A control device for an imaging system includes a video signal acquisition unit, a photometric unit, and a luminance control unit. The video signal acquisition unit is configured to acquire a video signal obtained by taking an image of fluorescence radiated from a subject under excitation by an excitation light that is emitted onto the subject. The photometric unit is configured to acquire brightness of the fluorescence based only on a color-specific video signal of one color corresponding to the fluorescence, the color-specific video signal being included in the video signal. The luminance control unit is configured to adjust luminance of a fluorescent image formed from the video signal, based on the brightness of the fluorescence acquired by the photometric unit.
