Real World Review - LED's that cut through

Real World Review by ZeSpectre (0610.17)

North Arlington doesn't really get a lot of fog but we got socked in late last night! By the happiest of coincidences the streetlights in the parking lot behind my place were out as well so I got some quality "lightsaber" time in :naughty: .

Now as we're all well aware, a lot of LED based flashlights suffer a pretty strong "bounceback" effect in fog where the light doesn't really punch through but just sort of diffuses and creates a well lit wall of fog that you can't see through.

I'm happy to announce that there are a few more LED based lights that can be added to the list of "fog cutters".

MiniMagLED 2xAA and MiniMagLED 3xAA - Of course the 3xAA light was stronger but both lights actually did an very acceptable job of punching into the fog bank.

MagLED drop in for 3xD - WOAH! To my complete astonishment this light punched through fog almost as well my MagCharger (my yardstick for fog situations).

Night-Ops Gladius - Well we sort of already knew this but I thought I'd just re-iterate that it does a good job in fog.

AND the FAILURES

Coast V2 6 LED - The all flood beam just bounced right back and was essentially useless.

No name 20 LED "Showerhead" light - Failed for the same reason as the coast light.

Actually what really determines whether a light ''punches through'' smoke/fog? Is it the texture of the reflector, the amount of lumens, or the amount of throw the light has, or colour temperature??

I'm pretty sure it's the tint or color that punches through fog. A V1 or V0 tint LED would be the best tint to use for foggy outdoor use.

Tachy

nutz_about_lights said:

Actually what really determines whether a light ''punches through'' smoke/fog? Is it the texture of the reflector, the amount of lumens, or the amount of throw the light has, or colour temperature??

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Obviously throw, if you look at his results The texture of the reflector changes throw. The light output changes throw. The color could make a small difference, but as far as I know, nobody here has isolated what that might be.

Loomy said:

Obviously throw, if you look at his results The texture of the reflector changes throw. The light output changes throw. The color could make a small difference, but as far as I know, nobody here has isolated what that might be.

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Exactly. I took out my Pelican M11 (incan) in the fog last night- I needed to find my dog in the backyard. It punched through the fog like a warm knife in butter. Ok, I'm terrible at cliche's and I'm certain I eviscerated that one. Anyway, I'm sure it is throw first, then perhaps tint.

Did you try the River Rock 2 AA w/spotlight optic (which also does a good job in fog) to compare it to the MagLEDS?

nutz_about_lights said:

Actually what really determines whether a light ''punches through'' smoke/fog? Is it the texture of the reflector, the amount of lumens, or the amount of throw the light has, or colour temperature??

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IMO it would be the narrowest possible beam, held with the arm extended downward as far away from eye level as possible.

It's easy to envision the beam of a light with a lot of spill lighting up the fog (or smoke) right in front of your eyes and making the target impossible to see.

With a narrow beam held low you will not only find yourself looking through less light splashed onto the fog between your eyes and the target, but the splash that does still occur will be farther from your eyes and take less of a bite out of however much dark adapted vision you may have to work with at any given time.

One of these days I'm going to work up a graphic that makes this easier to understand.

Here we go:

If you click on the imagelink above you'll see that although in both examples the user is looking through the same amount of fog, in the upper example the combination of a floody beam held at near eye level means that he must look through a great deal more fog that is reflecting light right back into his eyes than the lower example.

In the lower graphic the user is lighting up much less fog and much more target, comparatively.

Okay, I'll try to address all of this at once <grin>.

First, I would say the PRIMARY factor for fog penetration is the reflector or optics. This is easily 80% of the difference. The really bizzare thing is the lights with output that would be described as "ringy" seem to do better than flat and even output (Inova T4, MagLED module, and in incandescent world my old "reproduction" 1920's leather wrapped light). I wonder if this has to do with interference patterns in the "rings" canceling returning or "bounced" light but I have absolutely no way of testing this theory.

(Yes, C4LED, I also used the 2xC River Rock with that no-spill optic and it penetrated far better than you might expect considering the output from that light vs say the MagLED drop in)

Tint does, however, seem to be another factor. The lights that have a slight bluish cast do really seem to "cut through" better than anything with a greenish tint. Yellowish seems to help some and pure white is the worst.

Sub-Umbra, great graphic! Can I please have permission to use it in the future? The really intersting thing with LED based lights though is that the super floody lights (Coast, showerhead, L2) can still create a blinding wall even when held low as you illustrate. The only thing I can compare it to is the diffusion effect you get when you shine a laser into a drop of water and it bounces around effectively illuminating the whole drop. (wish I could find a picture of the effect I'm referring to).

zespectre said:

...Tint does, however, seem to be another factor. The lights that have a slight bluish cast do really seem to "cut through" better than anything with a greenish tint. Yellowish seems to help some and pure white is the worst.

