The prismatic focuser enables one to observe the subject to be filmed directly through the taking lens, with the latter already in position. It is intended for use before the Model H camera is loaded, as most modern films have an opaque anti-halo coating which prevents the use of any other system of accurate direct observation. Should it become necessary to carry out viewfinding and focusing again before the reel is finished, the camera will have to be ubnloaded temporarily . It gets inserted into the film gate, and allowed focusing at the film plane through the taking lens. Although useful for cinemicrophotography, animation and title work, its use is rather limited for normal filming as the film door and pressure pad are removed while focusing.
