What is the best flashlight in the fog?

[LuxLuthor]

As yellow said...it's not the bulb/led color or overall output that is the issue. Rather it is the elimination of as much spill as possible. You are going to illuminate the fog in any case, the question is what gives the best penetrating & useful vision. Next time we have some fog, I'll give a ranking of which works best that I have, and see how a camera captures it.

Ictorana, for the record to make sure I am comparing your idea of a 1-2W sealed bulb, what is the exact model/light setup you are thinking so I can compare it specifically.

 

[lctorana]

Any lantern that uses a 4546 sealed-beam bulb (any make).

The host could be an Eveready, a Big Beam, a Ray-o-Vac, a VolKano or even your old Navy battle lantern. But the bulb must be a 4546.

 

[Sub_Umbra]

color is totally unimportant,
the amount of SPILL is important!...

Ding ding ding ding -- we have a winner!

I would add that the tight beam should be held as far from the line of sight as possible.

It ain't rocket surgery.

 

[defloyd77]

It's all about the beam shape and angle of which the light is held. That video comparing the TK20 and TK11 doesn't really prove that a warmer tinted light works better, the TK11 is held closer to the camera, thus making it's backscatter worse and the TK20's beam I believe is more narrow. The tint phenomena I believe is kind of an illusion, I like to call "high contrast backscatter". This basically means that a warm tinted light backscattered with greens and browns behind it will cause an illusion that there's not much backscatter, simply because the warm tint "blends in", do the same with a cool tinted one and the cool tint will contrast greatly with the background. Watch that video again and watch for the camera to adjust it's white balance, you can see the TK20 going from warm white to a very white white and the backscatter looks to be worse and the TK11 also turns to a white white and will appear better.

Pelican now has an updated Little Ed and Stealthlight with 84 lumens now. They were designed with this stuff in mind with their Recoil reflector which shines the LED backward into the reflector and it emits a very tight, no spill beam.

 

[angelofwar]

How about the laser-like beam of the (now) old 19 lumen KL3's? If we ever got fog here, I'd like to try it out...any thoughts?

 

[LuxLuthor]

Any lantern that uses a 4546 sealed-beam bulb (any make).

The host could be an Eveready, a Big Beam, a Ray-o-Vac, a VolKano or even your old Navy battle lantern. But the bulb must be a 4546.

OK, I have that exact bulb in my old Navy Battle Lantern. I'll try it next foggy night. This could be a moment of Incandental Transformation. Ommmmm.

 

[lebox97]

I like this idea, any bystanders will freak out when seeing ground level UFO's as you walk though

Got it! tape your lights to your feet! something with plenty of throw and little spill, yellow or orange colored and light UNDER the fog instead of throwing light straight at it! Works for cars, why not humans?

 

[M@elstrom]

color is totally unimportant, the amount of SPILL is important!

Our car's yellow tinted automotive fog lights penetrate mist/fog better than the non-tinted halogens of equal output/spill, and this is because...

 

[zipplet]

I remember reading that water droplets can reflect shorter wavelengths of light more so than longer wavelengths. Combine this with rayleigh scattering and it would explain why cool blue LEDs seem to create a white wall more so than other tints in fog?

 

[LuxLuthor]

and this is because...

Myths sometimes are believed to be true.

 

[EV_007]

Best flashlight in the fog, or anywhere else, is the one(s) you have on you.

 

[defloyd77]

Our car's yellow tinted automotive fog lights penetrate mist/fog better than the non-tinted halogens of equal output/spill, and this is because...

Check out my post.

 

[M@elstrom]

Check out my post.

I remember reading that water droplets can reflect shorter wavelengths of light more so than longer wavelengths. Combine this with rayleigh scattering and it would explain why cool blue LEDs seem to create a white wall more so than other tints in fog?

Thanks for those informative responses they make more sense than it's a myth, ultimately visual illusion or not lower frequency light output creates less obvious backscatter (or apparent light reflection) thus making it more usable in heavily fogged conditions

Myths sometimes are believed to be true.

Not your best attempt at an explanation Lux' :shakehead

I note there is division as to how effective selective yellow light output can be with an online article from the Alaska Science Forum whereby the author claims they don't work at all, then decidedly turns around and cites a Russian article which concedes "The advantages ascribed to it may take place only in very thin fog or may be subjectively received by some drivers owing to their individual peculiarities of vision."


