Don said:
OK, guys... you've all been having so much fun with LED flashlights, now
here's one for ya:
Show me some plans for a floodlight/spotlight (ideally, adjustable
between the two) *USING IR LEDs* that will light up a goodly section of
territory - Enough to make decent moonless-night video of deer with a
camera that has demonstrated itself to be QUITE nicely sensitive to the
IR wavelength used by all the remote controls I've got in the house.
It won't work. I have tried. The unfocused/unreflected LED's will only
illuminate out to about 15-20 feet, if you are using a gen-1 NV tube
viewer, and a CCD-camera is about equal to that at best. You can put one
IR LED into a flashlight-base and put it in a flashlight (with a
dropping resistor) and get a -fairly- good small beam out to 40-50 feet
or so, but the flashlight you use MUST have a sweep focus, that can
adjust from spotlight to flood. Because the "flood" setting doesn't
illuminate very far, but the "spot" setting is too bright to be of much
use up close. ....THere are companies that sell IR-LED heads that they
say are for this. I have not tried any of them, but from my own attempts
(with a 19-LED unreflected unit, as well as a couple single-LED
reflected attempts) in a Mag-light body I would say it doesn't work.
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The best way to make a IR light source for a gen-1 or CCD camera is also
the easiest way: use a regular flashlight, regular bulb and get a
deep-IR glass photographic filter. These filters will not allow any
visible light through at all, but they are expensive: the Hoya-RM90 is
one. A much cheaper way is to put a deep-red and deep-blue filter over a
regular flashlight. This is visible-red if you are looking right into
it, but the light it casts is not visible--yet shows brightly in gen-1
NV scopes. CCD cameras catch it well too, if they have no IR filter. As
to how well the animals can see this, I don't know. My experience was
that wildlife were far more concerned about noises than a red light, but
you may be after different animals.
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If you really want to see in the dark [WITHOUT using active lighting]
the -only- way is to get a gen-2 or gen-3 night-vision scope, one that
adapts onto your camera of course. Figure $1200+ US for a gen-2, $1800+
US for a gen-3. This will allow you to film in any lighting
circumstances outdoors, probably without any additional lighting at all.
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As a sidenote, I also have tried stacking two gen-1 scopes. By taking
the eyepiece off one, and holding that up right in front of the other.
It doesn't really accomplish much; the image is somewhat brighter but
far less clear--the "background noise" brightens more than the image.
You need to use an f-stop on the scopes to see anything at all--I used
pieces of kraft paper over both lenses, with small holes cut centered in
them about 10mm across--or else the rearmost image turns up too bright.
Two cascaded $100 gen-1's won't equal a single $1000 gen-2. Gen-1 NV
tubes use electron inverters internally, that drastically ruin/blur the
images they produce. A gen-2 or gen-3 NV scope image is far more clear
than a gen-1 is, and amplifies light higher and with less noise as well.
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