136 



Popular Science Monthly 



it is shifted by the cyHnder-pins. The 

 box or case for the mechanism should he 

 about 12 in. in height and 33^ in. wide, 

 the length from front to back being 

 determined by the focal length of the 

 lens. 



If it is desired to take an extra-long 

 film at one time the box can be made 

 higher to contain larger rolls. The 

 cylinder is supported by axles J, J, 

 which pass through holes bored in the 

 sides of the camera-box at the proper 

 points to bring the cylinder to within 

 1/16 in. of the film. To one of the axles 

 is attached a pulley i in. in diameter, 

 belted to the drive-wheel with a belt 

 stretched fairly tight. The drive-wheel 

 is made in two sections of different 

 diameters, which are fastened together 

 to form one wheel, the outside section 

 of 8 ins. diameter being belted to the 

 cylinder, and the other section of 4 ins. 

 diameter being belted to the i-in. pulley 

 connected with the take-up roll at the 

 bottom. 



The camera-box has an aperture i in. 

 high and 1 3^ ins. long cut in the back, to 

 afford passage for the pins when pulling 

 the film, and to allow using the machine 

 for projecting the pictures. When used 

 as a camera, the opening is made light- 

 tight by the pivoted cover H. This is 

 opened to allow the light to be projected 

 on the film when used for projecting the 

 finished pictures. 



The camera-lens may be of any con- 

 venient focal length. It is mounted in 

 a hole cut in the front of the box, 

 opposite the hole in the cylinder. The 

 lens should be mounted for shifting it 

 backward and forward to obtain the 

 proper focus of the image, as observed 

 on the film through the aperture at the 

 back of the camera. The camera-box 

 must be made light-tight. 



Now load the camera with the sen- 

 sitized film. This must be done in a 

 dark room, with only ruby light. This 

 film can be obtained already perforated 

 from any dealer in photographic supplies. 

 The film is passed behind the pressure- 

 guides and the cylinder-shutter, as 

 shown in the illustration, with the dull 

 or film side toward the lens. It is 

 fastened to the lower take-up shaft by 

 means of a thumbtack, after which the 

 camera is closed. When taking the 

 pictures, the camera should be supported 

 on a table or some other rigid surface. 



The driving-handle, attached to the 

 driving-wheel, is turned at a speed of 

 two turns per second, making sixteen 

 pictures per second, or eight pictures 

 per turn. 



After the film is exposed it is ready for 

 development, which is accomplished in 

 the same manner as the development of 

 ordinary films, except that an arrange- 

 ment for handling such a long film is 

 necessary. 



Make a square wooden frame to fit 

 inside the developing-trays used, which 

 should be at least 14 ins. by 17 ins. in 

 size. The film is wound around the 

 frame with the emulsion or dull side 

 outward and is then easily handled in 

 the developing solutions. The film is 

 left on this frame for all manipulations 

 until dry, when the negative is ready for 

 the printing of the positive film. In the 

 dark room, wind up the negative and 

 an equal length of positive film into a 

 roll, with the emulsion sides in contact. 

 The two films are then passed through 

 the camera together in the same way the 

 original film was passed through in 

 taking the pictures. 



For printing, the lens is removed from 

 the front of the camera and the camera 

 pointed toward a bright light. The 

 camera handle is turned at the proper 

 speed to give a correct exposure to the 

 positive film. The correct exposure is 

 best determined by making short ex- 

 posures on a few inches of film, until the 

 right effect is obtained. Then the full 

 length is printed in the same way. 



The positive film is developed in the 

 same way as the negative. After wash- 

 ing and drying, it is ready for projection. 

 The finished positive film is placed in 

 the camera, with the pictures upside 

 down and the dull side toward the back 

 aperture, which is opened. Through it, 

 the light from a stereopticon, or some 

 other form of brilliant illumination, is 

 projected on to the film. The picture is 

 then focused on a screen placed in front 

 of the camera-lens. The pictures are 

 projected by turning the driving handle 

 at the same speed that was used when 

 taking first them. 



If a very brilliant light is used for 

 projecting the pictures it is necessary 

 to cover the film when it is not running 

 through the camera, as the film is in- 

 flammable and will quickly catch fire 

 from the heat. 



