# Green LEDs What is their purpose?



## crizyal (Sep 29, 2009)

I know that red LEDs preserve night vision and blue LEDs can be used for blood tracking, yellow and amber for signaling, but I have no idea what a green LED would be used for. I am interested to know if they are just for novelty or if they have an intended purpose.:shrug:


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## DimeRazorback (Sep 29, 2009)

Aren't they mainly used for map reading?


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## 276 (Sep 29, 2009)

DimeRazorback said:


> Aren't they mainly used for map reading?



That's what i thought, i have used them for almost anything.


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## SFG2Lman (Sep 29, 2009)

battery vampires? ***stares at his cable modem*** oh yeah and indicator lights....a lot of them, usually maps are red light readable so you don't need to reveal your position to the enemy with wavelengths that are more visable at a distance


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## greenLED (Sep 29, 2009)

I've been around for a while, and I have still have no idea what my purpose is. :nana:

lovecpf


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## UpChUcK (Sep 29, 2009)

greenLED said:


> I've been around for a while, and I have still have no idea what my purpose is.



 :thumbsup:


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## LEDobsession (Sep 29, 2009)

Oh good, no one has used this one yet.

They tell us to....
GO!
:nana:

:duck:


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## Sgt. LED (Sep 29, 2009)

greenLED said:


> I've been around for a while, and I have still have no idea what my purpose is.


 
To create our nice CPF discount thread!


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## ElectronGuru (Sep 29, 2009)

crizyal said:


> I know that red LEDs preserve night vision and blue LEDs can be used for blood tracking, yellow and amber for signaling, but I have no idea what a green LED would be used for.



Here's a color sampling of a green nightlight:






Green lights and red lights BOTH preserve night vision. Eyes are extra sensitive to green and extra unsensitive to red, so its easier to see green from a distance while harder to see red (tactical).


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## Beamhead (Sep 29, 2009)

Envy.


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## pOkiE (Sep 29, 2009)

i know they use high powered lights with green filters to see particles in the air. and to preserve night vision...?


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## Burgess (Sep 29, 2009)

to ElectronGuru --


Thank you for that information.

:goodjob:
_


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## zven (Sep 29, 2009)

Well, I also have no idea what their intended purpose is. I only got my Inova X5 in green because it looked cool.

From my use, though, there are a few things that I can say about it. Being that our eyes are pretty sensitive to variations in green wavelengths, shining a green light at something still gives you pretty good differentiation between color regions in the visual field.

Now, while I wouldn't say that you have good color rendition with monochromatic green light, the contrast between colors remains fairly true to what you see under normal white light. That is, under the green LED, you don't see a deep red as red and a happy yellow as yellow, but the red still appears relatively darker than the yellow. It's the same sort of thing as converting a photo to black and white - you don't see colors anymore, but reds and yellows and blues, etc. are still different shades from each other.

Another thing I've thought about, though haven't had the means to test, is the use of green light for aiding night vision. Red is considered good for night vision because only the cones in your eyes see it, and the rods can remain adjusted to the dark, as they aren't sensitive to red. Green, however, is pretty close to the color that all optical receptors are sensitive to (I think it's yellow-green, about like many safety vests, fire trucks, etc., to be precise). So, being that our eyes are more sensitive to green than to either blue or red, I would hypothesize that one could use a dimmer light to achieve the same ability to see. And if you're using a dimmer light, would you not be preserving your night vision to a greater extent?

Also, since both cones AND rods are sensitive to green light, a green LED for night vision would provide you with much better peripheral vision than a red LED, as your peripheral vision uses mostly rods. By the same token, of course (as alluded to above), since red isn't perceived as well in peripheral vision, it would make a better choice in many tactical situations.

Anyway, I personally like and use green LED's for preserving contrast between colors, as opposed to red (where, for example, reds and yellows become indistinguishable) or blue (where reds turn way darker than normal). Of course, I'd be curious to hear more about the intended purpose(s) of green light...


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## Crenshaw (Sep 29, 2009)

To my knowledge, its because our eyes are MOST sensitive to both green and red, so you need the LEAST amount of the light for your eyes to be MOST sensitive to it.

here is a good article

http://www.equipped.org/nitevision.htm

Crenshaw


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## RyanA (Sep 30, 2009)

From my experience, green lights, bright ones at least, knock out night vision. supposedly the eye is most sensitive to green. I think 520-555nm depending on ambient light.


