Most of my flashlights have CCT of 5000 K or higher and I have two flashlights of 4000 K.
In a recent article about the James Web telescope i read that by means of infrared it can easily pierce through dust. It reminded me that when in a foggy surrounding it is better using a low CCT, say 2300 K to penetrate fog.
My question is are there any of you who have experienced that 2300 K is really noticeably better than say 5000 K for piercing fog and identifying things.
If really so, i intend to buy a Convoy S2+ Nichia 519a 2700 K.
Cars and trucks have been trying all sorts of lights for decades - none of them are any better than standard headlights. I’m surprised to hear that infrared works on dust - I’m guessing the ir light just doesn’t reflect back off the dust, or that we don’t see the reflection.
Weerapat Kiatdumrong seems to like the lower tints (3000k or lower) for wet asphalt and rain and 5000k for fog. He does real tests with many tints
Firefighters round here prefer about 3000k if I am not mistaken. The less away from blu/white and more toward yellow/amber seems to be better at penetration and less backscatter for particles in the air. Yellow has always been a fog/haze driving light color. The beam pattern will matter too, so a dedomed 519 in 3500K or 3000k might work well for you and would end up 2200-3000k. Depending on what you are doing, there is also Osram amber that would work if you don’t need a lot of CRI.
" For light frequencies well below the resonance frequency of the scattering medium (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength, e.g., a blue color is scattered much more than a red color as light propagates through air."
From my understanding, a warmer CCT with less blue will pierce fog better. Fog lights in cars are often yellow, and I suspect that is the reason why.
In my experience, offsetting the light source as much as possible from your line of sight will have a significant improvement as well.
My experience has been that yellow or amber light is vastly better than white light in automotive fog lights used in foggy conditions. Auto fog lights are also made with lenses with a sharp beam cutoff such that about zero light is beamed any higher than the mounting height of the lights.
I would imagine a yellow filter over the lens of a flashlight would be good at making better performance in fog. Perhaps an elliptical optic oriented to spread the light to the sides and reduce light rays going up.
Fog lights were also beneficial in snow so I can imagine the improvement yellow fog beams would have in dust.
So, a yellow filter doesnt MAKE a light yellow, it just cuts out the light that ISNT yellow. With a yellow filter there is not more yellow than before, just less of everything else.
As a result yellow filters are not “cutting through” smoke more, however they may be limiting wavelengths that reflect off the smoke more and increase glare.
That is a bit different than a dedicate yellow light with a yellow emitter. Such an emitter may output more light in the yellow band than say a white light that has a full spectrum including yellow.
On to if yellow (or longer wavelengths) is more effective than other wavelengths.
What is interesting is comparing the spectrum on a sunny day vs the spectrum on a cloudy day.
There is more to discuss here, but frankly i need to look at these charts more.
Still, if someone wants to test, take a full spectrometer out in the sunlight, and then out when its cloudy. See if you get more power in the yellow (or longer wavelength) spectrums under the clouds.
One could also measure a flashlight on a clear night, then measure the same flashlight on a foggy night, again comparing the spectrum and where it drops most, and where it drops least.
Note, this is not quite comparing cct. Yellow is a wavelength, not a cct.
You could conduct a similar test with two flashlights and a light meter. Take two lights, say one with a 519a and a high cct, then the same light with a 519a and a low cct. Measure output of each at a set distance on a clear night, then measure the output of each at the SAME distance on a foggy night. The one with the lower output drop is “better”.
As a logger accustomed to running my skidder 2 hours in the morning before daylight, I can agree that cool lights suck in the fog, smoke or dust. I much prefer the warm lights but good luck finding them if you’re looking for equipment or auxiliary lights. Everything in the parts shops and equipment showrooms is 6500K. It’s so bright, right? Yeah right, until you use them out in the woods or other workplace. Stick with neutral or warm and you’ll be happier.
From my experience with vehicle lighting, I know warm/yellowish color temperature is commonly used in car or 4x4 spotlights or foglights. Somewhere around 2000-3000K seems like a good option. I find the placement of the lights also makes a huge difference to the visibility. Roof mounted spots tend to show every particle and droplet of water you drive into. Low to the ground, floody foglights seem to work best. Some vehicles even have two stock foglight bulbs in the correct location. There are plenty warm CCT options to choose from if you want to replace the bulbs. (Make sure theyre road legal if thats what you intend to do)! Hope this helps a bit!
IMO, you might notice more of a difference if you go for a beam pattern that is more like a spot light than one that’s more floody if you’re worrying about fog, rain, snow, smoke, or even trying to navigate through dense brush.
Thank you all for sharing your knowledge, experience and thoughts concerning the subject.
I’ve learned much more.
The main reason i’ve asked my question is that i am looking for a suitable CCT for walking the dog, or riding home on my bike during a foggy evening.
I live in the Netherlands nearby woods and pastures and since a decade or so, wolves have been migrating from Central Europe through Germany into the Netherlands and settled here.
Now i do know wolves normally will avoid encounters with humans but since the Netherlands is a densely populated country, wolves are much more accustomed to presence of people than for example the wilds of Northern America.
So when riding home on my bike or walking the dog in foggy evenings i would like to have a good vision ahead of me.
I think i’ll order a Convoy S2+ with a 3000 K Nichia 519a or S2+ with XML2 T4-7A.
Which one would be better for my purpose ?
(1) CCT/color absolutely matters. The inverse correlation between wavelength and backscatter is a known fact.
(2) Spot/flood preference depends on your usage. Spot is probably more useful if you want to see any distance at all.
(3) Both the 519A and XML2 have too low output and are too floody. Consider the XPL-HI in 7A tint, which is throwier with decent output. If you really want throw, consider the Osram yellow or red, sacrificing output and color rendering for maximum throw and visibility through fog.
Whether you have cool or warm light you will still get a washout in front of you if you shine it into fog, seen it hundreds of times during camping.
for seeing in fog (as much as it is possible, cuz there is absolutely no light source that will go thru it unaffected) you need a beam with as little of spill as possible, but the beam itself is not the only thing that matters, it is where you shine it, you want as far as possible from your eyes. there is a reason why fog lights on cars are installed at lowest possible point. not saying you have to clip a light to your feet, but i have noticed that if someone else shines a light, me staying away from them allows me to see better than those people with the flashlight, even if they use cool white tint.
So you really should not be worrying much about cct, but about your optics. a 4000-4500k will be just fine for almost any situation, fog or not.
The advice about aligning the light’s axis away from your eye’s direction of view is excellent, water droplets are essentially retroreflectors and will reflect less back when viewing the beam off-axis.
It is true that you still still get a washout whether warm or cool, but the washout is noticeably and usefully less with warm. There’s a huge difference in fog penetration between my S2+s in 5700K and 4500K, same driver/optics. The difference will be even greater if one goes for a much lower CCT.
I’m surprised nobody has mentioned the Convoy S3 with B35AM or 719A 2700K yet. Being 6V LEDs, those mean it will have a boost driver, which should improve efficiency and output stability on high.
