A system and method are described for controlling voltage on discharge capacitors which control light energy from flash lamps, wherein the method includes measuring over time an operational behavior of a flash lamp for performing photothermolysis, wherein a discharge capacitor transfers energy to the flash lamp, empirically deriving a behavior of the flash lamp as a function of operation over time, and using the empirically derived behavior of the flash lamp to control a voltage of the discharge capacitor and thus energy transferred to the flash lamp.