The Heliopan 39mm KR15 (85B) Glass Filter will produce natural colors when shooting with tungsten film outdoors. Using tungsten film in daylight will produce a bluish cast in the photograph.
What do you do when you must take some photos outdoors and all you have left is tungsten film? Using tungsten film in daylight will produce a bluish cast in the photograph. The 85 series of filters will "bring back", i.e. color balance the tones in your images. These yellow filters are used to correct differences in color temperature between the recording medium (film/video) and the light source.
An 85B filter converts tungsten film to daylight. An 85C produces the coolest results - more than either the 85 or 85B. However, it is interesting to remember that an 85C is also useful as a creative warming filter with daylight film in daylight.
Heliopan Lichtfilter-Technik of Munich, Germany, has changed their black anodized brass filter rings on most Heliopan non-rotating filters to their "slim" mounts. These slim mounts are made of black anodized brass stock and have so little rim in front of the lens (5.4mm) that they will not vignette with lenses as short as 21mm.
Heliopan offers a wide selection of sizes, screw-in, series, bayonet, square and rectangular filters including digital, video, center weighted, graduated, wide angle, Kaesmann polarizers, drop-in polarizers, etc.