ABSOLUTE JUDGMENTS OF LIGHT INTENSITY

The assumption was made that absolute judgments of luminance could be made providing the eye remained in a relatively constant state of dark adaptation during the judgmental process. This hypothesis was tested by presenting each of twelve naive subjects with a preselected, random series of five stimuli which ranged from stellar magnitude 2.30 to 5.33. Each subject made 200 judgments at the approximate rate of three per minute. Results indicated two stimuli lying about 0.90 steller magnitudes apart were confused, but near certainty of discrimination occurred when two stimuli were separated by approximately 1.40 steller magnitude.