8 ms·

This has long been a pet peeve of mine. I don't disagree with it but the colors shown in the article aren't violet, they are all shades of purple. Spectral vio

This has long been a pet peeve of mine. I don't disagree with it but the colors shown in the article aren't violet, they are all shades of purple. Spectral violet is outside the gamut of most RGB color spaces, including sRGB, Adobe RGB, Pantone, CIELAB, etc. Monitors also wouldn't be able to reproduce it anyway. The CIE 1931 curve showing a bump in red inside the blue is misleading I think. It does not represent how the cones react (the article says so in small print). The L cones aren't excited at all when pure blue or indigo or violet light hits them. The graph was built to find the best RGB primaries to use in order to best "emulate" how we interpret colors, so I think it actually already encodes our bias and general lack of skill at distinguishing violet from purple. Similarly many people don't really make a distinction for cyan and just call it blue or green when they see it.

NikolaNovak 8y ago
What would be the best way to get the true spectral violet then - a paint chip from hardware store? Also, do you by any chance have a handy link to an actual graph on how cones react to various spectra of light? Many thanks!
- tgb 8y ago
  A prism, probably.
- ddeck 8y ago
  >do you by any chance have a handy link to an actual graph on how cones react to various spectra of light? I think you'll find everything you need here: http://www.handprint.com/HP/WCL/color1.html http://www.handprint.com/HP/WCL/color1.html and elsewhere on the same fantastically web 1.0 style site[1]. Bruce Macevoy is an artist with penchant for color theory. [1] https://www.handprint.com/HP/WCL/wcolor.html https://www.handprint.com/HP/WCL/wcolor.html
  - reitanqild 8y ago
    > elsewhere on the same fantastically web 1.0 style site[1]. Refreshing! I want to read that site even if I don't care too much about colours. (The only thing I kind of miss is if it could be even easier to read on mobile.)
- joshvm 8y ago
  Either a UV laser/lamp, or you need a broadband light source, like sunlight, and a filter/monochromator of some kind (either using a prism or a diffraction grating, or a bandpass filter). You could find something that only reflected UV, yes, but only if you had a source that emitted UV in the first place. Odds are most people don't want UV emitters in a screen they look at 6 hours a day. The point is that you need a source which contains the wavelength of interest. Monitor leds are red/green/blue and don't emit violet photons. 405nm is usually somewhat visible, if a bit blurry. Blue leds are usually Gallium Nitride based which produces more like 450nm. Look up the photopic and spectroscopic response: https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Photopic_vision https://en.m.wikipedia.org/wiki/Photopic_vision https://en.m.wikipedia.org/wiki/Scotopic_vision https://en.m.wikipedia.org/wiki/Scotopic_vision
  - delinka 8y ago
    I see "spectral violet" and "UV" in two different comments. I have the understanding that "ultraviolet" is past violet and outside the visible spectrum. So now I have questions... Do spectral violet and ultraviolet differ? In what way? If something isn't visible, why does it matter?
    - class4behavior 8y ago
      >Do spectral violet and ultraviolet differ? In what way? It's ultra because it isn't within the visible spectrum. Violet is a spectral color, which means it's evoked by a single wavelength of light. So the term spectral violet refers to all the shades of violet. >>why does it matter? You have a word for it.
    - oppositelock 8y ago
      A UV lamp will emit a range of frequencies, and one the lower frequency side of that distribution will be some spectral violet, along with a bunch of UV you can't see. Spectral violet and ultraviolet are just two ranges on the continuous frequency spectrum, so they differ in frequency.
    - 8y ago
- ajross 8y ago
  Paint pigment gamuts are no better than display filters. Get a UV "black light", the color you see from the tube (not the fluorescence from other stuff) is basically what this article is calling "violet".
- blincoln 8y ago
