Talk:Color vision

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[edit] Suggested External Link

Hi there -- I recently finished an introduction/overview paper to color vision -- it contains lots of nuggets of trivia -- you can see it at www.diycalculator.com/sp-cvision.shtml. I think it would be worth an external link -- but I'll leave that to whoever is managing this page -- cheers -- Max (max@diycalculator.com)

Looks like a good, informative site. I'll go ahead and it to external links, and others can remove it later if they'd like to. Thanks for the suggestion! delldot | talk 01:17, 11 March 2006 (UTC)

[edit] Merge

There is really no such thing as color vision kept separate from the rest of visual perception and cognition. This article should merge into those. There is already more in visual perception about the real issues here, than there is covered in this article. 142.177

I disagree that this should be moved. I think the information currently at visual perception should be moved here. I agree that colour vision is not separate from the area of visual perception, but that doesn't mean they need to be in the same article. There is a lot more to be written about colour perception so the visual perception article would end up too large anyway. Angela 21:25, Sep 17, 2003 (UTC)
Since I created this article, I feel I should give some explanation: I didn't want to try and fit everything into visual perception, which would have become enormous and incredibly complex, given the complexity of the subject. I thought it best to break up the various aspects of vision, even given that there is so much overlap in different aspects of vision.
Incidentally the section on color in visual perception is, frankly, a load of crap. I'm beginning to understand why 142 was banned in the first place, pardon my brusqueness. Graft 01:14, 18 Sep 2003 (UTC)
Pointing out specific problems with the article on the appropriate talk page would be more useful than global criticisms and personal attacks. I don't think the current stuff on colour in the visual perception article fits in particularly well with the rest of the topic and would perhaps be better on a separate page but I can't see why you're writing the whole thing off as crap. Angela 01:19, Sep 18, 2003 (UTC)
The article (visual perception) seems to have been reconstructed as a history of the meaning of the term "colour", rather than a discussion of how perception works. Sorry for the personal attacks, I'm just rather put off by 142 tonight. Graft 01:22, 18 Sep 2003 (UTC)
Those two things need to be separated. History of colour? Meaning of colour? Or something like that. I'd like the visual perception article to be more focused on the scientific/psychological aspects rather than the history. Angela 01:27, Sep 18, 2003 (UTC)
I moved it all here as it is more relevant to the Color vision page than the Visual perception page. If someone thinks what is below is rescuable, they could try putting in this article. Angela 13:01, Oct 31, 2003 (UTC)
Is there any place in this article for an alternative theory, ie Gerald Huth's website? --68.169.226.44 21:22, 21 Mar 2005 (UTC)
No. That site doesn't make any sense. Graft 22:03, 21 Mar 2005 (UTC)
Sorry that wasn't the link I meant to give, this is the actual paper. 68.169
I've read this site in some detail. At this time the idea is far too experimental to be considered informational. I am also of the opinion that this theory is easily refuted by a simple examination of the optical and mechanical properties of the eye, which are trivially measured and AFAIK do not agree with the degree of chromatic abberation required for this theory to work. Furthermore, the mathematics of waveguide effects around cone cells have been analyzed by others corrections to photopigment optical density have been estimated to account for the effect, and the author's often-cited "mysterious" effects of induced-color perception experiments by Edwin Land are easily explained by modern color appearance models. Its fun to think that 300 years of vision science is completely wrong, but it does not appear to be the case. :) Andyschm 08:12, 20 March 2007 (UTC)

[edit] Colour

In these first stages, luminosity or black-white content is distinguished from red-green hue and saturation, and from blue-yellow hue and saturation. Differences in sensitivity of these causes the perception of distinct colours, such as the bands in the rainbow, which appear to have seven distinct colours to most people. Failures to tell red from green are common in men. More shades of green can be distinguished than that of any other colour.

According to John Gage of Cambridge University, figuring out what a colour word means is just as difficult as figuring out what they were thinking: the words assigned to colour represent typically associations made in cultures, and not actual frequencies.

