Economy thermal imager?

[Lostgallifreyan]

hal-usenet@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in
news:OrednYczvpQRLODXnZ2dnUVZ_j1i4p2d@megapath.net:

Apparently the Draper point at 798 K seems to be some standard for
visibility of hot objects, but I have not found any references how
this is actually determined.

wikipedia for John William Draper
http://en.wikipedia.org/wiki/John_William_Draper
says:

In 1847 he published the observation that all solids glow red at
about the same temperature, about 977 F (798 K), which has come
to be known as the Draper point.

It has a couple of references if you want more info.

I'm not sure that citing it as any guide to precision matters much. I just
tried that test I mentioned, I used a Weller WSD-81 'station' and an LR-21
iron, set at 450°C. I could see it before my eyes were fully dark-adapted,
but could not resolve colour. I could see it pretty much equally with
photopic or scotopic vision, done by arranging wide angle changes off-axis
from central vision, but I could only resolve any detail when it was at the
centre. Not much either, I couldn't see the tip shape very clearly but I
could see the silhouette of the heavy guard coil wire as it passed across it.

What did surprise me was that a small near-IR sniffer I built could not see
it. It's not very sensitive but I thought it ought to if I could, given the
stuff I've used it for before, so eyes are obviously rather good at this.
Couldn't see a thing at 400°C though.

 

[Archimedes' Lever]

On Wed, 22 Jul 2009 16:55:30 -0700 (PDT), "miso@sushi.com"
<miso@sushi.com> wrote:

Thermal imaging is in the 10um range, It
really detects infrared.

I know what thermal imaging is. I do not need a primer.

 

[Don Klipstein]

In <Xns9C6288007E4Azoodlewurdle@216.196.109.145>, Lostgallifreyan wrote:

hal-usenet@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in
news:OrednYczvpQRLODXnZ2dnUVZ_j1i4p2d@megapath.net:

Apparently the Draper point at 798 K seems to be some standard for
visibility of hot objects, but I have not found any references how
this is actually determined.

wikipedia for John William Draper
http://en.wikipedia.org/wiki/John_William_Draper
says:

In 1847 he published the observation that all solids glow red at
about the same temperature, about 977 F (798 K), which has come
to be known as the Draper point.

It has a couple of references if you want more info.

I'm not sure that citing it as any guide to precision matters much. I just
tried that test I mentioned, I used a Weller WSD-81 'station' and an LR-21
iron, set at 450°C. I could see it before my eyes were fully dark-adapted,
but could not resolve colour. I could see it pretty much equally with
photopic or scotopic vision, done by arranging wide angle changes off-axis
from central vision, but I could only resolve any detail when it was at the
centre. Not much either, I couldn't see the tip shape very clearly but I
could see the silhouette of the heavy guard coil wire as it passed across it.

This appears to me that you were seeing the very-dimly-glowing tip and
maybe the likely-slightly-hotter heating-element-area mostly with scotopic
vision.

450 C is 723 K. The surface over the heating element was likely
somewhat hotter, likely mid to upper 700's K.

The 798 K "Draper point" appears to me to be the threshold of achieving
significant stimulation of photopic vision to the point of seeing color
more than gray.

What did surprise me was that a small near-IR sniffer I built could not see
it. It's not very sensitive but I thought it ought to if I could, given the
stuff I've used it for before, so eyes are obviously rather good at this.

What wavelength range is your "near-IR sniffer" good at, and what
radiant power density in that wavelength range is lowest it will sense?
If you report this, I can figure temperature necessary to achieve this.

Couldn't see a thing at 400°C though.

I am not surprised - that is 673 K.

I consider myself optimistic at thinking that I may be able with best
dark adaptation to dimly see with blurred outlines and no color,
incandescence at 700 K.

I calculate the following values of candela per square centimeter to
photopic vision corresponding to the following temperatures low enough
to achieve glow so dim as to be seen primarily by scotopic vision despite
spectral content at wavelengths long enough to favor photopic:

775 K: 3.25 E-7 (s/p ratio is .131 on a scale where 555 nm
monochromatic yellow-green = 1)

750 K: 1.22 E-7 (s/p ratio is .119 on the above scale)

725 K: 4.27 E-8 (s/p ratio is .107 on the above scale)

700 K: 1.40 E-8 (s/p ratio is .096 on the above scale)

===============

Temperature at which s/p ratio achieved by a blackbody is "unity" as in
same as that of 555 nm yellowish-green monochromatic narrowband light:

2093 K,

which I have determined that a USA-usual 120V 100W lightbulb of
"Big 3 brand" and rated to last-on-average 750 hours and to
produce-on-average 1670-1750 lumens at 120 volts, to achieve at around
53-54 volts, maybe give or take another volt.

