Infrared illuminators or flash lights that have little to no red glow? - Page 1

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[ARCHIVED THREAD] - Infrared illuminators or flash lights that have little to no red glow?

Posted: 9/17/2017 9:24:28 PM EDT

Which brands are good?

Thanks.

Posted: 9/17/2017 9:43:14 PM EDT

[#1]

Quoted:
Which brands are good?

Thanks.

View Quote

What's your budget, how far does it need to project, weapons mounted or hand held?

Posted: 9/17/2017 10:59:11 PM EDT

[#2]

If it's a I inch tube can't it be used for both applications?

Say 100-150 yards?

Posted: 9/18/2017 3:24:56 AM EDT

[#3]

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Quoted:
If it's a I inch tube can't it be used for both applications?

Say 100-150 yards?

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For a great IR light for the money a SolarForce drop in module and a body @ 23.00 direct from them. You can find the 950nm drop in modules for @ 8.00 which gives off less of a purple glow.
If you have the money and want a dual role flashlight that does both white and IR light either a SureFire M952V (350 lumen white light version not the 150 lumen), V1 (250 lumen white light version), or M622V

Posted: 9/18/2017 8:43:18 AM EDT

[#4]

Quote History

Quoted:

For a great IR light for the money a SolarForce drop in module and a body @ 23.00 direct from them. You can find the 950nm drop in modules for @ 8.00 which gives off less of a purple glow.
If you have the money and want a dual role flashlight that does both white and IR light either a SureFire M952V (350 lumen white light version not the 150 lumen), V1 (250 lumen white light version), or M622V

View Quote

+1

The Solarforce is cheap but works great. I was teaching my son how to drive with the PVS14 the other night and as we zoomed from fields to thick woods, I used it intermittently to help with the changing light conditions. For the low price, it can't be beat.

Posted: 9/18/2017 9:39:36 AM EDT

[#5]

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Quoted:

+1

The Solarforce is cheap but works great. I was teaching my son how to drive with the PVS14 the other night and as we zoomed from fields to thick woods, I used it intermittently to help with the changing light conditions. For the low price, it can't be beat.

View Quote

Is your light a 940nm? Does it have any red glow?

I recently spent some $$$ on a Surefire vampire scout. It's a great light, but the red glow in IR is excessive. To the naked eye it looks like a red LED headlamp without any forward projection.

Think this is due to the TIR lens. My new DIY project is to make an IR cut filter for it to eliminate the visible glow and, hopefully, tame the output to a degree that the light is useful up close ( it is too bright inside 50 yards).

Posted: 9/18/2017 9:44:03 AM EDT

[#6]

Thanks for the advice. I'll check that one out.

I ordered a couple of cheap $15-20 ones on eBay to mess around with. One is a 850 nm and the other is 940.

I have a couple of expensive $150.00 I bought years ago and they work great ( except for the one that fell apart on me) but have a visible glow out to like 40 yards. . To be honest I feel that that many of the expensive illuminators are cheap ones with a high price sticker.

Posted: 9/18/2017 10:40:43 AM EDT

[#7]

https://m.ebay.com/itm/OSRAM-Cree-Infrared-Radiation-Light-IR-850nm-Night-Vision-Zoom-Flashlight-Torch-/182660730390?hash=item2a876d8e16%3Ag%3AjPUAAOSwKoRZYvMR&_trkparms=pageci%253A2478efc2-9c7d-11e7-8e1a-74dbd180cf7d%257Cparentrq%253A9560b08a15e0a8665ecf35ffffdc2751%257Ciid%253A1

That's one of the ones I ordered. I got the last one from.a US seller for a dollar more.

Edited to add.

Here's the other one.

https://m.ebay.com/sch/i.html?_from=R40&_trksid=p2056116.m570.l1313.TR5.TRC0.A0.H0.X.TRS5&_nkw=Long+Range+IR+940nm+Night+Vision+OSRAM+Infrared+LED+

Posted: 9/18/2017 2:56:59 PM EDT

[#8]

Quote History

Quoted:

Is your light a 940nm? Does it have any red glow?

I recently spent some $$ on a Surefire vampire scout. It's a great light, but the red glow in IR is excessive. To the naked eye it looks like a red LED headlamp without any forward projection.

Think this is due to the TIR lens. My new DIY project is to make an IR cut filter for it to eliminate the visible glow and, hopefully, tame the output to a degree that the light is useful up close ( it is too bright inside 50 yards).

View Quote

No red glow that I can see, have to check it from some other angles.