The word "purple", for instance, referred to a dye and dye preparation technique, not the colour that resulted, in its English origins. According to Eleanor Irwin, the word referred to the shifts in colour, rather than to the colour itself - a concept we might call glamour or shimmer. Xenophenes refers to three kinds of purple, but there are in most Greek accounts only four colours (Aristotle saw just three) in the rainbow - thus he cannot mean by it what we mean. When they do refer to it as a colour, it is a much redder colour than that we would associate.

Colour words, historically, also had many other associations. The Greek chloros for instance, could mean "fresh" or "appealing" rather than "green". Other words could be either "blue" or "dark" in either the colour or foreboding sense. Not until Plato was there any clear statement that colour was a visual quality. Aristotle was concerned with iridescence but less about differing colours, and was perhaps colourblind.

By the 5th century there was some agreement on what colour was, and that it generally represented some scale between white (all colours) and black (no colours) - building perhaps on older Greek ideas about 'men as black, women as white' although these had no implications of morality. To distinguish dark from light was far more important than to distinguish any particular hue. Irwin suggests that the bright stark light of the Mediterranean influenced this view.

The painter's way of looking at colour, pigment, was also well established by this time and developed through the Renaissance.

[edit] Visual elements of cognition

Isaac Newton's work on optics was the basis of most Western notions of colour, as it was accepted as an "objective" phenomenon. But not by everyone - George Berkeley attacked Newton's work and that of Johannes Kepler as having no defensible ontology and suffering from a serious subject-object problem. Modern views tend rather more to Berkeley's than to Newton's or Kepler's in some respects - see morphogenetic field for a related issue regarding cognition in general.

Fred Brooks, in his research in the 1980s into user interfaces for complex molecular engineering problems, determined that there were no fewer than eleven distinctions in visual cognition. These included the ability to discern about two and a half degrees of freedom in colour alone, a full degree in luminosity on its own, a full degree each of albedo, one and a half of vibrato or rhythm of undulation, three spatially (height, length and width) presumably intuited by some higher cognition - he was able to use all eleven in design of user interfaces, along with two more of force feedback, and some in audio (which according to Sara Bly, Bill Gaver and Bill Buxton's work at Xerox Europarc had six degrees).

Differentiating visual from non-visual perception is sometimes quite difficult. People usually report seeing a better picture, for instance, if they hear more robust richer sound.

Newton saw a strong relation between colour and music, and was the first to divide purple into violent and indigo as a basic colour, yielding seven that matched the five whole tones (red, yellow, blue, green, violet) and two semitons (orange and indigo). Kepler had argued that musical harmony was the basis of the universe. By the 19th century music was widely considered the highest and unifying art, in effect replacing theology and philosophy and neatly managing to sidestep much ethical tradition.

[edit] Aboriginal visual perception

Studies of aboriginal languages reveal a very wide variety of names for lights and colours, which hints at highly honed ideas of the relationship between colours and survival-critical communication. Anthropological linguistics, a branch of linguistic anthropology, is concerned with this association of culture, language, and the way sensory perception is shared.

Brent Berlin and Paul Kay in their World Colour Survey claimed that all colour vocabularies were reducible to eleven terms: red and green, blue and yellow, black and white, orange, pink, brown, purple, and grey. These are the basic colour terms, and are monosyllabic, applicable to any item, highly salient, widely shared, and not included in the range of another term. But there were as few as two such distinctions made in some languages, presumably those where there was little need to make the distinctions.

Furthermore, in every single one of the six thousand languages studied, they appear in a fixed order, black and white first, then red, then either yellow or green, then the other, and then blue. Also all have the same center - that is, we all point to the same colour chit to mean the 'best example' of say red or blue.

Munsell colours are one basis of this list of centers, but brightness sometimes merges into hues, according to Robert McClury. In effect, the distinctions we make are first brightness distinctions, which is reflected in language, and then start to divide things up.

Another proposal is that the fovea, the pit in the eye where most hue receptors are located, gets opened up through a physiological response and may only become activated when there is a need to make certain distinctions.

