What advantage(s) does a Blue LED offer?

As the title asks, what advantage(s) does a Blue LED offer? For example, Coast/LED-Lenser offers the option of either white or blue for some of their lights. I've tried to search as to what advantage a blue LED would offer, but I'm not having much luck. I could understand red or yellow for retaining night vision, but why blue? Is it for greater efficiency over other colors, or? If you have a good link that goes into detail about the advantage/purpose of blue, that'd be helpful. Most of the info I've read so far has pointed out the advantages of almost all colors EXCEPT blue.....

Blue is often advertised as useful for night-vision, though it actually isn't. Some things do flouresce under blue light, and blue light just plain looks cool. That's all I know of, but there is likely more.

It's supposedly useful for following blood trails from wounded game, or people if that's your thing.

I remember reading somewhere that blue light annoys the eyes. So if you're feeling sleepy, shine some blue L.E.D.s at yourself. Anecdotally, it's worked on me and my friends.

In other words it's about the most worthless of all colors, as I was beginning to suspect from the lack of benefits that I could find.

Greetings!

Blue lights have always given me a headache...

Best wishes,
Bawko

Atomic_Chicken said:

Greetings!

Blue lights have always given me a headache...

Best wishes,
Bawko

Click to expand...

Sweet! I'll make sure to add that to the list!

+1 to what A-Chick said. :green:
Color rendition is really bad as well.

greenLED said:

+1 to what A-Chick said. :green:
Color rendition is really bad as well.

Click to expand...

Err... color rendition is zero, and that's true of any single-color LED... ("hey, this red LED sucks, makes everything look red...")

Some things do flouresce under blue light, and blue light just plain looks cool. That's all I know of, but there is likely more.

Click to expand...

Yep, among them are the phosphors on white LEDs... if you shine a blue LED at any of your white LEDs you can see this effect. (Alternatively, you can actually turn on a white LED and see the effect...)

i have a blue led dive light.great for night dives.blues the last colour to absorbed so it gose much further

From another thread a couple days ago:

Sub_Umbra said:

...Blue is a great color as it is the easyest color to hide from an audience -- which is why it is used so widely backstage and in other technical spaces by techies in theatres. Blue can also often be had brighter than other LEDs in the same model lights.

Since blue light is not focused correctly in normal eyes it may actually sharpen the vision of (some) abnormal eyes -- there are a number at CPF who need glasses and can read more easily with blue light. I'm one of them.

Click to expand...

There are lots of people who routinely use blue lights because they work so well for some specific tasks.

A search of CPF posts will even reveal one CPF member who has used high powered lights with Royal Blue LEDs for hunting humans in the woods for years. The Royal Blue LEDs have enough energy in the NUV part of the spectrum to cause some clothing to floresce slightly for various reasons.

There are also some very high tech optical and dental grade epoxies that only set up in the presence of blue LEDs used for just that purpose.

There are very good reasons that so many various blue lights are produced and continue to sell. If there were no uses for them -- you wouldn't see them.

Thanks for the info Sub Umbra. Naturally I didn't actually think they were without uses, just under relatively 'general use' they seem a poor choice. Looking beyond white, at least red, yellow, orange/amber, green, etc. offer more advantage in general use night viewing. I was just having a hard time identifying its specific benefits since it isn't particularly good for general night viewing. You also mention the possibility of higher brightness vs. other LEDs in a given model - what specifically do you mean? Are Blue LEDs more efficient at a given brightness? Operate at a lower temp?

BTW, if there are other threads discussing the benefits/uses of Blue LEDs, I'd be interested in the links. I tried doing some searches beforehand, but the search engine takes a dump when I use terms that are too common.

"Blue light, in the middle of the visible light spectrum, focuses imperfectly on the retina while scattering in the eye. This phenomenon, called "blue blur," is further intensified by moisture and dust particles, and haze, fog, rain and snow on overcast days."
I suspect this is the reason why so-called blue blocker sunglasses are popular. They eliminate the blue blur.

