...along with Quarkhead, apparently..... You're just jealous, because you can't climb a tree in a straitjacket. Please Register or Log in to view the hidden image!
You seem to be confusing perception with an abstraction, you call it "physiology". What is this you speak of? And please do not condescend to me you patronising prick.
Colors are not additive. Researchers sometimes classify languages according to their color terms - a "grue" language is one that uses the same term for what English speakers separate as "green" and "blue", for example: https://www.psychologytoday.com/us/blog/talking-apes/201502/fifty-shades-grue
Ya know, anyone who takes offense at being corrected had best stay off internet fora. I have made mistakes here - we all have. Suck it up and give thanks. Or is this beneath your dignity?
Dignity? Iceaura? Anyway what mistake did you make? The various ways of obtaining color are frequently referred to as additive and subtractive.
Please note, this quote is from Wikipedia; but it is accurate (I know this, because I know about Helmholtz and Young). Suck it up. --https://en.wikipedia.org/wiki/Additive_color
What on earth I'm talking about is the three-dimensional Euclidean space, the abstraction, of color vision in humans. It would be two dimensional if humans had only two types of cone cells. Or if you only considered two cone-cell types instead of three in the abstraction (additive color model).
Below is an image I made showing the RGB (Red Green Blue) additive color model, which appears as if colored spotlights are overlapping against a black background: Please Register or Log in to view the hidden image! And below is another image I made showing the CMY (Cyan Magenta Yellow) subtractive color model, which appears as if colored sunglass lenses are overlapping against a white background: Please Register or Log in to view the hidden image! In both images, the primary colors are represented by the three circles, and the secondary and tertiary colors can be found in the overlapping areas.
It's the quantitative slash technical-descriptive meaning of color (where colors are merely identifying labels attached to wavelengths/frequencies or physical affairs) that should qualify here. Since Galileo removed the everyday, phenomenological significance of "color" from physics centuries ago (primary/secondary properties distinction). So technically, the latter shouldn't be applicable to physics in isolation from other disciplines, although probably nobody cares or is prissy about fine print. For instance: Imagine that the visible range of electromagnetic radiation consisted of stories rather than waves. One of its stories makes you sad, another happy, yet another angry, and so forth. Those are feelings generated by your analysis (reading, interpretation, processing) of the stories. Accordingly, you wouldn't want to reference or ask about feelings (i.e., the experienced, qualitative or self-evident meaning of color) in physics because that's at least psychological territory if not also biological sciences offering explanatory correlates to such in the brain and nervous system. Yes, bodies or objects "out there" do feature the qualitative meaning of color that arises when they are illuminated (not in darkness), but the external environment ("out there") that we're experiencing is a manifested representation or simulation outputted by the brain or at least corresponding to areas of neural operations. Resulting in our commonsense realism beliefs that the world is the way it appears. Yet it is okay to still call that product a "public world" rather than a purely personal one due to the rest of humankind representing it the same way (barring specific individuals being afflicted by clinical conditions and substance intoxication compromising the results). But what the original or super-mental version of existence is actually like outside your "head" is something weird and abstract like quantum fields, or one of the competing quantum gravity models, or entangled qubits producing a spacetime hologram, or whatever oddball idea some corner of theoretical physics is cranking-out as a current, hot item. Not that any of it is literally the case or an uncontested "winner" for the metaphysical counterpart of the experienced "external reality". However, one chooses scientific realism over commonsense realism when residing or operating in the context of a physics-based worldview. Rational, symbolic descriptions of existence outputted by inferential activity in conjunction with experiments are brain products, too. However, it's a long tradition going back thousands of years to pretend as if they are not. Pretend that an intelligible version of the world is a mind-independent one or archetypal instead of ectypal, because there isn't another option besides blankness, inconceivablity, ineffability. When they work, the rational representations allow us to manipulate the manifested environment in new ways, just as the pre-scientific commonsense appearances did in their own limited way for ages beforehand. Stephen Palmer: People universally believe that objects look colored because they are colored, just as we experience them. The sky looks blue because it is blue, grass looks green because it is green, and blood looks red because it is red. As surprising as it may seem, these beliefs are fundamentally mistaken. Neither objects nor lights are actually “colored” in anything like the way we experience them. Rather, color is a psychological property of our visual experiences when we look at objects and lights, not a physical property of those objects or lights. The colors we see are based on physical properties of objects and lights that cause us to see them as colored, to be sure, but these physical properties are different in important ways from the colors we perceive.
So again, what is color depends on whether you mean physical light which is (perceived to be) colored, or you mean the perception of color. How we perceive colors is obviously strongly connected to how we design and build color displays. How modern display screens are designed and made explains most of the "requirements" of human color perception. Color psychology, or how colors make us feel, is in a different category to what we see and the mechanisms we have of generating images.
