Red light use cases?

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SammysHP
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Red light use cases?

With the huge positive reaction in the red Sofirn C01R thread I wonder what a use case for red lights look like. I’ve never needed or wanted a red light (except in the lab for photo work). What do you want to do with it? Which activity? Why red and not a low intensity white light?

maukka
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It’s probably the false notion that red light preserves night vision better. Or maybe people just want to experience the exotic deep red emitter.

In my opinion a low lumen white light is always more useful.

firedome
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maukka could explain more of that false notion, until now i have always believed that the red light preserved night vision and was less detectable in the distance.

We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light --- Plato

maukka
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White light can be used at levels much lower than red while still discerning detail let alone color. It is very difficult to get anything done with red light especially at low levels if you need to also make out colors. A Zebralight on its minimum level will not affect your night vision nor is it visible from afar and you can still see with it in pitch black. It is just that historically red lights have been very dim compared to white, because you need to filter a lot of white light to get red, which has perpetuated the belief. I’m not saying that a red light at a similar power level than white doesn’t preserve night vision better, but that’s a whole another matter.

The_Fat_Controller
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good article Here

jch10400
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Use case – I live about 15 minutes from a mountain preserve that does a guided monthly night walk. They only allow red lights on the walk. I use an old 3 AA Maglite with a red lens. It’s the only time I use red.

In their case I understand the red requirement. They have had people show up with everything from 4 D Maglites to hand held halogen spotlights thinking they will use them to look for owls. The red requirement keeps everything toned down.

maukka
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jch10400 wrote:
In their case I understand the red requirement. They have had people show up with everything from 4 D Maglites to hand held halogen spotlights thinking they will use them to look for owls. The red requirement keeps everything toned down.

I’m sure they would change the rule if someone turned up with an Acebeam X80. That red is something fierce. This also boils down to the output, not the spectrum.

spudley112
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Red light use cases?

To mark certain “questionable” districts.

Just kidding..here is another article that is interesting, Red myth.

I was in the military and we used red lights routinely. I lived under the impression that red lights aided in preservation of night vision as well for a long time.

AguassissiM
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Here is another myth (or is it not a myth) about red light.
Some do believe that red light helps while driving at night while others dismiss it as fairy tale bs.
Well I`m a professional freight relocation engineer or as everyone call us a truck driver, in my cab I always install 2 red lights that are on during the night driving. Fairy tale or not it helps my eye strain and overall eliminates my headaches that I used to get before experimenting with said lights. Will this work for anyone else ? some of my coworkers say it does and others keep telling us that we are full of **it .

***Rofis MR70*TurnRaise*Catapult V6*BLF Q8*BLF Mini*BLF Micro*Haikelite MT09R* Convoy C8*BLF D80v2 SST40*MatemincoX6S*AstroluxFT03-xhp50.2*AstroluxFT03-sst40*BLF-LT1*AstroluxFT03S-SBT90.2***

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I don't mean to disagree with maukka but...

Red light does not attract most insects as these are insensitive to this wavelength.

Red light is invisible to a wide range of wild animals (e.g. deers) as their eyes cannot perceive this wavelength.

Red light does not overstrain the human eye as much as white light does due to the absence of shorter wavelengths like blue or green.

g_damian
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Red light can be used for wildlife lighting, e.g. turtles. https://turtlesafeonline.com/

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Switching from adapted night vision to red light/3500K at the the same power, the red light was waaaay less hars and way more pleasant then the 3500K.

virence.com Nichia E21A sw30+sw40 Wizard Pro ; Skilhunt H03 XP-E2 660nm ; Wizard Pro E21A 2000K ; S2+ E21A sw40 d220 ; Sofrin C01R 660nm, Mf01 Mini Nichia 219B sw35+sw40

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SammysHP wrote:
With the huge positive reaction in the red Sofirn C01R thread I wonder what a use case for red lights look like. I’ve never needed or wanted a red light (except in the lab for photo work). What do you want to do with it? Which activity? Why red and not a low intensity white light?

Culling the coyote herd at night. I built a C8 with a red XP-E2 emitter. Doesn’t seem to scare them off like a white light does. I believe they can still see the red light, but see it more as a brown dot. Ideally, thermal scopes work much better, but a good one is in the $2500+ dollar range.

manithree
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Cycling tail lights.

Viperkeeper
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I use it to preserve night vision and not disturb animals. I’ll also use it mixed with UV. The contrast of 660nm/365nm really makes things glow under UV but I can still see everything with the red. Animals eye’s don’t dilate under red light either. So I’ll film animals under red light then I’ll swap to green in post. The results look just like a night vision camera.

