This Kodak 4x12" #26 Red Filter is ideal for strong contrast improvement since it absorbs green and blue completely and enhances red. Clouds are dramatically improved almost to the mood of a thunderstorm. It is more effective in cutting through haze, and moonlight effects are easily accomplished. It is also suited for infrared photography.
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), and 14 x 18" (350 x 450mm)