John Gage however refutes this view, and offers historical counterexamples - including 40 of the languages studied by Berlin and Kay where there appeared to be overrides of cultural distinctions over sensory ones - such as using one word for all of yellow and orange. Homeric Greeks, Medieval Europeans, Creek Indians, and ourselves may all receive frequencies identical to each other, but describe them in different ways based upon the cultural distinctions different lifeways force on them, and this is not separable from other linguistic or sensory distinctions, just as Japanese difficulty to say or hear "L" is fixed in early life, by lack of necessity to distinguish it from "R".

[edit] Non-human visual perception

Humans have good visual perception, apparently greater than hominids in general, as great apes appear not to be able to distinguish most colours. However, it is unclear, as the view from evolutionary psychology is incomplete and poorly tested even in humans, and apes have no languages of their own which can be investigated for colour distinctions.

Many birds are drastically more visually acute, being able to spot prey at vast distances and track it as they swoop in on it.

(moved from Visual perception, originally written by User:142.177.etc)

[edit] Birds

Regarding this passage:

Other animals enjoying three-color vision include tropical fish and birds. In the latter case multicolor perception is achieved through a single cone type. Brightly colored oil-droplets inside the cones are used to shift the perceived wavelength. Still other species have less effective two-receptor color perception systems, or simple monochromatic, single-receptor systems.

I'm slightly confused - how can birds have three-color vision with a single cone type? Is it actually "three-color" or is it a completely different non-analagous mechanism? Graft 18:25, 20 Nov 2003 (UTC)

From what I've heard, they have both different kinds of cones and different colors of oil droplets. Of course, birds differ from each other as mammals do. -phma
Indeed, some birds and fish are tetrachromatic rather than trichromatic.

[edit] See also

While the first word of the article provides a link to the article Color, I felt it desirable to mark that link in a "See also" section, because there is substantial information on color vision at that article to assist those wanting an accurate summary in the general context of theory of color. Is there any principled objection to this? It seems to me, as a relative newcomer to this whole color-and-vision domain in Wikipedia, that the domain needs considerable careful work, and disciplined re-organization. --Noetica 23:48, 5 Mar 2005 (UTC)bla bla bla bla bla yada yada yada boring........

[edit] locus geniculatum laterale?

Can anyone confirm this information that was recently added by 131.173.34.57? Or 131.173.34.57, can you WP:CITE a source? I did a quick internet search for "locus geniculatum laterale", and came up with no hits.

On its way to primary visual cortex visual information is transformed at an important relay region of the brain: the thalamus. The LGN (locus geniculatum laterale), a bunch of nerve cells in the thalamus, receives input from the eyes. The wiring of the nerve fibres from the retina on the LGN cells enables them to detect color opponencies, red-green and blue-yellow contrasted stimuli of manifold combinations make them respond vigorously. On the next stage, the primary visual cortex, cells are much more tuned to a narrow bandwidth of light, i.e. to certain colors.

I wasn't sure if the information was right because I know that LGN refers to lateral geniculate nucleus, and the initials of locus geniculatum laterale would be LGL. delldot | talk 14:10, 15 December 2005 (UTC)

I would say delete it in a few days if there is no response. PAR 14:44, 15 December 2005 (UTC)
One is obviously the Latin translation of the other, although "corpus" is far more common than "locus". This is not my field at all, so I can't really comment too deeply, but the statement that the LGN is responsible for color opponency is probably at least a little controversial. Evidence to back it up in this[1] PNAS paper from 2000, which says:
Our early evidence (1, 2) for two color-opponent cell types and one color-nonopponent cell type in the primate LGN provided evidence supporting the modified Hering-Hurvich-Jameson model of color processing. We characterized these different opponent cell types, on the basis of the color appearance of those spectral regions that produced maximum excitation and inhibition, as red-green cells (those differencing the outputs of the L and M cones) and blue-yellow cells (those differencing the S cones from the sum of L and M cones). These color terms for the cell types unfortunately persist, despite more recent evidence (10) that the LGN opponent-cell axes do not precisely correspond to the perceptual red-green and blue-yellow axes.
In other words, the LGN is at least involved in the opponent process, but there's more going on there than the text above suggests. However, at the current level at which the article treats things, this text is probably more than adequate. Graft 20:42, 15 December 2005 (UTC)
  • Fixed. Semiconscious 22:38, 15 December 2005 (UTC)

[edit] Evolution of Color Vision

I'd like to see this subject fleshed out more: When did proto-humans begin to see in color? When did the last color involved develop? Mostly because I remember an article in the local science mag which speculated that we began to see blue only relatively recently (2500-3000 years ago) because certain blue objects, like Sirius or Mediterranean sea, were described as being red in ancient texts.

