This might be a dumb question and why I'm gonna ask it is gonna make me sound pretty silly.

How come yellow is so much brighter than the other colors? I mean, I understand the hue/saturation/brightness stuff, and the primary colors or light or pigment mixin', and the visible light spectrum and all that jazz. That doesn't explain why yellow out of all of 'em is the brightest! Yeah you can have a really bright blue that's still blue, or a really not-bright blue that's still blue, but if something's yellow, it's bright. If it's not bright, it's not really yellow! I don't think it's just because the category of colors we call yellow is limited to bright yellow, since if you look at the regular spectrum then yellow is the brightest one, not blue or something.

I'm asking 'cause I've been coloring. Like in a coloring book, you know? Only not pictures of ponies or whatever, but these geometric patterns. They're symmetric over three lines, so there are six identical pie-slices. There are ribbons that run over the different areas. I blacked out a lot of it, and now I've got a bunch of circular ribbons of twelve different colors going all over the place. The colors are the six rainbow colors and all the intermediaries (red, red-orange, orange, yellow-orange, yellow, yellow-green, green, blue-green, blue, blue-violet, violet, red-violet). I've got a whole chunk of it done and when I look at it from a distance the only color that's really easy to pick out of the bunch is the yellow because it's so bright!What's up with this? Why is yellow so much brighter than the other basic colors?

Does it have anything to do with the fact that the sun appears yellow in the visible spectrum, and we've evolved to "notice" the sun?

The yellow pigment in paints etc is very weak. More light is reflecting off the white paper I assume you are using as a backing than for the other colours. Try using black paper and you'll see the difference.

Btw a 'weak' yellow is brown - both are mixtures of green and red light.

Yeah, probably to do with the way our eyes (rods or cones or whatever) are set up.

EDIT: Actually it's probably what Brennan said!

I'd speculate it might have to do with the fact that yellow light stimulates both M and L cones to a high degree:
http://content.answers.com/main/content/wp/en/6/65/Cones_smj2_E.png

It seems that off all colors this one would produce the most stimulation.

Brennan - that makes sense, but still what about a rainbow? Yellow is always brightest!

Perfy, I think that's what I was looking for. So it's 'cause the human eye only sees color in mixes of the primary colors of light?

I got a bunch more three-year-old-like questions. Hey, I was coloring.

Is there any particular reason those are the colors we can see? Can other animals see different primary colors? Like maybe some weird fish mixes orange, blue, and purple?

Also how come we see in those colors if colors are all different specific wavelengths? Do gadgets in our eyes break down a purple wavelength into blue and red ones somehow?

If our eyes are breaking down yellow into the red and green, is there just as much red as there was yellow and just as much green as there was yellow? 'Cause if it was breaking down into parts it should lose brightness.

Are you apologising for having fun? And for asking questions? [pissed]

Apparently the different cones each respond to a range of wavelengths rather than a specific colour. So the colour you see depends upon the variation in the three responses.

I guess we talk about the primary colours being Red, Green and Blue because we can exploit the way the cone cells work to fool our eyes into seeing all the other colours based upon this mechanism. There is never any yellow, cyan or magenta light coming from your screen, only RGB, but your eyes can't tell the difference.

Good find Perf. :)

Are you apologising for having fun? And for asking questions? [pissed]

I don't see an apology! Just explainin' how come I got these questions. Three-year-olds ask some pretty good questions sometimes anyway!

Apparently the different cones each respond to a range of wavelengths rather than a specific colour. So the colour you see depends upon the variation in the three responses.

I guess we talk about the primary colours being Red, Green and Blue because we can exploit the way the cone cells work to fool our eyes into seeing all the other colours based upon this mechanism. There is never any yellow, cyan or magenta light coming from your screen, only RGB, but your eyes can't tell the difference.

Good find Perf. :)

So it's like a triangulation thing? I guess that means that we've got such a neat spectrum 'cause we have three different types of receptors... and a two-kinds-of-receptors animal would only be able to see a gradient from one color to another. Are there any creatures with four kinds of receptors?

If it's a range... that explains how it breaks 'em down, I guess? That's pretty cool. Based on Perfy's graph, though, it seems like it would be hard to distingush between reds through greens 'cause there's a lot of input from red and green!

