Projected visuals refers to media formats like slides, filmstrips, and overhead transparencies where still images are projected onto a screen through a series of lenses. Opaque projection allows the projection of non-transparent materials by reflecting light off the surface rather than transmitting light through it. While opaque projection allows for on-the-spot projection of various classroom materials, it requires a dark room and produces dimmer images due to its less optically efficient process of reflected projection. Overhead projection allows presenters to face their audience while manipulating materials through marking and pointing, but printed materials must first be made into transparencies.