May 1976. Langzeitfilm für Umgebungslicht is exhibited. Daylight falls into the room through a window and the artificial electric light from a bulb is thus confronted with daylight. McCall draws a line on measuring sheets on the wall for the duration of the exhibition; it represents the constant that is the artificial light. Added to this are a regularly ascending and descending curve, signalizing the fluctuating light from outside. In another room a light cone is shown. The public is asked to fill the room with cigarette smoke.