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Polychromatic Pixels

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Re: Polychromatic Pixels

#141

Post by mark-r »

Retr0id wrote: post #43
o11c wrote: post #38

Earlier quoted context omitted.

Dithering is at worst equivalent to subpixels, which we already use. If you take the "no subpixels" claim out of the article, this technology still seems useful for higher DPI and easier manufacture.

Sure, but PPI/DPI headline figures are usually counted per-pixel, not per-subpixel, so the raw density numbers aren't directly comparable (and I'm not really sure what a fair "adjustment factor" would be)

"Fair" has nothing to do with it, the adjustment factor will be whatever the marketing folks think they can get away with.

Re: Polychromatic Pixels

#142

Post by mark-r »

refulgentis wrote: post #21
Retr0id wrote: post #18

Hm, thinking about this further, this would need dithering to work properly (which probably works fine, but the perceived quality difference would mean pixel density comparisons aren't apples-to-apples) Presumably, you get to control hue and brightness per-pixel. But that only gives you access to a thin slice of the sRGB gamut (i.e. the parts of HSL where saturation is maxed out), but dithering can solve that. Coming…

I'm not sure why saturation couldn't be controlled. I probably missed something in the article, though I do see ex. desaturated yellow in the photographs so I'm not sure this is accurate. If you can't control saturation, I'm not sure dithering won't help, I don't see how you'd approximate a less saturated color from a more saturated color. HSL is extremely misleading, it's a crude approximation for 1970s computing co…

Any desaturated colors I saw were also very bright, so I blame it on overexposure of the camera. Probably looked totally different in person.

Unsaturated colors aren't a problem, you just need to mix a bit of the opposite color. Unsaturated purples will be a challenge because you need to mix 3 wavelengths rather than just 2.

Re: Polychromatic Pixels

#143

Post by mark-r »

exmadscientist wrote: post #104
layer8 wrote: post #44

Earlier quoted context omitted.

Yes, mix two complementary colors like orange and cyan. You just need two wavelengths that hit all three cone types [0] in the right ratio. There’s the possibility that it’s subject to more variation across individuals though, as not everyone has exactly the same sensitivity curves. [0] https://upload.wikimedia.org/wikipedia/commons/f/f1/1416_Col...

Human vision in the yellow (~590nm) region is known to be extremely sensitive to particular wavelengths. Observe how quickly things go from green through yellow to amber/orange! So this is probably a nonstarter.

Every single white LED bulb you buy for your light fixtures is a mix of blue LED and yellow phosphor, so in practice it's no problem at all. Although I do concede that the yellow is probably not monochromatic.

Re: Polychromatic Pixels

#144

Post by mark-r »

yig wrote: post #11
dmitrygr wrote: post #4

These still produce a single [adjustable] wavelength, which means some colors that are displayable on displays of today are not representable using just one of these, and multiples will be required.

Two adjustable wavelength emitters should be sufficient, right? So the picking-and-placing problem gets easier by factor of 3:2 rather than 3:1.

The whole point of this technology is that you don't need picking-and-placing anymore, it's all built on the same wafer.

Re: Polychromatic Pixels

#145

Post by exmadscientist »

mark-r wrote: post #143
exmadscientist wrote: post #104

Earlier quoted context omitted.

Human vision in the yellow (~590nm) region is known to be extremely sensitive to particular wavelengths. Observe how quickly things go from green through yellow to amber/orange! So this is probably a nonstarter.

Every single white LED bulb you buy for your light fixtures is a mix of blue LED and yellow phosphor, so in practice it's no problem at all. Although I do concede that the yellow is probably not monochromatic.

It is 100% not monochromatic and that makes all the difference.

Here's one model I'm fairly familar with, having evaluated it for design-in to a product a few years back: https://www.lightstec.com/wp-content/uploads/2018/10/Philips... (apologies for the non-authoritative link, their entire datasheet server appears to be down....)

