What people are calling “spectral violet”, as in, a particular range of wavelengths of light, is not a “color”. Color is a perceptual phenomenon which happens in people’s brains, and is several steps removed from light spectra, involving several types of adaptation and varying from person to person and context to context.
“Violet” is a type of purple or purple–blue flower. People use the color term “violet” to mean a hue between blue and purple, without specific reference to the spectrum. People get confused about this because Newton stuck the label violet on a diagram of a color wheel one time.
> The “red” signal path has an interesting additional property. As you can see above, it has a small bump of activation around the short-wavelength (violet) end of the visible spectrum
No this is bunk. That bump is an artifact of the process used for defining the XYZ color matching functions in the 1930s before anyone could measure cone cells directly, and the author is grossly misinterpreting what it means. On a linear scale the cone responses look like this https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Co...
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While we’re at it, “cyan” is a terrible generic name for a blue–green hue. Stick to “teal”.
“Cyan” is just the Greek word for “blue”, and is a technical term for the type of greenish blue ink used in 4-color printing.
Also it’s a crying shame that the RGB display color made of mixing yellowish green and purplish blue is called “cyan”, since it bears almost no resemblance to the printing color.
> On a linear scale the cone responses look like this
Regardless of whether or not the article's description of the specific mechanism is correct, it's true that humans perceive violet (~400nm) light in a way that can be simulated on a monitor using a mixture of red and blue light.
Using "violet" and "purple" interchangeably in a lot of contexts is probably fine, but it's extremely frustrating when someone uses "violet" to mean "purple" (or vice-versa) in a technical context. E.g. if I buy a "violet" photo filter, I will be extremely disappointed if it turns out to be dark magenta/purple.
> “Cyan” is just the Greek word for “blue”, and is a technical term for the type of greenish blue ink used in 4-color printing.
My understanding is that hundreds of years ago, "blue" was used to refer to what we would now think of as "cyan", and "indigo" was used to refer to what we would now think of as "blue" (0x0000FF on a computer monitor).
> Also it’s a crying shame that the RGB display color made of mixing yellowish green and purplish blue is called “cyan”, since it bears almost no resemblance to the printing color.
The colour people typically refer to as "cyan" in RGB colourspace (0x00FFFF) is the same colour referred to as "cyan" in the CMYK colourspace used for printing. I have several cyan glass photo filters (intended to cut out all longer wavelengths like red, but let shorter wavelengths pass), and they also look the same.
If you perceive 0x00FF00 on a computer monitor as "yellowish green" and 0x0000FF as "purplish blue", and especially if 0x00FFFF doesn't look like cyan printing ink to you, have you considered having the spectral sensitivity of your eyes tested? It sounds like either that's different than usual, or you grew up with a different set of perceptual colour definitions than most people.
> extremely frustrating when someone uses "violet" to mean "purple" (or vice-versa) in a technical context. E.g. if I buy a "violet" photo filter, I will be extremely disappointed if it turns out to be dark magenta/purple.
If you are buying a photo filter you should look for a chart showing what specific wavelengths of light it absorbs.
Neither “purple” nor “violet” is a technical term.
> hundreds of years ago, "blue" was used to refer to what we would now think of as "cyan", and "indigo" was used to refer to what we would now think of as "blue" (0x0000FF on a computer monitor).
0x0000FF on your computer display is not anything like “unique blue” (some blue color a typical observer would say is neutral between green and red). Arguably calling computer-display primaries “blue” is a huge mistake.
Reasonable unambiguous human-comprehensible names for the RGB primaries would be something like “orangish red” (or even “reddish orange” if you take the ISCC–NBS color category name), “yellowish green”, and “purplish blue”.
> The colour people typically refer to as "cyan" in RGB colourspace (0x00FFFF) is the same colour referred to as "cyan" in the CMYK colourspace used for printing.
The +, ◻, and × are printer’s “cyan”, (the ISCC–NBS named category for this is “greenish blue”) and the triangle shows the mixture of sRGB B and G (right at the edge of the ISCC–NBS category “bluish green”).
In a similar way, printer’s magenta is a purplish red color, whereas the 0xFF00FF on a computer display is very slightly reddish purple. The two are not remotely similar.
