The dark-field describes an illumination technique used to enhance the contrast in unstained samples. It works by illuminating the sample with light that will not be collected by the objective lens and thus will not form part of the image. This produces the classic appearance of a dark, almost black, background with bright objects on it.
To fit a darkfield condenser simply loosen the condenser holder screw, remove the existing brightfield Abbe condenser and replace with the darkfield condenser.
Type of darkfield condensor: dry