IR photo/videography - filter for light source? Long-ish...

Hi folks...
An evil plot has come upon me, and I'm seeking some help in the "how
to?" and "how much?" departments.

First, let me assure you that this *IS NOT* aimed at the idea of
firearms use at night, although I'm aware that it could be put to such
an application if one desired to do so. The only shooting I plan on
doing with this rig (Assuming I can assemble it to begin with!) uses
videotape and/or photographic film as ammunition. Having said that...

I want to watch the deer. Without disturbing them or the neighbors. I
know we have a very large population of them around here, and that they
come and go like crazy at night (the tracks are impossible to miss,
they're even right up alongside buildings and vehicles, and one morning,
I went out to feed the horses, and there were deer prints from the wet
grass onto the concrete garage floor!) but come daylight, other than the
tracks and occasional droppings, they might as well not exist. Here's
where the "evil plot" part comes in...

I've got the cameras and related materials to tape/shoot in infrared. It
actually works decently using the IR from TV remotes as the "spotlight",
but due to the relatively low level, that's no good at anything beyond a
few feet.

That got me thinking about building an IR floodlight to go with the
cameras. My first thought, being mainly an electronics geek, was "A
whole bunch of IR LEDs, just like the ones in the TV remotes". Problem:
Power dissipation. Them puppies are gonna be making some heat. Problem
2: expensive.

OK, that idea MIGHT work, but a better one is in order. I've got one of
those "2 million candlepower" spotlights. Now there's a light source...
Except it's visible light, and I already know the deer are skittish
about headlights, flashlights, and similar. (I come upon them often when
coming home from work late at night - they usually make tracks for
"anywhere but here!" as quick as they can once the headlights hit 'em)

On the other hand, they're "tuned" for UV sensitivity - The other end of
the spectrum, as I probably don't need to specify - and everything I can
find says that they're either blind, or very close to it, to infrared.

So, if I take a filter that blocks visible light, slap it up in front of
my spotlight, and point it at a deer, the deer might notice a slight
warmth, but otherwise be unaware of the light. Meanwhile, my video
camera is showing me and/or recording realtime footage that's either the
whole point of that session, or tells me I've got the light pointed in
the right place, and at the same time aims the still camera. Meanwhile,
the still camera, mounted above the video camera so that they're both
pointing at the same place, is being lined up to snap the IR picture
that the video is seeing.

OK, OK, OK, I know... I'm rambling on. My apologies.

Now that I've figured this much out for myself, I need some expertise
from the photography buffs out there. I've found what I think SHOULD be
the filter I need. The problem is that "should be" and "it is" is a
distinction I don't have the knowledge to make, but you might.
One online source for it is http://www.adorama.com/KKWFG87.html
It's billed as being a "Kodak Wratten Gelatin Filter 75mm/3x3" Opaque
#87 Infrared". The description sounds promising, at least, as far as it
goes - "Visibly opaque filters absorb unwanted visible light in infrared
photography."

Based on the info I've supplied so far, would this item be likely to
accomplish the task I'm getting ready to put it to? If not, what would
be your suggestion as far as filters that I might use? I can't help but
notice it's rather pricey, at 55 dollars for a 3 inch square (No, I
don't have the measurements of my light handy, but I'll be checking on
that next) and I'd rather not be needing to replace it very often. It
sounds like it might be rather fragile, based on the fact that it's
called a "gelatin" filter. Will it survive for very long? And if it is
fragile, any suggestions for extending its working life?

Thanks for wading through this long-winded brain-pick!

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
I respond to Email as quick as humanly possible. If you Email me and get no
response, see http://www.sonic.net/~dakidd/main/contact.html Short
form: I'm trashing EVERYTHING that doesn't contain a password in the subject.

Try checking with some of the security equipment suppliers ... they often use IR for
surveillance, and have standard IR Illuminators available at relatively reasonable prices.

For example ... an 'exact phrase' search on

IR Illuminator

came up with over 8,000 hits like

http://www.axis.com/products/cam_irillum/

http://www.internetmarket.org/comput...t_vision.htm?A

http://www.angelfire.com/de/donnied/

http://www.nightvisionoptics.com/zoomiril.html








"RSD99" wrote in message
...
Try checking with some of the security equipment suppliers ... they often use IR for
surveillance, and have standard IR Illuminators available at relatively reasonable
prices.

