The Kodak 4 x 12" #38A Blue Special Color Effect Wratten Gel Filter is useful for correcting the tendency of reds to reproduce too lightly under tungsten illumination; when used for portraiture, skin tones are more natural and modeling is improved.
Most Kodak gelatin filters are available in 3 x 3" (75 x 75mm), 4 x 4" (100 x 100mm), 6 x 6" (150 x 150mm), 14 x 18" (350 x 450mm) and 4 x 12" (10.2 x 30.5mm)
Used to alter the color wavelength of light and make changes in contrast in black and white photography
Light balancing filter