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What color is the peak of the dark-adapted eye?

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The article mentions that the dark-adapted eye is most sensitive to green light. As of August 12 2007, this is a revert from a previous edit which said the dark-adapted eye is most sensitive to "blue-green" light.

Here is some research to support the use of "green" over "blue-green".

First, the dark-adapted eye (scotopic vision) is most sensitive to 507 nm light. Compare with the light-adapted eye (photopic vision) which is most sensitive to 555 nm light. References: http://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionintro.html (second paragraph after graphic of "Microscopic Anatomy of the Retina") and the "Luminous Efficiency" chart at http://hyperphysics.phy-astr.gsu.edu/hbase/vision/bright.html.

So what color is 507 nm? Obviously, color is perceptual, but here are some references giving ranges.

- The Wikipedia article "Color" has a chart showing blue at about 450-490 nm, and green at about 490-560 nm.

- In the same article, a CIE 1931 color space chromaticity diagram shows wavelength around the outer edge of the curve. Cyan (evenly mixed blue-green) is at about 492 nm, while 507 nm is clearly in the green section.

- The Wikipedia article "Visible spectrum" has a chart showing blue at 450-495 nm, and green at 495-570.

For these three references, 507 is within the green region and is not "on the border" at around 490 or 495.

A few years ago, I did a website which included laser wavelength tables. I used an online wavelength-to-RGB conversion calculator so that the on-screen colors for visible lasers would match (within obvious limits of equipment, calibration, etc.) the laser wavelengths. The resulting table is at http://www.lexellaser.com/techinfo_wavelengths.htm. Note that Argon at 501.7 nm is clearly green, not blue-green such as argon 496 or 488. This would mean that 507 nm would be even closer to a "pure" green.

(Unfortunately, I cannot now find the online wavelength-to-RGB calculator that I used at the time. I did find related sources, which include http://www.philiplaven.com/p19.html and http://www.midnightkite.com/color.html. Note at the latter the spectrums which use a wavelength-to-RGB conversion algorithm. On this spectrum, 507 is green -- I would not characterize it as "blue-green".)

For these reasons, I feel it is most correct to simply call 507 nm light "green". While it is towards the blue end of the "green zone" of the spectrum, it definitely is NOT an even mix of blue and green (e.g., cyan). Based on the sources above and especially the wavelength-to-RGB conversion, I feel most people seeing 507 nm light would call it "green". More specifically, if asked to compare 507 nm light with a pure blue (around 470), a blue-green (around 490-495), and a pure green (around 530), I feel most people would say that 507 nm would be closest to green, not to blue-green.

Pmurph5 03:44, 13 August 2007 (UTC)[reply]

This is highly subjective, but both based on the wavelength diagram Image:Spectrum441pxWithnm.png and Image:CIExy1931.png and my personal experience with tunable lasers I would call the range 480-510 nm "blue-green". So I disagree with you. But it wouldn't hurt to mention absolute wavelengths rather than subjective colors on the page. The peak of the night-vision sensitivity is much less relevant than the range, which I would call 450-550 nm, which is "blue and green". Han-Kwang (T) 07:08, 13 August 2007 (UTC)[reply]
Thanks for the comments. I did some more research, including speaking with one of the members of the SAE-G10T laser hazards subcommittee. Greg Makhov of Lighting Systems Design Inc. in Orlando helped SAE-G10T develop laser safety regulations for the U.S. FAA. Greg stated that the relevant parameter is photopic vision, not scotopic as I had mistakenly written in my original Wikipedia entry.
The reason is that pilots and others who might see nightime lasers almost always have some photopic vision. As Greg said: "If you can see colors, then your photopic vision is working." In a cockpit, this is almost always the case (e.g., control screens, etc.). True scotopic vision takes a long time to develop (dark adapt), and has no color perception.
The question of whether pilots see lasers photopically or scotopically was debated by the SAE-G10 committee members. They even considered alternatives such as a mix (mesoptic), or using the union of the scotopic and photopic curves (making a "top hat" curve). The final decision for using photopic data was primarily due to the fact that most pilots were in a bright enough environment that they had color vision (meaning cones, meaning photopic.)
As a result, the FAA's official Visual Correction Factor for lasers also uses a photopic curve. This can be seen in FAA Advisory Circular 70-1, which has forms to be filled out by those using lasers in airspace. Table 5 of AC-70-1 lists wavelength correction factors taken from the CIE normalized efficiency photopic visual function curve for a standard observer.
So, after doing this research, I have changed the Wikipedia entry appropriately. Thanks again for raising this issue which prompted me to look into it further.
Pmurph5 01:49, 15 August 2007 (UTC)[reply]

"Demonstration"

