There are no underwater camcorders; but sealed housings are available for a variety, but by no means all, of the existing models. Ewa-marine flexible video housings can be used to a depth of 10m, and so are suitable for swimmers, snorkellers, and shallow-working divers. For deeper sport and professional diving, pressure resistant (hard) housings are available from numerous manufacturers (see products section, video). Some systems allow the camera to be used with a wide-angle adapter, and this helps to offset the problem of poor underwater visibility by reducing the lens to subject distance. Underwater colour correction filters can be accommodated by most housings, and these help to reduce the blue colour cast when working at moderate depths.
An underwater video light improves results considerably, and is essential in situations in which natural light is insufficient. To qualify as a video light, a light source must provide even illumination (freedom from hot-spots), and should have a reasonably high colour temperature (at least 3200K), which means that ordinary underwater torches are not good enough. Video lights are available from various manufacturers, and are usually powered by heavy Ni-Cd or Lead-acid batteries. Since the power source must be carried by the diver, burn times for tungsten filament lamps are necessarily limited (rarely more than 1 hour, and often considerably less). High efficiency HID or LED lamps use about 20% of the power of an equivalent tungsten lamp and are to be preferred.
For motion picture photography, a video light should preferably be fixed rigidly to the camera housing by means of a lighting support arm. For close-range working, a video lamp may be mounted directly above the housing. In this case, the lamp may be attached to a standard accessory shoe (if provided). For medium-range working, the lamp should be further away from the camera lens, and a longer articulated (jointed) arm is to be preferred. Arms with 1" diameter ball joints can support lights weighing up to about 2-3kg in air. The Ikelite 1.25" ball-joint system can support in excess of 3Kg in air. Other arms, particularly segmented arms, will droop when holding heavy lights in air, but will work acceptably underwater if not excessively loaded.
Last update: 07:19 AM Wednesday, May 21, 2008