Photonica
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manithree wrote:
Cycling tail lights.

Yeah, I need a red tail light when I’m pedalling my a** around town.

Oh dear, that didn’t sound right.

More Photons!

Kalihi
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I used to think that super low moonlight/firefly modes made red lights unnecessary, but back-to-back testing completely changed my mind.

I found that even with the extremely low firefly modes on my ArmyTek headlamps (so low that you can comfortably look straight into the emitter with fully dark-adapted eyes), my night vision still returned faster when I used red lights versus the firefly modes. This still occurred even if I used much stronger red light than white light.

I also found that even on the lowest levels, white light wakes me up if I need to get up to do something in the middle of the night, but with red light, I can go right back to sleep afterwards.

And when visiting the local astronomy club’s field viewing nights (where they require red lights), I was again able to do back-to-back testing, and found that red light kept my eyes more sensitive to minor differences in star color than white firefly mode light.

The advantages of red light for me were so big that camping-style multi-emitter headlamps with red LEDs have almost completely replaced my enthusiast headlamps for nighttime use.

Pavlo
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Red has many advantages, but if constrained solely on preserving night vision, then green is the better choice. The eye at very low light levels is less sensitive to red, and thus more light is needed in red in order to discern a certain level of detail. As with green, the eye is much more sensitive to it at very dim levels. You can hence achieve equal clarity to red with alot less light, and regain your night vision faster.

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When just trying to see the time late late late at night on an LCD clock (black on clear), the lowest red setting of my WK30 is plenty bright yet I can drop off to sleep right after.

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Viperkeeper
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Pavlo wrote:
The eye at very low light levels is less sensitive to red, and thus more light is needed in red in order to discern a certain level of detail. As with green, the eye is much more sensitive to it at very dim levels.

Absolutely, but it’s not about the level of light it’s about how we react differently to red light. You can have high levels of red and your pupils remain dilated and maintain night vision. It doesn’t take much green or blue to ruin night vision. The argument seems to be low level white vs higher levels of red. For me indoors at night low level 2700k, outdoors it’s red. I can see stars, light pollution and the moonlight like never before.

Pavlo
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Viperkeeper wrote:
Pavlo wrote:
The eye at very low light levels is less sensitive to red, and thus more light is needed in red in order to discern a certain level of detail. As with green, the eye is much more sensitive to it at very dim levels.

Absolutely, but it’s not about the level of light it’s about how we react differently to red light. You can have high levels of red and your pupils remain dilated and maintain night vision. It doesn’t take much green or blue to ruin night vision. The argument seems to be low level white vs higher levels of red. For me indoors at night low level 2700k, outdoors it’s red. I can see stars, light pollution and the moonlight like never before.

The level of light does have a direct influence on night vision, regardless of color. If a green light is used at the same intensity as red, then red is by far a better choice. What I am saying is that you can use a significantly lower level of green to achieve the same nocturnal clarity as a higher level of red. With this lower level of green, your eyes will adjust faster to night vision than the higher level of red needed to compensate for the lack of sensitivity in red.

Check the article below, I found it quite helpful in trying to answer the same question.


With mesopic vision, at minimum illumination levels, you will see a slightly greenish tinge of color from white or green objects, every thing else will look gray or black. Remember: If you can see color, then your night vision has been compromised! Since a much greater intensity of red (than green) light is required to see, you are compromising your night vision to a greater degree when using red.

source:
http://www.astromax.org/activities/members/kniffen.htm

cetary
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Here’s a quote from a scientific peer reviewed .edu source. Red very much helps preserve night vision.

“Because the rods are less sensitive to red light, using a red flashlight helps to preserve night vision. “

Here’s another regarding the effects of short-wavelength blue light.

“Blue light, especially at night, can cause more eyestrain and fatigue then other types of light and can cause halos around objects, because short wavelength light makes it harder for the eye to focus. Just as blue light scatters in our atmosphere, it scatters in our eyes as well, impairing night vision. “

The popular XP-L HI 3D would be a poor choice for preserving night vision. The strong blue spike which you can see in the spectral power chart in the upper left, would also make it generate disproportionate levels of offensive glare to those around you who happened to be looking at it. The 2000K E21A ,on the other hand, would be a very sound choice if white light was still insisted upon. This would be because of its pronounced red content and suppressed blue/cyan. There you can see almost no blue spike.

