Is using red light for "preserving night vision" simply a myth?

[ebow86]

A red light to perserve night vision isn't much good to me becuase I'm bound to blast off the high beam anyway, thus destroying my night vision, but I can see where alot of people find it useful.

 

[JNewell]

Interesting post and discussion. Some of the conclusions surprise me. I'm not going to throw Wikipedia at the discussion, though.

Red light is preferable over white (or other colors), but the explanation given is wrong. I give references; you can google them, but I don't know if you can get the original articles. I can, being on a university network. Libraries should be able to get them, though.

The standard explanation already given is wrong, since both cones and rods react the same above wavelengths of 650 nm or so (red), but rods are much more sensitive at lower wavelengths, thus their night vision gets killed [S. Hecht and Y. Hsia, J. opt. Soc. Am. 35 (1945)]. Thus, for the same 'brightness experience' (for lack of a better understandable term) of red and white light, the eyes will recover more quickly if red light is used [E. O. Hulburt, 'Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors', J. opt. Soc. Am. 41 (1951)]. It's not that red will protect night vision, but destroys it much less than white.

However, red light loses its advantage with lower brightness (and I'm talking really low brightness here). If you don't need much brightness, you can get away with low intensity white [S.M. Luria and David A. Kobus, 'The Relative Effectiveness of Red and White Light for Subsequent Dark-Adaptation', Naval Submarine Medical Research Laboratory, Report 1036 (1984)]. White has the advantage of giving you sensitivity of a full color spectrum over any monochromatic source. It essentially makes no sense to restrict your eyes to the sensitivity of just one color, since you will need much higher brightness with the one color to get the same 'brightness experience' as with white.

As always, YMMV. The above articles assume 'normal' 'average' vision. If you're color-blind, for instance, your cones and rods react differently anyway, and it may not work for you.

 

[M@elstrom]

Concentrating to the question of red Vs. green for night adapted vision, this has been hashed out quite a bit on these forums and I'll "reuse" the answer I gave then...

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

And...

Obviously green light effects the Rod cells and to a lesser extent the Cone cells due to their 3-way cell distribution (which varies from one individual to the next) of the three types of Photopsin utilized by the Cone cells the largest proportion are sensitive to Long light Wavelengths of 500~700nm (predominantly Red).

Considering our Cone cells are responsible for detail & acuity it seems only logical that this is the reason for the NVG's applied color frequency and use of green ALS's in field for map reading and up close detail work

*Current school of thought seems to support the application of "significantly" low level white light for non-military and hunting/tracking applications allowing the engagement of both the Cones and to a lesser extent the Rod cells of the eye for night orientation/navigation as a means of avoiding the associated "night blind spot" resulting from peripheral only night adapted vision

Experiments conducted by G. Wald determined that the Rod cells were insensitive [should read less sensitive] to wavelengths above 640nm (Red), thus red light's only negative impact on our night adapted vision is it's intensity, low level red simply works! :thumbsup:

Normalised absorption spectra of human Long, Medium & Short wavelength Cones & Rods cells


FWIW Cones division (which varies person-to-person) are explained rather well by Wikipedia HERE

 

[wyager]

What a truly sad and skewed perspective... if science is always 100% correct why do we have members of the scientific community arguing about global warming? scientific ideology is nothing more than the current "collective agreement" reached through repeatable experiments OR interpretation of data collected using the scientific approach/method...

Remember they once thought the world was flat, the earth was at the centre of the galaxy & the atom was the smallest structure in the universe, trust your personal instincts/experience and only use "current science" as a guide :candle:

Science IS always correct, barring human error. That's what I said. The thing about global warming is this-the fact that the earth is warming is undeniable, but whether or not it is a natural cycle is arguable. We don't have sufficient data to satisfy the scientific method about global warming yet. And then of course, there are people who argue things like "evolution is not real". But of course, this is just human error. Spitting in the face of scientific evidence does not count as science, and should be ignored.

They thought the earth was flat because they were raised to ignore facts and not follow the scientific method. No respectable scientist said that the earth was flat, but only because there were no legitimate scientists studying the earth in places they thought it was flat (some societies were aware it was round). Any people that actually followed the scientific method were burned at stake, so you got a lot of human error.


Our science now is amazing-and we have almost removed human error from science, as we now have machines that will perform complex mathematics and logistics without fail. I trust our science a lot more than the "science" of the past. I certainly trust it more than my own personal experience, beyond the fact that I have to experience the science.

