Page 243 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

222 Maritime Archaeology: A Technical Handbook, Second Edition
Figure 8.1 The standard Nikonos underwater camera range. (Courtesy of Brian Richards, Department of Maritime Archaeology, Western Australian Maritime Museum.)
B. FLASH AND ARTIFICIAL LIGHT
Various forms of supplementary lighting are available for underwater work. There are two basic types: electronic flash (or strobe) and incandes- cent lights. In most cases, the flash is more effective as it can produce a very strong light with far less bulk than the strobe lights. Its main disadvantage lies in the fact that one cannot see what the effect will be until the film is processed. More experimentation is possible with lights. In some cases the latest electronic flash has a small light that can be used so that the photog- rapher has some idea of the effects of the flash (shadows and coverage) before it is used. Additionally, the latest Nikonos cameras have flash attach- ments that have automatic through-lens control of the flash, which greatly simplifies the system. It should always be remembered that the capacity to reason is diminished when one’s head is under water. The deeper the dive the less rational one becomes. So anything that reduces the need to think under water is helpful (see Section V.A). In addition experiments have been made using flash in turbid water to improve the quality of the image. In turbid water the main problem with flash is backscatter, where the flash illu- minates small particles in the water between the camera and the subject. When the flash is reasonably close to the camera this can cause real prob- lems. By mounting the flash on a long arm and positioning it well above the camera and subject, the backscatter problems can be reduced. If the flash is far enough above the scene, the flash acts as a wide diffuse light source