The cokin a series a020 blue 80a filter balances 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 colour conversion chart bull 80a increases colour temperature from 3200 5500 degrees kelvin commonly used with 3200k lamps bull 80b increases colour temperature from 3400 5500 degrees kelvin commonly used with photoflood lamps