Modified from Figure 1 of Stockman A. & Sharpe L.T. (2006). Into the twilight zone: the complexities of mesopic vision and luminous efficiency. Ophthalmic & Physiological Optics, 26, 225-39.
Illumination levels. Typical ambient light levels are compared with photopic luminance (log cd. m-2), pupil diameter (mm), photopic and scotopic retinal illuminance (log photopic and scotopic tds, respectively) and visual function. The scotopic, mesopic and photopic regions are defined according to whether rods alone, rods and cones, or cones alone operate. The conversion from photopic to scotopic values assumed a white standard CIE D65 illumination. (Based on a design of Hood and Finkelstein, 1986.)
Hood, D.C., & Finkelstein, M.A. (1986). Sensitivity to light. In: K. Boff, L. Kaufman, & J. Thomas (Eds.), Handbook of Perception and Human Performance, 1 (pp. 5-1-5-66). New York: Wiley.
Stockman A. & Sharpe L.T. (2006). Into the twilight zone: the complexities of mesopic vision and luminous efficiency. Ophthalmic & Physiological Optics, 26, 225-39.