  Look for an LED UV torch/flashlight with a wavelength of 400nm. You could also use a diffraction grating, prism, or spectroscope, but you'll need to make sure the light source going into it actually contains violet light. i.e. if you use one of those with a CFL or LED bulb, you'll most likely not get much (if any) actual violet.
OscarCunningham 8y ago
> I don't disagree with it but the colors shown in the article aren't violet, they are all shades of purple. Spectral violet is outside the gamut of most RGB color spaces, including sRGB, Adobe RGB, Pantone, CIELAB, etc. Monitors also wouldn't be able to reproduce it anyway. Monitors can display a colour with the same hue as spectral violet, just less saturated (i.e. spectal violet + grey). I think it makes sense to call this colour a kind of violet.
- peteey 8y ago
  Monitors produce a mixture of blue and red. This is the definition of purple. Our monitors are not capable of producing violet. There is no "kind of" violet to discuss. The article deceptively passes off purple for violet, and shows magenta for contrast. It is wrong.
  - OscarCunningham 8y ago
    I'm using a definition of colour under which two lights are the same colour if they look the same to a typical human, whereas you're using a definition where two lights are only the same colour if they have exactly the same spectrum. Can we at least agree that computers can produce a colour that looks the same as a spectral violet light reflected off grey paper?
    - deleted 8y ago
      [deleted]
  - seandougall 8y ago
    Spectral colors are _all_ outside of the sRGB gamut. So apart from your needlessly aggressive tone, I’m not sure what you’re getting at.
    - peteey 8y ago
      Colors are not purely spectral. Pink and brown are colors that must be mixtures. Black is no color. Normally I wouldn't care, but the point of article is the difference between mixtures and wavelength. The point of the post is semantics. Some child just learning the colors gets a free pass, but if you put up a website to explain something and its wrong, I think its reasonable to "aggressively" say so.
tellak 8y ago
> so I think it actually already encodes our bias and general lack of skill at distinguishing violet from purple. > Similarly many people don't really make a distinction for cyan and just call it blue or green when they see it. Isn’t there a difference here between poverty of naming and physiologic limitation? Most people call cyan something else because they don’t have a name for it, but they can be trained to distinguish blue or green and cyan. OTOH, the point here is that certain violets and purples are metamers and although they have different spectra they cannot be physiologically distinguished.
gardaani 8y ago
The photopigment absorption curve [1] shows that the red (L) cones have a slight rise at 400nm (violet wavelength). Also, Wikipedia's image shows it [2]. That's why cameras also have a bump at 400mn, as shown on this manufacturer's page (under the relative sensitivity tab) [3]. Cameras must have it so that they can capture light at 400nm the same way our eyes do. Otherwise those colors would look wrong in pictures. That is also how computer monitors can display a color that we see as violet. They output a bit of red and lots of blue, which excites our red and blue cones and give the same stimulus as violet at 400nm wavelength. So, monitors can't output violet, but they can trick our eyes to think that there is violet. The same happens for yellow. Monitors can't output yellow wavelength (590nm), but they output red and green, which excites our red and green cones and we think we see yellow. So, you could also say that when you see yellow on web pages, it isn't really yellow. It is just a mix of red and green. [1] http://www.handprint.com/HP/WCL/color1.html http://www.handprint.com/HP/WCL/color1.html [2] https://en.wikipedia.org/wiki/Photoreceptor_cell#/media/File:1416_Color_Sensitivity.jpg https://en.wikipedia.org/wiki/Photoreceptor_cell#/media/File... [3] https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=4024 https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=40...
- jacobolus 8y ago
