Simple yet effective methods are available to enhance photographic images of low-contrast and low-relief specimens, such as fossils in shales, without manipulating or retouching the photographs. By applying polarizing filters to camera and light-source(s) in a way analogous to crossing nicols in a petrographic microscope, dramatic results can be achieved where there is a difference in reflectance between fossil and matrix, as with many coalified fossils. For example, this method is ideal for bringing out the shiny films representing soft tissues of Middle Cambrian Burgess Shale fossils. It is also useful in reducing reflections and increasing contrast in specimens that cannot be immersed in liquid (e.g., the Lower Cambrian Chengjiang fauna). Plants and graptolites in shales are other examples of suitable objects for this method. In addition, the use of digital imaging now makes it very easy to use interference between two versions to bring out differences. In this way, images of the same object taken with and without crossed nicols can be contrasted, as well as different colour channels. The result may be a dramatic improvement in the definition of hard-to-see or hard-to-image structures.

Stefan Bengtson, Department of Palaeozoology, Swedish Museum of Natural History, Box 50007, SE-104 05 Stockholm, Sweden.

KEY WORDS: photography, polarized light, image enhancement, shale fossils

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Copyright: Palaeontological Association, 15 April 2000
Submission: 18 February 2000, Acceptance: 29 March 2000