We use Optical Character Recognition (OCR) during our scanning and processing workflow to make the content of each page searchable. You can view the automatically generated text below as well as copy and paste individual pieces of text to quote in your own work.
Text recognition is never 100% accurate. Many parts of the scanned page may not be reflected in the OCR text output, including: images, page layout, certain fonts or handwriting.
CH. XI]
MOVING PICTURE FILM AND MECHANISM
417
The essential part of the mechanism consists in three sprocket wheels, a, b, and c, (fig. 231), the two wheels a and b move continuously at the average rate at which the film is passing (30 cm., i foot, per second), and serve to unwind the film from the upper reel F and feed the film to the take-up reel G at a uniform rate. The sprocket wheel c, located between the other two, is intermittent in its movements, being stationary for about % of the time and being in rapid motion for about J"6 of the time. The effect is, that after the film has been in position for exposure on the screen this sprocket wheel jerks the small section of film between L and M forward to the next picture. In fig. 232 is shown one form of mechanism for causing the intermittent movement of the sprocket wheel.
When the film is stationary it is projected on the screen by the objective, but during the short time when the film is in motion a shutter either before or behind the objective cuts off the light and prevents any blurring due to the movement of the picture.
The films are made in such a way that if the pictures are right side up, the later picture will be below the earlier ones, but as in passing through the machine the pictures are upside down, the later pictures are above and it is necessary to move the film downward to bring the pictures on .fiMMtfAtefc*, the screen in due order.
§ 584. Threading the film in the machine. — The film as wound on the reel usually is wound in the correct direction, so that the first pictures are on the outside. If this is not the case, the film must be rewound on another reel to reverse its direction. If the direction is correct the pictures will be upside down when the film is in
FIG. 232. INTERMITTENT MOVEMENT the machine, that is, when the
OF POWER'S No. 6 CAMERAGRAPH. ,-•, • -, -, c
,,, , , , , ., ... , , „ film is passing downward from (L ut loaned bv the Nicholas Power
Company). F (fig. 231).