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## Saint_Dogbert (Sep 30, 2009)

Um yeah I thought green light totally ruined night vision, because that is what the ol' rod cells are most sensitive to.


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## Lightraven (Sep 30, 2009)

Green light has at least two applications I can think of by soldiers. I was working with one soldier who was assisting me at night and he brought an Inova X5 in green. I seem to recall handing him a bright white light so he could improve his situational awareness.


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## [email protected] (Sep 30, 2009)

I'm definitely no expert in ALS (Alternative Light Sources) though CPF does have it's share, my understanding was... 

* *Rods* are our night adapted vision receptors (most sensitive to blue/green) primarily located in our peripheral optic regions, don't interpret colour OR movement
* *Cones* are responsible for specific detail & colour (most sensitive to red) primarily in our centered optic region
* *Photosensitive ganglion cells* regulate the dilation of the pupil (amongst other activities) ultimately controlling the amount of light entering the eye

Thus... 

* *Red* promotes night vision, peripheral vision & rapid night adaption in situations devoid of ambient light. 
* *Green* promotes detail, definition & prevents loss to our field-of-vision (night blind spot) but negates "peripheral" vision


Additional subject matter:-
Red - Night vision myth
Night vision - Wikpedia
Photoreceptor cell - Wikipedia
Nightvision in terms of Aviation application
Forensic ALS product guide - Foxfury.com


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## maxspeeds (Sep 30, 2009)

I can confirm that my eyes are very sensitive to the green color spectrum. I bought and tested a green seoul led (out of curiosit) and it would almost give me a headache :sigh: . It was an interesting color, but I cold find no practical use for it in my everyday situations that warranted it to stay in the flashlight. Needless to say it is now collecting dust


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## [email protected] (Sep 30, 2009)

I think NV is less sensitive to green mayby?


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## [email protected] (Sep 30, 2009)

[email protected] said:


> I think NV is less sensitive to green mayby?




Actually the "rods" (in our eyes) responsible for our nightvision is most sensitive to blue/green light


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## robvantour (Sep 30, 2009)

Rods have a great respositivity at 498 nm. (green-blue)
Their responsitivity for red light 600-700 nm is verry low.

To keep your night vision you should use red light.
Using powerfull green light will saturate the rods, and will disable them.

Keeping night vision with green light is only possible with verry low intensities.

For example: instrument backlights on ships are red, or verry dimmed green.

Try this for yourself, let your eyes adapt to nightvision, and turn on a verry bright red light, and after that a bright green one.


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## Ozgeardo (Sep 30, 2009)

Having just returned from two weeks in the field I can confirm that the primary use for green light (in the field tactically and non tactically) is for map reading.

Notably when using red light for either night vision retention or tactically as required when red light is put onto a coloured map many of the coloured features many reds/blues/browns will be reduced in colour and some colours will not appear at all. Green light will enhance the map details whilst still maintaining good night vision (not perfect but better than white light)

But if you are either in a non tactical situation or not trying to preserve night vision then " green means GO! ".

Of note I must admit that too bright a white light can also make map reading quite a task specially if you map is in a plastic map case or laminated.

Cheers
Ozgeardo


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## Pacecar (Sep 30, 2009)

I thought fishermen utilized the green LED headlamps.


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## zven (Sep 30, 2009)

[email protected] said:


> I'm definitely no expert in ALS (Alternative Light Sources) though CPF does have it's share, my understanding was...
> 
> * *Rods* are our night adapted vision receptors (most sensitive to blue/green) primarily located in our peripheral optic regions, don't interpret colour OR movement
> * *Cones* are responsible for specific detail & colour (most sensitive to red) primarily in our centered optic region
> ...



Sounds about right, with a couple of clarifications I would add:

*Rods*

- Adapt relatively quickly to low-light environments

- Have poor ability to see detail

- Are much more sensitive to light than cones (i.e., it takes less light to achieve the same level of activation as a cone receptor)

- Are actually pretty proficient at detecting movement (think about it this way: if they weren't sensitive to movement, how would we ever know that an object was hurtling towards us in our peripheral vision?)

