The invention relates to a shutter for an optical imaging system, e.g. a digital camera. The shutter comprises an interface between a transparent body and a capillary space. Light rays introduced to the active area of the interface are reflected by total internal reflection when the capillary space is filled with a gas. The light rays are transmitted through the interface when the capillary space is rapidly filled with a liquid. Thus, the light rays are either absorbed or reflected towards an image sensor, depending on the state of the shutter. The liquid is delivered to the capillary space through at least one duct which is positioned opposite the active area.