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Ir wavelength..850 vs 940 vs led

SHW

SHW

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850 ..being the strongest with distance and clarity but quite visible to quarry
940 .. being not quite as good as 850 with distance and clarity but almost invisible to quarry

So what is the wavelength of led ? Obviously not quite as strong or clear as vcsel ….but I’m convinced that the led is almost invisible to quarry . ?

So I’m asking because I can shoot rats no problem from 5 yds onwards without them being spooked with the led …
But if I switch on my Tl3 850 vcsel at close distances they run because they can see it .. so I only use the vcsel from about 30 yds and further which they don’t seem to see
I’ve yet to try a 940 at close distances
 
Rats near me do seem to respond to the 850nm, I don't have anything 940 compare it with.

One thing that occurred to me is the method of dimming the light.
(Young) humans hearing, normally tops out at about 20kHz, rats 80kHz, so if the chopping method to dim the light gives off some nasty high audio frequencies above about 15kHz they would hear it, whereas we would not.

I was using a variable light last night and the NV scope and light cause visible flickering at some levels, so if the rats associate the whine with danger its not the light that is doing it.

I would assume if the light is just ON/OFF there is no chopping of drive, would be interesting test of light sensitive rats, go full power.
 
Lasers are monochrome light sources but LEDs are not. If you look up the full specs of the relevant LED you can find a chart showing the distribution of wavelengths. The LED label "840nm" or "950nm" refers to the wavelength of the peak emissions but the band of wavelengths produced by the 840nm LED extends down to the visible red spectrum, hence being able to see a red glow. Indeed, your perception of red is only how you see the combined effect of the wavelengths and intensities emitted; some of the emissions may be at shorter wavelengths (green for example) at much lower intensity.

I don't have access at the moment to my Cree LED spectral charts but can probably post something later if asked. In the meantime the first chart below shows the sort of wavelength distributions you might expect (except this is not real data and the bands shown are narrower than you might get from your torch).

1721563827758.png
 
I think the simple answer is that a vcsel emits far more IR than an LED of the same wavelength
850nm IR is at the outer edges of what the human eye can detect, so it takes a much more intense source at that wavelength for our eyes to produce a big enough response for our brain to "see" the dull red glow of the IR
Same thing for rats - an 850nm LED may not be intense enough to spook them while a much more intense vcsel at the same wavelength may well be enough to spook them.
Moving the light around so that at one moment they are in (for them) low light and then suddenly in much brighter light can easily make them sit up and take notice.

Cheers

Bruce
 
So if choosing vcsel, and shooting a whole array of quarry. But only out to 200m max, but mostly inside 100m which would you recommend 850 vs 940?

I assume within the limited ranges of above, 940nm??
 
Greyghost said:
So if choosing vcsel, and shooting a whole array of quarry. But only out to 200m max, but mostly inside 100m which would you recommend 850 vs 940?

I assume within the limited ranges of above, 940nm??
Click to expand...
If that's your ranges I would go for the 940nm.


Cheers

Billy
 
Yes, at 200m the 940nm IR illuminates rabbit size more than well enough to shoot.
You need to be at over 300 yards for the 940nm to produce a noticeably dimmer image than the 850nm

Cheers

Bruce
 
Here are the Cree LED spectra I mentioned earlier... no 850 & 950nm on these charts.
As you can see the breadth of the curves is not the same for all types so you'd need to look online for the specific outputs for each LED if you want to know the lower wavelength cut-off .


CREE XP-E2 LED.webp
 
@BallisticBill I posted some of these curves recently in a thread about visibility of ir torches and made the point that the spread of wavelengths emitted by a genuine Cree led is almost certainly much less than that of many of the knock off and sub standard emitters used in cheap Chinese torches.
 
Blackwood outdoors delivering my 940 IR tomorrow for my V2 Zulus 312R , have only ever used 840Ir before and even my Pard 008P was spooking rats and rabbits like the Zulus even on the low setting, so from next week and hopefully for ever it’s going to be 940 for me, will post the honest results which I’m sure are going to amaze me now in the 940 club
 
Am I right in thinking that a vcsel 940 is slightly more powerful and un’covert than a led 940 …
and same for 850 ..
Reason I ask is when ratting a usual haunt of mine I use an 850 led which doesn’t spook them at all ..
, but on one occasion I thought il try a vcsel 850 (only a small one ) and they scarpered ….. so I reverted back to the led and all went back to normal ……
Or am I just imagining things 😊
I did notice also on the longer ranges the 🐀 didn’t run using either ir
 
My 940 torch has meant that on a moonless night I've been able to stand very still in the open and have rabbit hop into airgun range unaware of their impending doom. Never able to do that with the Pards 850nm.
 
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