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.
352 SOUND MOTION PICTURES
ent intensity into an image. These must be reassembled or composed in the same order and at the same speed that obtained at the transmitting end.
Although the eye is a very remarkable mechanism in many respects, it is faulty in that it has what is known as "persistence." This means that the electro-chemico process taking place in the nerves and the brain as a result of a stimulus on the retina persists for a brief time after the stimulus has been removed. Persistence lasts for about one tenth of a second; so if a series of stimuli are applied at that interval the result will be, not a broken, but a continuous reaction. It is this defect that makes possible motion pictures and television, since the illusion of motion is produced by sending a series of pictures, each of which is a "still," at the rate often or more a second.
To make the illusion more perfect, more than ten images should be completed every second, and from fourteen to sixteen are found to give almost perfect results. For reasons which will become clear as we progress, the lowest possible number is taken both as the minimum and as a value that will be satisfactory for television in its present imperfect stage.
We noted above that the disk with forty-eight holes produced an image with 2,304 dots. Having also concluded that ten images should be sent each second, it follows that 23,040 dots a second are required. This is equivalent to a requirement of 23,040 electrical impulses of varying intensity every second. What we have here, then, is analogous to the problem of transmitting an orchestration in which the frequencies extend up to 23,040 cycles a second, or considerably above the audible range for the average person. When it is realized that modulating frequencies of even 5,000 cycles, and even the average audio-frequency amplified seriously, discriminates against frequencies above 6,000 or 7,000 cycles a second, the