Talk:Visible spectrum

In the lede it says:

"The visible spectrum is the portion of the electromagnetic spectrum that is visible to (can be detected by) the human eye."

I don't think we should define the word "visible" here. Even though the definition provided is a perfectly valid definition, it is not the only possible definition of "visible." Many people who are legally blind have eyes that can detect light. Since "visible" is a common word, it should not require a definition. Also, "Visible spectrum" is a noun phrase that cannot be analyzed entirely in terms of its constituent parts. The temperate zone of the Earth, for example, is actually defined astronomically, and only coincides very roughly with the region in which temperate climate occurs.

Next, the range 390nm - 700nm seems odd. Even though it's referenced (to a textbook) I don't think it's one of the five most commonly cited ranges, or even in the top ten. The 390 at one end suggests a degree of precision that is not matched by the 700 at the other end. I suggest we go back to 400nm - 700nm, but qualify it with words such as "conventional," "nominal," or "customary." For example: "The conventional range of the visible spectrum is 400nm - 700nm. This range is, of course, purely nominal."

After that we could mention a few alternative ranges. For example, the CIE range for photopic (color) vision, 360nm - 830nm, and the CIE range for scotopic (night) vision, 380nm - 780nm. There's also a much narrower range, 420nm - 680nm, that comes up occasionally in technical literature, especially biochemistry. Even though that may seem exceedingly narrow, most people rarely see anything below 420nm or above 680nm, not because we are not capable of seeing it, but because our sensitivity at those wavelengths is so weak that they are drowned out by more visible wavelengths.

And finally, two subjects near and dear to my heart.

1) Nowadays many people have access to exotic light sources such as ultraviolet and infrared lasers, diodes, etc. As a result, many people are seeing light at wavelengths far beyond the more widely published ranges. For example, many people who work with uv lasers in the 320s and 330s can see the Rayleigh scattering. At the opposite end, a $15 5mW 980nm laser pointer shined directly into the eye (reasonably safe for up to 0.25 sec.) is clearly visible. In other words, people are "seeing the impossible."

2) Over the years there has been quite a bit of fundamental research into the extremes of human vision. The upshot is that the actual of range of human vision is about 300nm - 1100nm, but with qualifications. For example, children can usually see down to about 300nm, teens and young adults to 315nm, the elderly usually not below 400nm, the middle aged highly variable. In the low 300s color perception and visual acuity are seriously compromised. The more extreme the wavelength (both in uv and ir) the brighter the light needs to be in order to be visible. Eye damage is a serious concern for wavelengths below 320nm (because of the inherent dangers of uv at those wavelengths) and for brightness reasons above 950nm. Zyxwv99 (talk) 02:33, 22 September 2013 (UTC)

References

400-700nm

• Encyclopædia Britannica

http://www.britannica.com/EBchecked/topic/340440/light

• Textbook of Practical Physiology

G.K. Pal, Pal, G.K., Orient Blackswan, 2001 - Physiology - 530 pages http://books.google.com/books?id=CcJvIiesqp8C&pg=PA387

• Vision

Pierre A. Buser, Michel Imbert, MIT Press, 1992 - Medical - 559 pages http://books.google.com/books?id=NSZvt8Ld2-8C&pg=PA50

CIE

• Handbook of Optical Metrology: Principles and Applications, edited by Toru Yoshizawa

http://books.google.com/books?id=DdzBQsqPbzcC&pg=PA5

• http://www.physics.kee.hu/cie/div2/ds010_1.pdf

LIMITS

"In young adults, wavelengths as high as 1000 nm or down to 300 nm may be seen, but the standard range for human vision is typically given as 400-700 nm." Scott E. Umbaugh

• Digital Image Processing and Analysis: Human and Computer Vision Applications with CVIPtools

http://books.google.com/books?id=UQTMw5uoGHgC&pg=PA405

"Limits of the eye's overall range of sensitivity extends from about 310 to 1050 nanometers, but strong illumination is necessary for sensation at these wavelength extremes."

• Color and Light in Nature

David K. Lynch, William Charles Livingston, Cambridge University Press, 2001 http://books.google.com/books?id=4Abp5FdhskAC&pg=PA231

ULTRAVIOLET

"Wave length 334 mμ was described as highly unsaturated blue, bluish gray and silver; 313 mμ was given as light without color, almost colorless, gray with a trace of blue..."

• The Color of Ultraviolet Light

Albert Bachem The American Journal of Psychology, Vol. 66, No. 2 (Apr., 1953), pp. 251-260 http://www.jstor.org/discover/10.2307/1418730?uid=3739256&uid=2129&uid=2&uid=70&uid=4&sid=21102663451727

"According to different authors, under appropriate conditions seeing is possible in the ultra-violet down to a wave-length as small as 3100 Å. This fact has been confirmed on 21 persons (age 25–50 years)..." W. de GROOT

• Seeing in the Ultra-Violet

Nature 134, 494-494 (29 September 1934) | doi:10.1038/134494a0 http://www.nature.com/nature/journal/v134/n3387/abs/134494a0.html

INFRARED Infrared color reversal

• Color Vision: From Genes to Perception

edited by Karl R. Gegenfurtner, Lindsay T. Sharpe Cambridge University Press, May 28, 2001 - Medical - 492 pages http://books.google.com/books?id=4zQMQLLVkFYC&pg=PA93

"The foveal sensitivity to several near-infrared laser wavelengths was measured. It was found that the eye could respond to radiation at wavelengths at least as far as 1064 nm. A continuous 1064 nm laser source appeared red, but a 1060 nm pulsed laser source appeared green, which suggests the presence of second harmonic generation in the retina."