How does colorblindness work? One of the receptors goes bad? Red-green colorblindness would happen if red or green receptors were no good, yeah?

http://mcdb.colorado.edu/courses/3280/images/photoreception/four-spectra.gif

I'm just guessing here, but it look like yellow maximally stimulates the red cone (counter-intuitive, I know) without stimulating the blue cones very much at all. This sets up a near-maximum contrast between those two systems, and our system interprets that as 'really bright'. Our blue cones tend to be our brightness detectors.

But I'm not actually sure. It wouldn't be operating under the same system as why white light appears bright. I can't see colour, and so I can't use too much intuition on this question.

http://eosweb.larc.nasa.gov/EDDOCS/images/Erb/wavelength_figure.jpg

[...] I can't see colour, and so I can't use too much intuition on this question.


Are you red-green colour-blind or don't you really see any colour (or some other rare variant)?

So it's like a triangulation thing? I guess that means that we've got such a neat spectrum 'cause we have three different types of receptors... and a two-kinds-of-receptors animal would only be able to see a gradient from one color to another. Are there any creatures with four kinds of receptors?

How does colorblindness work? One of the receptors goes bad? Red-green colorblindness would happen if red or green receptors were no good, yeah?Now there's a couple of good questions! Colourblindness seems complicated. Wiki (http://en.wikipedia.org/wiki/Colourblindness) is your friend. It seems to relate in most cases to a lack of one or other set of cones.

Apparently there are creatures that are Tetrachromatic (http://en.wikipedia.org/wiki/Tetrachromacy) (they have four different types of cones). There seems to be a distinct possibility that this includes some humans with an unusual genetic heritage.

El'M: Are you Achromatopic (http://en.wikipedia.org/wiki/Achromatopsia)?

Is there any particular reason those are the colors we can see? Can other animals see different primary colors? Like maybe some weird fish mixes orange, blue, and purple?


There is nothing unique about the primary colors. They're merely picked because they are common and distict. You can actually choose any three colors, and make any other color you want. For example, odds are your printer works in CYMB. This means it mixes Cyan, Yellow, Magenta and Black dyes to produce whatever color you need. It's close to RGB, but it is different, and works just as well.


Also how come we see in those colors if colors are all different specific wavelengths? Do gadgets in our eyes break down a purple wavelength into blue and red ones somehow?


Yes. The cones in our eyes see a certain wavelength with a certain bandwidth, and then the brain 'mixes' the signals together, forming the color spectrum you physically see.

There is nothing unique about the primary colors. They're merely picked because they are common and distict. You can actually choose any three colors, and make any other color you want. For example, odds are your printer works in CYMB. This means it mixes Cyan, Yellow, Magenta and Black dyes to produce whatever color you need. It's close to RGB, but it is different, and works just as well.

I don't think that's true. RGB are the primary colors of light, RYB, or CYM, of pigment. I don't think you can choose just any three colors.

well, you guys totally blew my explanation out of the water

i'm going to the corner to sulk now

I don't think that's true. RGB are the primary colors of light, RYB, or CYM, of pigment. I don't think you can choose just any three colors.

I once got into this argument with both my Photogrametry and Remote Sensing profs. You can make any color out of just about any 3 colors (3 becuase of the 3 cones). Our Remote prof went so far as to bring cellophane in :p

RGB is what you use in computer monitors, CYMB is used for printers, RGY is what you tend to learn in grade school, older printing techniques used Orange-Green-Violet. The choice is entirely arbitrary.

El'M: Are you Achromatopic (http://en.wikipedia.org/wiki/Achromatopsia)?

Not really, but I tell people that for convenience. I have yet to find a test which specifies my condition. My suspicion is that I'm red/green colourblind but that my S-opsin (blue receptor) is a bit whacky. So I certainly see things rather differently from most people (and this causes me some trouble in figuring out the colour system)


Colour vision is mostly the differential firing between Red and Green cones, a lightwave will tend to activate one receptor more than another and then downstream neurons will judge the difference. Every receptor eventually will get stimulated by any specific wavelength, but the probably of firing will change based on the wavelength.

Our blue receptors then add an 'intensity' component to the colour, which then allows the colour to be identified. This 'intensity' component starts with our blue receptors, but they're actually (mostly) wired into our brain differently than our a red/green receptors. So, it's less a 'triangulation' and more of a 'bianglution' coupled with a flavour of intensity.

I'm just guessing here, but it look like yellow maximally stimulates the red cone (counter-intuitive, I know) without stimulating the blue cones very much at all. This sets up a near-maximum contrast between those two systems, and our system interprets that as 'really bright'. Our blue cones tend to be our brightness detectors.

