Night Adapted Vision: Why so Much Hype in Preserving It?

To be sure, I have no doubt that if you think about it long enough you will be able to come up with a scenario or two in which this would be important (or perhaps only somewhat convenient). In either case, by all means, feel free to list any scenarios you come up with. I'm actually curious to see if there are many (or any) scenarios that an average person encounters frequently enough to justify its (night-adapted-vision's) high position on the "consistently and thoroughly examined points of discussion" list.

Let me explain where I'm coming from. I see a lot of posts on here that indicate no tolerance for lights that don't come equipped with either an ability to operate in the .000001 lumen neighborhood, or with a red light that serves the same purpose - preserving night adapted vision. Don't get me wrong. I'm a gadget freak, so I would rather have a product that can do a bunch of cool things over one that can't. Therefore, on the surface I tend to actually agree with the line of thinking that I'm now questioning. What pushed me over the edge to bring this up was that I have just noticed how *important* this function seems to be in so many peoples' minds.

So I have to ask, if it's nighttime and you want to read a book or take a walk (or do whatever) and all you have is a flashlight that can only descend to the depths of the 20 lumen threshold, for example, and you therefore have to momentarily delay your continued enjoyment of this highly touted night adapted vision, why did your panties just get tied in a knot over this? Your night adapted vision will come back momentarily, won't it? It's not really that critical for you to have right now, is it? After all, if you really do need to see something in its full brilliance again within the next few seconds, you still have your flashlight, don't you? Isn't the point of a nice light to artificially transform the night into day and thus, by definition, render your night adapted vision momentarily unnecessary?

Okay, enough out of me. That's all I have for now. Please tell me if I'm missing something.

~

(Quoting you) :
"Your night adapted vision will come back momentarily, won't it? It's not really that critical for you to have right now, is it?" ...........


I understand , but yes , there might be times when it is critical .

~

Anonnn said:

To be sure, I have no doubt that if you think about it long enough you will be able to come up with a scenario or two in which this would be important (or perhaps only somewhat convenient). In either case, by all means, feel free to list any scenarios you come up with. I'm actually curious to see if there are many (or any) scenarios that an average person encounters frequently enough to justify its (night-adapted-vision's) high position on the "consistently and thoroughly examined points of discussion" list.

Let me explain where I'm coming from. I see a lot of posts on here that indicate no tolerance for lights that don't come equipped with either an ability to operate in the .000001 lumen neighborhood, or with a red light that serves the same purpose - preserving night adapted vision. Don't get me wrong. I'm a gadget freak, so I would rather have a product that can do a bunch of cool things over one that can't. Therefore, on the surface I tend to actually agree with the line of thinking that I'm now questioning. What pushed me over the edge to bring this up was that I have just noticed how *important* this function seems to be in so many peoples' minds.

So I have to ask, if it's nighttime and you want to read a book or take a walk (or do whatever) and all you have is a flashlight that can only descend to the depths of the 20 lumen threshold, for example, and you therefore have to momentarily delay your continued enjoyment of this highly touted night adapted vision, why did your panties just get tied in a knot over this? Your night adapted vision will come back momentarily, won't it? It's not really that critical for you to have right now, is it? After all, if you really do need to see something in its full brilliance again within the next few seconds, you still have your flashlight, don't you? Isn't the point of a nice light to artificially transform the night into day and thus, by definition, render your night adapted vision momentarily unnecessary?

Okay, enough out of me. That's all I have for now. Please tell me if I'm missing something.

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Preserving night adapted vision helps to make a person feel a little more secure. He/she can see what is going on around in near darkness. This is especially true if the person is running away from something or trying to not attract attention to themselves but still need to see and/or find an escape route quickly in case something happens. Imagine blinding yourself for those few moments, only to get your night vision back and have something in your way that wasn't there before? It's very disconcerting...

