Interesting. Though maybe not so surprising that "multi-primary color display technology ... was presented as a key direction for the next-generation display industry" at the “Multi Primary Color Display Ecosystem Conference”.
This is really being driven by tandem OLED with blue phosphorescent (not fluorescent which is the current commercial design) layers, most likely from Universal Display Corp. The blue phosphorescent OLEDs have (note red/green are already) longer lifetime and and efficiency, but they aren't the deep blue you need for 3 primary displays.
Samsung and LG which both demoed ultra-wide color gamut/volume displays at SID 2026, but also CSOT/TCL. This allows even greater than BT.2020 coverage (APEX pixel is 131%!) or trade off for lifetime with higher brightness/efficiency.
The original 4 color LCDs (like RGBY/RGBW) was driven by a long ago need for brightness and resolution with fewer subpixels (see Samsung's Pentile RGBG arrangement). This both solves a different problem and the technology is being driven by a different development (and marketing).
Everything old is new again. Back in the 2010s Sharp tried to release a TV with an extra yellow colored subpixel. Commercially, it failed spectacularly.
Can anyone explain how this works? Humans have 3 (sometimes 4) cones, so I thought that going beyond 3 primaries wouldn't increase the perceivable gamut.
You are probably familiar with the horseshoe-shaped chromaticity diagram [0] of human-visible colors. A light source with three color primaries spans a triangle in that coordinate system. To cover the whole horseshoe, at least one of the vertices would need to be way outside the horseshoe. With four color primaries, you get a quadrilateral that makes it easier to cover a larger portion of the horseshoe.
The reason the visible colors form a horseshoe rather than a triangle is due to how the cones’ sensitivity ranges overlap [1]. They cannot be excited independently by the primaries of a display.
I'd like to add that no light source can lie outside the horseshoe of the CIE xyz diagram: pure wavelengths are points on the curved line, everything that mixes them moves towards the inside of the space. So you're stuck with triangles that fit within it.
Nice. If I add a primary and then clicking optimize—without first moving the primary—it seem as though there are still only 3 primaries, because the new one doesn't move.
There's a lot of great explanations here, but none that quite put it the way I'd think of it.
If we had primary color wavelengths that could stimulate each cone independently, then it would work just like you say, and we'd only need 3 of them. But because the cone spectra overlap, we don't have "orthogonal basis vectors" to work with. Our primary colors each excite a mix of cone responses.
But no problem right? As long as each primary color has a different response, we at least have linearly independent vectors, and any student of linear algebra knows you can mix those together to act as an orthogonal basis and get any desired excitation of the cones. Right?
And that would be true, except that linear algebra assumes you can freely add or subtract vector amplitudes, but with LEDs we can only generate light, we can't send a beam of "negative green". So we're constrained to the subset of colors where the basis vectors all have positive amplitudes. And that's the smaller color space that results.
Cyan is severely under-represented by monitors, so the extra pixel is a dedicated cyan. It dramatically improves the ability to display blue/green colours.
I was under the impression that yellow was a better candidate for this. But whatever. Can hardly wait for RGBCYM televisions that will make my wallet bleed.
If you have monochromatic red and green light sources, like in a laser projector, you can reproduce very well the red-yellow corner, as mentioned by others.
However, in CRT displays, the color of the light emitted by the red phosphor was rather impure, far from a saturated red.
This limitation has been inherited by the sRGB color space, and because of this, the main defect of sRGB is that it cannot reproduce a lot of colors in the yellow-orange-red-purple corner.
This is very noticeable, because there are a lot of natural objects with such colors, e.g. flowers, fruits, birds, insects, clothes, whose colors appear washed out in sRGB, but they look much better on displays with greater gamut, like P3-D65 (Display P3) which is available in better monitors.
While the colors in the cyan corner cannot be reproduced well even with a laser projector, that is usually less objectionable than the poor reproduction of yellow to red colors by sRGB monitors, because interesting cyan objects are more rarely encountered (though they exist, e.g. certain gems, lichens, algae, insects, lizards and fish, certain clothes, frequently the littoral sea).
