One of the great things about flash is that it can be used to freeze a subject’s movement. This is because the flash has a very short duration, and the lower the power of the flash, the shorter its duration so the greater its ability to freeze movement.
Of course you have to find the right balance between exposure and freeze-power, but digital photography makes experimentation quick and easy.
Freezing the movement of water splashes without flash requires a very fast shutter speed of around 1/1000 sec.
In many situations, but especially when shooting indoors, achieving that speed would either require a very high sensitivity setting (which would introduce noise) or a wide aperture (which would reduce depth of field).
Even then, brighter ambient light might be necessary. Consequently, the best method is to use flash.
In his set-up Gavin was using an Olympus OM-D E-M5 Mark II set to manual exposure with a studio light to backlight the subject through a translucent background. He also held a flashgun at the front to provide some fill-in light. The flash units were triggered wirelessly using a sender mounted in the camera’s hotshoe.
The camera was set to a shutter speed of 1/250, the maximum speed at which the E-M5 Mark II can sync with flash. That speed isn’t fast enough freeze the water-splashes, it’s that flash that does the work.
In order to ensure that it’s the flash that makes the subject register on the sensor, Gavin set a small aperture of f/11 or f/16. Without the flash, using those exposure settings (1/250sec and f/11 and ISO 200) the image is black. However, when the flash fires, the subject is illuminated and the movement frozen.
Gavin placed the subject on a sheet of shiny black plastic, resting on top of a plastic box, with the whole thing sat in a paddling pool so that all the water was safely contained. The background, flash and camera were all safely outside of the pool.
With the tripod-mounted camera, subject and flash set-up, I focused manually ready for the action – the splashes could cause the autofocus a few problems resulting in delay or missed focus so it’s best to use manual.
In the first scenario Gavin poured water onto a lightbulb and with a UHS-II card in the camera I was able to fire off shots as quickly as the flash could recycle.
In the second scenario we only used the backlight and Gavin counted down from three before dropping a plastic ice-cube into the coloured water. He advised me to look directly at the glass rather than the screen on the back of the camera, and press the shutter release as I heard the splash.
I admit to whooping when I nailed it first time.
And the second.