Visual Performance Data for 156 Normal Observers of Various Ages
Data is presented on the visual performance potential of 156 "normal" observers from age 23 to 68 years. Data from the experiments presented show the large differences in visual performance capability both among individual observers of the same age and between the averages of different age groups. These observers represent the optima of the age groups studied and not the average of the population as a whole, since all observers with discernible ocular defects and those with visual acuity less than 20/30 were eliminated.
The results of the main study taken in conjunction with the results of a special supplementary experiment provide a new assessment of the factor for common-sense seeing, a contrast multiplier used to convert from laboratory forced-choice threshold data to thresholds corresponding to more ordinary criteria of just barely seeing. The value derived from the present work is 2.39, which is in agreement with the value of 2.40 reported by Blackwell in 1959.