The Optical Magic Lantern Journal (April 1890)

The Optical Magic Lantern Journal and Photographic Enlarger. 83 Photoramic Camera. SOME time ago we alluded to the effects that could be produced upon the screen by a number of consecutive pictures of ascene. We also mentioned that a camera capable of making several exposures each second had been devised by Mr. Friese Green. To outward appearance this camera is a box of about 9 in. square ; a lens protrudes from one end, and a crank handle from the other. Each time the handle is turned, four exposures are made on a prepared film, the film travelling along the requisite distance before the shutter is opened for exposure. The handle (see Figures 1 and 2) is connected with the main shaft, which by suitable gearing pays off and re-winds the sensitive film, the stock being contained on the upper spool. A suitable arrangement is provided for causing the film to remain stationary during the momentary space of time that the exposure is being made, which (says the Photographic News) is the cleverest part of the invention. “Immediately beyond the exposure screen, and between it and the up-winding roller, is an intermittently-acting drum of such diameter or circumference as that each other turn will take up and roll forward the exact amount of film required for each picture ; in passing this film forward, the drum also draws into the exposure position a fresh length of film ready to be exposed. To effect this intermittent motion, the aforesaid drum has a single, long escapement tooth, which, when the drum is not in motion rests on the cylindrical surface of a slotted pinion, which gears into, and is driven by, the main shaft with a continuous motion. The slot in this pinion is so arranged that once only during each revolution of the pinion does it allow the escape tooth to pass, and when this occurs, the drum, under the action of a driving spring, with which it is provided, makes one full turn, when the escapement tooth, coming round again, rests on the cylindrical portion of the slotted pinion as before. The spindle on which the drum revolves also gears into, and is driven with a uniform motion from, the main shaft, and to this shaft is attached the one end of a coiled spring, the other end of which is fixed to the inner circumference of the drum itself. As the spindle revolves, this spring winds up, and, on the release of the escape tooth and drum, the spring unwinds, carrying both the drum and escape tooth withit. Then the film is passed forward between the winding and unwinding rollers at this point only, with the necessary intermittent motion. The constant uniform motion of the paying out spindle as it unwinds causes a certain uniform length of the film to pass forward toward the exposure screen, when it collects into a kind of loop in readiness for use.’ As soon, however, as the detent tooth attached to the drum escapes through the slot in the pinion, the drum makes a single revolution, and in so doing both removes the exposed film from the screen, and, at the same time, draws a loop of fresh film which has been gathering into the exposed position, and, at the same time, passes forward the exposed film into the form of another loop in readiness to be wound up on the winding roller. “ The shutter is made in two portions, each provided with a slot, which in one position only allows the light from the lens to pass, and it is only by this simultaneous action of these two shutters that any action of light on the film can take place. One portion of this shutter 1s caused to revolve with a uniform motion, the other portion is worked by a rocker, or slide, actuated by a cam ; to this latter portion of the shutter is attached a spring, with a tension screw to regulate its speed.” Transparencies from negatives thus obtained are passed through two lanterns, supplied with suitable mechanism for rapidly placing them in position. By a ‘<cut off” in the rays of light, the one picture is rapidly merged into another, the change taking place during the moment in which the rays of light are cut off. The capabilities of this apparatus were described in the November number of the Optical Magic Lantern Journal, under the heading of “A Startling Optical Novelty,” and from that source was widely copied in the daily and weekly papers, in this country and abroad. Fic, 2.