Its my understanding (and experience) that there are levels of adaptation and that when folks complain of 'blowing their NAV', its not the few seconds kind but the few hours kind that they've lost.

Not only that, If your eyes are accustomed to darkness, suddenly flooding your retinas with light strains your eyes alot, especially with the pupils that dilated, the amount of light coming in can cause short and long term harm. The stress that your iris goes through while snapping shut...and also, it just physically freaking hurts to be blinded

As with so many things, it just depends on the context.

For example, you are a soldier, in combat, in a hidden position, in the middle of an enemy engagement, during a pitch black night...and you just received orders to proceed to point XYZ and reinforce ABC before they are overrun.

OKY DOKY THEN...where IS XYZ? Uh uh, gotta read the map...hope no pesky enemy combatants notice the glow from my foursevenM18 flashlight...

Click



Ok, here we go, XYZ is over there, we follow the river bank for cover, climb the ridge HERE, and dig in to form a defensive line HERE to protect ABC, OK men, lets GO!!!!

click



Sheet, I can't see a damn thing, you'll need to turn your flashlight on again...

click

Sweet! I can see everything! - There's the trail, there's the river off in the distance, and, [machine gun and rpg and so forth noises....]

ugh legh Daq Dun flashlight Daq Heghpu' !

IE: Sometimes, your job requires you to be able to move at night w/o a flashlight, and with night adapted vision.


Substitute a SWAT team bursting into a dark warehouse at high noon - and the perps are crouched in the shadows, waiting to see the cops so they can open fire first and gain the advantage...and the cops are coming with beacons letting everyone know where they are as the cast shadows from their search lights strain to see their shadowed nemisis.

The bad guys eye's are adjusted, they can see in the darkened warehouse....the cops are glowing piniatas :candle:


So, primarily, if you need to move about without light, later, you need time to let your eyes readjust to the dark, and that can take HOURS rather than minutes, again depending on if your eyes had already adjusted, and the light use was brief, or if you're starting from scratch.

For civilians, its typically not life and death, as its rare they CAN'T have a light. On the other hand, if you want to go for a nice moonlight stroll, do some star gazing, etc...you just can't do it with a flashlight that's going to make your eyes think its daylight again....you won't be able to see the moonlit landscape, the stars, etc...just the ball of light you're moving within.

If you're hunting, or committing a crime perhaps, you might not want to turn your position into a lighthouse...you might want more stealth, etc.

So, sure, sometimes its stupid to not use a light,and sometimes it IS stupid....and, after that, its a question of DEGREE.

TEEJ said:

As with so many things, it just depends on the context.

For example, you are a soldier, in combat, in a hidden position, in the middle of an enemy engagement, during a pitch black night...and you just received orders to proceed to point XYZ and reinforce ABC before they are overrun.

OKY DOKY THEN...where IS XYZ? Uh uh, gotta read the map...hope no pesky enemy combatants notice the glow from my foursevenM18 flashlight...

Click

Ok, here we go, XYZ is over there, we follow the river bank for cover, climb the ridge HERE, and dig in to form a defensive line HERE to protect ABC, OK men, lets GO!!!!

click

Sheet, I can't see a damn thing, you'll need to turn your flashlight on again...

click

Sweet! I can see everything! - There's the trail, there's the river off in the distance, and, [machine gun and rpg and so forth noises....]

ugh legh Daq Dun flashlight Daq Heghpu' !

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dc38 said:

Not only that, If your eyes are accustomed to darkness, suddenly flooding your retinas with light strains your eyes alot...and also, it just physically freaking hurts to be blinded

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This.

I don't care that much about my night adapted vision when I get up to whiz in the in middle of the night, but I don't like the uncomfortable blast of light that comes from a lightbulb or very bright flashlight at that point. It just plain hurts. So for me, the T1A is a perfect bedside light; I just dial it up from zero to whatever I need to navigate. The same with sleeping with others in the same tent or bedroom; it's nice not to shine the light in their eyes when you wake up and need to look at something or move about. I would guess that for most of us who like a low low, it has more to do with those reasons than actually preserving our NAV, although that certainly sounds more exciting.

