Do certain color led's put out more light?

Brasso

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Do certain color led\'s put out more light?

Skimming over some of the recent posts on here it sounds like colored led's have more "band for the buck" so to speak over the white led's. Does any of the colors hold an advantage over the others for visibility? I know the human eye can see more shades of green than any other color so I wonder if something like a green led Infinity would be better for seeing in the dark without destroying your night vision.
 

Sub_Umbra

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Re: Do certain color led\'s put out more light?

Green will probably be hardest on your night vision under most circumstances. Blu/green is used by the military on night ops because night vision gear has filters so that other team members may use it without messing up the night vision equipment use.

While red will preserve night vision, it gives off so much IR that it is like a beacon to anyone using NV gear. Actually, when you buy a 'red' LED flashlight it's usually right around 630 nm -- which is into the orange part of the spectrum so far that its closer to yellow than red. Even so, many find this 'super orange' very difficult to use since the human eye is so insensitive to it. A true red (with a frequency above 650 nm) is even harder to work with IMO.
color_sensitivity_o.jpg
 

IsaacHayes

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Re: Do certain color led\'s put out more light?

I had a 5W "true" green mag light I made once. It wasn't lime green, and it wasn't traffic green (keep in mind humans can tell differences between lots of "shades" of green). It didn't bother my eyes so much but it was bright! I now have a 3W Cyan that is around 495nm and the contrast is amazing! I can make out lots of things with this color at night. Even tell the difference of colors easily! I'd say that cyan is better than green at night even though it's supposed to be reversed....
 

Brasso

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Re: Do certain color led\'s put out more light?

So which color puts out the most light? If for instance you had an Infinity, which color would illuminate the best?
 

Mags

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Re: Do certain color led\'s put out more light?

Correct me if I am wrong, but I believe that green is only more "visible" to the eyes rather than brighter in life.
 

Sub_Umbra

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Re: Do certain color led\'s put out more light?

I've got quite a few lights with colored LEDs and it seems to me that my brightest are turquoise. (I've never owned a cyan, however).

Brasso,
I have a fistful of old CMG Infinities and the turq is much brighter than any of the four green ones I have in the same model. The only colored ARC AAA I have is also turq and it just blows away my white ARC AAA.

I read one theory that could explain why the turqs look so bright in the wild while the greens are always at the top of the sensitivity charts -- someone said that the turq light causes both the green and blue cones to fire, so it seems brighter than the green light, which would only fire the green cones. I dunno. It makes sense, but I dunno.

Maybe the cyan seems so bright for the same reason.
 

greenlight

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Re: Do certain color led\'s put out more light?

I don't think green is hard for night vision. I think blue would be worse, as it causes your pupils to contract more. Pulsing blue light is painful to look at because your iris has to work hard to contract each time. Just because it is easiest to see/brightest doesn't mean that green is hard on your night vision. Contrary, I find it rather pleasant.
 

Brasso

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Re: Do certain color led\'s put out more light?

The Infinity I have now is supposed to be white although it is noticeably blue in tint. I suppose it's probably about as bright as other colors?
 

Sub_Umbra

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Re: Do certain color led\'s put out more light?

Brasso,

There really are no white LEDs. What is called a white LED is actually a blue LED that has a phosphor coating that makes it give off a whitish light. Thats why the light from white 5mm Nichia LEDs is sort of violet in the center. This blue to white conversion is why true color LEDs like green can be as much as 70% brighter than white LEDs of the same class.

This conversion is the reason that I like green lights so much. You get 70% more light for the same size/battery combonation. I always use green unless I need color recognition for some task. For object recognition green is tops.
 

Sub_Umbra

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Re: Do certain color led\'s put out more light?

greenlight,

Here's a sensitivity chart broken down into photopic and scotopic response:
lumeff.gif

The green curve representing scotopic sensitivity is actually showing what frequencies of light your rods are sensitive to and how sensitive they are to various wavelengths. Green has the potential to whack your scotopic vision quicker than any other color because of the eye's greater sensitivity to that range. Note that the scotopic (dark adapted) curve pretty much peters out above 620 nm. (Right at what is commonly referred to as 'red'). That's why wavelengths above 620 nm are used to preserve night vision -- the rods don't fire in that range.

Actually, ANY common color may be used to preserve dark adapted vision if it is dimmed down enough. For example, if you take a green light which is infinately dimmable, like the Rigel Systems Mil-Skylite and sit in a dark room until you are dark adapted, you may then slowly turn up the Rigel (from off) just to the point where objects become recognizable by shape. If this is done carefully you won't see any green from the beam -- only greys. At this point you are seeing with your rods only since the intensity is not enough to fire the cones. Many say that this will have no effect on your night vision.

When this method is used with a white light it may represent the best of both worlds for preserving night vision and still having some color recognition. If you need to recognize a color (on a nautical chart, for example) you may slowly increase the intensity only enough to identify the color and then turn it right back down again. This will destroy a very small quantity of rhodopsin (visual purple) but such a small amount that it will be replenished very qickly.

When I looked into 'night adapted vision' last year I was amazed at what a controversial subject it is. I spent the better part of a couple of nights trying to get a handle on it. There is much information out there and many different approaches.

Here are some links for the interested. They also contain some secondary links which are very good:

Human Night Vision Preservation
Preserving Night Vision - Colors?
The Red Myth
joys of a DIM flashlight
 
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