I don't do IR photography, but I did read about using an IR-pass filter in front of a shoe-mounted flash in order to trigger optical slaves without affecting the exposure. (Basically a workaround for pre-flash on Panasonic bodies). Using Infra Red Masters To Trigger Optical Slaves | DIYPhotography.net Does anyone know where to source ready-made sheets of IR-pass filters? Is unexposed, developed color slide film the best bet? Thanks!