  > That's why cameras also have a bump at 400mn, This explanation is incorrect. Your graph is on a log scale. You can make a camera out of any invertible linear combination of human cone cell responses and you will end up recording basically the same information as far as an idealized human observer is concerned (that’s the basic idea of the CIE system of colorimetry). The specific choice of computer display primaries has to do with maximizing the possible gamut (as well as other technical and economic criteria), not precisely targeting specific cone cells. > when you see yellow on web pages, it isn't really yellow You are using a non-standard definition of “yellow” not accepted by color scientists or color measurement experts.
  - cosarara 8y ago
    This graph, from [1] shows that the L cone's responsivity doesn't go back up at all toward the left: https://en.wikipedia.org/wiki/File:Cones_SMJ2_E.svg https://en.wikipedia.org/wiki/File:Cones_SMJ2_E.svg It is lower at 425 than at 450, which makes sense. Now what does this one from [2] mean https://en.wikipedia.org/wiki/File:1416_Color_Sensitivity.jpg https://en.wikipedia.org/wiki/File:1416_Color_Sensitivity.jp... (logarithmic scale or not)? The "Red cones" Long line says "absorbance" is higher at 425 than at 450. [1] https://en.wikipedia.org/wiki/Cone_cell https://en.wikipedia.org/wiki/Cone_cell [2] https://en.wikipedia.org/wiki/Photoreceptor_cell#Humans https://en.wikipedia.org/wiki/Photoreceptor_cell#Humans
jacobolus 8y ago
This article is total bullshit. 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/Cones_SMJ2_E.svg/500px-Cones_SMJ2_E.svg.png 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.png 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.
- blincoln 8y ago
  > 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.
ajross 8y ago
> The CIE 1931 curve showing a bump in red inside the blue is misleading I think. The CIE color space isn't intended to represent the cone responses, though. The goal was to have a set of reasonably orthogonal, positive-definite functions with which to represent all visible colors as linear combinations of primitives. The "green" Y coordinate was chosen not for its color at all but because it matched the experimentally derived "brightness" function. X and Z are only kinda associated with red and blue. But because CIE can represent all colors, you can use it to define other color spaces like sRGB which do correspond closely to retinal cell responses. There are also refined versions like LUV and LAB which are (sometimes nonlinear) transformations from XYZ and are intended to better represent perceptual "distance" linearly. XYZ is just the basic language all these things are defined in, which was its purpose.
- jacobolus 8y ago
  > sRGB which do correspond closely to retinal cell responses What does this even mean? sRGB primaries are chosen to maximize the gamut of a 3-primary additive computer display. They do not “correspond closely to retinal cell responses”.
  - ajross 8y ago
    It means that the colors chosen for those primaries are "red", "green" and "blue" for precisely the reason that those match our cones and are easy to reason about, which (I assume) is the quality you are desiring in XYZ because of the "bump" you're complaining about. I get that you're trying to be pedantic on this, and that's fine. But the fact that you're complaining about XYZ the way you are shows that... you've sorta missed a few steps. The pedantry goes much deeper, and XYZ is the way it is for some very good reasons.
    - jacobolus 8y ago
      [edit: shortened this comment] I’m not trying to be “pedantic”, just not grossly misleading / confused, the way the article and most of the comments here are, including the one at top of this thread. Frankly this nonsensical article should be flagged off the front page, as it is going to lead people who read it to be misinformed. RGB display primaries are only related to the CIE system insofar as people use the CIE system for characterizing and describing them. But it doesn’t constrain the choice of primaries. The primaries are chosen (more or less) to maximize the display gamut under the constraint that there will be 3 of them. They don’t match human cone cells per se (obviously there is some relationship between cone cell responses and maximizing the gamut, but it is not a simple one).

