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7.2.7 Diving From Small Boats

Although most surface based umbilical diving is conducted from larger vessels or fixed platforms, the system may be readily adapted to small boat operations. Generally, when working from small boats, i.e. 16 to 30 feet, a bank of high-pressure cylinders is used to supply air, thus enabling the group to operate without the excessive noise of an air compressor's motor during diving operations. This enhances communications considerably and provides more pleasant conditions for surface. personnel. The number and size of cylinders used will, of course, depend on the size of the boat. For small boats, two or more sets of standard twincylinder scuba may be connected by a specially constructed manifold which is, in turn, connected to a high-pressure reduction regulator or small gas control panel. The umbilical is then connected to the pressure side of the pressure reduction unit. In larger boats air may be carried in a series of 240 or 300 cubic foot high-pressure cylinders. Regardless of the cylinder configuration used, all cylinders must be properly secured and the valves, manifold, and regulator protected to prevent damage to equipment and prevent personal injury. The umbilical may be coiled on top of the air cylinders or in the bottom of the boat. The communicator is generally placed on a seat or platform for the convenience of the tender. Communications equipment must be protected from weather and spray.

Since small boats are generally used for only shallow water work, the umbilical is normally only 100 to 150 feet in length. Longer umbilicals are bulky and cumbersome in small boats. It is generally wise to limit diving depths to less than 100 feet when working from a small boat and the boat may be readily moved to facilitate the lateral movements of the diver. Otherwise, normal surface supplied diving procedures and lightweight equipment are recommended.

The small boat umbilical diving team will normally consist of a diver, tender and standby diver. If properly qualified, all personnel may alternate tasks for maximum operational efficiency. The standby diver may be equipped with a second umbilical and mask or, as frequently the case, equipped with scuba. He should be completely dressed and capable of donning his scuba and entering the water in less than a minute. If he is using scuba, it is wise for him to be fitted with a

quick-release lifeline (readily releasable in the event of entanglement). Some use a heavy duty communication cable as a lifeline enabling maintenance of hardwire communication between the standby diver and tender. This line is also constructed so it may be readily released in event of entanglement. Many divers consider the use of a high pressure cylinder air supply system safer and more dependable than systems incorporating a small compressor and volume or receiver tank. Some desire that a small volume tank be incorporated into the system so the diver will have air for surfacing in the event of a malfunction, others find this unnecessary. Most agree that the diver should carry a small self-contained emergency scuba for use in event of primary system failure. This is mandatory when working around obstructions where entanglement is possible or inside submerged natural or man-made

structures.

"Live Boating" is a relatively common practice for surveying with an umbilical system. In this situation, the boat will follow the diver as he swims ahead or the diver will be slowly towed behind the boat on a weighted line or "tow-plane." The speed of the boat must be slow (0.5-1.5 k), and carefully controlled, depending on the experience of the divers. Precautions must be taken to avoid fouling the diver's umbilical in the propeller. Generally, the propeller is covered by a specially constructed wire or metal rod cage, and the umbilical is "buoyed" so it floats clear of the stern. When live boating from a large vessel, it may be desirable to tow a small boat behind the vessel and tend the towed diver from the smaller boat. The tender must be especially cautious to keep the umbilical clear and positive communications must be maintained between the bridge on the large vessel and the tender. The bridge may also wish to incorporate a system that allows monitoring the divers communication. If diver to surface communication is interrupted for any reason, the engines must be stopped.

7.3 UNDERWATER PHOTOGRAPHY

NOTE:

No Attempt to Cover the Details of Underwater Photography Has Been Made in This Manual. The Reader Is Referred to Appendices A and B for Publications Giving More Exhaustive Treatments.

Scientific underwater photography divides itself into two categories: photography with a diver-held camera and with a camera operated remotely. In the first category, the diver and his photographic instruments are an integral package. In the second category, the photographer need not even wet his feet. Diving skill and experience allow the photographer a degree of mobility and precise positioning in relation to the subject that cannot be achieved remotely. On the other hand, the remote camera disturbs shy subjects less than the threatening bulk of a diver, and functions at depths the diver cannot reach or can only reach with complex surface

support.

Aside from diving skill, scientific recording under water poses its own set of problems. There is less room for error than in photography on land. Objectives must be extremely clear and the scientist must carefully choose his equipment to record those objectives with minimal distortion and maximum information. Too often, the limited equipment from a laboratory's diving locker dictates the method of approach to a job. With ingenuity and commercially available equipment, the scientist need not be so restrained.

7.3.1 Still Photography

7.3.1.1 Lenses and Housings

Consider the 35 mm camera as a basic platforma starting point that must be modified for task requirements. Two approaches are possible in the selection of the camera: an instrument specifically designed to operate in the sea with watertight sealing, such as the Nikonos (Figure 7-10), or a camera designed for air use housed in a water-tight casing (Figure 7-11). The first is extremely portable and easy to use. The second is more versatile in lending itself to modification to fit specific requirements beyond the capabilities of the Nikonos.