But I'm not actually sure. It wouldn't be operating under the same system as why white light appears bright. I can't see colour, and so I can't use too much intuition on this question.

So less input to the blue cone indicates brightness? That makes sense! Man, that makes a ton of sense.

But yeah, that doesn't explain white...

I once got into this argument with both my Photogrametry and Remote Sensing profs. You can make any color out of just about any 3 colors (3 becuase of the 3 cones). Our Remote prof went so far as to bring cellophane in :p

RGB is what you use in computer monitors, CYMB is used for printers, RGY is what you tend to learn in grade school, older printing techniques used Orange-Green-Violet. The choice is entirely arbitrary.

I'm not gonna let you off that easy. I'mma have to go get my own damn cellophane. :mad:

How could you print yellow with OGV? Or print red for that matter? The absorption/reflection thing has made so much sense to me, this is crazy! I'm not going to be able to mix paint anymore because of you, I'm gonna be questioning too much...


New question, which might be outside the realm of science. Why are the colors we see the way they are? Is there any particular reason, or is it just one of those "'cause that's the way it is" things?

Also, the "tetrachromatic" creatures... do they see extra colors? Or is there just better definition in the spectrum we're familiar with?

How far does the visible spectrum range for different animals? Does it vary much in humans?

Interesting thread. White is also a bright colour.(IMO)

It can't just be the (anti)stimulation blue receptors that dictate how bright something is, or else black (which doesn't stimulate the blue receptors at all) would appear bright.

Maybe it just goes back to what Brennan said -- white things reflect more light than, say, grey things, so appear brighter.

It can't just be the (anti)stimulation blue receptors that dictate how bright something is, or else black (which doesn't stimulate the blue receptors at all) would appear bright.

Maybe it just goes back to what Brennan said -- white things reflect more light than, say, grey things, so appear brighter.

But why does Yellow appear Brighter than White ?

I'm gonna go with: it doesn't.

@Warpus, well to be fair you've identified the reason are eyes are sensitive to that part of the EM spectrum in particular.

I'm not gonna let you off that easy. I'mma have to go get my own damn cellophane. :mad:

How could you print yellow with OGV? Or print red for that matter? The absorption/reflection thing has made so much sense to me, this is crazy! I'm not going to be able to mix paint anymore because of you, I'm gonna be questioning too much...


Autochrome used OGV. http://en.wikipedia.org/wiki/Autochrome_Lumi%C3%A8re

I believe it was based on the same subtractive principles. There's no real reason why it wouldn't work, the only trick is developing the complimentary 'filters' that remove a wavelength from white light. This gives you your classic negative image. Reverse it and you get a true color positive.



New question, which might be outside the realm of science. Why are the colors we see the way they are? Is there any particular reason, or is it just one of those "'cause that's the way it is" things?


That's a very philosophical question, and yeah, it is what is (for most people).


Also, the "tetrachromatic" creatures... do they see extra colors? Or is there just better definition in the spectrum we're familiar with?


Generally, yes, they do see extra colors. I know many tetrachromes have receptors in the UV range, which allows them to see smaller things IIRC. But they can see things no human ever could with the naked eye. Some could see thermal emissions (night vision goggles) or UV (which will actually damage human eyes). What that would actually look like is something I try not to think about.

If their fourth receptor was in the 'visible spectrum' as we know it, they would most likely be able to differentiate more colors. After all, there is an infinite (well, finite but uncountable) amount of colors you can get by subdividing the traditional rainbow of colors.


How far does the visible spectrum range for different animals? Does it vary much in humans?

I do believe for humans there is fairly little variation in spectral range.

here's a secret......

that's where the idea that men prefer blonds comes from ;) they don't really, but the eye automatically tends to track on moving gold. :p

there is an infinite (well, finite but uncountable) amount of colors you can get by subdividing the traditional rainbow of colors.I thought frequency was one of those observables with non discrete values.

I thought frequency was one of those observables with non discrete values.

Well, I assume once you get down to things like Planck lengths, we will see a quanticized minimum value for wavelength, and thereby frequency. But even with that upper bound, it is for all intents and purposes infinite.

I don't think a wavelength is really a length.

We'd better stop expressing them in nanometres then, yes? :p

We'd better stop expressing them in nanometres then, yes? :p
It's more a local property of a particle that happens to share the same units as actual lengths :p

Wavelength is simply another way of describing the particle's momentum.

