Sunlight, daylight, incandescent, fluorescent, and other artificial light sources all have color charteristics that vary signnificantly. Filters give you better images by adjusting for these light variations.
Film and video are rated for a particular color temperature such as that of daylight or tungsten light. Filters are used to correct differances in color temperature between the recording medium and the light source.
80A filters balances daylight film for use with most standard tungsten lighting, studio lighting and copy stand lighting.