The chromaticity diagram is basically a straight line between 640nm (red) and 545nm (green), so anything in between (including pure yellow around 570nm) can be reproduced with a linear combination of red and green.
RGBY televisions do exist, but their goal is to boost brightness in the yellow region, not color gamut.
I don't have an answer, I'm just wondering out loud.
Cone cell activation is complicated. Displays with three well chosen primaries are economical and effective, but they aren't intended to produce every perceivable color. And our chromaticity diagrams, that pointy splotch that's often used to compare display gamuts, is based on a "standard observer" that is a simplified model for human perception.
An ideal pixel would be able to emit any kind of electromagnetic radiation of any intensity, kind of fun to think about but unrealistic and impractical.
What additional primaries mathematically do is expand a gamut from a triangle to a convex polygon. While ten or a hundred primaries would be bonkers, I bet we could fit a quadrilateral or a pentagon to the perceivable gamut in ways that'd see some gains.
It's not as simple as "3 cones = 3 primary colors." Each type of cone has a response curve and three curves overlap: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colcon.htm.... And each cone has different sensitivities (blue is much more sensitive than red and green). So perfectly monochromatic light will stimulate two and usually three cones to varying degrees. When you mix "green" and "red" to get yellow, what you're actually doing is stimulating the green cones (but also the red cones) and the red cones (but also the green cones) in relative proportions that your brain perceives as yellow. But it won't necessarily give you the exact same response of the two cones as monochromatic yellow light.
We have a very "fuzzy" visual perception. I remember seeing an RGB response curve of the human vision mechanism once. I doubt it was measured. Maybe they extracted it from the CIELab stuff.
Anyway, things like the green (or blue -can't remember) receptor have a strong curve in the green spectrum, but also a "bump," over in red (I think).
We're an organic mess.
Looking at RGB curves for LEDs, they are three perfect little mountains. No "bumps," anywhere.
I guess that the goal is to try to mimic the "messy" human visual perception.
Also, expect these monitors to be non-cheap. Companies like Eizo are having a difficult time, justifying their prices, these days.
The cones are not sensitive to a single wavelength but to a range.
The green-sensitive cones overlap with the red-sensitive cones, and to a smaller extent also with the blue-sensitive.
Full saturation red and blue are possible by emitting light on the edges of the visible spectrum.
Full saturation green, however, also activates the red and blue cones.
To cover the whole gamut is impossible, but you can approximate it with ~three green tones: a 490nm deep cyan that hits blue and green but not red, ~510nm that hits red and blue equally, and ~540nm the peak of the green cone.
Humans can see more than the colors they can make with only combining RGB pixels; you can't make 'neon' colors with them, even though we can see them in real life, for example. Other commenters pointed to links showing the visible color gamut vs the RGB ones. Compare also with CMYK used in print, it can produce sightly different colors compared to display RGB.
Remember that light is synthesized by combining the primaries; the spectrum is defined by their convex hull. You can expand the hull and ergo gamut by adding primaries.
The RGB setup we have strikes a balance between cost and visual quality. If the cost of adding primaries goes down you can add more to increase the quality. One issue is that the signals often assume RGB (channels), so the hardware manufacturer would have to adapt the RGB signal to their multi-primary hardware.
I don't know either, but if we visualize the RGB color space as a triangle that is entirely contained within the weird shape that represents the set of all colors the human eye can perceive ( https://en.wikipedia.org/wiki/RGB_color_model#/media/File:CI... ), presumably the idea is to cover more of that human-perceived space via a quadrilateral with four anchor points rather than a triangle with three. Presumably the "C" in "RGBC" stands for cyan, and in the linked image the cyan portion of the color space is particularly poorly represented.
Remember that light is synthesized by combining the primaries; the spectrum is defined by their convex hull. You can expand the hull and ergo gamut by adding primaries.
Disable JavaScript. A site abuses its privilege to execute code in your browser? Take the privilege away. Extensions like uBlock or no script can do this.
It's unmaintained, and off-topic for this discussion, but the Luminous JS event blocker¹ was cool because it allowed blocking specific event handlers while still allowing JS to execute.
