TECHNICAL ASPECTS OF PHOTO-DOCUMENTATION AND CAPTURING AESTHETIC GEOLOGICAL SUBJECTS IN THE FIELD

Photo-documentation and capturing the aesthetic features of geological subjects can be enhanced with attention to several basic rules of photographic technique. Major factors to be considered include lighting, color, and photographic composition.

Lighting of geological subjects for both documentation and aesthetic purposes includes the incident angle of sunlight (or other illumination source), brightness, and contrast. The angle of the light source is most important in how details on surfaces (e.g., exposed bedding planes, etching, sole marks) are captured. Brightness and contrast need to be adjusted to record pertinent details on film/digital file for photo-documentation. Brightness is typically adjusted through the combined reciprocal effect of aperture and exposure time, within the range of application of a particular film speed (or digital camera rating equivalence). The contrast between the lightest and darkest portions of the image is controlled by exposure settings and film type, and can be modified in post-processing through the dodging/burning method either in the darkroom or on the computer.

When color photography is employed, the purpose of attempting to capture “true” color or to represent the image with color enhancement should be established. A subject in the field has intrinsic color, which is modified by nature of the light illuminating it. Unless a physical sample of the subject is collected or a comparative reference (like a color chart) is used during the taking of the image, and the illuminating light can be recreated to compare the sample or reference to the image output, an interpretation will be required to estimate “true” color, irrespective of film type.

Photographic composition concerns the overall positioning of the elements in the image, including angle, distance, centering, and juxtaposition.

How lighting, color, and photographic composition can be best approached depends on the purpose and the final output of the image. The final output may be reflective media (paper, polyethylene), transparencies, and/or digital files. The final or maximum image/file size, and the technical quality requirements are key in determining the best method for obtaining the image.