*Cones*

- Adapt slowly to low-light environments

- Provide us with all our visual information on color, and nearly all information on detail

- Three types of cone receptors exist: one most sensitive to blue light, one most sensitive to green light, and one most sensitive to red light (well, I think its sensitivity peaks at yellow wavelengths, but it's for perception of reds - see this chart for a visual)


So yes, green light should work better for peripheral vision, as rods have peak sensitivity pretty close to that (blue-green), and they dominate perception in our peripheral vision. And thus, red would make for a better choice for situations where you don't want to attract/disturb peripheral vision of yourself or others. Also, red would indeed seem to be the best color choice for avoiding the "night blind spot". Green light would also seem to be the better choice for when you need to see during a quick transition to a low-light environment, as it would be more easily picked up by your rods, thus allowing you to see while your cones catch up (a dim red, on the other hand, would take a while to be useful, as the cones wouldn't be adjusted yet, and the rods wouldn't be sensitive to it at all).

However, I would have to disagree about red light promoting detail over green light. True, anything above red will activate the rods, which provide only fuzzy images, but the brain does a pretty good job of picking out details, even from relatively few cone receptors, and making them override that fuzzy image. And with overall sensitivity of the cones peaking at around green (maybe closer to yellow-green), a green light should make for more detailed vision than a red light, as the red light would be activating fewer of the cone receptors. And indeed, in my own tests of this, I can see detail a bit more easily with green light than with red light (though this may also be partially due to the color contrast issue I mentioned in my last post).

Now, the thing I'm left wondering is whether, assuming _equally perceptibly low levels_, a green light or a white light would be more advantageous or more disturbing to night vision. Since white would activate a greater number of receptors, would you not be able to use a dimmer light to achieve equal perception? Or would the individual receptors then not have enough light on their own to provide sufficient information about what you're seeing (e.g., color, shape, detail)?


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## longboat (Sep 30, 2009)

In the early days of LED flashlights, green LEDs were supposed to be the most efficient - i.e., they put out the most light for the amount of energy consumed (obviously, red LEDs were more efficient, but didn't put out much light). This may no longer be true with today's LED technology (don't know for sure), but the popularity of green could be a holdback from those days. I believe blue was also right up there with green in the efficiency/output realm, but did not render colors as well or preserve night-vision as well.


I have an old color beam chart, maybe it's from early photon packaging:

IR - used with night-vision equipment (so you are invisible in the dark)
red - preserves night-vision
orange - outrageous visibility (whatever that means)
yellow - tight beam projection
green - great outdoors (this is lime green)
NV green - incredibly bright and preserves night-vision (this is turqoise)
white - full color illumination
blue - incredibly bright
purple - UV effect (good for spotting scorpions, arachnids)

HTH


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## ElectronGuru (Sep 30, 2009)

robvantour said:


> Keeping night vision with green light is only possible with verry low intensities.





longboat said:


> In the early days of LED flashlights, green LEDs were supposed to be the most efficient - i.e., they put out the most light for the amount of energy consumed



Combining these ideas, since green light is more "effective", less of it is needed. In the case of flashlights, they are more "efficient" because fewer lumens are needed for the same amount of visibility. ie, a 5 lumen green flashlight can outperform a 50 lumen white flashlight for scanning the same dark field.


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## SFG2Lman (Sep 30, 2009)

about the fishermen thing, i thought that specific green wavelength penetrated water pretty well too


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## yellow (Sep 30, 2009)

I _think_ I remember somehow, that EARLY night vision equpiment (Gen I) could not detect green (but anything else).

So the soldier could use active light and not be detected (like he would when using IR, white, anything else)

PS: Gen I was pretty useless in the complete dark without active lights


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## Sgt. LED (Sep 30, 2009)

Yeah and friggin' blinded you when you got flashed.


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## John_Galt (Sep 30, 2009)

A friend of mine found a green Inova X5 in his tent. It was great for walking around summer camp at night. Very bright, and, because most things there were green, everything looked normal. It blew away the red 3 LED nite-ize drop in in my [email protected] 

But mine was better for capture the flag at 10:00. Harder to see across the field, unless it was pointed straight at you.


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## greenlight (Sep 30, 2009)

I love green lights. My favorite is my green inova X1.v1. For a moderately powered LED light it makes a very dramatic beam. 

It gets other people's attention, plus the color is pleasing to the eye. 