Posted: 9/18/2017 6:19:46 PM EDT

[#9]

Quote History

Quoted:
Is your light a 940nm? Does it have any red glow?

I recently spent some $ on a Surefire vampire scout. It's a great light, but the red glow in IR is excessive. To the naked eye it looks like a red LED headlamp without any forward projection.

Think this is due to the TIR lens. My new DIY project is to make an IR cut filter for it to eliminate the visible glow and, hopefully, tame the output to a degree that the light is useful up close ( it is too bright inside 50 yards).

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Quoted:

Quoted:

+1

The Solarforce is cheap but works great. I was teaching my son how to drive with the PVS14 the other night and as we zoomed from fields to thick woods, I used it intermittently to help with the changing light conditions. For the low price, it can't be beat.

Is your light a 940nm? Does it have any red glow?

I recently spent some $ on a Surefire vampire scout. It's a great light, but the red glow in IR is excessive. To the naked eye it looks like a red LED headlamp without any forward projection.

Think this is due to the TIR lens. My new DIY project is to make an IR cut filter for it to eliminate the visible glow and, hopefully, tame the output to a degree that the light is useful up close ( it is too bright inside 50 yards).

Hope the ir filters you find work out.
I put 3 ir passing filters ( which they block visible light) and no reduction on ir glow. But they will block all the visible light from a 3 watt led flashlight . So this shows the filters will block 3watts worth of visible light but can't block the faint glow of visible light emitted from a ir light. Because it's ir light that's why it magically passes thru 3 ir passing filters.
If a filter blocked the visible glow that we can't see don't you think the military and ir light makers would install them.
I really hope you can find a way to eliminate the glow I couldn't. I did switch to a 940nm as it does put less visible glow.

Posted: 9/18/2017 8:23:03 PM EDT

[#10]

Will 940nm be picked up.by gen 1 or just 2 and 3?

Posted: 9/18/2017 8:29:59 PM EDT

[#11]

I wonder how one of those EBay T-20 lights compare to say, a High Tech Redneck T-20. Does HTR mod there's to be a better performer somehow? I've read in reviews that the EBay ones can be hit or miss as far as quality control. Just wondering about actual performance.

Posted: 9/18/2017 10:12:07 PM EDT

[#12]

Quote History

Quoted:
I wonder how one of those EBay T-20 lights compare to say, a High Tech Redneck T-20. Does HTR mod there's to be a better performer somehow? I've read in reviews that the EBay ones can be hit or miss as far as quality control. Just wondering about actual performance.

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His could be better or they could be the exact same thing (with his logo) that he's charging over 10x the amount for?

Obviously I have no first hand knowledge but from what I've learned from other industries, this does happen.
My " gut" ( with no proof) tells me that it's probably the same thing at much higher price.

There all produced very inexpensively from China.

For example..

Do you think Surefire lights cost anywhere near what they sell for for them to produce?
What's in a flashlight?
It's a tube, a tail cap, springs, bulb assembly etc.
When I was a kid, and I'm not that old, we made homemade flashlights.

Posted: 9/19/2017 12:21:17 AM EDT

[#13]

Quote History

Quoted:

For example..

Do you think Surefire lights cost anywhere near what they sell for for them to produce?
What's in a flashlight?
It's a tube, a tail cap, springs, bulb assembly etc.
When I was a kid, and I'm not that old, we made homemade flashlights.

View Quote

True, but the Surefire offers a beautiful white and IR beam from the same head. They also offer a AA version which allows me to have 100% AA batteries (helmet light, weapon light, NOD, weapon sight, IR laser, GPS, radio, and white flashlight).

Posted: 9/19/2017 12:31:08 AM EDT

[#14]

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Quoted:

Hope the ir filters you find work out.
I put 3 ir passing filters ( which they block visible light) and no reduction on ir glow. But they will block all the visible light from a 3 watt led flashlight . So this shows the filters will block 3watts worth of visible light but can't block the faint glow of visible light emitted from a ir light. Because it's ir light that's why it magically passes thru 3 ir passing filters.
If a filter blocked the visible glow that we can't see don't you think the military and ir light makers would install them.
I really hope you can find a way to eliminate the glow I couldn't. I did switch to a 940nm as it does put less visible glow.

View Quote

The filter I tried is from an old Surefire flip up for their incandescent lights. Obviously it won't work for converting white LED to IR, but it does work to eliminate the red glow in IR mode, thought it cuts output drastically. That isn't all bad as the IR output is way to much up close anyway. With the filter it works out to about 40-50 yards or so. Wish it was brighter but will work up close and can be removed for longer distance use.

