Nudibranchs can be found virtually anywhere — from tropical coral reefs to the frigid arctic waters of the Barents Sea. They come in all sizes, from just a few millimeters to well over 30 centimeters (12 inches), and nudibranchs exhibit a variety of colors, bodyshapes, feeding habits and unusual biology seen in few other animal groups.
The word nudibranch means “naked gill,” which is appropriate, as these delicate creatures lack the shells normally found on marine snails and slugs. More than 3,000 species of nudibranchs are already known to science, but there are still lots of undescribed species still waiting to be found.
Often times, just finding nudibranchs is the hardest part to photographing them. When searching for nudibranchs to photograph, it is helpful to know a little about their biology and feeding habits. Most of the species are rather particular when it comes to food and will only eat one or very few specific food sources. Nudibranchs are carnivores, and their diet includes such treats as stinging hydroids, sea squirts, soft corals and even the eggs of other nudibranchs. Getting to know the dietary preferences of your subjects will greatly improve the chances of finding and photographing individual species on your checklist.
Trickier Than You Think
Once found however, nudibranchs are among the easiest animal subjects to shoot underwater, but they do come with a unique set of photographic challenges. Many nudibranchs tend to stay close to the bottom, making it difficult to compose shots other than top-down images of mostly seafloor. In this case, you’ll want to get really low, so you can create separation between the animal and the seafloor. They don’t move much even with strobes firing multiple times, which certainly makes things easier in terms of composing a nice frame. But on the flip side, don’t sit around and wait for these sea slugs to move into better positions! Always evaluate each situation to make sure you don’t waist valuable dive time on a subject that will never look good, or will use up all your air while you wait for the right pose.
Some species feed on bryozoans that grow on the surface of kelp fronds, but here you have the challenge of shooting a very small subject on a moving target. In either case, patience will be the best strategy to your nudi nuisance.
Because nudies can be as small as one centimeter, it might be difficult to fill your frame with the subject. While a 60mm macro lens will allow the photographer to get extremely close to the subject, it will create a problem when finding space for the strobes. When too close to a subject, it becomes tricky to achieve nice lighting. When visibility allows, a 105mm macro is often a much better choice, as it gives you greater working distance between your camera and the subject for positioning your strobes.
To get even closer, which will allow you to fill the frame further, you might consider adding a teleconverter or diopter. As an optical element, the teleconverter will steal one or two F-stops of light, but since macro photography normally involves the use of strobes at close range, this is not a problem. Also, make sure you shoot at really high F-stops, such as f/22 or f/32, to get maximum sharpness with as much depth of field as possible.
A diopter also works like a magnifying glass, and will essentially shorten the focusing distance of your lens by anything from half to almost nothing. These days, several manufacturers offer wet diopters that you can mount or dismount at your leisure underwater, greatly widening the range of possibilities when you’re down below. For instance, you may check out the +5 and +10 SubSee diopters made by ReefNet, but manufacturers like Seacam and Sea&Sea, also produce their own diopters for particular lens and camera configurations. High-quality optical diopters are available that mount via an adapter, fitting most macro ports from most manufacturers, while others screw right into threads at the front of certain macro ports.
Composition is King
Composing dynamic nudi shots when working with especially small subjects is the real challenge. Wave action, current (nudibranchs tend to thrive in current-ridden areas, where their food also thrives), and moving kelp and hydroids all work against you. A couple extra weights, or even ankle weights are useful when shooting close to the bottom in turbulent water.
Try shifting to manual focus and focus bracketing by moving the housing back or forth. Autofocus tends to miss the target slightly when working with really small subjects, which is easy to miss when looking at the camera’s small LCD display. But getting the composition right is often what separates ordinary run-of-the mill nudibranch images from the truly great ones. There are some basic rules you can stick to, like the rule of thirds and diagonals – but don’t forget that rules are meant to be broken at times.
In addition to the general composition of the image – focus and depth of field – it is always important to take into account the background of the image. If the background is cluttered and full of objects and different colors, your subject will not stand out and make a lasting impression on the viewer. Who wants to view an underwater fruit salad?
Finding a calm, uniform background often gives you the best results. A good option is to go for simple black background, which is easy to achieve once you find a nudibranch with a little open water behind him. Use a high F-stop and fast shutter speed to remove all ambient light, and get low so only the water column is in the background. Follow these steps and you will create the perfect black backdrop to complement the brilliance of nudibranchs, whether in Norway, or anywhere else around the world.
Taken from SDAA issue 02/2012