The _German film mapping camera_, shown in Fig. 61, is distinguished by a number of special features. The size of the pictures, 6 × 24 centimeters, is unusual. It has its advantages, however. Since the short dimension is in the line of flight, the maximum width of field covered by the lens is utilized (Fig. 17). This of course necessitates a larger number of exposures to complete a strip, which is perhaps an added advantage, since the narrower the individual pictures the better the junctions will be, especially if large overlaps are made. This proved to be the case with captured German mosaics. Difficulty is experienced in making overlaps on a turn (Fig. 62), but this is not a vital objection. The shutter has a fixed aperture, narrower at the center than at the ends, to compensate for the falling off in illumination away from the center of the lens. No safety flap is needed because the curtain moves in opposite directions on successive exposures, thereby also compensating for shutter distortion, as has already been discussed. Shutter speed is controlled by varying the tension of the actuating spring. [Illustration: FIG. 61.—German automatic film camera.] The camera is driven by an electric motor, connected to a set of gears, whose shifting provides for speed variation. The film is moved by rubber rollers which are cut away for part of the circumference, allowing the film to stand still until they bite again. A yellow glass pressure plate holds the film during the exposure and serves as color filter also (Fig. 63). An electric heater is provided near the shutter, as in all the later German cameras. [Illustration: FIG. 62.—Method of joining and printing film from German camera.] _United States Air Service automatic film camera_—_Type K_ (Figs. 64, 65, 92, 93, 98, 99). This is an entirely automatic camera, manufactured by the Folmer and Schwing Division of the Eastman Kodak Co., taking 100 pictures of 18 × 24 centimeter size at one loading. As with all the American cameras of this size, it uses the standard lens cones of any desired focal length. The camera proper consists of a compact chamber in which the film rollers are carried at each end forward of the focal plane, the shutter lying between. In consequence of this arrangement the vertical depth of the camera is the absolute minimum—short of decreasing the length of the optical path by mirror arrangements—making it possible to suspend the camera diagonally in the American and British planes, for taking oblique pictures. Flatness of the film is secured by a suction plate covered with graphited cloth and connected with a Venturi tube. The top cover is removed for re-loading. The shutters on the first cameras of this type are of the variable-tension fixed-aperture design, though later ones have the variable-aperture curtain controlled by an idler, as used in the American deRam. An auxiliary curtain shutter serves to cap the true shutter during setting.