An inadequately designed display viewed in the dark can easily cause
dazzling glare and affect our night vision. In this paper we test a
display design in which the spectral light emission is selected to
reduce the impact of the display on night vision performance while
at the same time ensuring good display legibility. We use
long-wavelength light (red) that is easily visible to daylight
vision photoreceptors (cones) but almost invisible to night vision
photoreceptors (rods). We verify rod-cone separation in a
psychophysical experiment, in which we measure contrast detection in
the presence of a colored source of glare. In a separate user study
we measure the range of display brightness settings that provide
good legibility and are not distracting under low ambient
lighting. Our results can serve as a guidelines for designing the
displays that change their color scheme at low ambient light levels.
Discussion and Conclusions
In this paper we showed that a display that emits long-wavelength
light (red to amber) offers several advantages over green and blue
displays that are used under low ambient light. A red-colored display
affects visual performance due to disability glare the least as it is
the least likely to cause dazzling or eye aversion, even if emitting
light at high photopic luminance levels. Other studies indicate that
red colored letters are the most legible at low luminance levels. Our
second experiment showed that a display in dark environments must emit
at least low photopic luminance levels (~20 cd/m^2) to be
comfortable to read, and higher luminance (~40 cd/m^2) if
displayed content, such as maps, requires distinguishing between
several brightness levels.
