Having talked about what the strobe does for you and the things that you need to think about to use them effectively, it’s time to consider the variety of ways we can use the strobes to enhance our underwater pictures.
The first thing to understand is a formula. That is that Total light equals the sum of Vertical light and Horizontal light. This diagram illustrates the concept. We can produce infinite variations of the picture by changing the amount of light from each source being used in an image.
As we are scuba diving, we adjust the amount of vertical light in the picture, so we will be changing the color of the background. We can take the background from black, where we allow no vertical light in, to a light blue where we add a lot of ambient light. This is probably a good place to start to compose our picture. Start by turning your strobes off and take a sequence of photographs varying the aperture with a shutter speed of 1/125th until you get the background color you are looking for. Point the camera, with the sun at your back into the blue water. Quite frequently, if you are scuba diving in the tropical waters of Key Largo, a good place to finish will be about f8 at 1/125th. at an ISO of 200. Obviously, less light will make the background darker, and more light, lighter. Once you have a background color to your liking, turn on one of the strobes and point it at your subject. Start on low power on the strobe and take a photograph. Review the result in the LCD screen and adjust the strobe power accordingly, increasing or decreasing the power. You can then turn on the second strobe to fill in any areas you think could do with some extra light.
In this picture of a Nassau Grouper, the shutter speed was 1/200th of a second with a small aperture and the strobe power was on high. This eliminated the vertical (ambient) light and made the backgound dark to avoid lighting a distracting background.
By contrast, this picture of a scuba diver on Molasses reef used a slower shutter speed of 1/125th with an aperture of F9 to allow more of the background light in to show the divers in the distance and give an idea of the size of the reef. The power of the strobe was increased until the lighting on the Atlantic Spadefish highlighted them just enough.
This picture of Divemaster Nick scuba diving on one of his rare days off used a slow shutter speed of 1/60th of a second combined with a large exposure of f5.6 to lighten the water on what was a fairly dark day. When you use a slower shutter speed on a moving object with a strobe, there isn’t much risk of motion blur because the strobe, which is lighting the foreground object is only typically illuminated for 1/1000th of a second, effectively freezing any motion.
This close up of a butterfly fish taken on Snapper ledge, was again taken with a fast shutter speed and small aperture to avoid lighting the brain coral in the background. It was taken using only a single flash to create an interesting shadow and provide some depth into what would otherwise be a “flat” photograph.
Remember that the most important point about using strobes is to use them to balance the horizontal and vertical light. We also use it to bring out the hidden color of underwater life. These two photographs of the Spanish Anchor on Molasses reef illustrate the point. The photo on the left was taken using only vertical light. The one on the right balances the horizontal and vertical light to get a nice blue background and uses the horizontal light to bring out the hidden color.
It also shows how important it is to follow the golden rule of Underwater Photography – While you are scuba diving and taking photographs, get close to the subject and when you think you’re close enough – get closer!
Happy shooting to all you Underwater Photographers out there. Keep diving, and keep shooting, as the best way to improve your abilities with a camera is experience, especially in the particularly demanding environment of salt water. And heck, it’s a great excuse to do more scuba diving in Key Largo after all!
Instructor Dave Jefferiss
For those who want to continue to learn about Underwater Photography, here is information on our “Digital underwater Photography Specialty Course”. (And it’s taught by Instructor Dave himself!)