Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a £10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.

--
Cheers
Dave.

On 28/10/2015 18:13, Dave Liquorice wrote:
Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

Might be worth trying a bit of exposed slide film... looks black the
visible wavelengths, but lets some IR through.

(I use it placed over the built in flash on the camera when I don't want
any direct flash illumination, but need to optically trigger a slave flash)



--
Cheers,

John.

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On Wed, 28 Oct 2015 19:58:21 +0000, John Rumm wrote:

Might be worth trying a bit of exposed slide film... looks black the
visible wavelengths, but lets some IR through.

Exposed and developed or just exposed? What ever I don't have any to
hand. Would the dark bit you sometimes get at the begining of a set
of negs work?

--
Cheers
Dave.

On 29/10/2015 01:54, Dave Liquorice wrote:
On Wed, 28 Oct 2015 19:58:21 +0000, John Rumm wrote:

Might be worth trying a bit of exposed slide film... looks black the
visible wavelengths, but lets some IR through.

Exposed and developed or just exposed?

Exposed and developed...

What ever I don't have any to
hand. Would the dark bit you sometimes get at the begining of a set
of negs work?

An unexposed and developed section of negative might - although that is
not as "black" as an exposed and developed section of colour
transparency film. If you have a box of slides produced commercially,
you often get one or two black slides from the ends of the roll.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
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| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/10/2015 03:34, John Rumm wrote:
On 29/10/2015 01:54, Dave Liquorice wrote:
On Wed, 28 Oct 2015 19:58:21 +0000, John Rumm wrote:

Might be worth trying a bit of exposed slide film... looks black the
visible wavelengths, but lets some IR through.

Exposed and developed or just exposed?

Exposed and developed...

What ever I don't have any to
hand. Would the dark bit you sometimes get at the begining of a set
of negs work?

An unexposed and developed section of negative might - although that is
not as "black" as an exposed and developed section of colour
transparency film. If you have a box of slides produced commercially,
you often get one or two black slides from the ends of the roll.

fx brain fart

In fact, swap those around, ;-)

Slide film will be black when totally unexposed and developed, and
negative black when fully exposed and developed.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 29/10/2015 01:54, Dave Liquorice wrote:
On Wed, 28 Oct 2015 19:58:21 +0000, John Rumm wrote:

Might be worth trying a bit of exposed slide film... looks black the
visible wavelengths, but lets some IR through.

Exposed and developed or just exposed? What ever I don't have any to
hand. Would the dark bit you sometimes get at the begining of a set
of negs work?

No you really want unexposed slide film developed end tails. Or modern
dye based negative film exposed to light and then developed.

I suspect the latter is not as dense.

--
Regards,
Martin Brown

On Wed, 28 Oct 2015 18:13:09 +0000 (GMT), "Dave Liquorice"
wrote:

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience with the cheaper end filters?

Kodak Wratten used to do gel filters to go on floodlights to convert
them to IR, a 500W halogen could barely be seen behind one. The
optical quality was very high and I used one filter and a pair of
scissors to make a number of camera filters. No idea what the
frequency band they passed was but they worked with IR film. I've
also used LEE Poly (polyester) filters in a Cokin mount (and black
bodge tape to keep the light out) . Apart from the fact they are
quite delicate (expensive sweet wrapper) they were fine. A friend put
them between two UV filters to create a more robust device, that
worked on most lenses but double banking the filters did produce some
masking at wide angles.

On Wed, 28 Oct 2015 22:25:04 +0000, Peter Parry wrote:

Kodak Wratten used to do gel filters

Still do but have you seen the price? £130+ for a 3" square bit! The
IR Illuminator only cost a tenner and could have got one for about £7
if I was willing to wait for it to come from China...

to go on floodlights to convert them to IR, a 500W halogen could barely
be seen behind one.

I wonder if I'm looking at the same stuff?

