Red Filter vs Red LED for night vision?

I'm curious if someone could contrast the advantages and disadvantages of a red filter ( like the SF F05 ) vs direct use of a red led(s) in terms of perserving night vision? I'm interested in the technology and physiology, not costs or practicality.

For example, if a red filtered incandecent of a given output is the same as the output of a red LED in terms of preserving night vision, that's what I'm trying to find out.

I would assume there are some differences between the range of wavelengths output by both, but don't any details or if they matter.

I'd also like to know if one or the other is more "stealthy".

Thanks,

-john

I have a red LED light and a red filtered light. All I can say is that the LED light is much more powerful than the filtered version.

Jeff

Red filters waste 95% of the light. LED's are pure red, no waste. My toy NightCutter RED puts out more than A filtered SureFire.

NikolaTesla said:

Red filters waste 95% of the light. LED's are pure red, no waste. My toy NightCutter RED puts out more than A filtered SureFire.

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Is that different if it is filterning a white LED vs an incadecent?

Thanks,

-john

Hi John,

I read you question, and immediately grabbed my handy-dandy rip-off-o-matic pocket spectroscope to check this out (actually the scope is pretty cool, just not real quantitative).

I have a SureFire red filter (the push-on kind, similar in construction to the F04 Beamshaper) that I used on my McLuxIII-PD, a stock MiniMag with a red filter from Mag, a red SureFire A2, a red CMG Infinity, and an Aleph 3 with a red-orange LuxIII.

Both filters gave pretty much the same spectrum. It peaks in the red, tails off into infrared, and stops abruptly in orange. The Mag filter is actually more red -- the SF filter goes farther into the orange.

The Surefire A2's red LEDs are the most red of the LED sources, but the spectrum does very faintly taper off to the first parts of green. The Infinity has a definite green component to its spectrum, and the Aleph's R/O has the barest hint of blue on that end of its spectrum.

What that means for physiology, I can't tell you. But here is a link to the "USAF School of Aerospace Medicine FLIGHT SURGEON'S GUIDE." Check Chapter 8: OPHTHALMOLOGY AND SPECIAL PROBLEMS OF THE EYE, especially the section on night vision.

http://wwwsam.brooks.af.mil/af/files/fsguide/HTML/00_Index.html

Hope this helps.

Scott

PS: You also asked if one was more stealthy.

I think so. I think the redder lights (to include both filters and the A2) are much more difficult to see from a distance. There is something strange about red where, below a certain intensity, your eyes just don't detect it well. You can verify this by taking two lights of approximately the same brightness -- one red -- and shining them on the ground outside. Gradually point them up and into the distance. The red light will fade out much faster than the other.

The best light I have for preserving night vision AND remaining functional is my SureFire A2 in yellow-green. Its LED spectrum covers most colors in enough intensity to make them out. You can read the vast majority of features on a road map with it, where you cannot with a red light. However, red is still best (in my opinion) for astronomy and other apps where maximum night vision is required.

You have to think of it this way: A LED puts out a "pure" color (yeah, not really, but close enough) and no energy goes to waste. An incandescent puts out all colors and then you filter it so only red goes out. You waste all the energy produced in creating all the other colors.

Energy-wise, a LED will be more efficient in producing the light costing you less battery power. In addition, a filter on a higher powered incandescent will result in heat buildup since it is absorbing all the energy. Whether that's stealthy depends on whether someone is using thermal detection on you.

If I am looking for a light with the brightest red and don't want to spend $200 on the Surefire A2, what would be brighter. A white light incandescent flashlight with a red filter or a white light LED flashlight with the same filter?

Incan with a (quality) red filter. Grab an E2e on the Marketplace, and try an MN03 or MN02 bulb, with an F05 filter. Red filters only allow red light to pass (which LED's don't emit alot of), so red filters block MOST of the useable light an LED emits. An LED with a red emitter is also another good option. I know Streamlight used to make the Stylus available in red.

Hope this helps, and welcome to CPF!

Thanks for the advice. I wouldn't feel comfortable buying something from someone on a forum because I have never done it before and don't use paypal. Those lights are also expensive. I was looking for a solution for between $60-$100. I need a decent run time and common batteries so if I run out I can easily acquire more AA or AAA. Was looking at a fenix LD20 or LD40 with a red filter. Can the LD40 take a filter?
Any incans that take common batteries, adjustable brightness, decent runtime (5+hrs) and can put out good red light with filter for under $100?

My pentagon Molle Light has a red filter that unscrews from the tailcap and screws onto the front of the bezel.

http://milspecmonkey.com/equipment-page/illumination/101-pentagon-molle-light

But the red is SUPER low. I find it only good for close up work in the dark. Not for general illumination. Compared to my Kroma, Milspec, and L1-RD, I would use the L1-RD for punchy red LED. However my kroma, milspec and SF helmet light produce more than enough red light to navigate in the dark.