Isn't that a bit like saying NO but... maybe, just a little :thinking:


Furthermore, if it is said that "the amount of Rayleigh scattering that occurs for a beam of light is dependent upon the size of the particles and the wavelength of the light." then isn't light wavelength (and inherently colour) still relevant to the effect/behaviour of light particles within a mist/fog? :thinking:

 

[defloyd77]

I note there is division as to how effective selective yellow light output can be with an online article from the Alaska Science Forum whereby the author claims they don't work at all, then decidedly turns around and cites a Russian article which concedes "The advantages ascribed to it may take place only in very thin fog or may be subjectively received by some drivers owing to their individual peculiarities of vision."

Thanks for those articles! The Alaska Science Forum one mentions "yellow" sodium-vapor street lamps, they clearly also scatter light just as bad as any other light.

Now here's something that really boggles my mind, my local airport has one of those spinning lights, one side white, the other blue, most likely they are the same wattage, the white one is brighter. Their focus seems the same, but during foggy or snowy nights, the blue one can be seen from a further distance. This goes completely against the blue light scattering theory, but helps my theory of high contrast back scatter as blue light will stick out more than a natural white light, especially if there is any light pollution.

 

[M@elstrom]

Now here's something that really boggles my mind, my local airport has one of those spinning lights, one side white, the other blue, most likely they are the same wattage, the white one is brighter. Their focus seems the same, but during foggy or snowy nights, the blue one can be seen from a further distance. This goes completely against the blue light scattering theory, but helps my theory of high contrast back scatter as blue light will stick out more than a natural white light, especially if there is any light pollution.

Perhaps you too are one of those in the purported minority that experience individual peculiarities of vision OR the blue light scattering issue is heightened when in the presence of a mixed source of light frequencies and not so much so as a single independent lighting source? :thinking:

 

[LuxLuthor]

Thanks for those informative responses they make more sense than it's a myth, ultimately visual illusion or not lower frequency light output creates less obvious backscatter (or apparent light reflection) thus making it more usable in heavily fogged conditions

Not your best attempt at an explanation Lux' :shakehead

So you missed the elegant simplicity of my succinctness, and feel that pedantic verbosity will reinforce the truth? OK, I'll play.

I note there is division as to how effective selective yellow light output can be with an online article from the Alaska Science Forum whereby the author claims they don't work at all, then decidedly turns around and cites a Russian article which concedes "The advantages ascribed to it may take place only in very thin fog or may be subjectively received by some drivers owing to their individual peculiarities of vision."

Isn't that a bit like saying NO but... maybe, just a little :thinking:

This is a case of a person only seeing what they want to see, rather than what is actually written. Let's examine your linked source a bit deeper, shall we? Perhaps the best idea would be to quote the entire article, despite the fact that it was written by an earthquake specialist, which becomes heresay without reference links to what his consulted "experts" actually said.

Do Fog Lights Really Work?
Article #593

by Larry Gedney

This article is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. Larry Gedney is a seismologist at the Institute.

I was asked the other day why fog lights were yellow. When I couldn't come up with an answer, I started asking around and discovered, to my surprise, that apparently nobody else could either.

Skiers, shooters and other outdoor types have long known that yellow goggles or glasses enhance outdoor vision. This is because the yellow lenses filter out the blue part of the spectrum and increase the contrast of a scene. But does the same thing hold the other way around? With the goggles, we are filtering reflected light entering our eyes, but is it possible to illuminate something with yellow light and achieve similar results? The answer, apparently, is no (which is likely to raise strong objections from people who have been using yellow fog lights for years).

For expert advice, I contacted the Cold Regions Research and Engineering Laboratory (CRREL) on Fort Wainwright. Captain John Craig of that group then arranged to have a computer search made on the subject of light penetration in fog and mist from CRREL's headquarters in Hanover, New Hampshire. As a result, I obtained a list of over 200 references and abstracts of articles published by researchers all over the world.

Not a single one asserted that yellow light has superior penetrating qualities, but several specifically stated that it did not. To quote from one Russian article, for example:

"Investigations and practices of automobile traffic do not confirm any substantial advantages of yellow light over white light. The advantages ascribed to it may take place only in very thin fog or may be subjectively received by some drivers owing to their individual peculiarities of vision. Therefore, it does not make any sense to switch over headlights to yellow light, although the use of yellow light in special fog lights does not raise any objections." End of quote. The phrasing is quaint, but the meaning is clear.

I had long thought that the yellow sodium-vapor street lamps that are becoming common were used specifically because they cut through fog better. I found out that there actually is a specific reason for their use, but that it is because they operate on only about half the power of conventional lamps.

So, unless you just happen to like yellow, save your money and forget about so-called "fog-lights." They don't exist.

