Multi light imaging of small compression fossils – proper tools and a neat shortcut

The interpretation of compression fossils can be very challenging due to multiple structures
overlying each other. Therefore, it is often not sufficient to use only one image modality.
Photographs taken with grazing light from multiple directions can be used in order to highlight
small-scale surface details that are not apparent from the colour of the fossilized material. Yet,
when presenting the findings this can come at the cost of needing many images to illustrate various
parts of a fossil. However, there are several techniques that can harvest the information from a
set of images taken with different illumination settings (Multi Light Image Collections) by creating
digital models of the fossils. One such set of techniques is centred around the reflectance properties
(Reflectance Transformation Imaging), while other techniques aim to recover the surface shapes
(Photometric Stereo). Both sets of techniques have been successfully used to study fossils; however,
they have not become widespread in palaeontology. Here I aim to explain methods of adapting the
techniques to the study of compression fossils by means of overcoming photographic limitations,
custom hardware and automation, as well as to present a way to capture similar datasets using a
flatbed scanner.