I’ve heard it was because red light waves don’t travel that far, but I can see the red light on an airplane wing that’s miles away.
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Greetings from /r/flashlight.
First of all, “tactical” flashlight doesn’t have a fixed definition – it tends to be more of a marketing term. Most lights marketed as “tactical” don’t have a red LED or include a red filter.
We do see a number of posts from people in various armies asking for lights with red capability though, usually because someone well above their pay grade has mandated it for reducing observability. Oddly, there doesn’t seem to be any limit on output or intensity most of the time, and someone looking upon [this](https://i.imgur.com/4mVvg0b.jpg) from a mile away would easily be able to tell someone is using a light source.
There’s also a perception that red light doesn’t ruin dark adaptation. It’s half-true: at similar intensity, red light will have less impact than white, but it’s harder to see what you’re doing with red light, so it kind of evens out. I’d make the same argument for observability: the most important factors are to use as little light as possible, and avoid pointing light sources directly toward where an observer might be.
Much of this doctrine was likely developed long before the advent of modern LED-based flashlights, which can support dimming between a hundredth of a lumen (literally thirty times dimmer than a firefly) to over a thousand (car headlight). A red filter substantially reduces the brightness of a fixed-brightness white light.
I was adding to the other posters. A tactical flashlight is meant for situations where you want to see without being seen. It gives enough light for you to read a map by, but allows you to get closer to an opponent without him seeing you do it.
The airplane light would be even brighter without the red cover so you’d see it even farther away. The red and green lights are so you know which direction it’s moving.
Red light is less harsh on the eyes after you have adjusted to the dark. Some folks argue green could potentially be better.
To not mess up your natural night vision. Also, I believe it doesn’t show up on night vision/IR.
Tactical is something of a marketing term, so can be used in many different ways to sell a flashlight…
The red lenses however, are used for a specific reason, which is preserving somebody’s night vision.
The human eye takes time you adapt to changing light levels – when you turn off the light in a darkened room for example, at first you can see nothing, just blackness. But if you wait for a moment your eyes will adapt and you will start to see some detail.
What this means is if you are somewhere dark, it might be preferable to let your eyes adapt to the darkness to see, rather than using a torch – this means you can see everything, rather than just the little spot that the torch points at, and it is much harder for other people to see you.
This is a problem however if you need to do something specific like read a map – if you turn on a white light it ruins your night vision, and when you turn off the torch your eyes will take time to as adapt again. The way the human eye works, it is less sensitive to red light than the blue/green light that makes up white, so while a white light ruins your night vision, a red light will not – so using s red torch will let you read a map or do a tall you need to see, while still preserving your night vision.
Generally this is considered as a ‘tactical’ thing as it is often used by the military as a way to operate in the dark more efficiently, and less likely to be seen by the enemy.
It’s primarily to preserve night vision. It takes the eyes a half hour or more to be fully dark adapted. You can easily observe this after you turn out the lights to go to bed. Your bedroom seems completely dark at first. Then you slowly start to see things again. After a long enough time you can once again basically see everything in the room.
Every time you look at a bright light your pupils reduce again and the process starts all over. The optic nerve isn’t as sensitive to red light though, so your pupils remain dilated, preserving your night vision.
I do amateur astronomy. It’s a standard practice in astronomy to use only red light in the field. They are looking at extremely faint objects. Want to make enemies quickly at a star party? Pull up in your car with your headlights on.
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