Tips for how to use backlighting to liven up your underwater photography.
Front lighting is the most common lighting technique in underwater photography and works very well in almost all situations. However, images lit this way using 2 strobes on equal power, can sometimes appear 'flat' with minimal shadows. An alternative technique is backlighting – illuminating your subject from behind. This will give a more creative edge to an image, and can accentuate specific features of your subject.
Here are some tips to help you get started with this interesting lighting technique:**
Strobes are most commonly used for backlighting, however don't forget about your spotting light or torch - they can also give very nice effects (and torches are widely used for backlighting shooting macro). Use long strobe arms to position your strobe/torch behind the subject, or detach the strobe/torch and hold it in one hand while shooting with the other. If you have a willing buddy they can hold the light in place for you, leaving you with both hands to shoot in a more stable position.
Only using backlighting behind your subject can result in a silhouette with an accentuated outline of the subject, and a glowing effect if the subject is translucent.
Alternatively, you can balance the backlighting with front lighting as well – this will make 'foreground' details of your subject pop, for example the eyes and fins of a fish, while the backlighting shows a prominent outline of the subject.
Using a snoot will help to avoid stray light, and minimize backscatter. A flexible fiber-optic snoot is useful for shooting one-handed – you can comfortably hold the strobe facing forward and closer to your camera, while the fiber-optic snoot can bend backwards on itself behind your subject.
Most strobes have a useful 'slave' option, and can be placed on a tripod behind your subject, and triggered by the internal flash of a compact camera, or a second strobe if using a DSLR.
A better (but more expensive) option is to use a third optically triggered remote strobe on a small tripod. This ensures consistent strobe positioning, and is especially useful for wide-angle when shooting larger subjects from further away, but also using two strobes on your camera. With no wired connection to your camera you'll have complete freedom of movement to compose your images as you desire. Be aware the light from your master strobes doesn't affect your backlighting. Also make sure the master strobe has direct 'line-of-sight' to your remote strobe's sensor.
Be careful not to damage any marine life when you're moving your camera with long strobe arms; using a long snoot; or setting up a remote strobe on the seabed.
Set your camera with a fast shutter speed, small aperture (high f-number), and a low ISO to minimize ambient light – which can sometimes reduce the backlighting effect.
Avoid strobes or torches being visible behind the backlit subject in your image. This can be tricky for small macro subjects, while using a large strobe or torch. Again, a snoot comes in useful to counteract this problem.
Soft corals, sea fans, tube anemones etc. are easy subjects to start with when using this technique for the first time. Look for subjects with rough outlines and hairy appendages such as Hairy Frogfish or Weedy Filefish for example as the backlighting will enhance their outlines. Thin, translucent, (and stationary) subjects are great for backlighting, such as nudibranchs, jellyfish and Leaf Scorpionfish for example, which can look like they're glowing from within. Thicker, moving subjects such as larger fish, turtles etc. will often require additional front lighting, to avoid capturing only the subject's silhouette.
Through trial and error, and carefully reviewing each image on your camera's LCD screen, you'll see how the visibility, lens choice (macro/wide-angle), strobe position, size of the subject and its translucence will determine the necessary strobe power and strobe-to-subject distance to capture the perfect backlit image.
Getting the lighting 'just right' in underwater photography can be difficult at times but it's absolutely paramount when it comes to capturing the perfect shot. The backlighting technique is one of many useful techniques you should gradually learn, that will really enhance your portfolio.
Christian Loader (30, UK) is a full-time professional photographer for Scubazoo Images www.scubazoo.com . He has worked extensively throughout SE Asia as an underwater videographer and photographer, and lives in Kota Kinabalu, Sabah, Malaysian Borneo.