Night Vision - Why red light does not affect our night vision.
The human eye contains two types of receptors, the rods and the cones. Rods and cones have an increased sensitivity to frequency bands at different ends of the visual spectrum.
Rods are largely responsible for our day time and colour vision and have an increased sensitivity towards the red band of the visual spectrum.
Cones are responsible for our night vision capability and have an increased sensitivity towards the blue, shorter wavelength band of the visual spectrum.
For this reason red light will not affect the sensitivity of the cones and with that our night vision is not affected by the use of red light in the cabin.