OT: Ways to read hidden lettering?

N

N_Cook

Guest
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
 
On 04/24/2015 7:45 AM, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
Click to expand...

Why not make your own IR camera:

http://www.picturecorrect.com/tips/how-to-build-your-own-infrared-camera/

Lots online when you search for "Make your own IR camera"

John :-#)#
--
(Please post followups or tech inquiries to the USENET newsgroup)
John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)
www.flippers.com
"Old pinballers never die, they just flip out."
 
On 24/04/2015 16:16, John Robertson wrote:
On 04/24/2015 7:45 AM, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras

Why not make your own IR camera:

http://www.picturecorrect.com/tips/how-to-build-your-own-infrared-camera/

Lots online when you search for "Make your own IR camera"

John :-#)#
Click to expand...

I've only tried my hacked IR filter-less camera with IR zappers, not
tried to take a pic of anything. I'd not considered adding an IR-pass /
visible cut filter, as in that file. I wonder what material that is mase
of, polythene? I know that passes the IR of PIR use, whatever wavelength
that is.
I also assume the IR of such a modified camera without germanium lens is
only sensitive to about 1 to 3 micron IR
 
from
http://www.instructables.com/id/Floppy-Disk-IR-Camera-Hack
it seems floppy disc material, passes IR and blocks visible for this purpose
 
On Fri, 24 Apr 2015 08:16:57 -0700, John Robertson <spam@flippers.com>
wrote:

On 04/24/2015 7:45 AM, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras

Why not make your own IR camera:

http://www.picturecorrect.com/tips/how-to-build-your-own-infrared-camera/

Lots online when you search for "Make your own IR camera"

John :-#)#
Click to expand...
Thanks for posting that link John. It really makes me want to buy
another camera to modify. Since I have a machine shop any physical
mods and special filter mounts will be easy for me. In fact, I built a
filter/lens mount for my Sony DSC-120 Cybershot camera. This has
allowed me to mount telephoto and fisheye lenses to it.
Eric
 
On Fri, 24 Apr 2015 15:45:33 +0100, N_Cook <diverse@tcp.co.uk> wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
Click to expand...
Wasn't it you who tried taking an IR filter out of a camera and found
that it would not focues without the filter in place? John, posted a
link in a reply to your post . The article the link points to says
that some cameras will need the IR filter replaced with a piece of
glass the same physical size for the camera to work properly. You
should read the article. It has some pictures that were taken with
various filters that only let in certain wavelengths of IR and blocked
all visible light. I can see how this might work for you project.
Eric
 
On 24/04/2015 18:02, etpm@whidbey.com wrote:
On Fri, 24 Apr 2015 15:45:33 +0100, N_Cook <diverse@tcp.co.uk> wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
Wasn't it you who tried taking an IR filter out of a camera and found
that it would not focues without the filter in place? John, posted a
link in a reply to your post . The article the link points to says
that some cameras will need the IR filter replaced with a piece of
glass the same physical size for the camera to work properly. You
should read the article. It has some pictures that were taken with
various filters that only let in certain wavelengths of IR and blocked
all visible light. I can see how this might work for you project.
Eric
Click to expand...

guilty, that was on a close to scrapper camera, just used as a trial
run, not worried if I wrecked it. The current one I've removed the IR
blocking filter from, was a thin sheet , not a block of material like
the one of my previous posting
 
On Fri, 24 Apr 2015 15:45:33 +0100, N_Cook wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
Click to expand...

Hmmm, those terahertz airport scanners are rumoured to be able to see
through clothing, so perhaps they would work. May be difficult to beg,
steal or borrow one, though...

Mike.
 
On 24/04/2015 18:36, Mike wrote:
On Fri, 24 Apr 2015 15:45:33 +0100, N_Cook wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras

Hmmm, those terahertz airport scanners are rumoured to be able to see
through clothing, so perhaps they would work. May be difficult to beg,
steal or borrow one, though...

Mike.
Click to expand...

I wonder how many people had accidently lost their "X-ray" Sony
camcorder so they could not surrender it .
http://www.liveleak.com/view?i=faf_1385072214
 
In article <mhdrpt$p42$1@dont-email.me>, N_Cook <diverse@tcp.co.uk> wrote:

I've only tried my hacked IR filter-less camera with IR zappers, not
tried to take a pic of anything. I'd not considered adding an IR-pass /
visible cut filter, as in that file. I wonder what material that is mase
of, polythene?
Click to expand...

You can make an acceptable IR-pass, visible-block filter using a thin
piece of black-colored acrylic sheet plastic ("Plexiglas"). The black
color is apparently a dye, not a pigment.

I've taken some acceptable near-IR photos using this technique, with
an old Canon digital camera whose sensor lacks an IR filter. It
requires an exposure of several seconds but it does work.
 