NikolaNovak 8y ago

What would be the best way to get the true spectral violet then - a paint chip from hardware store? Also, do you by any chance have a handy link to an actual graph on how cones react to various spectra of light? Many thanks!

tgb 8y ago
A prism, probably.
ddeck 8y ago
>do you by any chance have a handy link to an actual graph on how cones react to various spectra of light? I think you'll find everything you need here: http://www.handprint.com/HP/WCL/color1.html http://www.handprint.com/HP/WCL/color1.html and elsewhere on the same fantastically web 1.0 style site[1]. Bruce Macevoy is an artist with penchant for color theory. [1] https://www.handprint.com/HP/WCL/wcolor.html https://www.handprint.com/HP/WCL/wcolor.html
- reitanqild 8y ago
  > elsewhere on the same fantastically web 1.0 style site[1]. Refreshing! I want to read that site even if I don't care too much about colours. (The only thing I kind of miss is if it could be even easier to read on mobile.)
joshvm 8y ago
Either a UV laser/lamp, or you need a broadband light source, like sunlight, and a filter/monochromator of some kind (either using a prism or a diffraction grating, or a bandpass filter). You could find something that only reflected UV, yes, but only if you had a source that emitted UV in the first place. Odds are most people don't want UV emitters in a screen they look at 6 hours a day. The point is that you need a source which contains the wavelength of interest. Monitor leds are red/green/blue and don't emit violet photons. 405nm is usually somewhat visible, if a bit blurry. Blue leds are usually Gallium Nitride based which produces more like 450nm. Look up the photopic and spectroscopic response: https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Luminosity_function https://en.m.wikipedia.org/wiki/Photopic_vision https://en.m.wikipedia.org/wiki/Photopic_vision https://en.m.wikipedia.org/wiki/Scotopic_vision https://en.m.wikipedia.org/wiki/Scotopic_vision
- delinka 8y ago
  I see "spectral violet" and "UV" in two different comments. I have the understanding that "ultraviolet" is past violet and outside the visible spectrum. So now I have questions... Do spectral violet and ultraviolet differ? In what way? If something isn't visible, why does it matter?
  - class4behavior 8y ago
    >Do spectral violet and ultraviolet differ? In what way? It's ultra because it isn't within the visible spectrum. Violet is a spectral color, which means it's evoked by a single wavelength of light. So the term spectral violet refers to all the shades of violet. >>why does it matter? You have a word for it.
  - oppositelock 8y ago
    A UV lamp will emit a range of frequencies, and one the lower frequency side of that distribution will be some spectral violet, along with a bunch of UV you can't see. Spectral violet and ultraviolet are just two ranges on the continuous frequency spectrum, so they differ in frequency.
  - 8y ago
ajross 8y ago
Paint pigment gamuts are no better than display filters. Get a UV "black light", the color you see from the tube (not the fluorescence from other stuff) is basically what this article is calling "violet".
blincoln 8y ago
Look for an LED UV torch/flashlight with a wavelength of 400nm. You could also use a diffraction grating, prism, or spectroscope, but you'll need to make sure the light source going into it actually contains violet light. i.e. if you use one of those with a CFL or LED bulb, you'll most likely not get much (if any) actual violet.

OscarCunningham 8y ago

> I don't disagree with it but the colors shown in the article aren't violet, they are all shades of purple. Spectral violet is outside the gamut of most RGB color spaces, including sRGB, Adobe RGB, Pantone, CIELAB, etc. Monitors also wouldn't be able to reproduce it anyway. Monitors can display a colour with the same hue as spectral violet, just less saturated (i.e. spectal violet + grey). I think it makes sense to call this colour a kind of violet.

peteey 8y ago
Monitors produce a mixture of blue and red. This is the definition of purple. Our monitors are not capable of producing violet. There is no "kind of" violet to discuss. The article deceptively passes off purple for violet, and shows magenta for contrast. It is wrong.
- OscarCunningham 8y ago
  I'm using a definition of colour under which two lights are the same colour if they look the same to a typical human, whereas you're using a definition where two lights are only the same colour if they have exactly the same spectrum. Can we at least agree that computers can produce a colour that looks the same as a spectral violet light reflected off grey paper?
  - deleted 8y ago
    [deleted]
- seandougall 8y ago
  Spectral colors are _all_ outside of the sRGB gamut. So apart from your needlessly aggressive tone, I’m not sure what you’re getting at.
  - peteey 8y ago
    Colors are not purely spectral. Pink and brown are colors that must be mixtures. Black is no color. Normally I wouldn't care, but the point of article is the difference between mixtures and wavelength. The point of the post is semantics. Some child just learning the colors gets a free pass, but if you put up a website to explain something and its wrong, I think its reasonable to "aggressively" say so.

tellak 8y ago

> so I think it actually already encodes our bias and general lack of skill at distinguishing violet from purple. > Similarly many people don't really make a distinction for cyan and just call it blue or green when they see it. Isn’t there a difference here between poverty of naming and physiologic limitation? Most people call cyan something else because they don’t have a name for it, but they can be trained to distinguish blue or green and cyan. OTOH, the point here is that certain violets and purples are metamers and although they have different spectra they cannot be physiologically distinguished.

gardaani 8y ago

The photopigment absorption curve [1] shows that the red (L) cones have a slight rise at 400nm (violet wavelength). Also, Wikipedia's image shows it [2]. That's why cameras also have a bump at 400mn, as shown on this manufacturer's page (under the relative sensitivity tab) [3]. Cameras must have it so that they can capture light at 400nm the same way our eyes do. Otherwise those colors would look wrong in pictures. That is also how computer monitors can display a color that we see as violet. They output a bit of red and lots of blue, which excites our red and blue cones and give the same stimulus as violet at 400nm wavelength. So, monitors can't output violet, but they can trick our eyes to think that there is violet. The same happens for yellow. Monitors can't output yellow wavelength (590nm), but they output red and green, which excites our red and green cones and we think we see yellow. So, you could also say that when you see yellow on web pages, it isn't really yellow. It is just a mix of red and green. [1] http://www.handprint.com/HP/WCL/color1.html http://www.handprint.com/HP/WCL/color1.html [2] https://en.wikipedia.org/wiki/Photoreceptor_cell#/media/File:1416_Color_Sensitivity.jpg https://en.wikipedia.org/wiki/Photoreceptor_cell#/media/File... [3] https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=4024 https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=40...