Not sure about that, it would imply the Egyptians couldn't see blue though, and there is a lot of blue in their tombs I believe. Also was the sky described as being red in texts from 1000BC? --Fxer 21:27, 13 June 2006 (UTC)
This is silly. All primates have tri-color vision; it evolved tens of millions of years ago. The more likely explanation for Sirius is (a) they got it wrong, or (b) there was some other reason for their observation. Talk.origins has a page on Sirius, actually[2]. Not exactly relevant, but answers the question. Graft 23:15, 14 June 2006 (UTC)
Not all primates are trichromatic (esp. New World monkeys). In primates species, color perception is highly correlated with diet as well as diurnal/nocturnal habits. Insects are typically easier to see with dichromatic vision, whereas the spectra of leaves indicates digestibility and colored fruit (which is in some cases thought to have coevolved with trichromacy) stands out better in the presence of luminance noise found in foliage. Specific details on point-mutations and other theories are addressed in papers by Prof. J.D. Mollon and others. Andyschm 07:57, 20 March 2007 (UTC)

[edit] Article could copy from Color article

In the article on Color section Color#Color vision has: "Main article: Color vision". But there is actually more info there than there is here, which is strange. Lambiam 23:37, 11 March 2006 (UTC)

Yes, Lambiam. A few of us have put considerable effort into filling out suitable detail in that section, and the results are pretty good, I think. Most of its content could indeed be moved to this article, where it fits more naturally. I think there are several such anomalies in the articles concerning vision and colour. Noetica 23:36, 14 June 2006 (UTC)

[edit] What would seeing in 4 or 5 colors "look" like?

Find some-one who can, and ask them :~). See Color Blindness (which should be cross referenced here). Some women inherent two slightly different types of cone, giving them 4 color peaks instead of 3. Actually, you get the opposite kind of answer you get if you ask a "color-blind" guy: the world looks normal, but colors are more (less) interesting 150.101.166.15 00:20, 4 April 2007 (UTC)

If humans can see Red/Blue/Yellow, what would the 4th and 5th colors some tropical fish/birds can see do for them? Are there colors in the rainbow that humans can never know about or something? --Fxer 21:25, 13 June 2006 (UTC)

