Photographic camera with liquid-crystal diaphragm arrangement

In a photographic camera, a diaphragm arrangement comprising liquid crystal material positioned in the path of light entering the camera, and means for changing the size of the opening of the diaphragm arrangement by alternatively changing the transparency of one or both of at least two portions of the liquid crystal material, the relative positions of said portions being such that when both are non-transparent light is blocked from passing between them and that when both are transparent there is between them no obstruction to the passage of light, wherein said means comprises two transparent electrodes positioned in the path of light entering the camera respectively in front of and in back of the liquid crystal material, one of said transparent electrodes having surface resistance, electrical circuit means operative for establishing between two spaced locations on said one of said electrodes a variable potential difference, thereby causing the potential difference between either one of said spaced locations and locations on said one of said electrodes intermediate said spaced locations to have a value dependent upon the distance from said spaced locations, and additional electrical circuit means operative for maintaining the different portions of the other transparent electrode at a potential such that a continuous change in said potential difference will result in a continuous change in the potential difference between corresponding locations on the two transparent electrodes and accordingly a continuous change in the size of the non-transparent portion of the liquid crystal material intermediate the transparent electrodes.