Pavlo
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@cetary

I agree with you 100%. In real life practical terms where most are using an intensity of light high enough to suppress night vision, much better to go with a warmer CCT like that of the 2000K E21A. The minimal blue/cyan will also avoid interference with melatonin suppression. I do suspect that a 2000K led might still be visible by animals and insects.

xenotar80
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Kalihi wrote:
I used to think that super low moonlight/firefly modes made red lights unnecessary, but back-to-back testing completely changed my mind.

I found that even with the extremely low firefly modes on my ArmyTek headlamps (so low that you can comfortably look straight into the emitter with fully dark-adapted eyes), my night vision still returned faster when I used red lights versus the firefly modes. This still occurred even if I used much stronger red light than white light.

I also found that even on the lowest levels, white light wakes me up if I need to get up to do something in the middle of the night, but with red light, I can go right back to sleep afterwards.

And when visiting the local astronomy club’s field viewing nights (where they require red lights), I was again able to do back-to-back testing, and found that red light kept my eyes more sensitive to minor differences in star color than white firefly mode light.

The advantages of red light for me were so big that camping-style multi-emitter headlamps with red LEDs have almost completely replaced my enthusiast headlamps for nighttime use.

That’s really interesting about your experience with dark adaptation with red vs very low white light. I keep seeing people post rebuttals against using red light for dark adaptation. I wonder if it’s across the board or person to person variation.

I personally use either red or 2000K (e21a) at night so it doesn’t jack up my sleep. I usually tend to use the 2000K light since I can see better and it doesn’t have a blue spike like most LEDs. I can blast the 2000K and not have any sleep issues… whereas something like the nichia sw45k (massive blue spike) will screw with my sleep for hours.

zak.wilson
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My experience testing red light versus sub-lumen white is that levels of white that allow me to perform tasks tend to be lower enough than levels of red suitable for the same tasks that it has less impact on my dark adaptation.

There are situations where that’s not the case, like viewing objects with very high contrast (e.g. black text on a white page) or instrument backlighting.

I think something that hasn’t been emphasized enough so far is luminous flux, as opposed to electrical or optical power. The lumen, and its derived units, lux and candela is calibrated to human visual sensitivity. 1 lumen of red light is much more radiant power than 1 lumen of green light. Much of the accumulated wisdom (not necessarily more robust scientific data) comes from decades of experience sticking filters on incandescent lights without dimming capabilities.

As an example, the Lee 106 primary red filter intended for entertainment lighting transmits 12.8% of the light from a 3200K tungsten-halogen incandescent source. I’m not actually sure if the transmission listed is luminous or radiant; if it’s radiant, the reduction in visible light is even greater.

Of course it’s no surprise to anybody that blocking most of the output of a light source mitigates its impact on dark adaptation and reduces its visibility to a faraway observer.

What would be interesting is a test involving extremely low-output light sources with very precise regulation in which subjects are given time to become dark-adapted, then gradually increase the brightness of their light source until they’re able to successfully perform some task, followed by a test of their dark adaptation.

Ceilingbounce – flashlight testing and runtime graphs for Android

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I have some Osram 657nm “hyper red” emitters, when my eyes are dark adapted I can look directly at them (even on high), and it doesn’t reset my adaptation like a normal light would.
Based on that I’d say there’s some truth to it, OTOH you have no idea what any color is so if that matters at all then red isn’t a great choice.
If your goal is to just not trip over something then red is great. IF IT KEEPS THE BUGS AWAY THEN EVEN BETTER!

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zak.wilson
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I put a 660nm LH351H in a Tool AA for a friend to use as a costume prop, but it didn’t occur to me to try staring directly into it. I have another, but no appropriate unused lights to stick it in.

Maybe I should offer it to people who do instrumented tests. maukka? djozz?

Ceilingbounce – flashlight testing and runtime graphs for Android

hank
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Well my gosh, you can grossly overpay for a red LED to treat oral herpes cold sores!

The Luminance RED Cold Sore Treatment Device
$349.00
https://luminancered.com/

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I’ve always liked red light. Whatever the science, it always feels easier on my eyes. It doesn’t spark wakefulness either. I’ve used it for a lot of night activities, including not wanting to wake others while camping, caring for small children, etc. Going back to the last century, my favorite night lights around the house were high-quality 25W red incandescent bulbs. Unfortunately, those have gotten harder to find. I went without until finding some decent red LED night lights here and I had almost forgotten how much I love it around the house at night.

Deep red is even better. Sure, I might not be able to see the full output but I love what I can see. It’s pretty and almost magical. If it’s also good for my vision, even better. That little Sofirn has left me wanting it with more power. I’d love to see deep red choices in either 18650 or 21700 from Convoy, especially with the mode freedom of Biscotti.

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