Product information "Cokin P035 81D Color Conversion Filter"
The 81 Series of filters control the bluish coloration that affects daylight film. An 81D is used as a warming filter to eliminate the bluishness of open shade on very clear days. The 81D is stronger than an 81C and is also used for general landscape photography on cloudy days as well as to add more of a "suntanned look" in portrait photography.
Filter factor 1.2 (+1/4 stop)
Related links to "Cokin P035 81D Color Conversion Filter"