E-inks are fundamentally analog, so theoretically you could have as many shades of gray as your timing resolution allows, but basically all the commercial controllers available abstract the display as a dumb framebuffer so you can't really access their fundamental operation of "make this pixel slightly whiter or darker.
That depends on what you exactly mean by "controller". The hardware controller typicaly has capability of exposing selected pixels to essentially arbitrary voltage level for specified amount of time and the framebuffer abstraction happens on the driver level.
The majority of dev kits and modules available abstract away that level and provide something not unlike a regular LCD where you just send it raster images; the driving waveforms etc. which are needed to do effects like this are abstracted away, and the details are kept secret.
Any examples? I've only played with Waveshare screens/drivers a little, but I'm pretty sure I saw the LUTs defining voltage levels and times on the "user side", e.g. within the examples code. And from a YT video that shown how to drive those screens at 3FPS (didn't try it myself yet), I assume those are the actual LUTs that convert abstractions into voltage control.
So many (all?) do this dumb thing on a page update where they write all black and all white several times then write the image. There can't be a good reason for that - they can also put up a dialog popup and erase it without all that drama! Its like they all took the demo driver and shipped it
The full black/white is to "cleanse" --- since the material itself is stateful, pixels will drift slightly after several writes and cause ghosting/graininess if you don't eventually reset them all to a known state. It doesn't have to happen on every refresh, however.
I got a kobo aura one (cracking bit of kit) for christmas, it doesn't have the prounounced flash to white then load at all, it's near instant.
Also 300ppi is the sweet spot on an 8" display it's basically a near perfect paperback analogue and has a blue to orange backlight shift keyed to time of day.
I've been experimenting with epaper recently, controlled by an ESP8266 device. The following (short) video shows a full-refresh of an image loaded over HTTP:
On a Kindle Paperwhite it is an option called Page Refresh under your Reading Options. It'll occasionally do a wipe, for example when a page has images but not not often enough to be annoying.
I don't have the Paperwhite, but this option was present on earlier models too. I found it more annoying to have inconsistent page turn latency than to have consistently slow page turns.
My partner and I both got a Kobo, we're very happy with it. We use Calibre to manage our collection. Haven't tried DeDRM yet though. I got the Kobo Aura ONE, and she's got the Kobo Aura H2O. I actually prefer the 6.8" yes it is smaller but it lays better in the hand and is easier to take with you (fits better in the pocket). Its also about 50 EUR cheaper.
Some disadvantages: macOS doesn't have always recognise the device, it has 2.4 GHz WiFi only (put if off to save your battery). The Kobo's also have that screen refresh feature btw you can reduce its effectiveness if you're reading a lot.
Immediately after you bought it, check out the coating of the screen very carefully. I send one ONE back because it had a minor damage to the coating which caused bleeding. I found that distracting, YMMV. The 2 devices got it as well, but less severe and it depends on how you hold the device whether you notice it.
I have Onyx Boox Darwin 4 with hi-res display (6" at 1448x1072). I'm happy with it after 3 previous e-books: sharp display, built-in light, touch, stock android with Google Play, 2 cores, 8GB flash. The only misfortune is lack of my native language in UI.
It has 8 GB how is that not enough in between charges?
Kobo and Amazon don't contain *SD options but other e-readers do [1].
As insinuated, I find it is overrated. You can even run Calibre in Docker [2] to serve it over HTTP(S). And as you know, Kobo have a web browser. So you could put the books you're likely to read on your Kobo (8 GB is a lot) and serve the rest via that way. You could also serve the content over your phone via USB OTG.
If you're off the grid for a long time, I actually recommend something else instead: put your smartphone off, e-reader on, and keep a (at your option relatively, to <3 your battery) charged powerbank with you. Not necessarily for your smartphone, but for your e-reader!
I know some publisher's don't use DRM (like Tor). I was wondering if maybe Kobo had licensed Amazon's DRM for the newer DRM that doesn't have a crack yet (as far as I know, but I haven't checked in a few months).
