Underwater photography

In recent years, there have been rapid advances in the development of underwater cameras, television and video. The current interest in sport diving has led to the development of a wide variety of underwater camera equipment designed for easy use by scuba divers. Further impetus has come from the need of the oil and gas industry to inspect their underwater hardware. Photography is widely used by marine biologists to support other sampling methods. It can also be used as a recording tool on its own. For example, stereophotography, using two cameras mounted in a frame, provides three-dimensional images allowing size measurements to be taken. Repeat visits to marked areas can be made to record changes in species composition, growth rates and seasonal changes.

Diver-operated cameras

Underwater photography has become an increasingly important tool for diving marine scientists over the past 15 years or so. Diver-held underwater cameras fall into two main categories: standard 35mm land cameras and flashguns enclosed in pressure-proof housings; and amphibious, waterproof cameras with dedicated flash guns of which the Nikonas system is the most widely used (Figure 3.32). Both systems can be fitted with a variety of wide-angle and close-up lenses. Housed cameras tend to be bulky but have the inherent capabilities of any single lens reflex camera allowing automatic exposure and focusing. Several amphibious cameras now have automatic exposure capability with through-the-lens (TTL) metering but to date, only one, the Nikonas VI, has automatic focusing. The high price of this model puts it beyond the reach of many divers.

Figure 3.32 Nikonas V amphibious camera equipment; (a) camera with dedicated flashgun allowing TTL metering; (b) camera with close-up lens framer.

The main problems with underwater photography stem from the lack of available light. Except in very shallow depths, a flashgun is always necessary, both to provide enough light, and to restore colours at the red end of the spectrum (see page 138). Backscatter from particles in the water reflected by the flash makes distance photography difficult. This can be partially overcome by use of wide-angle lenses which allow a close approach to the subject whilst covering a reasonable area. A wide variety of books, videos and specialist courses on underwater photography are now available.

Underwater housings have also been developed for the lightweight, compact video cameras now available on the market. These are easy and cheap to use and are especially useful at deeper diving depths where diver time is limited. Underwater video is now being increasingly used in biological survey and monitoring work.

Remote cameras

Remote, automatically operating underwater cameras deployed on wires from research vessels have been in use since about the 1970s. Nowadays they are more often mounted on sledges, submersibles or on towed arrays of multi-instruments. They can also be mounted above baited traps. Modern cameras and lighting units provide high-resolution photographs. Cameras operating in the deep sea do not necessarily need a shutter due to the lack of light at such depths.

The camera systems described here are those most commonly in use today for studying the deep-sea bed.

Flat plan pictures of the sea-bed are taken using stereo cameras pointing straight down (Southward et al., 1976). The instrument package in its supporting frame is lowered from the ship until a trip-weight hanging beneath the apparatus touches bottom. This fires the electronic flash so that a photograph is taken, and the film is wound on. It also causes an acoustic signal to be transmitted to the ship. As soon as this is heard on the ship's hydrophone the apparatus is raised slightly above the sea-bed and then lowered again. As the weight touches bottom a further picture is taken, and the process is repeated for each photograph. Alternatively, either bottom or midwater cameras can be triggered by levers carrying bait, each photograph being taken at the instant an animal grasps the bait.

A camera can be mounted on a sledge and towed across the sea-bed by the ship. In this case the camera is usually obliquely mounted and programmed to take photographs at set intervals. It is often easier to identify small animals from oblique, rather than straight down pictures.

A recent exciting development is in free vehicle cameras that can be deployed on the sea-bed and left there, with no connection to the surface, for many months at a time. Their use in time-lapse photography at abyssal depths has been revolutionizing concepts of life on the deep-sea bed. The camera takes photographs at set intervals and other instruments record current speed and direction at the same times. The instrument package, including the camera, is recovered by sending an acoustic signal which releases it from its expendable

Bathysnap Design

Figure 3.33 'Bathysnap', a free-vehicle time-lapse camera system.

Reproduced from Lampitt and Burnham (1983), with permission from Elsevier Science Ltd.

Expendable base

Floatation spheres

Figure 3.33 'Bathysnap', a free-vehicle time-lapse camera system.

Reproduced from Lampitt and Burnham (1983), with permission from Elsevier Science Ltd.

ballast base. It then floats to the surface and can be tracked and retrieved by the research vessel. A system called 'Bathysnap' (Figure 3.33), developed in the UK by the Institute of Oceanographic Sciences (Lampitt and Burnham, 1983), has recently been used to follow seasonal changes in the amount of phytodetritus at abyssal seabed sites (Rice etal., 1994), especially in relation to the spring plankton bloom in the North Atlantic (see page 195).

These cameras can be used in combination with baited traps allowing photographs to be taken of otherwise motile and well-dispersed species. Giant amphipods and various fish have been photographed in this way.

The appearance of the sea-bed shown in photographs provides information about the nature of the sediment and the speed of movement of the bottom water. Organisms can be seen undisturbed in their natural environment, or their presence known from their tracks or burrows. Where creatures can be easily recognized, quantitative information from photography is probably more reliable than that obtained by grab samples.

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Responses

  • LUCAS
    How has underwater photography changed?
    9 years ago
  • Ashley
    What tools and instruments are used in underwater photographer?
    9 years ago

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