With a distinctive color like that, people always know that it is YOU who is approaching.


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## darknessemitter (Sep 30, 2009)

Could one of the long time members maybe point this thread to one of the better explainations of uses for different wavelengths? Red vs. Green for nightvision has been discussed many times, and a lot of inaccurate information gets posted each time.... kinda gives me a headache 

I'll try to make this short. 

RED: Helps preserve natural scotoscopic nightvision. Rod cells are insensitive to it. You'll retain more of your scotoscopic nightvision after using a red light.

GREEN: Rod cells are VERY sensitive to it, therefore it will DEPLETE the rhodopsin needed for scotoscopic night vision FASTER. However, the cone cells, used for bright light color vision can see a lot of detail in green, so some people find it useful for that reason, although you won't be able to see as well in the dark when you turn the light OFF.

GREEN For Use Around Night Vision Goggles: Some types of night vision goggles are less sensitive to green light, using green light may cause less glare for a friend standing next to you who is using nightvision goggles. However, it is NOT completely invisible to nightvision gear, so don't assume that an enemy with nightvision goggles will not see you waving a bright green light around.


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## crizyal (Oct 1, 2009)

Thanks for all of the responses. I think I would like to play around with them a bit. I would like an Inova X5 green though it looks as though they have been discontinued.


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## [email protected] (Oct 1, 2009)

darknessemitter said:


> GREEN: Rod cells are VERY sensitive to it, therefore it will DEPLETE the rhodhipsin needed for scotoscopic night vision FASTER.



Rhodopsin is sensitive to light period, depleting as a direct result to exposure (red light causes depletion also albeit at a slower rate) 


Might be better to condense further...

*Red* - promotes "singular" detail (due to cones), prevents night blindspot (associated with rod only night adaption) & depletes rhodosporin (biological chemical necessary for "rod" low light adaption) albeit slowly
*Green* - promotes peripheral night vision (but depletes rhodosporin more readily) also enhances detail & colour perception


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## Hooked on Fenix (Oct 1, 2009)

Green light is invisible to many animals. I tend to use my green Inova X5 when walking down streets with lots of dogs around. As soon as one dog sees you, they start barking until all the dogs on the block are aware of your presence. Often, there is someone who left their gate open and the dogs will get loose and chase you. My green light keeps them from seeing me as easily so I can walk down the road safely. This is especially needed on the 4th of July when I walk to see the fireworks instead of driving and getting caught in traffic afterwards.


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## Sub_Umbra (Oct 2, 2009)

I greatly prefer green and blue/green for preserving dark adapted vision. For the record *ANY COLOR* may be used while preserving dark adapted vision as long as it is not pointed into the eyes or allowed to reflect back into them. By the same token any colored light can also *destroy* dark adapted vision if it is too bright and/or is handled carelessly. 

Even red lights with wavelengths longer than 640nm can wreck your dark adapted vision if they are bright enough to burn an afterimage into your cones that overpowers the weak output of your rods. Even though your rods won't be directly affected -- they'll be out of commission for a while. Try it.

Don't forget Christmas and Mardi Gras for green LEDs.


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## Search (Oct 2, 2009)

There is proof that different colors affect the human eye in different ways.. however.

This was discussed many months ago and around 30 people all had the same but different things to say.

Basically, there wasn't a single color that universally worked best. Some people just plain saw better with red and some better with green.

It's safer to say to try them both and see what works best with you.

I've got this for night time tactical house recon anti-wife waking missions:






It's a battery vampire.


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## defloyd77 (Oct 2, 2009)

I have a thread going on a 1AA/1AAA battery vampire light with a red or green LED. I'm just curious as to what light you guys use that use green LED's, I'm looking into getting a green Inova X1. 

Also regarding green LED's and efficiency, the green Rebel gets 100 lumens @ 350 mA, so they're still of the highest efficiency among colored LED's. If one were to make a call or email Peak, they can custom make an Eiger with one of these Rebels.


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## darknessemitter (Oct 2, 2009)

[email protected] said:


> Rhodopsin is sensitive to light period, depleting as a direct result to exposure (red light causes depletion also albeit at a slower rate)
> 
> Might be better to condense further...
> 
> ...


 
Heh, sorry about the creative spelling of rhodopsin. 