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Underneath "Accidental vs. deliberate exposure", there is a sentence which says "(To demonstrate this, aim a laser pointer at a retroreflective street sign a block or two away.)". It may be a good idea to revise this as it may serve to encourage others to point laser pointers (most likely deliberately) out in the public, in addition to surprising others who happen to be witness to such a demonstration. —Preceding unsigned comment added by Saphius (talk • contribs) 04:19, 2 October 2007 (UTC)[reply]

Good point. I have taken the simple solution by removing the suggestion. It was not particularly encyclopedic in any case. Pzavon 01:55, 3 October 2007 (UTC)[reply]

How to add photo of laser guide star

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This article previously had a photo of a laser guide star. Someone removed it, but I am unclear as to the reason. (The reason cited was that the photo appears in Wikimedia Commons, but I don't think this is true. The removed photo is NOT in Wikimedia Commons.)

Is it possible to use another photo of a laser guide star? There is one in Wikimedia Commons at http://commons.wikimedia.org/wiki/Image:Keck_laser_at_night.png. I don't want to add this willy-nilly without understanding 1) if this is OK and 2) the best way to do this.

Any help from more experienced Wikipedians is appreciated. If you could just put the cited photo in, that would be great. —Preceding unsigned comment added by Pmurph5 (talk • contribs) 23:31, 13 January 2008 (UTC)[reply]

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This article needs some cleanup because:

  • there is legal advice in the article (WP:NOTGUIDE - );
  • there is Howto content (use beam stops, etc.)
  • there is too much "should" in general (it should be noted, pilots should keep in mind).

Furthermore I question some of the statements about the effects of laser pointers from several 100 m distance, for example in the "Example calculations" section, which are provided without a verifiable source. No doubt it is unpleasant to stare into a 50 μW/cm2 beam (laser pointer at 350 ft), but there is no way a hand-held laser pointer would lead to sufficient exposure time to be an issue, even if aimed deliberately. As anyone who has attended a laser-pointer-supported slide show presentation can attest, it is nearly impossible to steadily hit a target the size of a pupil even from 3 m distance, let alone 100 m. I just tried to shine a 1 mW low-divergence green laser pointer from 10 m into my own eye (mirror at 5 m) and it is pretty hard to hit my eye. I estimate that my pointing accuracy is about 5 mrad (+/-2.5 mrad), which would mean exposure during 1/100 of the time assuming 1 mrad divergence. Furthermore, my shaking hands cause the beam to move at 50 mrad/s, which means that the exposure time per flash is 1/50 seconds, and the energy per flash assuming a 0.5 cm2 pupil is 25 uJ/s * 1/50 s = 0.5 uJ. For a moving plane, the exposure is even smaller (10 cm spot size at 100 km/h = 1/300 s exposure). It is not clear whether these considerations are taken into account in the discussion, or that it is always assumed that the laser pointer is mounted on a telescope tripod. Han-Kwang (t) 06:25, 27 August 2008 (UTC)[reply]

Good points. If no one else cleans up first, I plan to significantly clean up this article in mid-to-late September when I get back from a trip.
(1) Regarding the example calculations, these numbers come from the SAE G10-T Laser Hazards Safety Subcommittee, and the numbers are also used by the FAA. They understand that hand-held pointers produce flashes and not steady light. The light levels set for visual effects (distraction, glare, and flashblindness) are what SAE/FAA considers to cause these effects. The photos taken in the simulator show these effects pretty well.
(2) Don't forget that we are talking ranges of many hundreds of meters. A laser pointer's beam spreads out, making the beam wider and thus easier to flash over an object such as a cockpit. Your in-the-mirror test needs to be much further away.
(3) Finally, there have been increasing laser pointer/aircraft incidents -- in the US as many as one per day. If laser pointers were not so noticeable or objectionable, pilots would not be complaining. There are people with 5mW, 50mW and even 500mW pointers doing these stupid things. Especially at the higher powers you bet there are visual effects which "lead to sufficient exposure time to be an issue" - an issue so much that there are arrests, trials and even jail over this misuse with aircraft.
(4) I should restate here in the Talk section that no one should ever point a laser pointer, no matter what power, at or near an aircraft. It could be unsafe for pilots, it may lead to investigations, arrest etc. for the user, and it adds to the incident database that could be used to justify a ban on laser pointers (as was done in New South Wales).
Thanks for your comments and interest! --Pmurph5 (talk) 16:23, 27 August 2008 (UTC)[reply]
(1) Then the statements should be properly sourced and preferably the conditions should be mentioned under which the statements are true (hand-held, hand-held supported on a solid object, tripod)
(2) My experiment was to see how annoying a spot from 10 m distance is and to estimate how accurate my beam pointing is. And it is why my calculation is mostly in mrad units. Moreover the claim is 'closer-by is more dangerous'.
(3) If you consider 50+ mW still a laser pointer (I don't), the article should mention the actual powers rather than the vague "laser pointer".
(4) You can state your opinion here, but such a statement does not belong in any Wikipedia article. Attribute the statement to an authority or stick to the dry facts (dangerous, can get you in trouble).
P.S. sorry for any lack of tact; i'm in a hurry now.
Han-Kwang (t) 17:31, 27 August 2008 (UTC)[reply]
I have done some cleanup. The section "Reducing the hazard" was rewritten to remove the "how-to" tone. Numerous references were added in this section and elsewhere so that authorities were cited. A reference was added for the graphic, to give sources for the distances and photographs. Material was added to the section on "Airspace zones", to correlate the laser limits with the visual effects, and to be clear about what types of lasers are restricted in these zones. References which previously were only at the bottom of the article, such as the FAA simulator studies, were instead put into new text within the article; this gave context to these valuable references.
I understand this does not address all the concerns about giving advice, saying "should", etc. If someone else wants to do this, great; otherwise I have it on my "to do" list (grin!).
Pmurph5 (talk) 18:21, 4 December 2008 (UTC)[reply]