If it looks like a length and smells like a length...

Yes, tetrachromats actually see more colours. They could see differences that you or I wouldn't be able to see: though it depends on how their system was set up (and I think it's currently being investigated). We have red/green opponency, with blue being a separate metric. A tetrachromat has more variation, but more types of variation as well.

Mise: black isn't bright because it doesn't stimulate any cones. Yellow stimulates two cones, but not the blue cone (very much). I don't know why white's so bright, unless it's a completely separate qualia (which it might be)

It's more a local property of a particle that happens to share the same units as actual lengths :p

Wavelength is simply another way of describing the particle's momentum.

No, wavelength is how far that particle will go in one cycle. It is very much a real unit.

No, wavelength is how far that particle will go in one cycle. It is very much a real unit.
One cycle of what...? ;)

I don't think a wavelength is really a length.Why not, there are clearly phenomena (interference) that have physical lengths dependent on wavelengths?

Why not, there are clearly phenomena (interference) that have physical lengths dependent on wavelengths?
Those wave-like phenomena could be restated in terms of the particle's momentum. For exampe, diffraction is a direct result of the uncertainty in the particle's momentum as it passes through the slits (i.e. you know its position must be confined to the width of the slits, so there must be a finite uncertainty in its momentum along the same axis).

Ultimately, though, a photon is neither a wave nor a particle. And it's not both, either. It's something separate from either of those things. In some situations we can treat it as a classical wave -- in which case it makes sense to refer to its wavelength and frequency; in other situations, we can treat it as a classical particle, in which case it makes sense to refer to its momentum and energy. Either way, though, they are both equivalent representations of the same system.

Anyway, the point is, a classical wavelength is indeed a length, and has a real distance associated with it. A photon isn't a classical wave, so doesn't have a classical wavelength; it has a "quantum wavelength", or "corresponding wavelength", or some other such description. The physical interpretation of a photon's wavelength is simply its relationship with the photon's momentum.

Bees certainly see more colours than we do. That's why some apparently drab flowers attract bees.
Yellow may also appear bright because those photons carry more energy than other colours, whilst also maximally stimulating one type of cone. This may give a larger signal in that cone type, saturating it and stopping it firing at all.
No firing at all would lead the brain to conclude that there's a very bright light, which it therefore perhaps processes as akin to white.

Those wave-like phenomena could be restated in terms of the particle's momentum. For exampe, diffraction is a direct result of the uncertainty in the particle's momentum as it passes through the slits (i.e. you know its position must be confined to the width of the slits, so there must be a finite uncertainty in its momentum along the same axis).

Ultimately, though, a photon is neither a wave nor a particle. And it's not both, either. It's something separate from either of those things. In some situations we can treat it as a classical wave -- in which case it makes sense to refer to its wavelength and frequency; in other situations, we can treat it as a classical particle, in which case it makes sense to refer to its momentum and energy. Either way, though, they are both equivalent representations of the same system.

Anyway, the point is, a classical wavelength is indeed a length, and has a real distance associated with it. A photon isn't a classical wave, so doesn't have a classical wavelength; it has a "quantum wavelength", or "corresponding wavelength", or some other such description. The physical interpretation of a photon's wavelength is simply its relationship with the photon's momentum.


Maybe you could explain diffraction with momentum (You can make it plausible, but I am not sure that you could quantitatively explain all phenomena). But the mentioned interference would be pretty hard to explain with a particles momentum. Why exactly would one particle create an interference pattern after passing double slits? I challenge you to explain this entirely in a particle and momentum paradigm.

My point is: the particle and wave approximations are not equivalent. There are points where the particle approach fails, and there are points where the wave approach fails (and there are points where both fail). Both are imperfect approximations of the underlying quantum field.

And wavelength can be interpreted as a real length: It is the interaction scale of a particle.

btw: if you say that a photon isn't a particle, then you bascially abolish the very concept of particles, because you could say that about every particle. They're all just states of a quantum field.

Those wave-like phenomena could be restated in terms of the particle's momentum. For exampe, diffraction is a direct result of the uncertainty in the particle's momentum as it passes through the slits (i.e. you know its position must be confined to the width of the slits, so there must be a finite uncertainty in its momentum along the same axis).How under this restatement do we get double slit interference patterns?

