Is the human eye capable of seing infrared?

[Parker North]

The human ey can "percieve" waves beyound 750 nM but to be able to
discern the image.........no way in hell. Golly why would we need
to perfect night vision glasses if we could actually see at the 1uM
range?

Beyond me, but I like this Doc. Nuff said.. ;-)

 

[Dr. Don Sandell]

Thanx Parker,

Physiology is my forte'.

 

[kenw]

Actually it can image just fine to 1um, that's why lasers in this region are extremely dangerous. The lens and vitrea are transparent at these wavelengths, the photopigments do absorb in these wavelengths although their photoresponse is very poor (100-1000 times less sensitive than in the red). You don't get a blink response typically because of poor sensitivity but the laser spot still focuses on to the retina and toasts it. In a dark room, with no other light around to mask it, you can see in these wavelengths with an incredibly bright source. Again, a situation you'd have to go to a lot of trouble to create.

As for your night vision googles comment I think you are very confused about IR wavelengths and night vision google types. At 1 um the night is just as dark as at 700 nm. Night vision googles come in three kinds:

Near IR illuminators: These shine a bright light in the 900 nm range to illuminate the scene and have an imager with response in this region. Obviously you can't see any further than your light source (just like a flash light). Since our photo response is so poor to 900 nm light no one else can see your floodlight and you remain stealthy. Unless of course they have same googles and they see your head light. These DO NOT see heat. They simply see the reflection of the IR illuminator. It is just like shining a flash light around, except no one else can see your flash light. This is what the 717 nightshot mode is. If you take a really bright illuminator into a dark room you can actually see it glow.

Image intensifiers: These are what true NVGs used in the military are. They use a photomultiplier scheme to convert photons to electrons, then multiply the electrons up, and crash them into a phosphorescent screen. These amplify all wavelengths in the visible and near IR. These can not see in true total darkness, but even starlight is plenty for them to work with.

Long IR imagers: I don't think there are any "goggles" persay like this but many sights and cameras used for recon and targeting use these. Imaging is done in the 3-5um or 7-10um range, way way longer than 1um. These are heat imagers. Things near 273K (room temp) emit around here as well as exhaust plumes. These are not imaging reflected light, but rather the IR wavelengths emitted as blackbody radiation from the targets. The eye has absolutely no response in this region, the lens stops focusing well, and the vitrea starts to absorb in this region as well. At long enough wavelengths the lens it self is nearly opaque.

So again, eye does respond, very very poorly out to 1um, the lens does focus images in this region, but to ever truely "see" anything at these wavelengths you need to remove all light in the visible spectrum since the eye is a 1000 times more sensitive in that region, and then illuminate the scene with a ludicrously bright source to make up for the lack of sensitivity. Not an every day occurance. And for filters, my guess is visible light leaking in still swamps the near IR image.

The human ey can "percieve" waves beyound 750 nM but to be able to
discern the image.........no way in hell. Golly why would we need
to perfect night vision glasses if we could actually see at the 1uM
range?

--
---------------------------
Ken W
Sony DSC-S85
& lots of 35mm and 4x5 in the closet

 

[Parker North]

Thanks for going to the trouble of adding all of this information. I really enjoyed reading it.

Parker

 

[Daniella68313]

Yes me too I really enjoyed reading it. Very interesting.

Thanks for going to the trouble of adding all of this information.
I really enjoyed reading it.

Parker

--
Daniella
http://www.photosig.com/viewuser.php?id=26918
http://www.pbase.com/zylen
C7OO FORUM: http://www.c700uz.com

c7OOuz, Dimage-7, Tcon14tele, C210tele, Cokin-173, Grad-ND, Hoya-red-Intensifier, Hoya R72.

 

[Mee'n'Mac]

Near IR illuminators: These shine a bright light in the 900 nm
range to illuminate the scene and have an imager with response in
this region. Obviously you can't see any further than your light
source (just like a flash light). Since our photo response is so
poor to 900 nm light no one else can see your floodlight and you
remain stealthy. Unless of course they have same googles and they
see your head light. These DO NOT see heat. They simply see the
reflection of the IR illuminator. It is just like shining a flash
light around, except no one else can see your flash light. This is
what the 717 nightshot mode is. If you take a really bright
illuminator into a dark room you can actually see it glow.

This gives me an intriging idea. It's easy to fashion a near-IR flashlight w/LEDs (available @ RadioShack even). People with IR sensitive cameras (D7, S404, ...) could use this setup to take night pictures (albeit monotone) that might look interesting. I'm not to sure as to how effective a "flash" range this setup might have .... maybe I'll give it a try.

 

[PeteGanzel]

Actually I've done what you described. Here's a shot taken with 16 high power 850nm LEDs.



The camera is really not that sensative to IR, It took a 30 second exposure for this shot wide open at ISO 100 (no IR filter). Even though the LEDs consumed the same power that visible LEDs would use. Its not really practical to use IR LEDs for normal exposures.

