Pane or foil with controllable transparency and light transmission comprises a layer configuration between two transparent carriers such as glass panes, foils or the like; transparent electrodes are disposed on the carriers; a tansparent electrolyte and an active polymer layer are disposed between the electrodes; the active polymer layer has light absorption in the visible spectrum range characterized by a variation in the case of a reversible chemical doping reaction; preferably an additional transparent layer is included to serve as reversible source for storage and yielding of ions, the additional layer is juxtaposed to the electrolyte.