This whole article smacks of nursery school preaching from some police person. There is no inherent risk in reasonably pointing a laser pointer (i.e, <5 mW) at anything or anyone. To suggest otherwise is not physically or optically supported.
http://www.laserist.org/Laserist/Safety_aircraft.html
To even approach the cockpit distraction levels discussed, one would need to be positioned at a runway's approach end with a high powered green laser using a tracking system. Even then, I am not sure the cockpit angle and distance would allow for distracting illumination. To imply that a hand held laser pointer could endanger a pilot at altitude is pure fallacy due to beam spread and attenuation, notwithstanding impossibly focusing from below on a moving target in the dark.
Think about how much safer the world would be if the paranoid were as concerned about guns and bullets as they are about laser pointers.
--187.132.72.26 (talk) 07:25, 1 April 2010 (UTC)[reply]
Agreeing with parent post and not disrespecting pilots and the hazards of lasers, but this is not the venue for telling readers what they "should" do. Also, this reads like a case study Wikipedia:What Wikipedia is not, a How-to manual, and a warning poster. Group29 (talk) 13:24, 5 June 2011 (UTC)[reply]

Colloquial Diction in Article?

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While reading this article, I felt that a lot of the diction (wording) was a lot less formal or encyclopedic then most of Wikipedia's articles. The real standout was this: "Note that while the distances given are exact ("52 feet", "262 feet"), the laser's brightness is in fact falling off slowly. It is not as if at 51 feet the laser is an eye hazard and at 53 feet it is eye safe," but I don't think that's the instance.

I didn't see any first person, though, or any other obvious problems, and I'm not exactly sure how to word this otherwise. Is this against the style guide, and if so, how should it be worded? Dylan (talk) 22:27, 26 February 2009 (UTC)[reply]

A Question of Proportion

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I don't know anything about lasers and the article really just does not give me a sense for how grave an issue this is, except for saying "if this," or "if that," a plane might become involved in a serious accident. I mean I really don't understand what kind of lasers the article is discussing. What is "a legal 5 mW laser pointer"? Is it like the laser pointers you can buy at Office Max for $25USD? Obviously I could take the link to http://en.wikipedia.org/wiki/Laser_pointer and wade through all of that too, but couldn't "Lasers and aviation safety" provide some succinct explanation that would give the laser-ignorant like me some sense for the gravity of this problem? Arcanicus (talk) 17:48, 17 July 2012 (UTC)[reply]

Moral Panic

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This is a highly detailed article for what amounts to "Pointing bright lights at airplanes could theoretically cause a crash." Did this come from a government manual? It's ridiculous. How about pointing lasers and bright lights at cars? Isn't that 1000 times more likely to catch a driver in the eye and 1000 times more likely cause a crash if it does? This smacks of a moral panic. — Preceding unsigned comment added by 199.52.13.130 (talk) 18:29, 4 March 2015 (UTC)[reply]

Video of hundreds of lasers having no effect on helicopters

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http://mashable.com/2013/07/01/egypt-protestors-laser-pointers/ Pilots deal with the sun, moon, and lightning all the time. All more powerful than lasers. 2602:304:B167:A420:4C93:2EC1:24AD:6F5A (talk) 05:51, 18 April 2015 (UTC)[reply]

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Citation 33, USA Today "N.J. man charged with aiming laser…" by Alan Levin 2005 points to a broken link. I couldn't find the article in USA Today archives or Internet Archive. Quesoteric (talk) 17:17, 5 February 2024 (UTC)[reply]

@Quesoteric Fixed the link. Reconrabbit 22:07, 6 February 2024 (UTC)[reply]
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