Page 1 of 2 12 LastLast
Results 1 to 10 of 20
  1. #1
    Ioannis's Avatar
    Ioannis Guest

    Default Color Spectra of Common Light sources



    The color spectra page of the most common light sources is now complete.

    The calibration was performed from scratch, using only Mercury as a
    reference. Everything, with the exception of a couple of oddballs, is
    derived from it directly. Some parts may be slightly off, (especially
    towards the purple), because of micro-differences in the focal length of the
    collimator, while taking pictures. From 346-350nm and upwards, the match
    should be pretty good. The actual wavelength calibration is described in
    detail in the "notes" section, and is now as scientifically accurate as
    possible, as there should be no cumulative errors. Only individual errors
    relative to Mercury.

    The table has been re-arranged, and to it 10-15 more photos have been
    added/changed (including spectra of some lamps which are not in existence
    any more, like the original self-ballasted high pressure Mercury and the
    older "improved" high pressure Mercury), for a total of 37, so it now looks
    much nicer and more consistent:

    Note references can be directly jumped onto via html markers, so one can
    navigate comfortably back and forth.

    You are welcome to take a look:

    http://users.forthnet.gr/ath/jgal/sp...ml#colorphotos
    http://users.forthnet.gr/ath/jgal/sp...ici.html#notes

    Enjoy,
    --
    I. N. Galidakis
    http://users.forthnet.gr/ath/jgal/
    Eventually, _everything_ is understandable


  2. #2
    Chris L Peterson's Avatar
    Chris L Peterson Guest

    Default Color Spectra of Common Light sources

    On Sat, 24 Sep 2005 11:01:37 +0300, "Ioannis" <morpheus@olympus.mons>
    wrote:



    Great job, and a very useful reference. Thank you for collecting and
    publishing this information.

    _________________________________________________

    Chris L Peterson
    Cloudbait Observatory
    http://www.cloudbait.com

  3. #3
    Uncle Al's Avatar
    Uncle Al Guest

    Default Color Spectra of Common Light sources

    Ioannis wrote:

    That's a keeper! Finally, something better than ISCO Tables.

    --
    Uncle Al
    http://www.mazepath.com/uncleal/
    (Toxic URL! Unsafe for children and most mammals)
    http://www.mazepath.com/uncleal/qz.pdf

  4. #4
    The Ghost In The Machine's Avatar
    The Ghost In The Machine Guest

    Default Color Spectra of Common Light sources

    In sci.physics, Chris L Peterson
    <clp@alumni.caltech.edu>
    wrote
    on Sat, 24 Sep 2005 13:32:43 GMT
    <o3laj15ha88og6ana95ggo2hn61efe31gv@4ax.com>:

    The "mile markers" (OK, nanometer markers) are a nice touch. :-)

    --
    #191, ewill3@earthlink.net
    It's still legal to go .sigless.

  5. #5
    Marvin's Avatar
    Marvin Guest

    Default Color Spectra of Common Light sources

    Ioannis wrote:

    There are some details that indicate artifacts. The one that "jumped out" at me is in the
    spectrum of the high-pressure sodium lamp. Your note mentions the self-absorption in the
    yellow, but why does the space between the two yellow areas look red? Is it perhaps only
    seen that way on my monitor? If it is really in your image, it may be from scattered
    light. Maybe I'm being too fussy for the purposes you have in mind for the images.

  6. #6
    Ioannis's Avatar
    Ioannis Guest

    Default Color Spectra of Common Light sources

    "Marvin" <physchem@cloud9.net> wrote in message
    news:11jbg8n6t1uujbb@corp.supernews.com...
    [snip]
    at me is in the
    self-absorption in the
    it perhaps only
    from scattered

    The High Pressure Sodium lamp spectrum is one of the hardest to photograph.
    Reason being that the intensity of the wings of the self-absorption around
    the D line, is on the order of tens of thousands times higher than the rest
    of the Sodium lines.

    This necessitates some compromise between exposure time and stray light. If
    the exposure is lowered to the point where the absorption looks completely
    black, then one misses the rest of the lines. If one wants the rest of the
    broadened lines, one has to overexpose the D absorption wings, some.

    The necessity of this compromise is shown on the previous spectrum, #21,
    where in order to show the rest of the sodium lines, I overexposed the D
    line, which has not completely self-absorbed yet.