Again, we don't know what was actually said in the one [Russian] article, but assuming Mr. Gedney did accurately quote the source, it is stated as diplomatically as possible that some drivers who spent extra to buy yellow fog lights are imagining there may be a benefit so as to not look like an idiot.

OK, you feel pedantic verbosity is required for me to back up my invalidated succinct statement. let's see what Google gives us asking it "Do Yellow Fog Lights Work?"

http://www.cartalk.com/content/columns/Archive/2002/February/08.html

Car Talk


Tom: So the question becomes, to yellow or not to yellow? There's a lot of debate about this, but the research says that yellow lights are no better than white lights at penetrating fog. The theory bandied about was that yellow light has a longer wavelength and is therefore less likely to be reflected by the fog particles. Turns out, this is complete poppycock.

Ray: Apparently, the fog particles themselves are so big that they reflect all colors of light. Basically, all light bounces off of them, so using yellow light instead of white light gives you no advantage.

Tom: Plus, in order to get yellow light, what fog-light manufacturers do is put a yellow lens over a white light. That cuts your light output by 20 percent to 30 percent, which is counterproductive.

Ray: So if you live in a coastal area where fog is a real problem and you want to give fog lights a try, we'd suggest a set of high-quality, white fog lights that are professionally mounted to be sure they're aimed correctly. And don't forget to check their aim periodically. Since they're mounted low, they can be knocked out of alignment when you run over things like snow banks and stalled Toyotas.

Daniel Stern Lighting:

What is Selective-Yellow Light?

It's what happens when you subtract blue from the output of a lamp producing white light. But first, what means "white light"? Under US Federal Motor Vehicle Safety Standard number 108 and Canadian Motor Vehicle Standards 108 and 108.1, headlamps as originally installed on motor vehicles (and as installed by anyone other than the vehicle owner) must produce white light. The relevant SAE (and identical ECE) color standards define "white" light as a rather large range within the CIE 1931 colorspace. That's why both brownish sealed beams and bluish HID headlamps are considered "white". It's also why "blue ion" or "crystal blue" bulbs with blue-pass dichroic filters sold to poseurs who want to try to pretend they have HIDs are not considered "white". The light can tend towards a yellow tint to a certain degree and still qualify as acceptable "white" light.

In 1936, the French for tactical reasons wanted a way to identify the registration nationality of vehicles at night. However, they did not want to reduce roadway safety, and wanted in fact to improve it if possible. So, they figured to remove the blue from the output spectrum of their vehicles' front lamps. Some technical papers out of France on the subject can be had here and here. White light with the blue component subtracted is known as "selective yellow" light. It is a pure yellow color with little or no orange component—hence the French yellow headlamps. Yellow lamps have consistently over the years been subjectively ranked as better in poor weather and lower in glare than white ones, but is the effect real? Or is it just a subjective impression?

One problem with this conclusion as drawn from the French experience with selective-yellow headlamps in France is that when the question was being considered, the lamps that were being compared with white lamps reduced the absolute intensity of the beam by about 12 percent. This fact may have had a part in reducing the glare. Because the requirement for yellow light no longer exists (though it remains allowed in many countries) we probably will never know the vagaries of the answer to this question.

What explains the persistent subjective preference amongst experienced poor-weather drivers for yellow fog lamps, despite decades of white fog lamp prevalence? Selective yellow light can improve a driver's ability to see in fog or rain or snow, but not because it 'penetrates fog better' or 'reflects less off droplets' as is commonly thought. That effect is known as Rayleigh Scattering, and is why the sky appears blue. However, it occurs only when the droplet size is equal or smaller than the wavelength of the light, which is certainly not the case with ordinary fog, rain or snow. Roadway Fog droplets are several orders of magnitude larger than visible light wavelengths, so there's no Rayleigh Scattering.

So, why do yellow fog lamps seem to work better? It's because of the way the human eye interacts with different colors of light. Blue and violet are very difficult for the human optical system to process correctly. They are the shortest visible wavelengths and tend to focus in front of our eyes' retinae, rather than upon it. To demonstrate this to yourself, find a dark blue store front sign or something else that's a dark, pure blue against a dark background in the absence of white light—from any appreciable distance, it's almost impossible for your eyes to see the blue lighted object as a sharply defined form;the edges blur significantly. Deep blue runway lights exhibit the same effect; check it out the next time you land at night.

Blue also is a very difficult color of light to look at; it stimulates the reaction we call glare. Within the range of allowable white light, bluer headlamps have been shown to be 46% more glaring than yellower ones for a given intensity of light — see studies here and here. So, it seems culling the blue out of the spectrum lightens the optical workload and reduces glare. For a more detailed examination of this effect with respect to driving in foul weather, see Bullough & Rea's study on the topic.

