The Cokin 720-89b infrared filter is specifically designed for infrared photography with digital cameras and infrared film. Infrared light starts in the high-red area of the visible spectrum at around 750nm and goes up beyond 1000nm. This light is not visible to the naked eye. Looking through the filter looks almost opaque because the filter is only passing light from the very high red edge of the visible spectrum and infrared light. Infrared photography yields very interesting, sometimes stunning, and creative result as objects in a scene reflect infrared light differently than normal light. Due to the nature of infrared light, filter factor and exposure compensation vary widely from visible light and depends largely on lighting conditions. It works well with digital cameras, especially mirrorless cameras or DSLRs with no IR blocking filter in front of the sensor. (Please check your camera's owners manual). and it only passes light at 720nm (high-red) and above. Gives more predictable results than filters that only pass infrared light above 850 or 900nm.