That's a fine philosophical question, Fxer. But a good question to ask before that one is this: What do the colours we do see look like? Some say they look like something, others say that the question itself is faulty, since colours aren't really the right sorts of thing to look like anything! See Qualia for discussion of this matter, and some links. By the way, how many colours do we "see in", in fact? (Whatever ones they are, don't expect them and a few others that we don't see to be "in the rainbow"! They are fabricated in our own brains.) Some would say that normal human vision involves four basic ("primary") colours, not three. This is well discussed in a couple of places, including at this part of the Color article. Read about opponent processes, in particular. Noetica 23:48, 14 June 2006 (UTC)
This is easily answered: the weakest part of our color vision is the blue portion of the spectrum, which has the weakest frequency-range overlap with any of the opsin receptors in our eyes. Adding more color resolution would simply allow us to resolve colors with more accuracy, i.e., you'd be able to distinguish reddish-orange from reddish-reddish orange better, or indigo from indigo-violet, etc., depending on what part of the spectrum gets the additional coverage. In fact, some women are polymorphic in an opsin allele which allows them greater color resolution in the green part of the spectrum. Graft 02:14, 15 June 2006 (UTC)
Um, sorry Graft. The matter of greater powers of resolution in some part of the spectral range is not the same as the matter of how things would look (to a tetrachromat, say). Suppose most of us were dichromats, with only the M cones and the L cones, and just a few exceptional people were discovered to be trichromats (equipped also with S cones). Suppose also, quite naturally, that only these rare trichromats had colour experience like ours, and experienced the full range of colours that we do. Then, finally, suppose someone posted a question relevantly like Fxer's above: "What would it be like to experience the world with a third type of cone added, so we had extra colours?" The correct answer would have to address our actual colour experience, with our full range of colours that are denied to the majority – the dichromats. It would not be enough simply to mention better discriminations in a certain spectral range, in terms of the more limited colours that dichromats experience. (And, leaving tetrachromats' experience, what can we even say about dichromats' perceived colours? Very little!) Similarly, your answer above falls down. (Tricky stuff!) Noetica 07:54, 15 June 2006 (UTC)
I agree, more or less, with Noetica. We can never really understand completely the experience of a tetrachromat any more than we can experience four dimensions visually. The closest we can come to understanding the experience of a tetrachromat (a person who has four separate color receptors) is to look at the case of a trichromat trying to explain their experience to a dichromat, since we can experience what it is like to be a dichromat. To a tetrachromat, things would look more "complicated" and yes, the difference in two colors might be apparent to a tetrachromat, but not a dichromat (but not necessarily). But even more, its not that a tetrachromat's resolution would be increased (i.e. a tetrachromat would resolve two different colors that was below a trichromats resolution) but that a tetrachromat would see two different colors in some cases where a trichromat would see only the same color, even if they both had perfect, or infinite resolution. PAR 12:50, 15 June 2006 (UTC)
I don't see how it's useful to say we'll never fully understand someone else's subjective experience. I mean, duh. That's why it's a subjective experience. But I fail to see how I've described it is inaccurate. This is how it works with actual dichromats, people with red-green color blindness - they're simply unable to tell apart colors that others (trichromats) can distinguish easily. Graft 14:59, 15 June 2006 (UTC)


I wasn't disagreeing, but I just wanted to make sure we were talking about the same thing. There are two different issues here, the inability to resolve two colors because they are the same, and the inability to resolve two colors because they are so close to being the same. Suppose there are two light sources with different spectral distributions, A and B. A dichromat may not be able to distinguish between the two, because to the dichromat they may be exactly the same color, while a trichromat may easily distinguish between the two, because to the trichromat they are not the same color. On the other hand, we could have another two different light sources C and D. The dichromat may be able to distinguish between the two because they are different colors to the dichromat and the dichromat has a high sensitivity to the difference. They may be different colors to the trichromat as well, but the trichromat may have less of an ability to distinguish colors than the dichromat, and may not be able to resolve the difference between the two and so would call them the same. When we say that a tetrachromat can distinguish colors that a trichromat cannot, we have to be clear that its not because a tetrachromat has an increased ability to distinguish between two colors that both agree are different, its because the tetrachromat sees two different colors while the trichromat only sees one, no matter how good they are at resolving differences. PAR 23:40, 15 June 2006 (UTC)