I knew I was a highlighter but reading that showed me how much my brain relies on spam click highlighting to keep my eyes on track. I should probably read more books.
I do it one type of pointer or another for tracking my reading position continuously. I even highlighted some words in your comment while I read it. In a book, I typically put my finger (or the corner of my bookmark) under the 3 words or so I'm currently reading, or I'll put my thumb next to the line I'm currently reading. I don't usually think about it, but being on that web page and being prevented from highlighting made me back away quickly. If I'm not highlighting, then I'll also scroll so the top of the page marks where I am. (Whenever a page has a menu that changes relative position/size or pops up to cover the content when you change scrolling directions, that's an annoyance.) I think I use something to keep track of the current line like that more often than highlighting. Now that I think about it, if my mouse pointer were more noticeable, I assume I might simply point to where I am. Then again, the highlighted words are independent of the pointer, so it lets you have both.
Why? Maybe my eyes move away from the page while I think about what I'm reading. Otherwise you'd have to keep a visual lock on your reading position continuously right? Or you'd have to scan the text to figure out where you left off.
If you’d read the article, you’d learned that these are advancements in backlit LCD technology. More generally, however, having more than three color primaries is orthogonal to the question of backlit vs. self-emissive.
Probably yes, but density hasn’t been an issue for over a decade. Mobile device screens are 5-10x denser than TVs, and cost <€100; Apple has used mini-led for their retina displays for a long time too.
Yes, it would require more. No, at least assuming the pixels aren't well below the eye's spatial resolution limit then resolution will impact perceived quality much more than color accuracy. Consider what lossy image codecs like to do to chroma and why that is.
However, there are tasks that benefit from better color reproduction. There are also screens where the pixel size is well below the human discernable limit.
enough studies and randomized control trials have been conducted, it is conclusively shown that blue light emitted from household devices does not interact meaningfully with sleep. metareview CRD420251034611 "non-significant reduction in sleep onset latency" means blue light has been conclusively observed to not delay sleep - it doesn't mean that blue light has not yet been observed to delay sleep, we instead know conclusively that it does not. even better, a registered trial one: https://clinicaltrials.gov/study/NCT01855126 - RCT where shining a bunch of blue light on old people's eyeballs didn't help them stay awake longer (going to bed too early is actually a more common clinical issue than staying up too late). well if it can't keep people awake, it doesn't keep them awake.
it's a great interview question though. "does blue light from screens cause sleep delay?" it doesn't. why do so many people think it does? why suffer with a piss colored screen?
My erstwhile psychiatrist was completely obsessed with blue light. That, and caffeine, she told me to cut them out. She insisted that staring at a screen late at night, and just prior to sleeping, was my undoing.
And to a certain extent, she was right, but it was not "the blue light" per se that was damaging my psyche. Rather, it was the stuff within the light that was getting me agitated and angry. It was the disputes on Wikipedia, the social media arguments, the ragebait I found everywhere, the F.U.D. leading to my paranoia and rebellion and loss of trust.
It's like people who say "5G is harmful to our brains" -- well, yes, because whatever is being transmitted over that 5G is harmful, like porn or social media -- not the mere frequencies themselves!
Interesting. Though maybe not so surprising that "multi-primary color display technology ... was presented as a key direction for the next-generation display industry" at the “Multi Primary Color Display Ecosystem Conference”.
This is really being driven by tandem OLED with blue phosphorescent (not fluorescent which is the current commercial design) layers, most likely from Universal Display Corp. The blue phosphorescent OLEDs have (note red/green are already) longer lifetime and and efficiency, but they aren't the deep blue you need for 3 primary displays.
Samsung and LG which both demoed ultra-wide color gamut/volume displays at SID 2026, but also CSOT/TCL. This allows even greater than BT.2020 coverage (APEX pixel is 131%!) or trade off for lifetime with higher brightness/efficiency.
The original 4 color LCDs (like RGBY/RGBW) was driven by a long ago need for brightness and resolution with fewer subpixels (see Samsung's Pentile RGBG arrangement). This both solves a different problem and the technology is being driven by a different development (and marketing).
https://en.ubiresearchnet.com/sid-2026-bt2020-oled-display-t...
