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D2H - more on IR noise

  • Thread starter Thread starter edbetz
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Bjorn, please have a look at the image of transmitting IR diode from TV remote. You will see blue channel pixels also involved. Blue filter seems to allow IR to get through.

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I just did a search in all the forus and came up with nothing.. Do you have any links to thread discussing it?

Cheers

peter
Iliah Borg said:
Peter Dove said:
The output from DCDraw is incredible! How the heck was this hidden
away from me!
Click to expand...
For the last year we pointed to it here many times. The wonderful
thing about it is that it is available in source.

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no text
Click to expand...
 
The truth is, I really can't tell you from a scientific perspective what exactly is going on here. I can't tell you, YET, if there is any difference with how the D2H responds from other Nikon digital cameras or any other digital cameras.

I can tell you that the hot mirror filter, which doesn't cost me even 1/10 of an f-stop, seems to render a more accurate image in terms of color and the images seem sharper. There is some technical reason for this, what it is, I just don't know, but much of it has been explained here in this thread.

I don't imagine that a flash tube will reflect the same color shift as did my single 60 watt light bulb (would the brand help? or do I need someone to perform a complete spectrographic analysis of the light for this un-scientific test to have any validity)

:-)

So, for now, and until I find a reason not to, I'm leaving my hot mirror filter on the camera.

Heck, it protects the front element anyway and it doesn't seem to effect my exposure even 1/20 of a stop.

So, while my tests arn't controled enough for some of you,

I know what I see. I know what the images show.

You can see them for yourself.

-Ed
Iliah Borg said:
Bjorn, please have a look at the image of transmitting IR diode
from TV remote. You will see blue channel pixels also involved.
Blue filter seems to allow IR to get through.

--
no text
Click to expand...
--
Ed Betz
http://www.edbetz.com
 
Can I mention that I'm not saying this is a defect in the D2H!
I'm not saying it is even worse then any other digital camera.

It is, more over, just an observation. I noticed it when shooting a job. I spent several days and many hours trying to duplicate it.

I then tried to figure out how to prevent it.

Then I shared all of that work with you all here.

I hoped that some others might find it useful and even help explain to me what is going on.

Thats all.

If you don't find it helpful, I'm sorry, I was only trying to be helpful.

I'm sure if I bring these pants and tie out into a bright sunny day, they'll look fine. I, however, don't always shoot on bright sunny days, but thats just me.

Showing a photo without an issue is really nice, but, how helpful is it?

If I did this test (as many others I've done and not posted) and I didn't see a color shift and everything was fine, I wouldn't have posted it - it would just take up space.

-Ed
Bjorn Rorslett said:
your setup is not precisely enough defined to allow us to
understand what's going on here. One example: The IR content of
the light source, what is it? Another: it is a fact that IR
radiation triggers red pixels in D2H (as well as in most other
Nikon DSLRs used by me). So, your sample image purporting to
indicate IR "noise" should show this noise in reddish, not blueish
hues, if it were real. Also, it is a fact D2H is much less
sensitive to IR than other Nikon DSLRs, have you repeated your test
with cameras other than D2H?

A further problem here is that we are not shown the transmission
curve of the hot mirror filter itself, which may well begin to cut
already in the blue region of the spectrum. The non-hot mirror
sample for example might show some added UV-mediated fluorescence
(remember, clothes are not inactive reflectors of light, the cloth
itself may be treated with chemicals altering its spectral
reflectance). if the hot-mirror influenced deep blue, it would also
reduce any fluorescence-related effects on the image.

I'm going to do a more rigorous test with a known light source
(electron flash with Xenon tube), and a set of hot mirror and IR
filters with known
transmission, and do this with a test subject more appropriate to
the issue. I'll report my findings on a later occasion.
Click to expand...
--
Ed Betz
http://www.edbetz.com
 
Relax Ed, we know - we dont think your camera bashing - I for one find your tests and solutions very interesting and your use of so much digital stuff before brings a keen eye for detail and variations to the table.