I am aware that a few lower-current longer-life vaccum-containing
incandescents have a fair chance of having color temperature this low or
slightly lower. However, it appears to me that more-usual for tungsten
incandescent lamps with design current low enough to be served better by
vacuum than by argon-nitrogen gas fill, along with design life expectancy
around 2,000-3,000 hours, is for color temperature to be not far from
2360 K (which achieves s/p ratio of 1.16 on scale where 555 nm achieves
unity).

The USA-usual 120V 100W incandescent with rated average life expectancy
of 750 hours, rated to produce 1670-1750 lumens, and having CC-6 or CC-8
filament, and of "Big 3 brand", appears to me to typically have color
temp. of 2870 K (2865 K by a slightly older definition revised by a
redetermination of one of 2 constants in the "Blackbody Formula"), appears
to me to achieve s/p ratio of about 1.42.

I hope the above supports my impression that human photopic and scotopic
vision have nonlinearities that differ from each other. I sense that
there is dynamic range compression achieved by both, less for human
photopic vision than for human scotopic vision.

I sense that human scotopic vision achieving greater dynamic range
compression than human photopic vision does, is the explanation for seeing
barely/hardly/minimally/dimly - incandescently-hot objects with color
"degrading to gray" (my words) as temperature decreases from about 800 K
or so to mid-700's K or so.

- Don Klipstein (Jr) (don@misty.com)

 

[Lostgallifreyan]

don@manx.misty.com (Don Klipstein) wrote in
news:slrnh7sqbd.qk8.don@manx.misty.com:

In <Xns9C6288007E4Azoodlewurdle@216.196.109.145>, Lostgallifreyan wrote:
hal-usenet@ip-64-139-1-69.sjc.megapath.net (Hal Murray) wrote in
news:OrednYczvpQRLODXnZ2dnUVZ_j1i4p2d@megapath.net:

Apparently the Draper point at 798 K seems to be some standard for
visibility of hot objects, but I have not found any references how
this is actually determined.

wikipedia for John William Draper
http://en.wikipedia.org/wiki/John_William_Draper
says:

In 1847 he published the observation that all solids glow red at
about the same temperature, about 977 F (798 K), which has come
to be known as the Draper point.

It has a couple of references if you want more info.

I'm not sure that citing it as any guide to precision matters much. I
just tried that test I mentioned, I used a Weller WSD-81 'station' and
an LR-21 iron, set at 450°C. I could see it before my eyes were fully
dark-adapted, but could not resolve colour. I could see it pretty much
equally with photopic or scotopic vision, done by arranging wide angle
changes off-axis from central vision, but I could only resolve any
detail when it was at the centre. Not much either, I couldn't see the
tip shape very clearly but I could see the silhouette of the heavy guard
coil wire as it passed across it.

This appears to me that you were seeing the very-dimly-glowing tip and
maybe the likely-slightly-hotter heating-element-area mostly with
scotopic vision.

That figures, but does scotopic vision also have resolving power at the
centre of vision? I was definitely seeing better imaging there..

450 C is 723 K. The surface over the heating element was likely
somewhat hotter, likely mid to upper 700's K.

The 798 K "Draper point" appears to me to be the threshold of
achieving
significant stimulation of photopic vision to the point of seeing color
more than gray.

Agreed. I'd have tested that, but the iron only went so far..

What did surprise me was that a small near-IR sniffer I built could not
see it. It's not very sensitive but I thought it ought to if I could,
given the stuff I've used it for before, so eyes are obviously rather
good at this.

What wavelength range is your "near-IR sniffer" good at, and what
radiant power density in that wavelength range is lowest it will sense?
If you report this, I can figure temperature necessary to achieve this.

Not really sure.. I built it from various RF plug parts and a couple of
button cells driving directly in series, an phototransistor and a high-
brightness green LED that happened to put out well at very low currents.