Posted: 9/19/2017 2:23:05 AM EDT

[#15]

Quote History

Quoted:

His could be better or they could be the exact same thing (with his logo) that he's charging over 10x the amount for?

Obviously I have no first hand knowledge but from what I've learned from other industries, this does happen.
My " gut" ( with no proof) tells me that it's probably the same thing at much higher price.

There all produced very inexpensively from China.

For example..

Do you think Surefire lights cost anywhere near what they sell for for them to produce?
What's in a flashlight?
It's a tube, a tail cap, springs, bulb assembly etc.
When I was a kid, and I'm not that old, we made homemade flashlights.

View Quote

There is more to it than just making a 1" tube, end cap, head and slapping it all together. There is a lot of R&D/engineering that goes into manufacturing anything, tooling, planning, purchasing, marketing, assembling, testing, patenting, pay roll, shipping, etc. Also SureFire has a top notch return/repair policy. If something breaks they will either repair or replace it no questions asked. Are they worth it? If you have the duckets I'd say so. The way I'm able to afford them is to buy them used. If something goes wrong I send it back in which they usually replaced with a newer more powerful unit since they no longer make or have parts for the model I sent in.

Posted: 9/19/2017 3:33:23 AM EDT

[#16]

Quote History

Quoted:
Hope the ir filters you find work out.
I put 3 ir passing filters ( which they block visible light) and no reduction on ir glow. But they will block all the visible light from a 3 watt led flashlight . So this shows the filters will block 3watts worth of visible light but can't block the faint glow of visible light emitted from a ir light. Because it's ir light that's why it magically passes thru 3 ir passing filters.
If a filter blocked the visible glow that we can't see don't you think the military and ir light makers would install them.
I really hope you can find a way to eliminate the glow I couldn't. I did switch to a 940nm as it does put less visible glow.

View Quote

Perhaps stating the obvious here, but a 3W (assuming) white LED isn't producing much IR so it's an easy job for filters. On the other hand your IR LED is giving out lots of it and some escapes, I guess.

Not an expert on the matter, but what little I have read there are plenty of IR longpass filter materials with vastly different properties. Even a pricey filter could let something through as some have angle limitations on the light that they can reflect back and some leak on shorter wavelengths.

Posted: 9/19/2017 10:51:41 AM EDT

[#17]

The reason for putting the ir filter over a 3w white led flash light is to verify that all visible is blocked and you have a tested filter that only passes ir light. Then try the ir passing filter on a 850nm ir light and you will see it will not eliminate the glow. How can it cut all of the visible light from the bright flashlight but not the very weak glow from the ir light.
After all the purplish glow is at the opposite end of the light spectrum compared to ir light. From what I have concluded is the glow is ir light that we are not suppose to see.

Placing neutral density filters will dim the glow but will dim the ir output as well I have used them to reduce the glow but the range is cut to 30-40yds.

Posted: 9/19/2017 1:46:22 PM EDT

[#18]

850nm is in the range what people will see. Do you know the cut-on value of your filters? If it is even slightly lower than 850nm and maybe with a not so steep transition from reflective to transparent it's possible it leaks well into what the eyes can register.

I don't know the specifics of your white 3W LED, but that your filters stop all visible light from the white LED doesn't mean they block everything the eye can see.

This is just speculation, but I have heard a high qualitty steep cut-on NIR filter at 880nm should be pretty safe blocking visible signature.

Posted: 9/19/2017 9:25:27 PM EDT

[#19]

Side question. Will gen 1 even pick up light from a 940nm illuminator?

Posted: 9/19/2017 9:31:07 PM EDT

[#20]

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Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

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No.

Posted: 9/19/2017 9:45:37 PM EDT

[#21]

Quote History

Quoted:
850nm is in the range what people will see. Do you know the cut-on value of your filters? If it is even slightly lower than 850nm and maybe with a not so steep transition from reflective to transparent it's possible it leaks well into what the eyes can register.

I don't know the specifics of your white 3W LED, but that your filters stop all visible light from the white LED doesn't mean they block everything the eye can see.

This is just speculation, but I have heard a high qualitty steep cut-on NIR filter at 880nm should be pretty safe blocking visible signature.

View Quote

Ir passing above 720nm, 760,850,950

The ir950nm reduces the glow by 2/3 but cuts the output by the same . So same thing as a neutral density filter just blocking everything. With the other three stacked the glow is about the same .