In article <mhdksj$sro$1@dont-email.me>, N_Cook <diverse@tcp.co.uk>
wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
Click to expand...

If you can hack the old tech, IR film (of the roll in the camera, take
pictures you can't see, process in a darkroom with wet chemistry sort)
might be a way to access near-visible IR photography on a lower budget.

Before you rip out the IR filter, check the camera (or various cameras)
with the source - many cell phone cameras (at least) can "see" enough
near-IR to show near-IR sources without removing a filter.

Visible light, digital camera and image post-processing MIGHT do it.

Different but similar application with old letters (literary estate) and
blacked out parts was sorted by scanning at high color depth and
separating brown-ish-black from blue-ish-black as the ink written in and
the ink blacked out with were different. Not my project, went to a talk
at a conference where it was presented.

--
Cats, coffee, chocolate...vices to live by
Please don't feed the trolls. Killfile and ignore them so they will go away.
 
On Fri, 24 Apr 2015 08:16:57 -0700, John Robertson <spam@flippers.com>
wrote:

On 04/24/2015 7:45 AM, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras

Why not make your own IR camera:

http://www.picturecorrect.com/tips/how-to-build-your-own-infrared-camera/

Lots online when you search for "Make your own IR camera"

John :-#)#
Click to expand...
John-I got all jazzed up reading the article you posted the link to.
Then I looked at some more. Then a little later I made a trip to the
hardware store and stopped in the thrift store a few doors down to
look for a camera. Dropped 8 bucks and came home with two Cannon ELPH
cameras. I don't know yet if eather camera works but for 8 bucks it
was worth the risk.
Eric
 
On 24/04/2015 19:13, Dave Platt wrote:
In article <mhdrpt$p42$1@dont-email.me>, N_Cook <diverse@tcp.co.uk> wrote:

I've only tried my hacked IR filter-less camera with IR zappers, not
tried to take a pic of anything. I'd not considered adding an IR-pass /
visible cut filter, as in that file. I wonder what material that is mase
of, polythene?

You can make an acceptable IR-pass, visible-block filter using a thin
piece of black-colored acrylic sheet plastic ("Plexiglas"). The black
color is apparently a dye, not a pigment.

I've taken some acceptable near-IR photos using this technique, with
an old Canon digital camera whose sensor lacks an IR filter. It
requires an exposure of several seconds but it does work.
Click to expand...

I've just butchered a 3.25" floppy disc and quite a nice sepia tone to
the outdoor scene I was looking at it through, not tried on the camera yet.
 
On 24/04/2015 19:49, Ecnerwal wrote:
In article <mhdksj$sro$1@dont-email.me>, N_Cook <diverse@tcp.co.uk
wrote:

Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.

If you can hack the old tech, IR film (of the roll in the camera, take
pictures you can't see, process in a darkroom with wet chemistry sort)
might be a way to access near-visible IR photography on a lower budget.

Before you rip out the IR filter, check the camera (or various cameras)
with the source - many cell phone cameras (at least) can "see" enough
near-IR to show near-IR sources without removing a filter.

Visible light, digital camera and image post-processing MIGHT do it.

Different but similar application with old letters (literary estate) and
blacked out parts was sorted by scanning at high color depth and
separating brown-ish-black from blue-ish-black as the ink written in and
the ink blacked out with were different. Not my project, went to a talk
at a conference where it was presented.
Click to expand...

"photoshopping" I can see has possibilities here as I'm only interested
in reading the text , ie differentiatable colour or luminance levels,
not pictures of foliage against black skies or anything artistic.
 
On 24/04/2015 15:45, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras
Click to expand...

To be honest I think your best bet is to illuminate the scene with
filtered longwave IR (and no visible) and use an amateur astronomy CCD
camera time exposure to try and image through the wallpaper. How well it
works depends on how much pigment is in the wallpaper. The paper should
be moderately transparent to IR but the pigments may not be.

These cameras are relatively common and your local astronomy club might
well have someone who is game to give it a try. The difficulty is that
there is a limit to how well glass lenses transmit IR. The other problem
is that you will need to do it with a quality longpass filter as you are
in the noise >> signal regime on this one.

The FLIR addon for an iPhone5 would be another option.
http://www.amazon.com/FLIR-ONE-Thermal-Imager-iPhone/dp/B00K0PXFB6/ref=sr_1_1?ie=UTF8&qid=1429954794&sr=8-1&keywords=flir

Possibly the one with the best chance of success if you don't know
someone who owns a genuine FLIR camera.

