THE ART OF DIGITIZING GEOLOGICAL COLLECTIONS: A VIEW FROM THE TRENCHES

With a two-year Institute of Museum and Library Services (IMLS) grant, the Perkins Geology Museum at the University of Vermont has been archiving digital images of the Museum’s collections. The collections include fossils, rocks, minerals, maps, diagrams, 35mm slides, photographs, thin-sections, and sediment cores. An estimated 40,000 images will be produced and viewable on-line (http://perkinscatalog.uvm.edu).

Quality digital images must have sufficient spatial and color resolution to provide optimum visual information and be artistically composed to highlight geologic details. Geological features ranging from meters to microns are being captured with a variety of digitizing cameras and scanners. A SPOT Insight Camera (1600x1200 pixels) is the main workhorse used in this project.

We have experimented with many techniques in order to achieve quality results using this SPOT camera. Multiple views of specimens are obtained to give the viewer a sense of their three-dimensional character. These views include dorsal, ventral, left-hand, right-hand, anterior, posterior, and oblique. Modeling clay can be used to hold a specimen at different angles and thus increase the spatial value, shape, and contrast of the image. Due to the three-dimensional properties of most specimens, close attention to depth of field and aperture is required. The light source should emit natural light so the specimens’ color and contrast are natural and high. We use full spectrum 100-watt bulbs rather than halogen or fluorescent lights for a lower light intensity. Higher watt bulbs reflect too much light off the specimens. To reduce the light reflection off of a crystal face or a light colored specimen, the angle of the lights is changed and the intensity decreased. When fossils are digitized a blue background is used since they are predominately gray, while a black background is used for minerals to bring out the unique colors. A piece of glass is used as a shelf on a camera stand to eliminate shadows and raises the specimen high enough so that the background color source is never in focus. When a macro lens is used, the specimen is placed on a black cloth to eliminate reflections. Overall the images are pleasing and clear to the eye, and are successful in their purpose.