A warning system of a camera for providing a photographer a warning indicating an impediment to a window, provided in a front wall of the camera, through which light traveling toward and/or from a subject passes. It includes a touch sensor, disposed in close proximity to the window, which involves a resistance, or a body capacity, of a photographer's finger touching the sensor in, and as a part of, an electric circuit. This provides a change in electric parameter of the circuit by which a warning device is actuated to emit light, or otherwise generate sound, as the warning of impediment.