--
Regards,
Martin Brown
 
On 25/04/2015 10:44, Martin Brown wrote:
On 24/04/2015 15:45, N_Cook wrote:
Situation is wishing to read some black gloss-painted letters over white
emulsion painted plaster, but for a few decades has been covered by
wallpaper. Setting is a commercial premises that permission to
non-invasively explore would be possible but steaming off wallpaper and
remedial work (no matching new wallpaper found) is not permitted.
3 ideas so far, any suggestions relating to these , or any other ideas?

1/ A 3W <>.9micron wavelength IR torch bought and on the way, in
conjunction with a webcam that I've removed the IR filter from and
checked with IR zappers as responsive.
2/ I'll also try a vitreous resistor set in a chromed cone in
conjunction with a keyfob pyro thermometer, for 10 to 25 micron IR
"interogation". The wallpaper is striped so it may be possible to move
the pyro, parallel to the lines, if the wallpaper dyestuff interferes
with any response. Recording the temperature change with X and Y , if
any differentiatable changes become apparent.
3/ high power directed white light and neutral density film over a
camera lens.
I'll make a test bed of some black painted letters of the relevant size
on plaster covered with some wallpaper. Letters are known to be about
65mm high and letter thickness of black paint about 6mm, as they were
stencilled. Wallpaper is simple uniform thickness, not anaglypta.

Hiring a pro IR video camera is out of the question as too pricey and
may not work for this use anyway . I'm still looking for somewhere that
might hire (for some reasonable fee) one of the low res <>60x80 pixel IR
video cameras

To be honest I think your best bet is to illuminate the scene with
filtered longwave IR (and no visible) and use an amateur astronomy CCD
camera time exposure to try and image through the wallpaper. How well it
works depends on how much pigment is in the wallpaper. The paper should
be moderately transparent to IR but the pigments may not be.

These cameras are relatively common and your local astronomy club might
well have someone who is game to give it a try. The difficulty is that
there is a limit to how well glass lenses transmit IR. The other problem
is that you will need to do it with a quality longpass filter as you are
in the noise >> signal regime on this one.

The FLIR addon for an iPhone5 would be another option.
http://www.amazon.com/FLIR-ONE-Thermal-Imager-iPhone/dp/B00K0PXFB6/ref=sr_1_1?ie=UTF8&qid=1429954794&sr=8-1&keywords=flir


Possibly the one with the best chance of success if you don't know
someone who owns a genuine FLIR camera.
Click to expand...

agreed one of those add-ons or the low res FLIR cameras , but just for a
one-off job , cannot justify the prices or even to hire one for one day.


I've now got a test patch of wall with painted on gloss black 3 letters
of the right size, will wallpaper over it on Monday.
 
On 25-Apr-15 12:49 AM, N_Cook wrote:
from
http://www.instructables.com/id/Floppy-Disk-IR-Camera-Hack
it seems floppy disc material, passes IR and blocks visible for this
purpose
Click to expand...

So does exposed & developed 35mm film.
 
On 25/04/2015 13:38, RodK wrote:
On 25-Apr-15 12:49 AM, N_Cook wrote:
from
http://www.instructables.com/id/Floppy-Disk-IR-Camera-Hack
it seems floppy disc material, passes IR and blocks visible for this
purpose


So does exposed & developed 35mm film.
Click to expand...

ITYM *unexposed* developed slide film which is a good cheap IR long pass
filter since the dyes block most of the visible light.

Using it for viewing eclipses or looking at the sun can cause serious
eye damage since it makes the visible light level tolerable whilst still
allowing enough near IR through to cause retinal burns.

--
Regards,
Martin Brown
 
On 4/25/2015 9:09 AM, Martin Brown wrote:
On 25/04/2015 13:38, RodK wrote:
On 25-Apr-15 12:49 AM, N_Cook wrote:
from
http://www.instructables.com/id/Floppy-Disk-IR-Camera-Hack
it seems floppy disc material, passes IR and blocks visible for this
purpose


So does exposed & developed 35mm film.

ITYM *unexposed* developed slide film which is a good cheap IR long pass
filter since the dyes block most of the visible light.

Using it for viewing eclipses or looking at the sun can cause serious
eye damage since it makes the visible light level tolerable whilst still
allowing enough near IR through to cause retinal burns.
Click to expand...
Exposed colour negative film is OK too. The main difference is the
strong orange cast of the film stock, but you don't care in an IR filter.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net
 
No discussion of the small halogen bulb or vitreous resistor set at the
apex of an insulated chromed brass cone for a long wavelength IR
illuminator, in conjunction with one of these
http://www.maplin.co.uk/p/pocket-infrared-thermometer-n19fr
keyfob IR thermometer I use for locating hotspots on circuit boards.
Now I have a test bed of hidden letters i can have a go at different
settings. But any suggestions of what sort of wattage and temperature
may show the greatest contrast of white and black under paper?
 
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