FLW corrects neon light. It eliminates the green tint in neon lighting. No one has ever looked good under the white light of fluorescent tubes; this is clearly evident in color photos due to the unappealing green tones. The COKIN FLW filter was specifically designed to neutralize the main tone of the most commonly used fluorescent lights. You should always have this filter with you for all public places (train stations, restaurants, offices, etc.) where you cannot change the lighting.