"Blue light (380-480 nm) can cause damage to the Retina (the back of the eye)."
I remembered reading this a couple of years ago. Not sure how accurate it is or what level of exposure would cause damage, but it may be worth further research if you're considering buying a high powered blue led.

. You also mention the possibility of higher brightness vs. other LEDs in a given model - what specifically do you mean? Are Blue LEDs more efficient at a given brightness? Operate at a lower temp?

Click to expand...

Blue LEDs are the most efficient (watts out/watts in) LEDs by far, I suspect this because blue is what is used in white phosphor LEDs, and there's a big push to make the white more efficient. Even though the eye's sensitivity for blue is fairly low compared to a lot of the other colors, this is made up for by the fact that the LEDs are so power efficient compared to other single-color emitters. By shifting the spectrum slightly toward blue/green, it's possible to make very bright LEDs because they preserve the efficiency of the "blue" LEDs, but the eye is a lot more senstive to cyan.

Green LEDs are surpisingly inefficient (power out/power in -- producing fewer lumens than red or blue in many cases, even though the eye's sensitivity peaks sharply in the green. I suspect at this point it would actually be more efficient to use a blue LED plus a phosphor and green filter to produce green, than to actually use a green LED.

In terms of separate colors, I think that blue is the most useless for my use.

It's supposedly useful for following blood trails from wounded game, or people if that's your thing.

Click to expand...

green is more useful in the given example of tracking blood -- as grass/brush will reflect it, but red blood will not, so it will generate a stark contrast, even with low illumination. Green is also focused sharpest on the retina of any color, blue is the least focused.

As for the issue of looking for things that fluoresce, near-UV would be better, it can cause a wider variety of things to fluoresce (such as paper, cotton shirts, money) and the only visible light in that case will be caused by fluorescence -- blue light may caause things to fluoresce, but reflected blue will make it will harder to see.

In terms of night vision preservation, red is by far the best -- as it's possible to read by it, yet not disrupt night vision at all. Blue is the worst, as not only do the cones of the eye have poor sensitivity to it (can't see as well with it), that's where the rods have their peak sensitivity, so enough blue to be useful will immediately wipe out night vision.

I remember reading somewhere that blue light annoys the eyes. So if you're feeling sleepy, shine some blue L.E.D.s at yourself. Anecdotally, it's worked on me and my friends.

Click to expand...

The sun produces strong cool white output with a lot of blue in it. The moon on the other hand does not reflect blue very well, so presence of blue is the way your body can detect if it's daytime or nighttime. Artificially producing a lot of blue light is a way of "tricking" your body into thinking that it's daytime.

mmmflashlights said:

...You also mention the possibility of higher brightness vs. other LEDs in a given model - what specifically do you mean? Are Blue LEDs more efficient at a given brightness? Operate at a lower temp?

Click to expand...

LEDs have changed a lot in the last couple years and I'm not really up on the 'bleeding edge' of current LED development. What follows was definately true two years ago and is probably still true today. (someone will step up to correct me if I'm wrong
)

To my knowledge there really is no such thing as a white LED. There are only monochromatic LEDs. Unless things have radically changed just recently, what we refer to as white LEDs are actually blue LEDS whose dies have been doped with a phosphor that floresces and gives off a whitish light. Have you ever noticed the slightly lavender hotspot of a 'white' 5mm LED? It's a byproduct of the blue light behind it.

Anyway, back to the brightness. What we call a white LED is actually a blue LED being converted to a whitish output. Like many other covnversions, making white light from blue light is not 100% efficient. The blue LED will often lose ~40% of it's brightness in it's conversion to white, so it only makes sense that if we apply the same voltage and current to the blue LED before it's converted to white it will be brighter than the finished product (white).

