Suprising results of NVG vs red

There has been much discussion of NVG (Night-Vision-Green 495-505nm) vs red light (1 2 3 4 5), some of it contradictory. Since all these discussions failed to un-confuse me, I decided to put it to the test myself. With comments such as "eyes most sensitive to NVG" and "more contrast/detail with NVG" I was ready to agree that NVG would be superior to red for dark-adapted eyes. Imagine my surprise when I found exactly the opposite!

I purchased an NVG Photon Freedom Micro and compared it's lowest setting with a dollar-store red keychain LED (two button alkalines). The wimpy dollar store LED has total fewer lumens so I really expected the NVG to win, but while the NVG light was "brighter" (even on the dimmest setting), I saw less contrast and less detail! I tried a variety of objects around the house including black text on white papter, and the dimmer red won out for sharpness and contrast every time. This was just after waking up in the morning before the sun came up so I should have had complete dark-adaptation.

I think I might understand what's going on here. From what I gather rods are the cells that see NVG in scotopic night vision, and since there are fewer rods in the eye, naturally resolution is lower. And since cones, which are much more numerous, see the red, acuity is higher.

Actually seeing things in the dark is a totally different matter than preserving night vision, and for for me in close distances around the house, red wins. If red has an added advantage over NVG when it comes to preserving night vision, for me that's merely a pleasant fringe benefit.

And as for destruction of night vision, neither NVG nor red noticeably damaged my dark adaptation at these low, low levels. So while my test is admittedly subjective and unscientific, I must concur with the conclusion that some have drawn, which is that what really matters to preserving night vision is using very low levels...of any color.

I agree with the low levels comment.

As someone who has spent 1000's of hours peering into the darkness from the bridge of ships I prefer red, but pretty much anything that is at a sufficiently low level works fine.

The biggest problem for me is that most lights are too freaking bright. Nothing like showing up to relieve the watch and hosing the bridge down with a bright light, killing the entire watches night vision because you hit the wrong switch or button combo.

When it comes to reading a chart though, low white light is the only option. With red, green or blue lights, lines of those colors aren't visible.

Personally I use a Rigel Systems skylite (White/Red), but they all work well because their output is easily adjusted to very low levels.

This is a little out of my regular ballpark, but I believe NVG do have a limited resolution, so if you're trying to read a piece of paper, I bet your own eyes will do a much better job.

As for night vision preservation, I agree that whatever you have at the lowest level that is convenient to use will just simply do the trick. From my own experience I can say that yes, red affects your eyes less, but my experience has also proven that it only means that you'll need more red lumens to see as well as with green lumens, period. 200 red lumens will hurt your eyes just as bad as, just to put a number on it, let's say 45 white lumens if you just woke up in the dark.

It's really a question of what YOU can see... or not. Low low green works best for me, since I can see much better, but then again I know some people who can't even differentiate green from purple, and probably would see better with another color, so I say whatever works for you is good for you. I think too many people forget that, as humans, we are at least a little different in every single aspect, and visual perception is no exception, so trying to find the ONE light that is best for all is like treating humans like machines out of a production line.

[EDIT] .. forgot to mention that the situations where I usually try to preserve my night vision is outdoors in the woods, so green works best to see roots sticking out of the ground...

Amen

two different topics?

I thought green was choosen for the color or the phosphors of night vision devices because the human eye is most capable of perceiving green.

I think that NVG phosphors used in NVDs and ones natural 'night vision' and the preservation of it are two different topics. One does not use a NVD to preserve ones dark adapted vision or 'night vision'.

Low level red light has been traditionally used in the preservation of night vision because we have a difficult time seeing red. The only color we see worse (I believe) is blue. Since we can't see the red very well, out eyes maintain their low level capabilities. I think :thinking:

Just to be clear... I don't have Night Vision Goggles. I have a Night-Vision-Green (A.K.A. Aqua or Turquoise or bluish-green) LED Photon Freedom Micro LED light.

The "NVG" Green lights aren't necessarily designed to "preserve your night vision", ala low level red light...it's more or less designed to help the pilot not have to adjust his eye's when taking off his NVG's...helo pilots turn the lights out when they switch to NV, and turn the NV Green lights on when they're done...so they see things in the same tone...

In short, it has nothing to do with intesnity (or our eye's perception/reception of the intensity of the light), but the tone/tones (color) in which the pilots see things...

Hope this helps!

I think I read somewhere that NVG lighting was designed to not cause night-vision equipment to bloom like it does with bright light sources. I guess the sensors aren't as sensitive to the green colour. The reason the viewfinders are green is that human eyes are the most sensitive to that colour.

