HOYA FL-D Filter

Used to correct the greenish tone that appears when daylight type
film is used under fluorescent lighting. The FL-DAY (FL-D) is for use with daylight type fluorescent lamps. It is recommended that auxiliary light sources be used when long exposures become necessary due to insufficient light.
Both the FL-D and FL-W filters can be used to create a dramatic colorcast outdoors when the cameras white balance is manually to daylight.