Yes, there was a very faint glow from the LEDs visible to my eyes if you looked right at them

Good Luck.

Pete

Near IR illuminators: These shine a bright light in the 900 nm
range to illuminate the scene and have an imager with response in
this region. Obviously you can't see any further than your light
source (just like a flash light). Since our photo response is so
poor to 900 nm light no one else can see your floodlight and you
remain stealthy. Unless of course they have same googles and they
see your head light. These DO NOT see heat. They simply see the
reflection of the IR illuminator. It is just like shining a flash
light around, except no one else can see your flash light. This is
what the 717 nightshot mode is. If you take a really bright
illuminator into a dark room you can actually see it glow.

This gives me an intriging idea. It's easy to fashion a near-IR
flashlight w/LEDs (available @ RadioShack even). People with IR
sensitive cameras (D7, S404, ...) could use this setup to take
night pictures (albeit monotone) that might look interesting. I'm
not to sure as to how effective a "flash" range this setup might
have .... maybe I'll give it a try.

 

[Barry L]

There already exists IR illuminators for IR sensitive, monochrome closed circuit television (CCTV) cameras that are used for security purposes. These IR illuminators have ranges from as littles as a few feet to a hundred feet. They are available from companies including Videolarm among others.

Near IR illuminators: These shine a bright light in the 900 nm
range to illuminate the scene and have an imager with response in
this region. Obviously you can't see any further than your light
source (just like a flash light). Since our photo response is so
poor to 900 nm light no one else can see your floodlight and you
remain stealthy. Unless of course they have same googles and they
see your head light. These DO NOT see heat. They simply see the
reflection of the IR illuminator. It is just like shining a flash
light around, except no one else can see your flash light. This is
what the 717 nightshot mode is. If you take a really bright
illuminator into a dark room you can actually see it glow.

This gives me an intriging idea. It's easy to fashion a near-IR
flashlight w/LEDs (available @ RadioShack even). People with IR
sensitive cameras (D7, S404, ...) could use this setup to take
night pictures (albeit monotone) that might look interesting. I'm
not to sure as to how effective a "flash" range this setup might
have .... maybe I'll give it a try.

 

[Mee'n'Mac]

Actually I've done what you described. Here's a shot taken with
16 high power 850nm LEDs.

As usual, somebody's beat me to it Thx for the photo. I wonder how it would compare visually to the more usual way of making an IR photo ?

p.s. - Did "we'all" eventually answer Daniellla's (and other's) questions ?

 

[PeteGanzel]

. I wonder

how it would compare visually to the more usual way of making an IR
photo ?

The appearance is identical to a photo taken with sunlight and an IR filter.
Foliage is recorded as very bright.

A more promising alternative to IR LEDs ( at least with the D-7) is filtered electronic flash;

p.s. - Did "we'all" eventually answer Daniellla's (and other's)

questions ?

Yea you're right, I guess we are pretty far off topic.

Pete

 

[Dr. Don Sandell]

Good lord, so many posts for such an inane subject. Humans can "see" light that ranges from 400 to 750nM. Anyone who thinks we acn see 1000nM is full of crapola. Click the link below....it mirrors the info I was taught in med school. Of course there is a huge range of "normal" or more precisely "WNL" (within normal limits) but the bottom line is folks.....400-750nM. You will need Acrobat to read the reference. Sorry if I have stepped on any toes; but as my old buddy Joe Friday says "just the facts maam, just the facts".

http://faculty-web.at.northwestern.edu/med/fukui/Seeing%20is.pdf

 

[Daniella68313]

Let me see the result if you try it.

Near IR illuminators: These shine a bright light in the 900 nm
range to illuminate the scene and have an imager with response in
this region. Obviously you can't see any further than your light
source (just like a flash light). Since our photo response is so
poor to 900 nm light no one else can see your floodlight and you
remain stealthy. Unless of course they have same googles and they
see your head light. These DO NOT see heat. They simply see the
reflection of the IR illuminator. It is just like shining a flash
light around, except no one else can see your flash light. This is
what the 717 nightshot mode is. If you take a really bright
illuminator into a dark room you can actually see it glow.

This gives me an intriging idea. It's easy to fashion a near-IR
flashlight w/LEDs (available @ RadioShack even). People with IR
sensitive cameras (D7, S404, ...) could use this setup to take
night pictures (albeit monotone) that might look interesting. I'm
not to sure as to how effective a "flash" range this setup might
have .... maybe I'll give it a try.

--
Daniella
http://www.photosig.com/viewuser.php?id=26918
http://www.pbase.com/zylen
C7OO FORUM: http://www.c700uz.com

c7OOuz, Dimage-7, Tcon14tele, C210tele, Cokin-173, Grad-ND, Hoya-red-Intensifier, Hoya R72.

 

[Daniella68313]

Actually I've done what you described. Here's a shot taken with
16 high power 850nm LEDs.

