The twin lens reflex camera, abbreviated TLR, is characterized by having two objectives of the same focal length. One is the actual photographic objective[?], while the other is used for the viewfinder system. In addition to the objective, the viewfinder consists of a mirror, a matte focussing screen at the top of the camera, and a pop-up hood surrounding the focussing screen. The two objectives are connected, so that the focus shown on the focussing screen will be exactly the same as on the film. The typical TLR is medium format, using 120 roll film with square 6 x 6 cm images.