Might want to try a Streamlight Night Com LED Flashlight 51056 $41.95 @ Bright Guy

http://www.brightguy.com/products/Streamlight_Night_Com_LED_Flashlight_51056.php

The Streamlight Night Com C4 LED flashlight has a unique mode-select switch that allows you to choose from 3 lighting options - bright white C4 LED, 2 Nichia ultra-bright red LEDs or a single night vision protection LED (meets or exceeds the requirements of MIL-1472D for true night vision preservation). Safety mode is also available. When in safety mode, the flashlight cannot be turned on.

Rotate the mode select switch to choose the safe position or any of 3 lighting positions:
1. Lo power indicator type LED (for maximum night vision preservation); <0.05 lumens
2. Two Ultra-Bright RED LEDs; 2.5 lumens with up to 28 hours of run time
3. Center C4 bright white LED; 105 lumens with up to 3.5 hour run time

My .02 FWIW YMMV

MaxPowers5 said:

Thanks for the advice. I wouldn't feel comfortable buying something from someone on a forum because I have never done it before and don't use paypal. Those lights are also expensive. I was looking for a solution for between $60-$100. I need a decent run time and common batteries so if I run out I can easily acquire more AA or AAA. Was looking at a fenix LD20 or LD40 with a red filter. Can the LD40 take a filter?
Any incans that take common batteries, adjustable brightness, decent runtime (5+hrs) and can put out good red light with filter for under $100?

Click to expand...

As RWT1405 mentioned, a "combo light" with red emitters would be your best bet. Other than the stream-light nightcom, a few others are the Sidewinder, and the Energizer Tactical. No battery powered incan will give you 5 hours of useful runtime. SF's MN02 tops it out at 25 lumens for 2.5 hours, and just starts tapering off at the end. A Mag-lite on alkalines begins dimming as soon as you fire it up, and the light out-put is about useless after the first 15-30 minutes, depending on model. Look at these other models mentioned, and hope this helps!

if you want efficiency, go for a red LED.
a white led or incandescent bulb with a filter will be (much) less efficient.


I don't know about the night vision preservation or stealthyness ect but I'm sure there is a difference, because of the different spectra.


red LEDs emit a very simple spectrum, with a very narrow peak, while white LEDs emit a spectrum with two peaks, a narrow blue one and a broad yellow one and incandescent bulbs emit a very broad spectrum without any peaks etc.



you can see incandescent vs. white led spectra here:
http://ledmuseum.candlepower.us/led/a2.htm

red led here:
http://ledmuseum.candlepower.us/seventh/k2.htm

and, red filtered white led as well as red filtered incandescent here:
http://www.ledmuseum.candlepower.us/led/spectra0.htm


I think the best way to find out the advantages or disadvantages it to try it.

holy thread revival!!!!!!!! but anywho to the revivalist, here: http://www.batteryjunction.com/olight-m20-crimson.html $89.95

That M20 Crimson caught my eye a while back when I saw it announced... The only descriptions I can find list it as 105 lumens only.
Sure its 105 lumens of pure red light so it wont blow your night vision as badly as white, but its still really bright right?
That M20 crimson may just make it as a night hunting light... I have my 85Tr for close work, and a red thrower would be sweet...

Red is percieved as much less bright as say, green by your eyes.

srfreddy said:

Red is percieved as much less bright as say, green by your eyes.

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true, the same amount of energy in form of red light will be perceived muss less bright than green, but lumens are corrected in a way that lets us perceive 1 red lumen with the same brightness as 1 green lumen or 1 lumen of any other color with normal vision, that is not night adapted vision.

Okay thanks for the info.
So I guess I will drop my battery life requirement.
So what flashlight do you think will be the brightest with a red filter on it? Needs to be AA or AAA and under $100. I would also like a high/low function

MaxPowers5 said:

Okay thanks for the info.
So I guess I will drop my battery life requirement.
So what flashlight do you think will be the brightest with a red filter on it? Needs to be AA or AAA and under $100. I would also like a high/low function

Click to expand...

Steamlight sidewinder or energizer tactical. Both take 2ea. AA's (Lithium or Alkies). The SL Sidewinder is the better, because is has more settings.

ASheep said:

That M20 Crimson caught my eye a while back when I saw it announced... The only descriptions I can find list it as 105 lumens only.
Sure its 105 lumens of pure red light so it wont blow your night vision as badly as white, but its still really bright right?
That M20 crimson may just make it as a night hunting light... I have my 85Tr for close work, and a red thrower would be sweet...

Click to expand...

I have a M20S with a red filter, and the filter throws a ring of white light to the sides. If I wanted to be stealthy, I certainly would NOT use this light. The M20 Crimson is a much better solution since no white light can leak out of a red light.