 

[M@elstrom]

[Off Topic]

 

[wyager]

"Okay so again I ask you... was science correct when they unequivocally stated that "the atom" was the smallest object in the universe?"

Occam's razor. No more should be presumed to exist than absolutely necessary. The existence of sub-atomic particles was not important to science at the time. That's like asking why the Aztecs were smart if they didn't know about electromagnetism.

"Take the "scientific method" and apply it in your personal life don't trust someone else to do your thinking for you, make up your own mind that's why you've got a brain"

I've never let anyone decide for me any more than is necessary. However, sometimes you just have to trust others. A. priori knowledge is still useful. I've never used an electron microscope, but I still trust the people that have when they say computer chips are made out of silicon.

 

[OceanView]

Although debating the scientific method and the evolution of human understanding of the natural world may make an interesting college course, we're terribly off-topic here. :thumbsdow

Why do night vision threads often bring out the worst in flashaholics? :shrug:

 

[M@elstrom]

Although debating the scientific method and the evolution of human understanding of the natural world may make an interesting college course, we're terribly off-topic here. :thumbsdow

Agreed I will delete off topic commentary :naughty:

 

[elgarak]

Experiments conducted by G. Wald determined that the Rod cells were insensitive to wavelengths above 640nm (Red), ...

No, he didn't.

See my previous post, second graph. Read the caption. That's Wald's data. Which DOES show sensitivity still at 700 nm... (Never trust Wiki. Check the original source.)

 

[Nitro]

I do a lot of star gazing. I, like most astronomers know when I've achived good night vision. But even more important I know how long it takes for it to return after seeing light. If I go inside with a white light, even if dim, it does take longer to get my night vision back than if it's red.

I purposely have a red bulb in my garage, which is pretty bright, that I use when star gazing. My night vision is preserved after being around the red light. The only time I have a problem is if I stare directly at the bulb. But if it were a white bulb and I stared directly at it, my night of star gazing would be over.

Something else that's interesting that most astronomers know is there is no color when star gazing. Your eyes can't detect color in very low light. Also you see less detail. However, a trick you can do is look just to the side of the object. After a while your mind will gather the image in more detail than if you were looking directly at it.

As far as science goes: Science, statistics, politics, religion, law have all been used by persons to push an agenda. As the old sayings, "Figures don't lie, but liars figure", and "Don't believe your own eyes." come to mind.

 

[kramer5150]

I find that any color tint if low enough will preserve my night adapted vision. Warmer tints, amber, orange and red I find "easier" on my adapted vision. By that I mean less "blinding" upon initial exposure, and shorter time to recover once exposed.

My opinion is based on my own observations with my 3 lights. I have three different moderate-low output lights. A Lenser, nite-ize minimag and a SF-A2. All 3 use 3x 5mm emitters, and drive them fairly hard to maximum output levels. The surefire and Lenser use Nichias. I know for a fact that the SF-A2 slightly overdrives its red LEDs. Of the 3 the red A2 is by far MUCH more easy on my night adapted vision. It takes me less time to adjust and recover with the red tinted SF.

 

[mzil]

As one can see, both curves pretty much overlap above 600 nm. So, red light for night vision is just a myth. Or is it? After all, anecdotal evidence (as provided in this thread) seems to show that red IS better for night vision. Let's test it scientifically.

Yes, and thanks for these charts (which none of us have access to) and would you kindly do me (us) a favor and clear some things up since you can read the actual articles (I can only find brief summaries):

A) "Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors"

Liars! You only tested red vs white (going by the charts). Blue green etc never got tested.

B) "Thus red is better than white at preserving, or at least reducing the time to restoring, night vision once exposed."[paraphrased]


How exactly was this tested? After the antagonistic light exposure were the subjects then pressing a button at the lowest level that they could reliably detect a light bulb had been turned on staring right at it? Asked to read text and getting an accuracy score of 75% or better, or what? The submarine tests seemed to be judging the ability to see silhouettes against a starry sky, or something similar, but the other test I need more details, please.

