The hoya 81b hoya multi coated hmc glass filter controls the bluish coloration that affects daylight film it can also remove excessive blue from the effects of electronic flash its autumn the clouds are low hanging and the sky is patchy blue youve gone for a ride upstate to the mountains and the light in open shade is bluish a photo taken of your girlfriend with daylight balanced film leaning against the side of a barn will yield bluish tones that she might not find particularly flat