So, what's the best method of getting selective-yellow light? Until the mid 1990s, headlamps in France were required to produce yellow light. This was accomplished in one of several ways: With a headlamp lens made out of yellow glass, with a yellow glass balloon in front of the bulb either as part of the bulb or as part of the lamp unit, or, more recently, with a yellow-pass dichroic filter coating on a lamp's lens, reflector, condensor or on halogen bulbs themselves.

Cadmium glass was used to make the old French-market Selective Yellow bulbs; now that Cadmium's been more or less banned from auto parts for environmental reasons, the best remaining options are dichroic coatings applied to the bulb or absorption (non-dichroic) filters applied to one of the optical elements—the lens or reflector.

The blue-appearing lenses in many Asian-made fog lamps ("ion crystal", "gold irridium", and other such whimsical marketing names) are coated with a multilayer dichroic interference coating which passes selective-yellow light on axis, i.e., straight ahead. However, these dichroic filters don't absorb/block the blue light, they simply diffract it so it leaves the lamp off axis. So these lamps tend to glow blue when viewed off-axis, and in extreme cases there can be objectionable blue haze outside the brightest areas of the beam. The irridescence of these coatings causes or aggravates secondary-reflection problems where none would exist absent the coating. With the mirrorlike dichroic coating reflecting images of the glowing filament, light goes where it doesn't belong.

Dichroic selective-yellow bulbs are, for the time being, available in some of the common fog lamp bulb formats (H1, H3), though these are going away because no country requires selective-yellow lamps any more. Selective-yellow HID headlight bulbs (D2R, D2S) have been marked by Philips in Japan and other parts of Asia for quite a few years—Philips part numbers are 85122YX and 85126YX—these are now showing up in Europe as well.

For those intent on having selective yellow lights for whatever which reason, applying a coating to an optical element is a more permanent, optically cleaner option that eliminates the need to find and get special bulbs. Good results have been obtained by removing the lamps, cleaning the lenses thoroughly and making sure they're warm, then spraying them with several wet-but-not-drippy coats of Dupli-Color Metalcast yellow, a transparent yellow paint product with good adhesion and durability. Let each coat "flash off" (dry most of the way) before applying the next, and use thin coats so you don't get drips and sags in the wet paint. With each successive coat, the yellow tint will grow deeper. Make it about 2 shades deeper than you think looks right, and it'll turn out well in the end. Of course, the coating needs to be permitted to dry and harden completely before you take the fog lamps out on the road, otherwise dust and grit will become embedded in the still-tacky surface. In the case of lamps with removable lenses, by coating the interior surface of the lens obviously answers questions of coating durability against pitting and scratching. Results of conversion can be seen here.

http://www.lightingresearch.org/programs/transportation/pdf/SAE/2001-01-0320.pdf

A long 2001 pdf file that concludes that further research would be useful.

Driving in Snow: Effect of Headlamp Color at Mesopic and Photopic Light Levels

John D. Bullough and Mark S. Rea
Lighting Research Center, Rensselaer Polytechnic Institute
​

The s/p ratios of currently available
yellow-filtered headlamps do not differ enough from
conventional halogen headlamps for this effect to be
significant in practical situations, but the design of filters
that optimize both transmittance and s/p ratio might
result in yellow- or perhaps orange-colored light that
would provide a measurable benefit under perturbed
atmospheric conditions.

The role of rods in the presence of glare should also be
investigated. If the discomfort glare from oncoming
headlamps could be mitigated by reducing the s/p ratio,
the use of such headlamps might benefit drivers during
inclement conditions. Of course, such benefits would
have to be considered in parallel to possible drawbacks,
such as reduced sensitivity to off-axis targets[25,37,38] such
as bicyclists, pedestrians or animals in clear conditions.

Visual noise is a commonly experienced problem when
driving at night during inclement weather. The results
from this study indicate that filters can decrease the s/p
ratio of light sources, and thus decrease the degree to
which these sources can cause distracting visual noise.
In real-world situations, other factors, such as driver
alertness, color rendering, the spectral and spatial
distribution of roadway lighting, or glare could possibly
mitigate or intensify the s/p ratio's effect on overall
performance. Given the promising results obtained from
this preliminary study, it appears worthwhile to continue
to investigate this problem. By extending this work in the
laboratory and in the field, the practical value of such
research can be more easily understood.

http://www.ibuyautoparts.com/news-536/do-fog-lights-work.html

Here's a segment from "ibuyautoparts.com" which is a bastion of erudite sophistry.