I've also used LEE Poly (polyester) filters in a Cokin mount (and black
bodge tape to keep the light out) . Apart from the fact they are
quite delicate (expensive sweet wrapper) they were fine.

They are a more reasonable price at about £17 for a 4" square.

Been playing a bit in the meantime, plain white paper isn't bad, lets
through a fair bit of IR and diffuses the red glow. Hadn't any black
paper to try. Remembered I had some lighting gels, a range of ND and
some colours for making anaglyph 3D glasses. They all transmit IR,
hardly surprising, stuck in front of a 2kW tungsten bubble they'd
melt even quicker if they absorbed IR...

With rather more reduction in IR than I'd like I've got the red glow
down to below being really noticeable, that's with 4 layers of 0.9 ND
and 7 of a blue, might be 132 Medium Blue. Of course it's a nearly
full moon and clear tonight so the camera is doing pretty well with
available light.

http://www.howhill.com/weather/webcam_24.php

The IR is for when it's dark and stormy so people can see how full
the road is getting with snow...

https://www.flickr.com/photos/allsorts-60/5228772002

--
Cheers
Dave.

On Thu, 29 Oct 2015 02:11:28 +0000 (GMT), "Dave Liquorice"
wrote:


The IR is for when it's dark and stormy so people can see how full
the road is getting with snow...

IR trailcams use one of two types of LED emitter, the 850nm LED emits
a noticeable dull red glow but have good range, the 940nm emit no
visible light at all but tend to have a shorter illumination range.
940 are used in covert illumination systems and IR remote controls.

http://www.amazon.co.uk/CMVision-IRP...R-Illuminators

http://www.ebay.co.uk/itm/5WATT-940n...-/180748844279

Dave Liquorice wrote:
Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a£10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.


I'd expect the IR to be close to a single wavelength, hence
filtering is unlikely to be very successful. The normal spectral
bandwidth is between 20 and 50nM AIUI for infra red diodes.

On Wed, 28 Oct 2015 22:37:08 +0000, Capitol wrote:

I'd expect the IR to be close to a single wavelength, hence filtering is
unlikely to be very successful.

Difficult to tell with the lighting gels if the visible reduction is
the same as the IR, I don't tink it is.

The normal spectral bandwidth is between 20 and 50nM AIUI for infra red
diodes.

That's sort of the idea behind getting a filter that transitions
fairly quickly as close to the bottom of the visible red as possible.
I'm not sure where the bottom of the visible red is, the 'net
produces a range from 650 to 750 nm. It'll obviously vary by
individual but 100 nm is at least 1/4 of the whole visible range...

--
Cheers
Dave.

"Dave Liquorice" wrote in message
ll.co.uk...

Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a £10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.


Might be worth talking to these guys:
http://srb-photographic.co.uk

On 28/10/2015 18:13, Dave Liquorice wrote:
Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a £10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.


Under a tenner on eBay. You just need to be patient with dellivery from
China.

On 28/10/2015 18:13, Dave Liquorice wrote:

Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

If you still have some lying around unexposed slide film tails is as
good as anything. It even works with human eyes if you make a good seal
and allow about two minutes to dark adapt. The scene reappears in pseudo
false colour with live plant foliage very light coloured.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a £10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.

I'd go for 780nm if you want to be reasonably sure of eliminating
obvious visibility. Even then some might see it. Schott RG780

http://www.us.schott.com/advanced_op...TT_rg780_e.pdf

These are colloidal glasses with quite sharp low pass.


715nm definitely will not cut it. Wratten87 should be OK.

--
Regards,
Martin Brown

They seem to be able to make remote controls cheaply enough, where do they
get the stuff from?
Brian

--
From the Sofa of Brian Gaff Reply address is active
Remember, if you don't like where I post
or what I say, you don't have to
read my posts! :-)
"Dave Liquorice" wrote in message
ll.co.uk...
Playing with a cheapo LED IR illuminator and webcam sensitive to IR.
Works well enough but the illuminator at night is a very visible red.
I've played with a bit of old floppy disc, that cuts the visible red
completely when a handful of yards from the illuminator. Trouble is
it also reduces the IR substantially as well.

