Kestrel 3500NV Pocket Weather, Olive Drab
Military personnel and pilots flying in darkness are often
concerned with preserving their night vision. Due to overwhelming demand from
our military customers, the Kestrel NV line was added in 2005.
The NV model has the same features as its more colorful
counterparts, but is olive drab with a night-vision preserving backlight which
helps users to sustain natural night vision. The NV's backlight incorporates an
optical filter to reduce overall brightness and minimize blue and green spectrum
light to preserve night vision. Additionally, NV backlights are also much dimmer
than a standard backlight, making it more difficult to detect with the naked eye
in night operations. This backlight appears soft greyish pink, not red, and is
still in the visible spectrum, so is not compatible with night-vision equipment.
It takes 30 to 45 minutes for the average eye to adapt to
darkness and maximize night vision. Even a short burst of white, yellow, green
or blue light “bleaches out” the rod cell photoreceptors in the eye and causes
night blindness until the entire adaptation process can take place again. Light
in the red spectrum does not cause this “bleaching out”, preventing night
blindness and night vision fatigue.