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My understanding of digital displays is that they create colored images through pixels which can display red, green, or blue at each site, and use additive color theory to combine those colors to create the sensation of color as we normally see it. I am not sure if the pixels control for intensity in each color signal.

I understand there is a large body of work towards this theory and that it is relatively robust. However, there are still colors that we can see in real life which cannot be displayed in this way.

My question is, if instead of mixing three predetermined wavelengths of light at each site, (red, green, blue), would there be any advantage to a system where each pixel could independently produce any wavelength of visible light, and moreover control the intensity of that light?

Essentially I am asking if there write be benefit to having pixels output analogue values, instead of three discrete values, combined with the ability to modulate their intensity.

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    \$\begingroup\$ I think bringing the terms "analogue" vs "RGB" into your question is just confusing the issue. What are you hoping to achieve? Even if you had a display that could output any wavelength of light, what about the source it is reading from? Does the source system have the ability to capture and accurately represent all possible wavelengths of visible light? (The answer is no.) \$\endgroup\$
    – osullic
    Mar 15 at 15:17
  • \$\begingroup\$ sure there would be an advantage.... let us know when you develop the tech to create a pixel capable of emitting any particular wavelength of light.... that's the main challenge.... \$\endgroup\$
    – twalberg
    Mar 15 at 15:19
  • \$\begingroup\$ It would be an advantage, yes. And prepare your suitcase to win a Nobel prize in physics. \$\endgroup\$
    – Rafael
    Mar 16 at 2:55
  • \$\begingroup\$ Generating light of an arbitrary wavelength is not enough. What is the wavelength of gray? \$\endgroup\$ Mar 20 at 12:24

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Human color vision is dictated by the sensitivity of the 3 kinds of cone cell in the retina plus a little bit of neurological weirdness.

The result of this is that there are only 3 degrees of freedom to human color perception so we only really need 3 colors, close enough to be perceived as coming from the same spot, in varied amounts, to get a full range of perceivable colors.

PS. The human color perception has a lot of crosstalk between the colors and some weirdness associated with it so most normal RGB spaces are a little more narrow than the true tristimulus of the eyes. I think the red stimulus actually has a negative area of the curve under where green an blue intersect so it might only be mostly physically possible. See The Wikipedia article on the XYZ color space.

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If you ever find out a way to make full spectrum display (that's what you are trying to achieve) make sure you sell it for a great dividend.
Display's pixels are analogue devices. It's the DAC output which is discrete and DAC's input which is digital. Number of values the DAC (which is what resides on TCON basically) can output has nothing to do what wavelength the pixel produces. The wavelength of light emitted is defined by phosphor (in CRT) or by colour filter (TFT panels) and is fixed in all cases.

You seem to have misconception that display pixels display only one of three colours. That's false. Display pixels are typically groups of all three colours. Having three independent types of subpixels does not make those pixels "difital" or "discrete".

Human eye contains several independent types of light sensitive cells as well, that does not make it "digital" or "discrete" either.

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  • \$\begingroup\$ While not true at all for CRTs, it is true for LCDs. There's just 3 times as many pixels as you think. \$\endgroup\$
    – davolfman
    Mar 15 at 17:23
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A display pixel is made up of R+G+B LEDs(LCDs)... it can blend all three colors and vary their individual brightnesses simultaneously. This is a high resolution macro of the screen on my Motorola Moto X4 phone screen while displaying white.

enter image description here

And this is the output of an LED screen showing white.

enter image description here

Then we have the issue of how human vision works, where the color receptors (cone cells) are individually sensitive to long, middle, and short wavelengths (RGB; only one each), which are then blended by the brain to create perceived colors.

enter image description here

And then we have how a digital sensor sees.

enter image description here

Of course, every different sensor, every different display, and indeed every different person, will have different specific response curves. I.e. none of them can perceive nor replicate true color 100% accurately.

So we end up with a situation where an RGB display is generally able to display any visible color with reasonably sufficient accuracy... i.e. 8bit RGB color can generate 16M colors whereas a human can see ~ 10M.

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When energy is applied to any light emitting component, the parts of the spectrum emitted will be dependent on the characteristics of the materials of the component - the heat effect on the materials of an incandescent emitter, the fluorescence from a gas or vapour or the effect of the electron "gap" in a semiconductor. There will be a specific partial spectrum emitted depending on the materials used.

This was why incandescent lamps were "yellower" than fluorescent, and why there was significant development time from red to green and from green to blue LEDs : I'd recommend the "History" section of the Wikipedia page on LEDs.

Science hasn't yet come up with a way of varying the partial spectrum of light emitted from specific materials - or a way to change the component materials of an emitter while in operation.

Mixing the light in different proportions from three different emitters is, by comparison, a lot easier. I'm sure there would be advantages to having an component that could emit at continuously variable wavelengths (or even small steps in wavelength), but so far we haven't a clue how this could be done.

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short answer: no, to humans mixing the three RGB (sub)pixels results in exactly the same percieved color as having one pixel with the exact wavelength of the respective color. the reason for this is that humans have three color receptors, whos color sensitivity is approximatly red, green and blue (for more detail see answer of Steven Kersting).

so basically the red, green and blue (sub)pixel format of LCD screens mimics the way the human retina with three color receptors works. for other animals with different receptors this might be a different issue.

as a sidenote your denotion of "analogue" pixel is misleading: one pixel with tuneable wavelength wouldn't be more or less analogue then three pixels. both would have discrete values of brightness and wavelength, given by digital values. whereas the emitted light = electromagnetic waves are analogue waves in any case.

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