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.
1949 HIGH-SPEED PHOTOGRAPHY 445
is activated. In measuring the length between the pips from the beginning of one to the beginning of the next with the 60-cycle pulse the time interval will be &l/a milliseconds. However, with an unaged lamp, it is necessary to measure from the beginning of one pulse to the beginning of the second pulse from the first one and consequently this measurement is 162/3 milliseconds.
The Potter Instrument Company of Long Island City has built an oscillator which will furnish 1000 pips per second for operating up to 14 high-speed-camera timing lamps simultaneously. This oscillator used a 100-kilocycle crystal control and the timing circuit is then derived from breaking the 100,000-cycle output of the crystal to 1000 through two decade reductions. This oscillator can be operated from either 60-cycle or 400-cycle, 120-volt circuits. The 400-cycle circuit permits using this equipment in aircraft.
It has been observed that the human eye and brain cannot assimilate many actions going on simultaneously upon a screen. Therefore, in taking high-speed pictures the primary rule of photographic composition is to make the picture as simple as possible by confining the subject under study to one of its component actions rather than the subject as a whole. If, for example, a calculating machine is being photographed, individual springs, cams, locking levers, and similar devices should be photographed separately rather than attempting to make a high-speed picture of the whole unit at once. Greater magnification is obtained when the single subject is photographed. If possible, there should be some color contrast so as to delineate the actions as they occur from static or stationary parts.
Then comes the problem of lighting this in the laboratory. Formerly, the lights used for high-speed photography were quite bulky; 750-watt, 2000-watt, and 5000-watt lamps in reflectors have been employed. As a general thing a spherical reflector was placed back of the lamp so that the image of the filament would be projected on the subject. There were other cases, however, in which reflectortype lamps were used such as the RSP-2 750-watt photospot, airplane landing lamps (for portable use in planes), and 150watt show-window spots when burned at 220 volts after preheating. The older type lamps as mentioned above have been extremely effective for lighting small subjects or when banks of them were used for lighting subjects up to roughly 24 by 24 inches. Most high-speed-camera subjects fall within this field. When using the lamps mentioned above, particularly the 750-watt and 2000-watt setups, lamps were secured