Everything old is new again. Back in the 2010s Sharp tried to release a TV with an extra yellow colored subpixel. Commercially, it failed spectacularly.
I remember George Takei shilling those things.
Can anyone explain how this works? Humans have 3 (sometimes 4) cones, so I thought that going beyond 3 primaries wouldn't increase the perceivable gamut.
Update: thanks for all the great explanations!
You are probably familiar with the horseshoe-shaped chromaticity diagram [0] of human-visible colors. A light source with three color primaries spans a triangle in that coordinate system. To cover the whole horseshoe, at least one of the vertices would need to be way outside the horseshoe. With four color primaries, you get a quadrilateral that makes it easier to cover a larger portion of the horseshoe.
The reason the visible colors form a horseshoe rather than a triangle is due to how the cones’ sensitivity ranges overlap [1]. They cannot be excited independently by the primaries of a display.
[0] https://upload.wikimedia.org/wikipedia/commons/1/1e/CIE1931x...
[1] https://upload.wikimedia.org/wikipedia/commons/thumb/0/04/Co...
Excellent explanation.
I'd like to add that no light source can lie outside the horseshoe of the CIE xyz diagram: pure wavelengths are points on the curved line, everything that mixes them moves towards the inside of the space. So you're stuck with triangles that fit within it.
I was wondering about that, since some color spaces have their primaries outside the horseshoe. Thanks for clarifying.
What does it mean then for ProPhoto RGB triangle to be outside of the horseshoe on that diagram?
It uses nonphysical "imaginary" primaries that have meaning within the coordinate system but not within the human perceptual system.
This was a really fun visualization, so I vibecoded it.
https://www.jackgaller.com/colorspace
Nice. If I add a primary and then clicking optimize—without first moving the primary—it seem as though there are still only 3 primaries, because the new one doesn't move.
[dead]
There's a lot of great explanations here, but none that quite put it the way I'd think of it.
If we had primary color wavelengths that could stimulate each cone independently, then it would work just like you say, and we'd only need 3 of them. But because the cone spectra overlap, we don't have "orthogonal basis vectors" to work with. Our primary colors each excite a mix of cone responses.
But no problem right? As long as each primary color has a different response, we at least have linearly independent vectors, and any student of linear algebra knows you can mix those together to act as an orthogonal basis and get any desired excitation of the cones. Right?
And that would be true, except that linear algebra assumes you can freely add or subtract vector amplitudes, but with LEDs we can only generate light, we can't send a beam of "negative green". So we're constrained to the subset of colors where the basis vectors all have positive amplitudes. And that's the smaller color space that results.
Cyan is severely under-represented by monitors, so the extra pixel is a dedicated cyan. It dramatically improves the ability to display blue/green colours.
*edit: found the link I was after on this: https://moultano.wordpress.com/2026/06/19/where-to-find-the-...
Wow, that's a great article about color! It answers many questions. Thanks for the link.
I was under the impression that yellow was a better candidate for this. But whatever. Can hardly wait for RGBCYM televisions that will make my wallet bleed.
If you have monochromatic red and green light sources, like in a laser projector, you can reproduce very well the red-yellow corner, as mentioned by others.
However, in CRT displays, the color of the light emitted by the red phosphor was rather impure, far from a saturated red.
This limitation has been inherited by the sRGB color space, and because of this, the main defect of sRGB is that it cannot reproduce a lot of colors in the yellow-orange-red-purple corner.
This is very noticeable, because there are a lot of natural objects with such colors, e.g. flowers, fruits, birds, insects, clothes, whose colors appear washed out in sRGB, but they look much better on displays with greater gamut, like P3-D65 (Display P3) which is available in better monitors.
While the colors in the cyan corner cannot be reproduced well even with a laser projector, that is usually less objectionable than the poor reproduction of yellow to red colors by sRGB monitors, because interesting cyan objects are more rarely encountered (though they exist, e.g. certain gems, lichens, algae, insects, lizards and fish, certain clothes, frequently the littoral sea).
