The Heliopan 39mm 81C Filter controls the bluish coloration that affects daylight film. This is a strong salmon colored filter that can bring skin tones back to a respectable tone when the light changes during the day. It is especially useful under cloudy or open shade conditions since as the light changes, so does the color temperature. An 81C will decrease the color temperature by approximately 100 degrees Kelvin more than an 81B. An 81C can also be used with electronic flash to reduce the amount of "blue" generated by the flash. An 81C is a strong filter that can also be used to make a warm scene even warmer such as a beach shot where you wish to enhance the overall sense of temperature.