Page 352 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 12: Artifact Photography 331
Figure 12.3 Illustration showing the effect of contrast on a dark object, in this case the stern post timber form the Batavia. Although the timber is very black, the right-hand exposure is probably correct in reality, but it obscures the features. By lowering the contrast and lighten- ing the image, the features become more clear. (Courtesy of Patrick Baker and Jeremy Green, both of the Department of Maritime Archaeology, Western Australian Maritime Museum.)
If an incident light meter is unavailable, a neutral gray test card can be introduced into the field of view to obtain the correct exposure. The card is placed near the subject so that it receives the same incident light as the subject. The through-the-lens meter can then be used to determine the correct value. It is a good general rule to check both the incident (or gray scale) exposure reading and reflected light reading. If there is any discrep- ancy, one can be sure that there are surface reflection problems, and some thought will have to be given to the choice of exposure setting. When using a high magnification ratio (1 : 5 or greater) and a hand-held exposure meter, some account of the magnification formula is made to obtain the correct exposure.
C. ILLUMINATION
The lighting of an object is a complex and often difficult problem. Ade- quate light is required to illuminate the object and to produce good con- trast, while avoiding unnecessary shadows and reflections that can obscure