Biggest 300ppi eink screen?

[isaacbh]

Is the 8" screen on the Kobo Forma the biggest available with 300ppi? I tried previously a 10.3" reader from Onyx, but with only 227ppi, text and fine lines were too blurry for my taste. Currently I have the original H2O, and for reading PDFs I need to massage the file with tools like k2pdfopt, which is not always ideal. I assume all companies source their screens from eInk, but I couldn't find anything there. Thanks!

[ottischwenk]

Originally Posted by isaacbh

Is the 8" screen on the Kobo Forma the biggest available with 300ppi?

Yes, it is ~ 5 mm diagonally larger than the standard 7.8 inch screens with glass substrate.

[rowe]

I think that's right. I'd love there to be a 300dpi 13" reader, but E-ink are already struggling with quality control at pixel densities closer to 200 for the larger readers (seems most 13" screens have stuck dots).

[Quoth]

Even 200 dpi would be fine with true 254 shades with black and white. But eink only just manages 14 shades in addition to black and white so antialiasing is limited. A 133 dpi laptop may look better in resolution than 227 dpi eink because it has close to 256 brightness levels, colour (close to 16M variations of hue, saturation and brightness) AND it has sub pixel addressing. A colour LCD or OLED at 133 dpi is effectively 266 x 266 or 399 x 133 dpi before anti-aliasing, which with 254 brightness levels of grey (and more if coloured) gives a visual appearance similar to about 1200 x 500 dpi laser or 1000 x 1000 laser, depending on the type of subpixel layout.

The less shades the more resolution is needed. That's why laser printers need about 1200 x 1200 to decently render 150 dpi 16.7 Million colour photos, each dot is either on or off, no levels at all. Ink jets for a while have been able to vary density to an extent by modulating the droplet size, so 600 x 600 dpi ink jet can do as well as 2400 x 2400 high end laser prints.

[rkomar]

Originally Posted by Quoth

But eink only just manages 14 shades in addition to black and white ...

You keep making this distinction, but the "black" isn't close to black, and the "white" is far from white, so it sounds a bit odd when you say it. 16 shades of grey is what you get.

[JSWolf]

My H2O is 265 DPI with a 6.8" screen. It dithers better then a 300DPI PW3 with a 6" screen.

[cellaris]

Originally Posted by isaacbh

Is the 8" screen on the Kobo Forma the biggest available with 300ppi? I tried previously a 10.3" reader from Onyx, but with only 227ppi, text and fine lines were too blurry for my taste. Currently I have the original H2O, and for reading PDFs I need to massage the file with tools like k2pdfopt, which is not always ideal. I assume all companies source their screens from eInk, but I couldn't find anything there. Thanks!

There is also the Tolino Epos 2, which is the German brother of the Kobo Forma. The difference is that you can access Android and install some complementary reading program for PDFs (in addition to KOReader), such as Orion Viewer that works very well on the Tolino.

[rcentros]

Originally Posted by JSWolf

My H2O is 265 DPI with a 6.8" screen. It dithers better then a 300DPI PW3 with a 6" screen.

I'm currently reading a book on my Aura HD (which I think has the same screen, at least the same resolution) and, though I don't know exactly what "dithers" means, I can vouch for the quality of its fonts.

EDIT: Although comparing it directly to the original Tolino Epos' 300 dpi screen shows that the Epos is of a noticeably higher quality — though that may have more to do with lighting than dithering.

[JSWolf]

Originally Posted by rcentros

I'm currently reading a book on my Aura HD (which I think has the same screen, at least the same resolution) and, though I don't know exactly what "dithers" means, I can vouch for the quality of its fonts.

EDIT: Although comparing it directly to the original Tolino Epos' 300 dpi screen shows that the Epos is of a noticeably higher quality — though that may have more to do with lighting than dithering.

The Aura HD uses a Pearl eInk screen which is not as fast and the contrast is less then a Carta eInk screen. The Tolino Epos uses a Carta eInk screen. Carta is what the Aura H2O uses and what all glass backed 300DPI eInk screens are.

[isaacbh]

Originally Posted by rowe

I think that's right. I'd love there to be a 300dpi 13" reader, but E-ink are already struggling with quality control at pixel densities closer to 200 for the larger readers (seems most 13" screens have stuck dots).

Then I better not hold my breath... There is imo a market for a screen that fills the gap between an LCD and b/w eink, the best of both worlds really, something like Pixel Qi's transflective/reflective display for laptops/tablets. Too bad that never materialized.

[Quoth]

Carta with IR touch rather than capacitive seems to be the best white without frontlighting. Possibly best contrast.

Transreflective screens are only good for artificial built in light and bright sunlight. Inherently an LCD technology as it traditionally uses a rear light source or on small screens a mirror. The eink is opaque, though as I suspected, the rear has a dimmer negative image, so the white parts of the top can't have light reflected from a rear mirror as the rear will have the black particles. The white is no doubt the milky liquid.

Transreflective screens are really old and used on phones and PDAs originally.

[DNSB]

Originally Posted by Quoth

The eink is opaque, though as I suspected, the rear has a dimmer negative image, so the white parts of the top can't have light reflected from a rear mirror as the rear will have the black particles. The white is no doubt the milky liquid.

The old eInk screens used black particles and a milky liquid, newer eInk screens use both black and white particles.

[Quoth]

Originally Posted by DNSB

The old eInk screens used black particles and a milky liquid, newer eInk screens use both black and white particles.

Which is certainly opaque and will give a weak rear negative image and is useless for transreflective designs. Which was the point of my comment.
Thanks for update. So current screens, if anything, are even more opaque.

[DNSB]

Originally Posted by Quoth

Thanks for update. So current screens, if anything, are even more opaque.

Unless you get the JustTint film where they use a transparent liquid and the black balls are moved to the sides leaving most of the capsule transparent. Hopefully the attached gif will work.

[james_]

So, the question is.. what resolution is the JustTint film? It sounds perfect, you could put a low power EL backlight behind it which would work much better than side LEDs for large displays.

There doesn't seem to be any modules listed yet that you can get your hands on unless I missed it https://www.eink.com/modules.html