Choice of lens for either the free or housed camera is dictated by the required field of view and by the clarity of water. Since the distance from camera to subject must be short compared to air (Figure 1-5), the photographer requiring a broad expanse must use a lens with a wide degree of coverage. A rule of thumb is that photographic visibility is only about one-third of eye visibility, so the wide angle becomes an important tool even in clear

water.

Wide angle lenses, when used under water,

create their own optical problems. When used through a plane parallel port facing the water, several objectionable qualities are evident in the resulting photograph. Distortion and lack of sharpness in the periphery, color aberrations, and narrowing of the angle of view, all rob the under water photo of image quality it would have if the same focal length lens were used in air. The optical characteristics of water are such that wide angle lenses must be corrected for water use. This is possible by designing water correction into the lens formula (expensive but effective), or using corrective ports of varying sophistication and price in front of wide angle lenses designed for use in air. A plexiglass dome (part of a hemisphere), coupled with provision for closer focusing of the lens than is necessary in air, solves the problem with the least cost. Several commercial underwater housings have corrective capabilities.

When close-up photography of small objects is required the plane parallel port coupled with lenses of longer focal length, becomes a viable tool. Desirable requisites for this type of photography include ground glass focusing for precise framing, whisker sharpness of the image, a lens which can focus closely on the object, and at least one light source coupled to the camera. The plane parallel port that is so destructive to a wide angle image becomes an aid, when using a longer lens, enhancing the telephoto effect without noticeable destruction of the sharpness or color quality of the picture.

The "off-the-shelf" underwater cameras or simpler housings for air cameras, if unmodified, allow the scientist to work only in the middle distance range. Although this permits the collection of much useful data, invariably distant and closeup shots will be necessary. A well-designed and engineered housing is heavier and bulkier, and requires more maintenance than an in-water camera. It is, however, a more flexible instrument in the range of wide angle and closeup work than the in-water instrument. An in-water camera does not have ground glass focusing. Its extreme wide angle lenses are expensive and limited to a few focal lengths. Its provision for closeup modification demands that the diver work within rigid distances between camera and subject and shoot blindly, relying on mechanical extensions from the lens to determine the distance. Few small fish will tolerate the close proximity of a metal framing rod extending into their immediate territory. At the very least, the rod will induce by its presence unnatural behavior in fish and other

Nikonos Underwater Camera

With Electronic Flash and Wide Angle Lens

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Photo: Lee Somers

Photo US Navy

marine life. With ground glass focusing of the housed camera, this problem does not exist. Longer lenses allow the photographer to work far enough from his subject so as not to interfere with behavior, much less frighten away his subject.

7.3.1.2 Light and Color

Light and color go hand-in-hand under water (Figure 7-12). Color films balanced for either daylight or tungsten light are relatively blind to the color subtleties which our eye can distinguish within the blue or green spectra of water. In shallow depths, filtration offers some compensation. A color correction filter (Table 7-2) over a lens will break the blue up enough to restore a certain amount of color that the diver's eye sees and the unfiltered film cannot. The color red however disappears at about 40 feet of water and no filtration can restore it. Artificial light not only illuminates situations too dim for film exposure, but also brings out color

rent in the subject. To be effective, artificial

light in water must be used much closer to the subject than in air. The closer and more powerful the light, the more it will compensate for the excessive blue of seawater. By varying distance and power, different balances can be obtained. A waterblue background with a slight hint of color can be accomplished as easily as brilliantly illuminating the subject, completely obliterating the water quality.

Several good electronic flash units are made for underwater use. Some offer an under water wide beam for use with wide angle lenses; others a narrow beam which penetrates the water column more effectively (Table 7-3). Small electronic flash units designed for air use can be housed effectively for water use in simple plexiglass containers. Connectors are available for unplugging the units under water without danger.

Tests should be made to establish correct exposures with any unit with various speed films prior to the principal assignment (Table 7-4). Guide numbers, a quick and easy method of determining exposures in air, are virtually useless in water.

Flash bulbs can be used effectively under water in units designed for water work (Table 7-5); clear bulbs for distance and blue bulbs for closeups. The longer water column effectively filters the clear bulbs with blue so that the light balances for the daylight film. Beware of bulb implosion at great depths- nasty cuts on hands have occurred when changing bulbs in deep water.

Incandescent light powered by battery or by a topside generator (a must for motion picture work) has application in still photography also. It does not penetrate the water as well however, and is clumsier to use than electronic or bulb flash.

Lighting arms and brackets, or extension cords for off-camera light allow for a variety of positioning. Care must be taken not to place a light on the

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