takes for the electrochromic filter to revert to the clear state is the internal leakage current i ds of the electrochromic filter to speed up changing states from dark to clear a parallel resistor r p is used to bleed off excessive charge from the electrochromic filter for an electrochromic device that has a maximum input voltage v ec of 1 75 volts and a photovoltaic element maximum voltage of 2 0 volts and assuming a 0 2 ma discharge current i ds the following can be calculated equ1 the value of resistor r p is chosen to be high enough to force electrical current through electrochromic filter 5 yet low enough to allow the optical density of electrochromic filter 5 to change with sufficient speed as light conditions change referring to fig1 and 2 in operation during very bright scene conditions e g outdoors on a sunny day photovoltaic element 6 puts out a relatively high voltage causing the optical density of electrochromic filter 5 to become relatively high as a result a relatively large percent of the scene light is blocked by electrochromic filter 5 from proceeding towards imaging element 4 during poorly lit scene conditions e g outdoors at night photovoltaic element 6 puts out a relatively low voltage causing the optical density of electrochromic filter 5 to become relatively low as a result a relatively small percent of the scene light is blocked by electrochromic filter 5 from proceeding towards imaging element 4 preferably the system parameters are selected such that 1 when the scene is of average brightness part way between a sunny day outdoors at noon and a poorly lit night scene the optical density.