"Don Bruder" wrote

OT: This post is OT, should be in a video forum, but since it
is also applies to IR photography...

FWIW: IR illuminators for VTRs are available cheap, from ebay even.

[I want to take videos of deer] First, let me assure you that
this *IS NOT* aimed at the idea of firearms use at night,

You don't have enough deer.

I want to watch the deer

OK, I won't ask why, "De Gustibus non est Disputantum" etc.

That got me thinking about building an IR floodlight to go with the
[video] cameras. My first thought, being mainly an electronics geek, was "A
whole bunch of IR LEDs, just like the ones in the TV remotes".

Sounds good.

Problem: Power dissipation. Them puppies are gonna be making some heat.

Less than a Christmas tree light. They will make 'some' heat I suppose:
10 LEDs at 80ma each, wired as five 2 LED strings (2 LEDs
1 resistor in series), running from a 12V power supply produce
5 x .08A x 12V = 4.8 watts.

Problem 2: expensive.

Around $2.50 for a pack of 10? Liteon LTE-5228A, Digikey #160-1062
About 7mW/sr @ 20mA, with a max rating of 100mA @ 25C.

OK, that idea MIGHT work

It will work:

An Ir LED is 50x (~ 6 stops) brighter than a standard red LED. An
IR LED, as above, will put out 4.78 cd @20mA. A standard red LED
puts out .09 cd. This isn't really a true comparison since Ir
LEDs are rated in mW/sr and visible ones in cd, a human-eye
response measurement, but it gives a touchy-feely idea of relative
brightness. At green light 1cd = 1/683 mW/sr. [cd = candela,
mW = milli-watts, sr = steradians].

You say it kinda works with the light from a TV remote. Remotes
put out very little average power: the signal is a series of short
pulses put out a low repetition rate.

but a better one is in order. I've got one of
those "2 million candlepower" spotlights. Now there's a light source...

Use 'em every time I land my LearJet. This is overkill.

So, if I take a filter that blocks visible light, slap it up in front of
my spotlight, and point it at a deer, [and turn the spotlight on]

The filter will melt. The spotlight is designed to produce visible light
(and heat, natch): An IR filter will turn all that light into heating
the filter.

Additionally, being a spotlight it will light up only a small bit
of the deer.

There are special bulbs that put out just IR. If you want to go the
incandescent route I would suggest one of those.

But, hey, do what you wish.

--
Nicholas O. Lindan, Cleveland, Ohio
Consulting Engineer: Electronics; Informatics; Photonics.
Remove spaces etc. to reply: n o lindan at net com dot com
psst.. want to buy an f-stop timer? nolindan.com/da/fstop/
..

In article ,
"Nicholas O. Lindan" wrote:

"Don Bruder" wrote

OT: This post is OT, should be in a video forum, but since it
is also applies to IR photography...

FWIW: IR illuminators for VTRs are available cheap, from ebay even.

Agreed. But not at any price that *I* consider reasonable. At least, not
so far. Dumping anywhere from $80-$200 into a "let's dink around with
the idea to see if it works" project just doesn't hit me as being all
that... Errr... pardon the pun... bright of an idea.

[I want to take videos of deer] First, let me assure you that
this *IS NOT* aimed at the idea of firearms use at night,

You don't have enough deer.

Trust, me, we've got PLENTY of deer - it's just that in daylight, or
using visible floods/spots, they get scarce in a hurry. Once "the lights
go out", you darn near need to beat them off with a stick.

I want to watch the deer

OK, I won't ask why, "De Gustibus non est Disputantum" etc.

chuckles Yeah, it's not the typical request, I guess

That got me thinking about building an IR floodlight to go with the
[video] cameras. My first thought, being mainly an electronics geek, was "A
whole bunch of IR LEDs, just like the ones in the TV remotes".

Sounds good.

Problem: Power dissipation. Them puppies are gonna be making some heat.

Less than a Christmas tree light. They will make 'some' heat I suppose:
10 LEDs at 80ma each, wired as five 2 LED strings (2 LEDs
1 resistor in series), running from a 12V power supply produce
5 x .08A x 12V = 4.8 watts.