I think the phototransistor is an IR type from Maplin, 3mm package with
spectral peak response at 880 nm. Current varying betweem 0.1 mA and 20 mA
(which is why it seems so suited to direct LED drive). Those currents are
specified for 1000 lux and Vce of 3V but it saw less by one LED Vf, and its
sensitivity was further reduced by an IR pass filter made from the head of a
dark IR LED. I'd cut it off, polished (crudely, on a paper laid on glass),
then placed nose to nose to focus from a 5mm diameter region for best
coupling into the phototransistor while excluding any visible light.

This thing has been generally useful for seeing IR in various conditions
where it it would be within low visible intensities if it were visible at
all.

Couldn't see a thing at 400°C though.

I am not surprised - that is 673 K.

Yeah, just confirming that I couldn't. I could have tested at what point
between the two I lost sight of it, but it would taken a long time and not
proved a lot.

I consider myself optimistic at thinking that I may be able with best
dark adaptation to dimly see with blurred outlines and no color,
incandescence at 700 K.

Likely enough, I think. When I tried the 400°C test I thought I had seen
something but I tried the obvious test of sheilding it with my hand, and the
consciousness of the heat being shielded and the slight phosphenes (or
whatever they're called when slight neural generated effects occur) dominated
it. Even if I did see it it was lost in noise and loss of focus. So it was
doubt, rather than absolute nonseeing, so I am sure that at 425°C it ought to
be visible.

I calculate the following values of candela per square centimeter to
photopic vision corresponding to the following temperatures low enough
to achieve glow so dim as to be seen primarily by scotopic vision
despite spectral content at wavelengths long enough to favor photopic:

775 K: 3.25 E-7 (s/p ratio is .131 on a scale where 555 nm
monochromatic yellow-green = 1)

750 K: 1.22 E-7 (s/p ratio is .119 on the above scale)

725 K: 4.27 E-8 (s/p ratio is .107 on the above scale)

700 K: 1.40 E-8 (s/p ratio is .096 on the above scale)

===============

Temperature at which s/p ratio achieved by a blackbody is "unity" as
in
same as that of 555 nm yellowish-green monochromatic narrowband light:

2093 K,

which I have determined that a USA-usual 120V 100W lightbulb of
"Big 3 brand" and rated to last-on-average 750 hours and to
produce-on-average 1670-1750 lumens at 120 volts, to achieve at around
53-54 volts, maybe give or take another volt.

I am aware that a few lower-current longer-life vaccum-containing
incandescents have a fair chance of having color temperature this low or
slightly lower. However, it appears to me that more-usual for tungsten
incandescent lamps with design current low enough to be served better by
vacuum than by argon-nitrogen gas fill, along with design life
expectancy around 2,000-3,000 hours, is for color temperature to be not
far from 2360 K (which achieves s/p ratio of 1.16 on scale where 555 nm
achieves unity).

The USA-usual 120V 100W incandescent with rated average life
expectancy
of 750 hours, rated to produce 1670-1750 lumens, and having CC-6 or CC-8
filament, and of "Big 3 brand", appears to me to typically have color
temp. of 2870 K (2865 K by a slightly older definition revised by a
redetermination of one of 2 constants in the "Blackbody Formula"),
appears to me to achieve s/p ratio of about 1.42.

I hope the above supports my impression that human photopic and
scotopic
vision have nonlinearities that differ from each other. I sense that
there is dynamic range compression achieved by both, less for human
photopic vision than for human scotopic vision.

I sense that human scotopic vision achieving greater dynamic range
compression than human photopic vision does, is the explanation for
seeing barely/hardly/minimally/dimly - incandescently-hot objects with
color "degrading to gray" (my words) as temperature decreases from about
800 K or so to mid-700's K or so.

I read all that but I don't think I could have done it. Lets just say I make
an unusually good guinea pig.

I agree with the claim that scotopic vision has greater dynamic range though.
That fits my experience directly.

Possibly related to your comment on colour degrading, or perhaps not, is the
IR lased diodes. When I have seen them (5mw single mode types, looked at
directly at range greater than 1 foot, almost certainly eye-safe conditions)
they go beyond the wine or rubt reds of visible types. The impression is of a
maroon colour. (Yep, maroon, I ought to have mentioned it earlier in this
thread, no? > And what makes THAT interesting is that it implies a bluish
interpretation! Interesting given that deep violet at the other end hints at
a reddish interpretation of what is just a very deep blue. Life is full of
cylic/linear transforms, but this is the single weirdest one I know.

