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It was moved to "Sodium vapour lamp" earlier today for no reason. Dbenbenn 16:24, 21 Dec 2004 (UTC)


I included the LPS abbreviation as well as there was no mention of it. Google: "LPS sodium lamp" gives 4750 hits, "SOX sodium lamp" gives 812. (apart from this, i dont know which one is more popular or if one term is being phased out) || deanos 11:24, Nov 16, 2004 (UTC)

I've stated that the near-monochromatic yellow light is actually two wavelengths very close together. There are other doublets of different colours as well, but much fainter. I've rewritten the bit that previously referred to Colour Rendering (which is about light sources, not objects). JohnG62 21:02, 13 October 2007 (UTC)

Name changeEdit


Generaly speaking, I think the Wiki style is to leave differences in British/American spelling alone and it is definitely recommended style that the spelling at least be consistent throughout the article. I note that even though you moved the page to "Sodium Vapour Lamp", you didn't fix the first mention of "vapor" in the article. By the way, did you fix all the hyperlinks that link to this article?

I'd like to suggest that we undo the move and put the article back where it was, at "Sodium Vapor Lamp".

Atlant 13:55, 21 Dec 2004 (UTC)

Um, what? I didn't move the article. I agree that it shouldn't have been moved. Dbenbenn 15:58, 21 Dec 2004 (UTC)
According to [deleted page], it was moved by MPF. Dbenbenn 16:00, 21 Dec 2004 (UTC)
Alright, I tried to move Sodium vapor lamp out of the way so as to move Sodium vapour lamp back. That was the wrong thing to do. Oops. Dbenbenn 16:40, 21 Dec 2004 (UTC)
I apologize for attributing the move to you (but I'm glad you agree the move was wrong :) )
Atlant 17:17, 21 Dec 2004 (UTC)
I moved it back. Gentgeen 17:46, 21 Dec 2004 (UTC)

Small data additionsEdit

If the sky is clear, the light is simply irradiated around, causing large enough cities to actually glow with an orange light!

If you've approached a large enough city, usually with 1 million people inside or more, in a clear night, chances are that, when you're about 50 km away, you could see a dim, dome-shaped orange glow where the city is; this is particularly noticeable with cities that grow out instead of growing up like Guadalajara. Da_Nuke 05:55, 19 January 2006 (UTC)

Text temporarily removedEdit

I removed this sentence

"In Germany HPS lamps are not allowed for use on roads. New Australian roadway lighting criteria requires HPS lamp lumens be reduced by .75 for roadway lighting designs."

only because it needs to be fixed. Why are HPS lamps not allowed in Germany? In Australia, HPS lamp lumens must be reduced to 75% of what? and why? Is it 75% or 0.75 lumens? PAR 14:12, 19 January 2006 (UTC)


It is common to come across acronyms like SON-E and SON-T. I have also seen NES-E, NAV-E, NAV-T. I am new to this fascinating business of luminaires, and only know that E=elliptical and T=tubular (basically the shape of the luminaires, per se). Does anybody has a clue what SON stands for?

I suspect SOdium or Sodium Oxide something...
I would think it would be "Sodium Nitride", but that is a newly discovered compound from what I see. "Sodium Oxide Nitride" I could not find anything on. "Sodium Nickel" seems to be more involved with batteries, but since the nickel is used to make electrodes, ( then maybe that is what it has to do with. Eric B 15:42, 27 March 2007 (UTC)
OK, I decided to ask this question at Candlepower Forums (where I first asked about the White Son was was taold about it), and I was told that SOX does not even stand for Sodium OXide, so the article is wrong on that point. The person didn;t know what SON stood for either, but pointed out it was apart of a naming system introduced with the first two-piece low pressure sodium lamps in 1932 (SO or SO/H). the first One piece in 1955 was then SOI. SL and SLI was the linear lamps. He linked to as his source of information; but I haven't found these specific details there yet.Eric B 16:57, 14 April 2007 (UTC)
I came to ask the same thing, my guess is Sodium Oxide-Neon. Yes: SON-E is elliptical (bulbous), and SON-T is tubular. Interesting photos here --Belg4mit 19:43, 30 April 2007 (UTC)

Image persistently removedEdit

goes here for the mean time! 06:47, 11 February 2006 (UTC)

Discontinuuous spectrumEdit

The article currently states that "These lamps produce continuous spectrum light (not monochromatic)." All gas discharge lamps (fluorescent and HID) are polychromatic, but all also produce discontinouous (line) spectra (unlike incandescent lamps, including halogen, which produce continouous spectra). This is clearly illustrated by a standard spectral power distribution graph. Chondrite 23:48, 6 August 2006 (UTC)