The chromaticity diagram is basically a straight line between 640nm (red) and 545nm (green), so anything in between (including pure yellow around 570nm) can be reproduced with a linear combination of red and green.
RGBY televisions do exist, but their goal is to boost brightness in the yellow region, not color gamut.
How about just a "true RGB" that will make your wallet bleed (at $31k): https://www.youtube.com/watch?v=aAOgZ6cjrio
I don't have an answer, I'm just wondering out loud.
Cone cell activation is complicated. Displays with three well chosen primaries are economical and effective, but they aren't intended to produce every perceivable color. And our chromaticity diagrams, that pointy splotch that's often used to compare display gamuts, is based on a "standard observer" that is a simplified model for human perception.
An ideal pixel would be able to emit any kind of electromagnetic radiation of any intensity, kind of fun to think about but unrealistic and impractical.
What additional primaries mathematically do is expand a gamut from a triangle to a convex polygon. While ten or a hundred primaries would be bonkers, I bet we could fit a quadrilateral or a pentagon to the perceivable gamut in ways that'd see some gains.
It's not as simple as "3 cones = 3 primary colors." Each type of cone has a response curve and three curves overlap: http://hyperphysics.phy-astr.gsu.edu/hbase/vision/colcon.htm.... And each cone has different sensitivities (blue is much more sensitive than red and green). So perfectly monochromatic light will stimulate two and usually three cones to varying degrees. When you mix "green" and "red" to get yellow, what you're actually doing is stimulating the green cones (but also the red cones) and the red cones (but also the green cones) in relative proportions that your brain perceives as yellow. But it won't necessarily give you the exact same response of the two cones as monochromatic yellow light.
We have a very "fuzzy" visual perception. I remember seeing an RGB response curve of the human vision mechanism once. I doubt it was measured. Maybe they extracted it from the CIELab stuff.
Anyway, things like the green (or blue -can't remember) receptor have a strong curve in the green spectrum, but also a "bump," over in red (I think).
We're an organic mess.
Looking at RGB curves for LEDs, they are three perfect little mountains. No "bumps," anywhere.
I guess that the goal is to try to mimic the "messy" human visual perception.
Also, expect these monitors to be non-cheap. Companies like Eizo are having a difficult time, justifying their prices, these days.
The cones are not sensitive to a single wavelength but to a range.
The green-sensitive cones overlap with the red-sensitive cones, and to a smaller extent also with the blue-sensitive.
Full saturation red and blue are possible by emitting light on the edges of the visible spectrum.
Full saturation green, however, also activates the red and blue cones.
To cover the whole gamut is impossible, but you can approximate it with ~three green tones: a 490nm deep cyan that hits blue and green but not red, ~510nm that hits red and blue equally, and ~540nm the peak of the green cone.
Humans can see more than the colors they can make with only combining RGB pixels; you can't make 'neon' colors with them, even though we can see them in real life, for example. Other commenters pointed to links showing the visible color gamut vs the RGB ones. Compare also with CMYK used in print, it can produce sightly different colors compared to display RGB.
The YouTube logo in HDR looks very neon to me
Remember that light is synthesized by combining the primaries; the spectrum is defined by their convex hull. You can expand the hull and ergo gamut by adding primaries.
The RGB setup we have strikes a balance between cost and visual quality. If the cost of adding primaries goes down you can add more to increase the quality. One issue is that the signals often assume RGB (channels), so the hardware manufacturer would have to adapt the RGB signal to their multi-primary hardware.
I don't know either, but if we visualize the RGB color space as a triangle that is entirely contained within the weird shape that represents the set of all colors the human eye can perceive ( https://en.wikipedia.org/wiki/RGB_color_model#/media/File:CI... ), presumably the idea is to cover more of that human-perceived space via a quadrilateral with four anchor points rather than a triangle with three. Presumably the "C" in "RGBC" stands for cyan, and in the linked image the cyan portion of the color space is particularly poorly represented.
Remember that light is synthesized by combining the primaries; the spectrum is defined by their convex hull. You can expand the hull and ergo gamut by adding primaries.