C) "After testing the subjects ability to (lets say) read the text with a 75% accuracy level after exposure to the four test voltages using the white light bulb, we then repeated the test exactly but instead substituted the red light bulb." [paraphrased]

Hello! McFly! Red light bulbs are white ones that have been painted red so they obviously will have a reduced output and yield better results simply because they are dimmer and that you haven't accounted for! [People in this thread who claim red is superior haven't indicated they made any attempts to account for this either, I might add.]
---

Slightly off topic, but I'll bring it up anyways:

There are two kinds of people interested in red light. An astronomer wants to be able to read sky maps and find things in a bag while preserving night vision as best possible, and number two, a sniper who also wants to preserve night vision but even more so doesn't want to give away his (her) position. But isn't red light, the internationally accepted color of attention getting (think a bike light) about the stupidest color to use for a sniper? Hey look at me, over here!:wave:

 

[mzil]

Something else that's interesting that most astronomers know is there is no color when star gazing. Your eyes can't detect color in very low light. Also you see less detail. However, a trick you can do is look just to the side of the object. After a while your mind will gather the image in more detail than if you were looking directly at it.

I can see the Andromeda Galaxy with the naked eye, using this "averted vision" technique, which is 2.5 million light years away, if I recall correctly. As far as I know that is the farthest distance a human can see! [We are also on a collision course with it, so that's cool too!]

Some stars do have discernible color, BTW:
http://outreach.atnf.csiro.au/education/senior/astrophysics/photometry_colour.html

 

[elgarak]

Yes, and thanks for these charts (which none of us have access to) and would you kindly do me (us) a favor and clear some things up since you can read the actual articles (I can only find brief summaries):

A) "Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors"

Liars! You only tested red vs white (going by the charts). Blue green etc never got tested.

B) "Thus red is better than white at preserving, or at least reducing the time to restoring, night vision once exposed."


How exactly was this tested? After the antagonistic light exposure were the subjects then pressing a button at the lowest level that they could reliably detect a light bulb had been turned on staring right at it? Asked to read text and getting an accuracy score of 75% or better? The submarine tests seemed to be judging the ability to see silhouettes against a starry sky, or something similar, but the other test I need more details, please.

C) "After testing the subjects ability to (lets say) read the text with a 75% accuracy level after exposure to the four test voltages (*** shown on the logarithmic scale axis X, using the white light bulb, we then repeated the test exactly but instead substituted the red light bulb.

Hello! McFly! Red light bulbs are white ones that have been painted red so they obviously will have a reduced output and yeild better results simply because they are dimmer and that you haven't accounted for! [People in this thread who claim red is superior haven't indicated they made any attempts to account for this either, I might add.]
---

Slightly off topic, but I'll bring it up anyways:

There are two kinds of people interested in red light. An astronomer wants to be able to read sky maps and find things in a bag while preserving night vision as best possible, and number two, a sniper who also wants to preserve night vision but even more so doesn't want to give away his (her) position. Isn't red light, the internationally accepted color of attention getting (think a bike light) about the stupidest color to use? Hey look at me, over here!:wave:

This is from the Hulburt ("Time of Dark Adaptation after Stimulation by Various Brightnesses and Colors") paper:

1) They did indeed use three different monochromatic light sources. Remember, this was 1951, so the choices were limited. The monochromatic lamps were gas-discharge lamps, which produce a handful of discrete lines; for instance, a sodium vapor discharge lamp gives off one visible yellow line at 589 nm (actually, two lines at 589.0 and 589.6 nm. Standard test lamp to test a spectroscope during my lab classes. If you could see both lines with a simple grid spectroscope as they use in chemistry, you were good). Unwanted lines were filtered. Additionally, they used a Tungsten-incandescent with filters, which were not as well monochromatic, but pretty narrow band. The red was done with the filters used in Navy night vision protecting goggles (this was done at the Naval Research Lab in Washington, D.C.). Yes, the brightness of those lamps were calibrated. They used a (70% reflectivity) so called stimulation screen that was illuminated by those lamps, and they could adjust the brightness of this screen by adjusting the distance. A light meter was used to calibrate the brightness.

2) The night vision was tested with a target screen with a dot on it that was illuminated with a tungsten lamp turned so low that the screen itself was just at the threshold of being visible dark adapted. When the eyes became closer to dark adapted, one would see first the screen, then the dark dot on it. I had to do similar experiments myself while studying for my (German) Physics diploma, and this is quite doable and fascinating to see. The target lamp was shielded so that the light would only hit the screen, not the test person. The sizes of the screen, dot and distance to the test person were chosen so that the screen would appear under a viewing angle of 24 degrees, the dot under an angle of 1 degree.

3) The procedure was as follows. Test person would dark adapt the eyes. Then turn on the stimulating screen and look at it for a defined period of time. Then turn off the stimulating light, and wait (with a stopwatch) until one sees the target screen, and then the dot. Stop the time. The target screen was on all the time, since it was so low brightness that it didn't matter. Repeat often and take the average time. Get as many people (students at a university )as possible and do it with them.

