Originally posted 5 Sep 13.
So, which kind of light should you use at night? Most folks, including me, were raised on red lights at night. But as to the effectiveness of red light, it’s basically a myth that most likely started in a photographic dark room. Until about 1906, most photosentive material (plate, film and paper) was not very sensitive to red light. This insensitivity allowed these materials to be deal with for a relatively short time under a relatively bright red light. This was important to the vision of the photographers, because the human eye can see red if the level is bright enough. Much later, when L.E.D.s came on the scene (having a number of advantages over other light sources), they were economically only available in red for some time, and that has also helped to perpetuate the myth that red light is best.
As more research was done on the eye and how it sees, it was found that the rods (the structure responsible for low light vision) were also not very sensitive to red. It was assumed that like film, you could use red light, which is seen by red sensitive cones (there are also blue and green sensitive cones to give color vision) without affecting the rods.
The main issue in what is seen is the intensity of the light. Color is only an issue because the rrods (responsible for night vision) are most sensitive with a particular color.
And it’s not red.
It’s actually a blue-green (507nm) which is very similar to traffic light green or “TLG”(chosen for traffic lights for an entirely different reason, but I won’t digress).
Advantages of TLG:
– Blood is much more easily seen in TLG light, especially after it’s been exposed to oxygen. It is not so visible in red light.
– TLG does not make all red ink on maps and documents disappear when viewed with only red light.
– TLG does not damage night vision (ie, destroy visual purple).
So, consider getting yourself a TLG or bluish green lens cover for your flashlight. Do some experimentation with it. You’ll most likely find you have a new favorite night light color.
Now that we know what kind of light is best to use in low light, what can you do to become more adept at seeing at night?
Here’s a few techniques to maximize your night vision capability:
– Prepare to operate in darkness before doing so. Sit in a very dark room with little to no light whatsoever for 45 minutes to an hour before emerging into the darkness.
– While you’re in the dark waiting, you can perform a few simple exercises to reduce any eye strain you might have:
– Close your eyes tightly for 3-5 seconds then open them for the same time length. Do this 7 or 8 times.
– Sit and relax. Roll your eyes clockwise, then counter-clockwise. Do this half a dozen times and blink between each repetition.
– Focus on a distant object that you can make out in the dark room. If you’ve emerged in the dark already, focus on something 50m away for several seconds and then slowly refocus your eyes on a nearby object about 10m away . Do this about a half a dozen times.
– NEVER look directly at an object. It will disappear on you.
– Look above, below, or right or left of an object.
– Get below what you are trying to see. Employ a ‘false horizon’ (strip of dirt, stream, asphalt road, trail, or anything that appears as a band/single shade back drop).
– If you think you’ll need your night vision for long periods, use standard binoculars over NVD’s. Once you use the NVD, you’ll be ‘blind as a bat’ in the eye you used until your eyes develop visual purple again. Trust me on this.
– Eye protection works. Get some good non-fog clear lenses. Not yellow. They don’t help you. Try to make sure they don’t affect your depth perception.
Next time: Maximizing Night Vision by Combining the Senses