The Polaroid IR720 72 mm Infrared X-Ray Filter is so named because it will filter out most light below and above the wavelength of 720 nanometers (near infrared). The filter blocks most visible light and is therefore very opaque. In addition, a camera's auto exposure will not work. It is recommended that a tripod be used in conjunction with this filter because exposure times tend to be quite long. When using this filter, compose your scene first, then attach the filter.
Most digital camera sensors are inherently sensitive to infrared wavelengths. To prevent the auto exposure system from miscalculating exposure settings, digital cameras incorporate infrared blockers and special lens coatings. In spite of this, unique variations of uncontrollable focus, improper exposure and hot spots can create spectacular artistic effects.