Abstract
Apart from the well-known loss of color vision and of foveal acuity that characterizes human rod-mediated vision, it has also been thought that night vision is very slow (taking up to 40 min) to adapt to changes in light levels. Even cone-mediated, daylight, vision has been thought to take 2 min to recover from light adaptation. Here, we show that most, though not all adaptation is rapid, taking less than 0.6 s. Thus, monochrome (black-white-gray) images can be presented at mesopic light levels and be visible within a few 10th of a second, even if the overall light level, or level of glare (as with passing headlamps while driving), changes abruptly.
Highlights
Daylight scenes cover the photopic range (10 to 108 cd/m2), in which color is visible, but realworld outdoor night scenes in bright moonlight only span 0.01 to 0.1 cd/m2, scenes under outdoor lighting span 0.1 to 1.0 cd/m2 (Le Grande, 1957), and lit roads reach only 1 to 2 cd/m2 in the carriageway (Ekrias et al, 2008)
Data are plotted as log10 relative thresholds, thresholds for detection shown by diamonds (Ton)/Tabs and turned off (Toff)/Tabs, versus log10 field intensity levels in cd/m2 derived from the original measurements in trolands using Eqs 1 and 2
The data points in those figures represent the amount of logarithmic increase of the tested threshold (e.g., Ton, Toff, and Toff-flash) above the corresponding Tabs, for given background field level
Summary
Daylight scenes cover the photopic range (10 to 108 cd/m2), in which color is visible, but realworld outdoor night scenes in bright moonlight only span 0.01 to 0.1 cd/m2, scenes under outdoor lighting span 0.1 to 1.0 cd/m2 (Le Grande, 1957), and lit roads reach only 1 to 2 cd/m2 in the carriageway (Ekrias et al, 2008). Responses to changes in light level is thought to be sluggish as the rods take 20 to 40 min to fully recover after the offset of a bright light (Hecht et al, 1937; Alpern, 1961; Stabell and Stabell, 2003). It is this latter fact that we wish to addres in this paper
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