<P> Specialised condensers are also used as part of Differential Interference Contrast and Hoffman Modulation Contrast systems, which aim to improve contrast and visibility of transparent specimens . </P> <P> In epifluorescence microscopy, the objective lens acts not only as a magnifier for the light emitted by the fluorescing object, but also as a condenser for the incident light . </P> <P> The Arlow - Abbe condenser is a modified Abbe condenser that replaces the iris diaphragm, filter holder, lamp and lamp optics with a small OLED or LCD digital display unit . The display unit allows for digitally synthesised filters for dark - field, Rheinberg, oblique and dynamic (constantly changing) illumination under direct computer control . The device was first described by Dr. Jim Arlow in Microbe Hunter magazine, issue 38 . </P> <P> Like objective lenses, condensers vary in their numerical aperture (NA). It is NA that determines optical resolution, in combination with the NA of the objective . Different condensers vary in their maximum and minimum numerical aperture, and the numerical aperture of a single condenser varies depending on the diameter setting of the condenser aperture . In order for the maximum numerical aperture (and therefore resolution) of an objective lens to be realized, the numerical aperture of the condenser must be matched to the numerical aperture of the used objective . The technique most commonly used in microscopy to optimize the light pathway between the condenser (and other illumination components of the microscope) and the objective lens is known as Köhler illumination . </P>

Condenser and iris diaphragm are useful to coordinate what