You can get screw fitting IR pass filters for cameras(*) costing from
£30+ to under £10 and various start pass wavelengths. Has anyone any
experience
with the cheaper end filters? Is the transition from stop to pass
fairly sharp or spread out? Optical precision is not a requirement. A
4" square bit of Lee 87 polyester filter can be had for £15 that has
a published spec but is a £10 camera filter has the same or similar
performance...

On wavelength would a low 700's nm filter kill the visible red (a
very dull glow is OK) or does it need to be an 800 ish one? Obviously
the closer to the visible red the transition is the more IR there is
to illuminate things...

(*) 52 mm removed from the frame may well just replace the current
clear glass of the illuminator.

--
Cheers
Dave.

On 29/10/15 08:55, Brian-Gaff wrote:
They seem to be able to make remote controls cheaply enough, where do they
get the stuff from?
Brian

decent IR LEDS.


The OP obviously has LEDS that are at the bottom end of visible, not
truly in the IR spectrum


--
the biggest threat to humanity comes from socialism, which has utterly
diverted our attention away from what really matters to our existential
survival, to indulging in navel gazing and faux moral investigations
into what the world ought to be, whilst we fail utterly to deal with
what it actually is.

On 29/10/2015 09:49, The Natural Philosopher wrote:
On 29/10/15 08:55, Brian-Gaff wrote:

They seem to be able to make remote controls cheaply enough, where do
they
get the stuff from?
Brian

decent IR LEDS.

The OP obviously has LEDS that are at the bottom end of visible, not
truly in the IR spectrum

You can just about see the dim emission from nominal 750nm IR LEDs when
dark adapted. I suspect their FWHM is +/-10nm.

Never seen even a hint from 820 or 850nm ones.

--
Regards,
Martin Brown

On Thu, 29 Oct 2015 12:11:14 +0000, Martin Brown
wrote:


You can just about see the dim emission from nominal 750nm IR LEDs when
dark adapted. I suspect their FWHM is +/-10nm.

Never seen even a hint from 820 or 850nm ones.

The ones in the trailcam I have are 850nm and clearly visible as a
faint red light in the dark. The image here
http://www.omegacubed.net/bosch/bosc...d/ex26led.html is
pretty close to how they appear when viewed in the dark.

On Thu, 29 Oct 2015 16:18:22 +0000, Peter Parry wrote:

You can just about see the dim emission from nominal 750nm IR LEDs
when
dark adapted. I suspect their FWHM is +/-10nm.

Never seen even a hint from 820 or 850nm ones.

The ones in the trailcam I have are 850nm and clearly visible as a
faint red light in the dark. The image here
http://www.omegacubed.net/bosch/bosc...d/ex26led.html is
pretty close to how they appear when viewed in the dark.

The brighter spots are how the LEDs on this cheapo illuminator appear
in room lighting... At night from 20m away it's very obvious. Don't
know what the LEDs are, LEDs don't have a part No. stamped on them.

Put it back tonight and an awful lot of the IR has been filtered but
there is just enough to light things. On the other hand I've probably
over done the filtering, I could hardly see the red glow and I know
where to look! Also there is a lot of back scatter from the gels so
losses are probably higher than a single filter.

--
Cheers
Dave.

Security cams usually other way, solenoid operated IR CUT filter drops in during daylight and gets pulled out at night allowing illuminators to work.

Visble light generally thought of as 400-700nm.

On Thu, 29 Oct 2015 12:09:29 -0700 (PDT), Adam Aglionby wrote:

Security cams usually other way, solenoid operated IR CUT filter drops
in during daylight and gets pulled out at night allowing illuminators to
work.

This filter is for an illuminator not a camera so IR PASS is correct.
B-)

--
Cheers
Dave.