The cokin p series p026 warm 81a filter is designed to add warmth to a photograph whilst removing bluish casts from open shades this filter controls bluish coronation found in daylight film as well as eliminates excessive amounts of blue from the effects of electronic flashes this product is a mild light balancing filter which reduces colour temperature slightly for a warmer tone it corrects propensity towards blue tones and alters colour temperature 81 series conversion fac