Wednesday, July 20, 2011

Technique: Capturing a Splash

The photo technique for capturing a high speed splash is not difficult once you understand the basic setup.  When taking pictures of water, or glass for that matter, you need to begin by lighting the subject from behind.  Since transparent liquids and glass allow you to see the background, this is the surface you need to light first.  If your subject is highly transparent, like water, the background may be all you need to light.  Otherwise you can add two more lights, one pointing directly at the subject from behind, and the other aimed at the subject from the front.
Blue gels were put over the lights to add some color to this scene.  The background lights were aimed low so there would be a fall off of light causing a gradual shadow towards the top.  Note the black lines in the water.  These are caused by reflections from the black tub placed beneath the water to catch it.  The lines help sharply outline the water shape against the light background
Equipment:

The key to freezing high speed action is having a light that gives off a very short duration of flash.  Most flash units made for SLR cameras fall into this category.  The flash duration is even shorter when the flash unit is used at a lower power rating, such as 1/16th or 1/8th power.  The trade off here is in depth of field.  In order to keep the splash in full focus you will need to stop the lens down to a low aperture, such as f/11 or f/16.  

A light meter that can measure light from a flash is helpful, but not absolutely necessary.  You can probably come close enough to the correct exposure with some trial and error tests.

This setup uses four Nikon SB-900 flash units.  Two are aimed at the background.  The other two are aimed at the subject, one from behind right, the other from the front left.  Two units are used on the background to keep the flash power on a low setting that will allow for even shorter duration of flash.  The black tub does double duty.  It catches the water from the splash, but also caused black reflections in the liquid and glass to help define its outline. 
 
Setting up the camera:

Your camera may have trouble focusing on the splash so set it to manual focus and, with the camera on a tripod, take a manual focus reading of an object placed in the spot where the splash will occur.  Put the camera in its manual exposure setting and choose the highest shutter speed you can for your camera/flash combination.  This is usually in the range of 1/250th of a second.  A lens of medium focal length is a good choice.  The ISO setting should be set low to maximize quality. 

An assistant dropped one ice cube into the soda from about a foot above the glass.  Timing has to be perfect to capture the splash at the right moment.  Try keeping both eyes open so you have a peripheral view of the hand dropping the ice cube and can be prepared to snap the shutter at the right moment.
 
The exposure on the background should be approximately 1-2 stops brighter than the light falling on the subject from the front.  With the camera set to the correct exposure for the subject, the background will now be pure white.

A shot like this requires pinpoint timing and very good hand-eye coordination.  An assistant threw a dart at the water balloon, and the shutter had to be pressed just as the dart entered the frame.  Keeping the shutter button half-pressed will shorten the length the finger has to travel to complete the exposure.
This is a combination of two water splashes similar to the one that began this article.  They were put together and twisted with post-processing software.  The exposure setting for all the images in this article were done at 1/250th second, ISO 200, and f/14.

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