This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American
[The following is a guest post by entomologist Guilherme Ide Marques dos Santos, of the Museu de Zoologia da USP, Brazil]
Scientific photography is an important part of many publications. In taxonomy, for example, good images assist species identification, as written descriptions may be more difficult to follow than directly comparing the specimen with a picture.Scientific photography is not used only in research articles, but also in museum databases. Large, well-curated specimen databases housed in an institution translates to fewer loans and lowered risk of specimen damages.
In entomology, good scientific photography is especially important. Microscopes and macro lenses have improved to be able to capture the fine details of insects with precision. As the equipment has improved, new techniques are being developed for image processing, like focus-stacking images (with focus-stacking, the photographer takes several exposures, each with different focal plane, and when merged digitally they build a completely focused image.)
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Lighting is among the most challenging aspects of microscope photography. Many articles have been published about illumination. For example, for photography through a stereomicroscope where even front lighting is desired, dome lighting is a good choice (Fisher 2012, Kerr et al. 2008). A white dome placed around the specimen brings homogeneous reflected lighting and allows side lighting control using a black card to reduce light from certain directions.
However, an under-emphasized technique for enhancing the borders of the subject is backlighting. I prefer to use grey background to a white one, as the latter reflects too much light that can overwhelm the specimen border, reducing specimen details.
So, how may we achieve back lighting in a dome using a grey background? One option is to add extra lights lower than the specimen, but this active backlighting solution is more complicated and expensive than using the simple and almost costless passive backlighting solution described here.
Instead, we create a nice reflected back lighting using just white paper arranged in a frame under the subject to reflect the dome light. Placing the paper strips around the specimen, in a lower position and out of the microscope's visual field, we create neutral grey background with the borders of the specimens highlighted from reflection off the white paper strips. This technique is especially useful for emphasizing hairs.
References
Fisher, E.M. 2012. Dome Light Update. Fly Times 48: 2-9.
Kerr, P.H., E. M. Fisher & M. L. Buffington. 2008. Dome lighting for insect imaging under microscope. American Entomologist 54(4): 198-200.