Ultimately, though, a photon is neither a wave nor a particle. And it's not both, either. It's something separate from either of those things. In some situations we can treat it as a classical wave -- in which case it makes sense to refer to its wavelength and frequency; in other situations, we can treat it as a classical particle, in which case it makes sense to refer to its momentum and energy. Either way, though, they are both equivalent representations of the same system.

Anyway, the point is, a classical wavelength is indeed a length, and has a real distance associated with it. A photon isn't a classical wave, so doesn't have a classical wavelength; it has a "quantum wavelength", or "corresponding wavelength", or some other such description. The physical interpretation of a photon's wavelength is simply its relationship with the photon's momentum.Well, if you can explain the above I would be much more inclined to believe you.

Note: I'm not saying you're wrong, it's just that I'm unconvinced and a lot of that is due to my ignorance (I was never taught Dirac equation stuff)/

Maybe you could explain diffraction with momentum (You can make it plausible, but I am not sure that you could quantitatively explain all phenomena). But the mentioned interference would be pretty hard to explain with a particles momentum. Why exactly would one particle create an interference pattern after passing double slits? I challenge you to explain this entirely in a particle and momentum paradigm.
You can indeed quantitatively describe diffraction by reference to momentum and the HUP. It's fairly straightforward -- all you need to know is a bit of trig, and the x-p uncertainty relation.

Interference is described by reference to the particle's wavefunction. If you have two slits, slit A and slit B, then there are two paths that the particle could take, path A and path B, with separate probability amplitude functions (i.e. wavefunctions that describe a particle in state A and B separately) A and B. The resultant wavefunction is the sum of these two individual wavefunctions. You'll be left with something like Y(x) = exp(ik.yA(x)) + exp(ik.yB(x)), where yA(x) and yB(x) are the distance the wave originating from slit A and B respectively have travelled to reach position x on the screen. The square of this wavefunction, |Y(x)|^2, is the probability of the particle hitting position x on the screen. Which of course is the diffraction pattern.

Even classically, the diffraction pattern is simply the convolution of the function that describes the slits, and the function that describes the propagation of the (supposedly real) classical wave. I don't see why this needs to be a real wave for it to work. Indeed, if the photon isn't really a wave, and "wavelength" really doesn't have any physical significance, then we ought to rewrite the equations, substituting lambda for h/p. Lambda, then, is just shorthand for h/p. The equations would still work either way.

My point is: the particle and wave approximations are not equivalent. There are points where the particle approach fails, and there are points where the wave approach fails (and there are points where both fail). Both are imperfect approximations of the underlying quantum field.
Well, yeah... but I don't see how that implies that the wavelength is really a length.

And wavelength can be interpreted as a real length: It is the interaction scale of a particle.
You could interpret it as such, but then the wavelength wouldn't be a property of the photon, but rather a property of the photon-slit system. That is, the term "wavelength" is only relevant to situations in which the photon is interacting with something else, and is meaningless to a photon in isolation. This is in contrast with a classical wave (a water wave, or a sound wave), where the wavelength really is an intrinsic property of the wave itself, and is relevant to the wave in isolation (not just in situations where the wave interacts with something else).

btw: if you say that a photon isn't a particle, then you bascially abolish the very concept of particles, because you could say that about every particle. They're all just states of a quantum field.
I meant "classical particle", analogous with a "classical wave". Obviously, they're particles in the same way that all fundamental particles are particles. I don't know a better word to use for photons/electrons/etc. My first QM lecturer called them "wavicles".

Well, I assume once you get down to things like Planck lengths, we will see a quanticized minimum value for wavelength, and thereby frequency. But even with that upper bound, it is for all intents and purposes infinite.
I don't think a wavelength is really a length.

That seems to be dodging the bullet.

If wavelength is really a property of momentum the same restrictions should apply as with position, right? As far as I know the two are symmetric. If there is a minimum nonzero length, then by symmetry there should be a minimum momentum.

But that all comes from a different area of reasoning then what I was referring to. I was commenting that for a typical particle, variables such as position, linear momentum, and wavelength can take on any value; the equations that describe these quantities allow a particle to exist in any arbitrary fractional value. This is unlike for example angular momentum, which always takes on discrete values.

Now I don't really understand this plank length business, but I would caution against the assumption that just because there is a minimum length that length is discrete. This is quantum mechanics were talking about, and classical intuition need not apply.

That seems to be dodging the bullet.

If wavelength is really a property of momentum the same restrictions should apply as with position, right? As far as I know the two are symmetric. If there is a minimum nonzero length, then by symmetry there should be a minimum momentum.