Keep it up - I love the work you are doing - after all it can only benefit me when mine arrives!

Peter
 
I really get the feeling that some people think I'm a troll, just here to stir up the Nikon SLR forum or bash the D2H. Neither is trus,
Thanks for the support,

Ed
Peter Dove said:
Relax Ed, we know - we dont think your camera bashing - I for one
find your tests and solutions very interesting and your use of so
much digital stuff before brings a keen eye for detail and
variations to the table.

Keep it up - I love the work you are doing - after all it can only
benefit me when mine arrives!

Peter
Click to expand...
--
Ed Betz
http://www.edbetz.com
 
Peter Dove said:
Relax Ed, we know - we dont think your camera bashing - I for one
find your tests and solutions very interesting and your use of so
much digital stuff before brings a keen eye for detail and
variations to the table.

Keep it up - I love the work you are doing - after all it can only
benefit me when mine arrives!
Click to expand...
Same here.

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no text
 
Ed, first let me jump on the "Ed is a good guy" band wagon. To be truthful, I wondered a bit at your very first post, but after a few replies I could certainly understand your frustration. Since then you have been:

1. Persitent
2. Thoughtful
3. Helpful
4. On the Bleeding Edge of pushing the limits
5. Cheerful, thrify and kind :-) ( old Boy Scout days come through )

Far too many people don't bother to actually read a whole message, or better yet the whole thread, before jumping. My guess is that in this thread you have stated at least a dozen times that what you are working, and testing, are extreme cases that most will never even see.

Hang in there, the folks that appreciate what you are doing far outnumber the "Ed Bashers", we may just not be as vocal :-).

If you ever find yourself out my way, drop by, I owe you at least a drink or two of your favorite beverage for the work you have done.

Thanks,
EdwardBetz said:
Ed
Peter Dove said:
Relax Ed, we know - we dont think your camera bashing - I for one
find your tests and solutions very interesting and your use of so
much digital stuff before brings a keen eye for detail and
variations to the table.

Keep it up - I love the work you are doing - after all it can only
benefit me when mine arrives!

Peter
Click to expand...
--
Ed Betz
http://www.edbetz.com
Click to expand...
--
Bill Dewey
http://www.deweydrive.com
 
Peter Dove said:
Do you have any links to any reviews of DCDraw at all - it seems a
very interesting tool.
Click to expand...
Peter, it is DCRaw!!! :)) - stands for "Digital Camera RAW", has nothing 2 do with drawing.

Why would you need a review? The tool is pretty much self-explained. If you want, download the C file, and search for reviews on interpolation methods used, they are clearly stated in the text, as well as format details.

E-mail David, if you need more detail. His contact info is at http://www.cybercom.net/~dcoffin/resume.html

All hidden border pixels used for noise reduction and sensor characterisation are just passed to DCRaw output as well, but not applied to the image.

Other than interpolation, it is just an interpreter, and the fact that Adobe used it shows that it is a good format hack. Apply dcraw, than use ImageMagick to raise gamma (.8/2.2 should be good initial approximation), assign camera profile and convert to working space - and that's it, all from command line, works perfectly on UNIX as well, batch mode.

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no text
 
and I don't even own a D2H 8^). Nor will I own one in the near future (alas I am an amateur, don't earn any money with my photography and will have to be happy with the D100 for quite some time to come). But, you have me intrigued about IR "interfering" with CCD capture, just as UV used to "interfere" with film. I find your test results to be very compelling and I have learned much from this thread.

Threads like this is the whole reason that I frequent this forum, to LEARN and to give back to others when I can.

Thanks again Ed,
Mike Berube

--
  • It's all about the pictures -
(PBase Supporter)
http://www.pbase.com/mikeb2002
 
Chris101 said:
Hey! I used to work on spectrometers with John Talbot back in the
sci.astro days!