Our eyes are the most sensitive to the NVG color, so it is the most useful color to use if you are using ultra low levels that will not disturb your natural night vision no matter the color. I myself have never had a NVG colored light, so I can't speak from experience.

defloyd77 said:

Our eyes are the most sensitive to the NVG color,

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People say that, and while it is true that human rod cells are most sensitive to it, everyone neglects to mention that low levels of NVG light results in vision that is blurry and decidedly lacking in contrast. So let me get the word out... NVG is no good for seeing details.

tylernt said:

People say that, and while it is true that human rod cells are most sensitive to it, everyone neglects to mention that low levels of NVG light results in vision that is blurry and decidedly lacking in contrast. So let me get the word out... NVG is no good for seeing details.

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Hmm, interesting, I've read a lot of people saying they use NVG at low levels and nobody has mentioned the blurriness or lack of contrast.

defloyd77 said:

Hmm, interesting, I've read a lot of people saying they use NVG at low levels and nobody has mentioned the blurriness or lack of contrast.

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Maybe my night vision just sucks in general?

computernut said:

I think I read somewhere that NVG lighting was designed to not cause night-vision equipment to bloom like it does with bright light sources. I guess the sensors aren't as sensitive to the green colour. The reason the viewfinders are green is that human eyes are the most sensitive to that colour.

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This is exactly why.

To convert a cockpit to Night vision goggle compatibility is a major undertaking (the RNZAF had to convert it's fleet of Iroquois a few years ago) and it's all about the colour of the light.

The yellow green sold as night vision green has nothing to do with preserving your night vision, and everything to do with being compatible with image enhancing NVGs

This is from about 15 years ago when I was working on a device to go on a helo.

The NVG devices had notch filters in them for certain wavelengths of light which prevented the NVGs from blooming when you looked at that color light. This allowed you to have a eye readable as well as a NVG readable indicator.

I seem to remember there was a certain green, yellow, blue and red lights that were certified as NVG compatable.

So the NVG green light allows you to look at things like a map with NVGs turned ON or OFF.



wwglen

tylernt said:

Just to be clear... I don't have Night Vision Goggles. I have a Night-Vision-Green (A.K.A. Aqua or Turquoise or bluish-green) LED Photon Freedom Micro LED light.

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Oooops, read your post too fast.

I wonder why bluish-green, I personally can't see a thing with a blue light, I would personally pick a green - yellow light. I read that our eyes respond most to a wavelenght of 555nM for daylight adapted eyes and somewhere around 500 nM for night vision adapted eyesight. But, as I said before, we can't categorize everyone's eye response like we're machines. Some people can't see with any type of lighting at night, while I can do with less than a crescent moon.

Some people still have a hard time to understand this: Any light that is too strong will kill your night vision. Any light that is low enough won't affect your night vision. Red is a popular choice, because it influences your eye less, so will help preserving night vision more easily than green(and red LEDs will run with less power). Green is the easiest color to see, so night vision goggles take advantage of that so they can work with less amplification.

The choice of color to use should also take in account what you're pointing at. Green leaves look black when you point a red light at them (no red in the leaves to reflect the light back), so green seems to work better outdoors. If you're reading, then my guess is it all depends on the number of receptors you have in your eyes for a particular color.

tylernt said:

Maybe my night vision just sucks in general?

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Now that I think about it, I forgot about the night vision blind spot. Since the center of your vision is packed with cones to the exclusion of rods, you have to look off to the side of what you want to see when using night vision. It's called averted vision and pilots and astronomers are trained to use it. And I wasn't using it.

I still prefer red though. Yes, it has to be brighter than NVG -- but of all the colors, red affects rhodopsin (chemical involved in dark adaptation) the least, so it probably ends up a wash when it comes to preserving night vision. The greater resolution of using high-resolution cones (red) vs grainy rods (NVG) still seems worth any tradeoffs to me, at least for close work. For seeing distances, and for improving battery life, NVG may well be better since you need less of it.

Most of the time when I sell a NVG to a soldier it's because the red just isn't bright enough as a functional lowlight navigational tool. The NVG we sell is the second brightest key chain flashlight.
The red far surpasses the run time, I guess what it comes down to is what do you plan to do with it?
I would use the NVG to run in the woods, I would use the red for reading a map.
Just my 2 cents.

Tae Ma Toe said:

I would use the NVG to run in the woods, I would use the red for reading a map.
Just my 2 cents.

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You can't use red to read maps, the contour lines (which on the maps we use at least) are reddish brown and disappear under red light. I know OS maps are the same.