The 80 series of filters are blue. They are used to balance daylight film under artificial tungsten or standard (household) incandescent lighting. This filter measures 66 x 72mm and fits the Cokin A series holder. Filter factor 2 (+1 stop) 80 Series Color Conversion Chart 80A increases color temperature from 3200-5500 degrees Kelvin (commonly used with 3200K lamps) 80B increases color temperature from 3400-5500 degrees Kelvin (commonly used with photoflood lamps) 80C increases color temperature from 3800-5500 degrees Kelvin (commonly used with flashbulbs) 80D increases color temperature from 4100-5500 degrees Kelvin (commonly used to remove extreme orange or red)