You appear to have confused me with somebody Quarkhead was replying to, probably arfa brane. This obsession of yours is interfering with your reading comprehension. Colors are not additive in the mathematical sense you require for this: This is seen directly in the fact that different cultures perceive different colors (there is no consistent or definable set of dimensions in the proposed space - its dimensionality varies between 2 and 20 or more); indirectly in the fact that combinations of colors yield widely varying results depending on how the colors are generated, what values of saturation etc they possess, in what circumstances they are viewed, and in what manner they are combined; and mathematically in that there is no distance function or "inner product" validly defined on a "space of colors". The short version: you don't have a vector space of colors, and you can't choose consistent scalars from the space you have. You do have a vector space of wavelengths, and you can use it to predict with reasonable accuracy what colors a given person will observe in a given situation (with careful attention to human physiology and the context of perception: https://www.syfy.com/syfywire/another-brain-frying-optical-illusion-what-color-are-these-spheres ), but Hilbert spaces do not vary depending on what kind of notebook the mathematician writes their findings in, or in what circumstances they are being discussed and perceived.
Do you agree with the following: Do you also agree that a "color distance" function is just a color-difference function? That is to say, there's a distance (subjective) between two colors like red and blue? ed. and of course, there's a choice for red and for blue, but one that the average human would agree is a pair of colors, one red the other blue?
Sure. As long as it refers to something reasonable by "physical color", anyway (I took it to mean wavelengths and combinations of wavelengths in the ER spectrum) That refers to wavelengths, right? The "visible range" is a range on the ER spectrum, in other words - violet in the 400s, red in the 700s, many colors missing (they are not "pure"). https://www.thoughtco.com/understand-the-visible-spectrum-608329 As I posted: That's not the same as a vector space of colors, which as far as I can tell cannot be defined. Subjective distances do not a Hilbert space make. You need a mathematically specified, intersubjectively invariant, "inner product" - rigorously defined over the entire space. One - not four or five, or dozens, or different ones depending on who's asking. The "physical" distance between red and blue as perceived, rather than "physical", colors, for example, will depend on how the perceptions were generated, who is perceiving them, and the exact manner of their presentation to the human perceiver. https://www.thoughtco.com/understand-the-visible-spectrum-608329 Consider what the distance function would have to be that accounted for the optical illusion I linked above - in which one identical wavelength combination presents four or five different colors, no two of which are equally "distant" from the "physical color". Or consider the fact that most Westerners see violet as closer to red than green is. Or ponder this: https://micro.magnet.fsu.edu/primer/lightandcolor/humanvisionintro.html That's violet, green, and yellow, on the "physical color" spectrum. Or if you are Japanese: grue, grue, and yellow; if Russian indigo, green, and yellow; if a member of certain tribes: grey, grey, and white; and so forth.
--https://en.wikipedia.org/wiki/Color_vision. But it makes sense to establish a standard map between these spaces; if you want to sell TVs. You need to make assumptions about how those cone cells respond; one quite reasonable assumption is that this response is independent of culture, or religious belief, say.
But Euclidean 3-space is a vector space and there's a map from the Hilbert space (frequencies or wavelengths) to it --https://en.wikipedia.org/wiki/Color_vision We want colors to be elements of a vector space, congruent to \( \mathbb R^3 \). It has to be able to accommodate the absence of color (black is the absence of visible light), and the color white. Black is easy: any color with no magnitude is black. White is defined as the (algebraic) centroid of the simplex, which is more technical but not that hard to understand. This though, is where the output of those white light LEDs lives, mathematically speaking. Does anyone else here understand how these LEDS emit light that "appears" white, to the average human?
Wavelengths again. Why? Like I said, repeatedly, above: You do have a vector space of wavelengths. It's colors you can't describe as a vector space. And if you deal in wavelengths, "spectral colors", etc, you can not only create a working map, you can set it up as a vector space. If you deal in colors as perceived and named by humans, you can't do that. None of those maps will account for the optical illusion I linked above, for example: a single wavelength combination - one vector in the proposed vector space - that delivers several different colors to human perception. There's no way to formalize that as a vector space, and no way to formalize a distance function (an "inner product") over whatever space you do come up with that includes any one vector's perception as several different colors. Black is one of the most difficult colors to produce on a screen - salesmen will sometimes brag about the quality of the black a particular brand of screen can deliver, as a selling point. You don't need to make assumptions - you can measure the cone cell response. It's been done. So?
Is that good news or bad news for display technology? You're saying I can design and manufacture an ink printer as if the color space is a vector space, but not if a human looks at a colored printout? (?) Likewise I can manufacture a LED display using some standard for the color space, but as soon as light leaves the display I can't . . .
And yet, this optical illusion might be produced from a particular color display, with an underlying vector representation (a set of binary strings).
