IR Illumination

Flashlights, IR illuminators. Projects, reviews and queries. DIY 'stickies' here too.
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big black dog
Posts: 11
Joined: 01 Sep 2016, 10:56
Location: uk

IR Illumination

Post by big black dog » 11 Apr 2018, 10:12

Good Morning.
I have quite recently invested in NV and thermal for foxing. I use a Pulsar XD 38 S Thermal spotter and have a Pulsar Phantom NV scope. This outfit has revolutionised my foxing !......However, I am aware that some foxes do appear to pick-up on the IR illumination (whether using the 'on-board' IR that the Phanton comes with, or the Laserleuchs 5000 add-on that I occasionally use), have others noticed this too ? If so, is there a 'different' wavelength/ IR unit which may be used that foxes are not so attuned to ?
Any guidance, advice on this would be appreciated, thanks.

'Big Black Dog'.

blueroll
Posts: 668
Joined: 28 Nov 2014, 20:34
Location: Newton Abbot, Devon.

Re: IR Illumination

Post by blueroll » 11 Apr 2018, 12:00

Agreed that they can spot the IR.
I have found that the 940nm does not give enough illumination so I try to wait (not always possible) until the fox is facing away or distracted before I switch on and that gives you just enough time to nail him before he legs it. The only alternative is a thermal sight.

phoenix
BRUCE ALMIGHTY
Posts: 4687
Joined: 09 May 2012, 14:40
Location: Aberdeen

Re: IR Illumination

Post by phoenix » 11 Apr 2018, 13:29

Most tubed NV kit doesn't pick up IR wavelengths beyond 850nm, so going to 940nm to make it less visible to the foxes may well also mean that your scope can't see it either.

Cheers

Bruce
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

big black dog
Posts: 11
Joined: 01 Sep 2016, 10:56
Location: uk

Re: IR Illumination

Post by big black dog » 11 Apr 2018, 18:55

Thank-you 'blueroll' and 'phoenix' for your replies. Would you be kind enough to explain what you mean by the specific 'nm' values you quote in relation to my particular set-up. Apologies for my 'ignorance' re these technicalities.....bit of a 'philistine' as regards 'techno' .

ATB,
'Big Black Dog'.

blueroll
Posts: 668
Joined: 28 Nov 2014, 20:34
Location: Newton Abbot, Devon.

Re: IR Illumination

Post by blueroll » 11 Apr 2018, 20:08

big black dog wrote:Thank-you 'blueroll' and 'phoenix' for your replies. Would you be kind enough to explain what you mean by the specific 'nm' values you quote in relation to my particular set-up. Apologies for my 'ignorance' re these technicalities.....bit of a 'philistine' as regards 'techno' .

ATB,
'Big Black Dog'.
I know from experience what it means as to how well our NV performs, but for the techi, over to you Bruce.

phoenix
BRUCE ALMIGHTY
Posts: 4687
Joined: 09 May 2012, 14:40
Location: Aberdeen

Re: IR Illumination

Post by phoenix » 12 Apr 2018, 00:57

nm is short for nano metres. There are 1 million nanometres in a millimetre - so it's quite a small distance!
It's the unit that we use to describe the wavelength of light (and radio waves, microwaves, x rays etc, etc)
The human eye can detect light with a range of wavelengths from approximately 400nm up to around 760nm. From 760nm upwards is considered infra red (IR)
Tubed NV kit amplifies visible light and many tubes are not very responsive to light beyond about 820nm
Digital NV kit is entirely based on the fact that digital cameras can detect infra red light up to more than 1100nm.
However their sensitivity decreases as the wavelength gets longer.
The camera in a digital NV device will only be about 30% as sensitive to 940nm IR as it is to 850nm IR
Foxes (and humans) can "see" 820 and 850nm IR because the light is so intense and because the LED doesn't emit all it's light at exactly those wavelengths, a little visible light is also produced.
940nm is much less visible to humans and foxes (this is the wavelength used in many trailcams), but the range at which foxes can be seen with it is significantly reduced.
Foxes do "see" IR but, certainly in my area, it doesn't spook them. If, where you shoot the foxes are lamp shy, and IR shy, then a thermal scope is the only option.

Cheers

Bruce
LAND ROVER - THE WORLD'S WORST 4X4 BY FAR

warbucks
Posts: 816
Joined: 16 Sep 2013, 15:14
Location: Dewsbury

Re: IR Illumination

Post by warbucks » 12 Apr 2018, 11:41

As the lads have said 940 dosn't give enough range for foxing, i did try it once ----no good. (i use a Drone Pro with T66 850nm I/R torch)

Ive shot a little over 850 foxes in the last 4 years, IMO the foxes dont see the beam (turning I/R on when their not looking in its direction) but they do see the glow from the torch, depending on weather they have been shot at before will depend on if they spook, some time's they will sit and watch which then can make for an easy shot.

There are other things that we can do wrong in combination with the fox seeing the I/R glow, stopping in a vehicle then using I/R, using I/R then working the rifle bolt ect.

I have had foxes spook on me, my worst one was a fox that i had shot at and missed twice :thumbdown: every time this fox then came into the field it looked for the I/R glow then was off, this happened around 4 times, what i did was to come at it from a different direction and this worked i got it, even if you haven't shot at a fox and missed it but its seen your position with the I/R, its a good idea to move position the next time you go after it.

I always say that if a fox stays on my permission choose how wise they are i will eventually get it, they will eventually slip up.

Dave (warbucks)

big black dog
Posts: 11
Joined: 01 Sep 2016, 10:56
Location: uk

Re: IR Illumination

Post by big black dog » 12 Apr 2018, 19:48

Thank-you all for taking the time to reply with such helpful information.
I understand now I am not unique in experiencing this problem. I shall follow all of your suggestions and vary my routines as normal. If it were 'easy' everyone would be doing it !
Once again thanks all.

ATB,

'Big Black Dog'.

Lambda
Posts: 21
Joined: 31 Oct 2017, 17:41
Location: Den Haag, NL

Re: IR Illumination

Post by Lambda » 13 Apr 2018, 07:33

Hello :)

Here a little reference (one among others to be investigated, I guess) disclosing some informations concerning spectrum range accessible for game:

http://www.hunter.ru/hunting/articles/h ... _and_smell

The second graph is quite interesting and synthetic.

Just for feeding this interesting thread.

See you.

Lambda

Lambda
Posts: 21
Joined: 31 Oct 2017, 17:41
Location: Den Haag, NL

Re: IR Illumination

Post by Lambda » 13 Apr 2018, 12:49

Hi again...

Just some general ideas...

Sensor of digital nv as commonly used here gives access to a range of detectable wavelengths up to 1000-1100 nm. Quantum efficiency is nevertheless becoming weak at these end of the range. But still existing...

Here example with the watec 902 ultimate (sensor Sony ICX429ALL)


https://www.researchgate.net/figure/Qua ... 6_51910931

Around 5% QE at 1000 nm... weak but present.


There would be a bigger chance that these range of wavelengths (1000-1100 nm) would be less visible for foxes/games...

Therefore, using a IR powerful source emitting around this 1000-1100 nm range would be an alternative, while using a large objective lens as fast as possible (f1.0 or less, for instance) would still allow to feed the sensor of the ne device with enough light.

Briefly, making working nv sensor to its edge of spectral capability for giving less probability to be detected by games, and compensating lack of nv sensitivity, and range detection, by using better light collector and more powerful IR source....

Not a perfect solution, but reasonable compromise, budget-wise also...

Regards.
Lambda

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