Abstract
This study investigated the effects on foveal dark adaptation of series of alternating light and dark periods. The purpose of the study was to determine the duration of dark period necessary to avoid the cumulative effects of successive light periods on foveal adaptation. Absolute brightness thresholds were measured monocularly. The test patch which subtended 1 deg diam, and the pre-exposure which subtended 37.5 deg diam were centrally fixated. Foveal dark-adaptation curves were obtained after 10 and 25 presentations of each of the following light and dark period combinations: (1) 1 ft-L for 10 sec with dark periods of 0, 10, and 25 sec, (2) 10 ft-L for 1 sec with dark periods of 0 and 10 sec, (3) 0.1 ft-L for 10 sec with dark periods of 0, 10, and 25 sec, (4) 1 ft-L for 1 sec with dark periods of 0 and 10 sec, and (5) 0.1 ft-L for 1 sec with dark periods of 0 and 10 sec. Curves were also obtained after single presentations of each light period. In most cases, the longest dark period duration tested appeared to minimize or cancel any cumulative effects of the repeated presentations.
© 1960 Optical Society of America
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