That's a good point that rod cells aren't completely unaffected by red light, but they are much less sensitive to it; use a reasonably dim, longer wavelength red led and at least it won't affect you as much or as quickly. 

Also, on green light: Pretty much any color other than red will help with peripheral vision, although green a pretty good monochromatic option if dim enough. Otherwise, a very dim white light can serve the same purpose. Maybe a Photon Freedom on minimum setting, or another 5mm light on near dead batteries.


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## Sub_Umbra (Oct 2, 2009)

Green light will also do a better job of lighting things that are already green which accounts for at least a part of their popularity with hunters and others who spend time in the woods.


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## angelofwar (Oct 2, 2009)

Since the military bascially dropped for flashlight application (except the Yellow-Green), there only real purpose is signalling. What green is good at (as far as they're concerned), red and blue does better...


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## Hooked on Fenix (Oct 3, 2009)

Green light is also great for traveling in the snow. White light reflects back and blinds you, green doesn't.


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## TKC (Oct 3, 2009)

*I personally see better with green LED's, then red.*


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## darknessemitter (Oct 3, 2009)

angelofwar said:


> Since the military bascially dropped for flashlight application (except the Yellow-Green), there only real purpose is signalling. What green is good at (as far as they're concerned), red and blue does better...


 
Oh, interesting, so is yellow-green considered ideal for use with nightvision goggles (for minimal glare)? Prefered over green or blue-green?


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## EngrPaul (Oct 3, 2009)

RGB display boards and traffic signals.

...and sometimes just for fun.


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## angelofwar (Oct 3, 2009)

darknessemitter said:


> Oh, interesting, so is yellow-green considered ideal for use with nightvision goggles (for minimal glare)? Prefered over green or blue-green?


 
Yellow-Green is preffered, as it paint's everything the same color as the NVG's...so you go from YG objects, to Yellow-Green...your eye's don'thave to adjust as much whenremoving your NVG's...but Blue/Blue-green is good, cause it won't interfere with NVG's...you can only see it from the source...other than that, it's invisible...


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## [email protected] (Oct 4, 2009)

darknessemitter said:


> Heh, sorry about the creative spelling of rhodopsin.
> 
> That's a good point that rod cells aren't completely unaffected by red light, but they are much less sensitive to it; use a reasonably dim, longer wavelength red led and at least it won't affect you as much or as quickly.
> 
> Also, on green light: Pretty much any color other than red will help with peripheral vision, although green a pretty good monochromatic option if dim enough. Otherwise, a very dim white light can serve the same purpose. Maybe a Photon Freedom on minimum setting, or another 5mm light on near dead batteries.



Agreed! :thumbsup:


From what I've seen around the aviation scene NVIS white is the "new" low powered colour light of choice


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## drmaxx (Oct 4, 2009)

The following read might be interesting - even after 48 posts most is already said:
http://www.astromax.org/activities/members/kniffen.htm


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## Sub_Umbra (Oct 4, 2009)

TKC said:


> *I personally see better with green LED's, then red.*


+1

Way, *way* better.


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## crizyal (Oct 4, 2009)

OK, so the next question is what would be a good variable green LED light, say in a ramping mode or at least a really low low?


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## NE450No2 (Oct 4, 2009)

If I am remembering correctly the Yellow Green LED's on the A2 Aviator were specifically designed for Map reading, by pilots.

They have a "little book", quite thick with the different Airports, and their transponder and other info.

At least that is what I was told by SF when I toured the "factory" and that was one of the lights I was given by SF.

I always carry it in my vehicle when I travel for that reason.

I liked the A2 so well I bought a second for All round use with the white LED.


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## SilentK (Oct 4, 2009)

I always thought that green leds were used so you would not wash out Night vision devices as easy. :thinking: Like people without NVG could use them around people with NVG


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## Sub_Umbra (Oct 4, 2009)

crizyal said:


> OK, so the next question is what would be a good variable green LED light, say in a ramping mode or at least a really low low?


If you want to use a green light while preserving dark adapted vision the most difficult thing will be finding one *with a low enough output level.* I've worked with them extensively for years and I think that many new users are frustrated by how much brighter they are for low light tasks than the exact same models of lights in different colors. This makes *pointing discipline* all the more critical. If one takes any run of the mill green light for a low light task and splashes it around like a sugared up kid at a pajama party he will likely come away from the experience thinking that green is a poor choice for low light work.