As usual, somebody's beat me to it Thx for the photo. I wonder
how it would compare visually to the more usual way of making an IR
photo ?

p.s. - Did "we'all" eventually answer Daniellla's (and other's)
questions ?

I still have to decifer a good part of it but some did answer my question.

--
Daniella
http://www.photosig.com/viewuser.php?id=26918
http://www.pbase.com/zylen
C7OO FORUM: http://www.c700uz.com

c7OOuz, Dimage-7, Tcon14tele, C210tele, Cokin-173, Grad-ND, Hoya-red-Intensifier, Hoya R72.

 

[Daniella68313]

Good lord, so many posts for such an inane subject. Humans can
"see" light that ranges from 400 to 750nM. Anyone who thinks we
acn see 1000nM is full of crapola. Click the link below....it
mirrors the info I was taught in med school. Of course there is a
huge range of "normal" or more precisely "WNL" (within normal
limits) but the bottom line is folks.....400-750nM. You will need
Acrobat to read the reference. Sorry if I have stepped on any
toes; but as my old buddy Joe Friday says "just the facts maam,
just the facts".

but you did not explain how come I can see the vegetation turn almost white in value when I look through the infrared filter? The sky gets very dark, other obejcts seems to remain about the same. Some trees stay about the same (fir trees) but palm tree seems to glow white (reddish white).

Granted that is not infrared but can you explain what it is?

http://faculty-web.at.northwestern.edu/med/fukui/Seeing%20is.pdf

--
Daniella
http://www.photosig.com/viewuser.php?id=26918
http://www.pbase.com/zylen
C7OO FORUM: http://www.c700uz.com

c7OOuz, Dimage-7, Tcon14tele, C210tele, Cokin-173, Grad-ND, Hoya-red-Intensifier, Hoya R72.

 

[Dr. Don Sandell]

Danny girl,

As I posted before, your changing the color of light entering your pupil. Of course it's going to change your light perception. If you need to further research this.....the library of congress is an excellent site.

 

[Dr. Don Sandell]

Call your Optometrist or Opthomologist and ask him or her. I'm a G.P. and am unable to answer your question accurately. Your friendly local "Eye Guy" will do much better than I (or is that eye......or perhaps me?)

At any rate...........good luck kiddo!

 

[Daniella68313]

well, it all come up to one thing at the end....we can have a good preview of what the scene will look in infrared by just viewing it through the filter with our eyes. I think this would be probably useful for people who don't have EVF or people with DSLR who cannot see the effect of the filter in bright sunlight because the LCD is too hard to see. Good for evaluating how a scene will look and if it is worth setting up the tripod and shooting at that location.

I don't think an eye doctor will be able to tell me those things...this is probably something out of this world for them In any case, I am not ready to pay a 40$ consultation just to have an opinion on this..yike.

Call your Optometrist or Opthomologist and ask him or her. I'm a
G.P. and am unable to answer your question accurately. Your
friendly local "Eye Guy" will do much better than I (or is that
eye......or perhaps me?)

At any rate...........good luck kiddo!

--
Daniella
http://www.photosig.com/viewuser.php?id=26918
http://www.pbase.com/zylen
C7OO FORUM: http://www.c700uz.com

c7OOuz, Dimage-7, Tcon14tele, C210tele, Cokin-173, Grad-ND, Hoya-red-Intensifier, Hoya R72.

 

[Gareth Taylor]

Human vision is adaptable and there is no absolute cut off point, but a gradual loss in perception. The perceived limit varies between individuals and depends on the light source.

Your experiment illustrates the effects of chromatic adaption.

You have shown that by altering the light source (blocking most of the "visible" light) your perception of the scene corresponds with the infrared portion of the spectrum, hence the leaves appear to glow in relation to the other parts of the scene.

Here is a useful link for anyone wanting to learn the science:
http://www.efg2.com/Lab/Library/Color/index.html

My main reference is the Color Science bible "Wyszecki & Stiles" (ISBN 0471399183).

 

[Gareth Taylor]

Infra-red is defined as wavelengths longer than red no longer
perceptible to the human eye, so by definition, we can't.

Yes infra-red is defined as wavelengths longer than red.

No longer perceptible to the human eye? Think again.

There's
nothing intrinsically different about infra-red: it's just
electromagnetic radiation, just light light. The line between red
and infra-red is somewhat arbitrary; I also wouldn't be surprised
if there were significant differences between people.

However, I'm perfectly willing to believe that what you're seeing
is quite real: it would be the very long wavelengths of red light,
at the very edges of human perception. This would very likely cause
similar changes in appearance as "actual" infrared.

Refer to my later post:
http://forums.dpreview.com/forums/read.asp?forum=1024&message=4864467

 

[Gareth Taylor]

To clarify:

Yes infra-red is defined as wavelengths longer than red.

AND shorter than microwaves.