- Don Klipstein (Jr) (don@misty.com)

 

[Don Klipstein]

In article <Xns9C627A4B01391zoodlewurdle@216.196.109.145>,
Lostgallifreyan wrote in part:

don@manx.misty.com (Don Klipstein) wrote in
news:slrnh7sqbd.qk8.don@manx.misty.com:

<SNIP because I only have time at this moment to respond to one point:>

Possibly related to your comment on colour degrading, or perhaps not, is the
IR lased diodes. When I have seen them (5mw single mode types, looked at
directly at range greater than 1 foot, almost certainly eye-safe conditions)
they go beyond the wine or rubt reds of visible types. The impression is of a
maroon colour. (Yep, maroon, I ought to have mentioned it earlier in this
thread, no? > And what makes THAT interesting is that it implies a bluish
interpretation! Interesting given that deep violet at the other end hints at
a reddish interpretation of what is just a very deep blue. Life is full of
cylic/linear transforms, but this is the single weirdest one I know.

This reminds me of sensing some barely visible IR LEDs as emitting a
slightly orangish shade of red. I have seen their spectra with a
diffraction grating, and I know that I am seeing only very long
wavelengths past 750 nm, generally past 800 nm. I have seen the slightly
orangish shade of red in the long wavelength spectral region shown by the
diffraction grating, with the shorter wavelength end of the spectral band
appearing to me closer to pure red in color.

I have heard of this being called "color reversal" or "infrared color
reversal".

As for the soldering iron tip becoming more focused but still appearing
gray when viewed with central vision: I suspect that there are some rods
in central vision, in smaller and more closely spaced clusters to achieve
better resolution. Possibly photopic vision plays enough of a role to
increase sensation of resolution, however. However, I do see dimly
gray-appearing incandescent objects becoming invisible when viewed
entirely with the most central degree or two of vision. And when I look
at such an object that partially falls into the supposedly rod-free
most-central degree or two of vision, I sometimes tend to see the whole
thing anyway - maybe I get prone to "seeing things" under such conditions.

- Don Klipstein (don@misty.com)

 

[Lostgallifreyan]

don@manx.misty.com (Don Klipstein) wrote in
news:slrnh7u4fu.rnt.don@manx.misty.com:

Possibly related to your comment on colour degrading, or perhaps not, is
the IR lased diodes. When I have seen them (5mw single mode types,
looked at directly at range greater than 1 foot, almost certainly
eye-safe conditions) they go beyond the wine or rubt reds of visible
types. The impression is of a maroon colour. (Yep, maroon, I ought to
have mentioned it earlier in this thread, no? > And what makes THAT
interesting is that it implies a bluish interpretation! Interesting
given that deep violet at the other end hints at a reddish
interpretation of what is just a very deep blue. Life is full of
cylic/linear transforms, but this is the single weirdest one I know.

This reminds me of sensing some barely visible IR LEDs as emitting a
slightly orangish shade of red. I have seen their spectra with a
diffraction grating, and I know that I am seeing only very long
wavelengths past 750 nm, generally past 800 nm. I have seen the
slightly orangish shade of red in the long wavelength spectral region
shown by the diffraction grating, with the shorter wavelength end of the
spectral band appearing to me closer to pure red in color.

I have heard of this being called "color reversal" or "infrared color
reversal".

Weird. I have read of this before, but I don't know why it should be. The
maroon I sort of understand, it fits with a kind of mapping of spectrum as
circle, a standard practise in Microsoft colour picker dialogs for example..
Maybe our brains give interpretations to fit models we already have? These
models may work at a very primal level too.

As for the soldering iron tip becoming more focused but still
appearing
gray when viewed with central vision: I suspect that there are some
rods in central vision, in smaller and more closely spaced clusters to
achieve better resolution. Possibly photopic vision plays enough of a
role to increase sensation of resolution, however. However, I do see
dimly gray-appearing incandescent objects becoming invisible when viewed
entirely with the most central degree or two of vision. And when I look
at such an object that partially falls into the supposedly rod-free
most-central degree or two of vision, I sometimes tend to see the whole
thing anyway - maybe I get prone to "seeing things" under such
conditions.

