["Red light in itself does not preserve night vision."
"If you go for a brighter light it does not matter if it's red green or blue it will still affect your night vision."
Additional comments supported this view.]
The information this is based on is somewhat misleading.
Red light does not completely protect your night vision at any lumens output, but it does preserve much more than white light of the same lumens output. Just about any colored light, will preserve more than white light, but especially red or violet. The human eye is more adept at seeing in the yellow / green colors of the spectrum. Using red light preserves much more of your natural ability to see detail in dim yellow / green light.
Yes, the brighter it is, the less the protection.
Yes, the deeper the red, the more night vision protection you get.
If someones eyes are more comfortable with red light when waking up for a bathroom break (terrain permitting), for reading, or they want to have as little effect on others peace and darkness as possible when roaming around or setting up camp after dark, a red light is definitely the way to go. The dimmer, the better.
The noticeable effects of night vision are diminished more as the surroundings get brighter. Ie: the full moon making the night scenery brighter; near by white light sources contaminating the darkness with light pollution
Red light does have its inherent benefits. However, hiking with a red light to lead the way would definitely require a much higher lumens output to safely light the way, thereby reducing the benefits a good amount. It also would drain the battery quicker because of the higher lumens output. Yes, red light does cut through fog better than white.
One final note on the effectiveness of red light: People as we age, become naturally more night blind which reduces the positive effects of red light use. There are many people that are what's referred to as "night blind" to the point where they're not permitted by law to operate a vehicle after dark. They have extreme difficulty seeing in the dark, as well as having problems adapting to the dark again after oncoming headlights flash in their eyes. Just an example of the extreme end of this scientific fact.
Within astronomy, you'll see a nebula as a hazy grey smudge of light. Increase the aperture of the telescope (bringing more light to the eye), and you'll start to see hints of green and yellow. Increase it enough and you'll start to see other colors as well. The visual colors at the far ends of the spectrum are the last to be seen. That is why the dimmest, deepest red light is used when setting up after dark, and for star chart / map reading. It preserves as much yellow / green seeing ability as possible.
These principals are well understood and documented within the U.S. Military and the international astronomy community.
(Delmar) It sounds as though the eye expert gave you a very general view, rather than breaking it down into all of the variables. He's not wrong, just incomplete with what you were told. You also stated that there isn't really a need for hikers to preserve their night vision anyway.
I agree. In most scenarios out in the wild, there isn't a need. But, for astronomy, seeing fine detail in the dark, reading, and not bothering your neighbors in camp, there are benefits to a red light.
Example: In Colorado, I heard a Marmot playing near my camp at night. I snuck up close enough in the dark to take some photos with a telephoto lens. I was able, because of using my red light about 20 minutes earlier (instead of white), to see it enough in the dark and frame the image. Then with the infrared auto focus assist, I was able to focus in the dark and get my shots. It turned out that there were a pair of them playing on a rock outcropping in the dark.
(Bob Gross) Yes, covering the lens with red cellophane works. Just make sure that the cellophane is thick / dark enough to give the desired effect. It's what I do with my Black Diamond Gizmo headlamp.
One more benefit of red light: Stealth camping. A person would have to be roughly 2 times closer to see your red light as opposed to your white light of the same lumens output. An other Military proven fact.
My personal experience with this: more than 13.5 years military need for stealth (mainly infantry), 36 years of astronomy.
The point is, red light is not necessary or desirable for most, but is helpful and very necessary for some. If you like it / need it, don't let anyone talk you out of it. If you don't like it / need it, don't let anyone convince you that you do.
