IR filters - just curious

[Tomcat!]

I have read many incan vs LED threads about the various pros and cons of the technologies, and the incan crowd's top two pros are always colour rendition and throw. Having started with incan and still keeping a 9P I know the merits of these two. The other pro that sometimes gets chucked into the argument is use of IR filters. I'm aware that incan puts out a lot of IR whereas LED does not, but I'm curious as to what people actually use IR for? Are you running around with night vision goggles for hunting, committing up-market burglaries, making 'Paris Hilton' videos, what?
I've only seen the SF IR filter and it seems horribly expensive so I'm guessing your uses aren't just 'messing about'?
Who would use IR filters and who would use IR bulbs?

I think there's a hole in my light education that needs plugging.

 

[CM]

Some of us with high tech gear like Gen III NV like to supplement our toys with IR. So for the most, I think we are just playing. However, there is probably a small crowd here that use active illumination for more "Serious" purposes.

 

[Size15's]

The military and to a lesser extent specialist law enforcement use IR light (often by filtering incandescent light) so that they can see using 'night vision' equipment.

Whilst it is inefficient to block out all but the IR light from a visible light source, and an alternative to that would be to run a dedicated IR illuminator that uses IR LED(s) source, there is sometimes the need to switch from IR to white light quickly and flipping away a BeamFilter is a practical method of achieving this.

 

[Tomcat!]

Some of us with high tech gear like Gen III NV like to supplement our toys with IR. So for the most, I think we are just playing. However, there is probably a small crowd here that use active illumination for more "Serious" purposes.

What do you use your NV gear for?

 

[Tomcat!]

The military and to a lesser extent specialist law enforcement use IR light (often by filtering incandescent light) so that they can see using 'night vision' equipment.

Whilst it is inefficient to block out all but the IR light from a visible light source, and an alternative to that would be to run a dedicated IR illuminator that uses IR LED(s) source, there is sometimes the need to switch from IR to white light quickly and flipping away a BeamFilter is a practical method of achieving this.

So one could supplement the built-in IR of a video camera (even a domestic one) with an external IR lamp? I guess specialist LED would be more practical and efficient?

What is the difference between what used to be (or still is) called 'image intensifying' and IR? Is it that one is passive and the other active?

 

[Size15's]

We have a night vision forum here on CPF
http://www.candlepowerforums.com/vb/forumdisplay.php?f=16
We'll move this thread there if the topic meanders more in that direction...

 

[Tomcat!]

We have a night vision forum here on CPF
http://www.candlepowerforums.com/vb/forumdisplay.php?f=16
We'll move this thread there if the topic meanders more in that direction...

I noticed the NV section about 2 minutes after posting. I'll do my technology reading over there. Sorry about that.

 

[angelofwar]

More on the topic of the actual filters/IR light...other than the obvious of using them to enhance your vision with NVG's, there also used for covert signalling (morse), SOS, and IFF applications. You may want to use an IR filter on your G2/6P/E2, etc. to signal for rescue in a combat/hostile enviroment, becasue white light signalling, other than the obvious of giving away your position, may also be mistaken for ground fire from the helicopter pilot. I, however, use mine on my G3, for use with my camcorder, which has built in "Night Shot". A few will show up on Ebay from time to time, a bit cheaper than the retail price also.

 

[Tomcat!]

I can see the benefits of covert signalling.
Does a filter let much visible light out? I can't imagine it blocks out the whole visible spectrum? I mean visible to the naked eye. Wouldn't that give your position away?

 

[Size15's]

Does a filter let much visible light out? I can't imagine it blocks out the whole visible spectrum? I mean visible to the naked eye. Wouldn't that give your position away?

That's a very good question.

As far as I can tell, it's a balancing act. Yes, you can block out all visible light but then you aren't letting much IR through either.
I believe "covert" IR beam filters can let through a dull red glow that can be seen when bore-sighted with the beam and at reasonably close range. These tend to be in the order of 850nm filters.

There are also IR filters at 900nm and 950nm but the useful range for these becomes significantly less.

 

[Tomcat!]

A bit like a polarizing grating? I realise that's a bit simplistic but that's how I visualise it.

The IR lights I've seen on buildings for security all give off a faint glow so I guess to be effective you have to expect some visible light. Mind you, if they were perfect, you wouldn't know just by looking!:thinking:

 

[Size15's]

The IR lights I've seen on buildings for security all give off a faint glow so I guess to be effective you have to expect some visible light. Mind you, if they were perfect, you wouldn't know just by looking!:thinking:

These more visible IR illuminators serve a number of purposes - firstly, they are usually slaved to a CCTV camera and so are not covert - they can use more efficient IR that has a more visible signature.
They also serve to remind people that they are switched on, and are being used to observe even though it is dark. Reassurance and deterrence.

 

[Tomcat!]

These more visible IR illuminators serve a number of purposes - firstly, they are usually slaved to a CCTV camera and so are not covert - they can use more efficient IR that has a more visible signature.
They also serve to remind people that they are switched on, and are being used to observe even though it is dark. Reassurance and deterrence.

Very true. They can also be enhanced by a simple sign saying 'Look up'. Not as silly as it sounds. A local council up North somewhere used the same trick with their CCTV just to get people to look at the camera. If the natives get up to a bit of naughtiness, the police will have a load of full face shots to view. Every so often they move the sign to a different camera. Granted it's not fool proof, but it is at least cheap.

 

[Lightraven]

I use Generation III night vision goggles (and also thermal imagers) quite often in some darker areas for law enforcement work.

Generation I and II greatly benefit from IR emitters. I don't know exactly what people use night vision for, besides law enforcement (private detectives?) and military--maybe animal watching at night? But using an IR light would help.

I have messed around with a Maxabeam with an IR filter. And I use the IR LED on the monocular itself occasionally.

 

[angelofwar]

On the subject of bad/good/better filters, the filters on my Camcorder and my NVG's are both visible (the red glow), when looked at directly from the front...however my SF IR Filter puts out NO visible light...my G3 will be turned on, and you can look directly into it and see nothing...even with the P91 bulb...only IR light can escape. Once again, SF spending just a little more to go that one extra step!!!

 

[Lightraven]

The Maxabeam IR filter I got with the light (there are a 2-3 different IR filters I believe) also shows a dim red glow. I never realized that until I looked straight at it, something I typically don't do with HID spotlights.

I recall reading in the Maxabeam manual that some IR filters would block all visible light, and some would block most. I guess your stealth versus illumination needs must dictate.

 

[CM]

What do you use your NV gear for?

Strictly for playing. When camping, you can observe wildlife without them knowing you're watching. I'm sure you can think of other things if you let your imagination go.

 

[leukos]

I have an IR filter for my M3 just because it is an accessory. One of these days I'll use it....

 

[Chrontius]

I intend to pick up a cheap NVG and a cheap third-party IR filter (and/or a Kaidomain IR LED) from Ebay (About $7) to use in a Land Warrior-esque paintball setup. It'll be great fun.

 

[baterija]

I can second angelofwar's comments about the surefire filter, there's no visible illumination with the filter in place. I've never used an IR filter on a flashlight for much more than a little playing around with it to see the difference. I have used filters over headlights for driving in the dark though, and they didn't have a visible signature either.

I've never used night vision devices for non "work related" purposes.