Hoya Infrared - 77mm filters block all visible light letting only infrared light in different wavelengths pass. The number in the filter name (R72) is an indication of the cut-off point for visible light, in this case, 720 nanometers (720nm), the higher the figure, the more the filter ignores visible light. Infrared filters are constructed of optical precision ground and polished glass and appear black to the human eye. The HOYA Infrared R72 filter will enable you to create amazing black & white images with a hint of cyan & magenta. This type of filter is also used in crime detection, medical photography, detection of distribution of vegetation, etc.