Brains again.. I've noticed mine has an amazing ability to fill in missing
detail. Can be the cause of error as much as a cure for it. It's entirely
possible that although I do see that weakly hot iron in the centre of my
vision, any impression of better definition is purely my brain filling in
because it expects it, and knows what the iron looks like already. The
silhouette of the guard coil was real though, it presented itself as an
unfamiliar effect somehow even though logically I should have expected to see
it. I've learned to gauge when my brain is 'filling in' because when that
happens the impression often has a suspiciously familiar aspect when a true
new observation probably could not feel that way. But I usually avoid this
when trying to establish a fact, it's the equivalent of trying to design for
an op-amp at an extreme of its capability.

One thing I do remember, looking at a comet. That vanished when I looked
directly at it. The only way to see it was with peripheral vision, and to
keep moving slowly, too, so it triggered new cells and didn't get lost in
noise and distractions. Different spectrum of light, but still obviously
scotopic..

 

[JosephKK]

On Tue, 11 Aug 2009 14:10:54 -0500, Lostgallifreyan
<no-one@nowhere.net> wrote:

don@manx.misty.com (Don Klipstein) wrote in
news:slrnh7u4fu.rnt.don@manx.misty.com:

Possibly related to your comment on colour degrading, or perhaps not, is
the IR lased diodes. When I have seen them (5mw single mode types,
looked at directly at range greater than 1 foot, almost certainly
eye-safe conditions) they go beyond the wine or rubt reds of visible
types. The impression is of a maroon colour. (Yep, maroon, I ought to
have mentioned it earlier in this thread, no? > And what makes THAT
interesting is that it implies a bluish interpretation! Interesting
given that deep violet at the other end hints at a reddish
interpretation of what is just a very deep blue. Life is full of
cylic/linear transforms, but this is the single weirdest one I know.

This reminds me of sensing some barely visible IR LEDs as emitting a
slightly orangish shade of red. I have seen their spectra with a
diffraction grating, and I know that I am seeing only very long
wavelengths past 750 nm, generally past 800 nm. I have seen the
slightly orangish shade of red in the long wavelength spectral region
shown by the diffraction grating, with the shorter wavelength end of the
spectral band appearing to me closer to pure red in color.

I have heard of this being called "color reversal" or "infrared color
reversal".


Weird. I have read of this before, but I don't know why it should be. The
maroon I sort of understand, it fits with a kind of mapping of spectrum as
circle, a standard practise in Microsoft colour picker dialogs for example..
Maybe our brains give interpretations to fit models we already have? These
models may work at a very primal level too.

Simply put, just harmonics (frequency doubling/tripling). Many more
complex things are significant contributors as well.

As for the soldering iron tip becoming more focused but still
appearing
gray when viewed with central vision: I suspect that there are some
rods in central vision, in smaller and more closely spaced clusters to
achieve better resolution. Possibly photopic vision plays enough of a
role to increase sensation of resolution, however. However, I do see
dimly gray-appearing incandescent objects becoming invisible when viewed
entirely with the most central degree or two of vision. And when I look
at such an object that partially falls into the supposedly rod-free
most-central degree or two of vision, I sometimes tend to see the whole
thing anyway - maybe I get prone to "seeing things" under such
conditions.


Brains again.. I've noticed mine has an amazing ability to fill in missing
detail. Can be the cause of error as much as a cure for it. It's entirely
possible that although I do see that weakly hot iron in the centre of my
vision, any impression of better definition is purely my brain filling in
because it expects it, and knows what the iron looks like already. The
silhouette of the guard coil was real though, it presented itself as an
unfamiliar effect somehow even though logically I should have expected to see
it. I've learned to gauge when my brain is 'filling in' because when that
happens the impression often has a suspiciously familiar aspect when a true
new observation probably could not feel that way. But I usually avoid this
when trying to establish a fact, it's the equivalent of trying to design for
an op-amp at an extreme of its capability.

One thing I do remember, looking at a comet. That vanished when I looked
directly at it. The only way to see it was with peripheral vision, and to
keep moving slowly, too, so it triggered new cells and didn't get lost in
noise and distractions. Different spectrum of light, but still obviously
scotopic..

