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This deals with experiments, conducted over a period of months on six persons, measuring with the aid of a photometer the frequency of flicker. For the examination, a machine was made from a circular disk with a section removed. This disk was rotated before a known source of light until the impression of a continuous line or complete circle of light was seen by the subject. The critical frequency was noted in flashes per second needed to produce fusion, "a rise" being an increase and a "fall" being a decrease in the number of flashes per second. Measurements were made to determine the brightness of various parts of the spectrum and reaction of the eye when dark-adapted. To secure known intensities of illumination, the patient was placed in a cubical space whose walls measured 152 cm. and contained a square opening subtending an angle of 1 degree at his eye
The Adaptation of the Eye: Its Relation to the Critical Frequency of Flicker. Reports of the Committee upon the Physiology of Vision.. JAMA. 1930;95(9):685. doi:10.1001/jama.1930.02720090047030