Notice that diagram also shows dotted lines for the NCS “unique hues” of red, yellow, green, blue, and also shows round dots for the world color survey’s color category foci.
> have you considered having the spectral sensitivity of your eyes tested?
Yes, I have normal color vision, can perfectly pass a Farnsworth-Munsell 100 hue test, etc.
OK, I acknowledge that I was in error here about RGB full-saturation green + blue being equivalent to printer's cyan, and apologize for the error. However, they are still both (in my mind) firmly in the category of "colours in the sky on a cloudless day".
I think we're going to have to agree to disagree on the rest, but thank you for teaching me some new things today.
> “Violet” is a type of purple or purple–blue flower. People use the color term “violet” to mean a hue between blue and purple, without specific reference to the spectrum. People get confused about this because Newton stuck the label violet on a diagram of a color wheel one time.
If violet is between blue and purple, and indigo is between blue and violet, what are we doing here?
But yeah, color is a weirdly cultural-specific thing. For instance, "orange" used to just be considered a shade of red. (Not sure whether it's an urban legend or not, but supposedly the term "orange" to refer to a color originates from the Dutch royal house of Orange.)
I'd heard previously that the fruit used to be called "a naranj", and through linguistic evolution that transformed into 'an aranj', and a light bit of google for 'a naranj' returns the following: https://en.wikipedia.org/wiki/Orange_(word).
>> The word ultimately derives from a Dravidian language — possibly Tamil நாரம் nāram or Telugu నారింజ nāriṃja or Malayalam നാരങ്ങ nāraŋŋa — via Sanskrit नारङ्ग nāraṅgaḥ "orange tree". From there the word entered Persian نارنگ nārang and then Arabic نارنج nāranj.[2] The initial n was lost through rebracketing in Italian and French, though some varieties of Arabic lost the n earlier.[2]
Teal is in the vicinity of #0AA, while cyan is around #5FF; there's almost as much difference between cyan and teal as between cyan and (light) blue or green.
Printer’s cyan is a color in the vicinity of #00A2CC, which is not at all close to #55FFFF.
Using the name “cyan” for the latter is very confusing. I would strongly advise against it.
If you want you can use names like “bluish green”, “greenish blue”, or “blue–green” to stay out of trouble.
If you have a blue–green color, maybe slightly on the greenish side, “teal” is a pretty safe name: people won’t misinterpret what you mean. The name “teal” can represent a quite large generic range of colors.
> Color is a perceptual phenomenon which happens in people’s brains, and is several steps removed from light spectra, involving several types of adaptation and varying from person to person and context to context.
That's one way it's commonly used. But in some contexts color is also used to mean spectral distribution.
That's the whole issue.
It's the same as "If a tree falls in a forest and no one is around to hear it, does it make a sound?". The whole conundrum only arises due to overloaded meanings in many languages.
What people are calling “spectral violet”, as in, a particular range of wavelengths of light, is not a “color”. Color is a perceptual phenomenon which happens in people’s brains, and is several steps removed from light spectra, involving several types of adaptation and varying from person to person and context to context.
“Violet” is a type of purple or purple–blue flower. People use the color term “violet” to mean a hue between blue and purple, without specific reference to the spectrum. People get confused about this because Newton stuck the label violet on a diagram of a color wheel one time.
> The “red” signal path has an interesting additional property. As you can see above, it has a small bump of activation around the short-wavelength (violet) end of the visible spectrum
No this is bunk. That bump is an artifact of the process used for defining the XYZ color matching functions in the 1930s before anyone could measure cone cells directly, and the author is grossly misinterpreting what it means. On a linear scale the cone responses look like this https://upload.wikimedia.org/wikipedia/commons/thumb/1/1e/Co...
* * *
While we’re at it, “cyan” is a terrible generic name for a blue–green hue. Stick to “teal”.
“Cyan” is just the Greek word for “blue”, and is a technical term for the type of greenish blue ink used in 4-color printing.
You can see what “cyan” is as the little x, square, and + in this picture, https://upload.wikimedia.org/wikipedia/en/e/ed/Color-map-2.p...
Also it’s a crying shame that the RGB display color made of mixing yellowish green and purplish blue is called “cyan”, since it bears almost no resemblance to the printing color.