Page 353 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

332 Maritime Archaeology: A Technical Handbook, Second Edition
outlines and details. It must again be emphasized that the artifact photo- graph serves a different purpose to the general photograph of an object, where the use of high key and shadowing helps to produce a dramatic and striking photograph. If color film is used, extreme caution is needed to ensure that the lights are correctly balanced for color, or that the film matches the type of lighting used.
There are four choices of illumination. Tungsten lights are the most common form of lighting; they are cheap and convenient to use, but suffer from a number of drawbacks. First, they are hot, which can be inconvenient when dealing with close-up photography or where the artifact can be damaged by heat. Second, the photoflood illumination can be rather local- ized, unless large reflectors are used to diffuse the light. This type of light- ing can be used with color film provided a tungsten-type film is used. It should be noted that daylight-type color film can be used with tungsten light using a filter (80 series). This is not recommended for critical work as there can be some distortion of the color balance. Tungsten-type color films (Type B) can be used in daylight with a filter (85 series).
Another illumination choice is fluorescent light. It is a cool, diffuse light, ideal for black and white work. This light creates soft shadows and a uniform lighting. One of its best applications is illuminating plans or draw- ings, where the extended light source gives an even illumination over the subject, and does not cause the hot spots or strong shadows that occur with tungsten light. Its main drawback is that it is very difficult to use with color film, because the exact correcting filter for a particular fluorescent tube is difficult to determine.
Flash is another lighting choice, but it is notoriously difficult to handle, particularly in object photography. This light source is intense and localized and, more importantly, it is almost impossible to predict the results because of the instantaneous nature of flash. In effect, one only sees the success or failure of a photograph in the printed result. This is unlike the previous two situations where one can adjust the illumination until satisfactory condi- tions are obtained. In some studio flash systems a tungsten light is included with the flash. This is used to illuminate the subject while the camera and lighting positions are changed so that some idea of the effect of the flash can be obtained. The intensity of the flash can be softened with umbrellas (a white painted umbrella into which the flashgun is fired). This can be one of the best lighting options, as it gives diffuse, high light levels allowing large depths of field without having to worry about camera shake or unwanted shadows. The flash systems with electronic control are quite useful, and it is possible to get a flash which is controlled from within the camera. In this case, the internal photocell measures the light reflected from the film plane and controls the flash duration accordingly. This is excellent for close-up work, where flash meter readings or calculations of correct exposure are