The realm of marine photography has advanced far beyond the amphibious cameras of old. Since Nikonos first pioneered the underwater camera technology in the 1960's, marine photography has joined the digital revolution. Nikonos began with an amphibious 35mm camera with a rugged aluminum body. These classic cameras are still in circulation today, due to superior optics and a basic design that is salvageable if flooded. Optics also pose one limitation to amphibious and many housed style cameras. Lenses cannot be changed underwater. Imagine this scene: a scuba diver with a macro setup is stalking nudibranchs on fan coral. A dark shadow passes overhead. Looking up, the avid u/w photographer stares into the belly of a 15 foot manta ray. Imagine the powerless awe as the once in a lifetime photo opportunity glides past into oblivion. For such reasons, many newer underwater cameras empower the diver to switch from macro to wide angle on the fly, even 100 feet underwater.
Underwater cameras are generally of two types. Either the camera itself is submersible, or a traditional camera is placed in a water tight and pressure proof housing for underwater use. Optics of amphibious cameras tend to have an edge in clarity. Light waves pass from water to air in a direct optical path from lens to film or digital receptor. Conversely, in a housed camera, light travels through the lens on the housing, into open air, then through the second lens of the camera inside. The multiple changes of medium has a higher risk of scattering light waves.
Even so, for the average user, the difference is negligible.
Another consideration for u/w photography, water absorbs the color spectrum as it is filtered with depth. By 30-40 feet underwater the remaining colors have blended to mostly green and brown hues. To restore life to photos from the bland boredom, any camera will need a strobe. This is true for any photographer shooting in water deeper than approximately 10 feet. Reduced visibility waters require a strobe even shallower. Basic underwater cameras place a strobe on the body of the camera. This effectively restores light, but also causes back scatter as suspended particles illuminate and reflect back to the camera eye. To reduce back scatter, strobes are extended away from the camera either by hand or with mounting brackets and arms. These external strobes use a marinized sync cord to synchronize the flash in time with shutter release. The unflitered light source means brilliant reds, oranges and purples on film where the eye saw only dull brown, maroon and black. The effect is particularly stunning in colorful tropical waters.
As technology has improved, circuitry has condensed. Excellent point and shoot style cameras with 8 megapixel resolution or better are now available at reasonable prices for recreational users. Check when shopping cameras for housing availability for that particular model. Some manufacturers such as Sea Life cameras design both the camera and housing. Sea Life is a branch of world renowned Steiner binoculars, and the highest caliber optic technology is engineered into these cameras. Advantages to cameras designed for U/W photography include special program modes for shooting u/w to optimize against color filtration at depth. Any good design should provide the user necessary access manipulate buttons underwater. Poor designs require opening the housing to switch modes or access menu controls. This proves problematic when troubleshooting or changing target subjects underwater.
An often overlooked characteristic for marine photography is the balance of a camera in water. The best housings are as close to neutral buoyancy as possible. Since enveloping a camera in essentially a box of air adds positive buoyancy, dense weight is necessary to add negative buoyancy for balance. The most successful designs typically achieve this by minimizing trapped air space in the design phase. The larger the air pocket, the more counter-weight needed. Some designs simply add weight externally to the mounting base. While this returns the camera to near neutral buoyancy, there is a drawback. The camera is always prone to the upright position, and is difficult to handle inverted or peering into coral heads. A well designed amphibious or housed camera should rest easily in hand at any inclination underwater.
So you've bought the camera, read the manual and now it's time to shoot. Some basic tips for beginners:
Shoot horizontally or angled upward. A common mistake is to shoot every photo looking down. The light reflection off the bottom dulls the background. Shoot upwards for blue horizon and natural lighting.
Be meticulous. Read the manual for sealing instructions. Digital cameras hate seawater- period! Don't flood it. Some manufacturers use O-Ring seals that require silicone, others advise sealing surfaces be dry. Either way, get in direct sunlight and inspect for fuzz, grit and hairs that compromise seals. Use only fingertips and lips when handling O-rings, as these parts of your body don't have hair to compromise a seal.
Take notes. A dive slate to record light meter readings and settings improve mistakes light years faster than dumb luck.
U/W photography is fun and absorbing. Just remember to check tank pressure often. Safe diving!