This information isn't really pertainent though, because tungsten
lighting is not made by tungsten atomic emission, but rather a
tungsten wire is heated to a very high temperature until it glows
in a continous spectrum.
Click to expand...
Continuous? How can the atom radiate outside it's emmission frequencies? Tungsten does have emmission lines in the visible (according to the link I provided in the previous post some 96 frequencies) they just are distributed in a very bimodal pattern across the visible spectrum, this bimodality (in combination with illuminated materials that are more likely to reflect UV or IR light) is why I think images illuminated under such lights tend to be noisier(in blue channel) than under other forms of illumination. Thanks to quantum mechanics, the frequencies of emmitted photos are specific in frequency. The valence electrons around the sodium atoms in the filament are knocked into highier orbitals and then decay by fixed characteristic energy levels (depending on the total energy of the colliding electrons) to release light, they release it in a characteristic set of frequencies, it can not be continuous. I'd be interested in reading anything you might have that shows that it is.
Chris101 said:
The line spectrum is for the emission of
excited atoms of tungsten. The peak wavelength of a tungsten
filiment is indeed in the IR, but it also has a lot of visible
light, especially at the longer wavelength end of the spectrum.
Click to expand...
Only about 12% (in the best incadescent bulbs) of the energy of excitation is converted to visible light at the 2800 degrees celcius that a filament is optimally radiating at (to produce that visible light)..the largest contribution of emmitted radiation > 85% in most filaments, is in the form of IR light that can't be seen.
Chris101 said:
Tungsten illumination has very little ultraviolet.
Click to expand...
Agreed, I was just noting the proximity of the emmission lines toward the blue (visible) and red(visible) ends, not UV (which is invisible to human eyes) but visible colors near it.

A very instructive set of links below, describing in detail classical as well as quantum descriptions for electromagnetic energy (light) including emmission and absorption spectra.

http://www.colorado.edu/physics/2000/quantumzone/index.html
http://www.colorado.edu/physics/2000/quantumzone/bohr2.html
http://www.colorado.edu/physics/2000/quantumzone/lines2.html

Regards,
--

 
Bjorn Rorslett said:
your setup is not precisely enough defined to allow us to
understand what's going on here. One example: The IR content of
the light source, what is it? Another: it is a fact that IR
radiation triggers red pixels in D2H (as well as in most other
Nikon DSLRs used by me). So, your sample image purporting to
indicate IR "noise" should show this noise in reddish, not blueish
hues, if it were real. Also, it is a fact D2H is much less
sensitive to IR than other Nikon DSLRs, have you repeated your test
with cameras other than D2H?

A further problem here is that we are not shown the transmission
curve of the hot mirror filter itself, which may well begin to cut
already in the blue region of the spectrum. The non-hot mirror
sample for example might show some added UV-mediated fluorescence
(remember, clothes are not inactive reflectors of light, the cloth
itself may be treated with chemicals altering its spectral
reflectance). if the hot-mirror influenced deep blue, it would also
reduce any fluorescence-related effects on the image.

I'm going to do a more rigorous test with a known light source
(electron flash with Xenon tube), and a set of hot mirror and IR
filters with known
transmission, and do this with a test subject more appropriate to
the issue. I'll report my findings on a later occasion.
Click to expand...
I've shot two shot of a black T-shirt plus a GretagMacBeth colour checker with my D2H, one with and one without a Tiffen Hot-Mirror Filter. Light Source is a 60 W incandescent lamp and as you can see from these pictures, there is absolute no difference whatsoever between them. Pay special attention to the histograms from Capture 4 which are essentially identical.

This is without Hot-Mirror:
http://www.naturfotograf.com/D2H \without.jpg

and this is with:

http://www.naturfotograf.com/D2H \hotmirror.jpg

Thus, I cannot very the existence of "IR noise" as claimed to exist by others.
 
Bjorn Rorslett said:
Bjorn Rorslett said:
your setup is not precisely enough defined to allow us to
understand what's going on here. One example: The IR content of
the light source, what is it? Another: it is a fact that IR
radiation triggers red pixels in D2H (as well as in most other
Nikon DSLRs used by me). So, your sample image purporting to
indicate IR "noise" should show this noise in reddish, not blueish
hues, if it were real. Also, it is a fact D2H is much less
sensitive to IR than other Nikon DSLRs, have you repeated your test
with cameras other than D2H?

