Look at the camera table of any dive boat and there are basically two types of cameras: viewfinder cameras, (typified by the Nikonos and Sea & Sea systems) and conventional single lens reflex (SLR) cameras housed in waterproof enclosures. While most have used or at least handled a viewfinder system, few divers are familiar with a SLR system

A SLR camera allows the photographer to look through the lens, thus you "see" what the camera "sees." This compares with a viewfinder system in which you look through a separate lens, thus you "see" the subject a bit differently than the camera does.

So who should buy a housed SLR system? Those who are interested in obtaining fish photographs are first on the list. The "normal" or macro lenses that are commonly used for photographing small to medium sized fish have a very shallow depth of field. With a SLR you look through the lens and can place the plane of sharp focus precisely where you want it. With a viewfinder system a focus tool (such as a wand or framer) is used to aid in focusing. While such a system works well for stationary subjects, fish are threatened by the jaw-like appearance of the framer. I am not saying that you cannot get good photographs with a viewfinder camera, but you will get more and better fish photos with a SLR.

Photographers who wish to have precise control over composition will also benefit from a SLR system. If you want a colorful invertebrate in the lower left hand corner of your photo, a sun burst in the upper right and a diver in between the SLR allows you to see exactly how the final image will appear on film when you trip the shutter. Composition in macro photos will also be improved by a SLR. How many viewfinder photographers have tried to get an upward angle on a nudibranch, and found that the desired composition requires the framer to be embedded in a piece of rock?

So you have decided to house your SLR. What should you look for? First not every housing fits your camera, you must get one that has controls in the right places. Not all manufactures offer the same controls/features. It pays to do a little homework and figure out ahead of time what features you want or need. If you are new to this talking to a shop that specializes in underwater photography helps.

If you have the option, buy a camera with a sport or action finder. Examples of these kinds of cameras include the Nikon F series cameras or the older Canon F-1. These view finders are about the same size as a 35mm slide and allow a clear view of the entire viewfinder through the camera housing and face mask. Cameras that do not have sport finders have add-on magnifying lens that do much the same thing, but the view is not as good as with a sport finder.

Another feature to look for is an electronic shutter release. Most housings have a mechanical stutter trigger that penetrates the housing and works the shutter button on the camera. In California most divers use thick gloves and it is all to easy to trip the shutter when you only wanted to engage the autofocus or light meter. An electronic shutter triggers the shutter via a switch on the camera housing and a wire to the electronics in the camera. This allow precise engagement of autofocus, etc. without tripping the shutter by accident.

One last tip. All too often I see frustrated photographers using the focus knob or auto focus to track a moving subject. Try prefocusing the camera at the distance you want to photograph the subject, and focus by moving the camera rather than the focus control. Try it, it allows for precise control over focus and composition.

Bruce Watkins is a frequent contributor to California Diving News, lecturer and author of the book A Diver's Guide to Monterey County.