Using LED lights underwater requires you change your thinking about exposure, focus, and shutter speeds. Digital photography underwater is simplified by using LED lights, as they need very little adjustment. Your biggest concern will be controlling the motion of the camera system while shooting, especially when photographing macro. The good news is that once you have mastered shooting macro with LED lights, wide angle and general photography becomes even easier.
You need to remember that you are now using available light to expose your images, so the key to success is the shutter speed you select. Unlike flash photography using manual exposure, you should be using the shutterspeed exposure mode most of the time with LED lights. After two years of field-testing, we have found that most underwater photographers can take macro images at 1/250 second in shutter speed mode and get excellent images.
You might be concerned that this shutter speed might result in the camera’s aperture to be wider than you normally use. To get good exposures and retain smaller apertures, you will want to move the lights in close to your subject. This minimizes backscatter because you no longer light the water column between the camera and subject. Another solution is to bump up the ISO. Most SLRs and high-end point-and-shoot cameras can shoot at ISO 800 with virtually no loss in image quality.
If you are having trouble getting a sharp image, try using the motor drive setting. This will allow you to shoot bursts of 3 to 7 images at a time. When you first press down on the shutter, the first image might have a small amount of blur as you steady yourself, and the last image may have the same as you release the shutter. The middle images will be the sharpest. We find that using a monopod or flexible tripod on the bottom of the housing helps with macro photography. Just make there is ample dead zones for the legs to rest.
It will take some practice holding your system steady, but the results will be well worth it. You don’t have to worry anymore about balancing foreground and background exposures that you did with flash. Just find a great subject, hold the camera steady, and start shooting. You’ll probably never go back to using flash.