Anonnn said:

..........Your night adapted vision will come back momentarily, won't it?........

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If by momentarily you mean 20-30 minutes or more, than yes, it will return eventually. When camping, especially when stargazing, or on a night-hike or other nocturnal outdoor pursuits, I'd always rather rely on ambient light if possible, if my eyes are night-adapted and there is even a little bit of moonlight overhead, I usually don't need any light at all. If you don't get it, you just don't get it. I personally do get very annoyed when someone shines a light in my eyes or even shines a really bright light in my vicinity if my eyes are night adapted. My ideal flashlights for outdoor pursuits at night use Nichia LED's, like one of my Arc AAA, Infinity Ultra, or lower powered headlamps. I use a headlamp with one or two red Nichia LED's to read in bed every night so I don't disturb my wife who is sleeping.

Anonnn said:

To be sure, I have no doubt that if you think about it long enough you will be able to come up with a scenario or two in which this would be important (or perhaps only somewhat convenient).

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For me it's mostly about maintaining situational awareness and discreetness simultaneously, without using unnecessarily bright light that attracts attention or bothers others (who may be sleeping, for example), as well as being able to see better when I'm doing amateur astronomy (no flashlight in existence can throw that far ). That in addition to getting things done.

Anonnn said:

Let me explain where I'm coming from. I see a lot of posts on here that indicate no tolerance for lights that don't come equipped with either an ability to operate in the .000001 lumen neighborhood, or with a red light that serves the same purpose - preserving night adapted vision.

Click to expand...

Most people don't always need to preserve their dark adaptation--even amateur astronomers don't care when they're observing the Moon, for example, which is so painfully bright in telescopes that filters must be used--but whenever they do need to, then they need some help from their flashlights.

Anonnn said:

Don't get me wrong. I'm a gadget freak, so I would rather have a product that can do a bunch of cool things over one that can't. Therefore, on the surface I tend to actually agree with the line of thinking that I'm now questioning. What pushed me over the edge to bring this up was that I have just noticed how *important* this function seems to be in so many peoples' minds.

Click to expand...

It's because some people, particularly those in the military, actually use their dark adaptation and their flashlights as tools rather than cool gadgets.

Anonnn said:

So I have to ask, if it's nighttime and you want to read a book or take a walk (or do whatever) and all you have is a flashlight that can only descend to the depths of the 20 lumen threshold, for example, and you therefore have to momentarily delay your continued enjoyment of this highly touted night adapted vision, why did your panties just get tied in a knot over this? Your night adapted vision will come back momentarily, won't it?

Click to expand...

Dark adaptation takes longer than that to fully return once you've exposed your eyes to excessive levels of illumination. Keep in mind that many people rarely use dark adaptation, or even achieve it while they're still awake, so they don't have an intuitive understanding of what it's about--they typically turn on a bright light as soon as possible, and then it's completely gone. Other people use dark adaptation all the time and have learned to see more with it, as well as make use of limited amounts of light from their flashlights.

Anonnn said:

It's not really that critical for you to have right now, is it?

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Right at this moment, staring at a computer monitor, no, but at other times, absolutely yes.

Anonnn said:

After all, if you really do need to see something in its full brilliance again within the next few seconds, you still have your flashlight, don't you? Isn't the point of a nice light to artificially transform the night into day and thus, by definition, render your night adapted vision momentarily unnecessary?

Click to expand...

The point of a "nice" light is to be a tool that helps me perform tasks and achieve goals that I've set out to achieve, not necessarily to banish the darkness with excessive output just for the sake of it.

Anonnn said:

Okay, enough out of me. That's all I have for now. Please tell me if I'm missing something.