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I agree that blue tints may be superior but it's a hard sell to many. Most fish see best in the blue part of the spectum because wavelengths in the blue range penetrate water the best...and fog is water, too. I have a CYAN LuxIII @ 495 nm that will light up the side of a house at two full blocks through the rain in very low ambient light situations. I wouldn't guess how much of a factor tint is, but I'd bet it is a factor.

zespectre said:

...Sub-Umbra, great graphic! Can I please have permission to use it in the future?

Click to expand...

Yes. You might want to copy it to your hdd as I still have a thing or two to add, like a verticle line through each beam showing the relative difference in size of the potential reflective area that may splash light back into the user's eyes.

zespectre said:

...The really intersting thing with LED based lights though is that the super floody lights (Coast, showerhead, L2) can still create a blinding wall even when held low as you illustrate...

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Definately. The angle that a floody light is held at in smoke or fog may minimize the splash a bit but not very much, IMO. Maybe I was trying to show too many thing with just two examples -- I picked the extremes -- floody/high angle Vs. throwy/low angle. I thought about using four examples.

Sub_Umbra said:

Maybe I was trying to show too many thing with just two examples -- I picked the extremes -- floody/high angle Vs. throwy/low angle. I thought about using four examples.

Click to expand...

I just think there is an extra element to LED based lights and fog because if I hold a floody incandescent low and pointed at a fog bank I get -some- reflection and some penetration. However certain LED based lights (especially the floody, pure white, ones) held low turn fog into an impenetrable wall of glowing white cotton. I have the worst time describing the effect until I actually show people what I mean then they are all like "oh yeah, that's weird!".

Someday I'll get a U2 and fog at the same time and see if it has the same effect as the L2

zespectre said:

I just think there is an extra element to LED based lights and fog because if I hold a floody incandescent low and pointed at a fog bank I get -some- reflection and some penetration. However certain LED based lights (especially the floody, pure white, ones) held low turn fog into an impenetrable wall of glowing white cotton. I have the worst time describing the effect until I actually show people what I mean then they are all like "oh yeah, that's weird!".

Someday I'll get a U2 and fog at the same time and see if it has the same effect as the L2

Click to expand...

In my reality map that may make sense for a couple of reasons:

1. Most of the incans probably have more power than the LED lights, so even if floody they may have a stronger hotspot to begin with, hence, greater penetration.
2. 5mm arrays (like the showerheads) may be composed of LEDs with 15-45° beams or even even greater! They'll blow back all over you no matter what you do.

I will chime in, although it won't add anything.

IMHO, the biggest difference in fog is, as pointed out by Sub_Umbra, the angle of incidence versus centre of vision. That is why front fog lights on a car are much lower than the main lights, and have a flatter beam. If anyone has driven in thick fog, with their dipped lights off, and turned their front fog lights on, you will know the strain it takes off the night vision because you are no longer driving into a white wall. Yes, the beams are flatter, and they don't project as far, so I know it isn't quite the same as above, but I think the general premise still holds true.

So far this all seems perfectly logical.

When I lived in the SF bay area I always noticed that the fog was thinner close to the ground. If I stood in the fog I could easily see objects close to the ground (say, walking behind a person- I could see their ankels and feet but no details above the knees). Hence, when I installed foglights on my cars they were installed under the bumper, providing less glare and more visibility of the road below the fog.

Tint has an effect.

If you look at a light shining towards you in fog, it looks yellow. That is, the yellow part of the light penetrates the fog better. This is why yellow lights are used for car fog lights and for street lights in fog prone areas.

All other things being equal, incandescents work well in fog because they emit more strongly in the yellow part of the spectrum.

In my experiences, my MagLED got about as far as my Tec-40 in fog.

Has anybody ever tried an amber LED in fog conditions? I'm curious of the results.

The people who make car headlight systems know about fog and lights. I have seen 'white papers' on fog lights, but it was before the internet existed so don't know if Google can find them. IIRC flat-top yellow beams have been the fog lights of choice for rally cars for many decades. White, floody beams with significant output above eye level are the worst.
Greg

I wonder how a green LED with some punch would do in fog? I've never seen green fog lights, but since your eyes are more sensitive to the color green, maybe it would help cut through the wall of light created from white lights. Anyone have a HID light and a green filter?

Awhile back I took some pictures in my garage with a fog machine and some of my lights to see the beam characteristics. If anyone is interested I could do some more with different lights this weekend. These are all LED lights but I do have some incans too.

garageguy said:

Awhile back I took some pictures in my garage with a fog machine and some of my lights to see the beam characteristics. If anyone is interested I could do some more with different lights this weekend. These are all LED lights but I do have some incans too.

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Aren't fog machines fueled my chemical fluids? That's different than the water mist presented in natural fogs. Great shots though.

Garage Guy,
Nice shots!
But I have to agree with outdoors fanatic because I've used flashlights around "fog machines" before and although it's great for doing beamshots (as you so well demonstrated) I have yet to see quite the same "illuminated cloud" effect that happens with water vapor.