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.
4
LOG HELD BRISHTNESS, B (/iL)
observer in a motion-picture theater, we are able if his adaptation level is known to find to what extent any area may be illuminated without producing glare, to compute the amount of general illumination which may be tolerated on the screen without producing a perceptible degradation of contrast, or to specify the maximum of brightness difference in the field of vision if undue eye fatigue is to be avoided.
In order to make such useful application of the fundamental data contained in the sensibility curves, it is, however, necessary to know the .adaptation level of the observer under the particular conditions considered. Unfortunately the data necessary for this are not at present available. It will be recalled that the "adaptation level" is defined as specified by the brightness of a uniformly illurninated field filling the entire field of vision, and the retinal sensibilities were determined under such conditions. Now it is probable that the brightness of the foveal image is the most important factor in fixing the adaptation level of the retina, but undoubtedly the brightness of the images outside of the fovea have some influence. In the case of a person watching a motion picture, the picture itself occupies but a relatively small portion of the visual field, and in case the surrounding areas are very low in brightness his adaptation level will probably be somewhat lower than indicated by the average picture brightness. The effective application of the sensibility data, therefore, depends upon a reliable determination of the adaptation level under practical working conditions in the motionpicture theater. An instrument is at present being developed with which the adaptation level of the retina when stimulated by nonuniform fields may be measured. It is hoped when such measurements are available that the application of the sensibility data will
85