If you can't tell two colors apart, they are the same to you. It doesn't make any sense to say that two colors are different to some individual, and yet they are unable to distinguish between them. Graft 01:35, 16 June 2006 (UTC)
That is not true. You can have three different spectral distributions of light, A, B, and C. It may be the case that A and B look the same to you, and also B and C look the same to you, but A and C do not look the same. Thats because the difference between A and B is so small you can't tell the difference, and the same with B and C, but the difference between A and C may be the sum of the differences A-B and B-C, which may be large enough for you to see the difference. Just because two colors look the same doesn't mean they are the same. Its like if I can distinguish two points that are 3/100 of an inch apart or more, then two points A and B that are 2/100 of an inch apart I cannot distinguish. Same with B and C. But if the points are arranged as A B C, then A and C will be 4/100 of an inch apart, and I can see the difference. Saying A and B are the same point just because I can't detect their separation is wrong. What I am saying is that for a person who is a "unichromat" (can only see shades of one color), the colors they can see may be arranged on a line. They may have extremely well developed abilities to distinguish differences on that line, but its still just a line. For a dichromat who can see two colors, the colors they can see may be arranged on a 2-dimensional surface. They may have poor ability to sense differnces between colors on that surface, but it's still a surface. Two colors on the dichromats surface may collapse to one point on the unichromats line. I just want to be sure that we understand the difference between being able to sense the difference in two colors because they are too close together on the line, or surface, or whatever, and being able to sense the difference between two colors because you have more dimensions and can separate more colors than someone with fewer dimensions in their color space. PAR 15:39, 16 June 2006 (UTC)
You're saying true and useful things I think, Graft. But we all have to be careful not to fall into certain very pervasive errors when we blend talk of peceptual discriminations and the subjective experiences that accompany those discriminations. Here's a thought experiment that might prove useful:
Imagine that a baby is born with a strange (and hugely unlikely!) set of genetic mutations with these effects only: the pigment in each of the three cone systems is altered so that the three sensitivity curves are shifted uniformly in the "L" (long-wave) direction. (Assume also that the transparent tissues of the eyes are still transparent to the infrared wavelengths that this baby can see and we can't, OK?) Now, the baby grows up, and it slowly becomes apparent that things look different to her than to the rest of us. She can make some discriminations that we can't, and can't make some that we can. Also, she can see in some pure infrared light when we see nothing at all, but she lacks our ability to see in certain light that she might call "ultraviolet". Three questions:
  1. What is her colour experience like (ignoring the fact that particular things might look differently coloured)?
  2. Does her range of colours differ from ours?
  3. Is the structure of her colour space different from ours?
Three answers:
  1. Just the same as ours.
  2. No.
  3. Not at all. Her blue will still be complementary to her yellow; her yellow will be more similar to her light orange than to her dark green, and so on.
If you follow all that, and can see why these answers are good, that's fine. If you disagree with my answers I'll say more, if you like. Noetica 01:52, 16 June 2006 (UTC)
Well, to return to the first question: humans do not see red, blue, yellow, but red, blue, green :o). But this is a minor detail. PAR is right in that a tetrachromist would possibly have an extra colour dimension. The answers above moreover disregard the possibility that adding a fourth or fifth cone type might well lead to a radical jump in qualia experience, so that a complete new set of colours would be perceived. This is likely as adding one new cone type would lead to sixteen possible stimulus combinations, in stead of eight as with trichromats, fourteen of which possible non-black and white qualia. A corresponding qualitative colour space would need a four-dimensional representation and include a whole new class of extraspectral colours: those with three non-continuous stimulus combinations.--MWAK 10:11, 12 July 2006 (UTC)
To run with this dimension analogy, you're assuming that a new color receptor acts like a new orthogonal basis. This is not true; the new "dimension" it creates might lie very much in line with an existing one, as in the case where I add a very slightly different, shifted green color receptor. Big effect with respect to greens, but not much elsewhere. Remember that you're not really talking about an actual space with independent axes, here. Graft 12:12, 12 July 2006 (UTC)
Well, it might. But then it might not. In that case a spatial representational model would demand a four-dimensional colour space. Whether the receptor is only "slightly shifted" is not decisive, though it can be indicative. Using spatial models is indeed highly problematic. A stimulus combination matrix makes my point perhaps even better :o).--MWAK 16:24, 12 July 2006 (UTC)