Posted: 9/19/2017 10:15:00 PM EDT

[#22]

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Quoted:
No.

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Quoted:

Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

No.

I didn't think so.

Thanks for the reply.

Posted: 9/19/2017 10:18:22 PM EDT

[#23]

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I didn't think so.

Thanks for the reply.

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Quoted:

Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

No.

I didn't think so.

Thanks for the reply.

Welcome, Gen 2 (Generic) for that matter may see limited at 940 based on the tube.

Posted: 9/20/2017 11:08:33 AM EDT

[#24]

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Ir passing above 720nm, 760,850,950

The ir950nm reduces the glow by 2/3 but cuts the output by the same . So same thing as a neutral density filter just blocking everything. With the other three stacked the glow is about the same .

View Quote

Out of interest, do you see anything with your NOD if you place that 950nm longpass over the objective? When in front of the IR torch, does the angle from where you can see the glow change with the filter on? Some filters just plain leak and some have max incident angles from which on they no longer reflect but pass the light through. If the light bounced back once from the filter, then inside the torch reflector a few times, and comes toward the filter again it could be in any angle and have something to do with this. Or maybe your filter just leaks, 950nm with reasonable wattages should be invisible (both to the eye and almost completely to a regular Gen3)

Posted: 9/20/2017 11:10:58 AM EDT

[#25]

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Side question. Will gen 1 even pick up light from a 940nm illuminator?

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Gen0 will!

Posted: 9/20/2017 11:20:13 AM EDT

[#26]

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Quoted:
Gen0 will!

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Quoted:

Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

Gen0 will!

Lol...Bravo.

Posted: 9/20/2017 11:24:27 AM EDT

[#27]

Quote History

Quoted:
I wonder how one of those EBay T-20 lights compare to say, a High Tech Redneck T-20. Does HTR mod there's to be a better performer somehow? I've read in reviews that the EBay ones can be hit or miss as far as quality control. Just wondering about actual performance.

View Quote

I have an Amazon “Evolva” t20 and it lights shit up a tad better than my dbal d2. I used it for months but changed my setup so now it sits. Think I paid $30 or $40 for it.

Posted: 9/20/2017 1:54:28 PM EDT

[#28]

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Lol...Bravo.

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Quoted:

Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

Gen0 will!

Lol...Bravo.

Isn't there actually a generation 0?

Posted: 9/20/2017 5:55:21 PM EDT

[#29]

Quote History

Quoted:
850nm is in the range what people will see. Do you know the cut-on value of your filters? If it is even slightly lower than 850nm and maybe with a not so steep transition from reflective to transparent it's possible it leaks well into what the eyes can register.

I don't know the specifics of your white 3W LED, but that your filters stop all visible light from the white LED doesn't mean they block everything the eye can see.

This is just speculation, but I have heard a high qualitty steep cut-on NIR filter at 880nm should be pretty safe blocking visible signature.

View Quote

Here is a video of the magic purple glow and how it gets thru visible light blocking filters, actually 3 of them.
I messed around with pulse modulation and ways to eliminate the glow and very simple you can't because it's infrared.
Now getting a light with a deep embedded IR source like the torch pro will reduce any view from the sides, but you will still see the slight glow from source. Reducing the power helps but if you need the power no way around it.
IR 940nm passing thru 3 filters while small white led gets blocked 100%

The 3 filters block all visible light below 1st 720nm,2nd 760nm, 3rd 850nm

https://www.youtube.com/watch?v=gKIF1M1EtcA

Spectrograph of white led showing why IR filters won't work with white or colored leds.
NO IR light coming from a white led

Here is a video of no visible light emitted from a 940nm IR led
940nm 3watt IR light spectrograph output.

Posted: 9/20/2017 6:39:05 PM EDT

[#30]

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Quoted:
Isn't there actually a generation 0?

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Quoted:

Quoted:
Side question. Will gen 1 even pick up light from a 940nm illuminator?

Gen0 will!

Lol...Bravo.

Isn't there actually a generation 0?

I call Gen 0 a flashlight and a day scope.

Fooling aside, Gen 0 was the first NVD used in WWII in Okinawa. I almost have my hands on one...We shall see.

Posted: 9/21/2017 5:31:00 PM EDT

[#31]

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I call Gen 0 a flashlight and a day scope.

Fooling aside, Gen 0 was the first NVD used in WWII in Okinawa. I almost have my hands on one...We shall see.

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That would be fascinating to see! I hope you get your hands on it and give us a thorough write-up!

