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Geological Photography - History of, Photography in the Field, Photography in the Laboratory

light camera lens rock

ANTHONY H. COOPER
British Geological Survey

Geological photography records the rocks, deposits, and processes that characterize the earth’s crust and landscape. It includes photomicrography and photomacrography as well as the photography of specimens including rocks, fossils, and minerals on location, aerial photography, and remote sensing. It includes the photography of natural rock exposures, landscapes, caves, mines, quarries, and the recording of geological processes such as volcanism, landslides, and erosion. The dividing line between photography and digital imaging in geology is blurred, with computer-dependent techniques like multispectral scanning, imaging spectrometers, 3D tomography, and image enhancement providing powerful visualization and recording tools for rocks, minerals, and fossils.

History of Geological Photography

Geological photography goes back almost to the start of photography itself. Some of the earliest geological photographs were landscape pictures taken by Timothy H. O’Sullivan (1842–1884) during American frontier expeditions in the 1860s and 70s. In England, Victorian photographers and keen geologists such as William Jerome Harrison (1845–1908) and Godfrey Bingley (1842–1927) used the then new medium to record quarries and exposures, with Harrison publishing the first geological book illustrated with photographs in 1877. From 1885 onward, photography began to replace engraving as the main recording instrument for geological monochrome illustrations in books, and geological surveys began their photographic collections.

Photography in the Field

Camera equipment for field use has to be lightweight, easy to use, and capable of returning results suitable for lectures and publication. A light, 35mm SLR camera (or a compact camera) with a 28-70mm zoom lens that has a close focusing facility is ideal. Alternatively, a small water-resistant 5-8 megapixel digital camera with a spare battery and large amount of memory makes an ideal field camera. A tripod is useful, but often impractical to carry on fieldwork. A walking pole with a camera mounting screw in the handle is a useful substitute; alternatively a rucksack or pile of rocks can make a good camera support where slow recording speeds are required. A polarizing filter is handy for removing reflections from wet exposures or rocks in streambeds.

The landscape is geology, so good landscape photography can make good geological photography: If it can be taken near dawn or dusk it can also be beautiful, but harsh midday light, or strongly oblique light, may be required to illuminate some geological features. Pictures of geological exposures can range from whole cliffs to sedimentary structures and fossils. The inclusion of a scale is important and a person set to the side of a photograph is useful, but a scale of known length is better. Geologists commonly include a hammer, lens cap, or coin in photographs for scale. Unfortunately, hammers that range from 100g to 1.5kg can all look the same on film; coins and lens caps are similarly variable. The best scale is one marked in centimeters and 10-cm sections placed near the edge of the photograph. Rock exposures are rarely memorable so a good practice is to take two photographs and include location details on one of them (grid reference or latitude and longitude) written in felt tip pen on a piece of rock or paper. For close-up photographs the screen information of a global positioning system can be included. The angle of the light on the exposure is important for showing weathered textures, but smooth rock exposures can benefit from being wetted and photographed using a polarizing filter. Photography underground is specialized and the techniques of cave and mine photography are similar Geology is not just static and processes such as erosion and deposition should be recorded. Geological hazards affect human lives, so floods, glaciers, volcanoes, landslides, and subsidence lend themselves to reportage-type photography.

Photography in the Laboratory

Camera equipment for use in the laboratory can be similar to that for the field, but the addition of a macro lens and extension tubes on an SLR, or a close focusing facility on a digital camera are essential. Good macro photography technique and the elimination of camera shake are important. A strong tripod or copy stand and cable release (or remote control) are essential. Lighting can be simple using small desk lamps, but an 80A filter for film, or digital cameras with white balance adjustment are required. Flash can be difficult to use especially if it is on the camera as the lack of any modeling light makes good results difficult.

Paleontological photography is like portrait photography, where harsh light and heavy shadows lose detail. Light should be diffuse, but directional lighting is also needed to show the fossil form. This light must come from the upper left, otherwise the fossil relief may appear inverted. Heavy shadows can be removed by photographing the fossil on a glass plate suspended above a neutral gray or white background. To show subtle features fossils can be selectively whitened by puffing sublimed (heated) ammonium chloride onto the specimen, a thin coating emphasizes sutures and fine surface details. For dark gray carbonaceous fossils on dark gray rock, detail can be shown by photography under water or alcohol, and with the light sources and lens covered by polarized filters. Digital imaging with computer manipulation (separating and combining channels and/or focus) can be used to tease information from unpromising specimens. X-rays, infrared, and ultraviolet photography may also help to image difficult subjects.

Minerals vary from glassy and transparent to metallic and earthy. Lighting techniques for photographing glassware (backlighting and darkfield illumination) can show details. For reflective specimens, careful angling of the light and the use of polarizing filters can control the illumination and show detail.

Photography of microfossils and thin sections is best done through a modern microscope with dedicated photographic attachments. Reasonable results can be achieved using camera attachments on microscopes, or by using a copy stand and light tight trap between the camera (lens removed) and the microscope eyepiece; attachments to fit small digital cameras to microscopes are also available. Vibration from SLR shutters is a problem with microscope photography so the use of flash, or timing the light source will be useful. In geology, thin sections of rock are ground and polished to a standard thickness (0.02-0.03mm); the transparent section can then be photographed with either transmitted light or crossed polarized light. With crossed polarized, transmitted light, one polarizer is located beneath the thin section and one at right angles above the objective. This situation gives bright polarization colors that help to define the mineral types. Reflected light microscopes and photography are used for metallic minerals and small opaque microfossils.

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