This B&W 43mm 81A Warming Conversion Glass Filter has an effect similar to that of the Kodak Wratten 81A gelatin filter. It is also similar to the KR1.5 (Skylight) conversion filter except that it is less reddish as it absorbs a little bit of the red.
The 81A controls the bluish coloration that affects daylight film. It can also remove excessive blue from the effects of electronic flash. Good for general scenics when the photographer wishes to remove the bluish cast from open shade or just add warmth to the photograph.
Note! Whereas the KR series (and the 81 series) of filters creates a feeling of warmth, the KB Series (and the 82 Series) creates a feeling of coolness