shoot at 7fps and still have the flashes recycle in time.

While there are some limitations to this technique (e.g. 1/16th power means you have to have quite low levels of ambient light to allow the flash exposure to dominate), it’s something I’m looking forwards to trying myself. Read all about it, and the problems they had to solve, here.

1 comment:

  1. This is where I wish I had an SLR like the Nikon D70 which would sync at any speed. That way you could crank up the shutter speed and open up your aperature to make the strobes have to work less, but keep your ambient as low or high as you want it.

    I've just bought a Canon G9 which will sync at any speed and it's super, super cool. I'm actually going to start shooting with it more often when I need to utilise high speed syncing.