 

[JosephKK]

On Fri, 07 Aug 2009 08:12:23 -0500, Lostgallifreyan
<no-one@nowhere.net> wrote:

"JosephKK"<quiettechblue@yahoo.com> wrote in
news:jk4o751192hv04vit912ulhssfp7048dsl@4ax.com:

IIRC many common soldering irons run in the 600 F to 700 F range (not
all that far from visible glow) and may well output enough for a
modified digicam. I swear, that as child i could see the soldering
iron by its own glow (in the middle of the night when i woke for some
reason) some night when i left it plugged in.


I believe it. I've seen them at times. I can't tell when sight ends and
imagination begins though, I tried.. > I have a nice temperature controlled
iron now so I'll try this again some time. Helps to try to see it with the
rods, not the cones, so at least thirty degrees to the side.

This is back some decades ago when i was a teen. My eyes were really
sensitive, bright summer daylight caused me pain. BTW the soldering
iron was an old ungar imperial with a 40 W cartridge.

 

[Lostgallifreyan]

"JosephKK"<quiettechblue@yahoo.com> wrote in
news:niob85de1567eh7mb3t6cl3nr3btav4ojf@4ax.com:

Simply put, just harmonics (frequency doubling/tripling). Many more
complex things are significant contributors as well.

Seems doubtful to me. There is a doubling effect in the materials of the eye
apparently, people exposed to 1064 nm beams have reported seeing a green
flash of doubled-to-532nm light. I can't cite where I saw it because I can't
remember but it has been mentioned on alt.lasers at times. It's a result of
high intensity though, not low. It takes a lot of energy to produce the
nonlinear effects needed to do it.

I don't know what to think though, most explanations I've seen have problems
that make them unlikely. For example, the intensity needed to fire off a
strong green flash in the eyeball might need to be so strong that the last
thing the observer would be concerned with would be the perceived colour..

 

[Martin Brown]

JosephKK wrote:

On Tue, 11 Aug 2009 14:10:54 -0500, Lostgallifreyan
no-one@nowhere.net> wrote:

don@manx.misty.com (Don Klipstein) wrote in
news:slrnh7u4fu.rnt.don@manx.misty.com:

Possibly related to your comment on colour degrading, or perhaps not, is
the IR lased diodes. When I have seen them (5mw single mode types,
looked at directly at range greater than 1 foot, almost certainly
eye-safe conditions) they go beyond the wine or rubt reds of visible
types. The impression is of a maroon colour. (Yep, maroon, I ought to
have mentioned it earlier in this thread, no? > And what makes THAT
interesting is that it implies a bluish interpretation! Interesting
given that deep violet at the other end hints at a reddish
interpretation of what is just a very deep blue. Life is full of
cylic/linear transforms, but this is the single weirdest one I know.
This reminds me of sensing some barely visible IR LEDs as emitting a
slightly orangish shade of red. I have seen their spectra with a
diffraction grating, and I know that I am seeing only very long
wavelengths past 750 nm, generally past 800 nm. I have seen the
slightly orangish shade of red in the long wavelength spectral region
shown by the diffraction grating, with the shorter wavelength end of the
spectral band appearing to me closer to pure red in color.

I have heard of this being called "color reversal" or "infrared color
reversal".

Weird. I have read of this before, but I don't know why it should be. The
maroon I sort of understand, it fits with a kind of mapping of spectrum as
circle, a standard practise in Microsoft colour picker dialogs for example..
Maybe our brains give interpretations to fit models we already have? These
models may work at a very primal level too.

Simply put, just harmonics (frequency doubling/tripling). Many more
complex things are significant contributors as well.

No. Frequency doubling requires very high light intensities and usually
a crystal lattice with a heavy highly charged ion in it.

It is more likely to be a quirk of the light sensitive pigments of the
eye. A lot of nominally blue pigments and dyes have near IR leaks and I
expect the eye pigment is no different. Also at the low sensitivity
needed for near IR most of the colour vision is gone for me so it is
essentially grey with a hint of orange. NB red is constructed by the
brain as yellow-green. The eye cones are sensitive to yellow, green and
blue. Red is a construction of the brain.

You can have fun with this perceptual feature by using a neodymium
filter over the eyes which creates out of gamut colours for the brain to
contend with that are "redder than red" and "greener than green".

Regards,
Martin Brown

 

[notme]

On Wed, 22 Jul 2009 16:00:31 -0700, Archimedes' Lever wrote
(in article <9e6f65lgevbktpfqearr1g0dl3jm1jgcc0@4ax.com&gt:

Might as well buy the real IR imagers that the security camera folks
are pushing now, if you are going to do that.

