[akagr]

Isn’t e-paper the general category of low power displays? I understand that “e-ink” are a trademarked subset of the broader e-paper category, which also includes memory-in-pixel LCD displays which other watches like Garmin (and probably pebble) have. E-ink displays are only manufactured by eink corp, and are popularly found on e-readers, shelf price tags in some stores etc.

I may be mixing terms in my brain, though. Happy to be corrected.

[drum55]

I haven't really heard it being used like that, always heard e-paper being used as the specific e-ink displays and never anything else. The only time I've seen the (in my mind) confused messaging is on Pebble's own website, I still have my original Pebble Time somewhere, and that's a good part just down to how much I love those displays. I don't think I'd have used one for years if they were epaper.

[jsheard]

> The only time I've seen the (in my mind) confused messaging is on Pebble's own website

Yeah, other wearable manufacturers who use the same display technology usually call it MIP instead. Pebble are pretty much the only ones who call it e-paper, which has led some to think theirs is a distinct thing, but it's just MIP.

[cubefox]

> Isn’t e-paper the general category of low power displays?

Yes, or more precisely: reflective displays without backlight. There were many such display technologies a while ago (when the Kindle took off and various companies tried to compete with E Ink), but most have since been abandoned.

Pretty much all colored e-paper screens have much lower contrast than color printing on paper, since they mix colors by using can conventional RGB sub-pixels and darkening them individually, just like regular lit screens, which reduces the amount of reflected light.

[ssl-3]

> Pretty much all colored e-paper screens have much lower contrast than color printing on paper, since they mix colors by using can conventional RGB sub-pixels and darkening them individually, just like regular lit screens, which reduces the amount of reflected light.

Isn't that how color images printed paper works, too? We use inks (often in CMYK coloration, but a galaxy of other options exist) to subtract light from what would otherwise be reflected by a plain white paper.

What makes e-paper screens worse in this way?

[cubefox]

> Isn't that how color images printed paper works, too?

No. When you print a piece of paper some color, e.g. red, it will be completely red. But most e-paper screens will only be 33% red (optimistically) and 66% black. This is because physical pixels usually can't change color themselves, only brightness, so you use three of them, and darken the RGB components, to produce a colored pixel.

For displaying white on color e-paper screens you will have three non-dark RGB sub-pixels, but each color component only reflects at most a third of the incoming spectrum, either red, green, or blue wavelengths, while white paper (or monochromatic e-paper screens) will reflect all three wavelengths everywhere.

[drum55]

That’s not really correct, modern color eink displays actually change color, there’s different pigments inside each cell and others are created visually using dithering. Only the older type are monochrome displays with a color filter behaves like you’re describing.

https://www.eink.com/tech/detail/How_it_works

[cubefox]

Yeah, E Ink Gallery is the only real exception to the rule with full color support. (The store signage can also change colors, but they don't support color mixing, so there are just three or four colors in total.) Unfortunately, even after 10 years, E Ink Gallery is still far behind colored paper in quality. I think fundamentally their approach to e-paper (electrophoresis displays) is just not suited for full color.

[jsheard]

Multi-pigment panels exist but in practice nearly all color e-readers still use the filter-based panels, because they are so much cheaper. There are zero Kindle or Kobo models with the multi-pigment technology.

[drum55]

The ReMarkable devices are E Ink Gallery 3 multi pigment display, I have one on my desk.

[drum55]

They more or less have colored particles hanging around in goop and those get pushed around within a small sealed cell by electrostatic charges, there’s presumably some fundamental limit on the total quantity of the colored particles within the cell that’s quite low. I think modern displays have 4 different colored particles in each cell implying only a small portion of the contents is viewable most of the time. On paper you can have basically 100% saturation of whatever color you want in one area.