The best variable output lights in green for preserving dark adapted vision are probably the *Rigels* and the *Photon Freedom.* They will adjust to lower output levels than any other green lights that I am aware of. In any color these are also the best lights I know of for experimenting with dark adapted vision.

The PF also has the advantage of halving it's output and *GREATLY* increasing it's runtime over the stock light by swapping out the two cr2016s with one cr2032 cell. The color shifts a bit with the voltage drop but that shouldn't affect many tasks. I haven't done a runtime test on the green PF with one cr2032 but one of my cyan PFs was still going strong after twelve days straight. 

The green Rigels and PFs will allow one to see *much more* detail than with the reds and oranges -- and at much lower output levels, to boot. The same is true for the Rigels and PFs in cyan. In general, the "Greens" will also greatly reduce the intensity of your light's *IR signature* for those who may demand that feature. 

The now long gone CMG Infinities in green were too bright until the cell was about shot but they could be cupped when brighter, which was annoying but workable.


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## darknessemitter (Oct 4, 2009)

angelofwar said:


> Yellow-Green is preffered, as it paint's everything the same color as the NVG's...so you go from YG objects, to Yellow-Green...your eye's don'thave to adjust as much whenremoving your NVG's...but Blue/Blue-green is good, cause it won't interfere with NVG's...you can only see it from the source...other than that, it's invisible...


 
Oh, that makes sense. But, which is less detectable/glaring through the nightvision gear? Yellow-green or blue-green? 

I suppose the other benefit of yellow-green might be that since it's a slightly longer wavelength, it won't affect rod cells as quickly as blue-green, assuming you keep it dim. Though I guess that might not make as much of a difference if you've just had the viewfinder of the NVG up to your eyes...


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## Sub_Umbra (Oct 4, 2009)

darknessemitter said:


> ...But, which is less detectable/glaring through the nightvision gear? Yellow-green or blue-green?...



*Blue/green* (cyan). A few years ago astronomer, flashlight inventor and CPFer *RigelSys* posted that he sent samples of the *cyan* LEDs from the Rigel MIL Starlite and MIL Starlight Mini to the Air Force research lab at White Sands for testing and they certified them as 'NV Gear compatible.' He stated that at that time they were the *only* LEDs so certified.

Unfortunately it would seem that Google may no longer be indexing that old CPF archive.

In the aftermath of Katrina I was jawing with an 82nd Airborne night patrol in front of my house. I told them that I had a light in my pocket that I didn't think that their NV gear could see. They were very skeptical until I turned it on and they couldn't see it unless it was pointed *directly at them.* They were suitably impressed as they had the latest gear available. The light in question was an old CMG Infinity with a blue/green LED. (The LED color is similar to the beam depicted in my avatar.)

The *Phantom Warrior* company makes a line of lights *with all of the IR filtered out of the beam.* Even in white they are only visible with an NV device if they are pointed _right into it._ They are not available to the public.


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## darknessemitter (Oct 4, 2009)

Sub_Umbra said:


> *Blue/green* (cyan). A few years ago astronomer, flashlight inventor and CPFer *RigelSys* posted that he sent samples of the *cyan* LEDs from the Rigel MIL Starlite and MIL Starlight Mini to the Air Force research lab at White Sands for testing and they certified them as 'NV Gear compatible.' He stated that at that time they were the *only* LEDs so certified.
> 
> Unfortunately it would seem that Google may no longer be indexing that old CPF archive.
> 
> In the aftermath of Katrina I was jawing with an 82nd Airborne night patrol in front of my house. I told them that I had a light in my pocket that I didn't think that their NV gear could see. They were very skeptical until I turned it on and they couldn't see it unless it was pointed *directly at them.* They were suitably impressed as they had the latest gear available. The light in question was an old CMG Infinity with a blue/green LED. (The LED color is similar to the beam depicted in my avatar.)


 
I know blue-green has been used for NVG compatibility, but I was wondering how yellow-green compares, since it sounds like the military may be switching to it. 



> The *Phantom Warrior* company makes a line of lights *with all of the IR filtered out of the beam.* Even in white they are only visible with an NV device if they are pointed _right into it._ They are not available to the public.