I think they sell them by the box at Frys'.

When i search Frys.com for "infrared" I get all kinds of IR communication
devices (headphones, etc.), an intrusion-sensor security system, and one
security camera that uses IR illumination.

Is this what you mean? ::

<http://www.frys.com/product/5382748?site=sr:SEARCH:MAIN_RSLT_PG>

Thanks.

 

[Lostgallifreyan]

Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote in
news:Fruhm.267740$Ta5.241754@newsfe15.iad:

Also at the low sensitivity
needed for near IR most of the colour vision is gone for me so it is
essentially grey with a hint of orange.

That relates to what Don Klipstein said, and I've been thinking about that..
it's ame for me if the source is low intensity, broadband, and at edges of
IR. Orangish greyish brownish.. But what if the source is narrowband, much
deeper into IR, and fairly strong? To me such sources (unlensed 5 mW laser
diodes, etc) look maroon, a distinct red that is so deep and dark it is to
red as deep violet is to blue. And both ends of the spectrum seem to reach
toward each other like the closing of a circle. Anyone else see it this way?

NB red is constructed by the

brain as yellow-green. The eye cones are sensitive to yellow, green and
blue. Red is a construction of the brain.

You can have fun with this perceptual feature by using a neodymium
filter over the eyes which creates out of gamut colours for the brain to
contend with that are "redder than red" and "greener than green".

Where can I get one? This needs trying. What form is the neodymium in,
obviously not metal sheet... Doped glass?

 

[Hal Murray]

That relates to what Don Klipstein said, and I've been thinking about that..
it's ame for me if the source is low intensity, broadband, and at edges of
IR. Orangish greyish brownish.. But what if the source is narrowband, much
deeper into IR, and fairly strong? To me such sources (unlensed 5 mW laser
diodes, etc) look maroon, a distinct red that is so deep and dark it is to
red as deep violet is to blue. And both ends of the spectrum seem to reach
toward each other like the closing of a circle. Anyone else see it this way?

Years ago, I collected a set of LEDs with various wavelengths.
One was 700 nm. It was a very pleasant (to my eye) deep red.

It might have had a hint of purple in it, but I don't think that's
how I would have described it. If you had used that word I probably
would not have said you were nuts. (Again, that's from several
years ago.)

--
These are my opinions, not necessarily my employer's. I hate spam.

 

[Archimedes' Lever]

On Fri, 24 Jul 2009 20:00:33 -0700, Archimedes' Lever
<OneBigLever@InfiniteSeries.Org> wrote:

At the same time, Fischer Price sold a B&W "toy" camera for $150 that
could have a Ge or Pyrex lens or filter put on it, and it would do IR
very nicely.

Perfect proof that most in the group are idiots.

Not one comment on this well known anomaly as the years ticked by.

Now, the idiots are even talking about a reduced range setup.

This toy was around in 1987. I am sure many can be found in the used
channels.

http://cgi.ebay.com/Two-Fisher-Price-PXL-200-Cameras-and-Accessories_W0QQitemZ330351328339QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item4cea793c53&_trksid=p3286.c0.m14

 

[OutsideObserver]

On Sat, 15 Aug 2009 11:02:06 -0500, Lostgallifreyan <no-one@nowhere.net>
wrote:

Martin Brown <|||newspam|||@nezumi.demon.co.uk> wrote in
news:Fruhm.267740$Ta5.241754@newsfe15.iad:

Also at the low sensitivity
needed for near IR most of the colour vision is gone for me so it is
essentially grey with a hint of orange.

That relates to what Don Klipstein said, and I've been thinking about that..
it's ame for me if the source is low intensity, broadband, and at edges of
IR. Orangish greyish brownish.. But what if the source is narrowband, much
deeper into IR, and fairly strong? To me such sources (unlensed 5 mW laser
diodes, etc) look maroon, a distinct red that is so deep and dark it is to
red as deep violet is to blue. And both ends of the spectrum seem to reach
toward each other like the closing of a circle. Anyone else see it this way?

NB red is constructed by the
brain as yellow-green. The eye cones are sensitive to yellow, green and
blue. Red is a construction of the brain.

You can have fun with this perceptual feature by using a neodymium
filter over the eyes which creates out of gamut colours for the brain to
contend with that are "redder than red" and "greener than green".


