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Accurate wavelengths

Zom-B

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As I'm usually irritated with all those wavelength-rainbow images floating around which claim to depict wavelengths, but actually don't, and because I also notice a lot of people think 635nm is orange, I decided to create my own.

I created is image myself using a custom Java application and raw data from CIE 1931 2-degree records, interpolated at 1nm intervals, and converted to be represented with the color gamut of typical computer monitors (gamma=2).



The intensity of the colors in the bottom chart is also not numerically representative (the middle one is), because I changed it to reflect perceived brightness a little better.

(note that 405nm blu-ray is about 1400 times less intense than 532nm green, and the pc only knows 256 brightness levels, so it shows up as black)
 

Maven

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i was under the impression that sensitivity to 405nm violet was close to the same as 650nm red. however, in your graph it shows red is precieved as much brighter(i can't even see the line for 405 on the relative sensativity graph)
 

Murudai

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Maven said:
i was under the impression that sensitivity to 405nm violet was close to the same as 650nm red. however, in your graph it shows red is precieved as much brighter(i can't even see the line for 405 on the relative sensativity graph)
Our eyes are around 5-10 times more sensitive to 650nm than 405nm if I remember correctly.
 

Maven

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oh... ok i keep hearing people compare the beam to the beam of a red... i was thinking that they were about the same
 

Zom-B

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The beam visibility is indeed comparable to between those colors. Shorter wavelengths get refracted more by air molecules due to rayleigh scattering. That's the reason the sky is blue, and lower visibility blu-rays have more visible beams.
 

Chicxulub

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405 is 5% as visible as 650. (by averaging 400 and 410 nm wavelengths)

405 is .6% as visible as 532.

632 is red/orange. It's right on the border between red and orange. It depends on the person's eye how they perceive it.

Source- The 1988 CIE Photopic Luminosity Efficiency Function.
 

UMO

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So does it follow that a 30mW green is ~40x more visible than a 120mW blu-ray if it is .6% as visible? 1400x doesn't seem correct. 166x does.
 

moond0ggie

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That is a very informative illustration,
The relative sensitivity scale helps to depict
what frequencies are most easily viewed,

Its easy to see why a 532nM beam is so much more visible as compared to the 650nM beam.
I wonder if you can see a 473nM beam in the night sky as well as you can the 650nM?

Nice work!
 

mikeeey

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quadcam said:
405 is 5% as visible as 650.  (by averaging 400 and 410 nm wavelengths)

405 is .6% as visible as 532.

632 is red/orange.  It's right on the border between red and orange.  It depends on the person's eye how they perceive it.

Source- The 1988 CIE Photopic Luminosity Efficiency Function.
then why have people said a blu-ray laser is easier to see at night than a red laser?
 

Murudai

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mikeeey said:
[quote author=quadcam link=1218492281/0#5 date=1218504753]405 is 5% as visible as 650. (by averaging 400 and 410 nm wavelengths)

405 is .6% as visible as 532.

632 is red/orange. It's right on the border between red and orange. It depends on the person's eye how they perceive it.

Source- The 1988 CIE Photopic Luminosity Efficiency Function.
then why have people said a blu-ray laser is easier to see at night than a red laser?[/quote]

That was answered just a few posts above yours :)

Our eyes are more sensitive to 650nm than 405nm. But the beam visibility is slightly different. Lower wavelengths scatter in the air much better than higher wavelength lasers. Since 405nm is a much lower wavelength than 650nm, it scatters much better in the air and has a more visible beam. Though, since our eyes are less sensitive, the beam is probably around the same really. It's all subjective.
 

brtaman

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moond0ggie said:
That is a very informative illustration,
The relative sensitivity scale helps to depict
what frequencies are most easily viewed,

Its easy to see why a 532nM beam is so much more visible as compared to the 650nM beam.
I wonder if you can see a 473nM beam in the night sky as well as you can the 650nM?

Nice work!
Yeah 473nm in the night sky is almost as bright as a comparable 532 nm mw per mw IMO. It is much brighter at night than 650. My 35mw blue absolutelly devastates my >200mw red in terms of beam visibility. The perceived intensity of the blue wavelenght increases greatly when our eyes are adjusted to the dark.



brtaman
 

mikeeey

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I've never owned a blu-ray so thats why I'm asking so much lol. So can a blu-ray hit the clouds like a green can? you say it scatters, I'm guessing it cant hit the clouds then?
 

Chicxulub

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moond0ggie said:
That is a very informative illustration,
The relative sensitivity scale helps to depict
what frequencies are most easily viewed,

Its easy to see why a 532nM beam is so much more visible as compared to the 650nM beam.
I wonder if you can see a 473nM beam in the night sky as well as you can the 650nM?

Nice work!
Due to Rayleigh scattering, the shorter the wavelength, the brighter the beam will be relatively. My blue laser's dot is as bright as a 5mw green, but it's beam is much brighter.
 

Zom-B

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No, shorter wavelengths don't light up clouds as well as green. Illuminating a cloud has nothing to do with Rayleigh scattering, but only with perceived brightness. Green still beats them all.

Back on the beam visibility subject, the beam diameter is also an important factor in intensity. Most of us poke violet and red diodes in an aixiz, which has a ~4.5mm beam diameter. Most greens however have a 1~2mm diameter, so the light is much more concentrated on the retina too! (in addition to the wavelength being more visible). A two-lens beam contractor (or beam expander in reverse) might increase the beam visibility, but it needs optics of exactly known focal points.
 

Kenom

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it also has a lot to do with our nightime sensativity to light which changes when it's dark versus day.
 




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