Abstract: Apparatus for positioning, centering and holding film within a large format industrial camera for exposure within a light-tight exposure chamber, the bottom of which holds a transparent plate to receive the film at the focal plane, a two piece platen of flat rigid material, hinged together in abutting relationship, is carried above the transparent plate. One of the platen pieces is provided with a series of elongated slots therethrough to receive a series of elongated stops. The stops are yieldably carried by said platen piece for movement through the slots in the platen piece into the path of the desired size of film as it is slid across the plate and under the platen pieces. A control arm of generally "L" shape is swingably carried on each of the elongated stops. The control arms are selected for the desired film size and can be located and swung into position by a single finger operation without need for seeing them.