The cokin z pro series z036 flw filterrsquos main function is to either remove or decrease the amount of greenish cast created by fluorescent lighting such as white tubes fl filters bull fl d filter shooting under general purpose fluorescent lighting with daylight film can cause greenish tones to appear the fl d filter can be used to correct this bull fl w filter balances daylight film under warm white or white type fluorescent lamps bull fl b filter corrects colour ba