In my earlier post, I’d put down my thoughts on the Kindle as a device. I didn’t discuss its e-ink display except for saying that it is wonderful. This post talks about my observations of and comments on its screen in greater depth.
The technology behind the screen is that of e-ink. It essentially consists of thousands of microcapsules sandwiched between two electrodes that span the entire surface of the screen. The upper electrode is transparent while the bottom electrode forms the base for the pixel matrix. Since each microcapsule contains thousands of white and black particles, which are oppositely charged, the two electrodes combined with the display driver are able to make each pixel appear white or black depending on the applied charge.
One of the main advantages over a traditional LCD or AMOLED display is the complete absence of any backlighting. The e-ink display uses ambient light just like regular paper. Another significant advantage is that unlike an LCD or AMOLED screen, the e-ink display doesn’t have to be refreshed to maintain the drawn image. So in effect, to display static images or text, no power is consumed. Only while redrawing the screen is power consumed. So usually devices(like the Kindle) with e-ink displays provide for phenomenal battery life.
Now, that the basics are out of the way, let us move onto the screen of the Kindle.
1. Kindles’ screen has 16 levels of greyscale which makes for good renderings of images. In fact, each time you put the Kindle to sleep, it puts an image up on the screen since it wouldn’t take power to display it. Some of these images are quite detailed and intricate as you can see in the below photo.
2. Kindle uses some sort of text smoothening to make reading easier. It is like clear-type on windows and gets rid of all the jaggies around all letters. Though I havent used any of Sonys’ ebook readers, I am told that this text smoothening is one of the differentiators for Kindle.
3. Because e-ink is not backlit, but instead uses ambient light, reading out in the sun is a non-issue. Actually, the brighter the ambient lighting, the better the display seems unlike LCDs and AMOLED screens. Also, Kindle doesn’t have a glossy screen surface – it has matte. So glare is also not a problem.
4. Another aspect of the Kindle screen that goes a long way towards making it more paper like is the closeness of the text to the surface of the screen. Unlike LCDs or AMOLEDs, there don’t seem to be multiple surfaces of glass or substrate in an e-ink screen which make the rendered text appear well below the outer surface.
5. This is a minor quirk but nonetheless interesting. There are several actions on the Kindle that you can perform which refresh only part of the screen and not all of it. Examples would be dropping the menu while reading a book or browsing through your collection of ebooks(in which case the menu and toolbars are not redrawn but remain static). In all of these partial redraws, there is always a slight degradation of quality.
Take the case of activating the menu. To begin with all the text on the screen is uniformly rendered and is equally contrasty. Now, drop the menu down and take it back up. If you observe only that part of the screen which draws the menu is refreshed. The text in this region is redrawn and appears just as it used to before the menu was dropped.However, the text on the remaining region of the screen is slightly washed out. I wouldn’t expect most people to even notice it and it certainly doesn’t detract from the reading experience.
Another case is that of the toolbar. While reading a book, hit the Home button. This will redraw the entire screen along with the menu and toolbars at the top and bottom of the screen. This first drawing of the home screen is almost blemish free(though if you look closely enough, you can make out faint traces of the progress indicator of the book you were reading on the toolbar). Keep an eye on the page numbers on the toolbar. Now, move back and forth a few pages. In the photos below, I ve moved from ‘Page 1 of 6’ to ‘Page 6 of 6’. In the first photo, see how bold and well rendered ‘1’ is. In the next photo, look the the first ‘6’. Notice how washed out it is? If you observe carefully, you will also notice ghosting of the number drawn here. It is most apparent when you have a digit with a small footprint replacing one with a much larger footprint, say for example when you go to page ‘2’ and come back to page ‘1’. Behind the washed out rendering of ‘1’, you can make out faint traces of ‘2’.
I would put both these cases down to the nascency of the technology and the way that Kindles display driver works.
6. Lastly, I’d like to point out the screen ‘flashing’ each time a full redraw occurs. So this occurs only when turning pages and when opening an ebook from the home screen or closing it to return to the home screen. These flashes dont occur when there are partial redraws, such as when the menu is dropped down or when you type notes. I suppose that the flashing ensures uniformly drawn text and images. Using a stopwatch, I estimated that each flash takes about 250-300ms, long enough to be noticeable but short enough to not be a bother.
One of the reasons that I put this post together is because, e-ink is a completely different technology from the other existing ones. There are no similarities or commonalities between them that I know of. Also, for me, this is the first gadget I’ve used that uses a e-ink screen. So, in case you all out there notice something new and different that I may have missed out, include it in the comments.