Take a look at page 8 (PDF page 9), Figure 4, "Relative Spectral Distribution vs. Wavelength". Look at those spectral curves and what that phosphor really does. See that nice broad peak, that's pretty insensitive to the exact details? A little shift in the peak doesn't change the output much. And yet, they still bin white LEDs intensively!

These things just do not work with monochromatic emission in the orange. And the phosphor isn't even that good at low color temperatures (CCTs). Below about 2000K-2400K (ish), this approach doesn't work: the resulting LED looks like yellow trash, not like you'd expect (it should look something like a candle flame). So even phosphors can't get you down all that far in CCT. (There are probably expensive phosphors that can do it... but none were in mass production five or six years ago when I did a deep search.)

Re: Polychromatic Pixels

#146

Post by ddingus »

jessriedel wrote: post #54
GrantMoyer wrote: post #45

A single wavelength can't reproduce all visible colors. These pixels are variable wavelength, but can only produce one at a time, so you'd still need at least 2 of these pixels to reproduce any visible color. The fundamental problem is that color space is 2D[1] (color + brightness is 3D, hence 3 subpixel on traditional displays), but monochromatic light has only 1 dimension to vary for color. [1]: https://en.wikipedi…

Ha, yea, in particular these monochromatic pixels can't simply be white. Notably ctrl-f'ing for "white" gives zero results on this page. Relatedly, the page talks a lot about pixel density, but this confused me: if you swap each R, G, or B LED with an adjustable LED, you naively get a one-time 3x boost in pixel area density, which is a one-time sqrt(3)=1.73x boost in linear resolution. So I think density is really a…

Would one not just use a few pixels to create white?

That does mean a variable resolution scenario.

Re: Polychromatic Pixels

#147

Post by rini17 »

mark-r wrote: post #139
mensetmanusman wrote: post #75

Earlier quoted context omitted.

The human eye will see white when a pixel flashes through all of the colors quickly in time.

You don't need all the colors. As every household white LED bulb proves, you can get it with just a combination of blue and yellow.

You'll get atrocious CRI/sick skin tones that way. There's much more fleshed out spectrum in nowadays LEDs, especially warm white variants.

Re: Polychromatic Pixels

#148

Post by Bumblonono »

creshal wrote: post #114
Bumblonono wrote: post #111

Earlier quoted context omitted.

There are plenty of monochromatic cases. Right now hw has a lot of orange. Dynamic resolution / subpixel rendering. Retina looks really good already, not sure if the effect would be relevant or interesting but it might open up something new

What Apple sells as "retina" still doesn't match common print densities, there's definitely room for improvement.

You make it sound like there is still an easy to spot difference. When i look at the print quality of pictures on a news paper, its the opposite and at least for me, i don't need more than retina and i was very eager to switch to 4k to have higher dpi.

But 14' with retina im very happy.

I'm actually more surprised by hdr on my lg oled 4k. Its actually quite nice when done well.

Re: Polychromatic Pixels

#149

Post by creshal »

Bumblonono wrote: post #148
creshal wrote: post #114

Earlier quoted context omitted.

What Apple sells as "retina" still doesn't match common print densities, there's definitely room for improvement.

You make it sound like there is still an easy to spot difference. When i look at the print quality of pictures on a news paper, its the opposite and at least for me, i don't need more than retina and i was very eager to switch to 4k to have higher dpi. But 14' with retina im very happy. I'm actually more surprised by hdr on my lg oled 4k. Its actually quite nice when done well.

Newspapers are famously printed on the lowest quality recycled paper and cheapest print process available, because they're disposable. Compare a retina screen to a coffee table style reference book with high resolution photos – the kinds you can use a magnifying glass on - and you'll still notice differences.

Or just look at what companies do when manufacturing technologies allow them to push for higher densities: iPhones now exceed 450 dpi, and the 8" iPads exceed 300; if the technology allowed it, Apple would most likely introduce higher densities on larger iPads and Macbooks as well.

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