The shutter is a spring one, operated pneumatically, and consists of 2 metallic discs, each containing an aperture and passing in opposite directions between the 2 sets of lenses of the objective at the place where the diaphragm is usually situated. It gives exposures that may be varied at will from 1/80 to 1/120 of a second.
The camera is divided into 2 spaces by a partition (Fig. 242, S) which is light-proof. The folding sides of the camera are formed of strips of cardboard, one thickness of black taffety, and kid skin. The right side (Fig. 242, sg) forms a chamber which is designed to allow the objective to the left 0 to form an image upon the ground glass gl. The left side sd circumscribes the space in which the objective that carries the shutter ob forms an image upon a sensitised plate contained in the box B.
The 2 objectives are carried by a wooden front fr. A large -frame c carries the ground glass and plate box, and, at the same time, serves as a point of attachment for the folding sides. Adjustment is effected by moving the front / toward or away from the frame c by a mechanism that is described farther on. The plate box is sufficiently spacious to hold 12 plates in 2 piles of 6 each. Each plate is fixed in a small wooden frame, provided at the back with a very thin piece of sheet iron, which intercepts the light between it and the following one.
The 2 piles of frames are separated from each other by an incomplete partition that leaves enough space here and there for one of the frames to slide from one pile to the other. If, then, this 12-frame box contains but 11 frames, an empty space remains, and it will always be possible, by inclining the box, to cause the eleventh frame to slide from one pile to the other. When a plate has been exposed, it is therefore only necessary to incline the apparatus toward the right to cause the plate to enter the compartment situated on that side. If, now, the apparatus be pointed so that the objectives face the ground, and afterward be inclined to the left, one of the plates to the right will slide on to the pile to the left. Before each exposure it is well to tighten the screw v a little, in order to apply the foremost frame against the end of the box and give it exactly the same distance from the objective that the ground glass has. By repeating the same motions the 11 plates will be exposed in succession without any confusion being possible, and without there being any necessity of opening the box, or of allowing light to pass at any other moment than that of the exposure.
When the exposure is at an end, a metallic plate is pushed, and this separates the interior of the plate box from the chamber to the right. The box, being now closed on all sides, may be removed and placed entirely in the frame c, which is closed by a small door. When the front end is applied to the frame, the entire apparatus is reduced to a box, 5 x 6} X 10 in. in dimensions.
The focussing is effected by 2 metallic frames provided with racks (Fig. 243) that are placed beneath the apparatus - one of them carrying a front piece, ci, and the other, cs, sliding in a groove in the frame. These two frames are set in motion, one over the other, by a lateral button P, at the end of a rod that carries 2 grooved cylinders p. These grooves engage with the rack of the lateral pieces of the metallic frame ci. The frame cs is set in motion by a horizontal wheel R, which has a vertical axle that terminates beneath in a knob which is held in the left hand and serves to support the apparatus. It is only necessary to slightly turn the palm of this hand in one direction or the other to bring about a rapid motion of the frame cs, and consequently of the entire front end with the objectives, through the intermedium of the large wheel R (Fig. 24-3). A small wheel r serves for transmitting the motion of the large one to the opposite side of the frame, and to give it a parallel sliding motion free from any lateral displacement.
When in use the apparatus is affixed to a frame (Fig. 244) which is like a gun-stock in form, but which consists of four hinged pieces that permit of its being folded up. The front part contains a tube (Fig. 244, t) in which slides a piston pi, actuated by a spiral spring sp. This spring, upon uncoiling, drives the piston suddenly forward and produces a compression of the air which is transmitted, through the rubber tube ca, to the shutter, and unfastens it. In order to tighten the spring up it is only necessary to draw back the piece ch, until it hooks itself to the trigger g. A pressure of the finger upon the latter is sufficient to set the shutter free.
The mode of using the apparatus is as follows: The plate box being inserted, the shutter raised, the stock placed against the shoulder, and the spring tightened, it suffices to turn the apparatus toward the object to be photographed, and to examine its image upon the ground glass. A slight movement of the left hand effects the focussing, while the index of the right hand determines the amount of exposure. It is only necessary, then, to incline the apparatus successively in 2 directions to cause another sensitised plate to succees the one that has just been exposed; and, when the spring has again been tautened, one can proceed to another exposure.
With the plates now in market, there may be obtained in open air, in tine weather, in summer and in the middle of the day, very excellent negatives. Under other circumstances, such rapid exposures are insufficient to impress the plate to the desired degree for a good negative.
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