An electrical dimmer device and its driving method applicable to, for example, an image pickup unit and a display unit operate so that when a control signal for stop adjustment is changed from its current value of stop adjustment to a larger value, which occurs when the light transmissivity of a positive type liquid crystal is raised, or when the light transmissivity of a negative type liquid crystal is lowered, the control signal is temporarily varied to an intermediate value that is larger than the larger value. The energy of the varied larger value and a time during which that varied value is applied are determined in accordance with predetermined values. By doing so, it is possible to make a response speed when changing the light transmissivity extremely faster and thus attain a response time, of for example, one field period of time or less required for a stop mechanism of a video camera.