Abstract: A lamp dimmer suited for fluorescent and other lamps which controllably notches the applied voltage to a lamp circuit each half cycle. Progressively larger dimming control voltages produces progressively wider notches as well as progressively causing the notches to be further from the zero-crossing occurrence toward the peak occurrence of the half cycles, thereby providing means for varying power to the light circuit. Optocoupler means is employed with respect to a power output bridge to isolate the control circuit from the power output circuit to the lamp. A photosensor used to sense the ambient light conditions is used to produce the dimming control voltage so as to achieve a balancing effect between the ambient and the artificial light produced by the lamp.