Line spectra are not discontinuous. Even the narrowest line has a non-zero width. They just tend to be narrow, but the HPS lamp sodium D-line is very broad, hundreds of angstroms, and is not even close to discontinuous. PAR 02:27, 7 August 2006 (UTC)
The individual lines within the spectral output are continuous, but HPS has multiple discrete spectral lines, which are discontinuous. "The sodium D-line is the main source of light from the HPS lamp, and it is extremely pressure broadened by the high sodium pressures in the lamp, hence colors of objects under them can be distinguished. " The spectral output of low-pressure sodium is also dominated by the sodium D line, but has very low CRI. The enhancement of CRI in HPS is only partially due to the pressure-broadening of the sodium D-line, but is much more related to the addition of non-sodium elements to the arc tube. Chondrite 06:40, 7 August 2006 (UTC)
  • Every physical spectral line is continuous. There is no such thing as a discontinuous line. A discontinuous line would have zero width. Every physical spectral line has a finite width.
  • The only non-sodium elements in an HPS lamp are mercury and xenon. Neither of these two elements contribute anywhere near the amount of CRI that the broadening of the sodium D line does.
PAR 12:21, 7 August 2006 (UTC)
I think you're being perfectly ridiculous. You know as well as anyone that he's talking about the spectrum as a whole as being discontinuous. That is a completele valid statement. A continuous spectrum light source is typically an incandescent source. Just because a Na lamp has broadened emission lines which themselves are continuous (and they aren't even! b/c of self absorption) doesn't meant the entire spectrum can rightly be called "continuous".--Deglr6328 07:55, 20 October 2006 (UTC)
Yes, I know what he's talking about, but I have always heard it referred to as a "line spectrum" as opposed to a "continuum spectrum", not a "continuous" versus "discontinuous". I object to it on the basis of experience and mathematics. Perhaps this nomenclature is used in a field in which I have no experience, but if its just an invention, then it shouldn't be used. PAR 16:39, 20 October 2006 (UTC)

removal of imageEdit

Dicklyon just removed the image I added to this page months ago, claiming it was a "tinted sillhouette". Actually, the photo is a color photo taken under sodium vapor illumination and the fact that it shows up as a tinted sillhouette illustrates how NA vapor lamps generate essentially monochromatic views. I think the image should be restored. What do other people think? Debivort 02:38, 21 January 2007 (UTC)

I took it out because there's nothing in the picture that would be expected show a color difference in broad-spectrum light, and hence it fails to make the claimed point. Dicklyon 04:19, 21 January 2007 (UTC)
The background would have been multicolored (brick and cement and grass) but I suppose, since you'd have to take my word for that, the image is less than ideal. Debivort 06:56, 21 January 2007 (UTC)
Exactly. What I belive is irrelevant; if there's nothing visible in the background, the image fails to make its point. And the branches in the foreground are a complete distraction from the point, since they're unlighted. Dicklyon 07:33, 21 January 2007 (UTC)
Of course, the image does illustrate a monochromatic view (regardless of whether the monochromaticity is due to the lamp or not) and it could be argued that without a replacement image, all you've done is reduce the total information on the page. Are you intending to find a replacement, or should I be on the look out for a better shot? Debivort 09:13, 21 January 2007 (UTC)

The information about HPS color rendition is wrong. HPS lighting has a CRI of 22, which is very poor on a 1-100 scale. This information comes from my lighting texbook called Designing a Quality Lighting Environment, by Susan M. Winchip. Blue414 21:43, 15 February 2007 (UTC)

Ariel PhotoEdit

It would be great to have an areal photo showing a suburb lit by sodium-vapor lamps. —Ben FrantzDale (talk) 17:37, 27 January 2008 (UTC)


fixed a degree kelvin reference. no degree symbol is necessary for K —Preceding unsigned comment added by (talk) 20:02, 7 July 2008 (UTC)

Myth re cyclingEdit

I'd hate to tell you how long i believed that Lucalox lamps incorporated a sensor and control circuit that, late in life, detected some run-away condition like overheating, and shut them down to recuperate for an appropriate time, thereby providing a higher average-lifetime-total of hours of illumination compared to, say, dusk-to-dawn operation! I'll go away quietly, but is this a private myth, or is there a verifiable and notable public one that we should consider acknowledging (tho debunking) in the article?
--Jerzyt 04:17, 7 August 2008 (UTC)


According to [1], low pressure sodium SOX lamps have a layer of metal oxide semiconductor film to reflect IR, so SOX lamps do contain some oxygen. Totsugeki (talk) 11:55, 14 January 2010 (UTC)

Paragraph on Scotopic Lighting CalculationsEdit

The paragraph has good (unsourced) information, but does it belong in this article? I moved it here for the time being. Totsugeki (talk) 17:31, 14 January 2010 (UTC)

It is important to understand that photopic lighting calculations alone are obsolete for nighttime lighting applications. Colour previously had not been properly considered in nighttime lighting calculations. Human vision shifts towards a blue green sensitivity at nighttime and under conditions of 50 lux and lower. This is known as the Purkyně shift, identified by Jan Evangelista Purkyně in 1842. Many countries now require scotopic/photopic (S/P) lighting calculations, which represent a greater degree of lighting calculation accuracy known as mesopic lighting calculations. Such calculations are essential to improve accuracy of lighting calculations for roads. For most all applications, luminaires with white light sources are more effective than those that use HPS or LPS lamps. New mesopic lighting calculation standards will soon be released by the CIE, the International Commission on Illumination.

