Any automatic mechanism in the airplane must work well in spite of vibration, three dimensional movements, and great range of temperature. The requirements were well recognized when the war closed, but had not yet been met. Careful study of the conditions and needs by competent designers of automatic machinery may be expected to result at an early date in reliable cameras of the automatic type, but the description below of hand-operated cameras really covers practically all the cameras found satisfactory in actual warfare. =General Characteristics of Hand-operated Cameras.=—As distinguished from the hand-held cameras the larger hand-operated cameras are characterized by the greater focal length of their lenses, the size of plate employed, and the manner of holding—by some form of anti-vibration mounting attached directly to the fuselage. Except for the early English C and E type cameras which called for 10 inch lenses and 4 × 5 inch plates, the general practice at the close of the war by agreement between the French, English and American Air Services, was for the use of 18 × 24 centimeter plates and for lenses with focal lengths of approximately 25, 50 and 120 centimeters. The English also made use of a 14 inch (35 centimeter) lens, and never made a regular practice of anything larger than 50 centimeters. The Germans and Italians restricted themselves to the 13 × 18 centimeter size of plate, while a lens of 70 centimeters focal length was standardized with the Germans, in addition to the 25, 50, and 120 centimeter. The particular focal length was determined by the nature of the photographic mission. Where large areas were to be covered at low altitudes or without the demand for exquisite detail, the shorter focus lenses suffice. The most commonly used lens in the French Service was the 50 centimeter, while the 120 was employed when high flying was necessary or when minute detail was required. As already mentioned, the common practice was to keep cameras of all focal lengths available, but the ideal at the close of the war was to have the camera nose and lens a detachable unit, so that any focal length desired could be secured with the same camera body. _The standard French camera._ The hand-held form of French camera has already been described. The cameras for larger plate sizes and longer focus lenses differ only in the addition of a Bowden-wire distance release for the shutter and in the use of the Gaumont magazine which operates without the necessity of pointing the exposed side of the magazine upward. Fig. 40 illustrates the 50 centimeter camera, and Fig. 41 the 120. [Illustration: FIG. 40.—50 centimeter deMaria hand operated camera on tennis ball mounting.] [Illustration: FIG. 41.—120 centimeter deMaria camera.]