DARKFIELD TRANSMITTED LIGHT
microscopes produce images in which the specimen appears light
against a dark background. This effect is achieved by placing a Darkfield
"stop" in the filament plane of the condenser. This
"stop", often in the form of a slider or insert, is an opaque
circle which keeps the light from being transmitted straight through the
specimen to the eye. Rather, only light coming around the stop is
allowed to strike the object. Because of the sharp angle of
incidence, only the light which is scattered by the specimen reaches the
eye. At high magnifications a special oil immersion Darkfield
condenser may have to be substituted for the normal Brightfield
condenser.
