MOVING PICTURES 



3990 



MOVING PICTURES 



If viewed from th. interior of the 



camera is seen to be divided into two sections 

 by a long, narrow tube which runs through 

 the middle and contains at one end the lens, 

 at the other end an aperture with a screw 

 which serves as the "finder" for the ma- 

 chine. Often there is an additional finder on 

 top of the camera. The back half, upper and 

 is occupied by two zinc boxes containing 

 the spools of film, the upper for unexposed, the 



THI: CAMERA 



The moat modern device of the kind, with pat- 

 en ix granted In 1917. 



lower for the exposed, film. The unexposed 

 film is wound on a spool, and the end runs off 

 this spool and under a guide roller, then under 

 a wheel which is furnished with sprockets which 

 catch the perforations in the edges of the film, 

 to keep it from slipping. Usually there is a 

 spring roller as well, which presses the film 

 firmly against the sprocket wheel and makes 

 slipping impossible. The film then passes 

 through a gate which is just behind the lens. 

 The gate holds the film perfectly flat and 

 steady during an exposure. Below the gate is 

 the mechanism which, by means of claws en- 

 gaging the perforations in the film, jerks it 

 down space by space, as fast as it is supplied 

 by the sprocket wheel. Below this mechanism 

 the film passes under another sprocket wheel, 



then under another guide roller, and finally 

 winds upon a second spool. 



The Shutter. Tho .-hut tor of a motion pic- 

 ture camera is circular, with a triangular open- 

 ing in it. Because the shutter is geared to the 

 same crank shaft as that which feeds the film, 

 its proportionate rate of speed cannot be in- 

 creased. It makes one revolution every time a 

 space of film is exposed. But, since the length 

 of time for an exposure varies with the amount 

 of sunlight, it is essential that the shutter be 

 adjustable. To secure this, it is made in two 

 pieces. If a very brief exposure is needed, the 

 aperture in the shutter is made smaller; if a 

 long exposure is needed, it is made larger. The 

 mechanism which jerks the film into place is 

 also geared to the same crank shaft. This 

 makes the camera very easy to operate. The 

 photographer simply turns the crank handle on 

 the outside of the camera, making usually two 

 turns of the crank in taking sixteen pictures, 

 and the film begins to move, the claws jerk it 

 into place, and the shutter revolves. 

 \ Other Fittings. Most cameras are fitted with 

 a measurer, which registers on a dial on the 

 outside of the camera the number of feet of 

 film exposed. There is a device for punching a 

 hole in the film to mark the end of an exposure 

 to show where one subject finishes and an- 

 other begins; and there is a speed indicator 

 which shows exactly how fast the handle is 

 being turned. 



The Tripod. The tripod used is geared so 

 that it may be adjusted to any level by the 

 turn of a crank; the table of the tripod also re- 

 volves so that the camera may be turned in 

 any direction, and it also tilts at will. The tri- 

 pod is very strongly built, for absolute rigidity 

 is necessary in taking good pictures. 



The Film. All motion picture cameras and 

 all projecting machines use one size of film 

 and take pictures of one size only. All film is 

 one and three-eighths inches wide, including the 

 perforations, and the length of film exposed 

 for each picture is three-quarters of an inch. 

 One foot of film, therefore, contains exactly 

 sixteen pictures. The film may be bought in 

 any length, from 100 to 5,000 feet, but the 

 average camera will contain only 2,000 feet of 

 film at one time. Practically all the film on the 

 market is supplied by a Rochester, N. Y., firm. 



Developing the Film. All cameras containing 

 exposed film are taken to the developing plant 

 of a studio and unloaded in a dark room. Here 

 the film is unwound upon a revolving upright 

 frame, and it stays on this frame while it is de- 



