Page 356 - Green - Maritime Archaeology: A Technical Handbook. 2nd ed

Chapter 12: Artifact Photography 335
and clear way. As digital cameras are becoming more widely used for pho- tographic recording, archaeologists will need to be even more careful to properly record what is being photographed, because in the past both the negative sheets and the color slides generally had information about dates, places, and material recorded on them. With digital cameras the images are usually simply filed in folders with the minimal possibility for detailed infor- mation. However, many digital cameras have file naming conventions that record date and a sequential number. Unless one becomes highly organized, data is going to become lost. Like all computer systems getting an orga- nized filing structure is essential, this cannot be overemphasized with digital photography. One needs to place images in carefully thought out file or directory structures, possibly with a date (in year-month-day format: 20031224) to help order images chronologically and then a brief descrip- tion. Metadata, the information associated with the photographs need to be recorded too, possibly in a header word document at the top of the digital image directory. This sort of data: who took the pictures, what the subject was, etc, was, on conventional photographs written on the contact sheets, negative files or on the slide frame. It is too easy to forget all this in the enthusiasm of digital revolution and suddenly find you have no idea what the images are or where they came from.
B. SCALE POSITIONING
Every artifact photograph requires a scale in the view, however, if the scale is not meaningfully positioned, its inclusion in the photograph has only marginal value. In the case of an object with axial symmetry such as a pot or a cannon, the scale and the plane of the film are arranged so that they are both parallel. The camera is positioned in line with the center of the object and the scale is arranged so that it coincides with the outline of the object (Figure 12.5). It should be possible to use a photograph of this type to produce a scale drawing of the object. Remember that the scale is only correct in the plane perpendicular to the optical axis of the camera in which the scale lies (the scale plane). For this reason, the scale should be placed to coincide with the outline of the object. Thus, if the object is a cylinder, the height of the cylinder is only correct at the vertical edges or outline of the object in which the scale plane lies. The perspective effect of the pho- tograph gives a heightening of the cylinder toward the center, and mea- surements anywhere outside the scale plane will require a magnification factor to correct them to true scale.
Similarly, in the case of a flat object, the plane of the surface of the object must lie in the scale plane. A useful technique here is to place a small mirror