A transmitted-light base (1) for illuminating an object (15) for imaging through a zoom microscope (21), the transmitted-light base (1) comprising an integrated light source (3, 17, 18) having an associated electrical power regulation system (31) for generating a suitable radiation flux, and means (5, 6), capable of being added downstream, for generating a specified spectral intensity distribution, wherein the light source is embodied as a reflector lamp (3);
- and arranged close to the light exit side of the reflector lamp (3) is a continuously controllable mechanical brightness regulator (4) having an associated adjustment device (41) by way of which the brightness regulator (4) is activatable in such a way that the illumination intensity of the transmitted-light base (1) is controllable with no change in the spectral intensity distribution.