Seasonal Changes in Scotopic Sensitivity

Abstract

The scotopic sensitivity of three subjects was tested weekly over the course of a year. In addition, two measures were made to indicate each subject’s amount of exposure to sunlight. Scotopic sensitivity was found to be poorest in the summer months, when exposure to sunlight was greatest, and to increase gradually during the fall and winter. The course of sensitivity over the year agreed well with the external measures of exposure to sunlight, the best single measure being the amount of “blue” light reflected by the skin.