Most underwater exploration takes place during the day, in open water. The underwater photographer can create three-dimensional-looking images by carefully balancing the ambient light of the background with the artificial light that is used to illuminate the subject. The only time the underwater explorer will be in total darkness is on night dives or in an “overhead” environment such as a shipwreck or cave.
During night dives, you are in open water; even new divers enjoy this experience. Divers should still carry a primary light source and two backups. In case of an emergency, the diver could still go directly to the surface, which may not be the case in overhead, enclosed environments. Open water night dives allow for a simple dive-and-bailout plan.
If you are going to do photography in an overhead environment, though, remember that safety always comes first, imaging second. Cave diving and wreck penetration are real specialties. In an emergency, you CANNOT go directly to the surface. First, you have to reach open water, in order to surface. For this reason you need special gear, rigging and training. Diving in overhead environments must be taken seriously. It is very important for you to be comfortable in a cave or wreck before bringing in your camera rig. Also make sure you have extensive photo experience in open water before you wander into a cave or a wreck with your camera. Know how to operate your gear with your eyes closed; remember, you might be working in total darkness. It is way too easy to forget the rules while concentrating on creating an image. Ignoring the rules of overhead-environment diving could create circumstances and consequences that could really ruin the rest of your life.
Nevertheless, cave and other overhead environment training has great rewards. You will learn to be a better diver in all situations. Entering a cave or shipwreck really is going where few humans have gone before. Being inside some caves feels like you have left the planet Earth and you are in a remarkable other world. The only thing more exciting than being there is returning with stunning images of these remarkable places.
As far as lighting for photography, there aren't any walls from which to bounce light, so it’s pointless to try and light up the background. During night dives, it is best to use one or two flashes to light up your subject and let your background go black. Since there isn't any available light, you may as well use a fast shutter speed to stop movement and reduce camera shake. Use side lighting to bring out texture and to separate your subject from the dark background. Why bother with all this? There is some really interesting marine life active at night. This includes some very small creatures. Shooting macro and planning for animal-behavior images can be rewarding and worth the effort.
Once you have full cave certification, 50 cave dives and 40 dives inside your favorite wreck, it will be time to take some photos. First, you need to produce sharp images. Modern cameras allow photographers to be lazy and dependent on autofocus. These systems really are very good, but require some light and subject contrast in order to work. Inside a cave or shipwreck, however, there is no light. Therefore, many cave photographers still use manual zone focus techniques. To do this, you need to preset the lens and use depth of field in order to keep the image sharp, within a certain distance range. Underwater, you’re using ultra-wide-angle lenses anyway, and they have a deep depth-of-field range. Also, you’ll want to work as closely to your subject as possible, so you don't have to hold focus beyond two feet or so.
Most modern lenses no longer have a depth-of-field scale. Instead, you can use this online Depth-of-Field Table, which is very helpful for figuring out pre-focus settings (go to http://www.dofmaster.com/doftable.html). For example, if you are using one of many ultra-wide-angle lenses, you would first set the lens to the widest focal length, the focus to one foot and the aperture to f/8. Use tape to prevent these settings from slipping. With these settings, your image will be sharp from approximately six inches to somewhere between three and four feet. All you have to do is approach the subject and push the shutter release when you are within range.
Another technique you can try is to use a strong focus light to allow the autofocus to work. You can have a team member hold a primary light on your subject in order for your camera to focus. You can also attach a strong back-up light to your camera rig, such as lights manufactured by Sartek, Diverite, Fantasea, Intova and Solus. Remember to set your shutter speed so the focus light will not affect your image. Since you are shooting in the absence of available light, a slow shutter speed won’t help you anyway.
When you first get started in cave photography, you will be more successful in the cavern zone. The cavern zone is the area of the cave where there is still natural light from outside. First of all, such a dive is less demanding. Next, you can use the ambient light to your advantage. You could use one or two arm-mounted flashes to light your subject. Then use the ambient light for the background just like you do in open water. As with most underwater photography, you want to have your camera set on manual exposure control. You should be in the cave area with the open water behind your subject. With all underwater photography, use the widest lens possible and get as close to your subject as you can. Never be more than two feet away from your subject. The closer you are, the better your images are going to be.
Set your shutter speed for the ambient light in the open-water area. Aim your flash at your subject and control flash exposure with your f-stop or power control. Remember, changing your shutter speed will affect your ambient light exposure (background). Changing your aperture will affect your ambient light and flash exposure (background and subject). Changing the power of your flash will only affect your subject. That is why flash with power-control dials are the most versatile for all underwater photography.
Shooting in the cavern zone should offer the opportunity for interesting images. You can capture really eye-catching patterns in the background. Entering a wreck and staying close to the entrance, you can use the same techniques. This will keep both the dive plan and the photography simple, and be much safer than a deep penetration.
Once you enter the cave or turn away from the cavern zone, you are in a completely black environment. You need to bring all your lighting along. Basically, it is akin to lighting a room the way an architectural photographer does in a house or office building. This kind of photography is difficult enough, but now you have the extra challenge of total darkness—and being underwater!
In order to create dimension and show the cave or wreck interior you have to add a backlight. You are trying to create the same affect you'd use ambient light for in open water, but now you have to bring the light with you. Many models of underwater flash that are capable of accepting a long extension cord work well for the backlight. This will allow you to position the external slave trigger on your model so that it will fire when it detects the light from the flash.
Use a bungee cord to attach the flash to the model's air tanks. Don't forget the right sync cords and connectors! The flash should be pointed toward the diver's fins. It's best to fit in a wedge so the flash is easier to position. Run the slave to the front of the diver and attach it to a D-Ring. The Ikelite manual controller is very good for this purpose. Since the controller allows you to change the flash power remotely, you don't have to swim behind the subject to make any adjustments.
Have the diver face you, with the attached flash facing away from the camera toward the back of the inside space. When the flashes on your camera rig fire, the slave will trigger the backlight. It is important that the backlight does not burn out the background. Depending on how far away the back wall is, you might not need a lot of power, but you do need a wide soft beam of light for a more natural look. Doing this adds a three-dimensional feel to the photograph and allows you to see detail in the background. Most cave photographs are better with a diver in the photo, to show scale. Your model diver should have proper equipment rigging for the environment in which you are shooting. The model should also be carrying a primary light. You could use your subject's light to create an interesting composition element in your photograph. You can follow the same technique inside a wreck, but don't forget to also create still-life images of the ship's machinery and other artifacts.
This is very technical photography and requires patience, communication and planning with your subject and your other team members. One of the advantages of shooting with digital gear is being able to see the results instantly so you can make on-the-fly adjustments. So take your camera, a gaggle of flashes and go jump into a flooded hole in the ground (once you have certification, for sure)! Experiment, have fun and above all, dive safely!
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