Red light use cases?

cetary · 2019-10-27T21:52:24.000Z

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 · 2019-10-27T21:58:55.000Z

@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 · 2019-10-27T22:13:46.000Z

Kalihi:

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 · 2019-10-28T02:08:15.000Z

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.

bansuri · 2019-10-28T02:55:39.000Z

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!

CLB · 2019-10-28T03:07:12.000Z

RobertB:

Culling the coyote herd at night.

Why?

projectcoyote.org

PC_SAB_Coyote-Facts_FINAL_2.5.19.pdf

1204.09 KB

Scientific American

Why Killing Coyotes Doesn't Make Livestock Safer

There is no clear evidence that lethal control works to reduce human-predator conflict. It can even make the problem worse

etc.

zak.wilson · 2019-10-28T03:18:39.000Z

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?

hank · 2021-04-01T17:02:27.000Z

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

Luminance Red

New Treatment For Cold and Canker Sores - LuminanceRED.com

Luminance RED is an innovative LED device that delivers medically-optimized wavelengths of light. Money back within 6 months if you don't see improvements.

Chronovore · 2021-04-26T10:32:56.000Z

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.

Quadrupel · 2021-04-26T10:44:46.000Z

People using red light ,because they newer had a flashlight with moonlight.

jon_slider · 2021-04-26T12:56:01.000Z

hank:

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

thanks for the link it says:

“It has a stated power of 110mW/cm2 (milliwatts / cm squared) and a wavelength of 660 nm (nanometers). A 90 second treatment session delivers 10.0J of energy (a clinically proven, effective dose). ”

Im glad to see confirmation that the 660nm Red for 1.5 minutes speeds up healing of surface wounds…

can somebody translate the 110mW/cm2 to lumens?
or convert the output of the Sofirn C01R to mW/cm2?

gravelmonkey · 2021-04-26T14:22:47.000Z

Interesting thread, I think it’s one of those subjective things.

I’m not really a fan of my CO1R, I don’t get any of the positive feelings that are described here, I find it quite harsh and makes me feel uneasy, a bit like 2001 Space oddessy scenes lit in red…

Definitely prefer warmer tints, 5000k to 4500k to 4000k and lanterns at 2700k with me wondering what even warmer would be like Timeframe is early 20’s to early 30s, so I don’t think I can put it down to age

jon_slider · 2021-04-26T14:43:16.000Z

gravelmonkey:

makes me feel uneasy

I feel the same way about using Red light for looking At things…
dont like it at all

otoh, I use red light on sore muscles and pimples. I like that the inflammation and pain go away more quickly when I use Red Light Therapy.

Vegas_LED_Fan · 2021-04-26T15:08:31.000Z

Here is a picture of a red emitting T6 flashlight mounted on the rear frame of a recumbent trike using a “360 degree flashlight holder” designed specifically for 18650 powered flashlights. This one has both a steady and flashing light with an output of about 800 lumens. The advantage over a bike store light is obvious. You can switch batteries in an instant. You select the battery instead of not knowing what the manufacturer used. It’s way cheaper than any 800 lumen bike light. The flashlight was $12, the flashlight holder currently priced at about $3, and a Panasonic 3,400 mAh battery about $6. Most commercial bike lights don’t allow you to change the batteries and if they do, the OEM batteries are way overpriced.

gravelmonkey · 2021-04-26T17:05:13.000Z

MoreLumens:

gravelmonkey:

Interesting thread, I think it’s one of those subjective things.

I’m not really a fan of my CO1R, I don’t get any of the positive feelings that are described here, I find it quite harsh and makes me feel uneasy, a bit like 2001 Space oddessy scenes lit in red…

Do you have the stock optic in it? Could just be a bit too bright, you know. At least that’s what bothers me most, but soon trying different optics which just might make it a bit dimmer/less hotspotty when using it to illuminate objects close to you.

It does have stock optic, but ceiling bounced, the effect is even more uncomfortable, perhaps it’s just the nature of (almost) mono-chromatic light that I don’t like, I should order some other wavelengths to test

Hank33 · 2021-04-26T17:58:20.000Z

I tend to use green light at night more nowadays. Seems I can read better under green light.
Green also allows for differentiation between colors that red does not and the magenta used on aviation charts, for example, is readily readable under green light, not always the case with red.

puglife2 · 2021-09-02T18:12:57.000Z

For spooky night walk

xevious · 2021-09-02T18:54:54.000Z

For many years, BMW favored red lighting for illumination of car interiors—instrument cluster and various other control indicators for environment, stereo, accessories, etc. And there was a good reason why—they took a cue from the military. At first glance, sitting at night in a car bathed in red, it seems too much. But then, the eyes soon adjust. Red light IS easier on the eyes. And really, the best moonlight tint is red if you want to see without ruining your night vision or disturbing others. One just has to “get over” the premise of favoring white light.

And now, there’s studies showing that there are some inherent health benefits in utilizing red light. Huge topic in of itself.

Sarri · 2021-09-02T19:43:09.000Z

Since people so often mention the military in regards to this topic…

Like another poster, I too was in the military and they actually gave us torches with red filters.
After many complaints about not being able to see really important stuff, like certain lines on maps, they gave us torches with red and green filters… After further complaints, they included blue filters too, but that garnered hatred from medics who couldn’t see blood when treating casualties.

In the end we all just gave up and bought standard Maglite AAs with our own money. They fit the pocket better, anyway.

Forsythe_P_Jones · 2021-09-02T20:52:59.000Z

This is based on old CPF threads where it was discussed at length. The way I heard it, human color vision is high resolution and most sensitive in the blue-green part of the spectrum, and quite insensitive at wavelengths longer than about 640nm. It is the vision from cone cells in the eye. Night vision or scotopic vision, the vision from rod cells, is much more sensitive than color vision, but it is monochrome and low resolution. Its purpose is to see where you are going instead of stumbling into things, not to see fine details.

It is not really possible to read using scotopic vision because of the low resolution. If you want to read you are supposedly best off with blue-green (cyan or so-called NV green) light, around 505nm, set to just barely bright enough.

On the other hand, to best preserve your night vision, you want wavelengths above 640nm, thus the 660-670nm deep red leds that we are finally able to get easily now. But you’d use that for finding your way around, not for reading.

In aviation cockpits were set up so that the person reading the map would have a dim green light and others would have red lights. Night vision gear was also set up to not pick up the blue-green light.

The Rigel Skylite astronomy lights (very dim, with adjustable brightness) have some models where there are both red and green leds to select.

Some species such as cats and owls have a structure in the eye called the tapetum lucidum, which is like a reflector behine the retina that focuses faint incoming light back into their photo receptors. That is what makes their eyes especially shiny. It means their night vision is even more sensitive than that of humans, but also of even lower resolution.

en.wikipedia.org

Tapetum lucidum

The tapetum lucidum (Latin for 'bright tapestry, coverlet'; /təˈpiːtəm ˈluːsɪdəm/ tə-PEE-təm LOO-sih-dəm; pl. tapeta lucida) is a layer of tissue in the eye of many vertebrates and some other animals. Lying immediately behind the retina, it is a retroreflector. It reflects visible light back through the retina, increasing the light available to the photoreceptors (although slightly blurring the image). The tapetum lucidum contributes to the superior night vision of some animals. Many of these Si...