• Visual sensitivity of the eye to infrared laser radiation

David H. Sliney, Robert T. Wangemann, James K. Franks, and Myron L. Wolbarsht Affiliations JOSA, Vol. 66, Issue 4, pp. 339-341 (1976) http://dx.doi.org/10.1364/JOSA.66.000339

Zyxwv99 (talk) 23:38, 22 September 2013 (UTC)

This all seems excellent stuff. Why not make some changes to the article? Martin Hogbin (talk) 13:56, 12 February 2014 (UTC)

This lede states:"A typical human eye will respond to wavelengths from about 390 to 700 nm.[1]" The lede for the article "Light" states:"Under ideal laboratory conditions, people can see infrared up to at least 1050 nm,[8] children and young adults ultraviolet down to about 310 to 313 nm.[9][10][11]" (reference [8] actually states a 1064nm laser was detectable). There are several problems with this lede. First, a "typical" human eye will not only "respond" to visible light, it will "respond" to x-rays and microwaves as well. I'm not sure how to phrase it: 'will see', 'can visualize', 'will visually respond to', 'can sense', but a bald statement about an undefined response is inaccurate. Second, the human eye's sensitivity, especially to UV, diminishes throughout life, hence "typical" isn't very well defined here (and its meaning is unclear, imho). If I recall CIE did define a color space - but that was based on experts in the field (which we should presume biases the result). I've been involved in color matching my entire professional career (35 years), and I've read in numerous texts that the visible spectrum is 430 to 690nm, (Halliday & Resnick (1967) claim that the eye's sensitivity is maximum at 555nm and that it drops to 1% at 430 and 690nm, for a "standard observer"). It seems obvious to me that "typical" eyesight is like "typical" skin color or height or weight. That is, there ain't one. Its a moving target; we all are getting older. Unless there are some useful (global) norms for color vision acuity (?), I think we need to say both that most of us can see colors between 430nm (say) and 680nm under 'typical' viewing conditions and that there are reports of light perception as high as 1064nm, in the lab, and as low as 313nm (I'd like to see another reference confirming that the 1060nm result isn't due to harmonics).Abitslow (talk) 19:59, 7 June 2014 (UTC)

In the Sliney (1976) study, the 1060 nm pulsed laser did in fact generate a harmonic in the retina at 530 nm. It was those harmonics that inspired the study in the first place. Sliney was the U.S. Army's leading expert on laser eye injuries. Many soldiers reported were getting hit in the eye with near-infrared lasers from about a thousand yards away, usually escaping injury, but reporting that they saw a green light. It turns out that longer wavelengths of near ir can do that, but only in short pulses. Continuous wave doesn't do that. The average minimum amount of power needed to see 1064 nm (CW) was 0.069 mW, with 20-minute dark-adapted eyes, 3mm diameter beam, and three filters, each blocking out 99.9 of light more than 5 nm from the target wavelength. Nowadays huge numbers of people own or work with near ir lasers. I have a 300 mW 808 nm that produces clearly visible light, and a 5 mW 980 nm that I can see clearly when shined (briefly) directly into the eye. You can buy lasers like this on eBay for $15. They use them for fake currency detection, as some national currencies have dyes that reverse-fluoresce under 980 (reverse Stokes uptake).

The business about 310 nm UV is definitely age dependent, but only up to a point. Between 310 and 302 the opacity of the lens and cornea each increase by several orders of magnitude (how many varies with age). Up to age 30, nearly everyone can see UV down to 310. Between age 30 and 45 the lower limit of vision in the UV gradually increases, eventually extending into the ordinary violet.

Both the UV and ir research has been repeated by multiple studies, and confirmed by the millions of people worldwide who work with exotic wavelengths. And yes, people can see x-rays, gamma rays, and beta particles, the latter two generating Cerenkov radiation in the retina. At 310 nm people who can see that low have good visual acuity up to 4 inches, with some very limited color perception. In the near infrared, things are crystal clear.

