Next in order of complexity may be ranked the bag magazine (Figs. [31] and [44]). In this the exposed plate is pulled out of the magazine proper by a metal slide or rod into a leather bag. The rod is then pushed back, the plate in its metal sheath is grasped through the leather bag, lifted to the back of the magazine, and forced in behind the other plates. The number of plates exposed is indicated either by numbers on the backs of the sheaths, visible through a red glazed opening in the back, or else by a counter actuated by the metal slide rod. Usually twelve are carried in a magazine. For aerial work the common design of this magazine as used for ground work must be modified by providing extra large easily grasped hooks both on the draw rod and on the dark slide, which must be drawn before making the first exposure and replaced after the last. The small rings and grips of the standard commercial magazine are almost impossible to handle through heavy gloves.
The next type of magazine is represented by three designs, the Gaumont and deMaria, used very generally by the French during the war, and the Ernemann, used almost universally in the German air service (Figs. [32], [40] and [42]). In all of these the operation of plate changing is the same: the end of the magazine is pulled out and thrust back, a more simple operation than the bag manipulation just described. The internal workings are different according to size. In the smaller French magazines (13 × 18 cm.) the camera is first pointed upward, all the plates are drawn out except the one to be changed, and this, with the aid of springs, drops to the bottom, after which the other plates push back over it. The plates pull out in the direction of their long dimension. In the larger French magazine (18 × 24 cm.) only the exposed plate pulls out. The pull is in the direction of the shorter dimension of the plate, which is lifted up by heavy springs and slides back over the top of the pile. In the Ernemann magazine only six plates are carried, which there is good reason to believe represent the maximum feasible number, judging by the reports of jambs and breakages in the twelve-plate French magazines. In all of these magazines laminated wood slides pull out and in at each operation, and while satisfactory if made and operated in one climate, experience indicates that if made in America and sent abroad swelling of the wood may be expected to prevent their successful operation.
Fig. 32.—Various plate magazines used on aerial cameras.
Alternative forms of magazine, somewhat more practical from the standpoint of manufacture and export, are several designs embodying two compartments (Fig. [32]). In the most simple of these the plates are moved, immediately before or after exposing, from the unexposed to the exposed side. Illustrative of this type are the Folmer designs, in which the to-and-fro motion is imparted by a rack geared to a pinion actuated either by a lever, in the hand camera, or by the power drive, in the automatic design (Figs. [33] and [53]). Another illustration is afforded by the Piserini and Mondini magazine, in which the operation of changing is performed by a back-and-forth motion of a hand-grip, which also sets the camera shutter (Fig. [47]).
Fig. 33.—U. S. Air Service hand camera, with two-compartment magazine.
Fig. 34.—Film type hand camera.
In these magazines the center of gravity changes as the exposed plates are moved over, and only half the inside space is occupied with plates. These objections are overcome in the Chassel form, where both compartments are always full. Transfer of the bottom exposed plate from one compartment to the other is compensated for by the simultaneous shift of the top plate in the receiving compartment, to the feeding side. In a modification of this idea by Ruttan the exposing position is when the plates are half-way through the shifting process, whereby the magazine may be symmetrically mounted on the camera body.