The 81 Series of filters controls the bluish colouration that can affect daylight film. They warm scenes shot on cloudy days. They can also remove excessive blue from the effects of electronic flash. These filters are also good for general scenics when the photographer wishes to remove the bluish cast from open shade or just add warmth to the photograph. The 81 series is available in grades from 81 through 81EF, with 81EF having the warmest effect. Lee resin filters are made from lightweight, optical polymeric materials and are 4 x 4" (100 x 100mm).
Using tungsten film in daylight will produce a bluish cast in the photograph. The 85 series will produce natural colours when shooting with tungsten film outdoors. Conversion is from 5500°K to 3400°K. +2/3 stop.
These filters control the spectrum by reducing the transmission at specific wavelengths. They are primarily used to colour balance films, the required filter being determined as a result of tests, or as specified by the manufacturer. They can also be useful for correcting light sources for which no one conversion filter exists, or for adding a deliberate colour bias.
Darker and redder than chocolate or sepia, a very strong effect.
Lee Red 30 Resin Colour Correction Filter.