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FrozenGate by Avery

What is the wavelength of pure yellow?

What is the wavelength of pure yellow?

  • 565 nm

    Votes: 1 3.7%

  • 570 nm

    Votes: 2 7.4%

  • 575 nm

    Votes: 3 11.1%

  • 580 nm

    Votes: 8 29.6%

  • 585 nm

    Votes: 7 25.9%

  • 590 nm

    Votes: 5 18.5%

  • 595 nm

    Votes: 1 3.7%
  • Total voters
    27
zyxwv99

zyxwv99

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This is one of the trickier colors. We see yellow when the red and green cone-cells in our eyes are equally stimulated (after automatic adjustments by the neural circuitry). However, the relative sensitivities of the green and red cells varies with brightness. As a result, yellows that trend slightly towards green will become much greener at high brightness levels. Those that trend slightly towards orange will become far more orange. (This called the Bezold–Brücke shift.) On the other hand, this effect is very slight at low and medium intensity levels, just pronounced at high intensity. There is also a thin sliver of the yellow spectrum that doesn't shift (one of the "invariant hues"). (http://www.handprint.com/HP/WCL/IMG/bezbruk1.jpg)

Then there's "metamerism," the tendency of the same color to look different with changes in background or surroundings. For example, the Wikipedia article for "brown" (color), under the "optics" heading, shows two disks on a checkerboard, one in the light, one in shadow. The one in the light looks brown while the one in shadow looks orange, even though both disks are the same color.

And finally, people have different ideas of what counts as yellow. If it trends too much towards green, we see it as greenish-yellow. However, if the plainest sort of yellow is shifted a little towards orange, it just seems like a happier, more cheerful sort of yellow. Scoot it over even more, and it takes on a rich warmth, but still seems yellow. Even amber, which leans strongly towards orange, is often regarded as just another sort of yellow. For example, yellow traffic lights in the US have a color officially called amber, with a peak wavelength of 594nm. However, most people don't even notice, and just think of it as yellow.

So give me your best guess on the most neutral, plainest sort of yellow.
 





Well it looks like 565nm is well into the greenish-yellow and 585nm is probably leaning goldish yellow, so around 575nm-580nm should be pretty dead on yellow. But I don't have much to base off of other than 543nm and 593.5nm soooo :p not very many people have seen colors in between those bounds (an Ar/Kr will get you 568nm, there's 556nm and 561nm DPSS, but not much else...)
 
Thanks for the comments (and voting of course). It's nice how people arrived at their conclusions. I picked 580, but didn't want to vote until other people had a chance.

On the one hand, this is not a scientific study. On the other hand, scientific studies are usually carefully controlled, which can be a bad thing when it comes to color perception.

People here at LPF are far more aware of the relationship of wavelength to color than most people. They not only know the wavelengths of their lasers, but have seen them in a wide range of lighting environments, indoors, outdoors, day, night. Then we have the benefit of reading other people's posts on what laser colors look like, and whether what the camera sees is what people see with eyeballs.

That means even the educated guesses here are hugely meaningful.
 
Perhaps. The yellow-green area is probably the weakest wavelength range in terms of number of people who have seen those wavelengths... the orange gap is 612nm to 635nm unless you can afford a 620nm diode, while the yellow-green gap can be 543nm to 589nm or even 532nm to 589nm if you don't have any gas lasers

But I do agree. To me 532nm has some signs of yellow when it's dark out but looks a slightly warmer shade of green (less yellow) in the daytime. Anyone else notice this? I'm guessing it's due to scotopic vs photopic sensitivity?
 
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Why are these still a thing???

Having seen 532, 543, 568, 589, and 593. I say 589 is the most "pure yellow" from that range.

Still though. These threads are very annoying...

3150568-tactical-facepalm.jpg
 
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hwang21 said:
Perhaps. The yellow-green area is probably the weakest wavelength range in terms of number of people who have seen those wavelengths... the orange gap is 612nm to 635nm unless you can afford a 620nm diode, while the yellow-green gap can be 543nm to 589nm or even 532nm to 589nm if you don't have any gas lasers

But I do agree. To me 532nm has some signs of yellow when it's dark out but looks a slightly warmer shade of green (less yellow) in the daytime. Anyone else notice this? I'm guessing it's due to scotopic vs photopic sensitivity?
Click to expand...

I haven't yet explored the region between 612nm and 635nm. One person here has a 20mW 556nm laser pointer (http://laserpointerforums.com/f40/new-portable-dpss-wavelength-556nm-20mw-cni-65451.html). Besides posting photos, the user describes the color as "It isn't yellow, it isn't really green. My best description is that it's the colour of a banana that is half-way between unripe green, and ripe yellow. "

As for scotopic vs. photopic, the latest research indicates that this could play some role, but apparently minor. Besides the Bezold–Brücke shift (green shifts towards yellow at higher brightness) there is the Abney effect (green shifts towards blue when white is added).

In this case the main culprit may be metamerism. This is change in perceived color due to changes in background illumination as well as the color and brightness of surrounding objects. This is much more of an issue with narrow-band sources. For example, laser projectors give much less consistent perceived color than any other kind of projector.

That's why we can never get exact matches of wavelengths to color, much less color names. On the other hand, we can at least get a feel for where the "center of gravity" is, from people who have viewed narrow-band source in a wide variety of viewing conditions.
 
Bloom, if there's science/explanation involved then I think it's interesting such as the post above. Other than that it's kinda the same answer across the board, then yea it gets annoying. But this is interesting stuff with the Bezold-Brucke shift, Abney effect, metamerism, etc
 
Voted for 580.
For what it's worth I like these polls.
They might not be scientific but they're a good way to have an idea of the variations in color perception.
I actually made some of these polls back then, when I intended to make a better wavelength to RGB "converter". Never got around to doing it, though.
 
I think there a lot fewer variations in color perception than most people think. Also fewer variations in color naming than most people think. That plus obvious things that can skew color perception, such as brightness, whiteness, lighting, and neighboring colors. However, these things are pretty well documented so that for some colors you can actually attach a color name to a wavelength. There don't seem to be many named colors where that can be done with any degree of consistency, but I'd like to find out which ones they are and use them as landmarks.

Meanwhile, I have new graphics (in my photo album) I made from two hex converters, this one (Wavelength to RGB / HEX Calculator) and this one (http://www.efg2.com/Lab/ScienceAndEngineering/Spectra.htm).
 
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bloompyle said:
Why are these still a thing???

Having seen 532, 543, 568, 589, and 593. I say 589 is the most "pure yellow" from that range.

Still though. These threads are very annoying...

3150568-tactical-facepalm.jpg
Click to expand...

I'm with bloom on this somewhat. And true bright lemon yellow is 578nm.
 
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