The Tiffen 4x4" Dark Red #29 Filter is ideal for strong contrast improvement since it absorbs green and blue completely and enhances red. In addition to contrast control, red filters enhance skin tones, tonal corrections and are effective for more dramatic landscapes. What a wonderful filter! Turn a puffy white-clouded sky into a threatening storm! Like your green apples even greener? Pull out that red filter! Add a polarizer and that sky previously mentioned turns even more ominous. A standard red filter is a #25. The #29 is stronger and will increase the above mentioned effects. Stronger than a #25 red Clouds are dramatically improved almost to the mood of a thunderstorm; Darkens blue sky creating dramatic contrast between sky and clouds Use with Polarizer for dramatic black and white effects It is more effective in cutting through haze, and moonlight effects are easily accomplished; Creates greater contrast between foliage and flowers Used in scientific photography Excellent copying filter for blueprints