In the early 20th century Albert Munsell did a series of empirical studies to determine exactly how people see colors relative to one another. The results are expected, but fascinating.
Color wheels are wrong? How color vision actually works
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Re: Color wheels are wrong? How color vision actually works
#22It's interesting that Red/Green and Blue/Yellow colorblindness correlate to the opposite color pairs that Jason points out. Does anyone know why this is? Are these types of colorblindness related to a deficiency in the filters (#s 1 and 2) he describes?
Re: Color wheels are wrong? How color vision actually works
#23I wish I could upvote this twice. I hadn't realized that our actual perception of color was so filtered from the physical spectrum. I find it incredibly fascinating, from a philosophical perspective, that there are literally color combinations (i.e, greenish-red) that, despite lying within the physical spectrum to which our eyes are sensitive, we cannot see , cannot even imagine.
The thing that will really blow your mind is are there things that are red, or a group of things that have a common appearance that our minds just label "red." And what if what if the signals that reach my brain when I view "red" are shifted one to the left on the color wheel? The gradual perception of color change would be perceived but we would be looking at different colors even though we both agree that it is "Re…
> The thing that will really blow your mind is [...]
Re: Color wheels are wrong? How color vision actually works
#24This article tries to sensationalize and obfuscate something that is pretty simple in reality. RGB are the primaries in light. By mixing these three colors you can create any color the human vision system can perceive (yes, because of tristimulus). When white light hits a material, some of those RGB wavelengths are absorbed (subtracted). RGB - GB(Cyan) = Red, RGB - RG(Yellow) = Blue, RGB - RB(Magenta) = Green. Thus,…
Can you explain why your statement "pretty simple... RGB are the primaries in light" is true, his explanation in his article "complex... RGB is just a rough approximation" is false? He gives a plausible physiological explanation.
Re: Color wheels are wrong? How color vision actually works
#25I find the CIE Standard Observer graph enlightening: http://en.wikipedia.org/wiki/CIE_1931_color_space#Color_matc...
As far as I understand this, the red function, which corresponds to the red receptors in a typical human eye, reacts mostly to high wavelengths, but also has a small spike in the lower end of the spectrum. This explains why the violet end of the spectrum looks similar to red to human eyes, and this is probably why color wheels seem so natural. After all, a color wheel is almost the same as rainbow that wraps around.
I also find it fascinating that the CIE color space was defined as early as 1931.
Re: Color wheels are wrong? How color vision actually works
#26Why does he conclude that we need 4 primary colors? He knows that our eyes have three kinds of 'sensors', which roughly correspond to [R, G, B]. How the brain processes the initial perceptions, allegedly [R-G, (R+G)-B, R+G+B], doesn't change the fact that you can approximate all colors by mixing quantities of R, G and B.
What I'd find more interesting is a proposal (or a mention) of a color space that's based on what are, according to him, the 'computed' values. Something like NTL (tiNt/Temperature/Luminance), where N is R-G, T is (R+G)-B, and L is R+G+B. (The names 'tint' and 'temperature' are taken from photo editing software, as they are the only tools I can think of that come close to this system.)
Re: Color wheels are wrong? How color vision actually works
#27 Artists get it wrong
Oh, and some kind of talent.
Re: Color wheels are wrong? How color vision actually works
#28This article tries to sensationalize and obfuscate something that is pretty simple in reality. RGB are the primaries in light. By mixing these three colors you can create any color the human vision system can perceive (yes, because of tristimulus). When white light hits a material, some of those RGB wavelengths are absorbed (subtracted). RGB - GB(Cyan) = Red, RGB - RG(Yellow) = Blue, RGB - RB(Magenta) = Green. Thus,…
Can you explain why your statement "pretty simple... RGB are the primaries in light" is true, his explanation in his article "complex... RGB is just a rough approximation" is false? He gives a plausible physiological explanation.
RGB is pretty rough, you can clearly see from the graphs in this article, https://secure.wikimedia.org/wikipedia/en/wiki/CIE_1931_colo... how "fuzzy" all those colors are.