jacobolus 8y ago
> That's why cameras also have a bump at 400mn, This explanation is incorrect. Your graph is on a log scale. You can make a camera out of any invertible linear combination of human cone cell responses and you will end up recording basically the same information as far as an idealized human observer is concerned (that’s the basic idea of the CIE system of colorimetry). The specific choice of computer display primaries has to do with maximizing the possible gamut (as well as other technical and economic criteria), not precisely targeting specific cone cells. > when you see yellow on web pages, it isn't really yellow You are using a non-standard definition of “yellow” not accepted by color scientists or color measurement experts.
- cosarara 8y ago
  This graph, from [1] shows that the L cone's responsivity doesn't go back up at all toward the left: https://en.wikipedia.org/wiki/File:Cones_SMJ2_E.svg https://en.wikipedia.org/wiki/File:Cones_SMJ2_E.svg It is lower at 425 than at 450, which makes sense. Now what does this one from [2] mean https://en.wikipedia.org/wiki/File:1416_Color_Sensitivity.jpg https://en.wikipedia.org/wiki/File:1416_Color_Sensitivity.jp... (logarithmic scale or not)? The "Red cones" Long line says "absorbance" is higher at 425 than at 450. [1] https://en.wikipedia.org/wiki/Cone_cell https://en.wikipedia.org/wiki/Cone_cell [2] https://en.wikipedia.org/wiki/Photoreceptor_cell#Humans https://en.wikipedia.org/wiki/Photoreceptor_cell#Humans

jacobolus 8y ago

This article is total bullshit. 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/Cones_SMJ2_E.svg/500px-Cones_SMJ2_E.svg.png 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.png 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.

blincoln 8y ago
> 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.

ajross 8y ago

> The CIE 1931 curve showing a bump in red inside the blue is misleading I think. The CIE color space isn't intended to represent the cone responses, though. The goal was to have a set of reasonably orthogonal, positive-definite functions with which to represent all visible colors as linear combinations of primitives. The "green" Y coordinate was chosen not for its color at all but because it matched the experimentally derived "brightness" function. X and Z are only kinda associated with red and blue. But because CIE can represent all colors, you can use it to define other color spaces like sRGB which do correspond closely to retinal cell responses. There are also refined versions like LUV and LAB which are (sometimes nonlinear) transformations from XYZ and are intended to better represent perceptual "distance" linearly. XYZ is just the basic language all these things are defined in, which was its purpose.

jacobolus 8y ago
> sRGB which do correspond closely to retinal cell responses What does this even mean? sRGB primaries are chosen to maximize the gamut of a 3-primary additive computer display. They do not “correspond closely to retinal cell responses”.
- ajross 8y ago
  It means that the colors chosen for those primaries are "red", "green" and "blue" for precisely the reason that those match our cones and are easy to reason about, which (I assume) is the quality you are desiring in XYZ because of the "bump" you're complaining about. I get that you're trying to be pedantic on this, and that's fine. But the fact that you're complaining about XYZ the way you are shows that... you've sorta missed a few steps. The pedantry goes much deeper, and XYZ is the way it is for some very good reasons.
  - jacobolus 8y ago
    [edit: shortened this comment] I’m not trying to be “pedantic”, just not grossly misleading / confused, the way the article and most of the comments here are, including the one at top of this thread. Frankly this nonsensical article should be flagged off the front page, as it is going to lead people who read it to be misinformed. RGB display primaries are only related to the CIE system insofar as people use the CIE system for characterizing and describing them. But it doesn’t constrain the choice of primaries. The primaries are chosen (more or less) to maximize the display gamut under the constraint that there will be 3 of them. They don’t match human cone cells per se (obviously there is some relationship between cone cell responses and maximizing the gamut, but it is not a simple one).