Traditionally fog lights are yellow, and the reason why is the subject of some speculation. A common claim is that they need to be a single color light rather than white light, to minimize dispersion as the light hits the water vapor and scatters in different directions. It is often said that though red might be a more ideal color, it already has connotations to drivers —- it is used for both stop lights and brake lights. Yellow, then, would seem to be the next-most-suitable choice, because it has the next longest wavelength of visible light.

The problem with this idea, which sounds plausible scientifically, has to do with the size of the water molecules in fog. The molecules of water vapor are large enough that dispersion does not occur in any meaningful way, making the wavelength of the light irrelevant. It is possible that the first car companies to utilize fog lights were not aware of the impact that the size of water vapor molecules would have on the dispersion, and so believed that by choosing yellow lights they were minimizing the blur the fog lights cast. More likely is that yellow was chosen because of its connotations in the West with caution. Yellow lights and yellow signs are used to indicate that a driver should slow, look for obstacles, generally use increased levels of caution -- precisely the activities one wants other drivers to exercise when driving in heavy fog.

eHow.com now we are getting into some gold-plated advice:

How Do Fog Lights Work?

By S. Baselice

The idea behind fog lights is to reduce the amount of glare thrown back at you. The fog lights are angled downward toward the road at an angle, so when you turn them on, the light is thrown across the road in front of you and not straight ahead of you, where it can be reflected back. The light is not reflected back into their eyes. This gives you some visibility of the roadway, without blinding you. The color of the lights has no bearing on their use in fog. Today, yellow or any other color is not recognized as being "better" at penetrating fog. It may have more use as a safety mechanism for oncoming traffic.

http://www.autoanything.com/lights/51A22.aspx

Oh yeah, good old "AutoAnything.com" they are my go-to resource on advanced thermodynamics, so let's see what they have to say about yellow fog lights:

8. Are yellow fog lights really better than white or blue ones?

Light coloringThe old wives' tale that yellow fog lights give you greater visibility over white or blue ones is just not true. The premise of that superstition, that yellow light waves are long enough to pass through water particles without reflecting back into the driver's eyes, is based on a misinterpretation of Lord Rayleigh's principle of light scattering. As it turns out, the water particles in fog and mist are entirely too large to have an effect on any light waves from fog lights, be they yellow, white, blue or even green. In other words, any fog light that is properly mounted and aimed is effective, so don't worry about the color.

I could continue this meaningless exercise, but I'm bored now. Sorry for my brevity in this post.

 

[defloyd77]

That's a lotta readin! Well for me at least, I have ADD or somethin. I don't think there was anything that supports my high contrast back scatter theory. I'm not sure I explained it well enough in my previous posts, but as another example, take a red light and shine it at something blue when it's foggy. The red light lit fog will contrast against the blue background, but a blue light wouldn't. Now since there isn't too much blue to be seen when you are driving, mostly greens, grays and browns, the more blue white lights will have the same issue as the red light against a blue background. I guess you could say that yellow light (or any color light that's the same as the background) in a sense "camouflages" the fog.

Make sense?

 

[yellow]

to be honest, I think that every time the brighter the light, bet better.
When it comes to throw: no matter if in vacuum, air, dusty air, fog, underwater, underwater with debrits - as long as there is no spill
(I still adivise to use a bright light with spill reduced. Just try it
That cheap "test" with the adhesive tape makes no cost, does not harm the light, is no effort at all and reversible)

mentioning car fog lights is a good one:
1st: 20-25 years ago, when I was a kid, nearly every car had yellow lights, at least fog lights.
NOW? Any yellow fog lights? Original in the cars?
Why not?

2nd: has one ever disassembled an actual projection beam fog light?
They are this "good", because all the spill is already cut away inside the light. It does not leave it.
No spill to illuminate the fog - better penetration
I dont have the words ready to describe it, but if needed could make a drawing
(by the way: actual fog lights should be positioned high, not low)


PS: I am one of these guys who use high beam in fog - when it is not too dense - because one can see much more distance --> more light, better sight.
Of course it is harder on the eyes, but 10 meters more sight, is 10 meters, in fog.

 

[lctorana]

Lux, based on yellow's post, I evidently must change my recommendation to a 4547 or H7550.

 

[LuxLuthor]

Lux, based on yellow's post, I evidently must change my recommendation to a 4547 or H7550.

No way buddy. You are not jumping up from a 2 to 6W now. I'm locked in on the 4546 !!!!!! No weaseling at the last minute.