If you have an eye trained in the use of blue light (there actually is such a thing as a trained eye) you may use this to advantage. Some of the lights offered by the original ARC and CMG make good examples. The ARC-AAA in blue might be 40% brighter than the same model in white so if you have the skills to use it you may pick the blue one and have a brighter light than the white one -- for the same runtime on the same cells. The same is true of some of the CMG lights. I have an old CMG Infinity in blue that is insanely bright -- much brighter than the exact same model in white.

The blue/green Infinity is a similar story. Both the blue and blue/green Infinities by CMG are nearly as bright as the white Infinity Ultras of the same era -- but with four times the runtime. Aside from other advantages of those colors just the runtime alone may make them the best choice for some applications.

Thanks for the info 2xTrinity, very informative. I've been thinking about getting an orange, amber, or yellow LED for a small 'night vision retaining' light.

Here's part of why I'm bringing up the discussion, though I'm certainly interested in learning all benefits and downsides to the different LED colors - https://coastcutlery.com/surveyCC.php . It's for people that have bought a Coast product, pay $3.50 and they'll send you a V1 Power Lenser with a BLUE LED. :thumbsdow It's a decent little keychain light that takes 4 AG13 cells, build quality is good, produces an ok spot and 1 narrow spill ring. But comes with this damn blue LED, I'd like to put a white or other colored LED in it, but I don't see an easy way to get to the LED. It's decently bright but unless you have a specific use for blue or are confident that you can modify it, $3.50 is probably about what the thing's worth.

2xTrinity said:

Green LEDs are surpisingly inefficient (power out/power in -- producing fewer lumens than red or blue in many cases, even though the eye's sensitivity peaks sharply in the green. I suspect at this point it would actually be more efficient to use a blue LED plus a phosphor and green filter to produce green, than to actually use a green LED.

green is more useful in the given example of tracking blood -- as grass/brush will reflect it, but red blood will not, so it will generate a stark contrast, even with low illumination.

As for the issue of looking for things that fluoresce, near-UV would be better, it can cause a wider variety of things to fluoresce (such as paper, cotton shirts, money) and the only visible light in that case will be caused by fluorescence -- blue light may caause things to fluoresce, but reflected blue will make it will harder to see.

The sun produces strong cool white output with a lot of blue in it. The moon on the other hand does not reflect blue very well, so presence of blue is the way your body can detect if it's daytime or nighttime. Artificially producing a lot of blue light is a way of "tricking" your body into thinking that it's daytime.

Click to expand...

I must disagree with some of these statements.

How much light does the moon reflect at any spectrum? Since it's only partially full for a few days during the month, those would be the only days where moonlight exposure would be present with any significance (assuming no clouds). Also, who is up all night to absorb lunar rays? I have to disagree with your statement and insist that the lack of blue in the light reflected by the moon has nothing to do with how the body detects day/night.

Blue: Causes some things to flouresce, like blood and scorpions (I personally don't hunt either, but have read this a lot; does anyone do this?). I would guess that a blue led has more throw/power than a UV led, and would be more useful if this was the intended purpose. Checking currency is an up-close task to would lend itself to UV testing. As far as comparing it to green LED for blood tracking, there's not a lot of blue foliage, so the only thing that will light up will be the blood. Looking for some little black dots under a green light would be next to impossible.

My green inova x1 is much brighter than my white one, and I think it runs longer, too. They have the same circuit, and I don't think that a colored filter over the white light would produce as much light as the green one.

I do agree with your statements about the red LED light.

mmmflashlights said:

...BTW, if there are other threads discussing the benefits/uses of Blue LEDs, I'd be interested in the links. I tried doing some searches beforehand, but the search engine takes a dump when I use terms that are too common.

Click to expand...

That's a tough one. Much of what I've read about blue I found on threads about uses of colored lights in general, which is tough to search for, too.

Here's one on blue lights:

http://candlepowerforums.com/vb/showthread.php?t=132539

Interesting ... so for tracking a person/animal that might be bleeding, there could be an argument for a light that combines green and UV LEDs?