Led Flashlights And Night Vision

By Tom Huntington

The best way to view the world at night is with bright, clear, white light, right? Whether maneuvering around a campground, looking for a lost pet, lighting one´s path for trick-or-treating, or for any other activity that requires light at night, using LED flashlights with white lights seems to be the logical lighting solution.
So why is it then that many fishermen, hunters, and military personnel prefer NOT to use white LED flashlights light while navigating at night? Well, in reality, that white light isn´t really helping our vision, it´s destroying our natural night vision. Understanding the mechanics and biological processes behind human vision will help explain why the use of LED flashlights with white light is sometimes avoided at night.
The Workings of the Human Eye
The way a human eye works can be compared to how a camera operates. Both control the amount of light that enters so that there is a clear exposure for the incoming image. The camera records this image on film, but the eye has a slightly more complex system.
Light journeys through the cornea, pupil, the lens, and the jelly-like vitreous humor tissue until it reaches the retina. The retina is a layer of tissue located at the back of the eyeball and is made up of millions of light-sensitive cells called rods and cones. Cones will pick up on color and detail mostly in the daytime. Rods will focus on monochromatic vision in more low-light conditions.
Upon coming in contact with light, the rods and cones send electrical signals to the brain via the optic nerve. Once the brain has translated these light signals, we are able to view the world (our equivalent of the image being recorded on film).
Rods and Your Night Vision
Night vision is produced by chemicals in the rods called rhodopsin. Rhodopsin, a biological pigment that is highly sensitive to light, molecules change shape when they absorb light and this process results in the detection of light.
Ever wonder why it takes time for your eyes to become accustomed to the dark again after being exposed to bright light, such as from an LED flashlight? Well, this happens because those rhodopsin molecules take time (usually around half an hour) to retain their night vision shape after the eye is exposed to bright light.
The light spectrum where rods and cones are more sensitive is also another interesting component of the inner-workings of the human eyeball. On one side, the yellow-green section of the light spectrum, cones are more sensitive, hence why newer crosswalk signs are a bright yellow-green color so that they can stand out to drivers. On the other side, the blue-green section of the light spectrum, rods are more sensitive. So, colors such as red are harder for rods to pick up on. Hence why many outdoorsmen prefer using colored LED flashlights instead of white in order to preserve and protect their night vision.
Preserving Your Night Vision
Now that you have a better idea as to what some of the inner-workings of the human eye are, it´s time to choose the best LED flashlight for your night vision needs. Though most people choose LED flashlights that mimic daylight due to being more comfortable in the day time (and our cones can pick up on both color and detail), it´s time to think about what flashlight is best for your night vision.
There are LED flashlights that can emit yellow-green, blue-green, or red light, and even a type of LED flashlight that can contain all three of those light options, plus white light.
It may be difficult to choose which color spectrum to have with your LED flashlight, so think about the usage of this flashlight.
-Red light is great for when you want to use as little light as possible (rods cannot detect this kind of light which makes it great for maintaining your night vision).
-An LED flashlight emitting yellow-green light is great for when your need to read a color map (cones will be able to detect the colors and details more easily). If you are concerned about protecting your night vision, cover one of your eyes while using the yellow-green light.
-Blue-green light is great for using as little light as possible and detail is not necessary to see.
Now that you know a little more about how the human eye and night vision work, perhaps you will choose an LED flashlight that has a few more options than just white light.

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About The Author
For more information on selecting, using, and maintaining LED flashlights or headlamps, visit the website for Coast Products, a Northwest manufacturer and distributer of high quality LED lights, at www.CoastPortland.com.