On ballastsEdit

The page currently says: "Because the lamp effectively extinguishes at each zero-current point in the AC cycle, the inductive ballast assists in the reignition by providing a voltage spike at the zero-current point." This is simply false: the ballast only causes a phase shift in the current -- it still passes zero as usual. Maybe someone misunderstood this for the voltage spikes used to actually start the lamp.

-- (talk) 09:20, 13 March 2011 (UTC)

"most efficient electrically powered light source"Edit

I believe that this statement is now or at least will be outdated. Yellow LEDs certainly can be more efficient. David R. Ingham (talk) 04:43, 1 November 2011 (UTC)

You know what to do. Cite it and write it. --Wtshymanski (talk) 14:01, 1 November 2011 (UTC)
Not yet. LED records are achieved via single pulse or super-cooling, or both. Real-life, practical LED sources are in the range of 50-100lm/W, compared to 150-200lm/W figure for real life LPS lamps. (Teoretical LED limit is 683 lm/W for green light.)Agent L (talk) 07:18, 13 July 2012 (UTC)
Agreed with the OP - we need citations for the "the most efficient electrical light sources" claims. I was astonished that this article never mentions lumens or watts given the "the most efficient electrical light sources" claim in the lead.
My impression is that sodium-vapor lamps use less power per lumen than LED but as the LED lamps last longer municipalities prefer them as the LEDs need to be replaced less often meaning fewer truck rolls. LED technology is improving though. For example, the reason I came to this article was that I was reading Bay Bridge: Cutting edge LED lights create unique night landscape which talks about how they initially needed three foot diameter light poles to give them enough lamps for coverage of the roadway. Five years into the design process LEDs had improved that they built the bridge with 16 inch diameter poles. I was reading along and saw "Much more efficient. A 650-watt LED delivers the same illumination as a 1600-watt conventional bulb." It was not clear from the context if "conventional" meant sodium-vapor or incandescent lamp technology and so I came to this article. --Marc Kupper|talk 18:02, 6 September 2013 (UTC)

British English?Edit

What variety of English is this article going to use? There is a mixture now. I don't see any reason that one variety is more appropriate for the topic so let's just decide and fix it. Is there any reason not to use British English? Jojalozzo 15:23, 9 December 2011 (UTC)

See the title? Vapor, not vapour. Leave out the extra U's. American English. --Wtshymanski (talk) 15:27, 9 December 2011 (UTC)
I see! Thanks! Jojalozzo 16:23, 9 December 2011 (UTC)

Sodium High Pressure Lamp SpectrumEdit

The wavelength scale on the image, High_Pressure_Sodium_Lamp_Spectrum.jpg, does not agree with other published high pressure sodium lamp spectra[1--2]. The scale (given in nanometers) needs to be verified. I have contacted the originator of the file to point out the discrepancies.

[1] See sodium lamp spectra at

[2] W. C. Louden and K. Schmidt, "High Pressure Sodium Discharge Arc Lamps", paper presented at the National Technical Conference of the Illuminating Engineering Society, August 29--Sep 2, 1965, New York, NY. — Preceding unsigned comment added by Km45620 (talkcontribs) 14:27, 16 December 2013 (UTC)

Comparing the wikipedia spectrum, High_Pressure_Sodium_Lamp_Spectrum.jpg, here referred to as S1, with ref. [1] above (referred to as S2), and referencing the published sodium lines in the NIST Atomic Spectral Database [3], the following features in S1 map to the corresponding features in S2, which have the same wavelengths in the NIST database for neutral sodium atom (Na I) spectral lines [3]:
S1 Feature (nm) → S2 Feature (nm)
428 → 467
470 → 498
493 → 515
565 → 569
633 → 616
[3] NIST Atomic Spectral Database,

Km45620 (talk) 02:45, 20 December 2013 (UTC)

Low pression & high pressionEdit

Why not to give number to explain what is low pressure and high pressure? — Preceding unsigned comment added by (talk) 17:20, 26 August 2015 (UTC)

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There's no history!!! Why? If I were an engineer looking for info on how these things worked, great article. But as a general reader, who seems to recall that these became ubiquitous starting in the 1990s, replacing earlier lamps that had a blue-purple glow, the article leaves me high and dry. When did these first appear? When did they start to push out the earlier street lamps? If anyone has information, please add a brief history section. Important question: why did they replace the earlier lamps? Theonemacduff (talk) 17:46, 18 September 2019 (UTC)

Return to "Sodium-vapor lamp" page.