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I think what you're missing is the perspective of using flashlights as tools in conjunction with getting things done in an efficient manner as opposed to using brute force. I play with my flashlights as toys, too, because I think they're cool, but I have other things to get done, and nothing is better for that than using effective tools in the most optimal ways possible.

The functional value of using lower output levels recently clicked for me upon reading part of the FAQ on the HDS System site under "How Can I See Further?" and their white paper on LED Flashlights. I wasn't aware that vision response to light was logarithmic.

I've recently started taking night walks in the woods and find that preserving night vision to be most valuable. I've experimented with different outputs and found that higher outputs to be almost claustrophobic in that they create a tunnel of vision. When using outputs above 200 lumens night vision is impacted and outputs above 500 create a tunnel of vision where there isn't any visibility in the periphery due the contrast of flashlight and ambient light. I've found that running my Quark 123^2 X on the moonlight and low works well most of the time and bumping up to medium when needed.

The whole point of the light is usually to see better unless the idea is to impair someone else's vision, or get someone's attention at a distance.
Turn too much light on, get tunnel vision while showing the countryside where you are, then turn the light off and what was a dimly lit but comprehensible becomes dark and confusing.
Just enough light to get the job done, bright lights are great when there is a need but most of the time staying close to ambient light levels and noise levels is the most satisfying to me.

I don't like the eye pain either, but there's enough street lighting here at night that I rarely get enough adaptation to really suffer much from flipping a light on.

Well, I know I'm certainly one that's always preaching the virtues of moonlight. I agree with everything everyone has already said above with regard to the question of preserving night vision.

However, preserving night vision is only but one advantage of ultra-low lumens ("moonlight" and <1 lumen).... it seems to me the question is really, "is it worth limiting your flashlight selection just for moonlight?" For me, yes, absolutely, and here's why.

- Runtime - the low electrical draw provides massive runtime and emergency use power ... 200, 300, 400 hrs from a single AA
- Less disturbing to others - reading a book in the passenger seat of a car driving at night, checking on your kid sleeping, simply not being obnoxious in a crowded venue.
- Maintain your stealth (already mentioned by others). I stealth camp (RV, backpack, bicycle, and kayak), in places I know I shouldn't be, I prefer not to attract attention when I do so.
- Battery vampire - in a really bad situation (SHTF?) I know my moonlight mode with take dead batteries from any sort of electronic device with a cut-off (0.9V usually), and then run for many hours. High draw devices tend to trip the shut-offs before the batteries are really dead, while moonlight drawing 1ma can get that last percent or two from the batt.
- Simply lazy - why bother with having to charge, and change batteries once a week when I can change once every 3 weeks? I like using the minimal amount lumens to accomplish a given task (for me, that's usually 0.2 and 4 lumens) ... why change batteries 3x more than I need to?

I'm a camper that would rather not sit in the dark. So when I'm camping at night I'll run my light (single AA btw) for 4+ hours straight, every night. Anything above a couple of lumens and I have to start watching the clock, and make sure I've got spare batts. Anything on moonlight is effectively free and indefinite light (200-400 hours) for the term of my trip. And I can live with only moonlight if I had too - just have to work a little more aiming the hotspot for certain task.

In a survival situation... I know my light will be working a loonngggg long time after most other become paperweights.... what's that worth?

reppans said:

- Runtime - the low electrical draw provides massive runtime and emergency use power ... 200, 300, 400 hrs from a single AA
- Less disturbing to others - reading a book in the passenger seat of a car driving at night, checking on your kid sleeping, simply not being obnoxious in a crowded venue.
- Maintain your stealth (already mentioned by others). I stealth camp (RV, backpack, bicycle, and kayak), in places I know I shouldn't be, I prefer not to attract attention when I do so.
- Battery vampire - in a really bad situation (SHTF?) I know my moonlight mode with take dead batteries from any sort of electronic device with a cut-off (0.9V usually), and then run for many hours. High draw devices tend to trip the shut-offs before the batteries are really dead, while moonlight drawing 1ma can get that last percent or two from the batt....