All clear? Very hands on. Those guys were hard-*** physicists. But it's pretty much the newest data I could find. Essentially, no one thinks it's worth repeating (except for torturing Physics students). Hecht, Wald, Hulburt nailed it (Hecht did build a mechanical shuttered device to turn on and off targets (essentially model stars) and stimulating light in the 1920s, and then spent about 25 years using that thing to experiment with it). All the newer papers is 'just' detail stuff, how each functional building block in the eye does work to produce these effects.

Oh, and about 'no color during stargazing': Sure, the rods do not detect colors. But stars ARE differently colored, and with a large enough telescope you can see those colors with your own eyes. Essentially, the objective opening diameter needs to be large enough to collect enough light. My old school had a telescope large enough -- forgot how large exactly, and unfortunately not often enough available (plus, usually lousy weather in Germany, and a lot of stray light). But once I saw Betelgeuse, and got perfect seeing. Amazing! The air between my eye and Betelgeuse would become perfectly still for just a moment, and the fuzzy blinky blob I saw did shrink to this perfect pinpoint with an amazing red-orange hue. Just beautiful.

About red being a stupid choice: Nature's a *****. Red is the only color that does have any good effect.

 

[M@elstrom]

Low red light DOES inhibit dark adaptation. However, it does it MUCH LESS than white, or other colors. A dark adapted eye that gets low red light will recover faster back to dark adaptation than the same eye exposed to white light of comparable brightness.

So we agree all light effects all of the eyes cells absolutely? BUT low level red light effects the rods the least of all, how is this any different from what we've already posted? :thinking:

 

[Nitro]

People in this thread who claim red is superior haven't indicated they made any attempts to account for this either, I might add.

If I go inside with a white light, even if dim, it does take longer to get my night vision back than if it's red.

 

[MikeAusC]

The right answer for the wrong question ?

If you don't state your question very carefully, don't be surprised if you get the "wrong" answer -

A. What colour light should I use so I can use the least lighting power where I need to recognise colours ?

B. What colour light should I use so I can use the least lighting power where I only need to be able to see fine detail e.g. read text ?

C. What colour light should I use so I can use the least lighting power where I only need to recognise shapes but not fine detail ?

D. What colour light should I use so I can see fine detail e.g. read text, but when I LEAVE this lit area, I will still have maximum sensitivity under starlight ?

E. What colour light should I use where I only need to recognise shapes but not fine detail, but when I LEAVE this lit area, I will still have maximum sensitivity under starlight ?

F. What colour light should I use so I can still recognise colours in low lighting levels, but that light will not affect the sensitivity of Night Vision Goggles to Infrared.


If you can't see that these are questions about very different situations, you're wasting your time on this thread.

If you think the answer to all these questions is the same, you're wasting your time on this thread.

 

[Nitro]

Oh, and about 'no color during stargazing': Sure, the rods do not detect colors. But stars ARE differently colored, and with a large enough telescope you can see those colors with your own eyes. Essentially, the objective opening diameter needs to be large enough to collect enough light. My old school had a telescope large enough -- forgot how large exactly, and unfortunately not often enough available (plus, usually lousy weather in Germany, and a lot of stray light). But once I saw Betelgeuse, and got perfect seeing. Amazing! The air between my eye and Betelgeuse would become perfectly still for just a moment, and the fuzzy blinky blob I saw did shrink to this perfect pinpoint with an amazing red-orange hue. Just beautiful.

I have an 11" SCG. Actually, I can see the colors of the cloud belts on Jupiter, and color in some stars. But it's not enough to see the colors in nebula (bummer). Astrophotography, on the other hand will show colors very nicely.

 

[MikeAusC]

Some stars do have discernible color,

If you mean discernible by the eye, then it just means there's enough light reaching your eye to activate the Cones.

If we depended on eyes only, we could assume that moonlight consisted of only bluish light - but if you take a photograph under moonlight, objects have the same colour as under sunlight.

 

[elgarak]

If you mean discernible by the eye, then it just means there's enough light reaching your eye to activate the Cones.

While searching for papers on dark adaptation, I came across one where the scientist investigated the color perception at low light levels. Turns out that people DO experience color even when the cones are not activated due to low light levels. The current hypothesis is that the brain interpolates colors based on previous experiences (as if the brain goes: "These kinds of objects are most often blue. I make that one blue"), but it's not quite clear what exactly happens.