Michael R. Peres and Joseph Cowan
Making photographs at the microscope can be difficult. For example, magnification produces problems associated with the depth of field, and diffraction creates problems with image resolution.
One of the most difficult aspects of photographing through a microscope is creating image contrast, especially with thin, nearly transparent subjects. An early solution was the implementation of dark-field illumination, which involves using oblique-angle lighting from outside the lens's field of view. In this method, a white subject appears in front of a black background because light refracts to the lens from the subject.