 
That sounds interesting, but, I thought modern NVG was still fairly sensitive to visible red? Is this one of the ones that's sort of bluish-green tinted "white"? Like it cuts most of the visible red too.


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## defloyd77 (Oct 4, 2009)

Sub_Umbra said:


> The light in question was an old CMG Infinity with a blue/green LED. (The LED color is similar to the beam depicted in my avatar.)



The light in your avatar looks pure green to me, is it my computer? Also is that an actual flashlight or what? It looks awesome.


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## darknessemitter (Oct 4, 2009)

drmaxx said:


> The following read might be interesting - even after 48 posts most is already said:
> http://www.astromax.org/activities/members/kniffen.htm


 
No offense, but that article seems pretty one-sided. There are some good points about the limitations of red and advantages of very dim green, but it mostly ignores the benefits of red light, and exaggerates the cons.


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## Sub_Umbra (Oct 4, 2009)

defloyd77 said:


> The light in your avatar looks pure green to me, is it my computer? Also is that an actual flashlight or what? It looks awesome.


There's quite a bit of blue in there. It may look somewhat different on your computer (Alpha settings and all that). Color is also *perceived* differently from person to person. Much of what we are conditioned to think of as green actually has a lot of blue in it -- like the "green" traffic light. It has lots of blue *and* green in it to make things easier on people who are color blind to green. The color 'Tokyo Blue' is actually the name of the color for the green used in traffic lights in Tokyo.

It's not a light. It's just an icon I made years and years ago when I was using green lights for all non color rendering tasks. It started out pretty close to 525nm which is a pretty common color for green LEDs. The way it is now it's pushed up into the low end of cyan, maybe 585-590nm -- i dunno. I've got a fistful of lights that produce that very color at one voltage or another. I've used it for everything that doesn't require color rendering for years and I would be lost without it.


darknessemitter said:


> ...That sounds interesting, but, I thought modern NVG was still fairly sensitive to visible red? Is this one of the ones that's sort of bluish-green tinted "white"? Like it cuts most of the visible red too.


I don't have one but the pics on their site make their white look pretty white to me -- but I'll admit that variation in white tints don't have nearly as much impact on me as they do to others. For me white is all about color rendering...


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## defloyd77 (Oct 5, 2009)

Thanks for all of that very interesting info Sub Umbra. You know, the more I look at it, I do see blue, especially in the circle.


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## NE450No2 (Oct 5, 2009)

Let me add, that the yellow green LED's of the A2 are just not bright enough IMHO for "general walking around use".

They are great for reading a map, but not for other GP tasks, which is why I got a White LED A2.

It is PERFECT, in EVERY WAY.


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## defloyd77 (Oct 12, 2009)

Sub_Umbra said:


> The best variable output lights in green for preserving dark adapted vision are probably the *Rigels* and the *Photon Freedom.* They will adjust to lower output levels than any other green lights that I am aware of. In any color these are also the best lights I know of for experimenting with dark adapted vision.
> 
> The PF also has the advantage of halving it's output and *GREATLY* increasing it's runtime over the stock light by swapping out the two cr2016s with one cr2032 cell. The color shifts a bit with the voltage drop but that shouldn't affect many tasks. I haven't done a runtime test on the green PF with one cr2032 but one of my cyan PFs was still going strong after twelve days straight.
> 
> The green Rigels and PFs will allow one to see *much more* detail than with the reds and oranges -- and at much lower output levels, to boot. The same is true for the Rigels and PFs in cyan. In general, the "Greens" will also greatly reduce the intensity of your light's *IR signature* for those who may demand that feature.



Rigel describes the green LED as Blue-Green, is this the typical green with a hint of blue (like Sub Umbra's pic) or is it closer to cyan?


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## Sub_Umbra (Oct 13, 2009)

defloyd77 said:


> Rigel describes the green LED as Blue-Green, is this the typical green with a hint of blue (like Sub Umbra's pic) or is it closer to cyan?


I've never used the green Rigel -- I have the Mil Starlight Mini which is cyan. Since it is adjustable over a *very wide* output range and uses no PWM it's actual color varies quite a bit from one extreme to the other.

For this reason I would also expect a broad range of color from the green Rigels as the voltage changes.

My claims about being able to see better with the greens than with the red/oranges comes from experience with *other brands* of green and red, red/orange lights.