Preventing selection is quite the useless and user antagonistic pattern...
Disable JavaScript. A site abuses its privilege to execute code in your browser? Take the privilege away. Extensions like uBlock or no script can do this.
It's unmaintained, and off-topic for this discussion, but the Luminous JS event blocker¹ was cool because it allowed blocking specific event handlers while still allowing JS to execute.
¹https://gbaptista.github.io/luminous/doc/en-US/
Yeah. That was crazy. I've not encountered that, before.
I knew I was a highlighter but reading that showed me how much my brain relies on spam click highlighting to keep my eyes on track. I should probably read more books.
Fascinating! I wondered why some people did that
I do it one type of pointer or another for tracking my reading position continuously. I even highlighted some words in your comment while I read it. In a book, I typically put my finger (or the corner of my bookmark) under the 3 words or so I'm currently reading, or I'll put my thumb next to the line I'm currently reading. I don't usually think about it, but being on that web page and being prevented from highlighting made me back away quickly. If I'm not highlighting, then I'll also scroll so the top of the page marks where I am. (Whenever a page has a menu that changes relative position/size or pops up to cover the content when you change scrolling directions, that's an annoyance.) I think I use something to keep track of the current line like that more often than highlighting. Now that I think about it, if my mouse pointer were more noticeable, I assume I might simply point to where I am. Then again, the highlighted words are independent of the pointer, so it lets you have both.
Why? Maybe my eyes move away from the page while I think about what I'm reading. Otherwise you'd have to keep a visual lock on your reading position continuously right? Or you'd have to scan the text to figure out where you left off.
Turning off Javascript helps.
So where does this stand in 'backlit' or 'self emmission' panels?
"TV Displays Explained at the Fundamental Level" https://www.youtube.com/watch?v=WhFwPAfwdLo
If you’d read the article, you’d learned that these are advancements in backlit LCD technology. More generally, however, having more than three color primaries is orthogonal to the question of backlit vs. self-emissive.
If you're using 4 of them versus 3, wouldn't this require 1/3 more subpixels to achieve the same display resolution in pixels?
Or -using same # of subpixels per cm^2- would perceived display quality be similar due to better color representation?
Probably yes, but density hasn’t been an issue for over a decade. Mobile device screens are 5-10x denser than TVs, and cost <€100; Apple has used mini-led for their retina displays for a long time too.
Yes, it would require more. No, at least assuming the pixels aren't well below the eye's spatial resolution limit then resolution will impact perceived quality much more than color accuracy. Consider what lossy image codecs like to do to chroma and why that is.
However, there are tasks that benefit from better color reproduction. There are also screens where the pixel size is well below the human discernable limit.
> reduce harmful blue light
enough studies and randomized control trials have been conducted, it is conclusively shown that blue light emitted from household devices does not interact meaningfully with sleep. metareview CRD420251034611 "non-significant reduction in sleep onset latency" means blue light has been conclusively observed to not delay sleep - it doesn't mean that blue light has not yet been observed to delay sleep, we instead know conclusively that it does not. even better, a registered trial one: https://clinicaltrials.gov/study/NCT01855126 - RCT where shining a bunch of blue light on old people's eyeballs didn't help them stay awake longer (going to bed too early is actually a more common clinical issue than staying up too late). well if it can't keep people awake, it doesn't keep them awake.
it's a great interview question though. "does blue light from screens cause sleep delay?" it doesn't. why do so many people think it does? why suffer with a piss colored screen?
My erstwhile psychiatrist was completely obsessed with blue light. That, and caffeine, she told me to cut them out. She insisted that staring at a screen late at night, and just prior to sleeping, was my undoing.
And to a certain extent, she was right, but it was not "the blue light" per se that was damaging my psyche. Rather, it was the stuff within the light that was getting me agitated and angry. It was the disputes on Wikipedia, the social media arguments, the ragebait I found everywhere, the F.U.D. leading to my paranoia and rebellion and loss of trust.
It's like people who say "5G is harmful to our brains" -- well, yes, because whatever is being transmitted over that 5G is harmful, like porn or social media -- not the mere frequencies themselves!