Re: Color wheels are wrong? How color vision actually works
#29>And magenta? It comes from full R and B with no G, activating Filter #1 full-positive, Filter #2 at zero.
This doesn't seem right to me. If the second filter were at zero, you should have a pure red and not something with blue content in it like magenta clearly has.
I think he may be representing the second filter as R+G-B, when R+G-2B would make more sense. The latter system shows FFFFFF as being neutral on the yellow-blue axis, while the former erroneously puts it in the yellow region.
Re: Color wheels are wrong? How color vision actually works
#30This article tries to sensationalize and obfuscate something that is pretty simple in reality. RGB are the primaries in light. By mixing these three colors you can create any color the human vision system can perceive (yes, because of tristimulus). When white light hits a material, some of those RGB wavelengths are absorbed (subtracted). RGB - GB(Cyan) = Red, RGB - RG(Yellow) = Blue, RGB - RB(Magenta) = Green. Thus,…
> something that is pretty simple in reality
It’s not that simple: explaining it properly takes dozens if not hundreds of pages.
> RGB are the primaries in light.
This depends on what you mean by “primaries”. As far as I can tell, your definition is based on common color reproduction technologies, rather than the physiology of human visual perception. That’s fine, but recognize then that the “primaries” chosen for practical use are constrained by economic factors, &c. The three best lights for additive color reproduction are indeed R (an orangish red color), G (a yellowish green), and B (a blue-violet color): this is because those are the colors which maximize the differential responses of different cone cells, as can be seen in this diagram in Hunt’s book The Reproduction of Colour: http://i.imgur.com/ZOdZc.png Of course, such narrow-spectrum sources are not economically/technically feasible, and so instead a typical computer or television uses lights like these: http://i.imgur.com/JHeGa.png By contrast, a typical subtractive system uses primary dyes like these: http://i.imgur.com/qri1f.png (the colored lines on the charts are the reflectances at various concentrations)
You cannot reproduce any color the human visual system can perceive through just three primary lights: every display system has a “gamut”, and for example computer displays have great difficulty displaying saturated blue-green colors.
As Hunt summarizes,
“It will be realized that these three expedients cannot correct for the fundamental limitations of the process, which spring from the nature of the colour mechanism of the eye and the shape of the spectral absorption curves of the best available cyan, magenta, and yellow dyes. What is claimed for modern subtractive processes is that they produce pleasing colour pictures, and that the inevitable inaccuracies are balanced in such a way as to be least noticeable.”
> The "four color" wheel he lists at the end is not wrong, it's just silly: you could pick any points on the wheel and their opposites and have the same thing.
This is not true. Color opponency and the specialness of the so-called “unique hues” have had a great deal of scientific literature about them (physiology, psychophysics, linguistics, etc.), and no, you could not just pick any four arbitrary points. Of course, there’s some learned/cultural component to people’s color categorization too, and there are individual physiological differences, so there’s inter-observer disagreement on precisely what color is “unique red”, etc. But it is indeed true that any color can be described as some combination of red, yellow, blue, green, white, and black: this is Hering’s theory of color vision, the inspiration for the Swedish NCS system, based on decades of rigorous measurements in the 40s–70s.
The current scientific consensus is that color vision can be modeled in a simple way with 2 stages: (1) trichromacy of 3 cone responses, (2) higher-level opponent mechanism. There are many more complicated effects beyond that, and it’s essential to consider adaptation, but those 2 cover the basics.
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All of that said, I’m not completely satisfied with the original essay either. It’s pretty fluffy and hand-wavey, and the jokey language gets in the way. Conflating long/medium/short cones with red/green/blue colors is dangerous because it hides what’s really going on. I wouldn’t, as the author of this article does, call the red–yellow–blue–green anchored hue circle “proper”; there are other equally valid organizations, such as the Munsell system’s, which aims for perceptually uniform hue spacing. Still, on the whole it’s on the right track.
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I’m sorry that the Wikipedia articles about these topics aren’t clearer and more comprehensive, or I’d point you there. As the article says, the best resource online is Bruce MacEvoy’s handprint.com, but several books have excellent explanations. If you’re interested and MacEvoy’s site doesn’t clear things up I can suggest where to look in the library.