Everything I've read says that these IR units have problems with heat
dissipation - Some of them bad enough that they apparently need to
heat-sink each individual LED to keep them from cooking themselves.
That's a bit more than "a christmas tree light", I'm thinking...

Yes, I have a grasp on ohm's law and power dissipation, but at the same
time, I've got a grasp of the concept "too hot, and it melts down".
Dunno what the cause of the meltdown is, but it appears to have been
common enough in the early stages that today, one of the seemingly "key"
selling points on the commercially available IR illuminators that I've
come across so far is how well they're heat-sinked. At least, that's
what the literature I've been encountering seems to indicate. Or am I
falling victim to advertising hype?

Problem 2: expensive.

Around $2.50 for a pack of 10? Liteon LTE-5228A, Digikey #160-1062
About 7mW/sr @ 20mA, with a max rating of 100mA @ 25C.

OK, that idea MIGHT work

It will work:

An Ir LED is 50x (~ 6 stops) brighter than a standard red LED. An
IR LED, as above, will put out 4.78 cd @20mA. A standard red LED
puts out .09 cd. This isn't really a true comparison since Ir
LEDs are rated in mW/sr and visible ones in cd, a human-eye
response measurement, but it gives a touchy-feely idea of relative
brightness. At green light 1cd = 1/683 mW/sr. [cd = candela,
mW = milli-watts, sr = steradians].

Congratulations... I think you just left me in the dirt. I've heard of
candelas - Isn't that the light from one candle hitting a 1 foot square
white plate from a distance of 1 foot? mW is obvious, but what on earth
is a "steradian"? Sounds like something to do with angles. Note to self:
Google "Steradian". ACK! Now I'm HOPELESSLY lost! It DOES have something
to do with angles, but how that applies to how much light is coming out
of an LED (IR or otherwise) is beyond my comprehension!

You say it kinda works with the light from a TV remote. Remotes
put out very little average power: the signal is a series of short
pulses put out a low repetition rate.

Right. As demonstrated by my initial experiments, a TV remote is little
more than a sequence of flashes. It seems to work *REASONABLY* well as
an illuminator out to about 10 feet, give or take, but drops off sharply
in effectiveness past that point.

but a better one is in order. I've got one of
those "2 million candlepower" spotlights. Now there's a light source...

Use 'em every time I land my LearJet. This is overkill.

Not for what I usually use it for. In fact, at times, it isn't enough.

So, if I take a filter that blocks visible light, slap it up in front of
my spotlight, and point it at a deer, [and turn the spotlight on]

The filter will melt. The spotlight is designed to produce visible light
(and heat, natch): An IR filter will turn all that light into heating
the filter.

That's what I was afraid of.

Additionally, being a spotlight it will light up only a small bit
of the deer.

Spotlight, floodlight... For *MY* purposes, they're pretty much the same
thing, even if, to a photo tech, stagehand, or whatever, they're two
completely different beasts - A fairly concentrated light source that'll
allow photo/video work in the absence of other light. Assuming I
filtered the one I've got, and the IR coming out of it works at least
reasonably close to the same way the visible light it puts out does, I'd
be IR-painting a circle about 50-60 feet across at somewhere in the
neighborhood of 150 feet out. For this camera/spotlight combination,
that means I've got a "shootable" area probably about 30 feet across
when using it in "visible" mode. More than adequate to get the whole
deer (unless we're growing them *A LOT* bigger than I think we are!) in
the shot easily.

There are special bulbs that put out just IR. If you want to go the
incandescent route I would suggest one of those.

Well, actually, I was wanting to go the LED route, but that doesn't
*SEEM* to be either practical or reasonably (by my standards) affordable
at this stage.

But, hey, do what you wish.

Thank you ever so much. Having permission to o something from someone
online is SUCH a reassuring thing...

Seriously, though, thanks for the input. Perhaps the heat problem with
the available LED-based illuminators isn't as bad as I've been led to
believe. I'd rather go with solid state (stands up better to day-to-day
portable use) than fiddle around with filters and incandescents.

--
Don Bruder - - New Email policy in effect as of Feb. 21, 2004.
I respond to Email as quick as humanly possible. If you Email me and get no
response, see http://www.sonic.net/~dakidd/main/contact.html Short
form: I'm trashing EVERYTHING that doesn't contain a password in the subject.