There may be a minimum non-zero length/momentum/frequency/energy etc etc, but I don't really see why...

The de Broglie wavelength of the Earth is probably smaller than the Planck length, but I don't doubt that, if going slowly enough, and through a small enough set of apertures, it would interfere with itself.

I look forward to an impromptu demonstration of planetary quantum interference at the next meetup. :)

But that all comes from a different area of reasoning then what I was referring to. I was commenting that for a typical particle, variables such as position, linear momentum, and wavelength can take on any value; the equations that describe these quantities allow a particle to exist in any arbitrary fractional value. This is unlike for example angular momentum, which always takes on discrete values.


No, angular momentum can take non-discrete values. It doesn't make any sense to claim that momentum is continuous and angular momentum is not, because angular momentum is just the product of momentum and radius.

Both are only discrete, when the particle is in a bound state. A "free" particle can take continuous values for momentum and angular momentum.

Maybe one could try to take the whole universe or just the solar system as some kind of bound state and try to calculate quantized states for "free" particles. And there might be new physics at very high energies that would lead to quantized lengths. However for all practical purposes wavelength/momentum are not quantized.

No, angular momentum can take non-discrete values. It doesn't make any sense to claim that momentum is continuous and angular momentum is not, because angular momentum is just the cross product of momentum and radius.

Both are only discrete, when the particle is in a bound state. A "free" particle can take continuous values for momentum and angular momentum.

Maybe one could try to take the whole universe or just the solar system as some kind of bound state and try to calculate quantized states for "free" particles. And there might be new physics at very high energies that would lead to quantized lengths. However for all practical purposes wavelength/momentum are not quantized.It may not make sense, but it's what QM says. Angular momentum has discrete values. Further more, angular momentum can't point in a given direction.

Unfortunately I cannot provide the math that leads to these conclusion. The departure from classical mechanics stems from the fact that angular momentum is defined in terms of position(radius) and momentum operators. So instead of L = r x p, you get ~L = ~r x ~p, where ~L, ~r, and ~p are operators.

And yes, I am talking about free particles.

I guess I have to partially retract my post: even free particles can have quantized angular momentum related to a central potential.

But this is only works, if L and H commutate. If they don't, then eigenstates of the angular momentum have no physical meaning and the angular momentum is not quantized. However defining angular momentum might not make any sense in these cases. That's a bit of a problem of angular momentum in general: It can always be defined, but there are only few cases where it makes sense. But those few cases are very important in physics.

I suspect at this point we have lost Lucy's interest...

I look forward to an impromptu demonstration of planetary quantum interference at the next meetup. :)

With Narz in NY? Definitely no interest from Lucy, given that for some strange reason a load of people think of Narz as a sex offender.

We'd all be so drunk I don't think we'd have a problem keeping her interested.

Drunk?!?! Respectable chaps like us, Rambuchan and Nonconformist? Surely not?

Cyan and Magenta are also pretty bright. It might also be due to association with the sun.

Cyan and Magenta are also pretty bright. It might also be due to association with the sun.
Best explanation in thread.

Humanity just grew up with this huge honking BRIGHT sun. Incidentaly, the sun is yellow.

It's propaganda, god shows us that yellow is bright everyday, thus brainwashing us.
The solution is obvious - invade Poland and Singapore.

2 reasons why yellow is bright:

1) reason already given which is that the "red cone" and the "green cone" have such highly overlapping sensitivity bands.

2) reason not yet given which is that the "blue cone" is far less sensitive than the other two.

Dark yellow: go into a typical paint application and make a palette entry with red=255, green=255, blue=0. you will find a delightful bright yellow. Now change that to red=128, green=128, blue=0. It looks brown to me. Therefore I conclude, brown = dark yellow.

An interesting take on the discussion of blue cones and brightness perception - the retina can be damaged far more easily by blue light through photochemical toxicity than it can with longer wavelengths. Therefore there is a strong reflexive inhibition against looking at bright blue light. When the sun is low in the sky almost all the blue is scattered by the atmosphere

I suspect at this point we have lost Lucy's interest...That's the danger of asking such question in this forum. There's high risk involved to get suck into discussion about particles and wavelenghts. :lol:

rysingsun probably is the closest.

It should be noted also that with rods blue area is more sensitive than with cones. It can have some significance towards the question if considering evolutionary aspects of it.