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.
474 XIII. PROJECTION AND PROJECTORS
pass a relatively large amount of light and provide a relatively large signal for a photocell actuating the amplifier. The wide slit, however, attenuates the high frequencies appreciably with respect to the lower frequencies. To obtain " balanced" reproduction without excessive bass tones, both variable and fixed amplifier equalization is provided that is capable of suitably attenuating the bass. In selecting slit-thickness and amplifier characteristics, each manufacturer selects what he considers the best compromise for his particular machine and his concept of ' ' average ' ' film quality. In a large number of cases, the basic optical design was accomplished over a decade ago and little significant modification — much less fundamental re-design — has been made despite the fact that raw stock and prints have improved very materially in the interim.
For performance equivalent in response-frequency characteristic to 35-mm performance in a well-maintained neighborhood theater, an effective slit width of 0.5 mil would be required. This value is determined by multiplying the standard 35-mm slit thickness of 1.3 mils by the ratio of the film speeds. Only one manufacturer* (Eastman Kodak) has so far manufactured a commercial sound projector with a slit of this small size. Projector users owe Eastman a debt of thanks for having pioneered in the attempt to accomplish the lens improvement inexpensively in mass production. Most machines were originally designed to provide a slit of 1 mil,f but since chromatic correction was absent, manufacturing tolerances proved wide in practice, and lens inspection in machine assembly was not particularly good, effective widths of l1/^ mils were not unusual. Some lens system modifications proved quite good; an example is Bell and Howell. In their case, improvements in amplifiers and in transport systems made the improvement of the optical system evident in terms of improved sound from the loudspeaker. The lens improvement consisted of a change in the focal length of the cylindrical lens for the purpose of increasing its optical reduction ratio, and/or a change in the size of the small mask at the end of the optical assembly facing the exciter lamp. With all manufacturers, there was a tightening of tolerances, the extent of which varied from manufacturer to manufacturer. Despite these improvements, still further improvement is seriously needed in sound optical and film transport s}rstems; full advantage should also be taken of the recent advances in electronics to reduce the noise and distortion produced in the amplifiers and to widen their frequency range.
* The De Vry and the Bell and Howell Models are not widely available commercially.
t Mil — colloquial term for 0.001 inch.