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A previously proposed method for preventing the illegal recording of movies, which uses a charge-coupled device or a complementary metal oxide semiconductor device to add noise signals to the recorded content, is ineffective when the digital camera or camcorder used for the recording is equipped with an infrared-cut filter. The method has now been enhanced to make it effective even when an infrared-cut filter is used. Infrared rays specularly reflected from the filter are detected using an IR camcorder with a short-wavelength cut filter. Testing using a prototype system implemented on a 100-inch cinema screen showed that the enhanced method effectively detects in real time a camera or camcorder equipped with an infrared-cut filter.