A method for testing an optical investigation system, with an imaging device, a video camera and a light source for optical investigation of an object including a reference surface with predetermined optical properties being illuminated with illuminating light from a light source. An image of the reference surface is recorded by the imaging device and the video camera. An operating condition of the video camera that prevails during the recording of the image is recorded. The functionality or another property of the investigation system is determined on the basis of the recorded operating condition.