The Chinon CS has an in-built light meter that was designed to be powered by a 1.35 volt PX13 mercury cellproviding a constant power source. Due to environmental reasons,mercury batteries are no longer readily available in many countries.Suitable replacements include a 1.5 volt Alkaline battery (togetherwith an adjustment in the camera's film speed setting), a 1.35 voltWeinCell zinc/air battery, or a number of other PX13/PX625 batterysubstitutes.