A camera adaptor (19) is provided for connecting a camera (21) to an interface (13) of a medical-optical observation instrument (1) with a parallel beam path. The interface (13) is situated in the parallel beam path (9a, 9b) of the medical-optical observation instrument (1). The camera adaptor (19) has an instrument connector part (41) for connection to the interface (13) of the medical-optical observation instrument (1) and a camera connector part (43, 143) for connection to a camera (21). The beam path (43) runs through the camera adaptor (19) along a linear optical axis. The camera adaptor (19) has an objective-lenses combination (47) with a total focal length between 40 mm and 120 mm. A lens with a positive partial focal length leading on the instrument side in the objective-lenses combination (47) and is followed, on the side toward the camera, by a lens with a negative partial focal length.