While we can't say what it would look like in a creature's brain, I think we can say that if a visual system had more receptor colors, or even had the same number of receptors but tuned to substantially different wavelengths, then what we view as "accurate color reproduction" would not look anything like the original object. In general, two colors that we see as "identical" need not look identical to the creature, and potentially vice versa. So color photos, color television, RGB images: all of these would be useless to the creature, and it is not even possible to convert RGB images into a suitable form. Interior decoration would be difficult. Notinasnaid 10:44, 12 July 2006 (UTC)
MWAK, you wrote: humans do not see red, blue, yellow, but red, blue, green :o). But this is a minor detail. In fact the nature of the brain's colour processing is such that we do, in a very important sense, see in four colours: red and green (one pair of opposites) and blue and yellow (another pair of opposites). For discussion of this see especially the relevant section in Color. Much of the discussion right here is mixed up, because a proper distinction is not being made between: 1) colour as a feature of our experience, determined most of all by the ways our brain processes input from the eyes; 2) colour as coded in immediate output from the three cone systems in the retinas; 3) colour as an objective and external feature of light (and perhaps of objects). Until we have clarity concerning this three-way distinction, and rigorous use of terms thereafter, such discussions as the present one will be idle and unilluminating! (For example, gaining an extra set of cones, with different response to wavelengths, would be neither sufficient nor necessary for new qualia – if talk of qualia makes sense at all, which is in fact eminently disputable. Nor is it sufficient for gaining new discriminatory ability. Understanding all this calls for careful use of terms, and careful distinctions of the sort I have just mentioned.) Noetica 03:52, 13 July 2006 (UTC)
In a general sense I fully agree. However we might disagree on the details :o). I would say that:
  1. There is good empirical evidence that there is colour opponency.
  2. There is no good evidence there is no higher (than that of colour opponency) level processing below the conscious level.
  3. There is strong evidence there is such higher level processing.
  4. There is no good evidence there is isomorphy between colour opponency and the structure of the qualia.
  5. There is strong evidence there is no isomorphy between colour opponency and the structure of the qualia.
  6. The quallia are simply what the colour terms mean in our natural language.
  7. The natural language has primacy in relation to scientific discourse.
  8. Eliminativism regarding qualia is utterly incoherent and deeply irrational (or, if you're lucky, just plain stupid ;o).
--MWAK 18:03, 13 July 2006 (UTC)
MWAK, I have not exhaustively gone through what you gave written immediately above. But I can't see how it connects, at certain points, with what I said earlier. Precisely where are you disagreeing with me? I had written this, in response to you:
...you wrote: humans do not see red, blue, yellow, but red, blue, green :o). But this is a minor detail. In fact the nature of the brain's colour processing is such that we do, in a very important sense, see in four colours: red and green (one pair of opposites) and blue and yellow (another pair of opposites).
Let me elaborate a little. Note that I was very circumspect in how I worded things: ...in a very important sense.... I do not claim that we do unequivocally see in those four colours. I merely say that the matter is complex, and that to make any progress we need more rigour. What is easy to show, however, is that we do not, in any respectable sense, see in red, green, and blue. Even the three cone systems are not maximally sensitive to single-wavelength light that is seen as red, green, and blue, respectively. (See Color, in which there is discussion of the misleading names applied to the L-, M-, and S-cones.) The fact that we are able to induce the whole range of colour experience with three single-wavelength sources (seen individually as red, green, and blue) shows nothing. Other single-wavelength sources can do the same. As for the elimination of qualia, if we had time you could show me your attempt at refuting Dennett's classic Quining Qualia, and I could respond in his defence, since I do not regard Dennett as "utterly incoherent", or "deeply irrational", or "just plain stupid". Alas, however: I for one do not have the time. Noetica 02:41, 14 July 2006 (UTC)
It is certainly simplistic to say we see in red, green and blue (but then simplism was what I strived for :o); still I would hold it is a reasonable approach of a mechanism that might well be much more fundamental than colour opponency. As regards Dennett, I would say that much of his excellence as a writer lies in his ability to make you forget by the brilliance of his style how poor his reasoning really is. He certainly isn't stupid; whether we must call him incoherent, irrational or simply a charlatan depends on the level of charity we care to apply. If it is rigour you want, in Dennett it is not to be found. But you impress me as being an uncommonly intelligent person; allow yourself to consider the possibility that Dennett is wrong and soon you will be able to refute him without my help ;o).--MWAK 06:36, 14 July 2006 (UTC)