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## defloyd77 (Oct 13, 2009)

Sub_Umbra said:


> I've never used the green Rigel -- I have the Mil Starlight Mini which is cyan.



Well that does answer my question as they describe the Mil version as blue-green as well. Too bad for me, cyan irritates the heck out of me as does blue. I have a few electronic devices that have cyan indicator lights or backlights, they aren't that bright, but they totally kill my head and eyes. Makes me wonder if I'll have problems with traffic light green.

"LEDs are socketed so you can easily swap in different color LEDs." Does this basically mean you can change the LED in a similar way as a bi-pin bulb like a MiniMag, just pull it out and plug a different one in?


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## Sub_Umbra (Oct 13, 2009)

defloyd77 said:


> ..."LEDs are socketed so you can easily swap in different color LEDs." Does this basically mean you can change the LED in a similar way as a bi-pin bulb like a MiniMag, just pull it out and plug a different one in?


Yes, changing LEDs is a snap in the Rigels. Also note that many of them are set up to light up in the desired color if you turn the thumb wheel one way -- or light up in white if you turn it the other way. As I mentioned in an earlier post, they are great lights for experimentation. The interchangeability of LEDs is one reason.

The guy who owns Rigel, Leon (cpf username RigelSys) has been very helpful to experimenters at cpf in years past. He has mentioned that one could email him prior to a light order and arrange to buy additional colors of the LEDs his lights use.


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## Kuryakin (Oct 13, 2009)

Yep, the human eye is most sensitive at 555nm. Alas, this is nearly impossible to make with the present LEDs. So, 525nm is about as close as you can get, which is something like 97% as sensitive. 
The irony is, this is where LEDs tend to have the LOWEST radiometric efficency! 



RyanA said:


> From my experience, green lights, bright ones at least, knock out night vision. supposedly the eye is most sensitive to green. I think 520-555nm depending on ambient light.


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## Sub_Umbra (Oct 13, 2009)

> ...From my experience, green lights, bright ones at least, knock out night vision. supposedly the eye is most sensitive to green. I think 520-555nm depending on ambient light...


Even *Megalumen* beams may be used in some situations while preserving dark adapted vision if you know how. This type of application is *routine* in some occupations. 

 Don't point it in your eyes
 Don't let it bounce into your eyes
Color is far less a factor in destroying dark adapted vision than poor *pointing discipline* is.


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## defloyd77 (Oct 13, 2009)

Sub_Umbra said:


> Yes, changing LEDs is a snap in the Rigels. Also note that many of them are set up to light up in the desired color if you turn the thumb wheel one way -- or light up in white if you turn it the other way. As I mentioned in an earlier post, they are great lights for experimentation. The interchangeability of LEDs is one reason.
> 
> The guy who owns Rigel, Leon (cpf username RigelSys) has been very helpful to experimenters at cpf in years past. He has mentioned that one could email him prior to a light order and arrange to buy additional colors of the LEDs his lights use.



That's great! I think I just might get one with (non blue) green and red. I wish they made a slightly more rugged version of the mini, maybe I can find some sort of rubber casing or something.

By the way, now that I notice the bluishness to incan green traffic lights, it annoys the heck out of me but they aren't all like that. The LED left turn ones are pure green, I wonder if this varies by location or what?


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## Sub_Umbra (Oct 13, 2009)

defloyd77 said:


> ...I wish they made a slightly more rugged version of the mini, maybe I can find some sort of rubber casing or something...


My understanding is that the standard Rigels are somewhat more rugged than the Minis but I don't have one. I get the impression that in the Mini, the 'Astronomer' in Leon really shows. It seems to be essentially designed as an indoor light. It's smaller and handier than the big one and is all set up with a no nonsense lanyard. It is near perfect for my indoor uses.

It depends on your needs. I've read reviews by people I respect who really didn't like some aspects of the Mini, like a little light leakage, lack of water tightness and a snap together construction. 

If you get either model you should post your impressions on it.


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## defloyd77 (Oct 13, 2009)

Sub_Umbra said:


> It depends on your needs. I've read reviews by people I respect who really didn't like some aspects of the Mini, like a little light leakage, lack of water tightness and a snap together construction.



I definitely like the Mini better, it would be a mostly indoor light and I don't think the standard allows for the change of the LED's as easily as the mini and that's my favorite feature.


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