The world of non-commercial film and A-V

You must keep your camera dry. Keeping the camera away from the seawater is relatively simple - you put it in a waterproof housing and close the door. Closing the door is not that simple as it shuts onto a gasket of rubber called an O ring. You must ensure that the O ring seal is absolutely clean. A single hair or speck of dirt will result in the housing flooding, and you having to buy a new camera. Insurance is essential.

Housings range in price from a few hundred pounds to many thousands. They can be designed for just one camera or for a range. Cheaper housings will have access to only a few controls via push buttons or levers, for example: On/Off, Zoom In/Out, Record, Pause, and Focus. Expensive housings have access to more controls either by systems of levers or by buttons operating electronic controls. In particular, some housings allow adjustment of the camera's white balance and gain controls. Some allow viewing only through the viewfinder, others by the camera's display screen.

Some housings have just a single lens while others may accept supplementary "wet lenses" i.e. you can add them while under water, or may offer a range of primary lenses. Wide-angle primary lenses are amazingly expensive. Close-up lenses are less expensive but you may be able to fit a standard C/U lens onto your camera lens and still fit it into the housing. Underwater, refraction at the lens's surface makes objects appear to be larger and closer than they really are. A 35mm lens underwater is equivalent to a 50mm lens above water. Lenses are frequently defined by their angle of view (across a diagonal). 84°and 90° lenses are considered to be Wide Angle.

Spend a lot of time choosing your housing, understand its possibilities and its limitations. The housing and camera should ideally be chosen and bought at the same time so that you can decide upon and obtain those facilities that are important to you. Whatever you buy, you may still need to modify it so that it meets your exact needs.

My Amphibico housing with modifications.

The temperature of the water may limit your dive time and affect the operation of your camera. At most tropical locations the surface air will be warm and moist, the water will be warm. But even in warm waters, sudden drops in water temperature can occur at "thermoclines". The reduction in temperature cools not only the diver but also the air in the housing. If the housing is filled with warm, moist air, which is then suddenly cooled, the moisture will condense inside the housing; possibly on the lens, possibly on the inside of the camera! This problem can be avoided by filling the housing with cold, dry air (from the air conditioning system) before the start of the dive and additionally by placing a sachet of silica gel desiccant inside the housing just before closing the door. The main limitation of this approach is that the camera must be kept cool for the whole holiday, as a sudden exposure of the cool camera to the warm, moist air outside your air-conditioned cabin will also cause condensation within the camera. Overcome this problem by having two cameras. Another, smaller problem with thermoclines is that they cause a shimmering layer at the interface of the two water temperatures. This shimmering layer will appear as gross distortion on any footage.

Effect of shimmering - gross distortion.	Below the thermocline, shimmering gone.

© words and images, JohnFletcher

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