[edit] What is "red" "blue" "green"

I think it should be noted, scientific or not, that what one see as "red" may not be that same color to another viewer. Color, I believe is relative. As relative as a group of people eating Mexican food together; for one, it is too spicy, another not spicy enough, and a third just right. I have also noticed while playing pool with my father, who is color blind, at times shooting with the cue ball (white), 1 ball (yellow), and 2 ball (blue). Should something be added for the individual perception of color?? --Ben414 17:40, 3 August 2006 (UTC)

If you can source it. :) The light we see is not relative (it has a fixed and definite frequency spectrum and power) but, yes, the perception of it is relative. Similarly, the spicyness of food is perceived as different but it has a fixed and definite quantity of capsaicin (same way with mint and menthol). Red has a wavelength range of 625-700 nm but that's derived from how we see that range of light. The definition of red would change if the cones in our eyes saw different band of frequencies. Cburnett 16:34, 1 December 2006 (UTC)
Actually, I have read somewhere that while the borderline between e.g. green and blue may differ from person to person, culture to culture, or language to language, the colors in a complete spectrum identified by not-colorblind individuals as the "ideal" or "typical" red, green, blue and yellow are nearly universal - whatever the reason. The most notable exception seems to be that some languages do not have words for all four colors; e.g., "grue" (green-and-blue) may be one, in which case the "typical" grue coincides with either typical green or typical blue.
By the way, I think most people will agree that those four color names (red for blood, yellow for the sun, green for chlorophyl, and blue for the sky) somehow represent quintessential colors (as opposed to color names like turquoise, orange, lavender, etc.), though theory involves only three primary colors because the human eye has three types of color-sensitive cells. Can anyone explain this three-or-four colors issue? Or have I already done so, naming what perhaps are those four colorful things that are most important for hunter-gatherers?--Niels Ø 17:14, 1 December 2006 (UTC)
I have just noticed that some of these issues are adressed above; see e.g. #Aboriginal visual perception.

[edit] Unperceived colors in monitors?

Is there any rational behind the commercial sayings that some RGB based monitors (of a lower quality) can not generate All of the possible colors the human eye can preceive? Does this relates to anything more than a commercial aimed at getting us to buy a newer screen? Maybe it relates to some undetectable "color resolution" ? (more than 16384 shades of green is really too much for me..)—The preceding unsigned comment was added by 80.230.160.5 (talk • contribs) 10:59, 28 August 2006 (UTC).

No, all standard monitors are greatly deficient. E.g., a saturated green cannot be shown and the cyan is very, very poor. At the extreme ends of the spectrum, the red isn't much either and the violet is simply lamentable. However in the latter case this is on purpose: a saturated violet would be much too energetic and thus lead to eye damage. The remarkable thing is rather that despite this impoverished gamma, people still have the illusion that colour-wise they are looking to a pretty normal representation of reality :o).--MWAK 17:25, 13 September 2006 (UTC)
You mean to say gamut, not gamma. It could be said that for a typical display most out-of-gamut colors are highly saturated, and since highly saturated color is rare in natural scenes, its absence is not readily noticed by the observer. It may also be worth noting that comparisons of display capability by looking at the area of the gamut in chromaticity coordinates are nearly worthless, since such analysis makes no consideration for contrast ratio or brightness (both crucial components of a color appearance model), it cannot be an accurate measure of color quality. Andyschm 07:24, 20 March 2007 (UTC)

[edit] Mathematics of color perception

Would anyone like to properly format this section? Commander Nemet 03:36, 5 April 2007 (UTC)

[edit] Red cone colour perception

Something that confuses me here: this article states that the red cone is most sensitive in the "yellow" part of the spectrum, but the table later on states that this cone is stimulated most by "yellowish-green". This seems to be a contradiction. Since the "colour" assigned to each part of the spectrum is just based on what our eyes eventually see (i.e. it's the end result not the stimulus), then surely there can only be one colour we see at 564 nm? So is this yellow or yellowish-green? (unsigned by 10:31, April 7, 2007 86.148.113.162).

You are referring to the L-cone. It is confusing to refer to it as the red cone, as it is not most responsive to red as you pointed out. The yellow color is generally considered to be at 575nm. The sensation of yellow is caused by the zero-crossing of the L-M opponent functions (different between L-cone and M-cone). So judging by this, the description of yellowish-green is accurate; 564 is just a bit off 575nm, towards the green side. Notice that you shouldn't take the S/M/L cone chart in this article and do subtraction to try to get the L-M curve; this graph is normalized. This article and many other color-related articles should be greatly enhanced. I'll probably work on that in a month's time. Fred Hsu 21:44, 7 April 2007 (UTC)

Thanks for clearing that up. And I did notice the graph was normalized, but I assumed the normalization was equal for all three curves, keeping the proportions the same. Now you've pointed out that yellow occurs at the zero-crossing of L-M, I guess I can see why the colour yellow is a relatively small part of the visual spectrum!

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