Science behind flashlights’ different beam colors

XTAR Light

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Flashlights LEDs produce different colors by using various materials, which produce photons at different wavelengths. Those individual wavelengths appear as light of different colors. Red LEDs use the aluminum indium gallium phosphide (AlInGaP) material system. Blue, green and cyan LEDs use the indium gallium nitride (InGaN) system. Together, AlInGaP and InGaN cover almost the entire light spectrum, with a gap at green-yellow and yellow. One method of achieving a larger spectrum of colors is to mix different colors of LEDs in the same device.

Combining red, green, and blue LEDs in a single LED device, and controlling their relative intensities can produce millions of colors. Additionally, combining red, green, and blue in equal amounts produces white light.
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Different lighting colors have different meaning, and look at what they are generally used for:
*White: great for all around, every day illumination.
*Red: ideal for camping, navigating the way in the dark, preferred by people who are trying to save their night vision. And red light is the universal signal for caution and safety.
*Green: suitable for hunting. Many hunters claim animals are not frightened off by green lights.
*Blue: great for tracking blood trails along the foliage, it can be used by hunters, police and crime scene investigators. And blue light can cut through fog, which is widely used for fog headlights.
*UV: it’s aids in authenticating money, driver’s licenses, and other documents by making the special watermarks fluoresce. UV light can also make blood and other bodily fluids easily visible. Stains left by mice, dogs, cats, and other animals will also fluoresce under the UV light...

Upon your demands, do you prefer flashlights with single white light or colorful lights? And how do you use them?
 

Olumin

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I`m not quite sure That`s true, light shifted towards Longer wavelenths travel better through fog particles, higher frequencies collide more with them and give a lot of back scatter.

Factually correct, however, human eyes are somewhat more sensitive to blue and green light then red, hence blue light appears brighter to us in most circumstances. You can test that yourself by comparing the light of two flashlights of same or similar luminosity and different color temperatures. The cold-white light will appear brighter to you compared to the warm or neutral white light despite same actual brightness .
 

defloyd77

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I have NEVER seen blue fog headlights, in fact, if fog headlights are colored, they're yellow and that's to eliminate blue from the beam.

Regardless, it's been proven it's just best to go with white light that's aimed and focused right.
 

lightfooted

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I have NEVER seen blue fog headlights

And there is a reason for that. In the UK, US and Canada...blue lights are reserved specifically for Emergency vehicle use ONLY. In WA State it is illegal to display a blue light on your vehicle that is visible to other drivers, at all. At least on public roadways.
 

XTAR Light

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Thanks for your explanation! And blue light is also for nice fishing at night as it shines straight through the water without producing any glare.
 

defloyd77

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Blue light enables you to see more fog. I'd rather see the curb.

I've discussed this a ton in the past, so I hate to beat a dead horse, but that simply is not true. I'd be as bold as to say that 95% of "information" out there about the uses of colored lights is false and contradictory. From night vision preservation, to fogcutting and even blood tracking, the thing that's best for you is a good, quality source of white light.
 

desert.snake

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When I had a flashlight with a blue diode, I deliberately cut my hand to get blood, it does not start to be more noticeable, it is just black, like any other liquid, except those prone to phosphorescence. High CRI white LED shows blood best.
 

defloyd77

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When I had a flashlight with a blue diode, I deliberately cut my hand to get blood, it does not start to be more noticeable, it is just black, like any other liquid, except those prone to phosphorescence. High CRI white LED shows blood best.

I've never tried it on actual blood, but in the past I've tested red and blue light together on ketchup and I was really surprised at just how much that combination made the ketchup stand out like a sore thumb. I didn't have any high CRI lights back then to compare to and I no longer have any blue lights to compare to the high CRI lights I have now. I'd be really curious to see how they compare, I actually have blood in my yard thanks to a pair of killer stray kittens that have been hanging around our house.
 

-Virgil-

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blue light can cut through fog, which is widely used for fog headlights.

This is not even partially true.

if fog headlights are colored, they're yellow and that's to eliminate blue from the beam. Regardless, it's been proven it's just best to go with white light that's aimed and focused right.

No, what's actually been proven is that the folksy "explanations" and quasiscientific nonsense about yellow light penetrating fog better is a bunch of hoo-hah. This page and this one have what I have long considered to be dependable and correct information on the subject, not least because they have direct links to the full texts of relevant, rigorous studies by recognized expert scientists...not just a bunch of handwaving and regurgitated old wive's tales (and not what started this thread, which was a bunch of just-so promotional handwaving by a flashlight seller.)
 

defloyd77

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No, what's actually been proven is that the folksy "explanations" and quasiscientific nonsense about yellow light penetrating fog better is a bunch of hoo-hah. This page and this one have what I have long considered to be dependable and correct information on the subject, not least because they have direct links to the full texts of relevant, rigorous studies by recognized expert scientists...not just a bunch of handwaving and regurgitated old wive's tales (and not what started this thread, which was a bunch of just-so promotional handwaving by a flashlight seller.)

I'm not sure why you're telling me "no" while posting articles that pretty much say the same thing I said?
 

-Virgil-

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You said if fog headlights are colored, they're yellow and that's to eliminate blue from the beam. Regardless, it's been proven it's just best to go with white light that's aimed and focused right. (for) fogcutting (...) the thing that's best for you is a good, quality source of white light.

I posted links to sturdy, science-based explanations of why yellow light can be better than white in fog/snow/rain.
 

Alaric Darconville

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*Blue: Blue light can cut through fog, which is widely used for fog headlights.
Blue light has absolutely has no place in a fog lamp and it is NOT widely used in fog lamps. Not even in Elbonia!

Also, between white and selective yellow light, selective yellow light is superior in the fog. Not because it "penetrates fog" (an old dad's tale that seems to never go away), but that the light from the inevitable backscatter is easier for the human optical system to process.
 
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