Basic Underwater Photography: Lenses

Underwater photography has several basic differences from surface photography. The light level starts at least two f/stops less than above water, and most colors are filtered out by the water. The addition of flash restores these colors, but even the brightest flash has a maximum range of about five feet from the camera. The basic theory is to eliminate the water from your photograph because water degrades the image. This is done by using wide angle lenses. A lens in the 15 to 20mm range allows photographing a large image or people less than three feet from the camera. A normal 50mm lens would require you to be much farther from the subject to obtain the same image. Lenses in the 35 to 80mm range are limited mostly to taking fish pictures. Lenses in the 24 to 28mm range are considered "normal" underwater, providing reasonable coverage for an average scene. This range is wide enough for people portraits, but not too wide for fish photography. Macro photography is a fascinating frontier underwater. A macro lens is usually in the 50 to 105mm range, will have the ability to capture an image actual size on the film, and will focus to within a few inches of the lens. There are almost unlimited opportunities for macro photography underwater. A macro lens can take both normal and extreme close-up pictures. This one lens can photograph a shark chewing up your buddy, and also photograph the pieces. Multiple focal length or zoom lenses have become very prevalent and prove quite satisfactory underwater. Technically, these lenses may not be as sharp as a fixed focal length lens, but their quality today will satisfy all but the most discriminating analysis. Zoom lenses usually will not focus close enough to provide full range operation behind any dome without adding a +4 diopter close-up lens. This close-up lens looks like a filter and is available from most camera stores.