A Kodak 4 x 12" #47B Deep Blue Wratten Gel Filter for Tricolor/Color Separation Work accentuates haze and fog. Also used in dye transfer printing and for contrast effects (lightens blue tones).
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 30.5cm).