Hoya infrared 72mm 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 w