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> 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 th

> 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.

jacobolus 8y ago
> 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. These are not close at all. Look at the chart I made in 2010, https://upload.wikimedia.org/wikipedia/en/e/ed/Color-map-2.png https://upload.wikimedia.org/wikipedia/en/e/ed/Color-map-2.p... 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.
- blincoln 8y ago
  > These are not close at all. 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.

jacobolus 8y ago

> 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. These are not close at all. Look at the chart I made in 2010, https://upload.wikimedia.org/wikipedia/en/e/ed/Color-map-2.png https://upload.wikimedia.org/wikipedia/en/e/ed/Color-map-2.p... 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.

blincoln 8y ago
> These are not close at all. 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.