Printing devices include a media supply storing print media, a luminescent belt positioned adjacent the media supply in a location to move sheets of the print media from the media supply, a print engine positioned adjacent the luminescent belt in a location to receive the sheets from the luminescent belt, an optical sensor positioned adjacent the belt in a location to receive belt-emitted light from the luminescent belt, and a processor electrically connected to the optical sensor. The processor receives the image from the optical sensor and identifies locations of the sheets on the belt based on where the sheets block the belt-emitted light from the luminescent belt.