Like a phase-contrast attachment, the Nomarski differential interference-contrast (DIC) attachment can be easily adapted to any ZEISS microscope of the STANDARD KK, RA, WL, UNIVERSAL, PHOTOMICROSCOPE or ULTRAPHOT series. Since phase contrast observation will in some cases be a valuable supplement to DIC observation, the condenser for the Nomarski method also contains annular diaphragms for the phase contrast technique. This guarantees quick and easy changeover from one of these differentiation methods to the other. However, this applies only to the equipment for substage illumination. With reflected light, there is no need for a combination of the two techniques, since the Nomarski method is here clearly superior to phase contrast.