The most widely cited figure for "visible light" is 400-700nm. Every field of human endeavor that involves light and color has it's own range. However, the 400-700 nm figure is the non-specialized range. Obviously this involves consensus decisions, value judgements, opinions about where to draw the line. However, it is not our job to improve the English language by redefining commonly used words. Words mean what they mean. Zyxwv99 (talk) 21:15, 8 June 2014 (UTC)

Update: I just thought of a solution to this. We're basically arguing over the lede, which I haven't even touched in this article. I think the place to start is with the body of the article. There we can explain the most widely used definitions of visible light, including who uses them. The 400-700 nm range seems to be used mainly for didactic (teaching) purposes, e.g., introductory textbooks, encyclopedias, etc. Zyxwv99 (talk) 13:32, 9 June 2014 (UTC)

Color Wavelength Frequency Photon energy violet 380–450 nm 668–789 THz 2.75–3.26 eV blue 450–495 nm 606–668 THz 2.50–2.75 eV green 495–570 nm 526–606 THz 2.17–2.50 eV yellow 570–590 nm 508–526 THz 2.10–2.17 eV orange 590–620 nm 484–508 THz 2.00–2.10 eV red 620–750 nm 400–484 THz 1.65–2.00 eV

should be changed to

Color Wavelength Frequency Photon energy violet 380–450 nm 789-668 THz 2.75–3.26 eV blue 450–495 nm 668-606 THz 2.50–2.75 eV green 495–570 nm 606-526 THz 2.17–2.50 eV yellow 570–590 nm 526-508 THz 2.10–2.17 eV orange 590–620 nm 508-484 THz 2.00–2.10 eV red 620–750 nm 484-400 THz 1.65–2.00 eV — Preceding unsigned comment added by Tempedi (talk • contribs) 15:57, 31 May 2017 (UTC)

The section "Animal color vision" makes this statement about snakes: "other snakes with the organ may detect warm bodies from a meter away." However, no "organ" is mentioned in this section, so it is unclear what is meant here by "the organ." Presumably there was something here previously about which organ allows a snake to perceive radiant heat, but no such reference is present now. This statement needs to be made clearer. — Preceding unsigned comment added by 2601:602:8480:3343:2145:CFCE:C4CA:A507 (talk) 05:03, 4 February 2019 (UTC)

I don't know if it is already mentioned in this quite large page, but... I want to say that when the spectrum from a sunlit prism (corners 60°) is observed at a large distance (the distance prism - projection screen) then one shall notice the absence of the colors orange, yellow, yellowish green, cyan (greenish blue), and indigo. There's only the three colors red, green, and ultramarine blue (the same colors from the RGB color model). So... Sir Isaac Newton's color system (red, orange, yellow, green, blue, indigo, violet) is a bit childish or schoolish. Johann Wolfgang von Goethe also knew about this rather childish approach of Newton and noticed Newton's wrong observations after he (Goethe) performed his own experiments with sunlit prism. Moreover, there's no violet in the spectrum of white light! Sir Isaac Newton observed the Primary Rainbow but he didn't knew about the existence of the Supernumerary Arcs on the "inside" (on the blue part) of the bow. He noticed a color that he called violet, but... what he really observed was the "overlap" of the ultramarine blue from the Primary Rainbow with the red from the first Supernumerary Arc. This "overlap" is the color Magenta (deep pink). Newton must have been unaware of the existence of the "overlap-color" Magenta, thus... he thought he observed the color violet. DannyJ.Caes (talk) 07:25, 5 August 2019 (UTC)

Perhaps a case of anomalous color vision (indeed, deuteranomaly can be found in 6% men). Or crankery. Incnis Mrsi (talk) 09:59, 5 August 2019 (UTC)

Anyway it’s the spectral color article where color perception is to be addressed. “Visible spectrum” mostly stresses the fact that certain part of the EM spectrum is visible. Incnis Mrsi (talk) 10:15, 5 August 2019 (UTC)

Goethe's work is covered at Theory of Colours. Fundamentally, Newton and Goethe explored two different aspects of light. Newton's work correctly addresses the spectral composition of light, and identifies the apparent colors of monochromatic radiation. Goethe's work addresses aspects of human color vision that are ignored in Newton's work. From a physics perspective, Newton's work is fundamental—physics cares about the nature of light itself, not how colors appear to the eye. The Newtonian model cannot easily tell you where pink or brown come from, however. (NB: You cannot make a brown spotlight.)--Srleffler (talk) 18:09, 29 August 2019 (UTC)

The chart is incorrect at the end of spectrum: the atmosphere is quite transparent to the long waves. — Preceding unsigned comment added by 2003:DF:2812:FF05:EEF4:BBFF:FE36:3F5C (talk) 07:42, 25 September 2020 (UTC)

According to NASA the ionosphere is opaque to wavelengths longer than about 10 m.--Srleffler (talk) 16:16, 27 September 2020 (UTC)

While reorganising the article Optical window, I noticed that although this atmospheric window is characterised as optical, its range also covers the UV and infrared spectra. After some research I found that many valid sources differentiate between the visible and optical spectra, defining the visible spectrum as the one the human eye can detect and the optical spectrum as the one including the UV, the visible and the infrared spectra (see for example Frank L. Pedrotti's "Introduction to optics", Cambridge University Press, 2017, pp. 7-8). It seems that at some point in scientific history the terms optical and visible coincided, something that might hold true for many contemporary scientific fields as well. However, the matter should be looked into and this article should probably not present the terms visible spectrum and optical spectrum as synonymous.--L'OrfeoGreco (talk) 04:07, 28 December 2021 (UTC)