...In a survival situation... I know my light will be working a loonngggg long time after most other become paperweights.... what's that worth?

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+1 all of the above.

For me it is typically wanting to avoid blinding myself and waking up others. Also, for me at least, it wakes my brain up too much when I use too much light.

I first realized the importance of this when I got my first Fenix L2D-CE several years back. It had a low of 10 emitter lumens which would hurt my eyes every time I used it in the middle of the night. I found myself wishing for something much dimmer than that.

Low and behold 4sevens comes out with the moonlight mode(0.2 lumens) on the Quarks and I had to try it. It was fantastic. Would you believe it that not long after that I ended up wishing that was a little dimmer, too. So along comes Thrunite with the Neutron 1A and Firefly mode(0.09 lumens) and I am completely satisfied with that low level.

So for me anyway the really low level is very important and gets used every night. I live in the country and there is very little ambient light so my eyes get dark adapted every night after bedtime. It is not cave darkness but much darker than even in a small town.

Given enough time to adapt, you'd be amazed at how little light it takes to see where you're going. Reading with a sub-lumen light though would force my eyes to focus on the words with the part of my vision that sees poorly in low light, and would either not work at all, or cause a lot of eye strain.

So - We have come to the same conclusion we always do - If adapted night vision works for you and your situation, its great, and if it doesn't, it sucks. If bright lights work for you in your situation, its great, and if it doesn't, it sucks.

The low levels are extremely useful to me. I also live out in the country where the ambient light is almost zero. Initially i was going out, light blasting, wow look at that I can light up the whole property and more. Now I take the dogs out in the dark and gradually increase the light to the minimum i need to see the immediate area. Now I am finding that the spill allows me to see the immediate area but also enough of the surrounding area to be useful and evaluate for anything requiring attention, possibly more light to identify, possibly have a firearm brought to ready. So now I enjoy skulking around with little or no light, but always ready to light up the country side

Amateur astronomy is an example of where you would like to preserve your night vision but you need a bit of light from time to time to read or adjust equipment.

A private (VFR) rated pilot flying at night needs to read instruments but otherwise preserve night vision.

A hiker generally uses the least amount of additional light that it takes to be safe. More just limits peripheral vision. Light that makes it harder to see isn't optimal.

Even just taking your garbage out at night is an example. Sure 20 lumens is fine there but the concept is the same. You can take your garbage out with 300 lumens but in that case 20 is much better.

It takes much more than a few seconds or minutes to regain full night vision but only one bright blast of light to lose it.

Sure, some people exaggerate how much they need .004 lumens or how they find .2 lumens blindingly bright but the main point is usually just that a flashlight with a low of 30 lumens is generally not really low enough for many people if you use your light a lot at night in camping or hiking or dog walking situations.

Is this really a question that is not understood? I think the OP is more due to annoyance derived from reading of people obsessing on this subject rather than the actual subject.

I have on the top of a nine volt a led outputting .03 lumen. It is enough to do a ceiling bounce in the bathroom and be able to see. Seeing how a carbon zinc 9 volt can run it for 3 months 24/7, I see no reason not to have it around.

I was thinking about the same thing. I'm still young( a student that is) so I never really wake up in the middle of the night to do some stuff.

What I carry in the house is a fenix E05. After turning off all the lights, its the one I use to walk around and go to bed. Its enough for me and not blinding since its only 27 lumens. One night, I woke up at 3am and needed to go to the bathroom so I took the E05 and turned it on. HOLY COW! I just blinded myself with the mere 27 lumens of the E05. So I just took the HDS which was programmed at .94 and used that instead.

So if the one talking about using moonlight here is only at his own home, its not preserving that we are talking about but the only way to remove our Night Adapted Vision is by blinding the crap out of ourselves.