A further problem here is that we are not shown the transmission
curve of the hot mirror filter itself, which may well begin to cut
already in the blue region of the spectrum. The non-hot mirror
sample for example might show some added UV-mediated fluorescence
(remember, clothes are not inactive reflectors of light, the cloth
itself may be treated with chemicals altering its spectral
reflectance). if the hot-mirror influenced deep blue, it would also
reduce any fluorescence-related effects on the image.

I'm going to do a more rigorous test with a known light source
(electron flash with Xenon tube), and a set of hot mirror and IR
filters with known
transmission, and do this with a test subject more appropriate to
the issue. I'll report my findings on a later occasion.
Click to expand...
I've shot two shot of a black T-shirt plus a GretagMacBeth colour
checker with my D2H, one with and one without a Tiffen Hot-Mirror
Filter. Light Source is a 60 W incandescent lamp and as you can
see from these pictures, there is absolute no difference whatsoever
between them. Pay special attention to the histograms from Capture
4 which are essentially identical.

This is without Hot-Mirror:



and this is with:



Thus, I cannot very the existence of "IR noise" as claimed to exist
by others.
Click to expand...
Thanks, Bjorn. Please edit the links.
--
no text
 
Iliah Borg said:
Bjorn Rorslett said:
Bjorn Rorslett said:
your setup is not precisely enough defined to allow us to
understand what's going on here. One example: The IR content of
the light source, what is it? Another: it is a fact that IR
radiation triggers red pixels in D2H (as well as in most other
Nikon DSLRs used by me). So, your sample image purporting to
indicate IR "noise" should show this noise in reddish, not blueish
hues, if it were real. Also, it is a fact D2H is much less
sensitive to IR than other Nikon DSLRs, have you repeated your test
with cameras other than D2H?

A further problem here is that we are not shown the transmission
curve of the hot mirror filter itself, which may well begin to cut
already in the blue region of the spectrum. The non-hot mirror
sample for example might show some added UV-mediated fluorescence
(remember, clothes are not inactive reflectors of light, the cloth
itself may be treated with chemicals altering its spectral
reflectance). if the hot-mirror influenced deep blue, it would also
reduce any fluorescence-related effects on the image.

I'm going to do a more rigorous test with a known light source
(electron flash with Xenon tube), and a set of hot mirror and IR
filters with known
transmission, and do this with a test subject more appropriate to
the issue. I'll report my findings on a later occasion.
Click to expand...
I've shot two shot of a black T-shirt plus a GretagMacBeth colour
checker with my D2H, one with and one without a Tiffen Hot-Mirror
Filter. Light Source is a 60 W incandescent lamp and as you can
see from these pictures, there is absolute no difference whatsoever
between them. Pay special attention to the histograms from Capture
4 which are essentially identical.

This is without Hot-Mirror:



and this is with:



Thus, I cannot very the existence of "IR noise" as claimed to exist
by others.
Click to expand...
Thanks, Bjorn. Please edit the links.
Click to expand...
Strange, my Mozilla showed them without problem. But for the benefit of non-Mozilla people, I've uploaded new versions with simpler URLs.
 
Anthony Medici said:
Have you tried to take a picture of a TV remote control beam as a
way to tell if the camera is susceptible to that range of light?

It seems to me that these were taken at higher ISO values...
Bjorn Rorslett said:
Thus, I cannot very the existence of "IR noise" as claimed to exist
by others.
Click to expand...
Click to expand...
shot as 200 ISO, just see the EXIF info displayed with the images. Also, note I simply display a screenshot to get all info plus the histogram with the image, so don't hold that as an evidence for "graininess". The major point here was to see whether or not repeating the test setup claimed to generate "IR noise" in fact did so, which I could NOT verify.
 
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