Posted: 9/23/2017 9:33:06 AM EDT

[#32]

I received one of the illuminators I ordered.

It is listed as 940 nm, has a very faint red glow that can only be seen up to about 5 yards (dead on) and...

It works with gen 1 night vision!

On it's mst focused beam, it can be picked up by gen 1 out to about 80 yards. I estimate the max range for gen 3 would be about 150 yards.

On the most focused setting the illumination pattern appears as a square. The led behind the lens is square; so this makes sense.

It's covert, works very well, seems well constructed and I got it for $18.00.

Posted: 9/24/2017 4:27:21 PM EDT

[#33]

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Quoted:
+1

The Solarforce is cheap but works great. I was teaching my son how to drive with the PVS14 the other night and as we zoomed from fields to thick woods, I used it intermittently to help with the changing light conditions. For the low price, it can't be beat.

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Quoted:

Quoted:

For a great IR light for the money a SolarForce drop in module and a body @ 23.00 direct from them. You can find the 950nm drop in modules for @ 8.00 which gives off less of a purple glow.
If you have the money and want a dual role flashlight that does both white and IR light either a SureFire M952V (350 lumen white light version not the 150 lumen), V1 (250 lumen white light version), or M622V

+1

The Solarforce is cheap but works great. I was teaching my son how to drive with the PVS14 the other night and as we zoomed from fields to thick woods, I used it intermittently to help with the changing light conditions. For the low price, it can't be beat.

How far does the solarforce illuminate? Would it be usable out to 100-150 yards to if steel targets and clearly see critters while hunting? I'm using gen 3 nv. It would be cool to drop one of their modules in my old surefire 660 and use it for a cheap IR illuminator until I can get something better.

Posted: 9/24/2017 8:31:23 PM EDT

[#34]

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Quoted:

Isn't there actually a generation 0?

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Yup. Its similar to what people incorrectly call gen1 these days. It uses a broadband s1 photocathode as compared to the s20 and s25 PC's used by gen1 and gen2 devices. In theory all three will pick up 940nm but the PC conversion efficiency will be terrible. So mainly it would depend on how bright it is.

Posted: 9/24/2017 8:32:26 PM EDT

[#35]

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I call Gen 0 a flashlight and a day scope.

Fooling aside, Gen 0 was the first NVD used in WWII in Okinawa. I almost have my hands on one...We shall see.

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Ive got a few... just not that one. PAS5 is interesting.

Posted: 9/24/2017 8:33:23 PM EDT

[#36]

Quote History

Quoted:
I received one of the illuminators I ordered.

It is listed as 940 nm, has a very faint red glow that can only be seen up to about 5 yards (dead on) and...

It works with gen 1 night vision!

On it's mst focused beam, it can be picked up by gen 1 out to about 80 yards. I estimate the max range for gen 3 would be about 150 yards.

On the most focused setting the illumination pattern appears as a square. The led behind the lens is square; so this makes sense.

It's covert, works very well, seems well constructed and I got it for $18.00.

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Link?

Posted: 9/25/2017 12:35:15 PM EDT

[#37]

Quote History

Quoted:
Link?

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Quoted:

Quoted:
I received one of the illuminators I ordered.

It is listed as 940 nm, has a very faint red glow that can only be seen up to about 5 yards (dead on) and...

It works with gen 1 night vision!

On it's mst focused beam, it can be picked up by gen 1 out to about 80 yards. I estimate the max range for gen 3 would be about 150 yards.

On the most focused setting the illumination pattern appears as a square. The led behind the lens is square; so this makes sense.

It's covert, works very well, seems well constructed and I got it for $18.00.

Link?

https://m.ebay.com/itm/Long-Range-IR-940nm-Night-Vision-OSRAM-Infrared-LED-Hunt-Flashlight-Light-Switch-/391722173872?var=&hash=item5b347605b0%3Am%3AmxhknDVEXe2vr3lWF2fq4RQ&_trkparms=pageci%253A4d45ab91-a20f-11e7-b852-74dbd1801221%257Cparentrq%253Ab9e32add15e0abc5793210d9ffddc11a%257Ciid%253A1

Posted: 9/26/2017 12:51:52 AM EDT

[#38]

I got the other one I ordered.

It's a short to medium range illuminator with a variable beam. ( Like the other one I bought)

It's an 850nm, works extremely well and seems to be very well built.

https://m.ebay.com/itm/292131031426?_mwBanner=1

However the red glow is very visible but you have to be directly lined up, so I'd say it's visible out to about 40 yards ( at any angle) and perhaps (within 40 yards) 1-2 degrees off dead center.(axis)

I'm very happy with both my purchases.

