A shredder includes a housing having an opening for the insertion of media to be shredded. A cutting assembly for the shredding of media is disposed in the housing. A media detector including an infrared emitter and an infrared sensor is disposed about the opening for the detection of the presence of media to be shredded in the opening. A controller is disposed in the housing and is in responsive communication with the media detector for controlling the operation of the cutting assembly. The controller is programmed with a dynamic media detection threshold that is at least in part passed upon an emission sensed value and a background sensed value.