The definition of “photography,” in the Merriam-Webster dictionary, is “the art or process of producing images by the action of radiant energy and especially light on a sensitive surface (such as film or an optical sensor).” As underwater photographers, it is very important for us to consider the quantity, color, quality and direction of the light as it passes through water.
Above photograph: Combining ambient and strobe light creates breathtaking images.
Photographs © Larry Cohen and Olga Torrey
Quantity and Color
Underwater light is very different than light on the surface. Much of the ambient light reflects off the water’s surface, reducing the quantity of light that penetrates the surface. Water also absorbs different wavelengths of light, creating a color cast. Red and other warm colors are absorbed first, leaving warm-in-temperature ocean water to have a blue color cast. Cold, nutrient-rich ocean water and many bodies of fresh water contain large numbers of phytoplankton, which contains chlorophyll. This causes the water to have a green color cast.
There are several ways to correct this color cast. Bringing a white light underwater and getting it close to the subject is very effective. This also increases the quantity of light. The underwater image producer can use LED continuous lights for stills and video. Strobes (flash) can be used for stills only.
The use of strobes allows the underwater photographer to have more creative control when capturing stills. Strobe distance, power, and the camera’s aperture control the strobe’s exposure. The camera’s aperture and shutter speed controls the ambient light exposure. By keeping the aperture consistent and changing the strobe power for the subject’s exposure, and changing the shutter speed to adjust the ambient light background exposure, you can control the look of the image.
Use a fast shutter speed to darken the background. This can be effective when shooting light subjects. Using a slow shutter speed will create a light background. In open water, this can create a pleasing blue or green background. Using a strobe with a power dial will allow the image-maker to adjust the subject’s exposure, regardless of strobe-to-subject distance. Strobes with this feature include the Sea & Sea YS-D2J, Sea & Sea YS-01, Ikelite DS161, Ikelite DS160 and Ikelite DS51.
Even water that looks clear has particles in it, and water is denser than air. For this reason, getting close to the underwater subject is very important. Water will diminish image color, contrast, and sharpness. The farther away from the subject you are, the less effective your strobes will be, so it is important to use wide-angle or macro lenses and for your strobes to have a wide beam angle. It is best to use strobes with a beam angle of 100 degrees or wider. Adding a diffuser to the strobes provides a soft light.
Using two strobes does add task loading, but, getting even lighting is easier. You can also set the two strobes at different power settings to create light ratios just like one does in the studio. Arms to hold and position the strobes are important because it is best to use side lighting. This will prevent lighting up the particles in the water and will create texture in the subjects.
The strobes must fire when the shutter opens. This can be accomplished two ways, depending on your camera, housing, and strobes. Many housings have a waterproof bulkhead. On the inside of the housing there is a connector that goes into the camera’s hot shoe. On the outside of the housing there is a connection point for a sync cord that is sealed with an O-ring. The strobe has a connection point for the sync cord that is also sealed with an O-ring. Some housings have two bulkheads and others require a dual sync cord to use two strobes. The problem with this system is that you have more possible failure points that can cause flooding.
The other system uses the camera’s built-in flash and the strobe’s slave trigger. Fiber optic cables are used to move the light from the camera’s built-in flash to the strobe’s slave trigger. Make sure you set the camera flash to forced flash mode so the flash will fire even in bright light. Many housings have dual fiber optic cable ports to use two strobes. The cables can be plugged in or removed underwater. Flooding from the strobe connection is not possible. The camera’s built-in flash should only be used to fire external strobes. The camera’s flash is close to the camera’s lens and will light up all the particles in the water. This will cause a snow-like effect called backscatter.
Quality and Direction
Paying attention to the quality and direction of the ambient light and combining it with the strobe light can produce extraordinary images. In open water, it is possible to get light streaming in and lighting up the particles in the water, creating beams.
Between 11:00 a.m. and 2:00 p.m. is the best time to shoot. More light will travel through the water and not bounce off the surface. To get color into the background, besides using a slower shutter speed, it is a good idea to shoot upward, toward the surface. This is also a better perspective for most subjects.
Back-lighting the subject with the sun can create breathtaking images. You don’t want to overexpose the background, so in this case, you will need a faster shutter speed and will need to stop-down the aperture. The center of the sun can be too bright. Placing the subject in the center of the sun will attenuate the brightness in the center and will create a halo around the subject. The subject will be back-lit, so the strobe power will need to be turned up to expose the subject properly. You can also turn off the strobes to create a silhouetted image.
In a partial overhead environment, such as a cavern, the ambient light can cause breathtaking patterns of light and shadow. In this situation, the photographer should expose for the ambient light and use strobes on low power to fill in shadows and highlight the subject. Using a model will add interest to the light show. It is important to have a continuous light for safety. Mounting this light above the lens port will help the camera focus in low light. Using a focus light with an instant-off feature will prevent the focus light from affecting the image.
When photographing the interior of a shipwreck, use your strobes to light up the inside of the wreck. Use the shutter speed to expose for the light coming in the windows and doorways.
Models add a human element to cave photos. However, there is no ambient light in caves, so, to separate the model from the background and to create dimension, it is good to use a backlight. A third strobe can be mounted on the diver’s back, aimed toward the background. Ikelite strobes work best for this purpose. The Ikelite Optical Slave Converter needs to be in front of the model, and when the strobes on the housing fire, the Ikelite Optical Slave Converter will fire the backlight strobe. Strobes can also be placed around the cave, out of sight. The Ikelite 15' Extension Cord for Sync Cords can be used to bring the Ikelite Optical Slave Converter into line of sight of the strobes on the housing.
Special training is necessary to dive an overhead environment safely. No photo is worth dying for. Cave diving is safe when you follow the rules. This includes always having a continuous line to open water, and always carry a primary and two back-up lights. It is important to be comfortable and have experience in the environment before attempting to create images.
Taking the time to learn safe diving procedures and getting the experience to create underwater images is very rewarding. Well-lit underwater photos will WOW both your dive buddies and non-diving friends.
For more wildlife-related news and tips, be sure to check out the rest of Wildlife Week on B&H Explora!