By the sea, in the mountains, beneath the tropical sun your skin picks up flattering colors. Your photos, however, pick up mostly blue casts due to Ultra Violet (UV) rays. Cokin Skylight and UV filters eliminate these casts and clarify distant haze. Skylight filter #230 reduces UV rays and distance haze, and reduces blue cast approx 1/10th of a stop. Ultra Violet filter #231 reduces UV rays and distance haze. It offers no color change and is a ideal as a lens protector. Skylight filter(1B)#232 is the same as #230 except it reduces blue 2/10th of a stop and is recommended for high altitude and "sky" shots