The Heliopan 46mm (81A) Filter controls the bluish coloration that affects daylight film. An 81A filter will allow you to correct white balancing issues when you wish to reduce the color temperature of the shot and bring your tones back to a more acceptable level. An 81A can also be used with electronic flash to reduce the amount of blue generated by the flash. This filter is also useful when shooting at higher elevations where the light tends to run towards the blue end of the spectrum.