Backlighting Underwater Subjects: When, How and with What

Backlighting for Enhanced Impact: A Short Introduction

In our quest for ways to best define certain kinds of marine subjects, one of the more interesting tools available to us is backlighting. This is never going to be the most common approach to take photos, but with the right kind of subject, it is possible to achieve unique and striking results.

Image Shen Collazo

What equipment do you need?

You can certainly backlight with your existing strobes as long as you have arms that are long enough to get the strobe behind the subject. This is going to mean you are pretty close and utilizing a close focusing macro lens.

The other option is to disconnect one strobe entirely and place it still connected (usually with fiber optic as it is easier) behind your subject.

One of our favorite ways to achieve backlighting is just to carry a small Inon S-2000 around in our BC pocket. Not only is the S-2000 diminutive in size and weight; it also has an extremely sensitive 360 degree optical pick up to trigger the strobe. This means no cables are required at all offering maximum flexibility with placement. Of course the other Inons offer this flexibility as well in a larger form factor.

Sea & Sea strobes have traditionally only worked with a fiber optic or electrical sync connection attached. That may have changed with the new YS-D3 Lightning strobe that offers an optional slave trigger accessory that can be used for this, but we haven't had a chance to test how well this will work yet.

Another excellent tool for triggering a strobe behind a subject it the latest version of the Anglerfish Remote Trigger. This clever slave triggering device allows triggering of one or two strobes by fiber optic or electrical sync in a remote location; so compatible with just about any strobe.

A strong constant light source like a powerful focus or video light can also be an option for backlighting. While not as powerful a light source as a strobe, you have the advantage of "seeing what you get" which allows you to tweak the look you want more easily. This can work quite well for macro subjects if you have enough exposure latitude. Some of these lights can also provide red,green or blue LED lighting or utilize filter gels for special effects. The new Kraken Hydra 3500 S+ RGB WSRU offers several color options for special lighting effects.

Subjects

So what kind of shots are you likely to be successful with? Here are a few guidelines to keep in mind.

Look for subjects that have a distinctive silhouette that will capture a viewers eye. Seahorses, batfish, tube anemones, distinct nudibranchs, squid and shrimp like Hairy or Skeleton Shrimp are possibilities.
Does the subject have any transparent or translucent features that will light up and "glow" with back lighting. Anemones, some shrimp, hairy frogfish, coral polyps and flame scallops are good examples of these subjects.
Is the subject sedentary enough to put up with a camera on one side and a strobe on the other?
Can you light the backside without injuring marine life of any sort? Protect your subject's environment first, consider the shot second.

This hairy shrimp looks solid when lit from the front. Image Kevin Palmer

When lit from the back, the hairy shrimp looks transparent and "glows" Image Kevin Palmer

Technique

Most of the time, you do not want the camera to "see" the light source directly. If it does, it will mostly be blown out exposure in those areas. If your subject is large enough, then a light placed directly behind the subject can work well. If it is too small for that, then try placing the light source just out of the frame of the image. So right, left, above or below, with the light angled towards the back of the subject.

Image Chris Parsons

If shooting a strobe, it will often not be easy to adjust strobe power on the backlighting. TTL will not work well for this kind of shot, so get used to adjusting your aperture for exposure over several shots until you are sure you have it dialed in.
If shooting with a constant light source, either shutter speed or aperture can help adjust your exposure. If you are using a Fix, Kraken or Keldan constant light, there are remote control options that will allow you to adjust the light intensity.
If you can't seem to get a light in the right location for a shot, try to inlist a dive buddy in holding the right location. If shooting backlit wide angle, a diver behind a sea-fan with a light for instance can work well. Remember that front and rear lighting together is also very effective. This technique was used in the shot below.