    An exposure that shows black between the two absorption wings more clearly,
    is the 3rd photo shown below:

    http://users.forthnet.gr/ath/jgal/spectroscope/Na.html

    Note however how this photo completely misses the rest of the lines.

    A more accurate black and white picture, taken with "the monster", is shown
    on the above (last photo) link and on the following link, where the details
    of this area are shown clearly.

    http://users.forthnet.gr/ath/jgal/sp...bsorption.html

    The absorption area is not completely black anyway, because the Sodium
    discharge tube radiates thermally at about 1,200 C. The overexposure
    captures this incadescence, so brown/red is pretty much correct.

    It's really hard to make it better, unless I suppressed the rest of the
    emissions, exposure-wise. #22 was the best balance/effort from 7 attempts.

    images.
    --
    I. N. Galidakis
    http://ioannis.virtualcomposer2000.com/
    Eventually, _everything_ is understandable


  7. #7
    Marvin's Avatar
    Marvin Guest

    Default Color Spectra of Common Light sources

    Ioannis wrote:

    Good explanation, and good data to back it up. I guess the only way you could have shown
    cleaner spectra would be to combine several exposures. Some electronic sensors capture a
    much broader range of intensities than does film, but even then you would have trouble
    displaying the results as an image. There have also been multilayer B/W films in which
    each layer has a different sensitivity range.

  8. #8
    Ioannis's Avatar
    Ioannis Guest

    Default Color Spectra of Common Light sources

    "Marvin" <physchem@cloud9.net>
    news:11jdr9bbjnd9d24@corp.supernews.com...
    [snip]

    photograph.
    around
    rest
    If
    completely
    the
    clearly,
    shown
    details
    attempts.
    could have shown
    sensors capture a
    have trouble
    films in which

    Correct. If I did any of that however, I don't think the data would be
    accurate. Provided that the camera has a response which is close to that of
    the human eye, one could conceivably extract the spectral distribution curve
    of the source from its color spectrum photo, either by doing an inverse
    Fourier on a horizontal line, or simply by tracing a horizontal line and
    looking at the RGB/brightness values of the traced pixels.

    If the photographs were composites from films with different response
    curves, the spectral distribution would contain additional discontinuities
    or will be distorted, things which don't show on the original, but can still
    betray the original's "fakeness". I think that in this case the extracted
    curve won't match the curves published by the big companies.

    Btw, I have also added one more spectrum, that of a typical American Metal
    Halide lamp. This kind of Metal Halide is quite rare in Europe. Fortunately,
    I foresaw the need when I was there 13 years ago and grabbed one. (Actually
    I grabbed 3, but anyway :-)

    The order of the spectra passed #16 has changed. last update: 25/9/2005,
    10:00pm.
    --
    I. N. Galidakis
    http://ioannis.virtualcomposer2000.com/
    Eventually, _everything_ is understandable


  9. #9
    Autymn D. C.'s Avatar
    Autymn D. C. Guest

    Default Color Spectra of Common Light sources

    Thanks for prettying knowledge. But you didn't answer my email about
    the diode laser. And substances are not capitalised.


  10. #10
    Autymn D. C.'s Avatar
    Autymn D. C. Guest

    Default Color Spectra of Common Light sources

    UU, UU, can you get a curve for various flames? candle, match, propane,
    alcohol?

    -Aut


 

 
Page 1 of 2 12 LastLast

Similar Threads

  1. How much will domestic light sources interfere with photos?
    By HeXploiT in forum Astrophotography Forum
    Replies: 3
    Last Post: 02-15-2010, 12:26 PM
  2. Replies: 0
    Last Post: 05-23-2007, 07:20 PM
  3. Color spectra sections taken with a large spectroscope
    By Ioannis in forum Amateur Astronomy Forum
    Replies: 0
    Last Post: 12-05-2005, 05:20 PM
  4. Sometimes, light pollution sources can look good...
    By Rich in forum Amateur Astronomy Forum
    Replies: 10
    Last Post: 10-25-2005, 11:26 AM
  5. Sources of Light Pollution
    By Tony Flanders in forum Amateur Astronomy Forum
    Replies: 40
    Last Post: 10-20-2003, 04:25 AM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  
Powered by vBulletin Version 4.2.0
Powered by vBulletin
All times are GMT. The time now is 08:14 AM.