Posted: 9/26/2017 1:55:31 AM EDT

[#39]

op,

what is your use for the ir flashlight, and why do you want the emitter to not be visible?

what setup are you going to be using with it?

questions to taylor some information

Posted: 9/26/2017 10:54:16 AM EDT

[#40]

Quote History

Quoted:
op,

what is your use for the ir flashlight, and why do you want the emitter to not be visible?

what setup are you going to be using with it?

questions to taylor some information

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I don't have a particular set up but was thinking to add a monocular mounted behind a red dot or a scope.

Isn't the whole idea of night vision to see in the dark and (try) not to be detected? Otherwise one would just use a regular flashlight.

Btw. Nice avitar!

Posted: 9/26/2017 7:01:03 PM EDT

[#41]

So that one doesn't appear to have low, med, and high functions? I see several that look identical that do. They seem to cost a little more though. It does appear to have the OSRAM black LED which is supposed to be the most current version and noticably brighter than the previous version.

Quote History

Quoted:
I got the other one I ordered.

It's a short to medium range illuminator with a variable beam. ( Like the other one I bought)

It's an 850nm, works extremely well and seems to be very well built.

https://m.ebay.com/itm/292131031426?_mwBanner=1

However the red glow is very visible but you have to be directly lined up, so I'd say it's visible out to about 40 yards ( at any angle) and perhaps (within 40 yards) 1-2 degrees off dead center.(axis)

I'm very happy with both my purchases.

View Quote

Posted: 9/26/2017 7:50:21 PM EDT

[#42]

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Quoted:
So that one doesn't appear to have low, med, and high functions? I see several that look identical that do. They seem to cost a little more though. It does appear to have the OSRAM black LED which is supposed to be the most current version and noticably brighter than the previous version.

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It's puts out a lot of light that can be picked up with gen 1. I'm going to try it next with gen 2.

I'm happy with it the way it is and the price is great.

Posted: 9/26/2017 8:56:09 PM EDT

[#43]

well, if you are trying to be undetected by humans, I'm not going to ask what tier operator you want to pretend to be....

skypup posted in the past, that there are no rhodopsin receptors that detect and respond to wavelengths >720. it of course lead to some back and forth with others.
I tend to think that the eye is limited too.

the reason is as below (old quoted post)

Quoted:
you've both discussed it above, but graphically....

an led doesn't only emit one frequency of light, they are rated by the peak wavelength

wavelength of an osram 850nm led.

the various generation night vision devices have sensitivities like this

image orignally posted by dcs in this thread
http://www.ar15.com/archive/topic.html?b=6&f=18&t=294085

skypup notes that rhodopsin, the pigment that sees for you, is only sensitive up to 720nm in this thread
http://www.ar15.com/forums/t_6_18/414218__ARCHIVED_THREAD____Anyone_have_hogs_spook_when_turning_on_Torch.html&page=1

so what glow you see is light being emitted from the side wavelengths off of the peak.

and
shows how a cutoff filter, which only allows certain wavelengths of
light to get thru, could be used to decrease how visible the glow from
an led emitter is.
http://www.ar15.com/forums/t_6_18/402460_Hog_reaction_to_850nm_IR.html

from
the response graph, once you go above 850nm the sensitivity starts
falling off really fast. that means, you would need a lot more power at
940nm to achieve the same amount of visual illumination from a gen3 nvd,
compared to that at 850nm or lower.

so, if you really want to go
"covert", with little if any led glow, you'll want to put a bandpass
filter on a 850nm led, or get a 940nm at, maybe 4-10x the power, to get
the same 'visual brightness'.

View Quote

what the eye preceives is the spill from the smaller wavelengths, up to the 720nm. why is there such a visible glow? well, you have to remember that, with all the energy that is being put out at the peak, the more energy at the peak wavelength, the more energy at the spill wavelengths also.

how to fix the problem (at least dim it down)? you don't buy ir filters, you buy band pass filters that filter out the shorter wavelengths, as written up by skypup in the second link in the above quote.

if you really want to be covert, I suppose you could try to double up on the band pass filter, but at a greater attenuation of the passed wavelengths.

Posted: 9/26/2017 10:04:47 PM EDT

[#44]

With these filters, you will cut down on output; so it's 6 of one or half dozen of the other.

[ARCHIVED THREAD] - Infrared illuminators or flash lights that have little to no red glow?

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