Where can I get one? This needs trying. What form is the neodymium in,
obviously not metal sheet... Doped glass?

You guys should talk to this guy. He knows exactly what he is doing.

His name is waterhed

http://cgi.ebay.com/Modified-Pxl-2000-Pixelvision-Camcorder-Pxl2000-Camera_W0QQitemZ120457191739QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item1c0bcee13b&_trksid=p3286.c0.m14

 

[Martin Brown]

Hal Murray wrote:

That relates to what Don Klipstein said, and I've been thinking about that..
it's ame for me if the source is low intensity, broadband, and at edges of
IR. Orangish greyish brownish.. But what if the source is narrowband, much
deeper into IR, and fairly strong? To me such sources (unlensed 5 mW laser
diodes, etc) look maroon, a distinct red that is so deep and dark it is to
red as deep violet is to blue. And both ends of the spectrum seem to reach
toward each other like the closing of a circle. Anyone else see it this way?

Years ago, I collected a set of LEDs with various wavelengths.
One was 700 nm. It was a very pleasant (to my eye) deep red.

The nominal peak wavelength of an LED is +/- 20nm so there would be some
visible deep red component in the wings unless you also had a long
pass filter. A lot of IR LEDs have a black organic dye in them to mask
any trace of visible red emission. 750nm & 820nm ones look pretty well
black to me.

Regards,
Martin Brown

 

[miso@sushi.com]

On Aug 15, 8:26 am, notme <no...@notme.org> wrote:

On Wed, 22 Jul 2009 16:00:31 -0700, Archimedes' Lever wrote
(in article <9e6f65lgevbktpfqearr1g0dl3jm1jg...@4ax.com&gt:

  Might as well buy the real IR imagers that the security camera folks
are pushing now, if you are going to do that.

  I think they sell them by the box at Frys'.

When i search Frys.com for "infrared" I get all kinds of IR communication
devices (headphones, etc.), an intrusion-sensor security system, and one
security camera that uses IR illumination.

Is this what you mean? ::

http://www.frys.com/product/5382748?site=sr:SEARCH:MAIN_RSLT_PG

Thanks.

Yes, that is what not to buy. ;-)

This is an example of a very sensitive B&W camera that has some near
IR response
http://www.supercircuits.com/Security-Cameras/Specialty-Security-Cameras/PC164C
Unfortunately, this one is CS mount. I can't say for sure if you can
use a C mount lens on it. I have an older version that is C mount. The
idea is you get a large aperture c-mount lens, which isn't all that
hard these days if you want something that is purely mechanical (i.e
no electronic iris). Ebay has no shortage of C mount lens. If you get
serious about this and want a follow up, start another thread as this
one is pretty much hijacked.

 

[Fester Bestertester]

At the same time, Fisher Price sold a B&W "toy" camera for $150 that
could have a Ge or Pyrex lens or filter put on it, and it would do IR
very nicely.

Where would one find such a lens to replace the standard lens?

Thanks.

 

[Archimedes' Lever]

On Sun, 16 Aug 2009 00:06:54 -0700, Fester Bestertester <fbt@fbt.net>
wrote:

At the same time, Fisher Price sold a B&W "toy" camera for $150 that
could have a Ge or Pyrex lens or filter put on it, and it would do IR
very nicely.

Where would one find such a lens to replace the standard lens?

Thanks.

Did you think to try Edmund Scientific or some optical lens coating
supplier?

http://www.edmundoptics.com/onlinecatalog/search/index.cfm

 

[John Larkin]

On Sat, 15 Aug 2009 10:05:24 -0700, Archimedes' Lever
<OneBigLever@InfiniteSeries.Org> wrote:

On Fri, 24 Jul 2009 20:00:33 -0700, Archimedes' Lever
OneBigLever@InfiniteSeries.Org> wrote:

At the same time, Fischer Price sold a B&W "toy" camera for $150 that
could have a Ge or Pyrex lens or filter put on it, and it would do IR
very nicely.


Perfect proof that most in the group are idiots.

Not one comment on this well known anomaly as the years ticked by.

The FP uses a CCD so can't work as a thermal imager. Near IR, maybe,
but that isn't germanium lens territory.

http://www.thorlabs.com/images/TabImages/GermaniumTrans.jpg

Most digital cameras work nicely in the near IR.

John