How the Kindle Paperwhite Works

Kindle Paperwhite measures 6.7 inches (169 millimeters) high by 4.6 inches (117 millimeters) wide. It is a scant 0.36 inches thick (9.16 millimeters for the WiFi-only model and 9.27 millimeters for the 3G). The WiFi-only version weighs just 7.5 ounces (213 grams) and the 3G weighs 7.8 ounces (221 grams) due to additional internal hardware.

The WiFi-only Paperwhite can connect to an 802.11b, 802.11g or 802.11n WiFi network and supports WEP, WPA, WPA2 or WPS (WiFi Protected Setup) security. The 3G can connect via either WiFi or a cellular 3G network, and is compatible with cellular networks in dozens of countries all over the planet. Unlike most 3G devices, you do not have to pay a monthly fee for the service. It's provided free of additional charge by Amazon.

On the aesthetic front, the color of the shell has been changed from a dark gray to black, and the screen from gray to a more stark white. The shell is plastic, and the back is rubberized to prevent slipping. The screen is 6 inches (15.2 centimeters) diagonally, like other Kindles.

The Paperwhite has a two-point, multi-touch capacitive touch screen. The home button on the front has been removed, so now the only two ways to interact with the device are the touch screen and a power button at the bottom of the device next to the power indicator LED (light emitting diode). To turn on the device and wake it up, you press the power button and then swipe the screen.

Also at the bottom of the device is a micro-USB port for connecting the device to a computer or other USB adapter for charging. You can move content to the device by connecting to your computer, but content for all current Kindles is automatically stored via Amazon's cloud service and can be downloaded at any time wirelessly for free. The Kindle Paperwhite comes with a USB 2.0 micro-B cable. The wall power charger that came with some previous Kindles is now available as an optional purchase, and does not ship with the device.

The Paperwhite's storage capacity is technically 2 GB, but only 1.25 GB is available for downloaded content. There is no way to expand memory on the device, but with Amazon's free cloud storage, you can delete and re-download your content at will, provided you are connected to a WiFi or 3G network. Amazon estimates that you can store around 1,100 books on the device.

As with all previous Kindles, Paperwhite uses E Ink technology, which employs microscopic black and white particles to draw text and images onto the screen. The particles are contained within tiny spheres, with an array of electrodes underneath. The black particles are negatively charged and the white particles are positively charged. When a negative charge is applied under a sphere, it repels the black particles to the surface, making that area appear black on the screen. A positive charge repels the white particles, effectively erasing the "ink" and making that area appear blank. These spheres and electrodes can also be used to draw 16-level grayscale images. In conjunction with a matte screen surface, E Ink makes for very smooth and readable text that resembles that of a book more closely than the text on a computer screen.

The Paperwhite has a display resolution of 768 by 1024 pixels, with 212 pixels per inch (PPI). Paperwhite also incorporates a new LED front-lit screen. The device's lithium polymer battery has estimated life of up to eight weeks, assuming you keep the light at brightness level 10 (out of 24), only use it for 30 minutes a day and turn wireless off when you're not actively using it. Other usage patterns can drain the battery faster, but a Kindle can run much longer on one charge than the typical phone, tablet or laptop, even with heavy use.

Speaking of the lit screen, read on to find out more about this improvement to the Kindle e-reader.

The most innovative thing about the Kindle Paperwhite is the front-lit screen with what Amazon is calling "light guide" technology. The display is made up of three layers: the E Ink display (innermost), the capacitive touch screen (middle) and the light guide (outermost) layers. The display layer is similar to previous Kindle displays, but with improved resolution and contrast. The multi-touch screen is a step up from the Kindle Touch's infrared (IR) touch screen. And the light guide is something new altogether.

There are four tiny LEDs built into the bezel at the bottom of the device's screen. These tiny lights point toward the display, and the light guide layer disperses the light across the entire screen. This top layer has been described by Amazon as being akin to a fiber optic cable flattened out into a sheet. It's imprinted with what they refer to as "nanoscale optical diffractive patterns" that direct the light across the screen and cause it to come out in certain areas, distributing it as evenly as possible downward onto the display. The imprinted guide pattern changes as it travels away from the light source in a way that ensures near-uniform distribution despite the fact that it's all coming from the bottom of the screen.

Lights usually prove to be a power drain, but battery life has been preserved by using low-power LEDs and engineering the device to use them efficiently. You can choose from 24 different levels of brightness, and even at the lowest, the lights are still on. The LEDs only go off when you turn the device off. This illumination allows you to use the Kindle Paperwhite in a number of settings, from bright outdoor sunlight to complete and utter darkness and everything in between. No other device on the market as of spring 2013 has a screen quite like it, although there are other e-readers with lit screens.

Amazon and fans of the technology contend that E Ink displays are easier on the eyes than back-lit LCD screens, which generally have LEDs that shine light toward your eyes. Amazon also states that the Paperwhite preserves the more paper-like nature of E Ink because the light guide shines the light inward toward the screen instead of outward. Anecdotally, people do find E Ink, as well as this front-lit screen, more pleasant and comfortable to view than a typically back-lit tablet. But there is still some debate on the matter, and studies haven't yet found a definite link between LCD screens and eyestrain. Modern LCD screens apparently refresh at a rate faster than our eyes can even detect. Some people report having no more trouble reading on LCD tablets than they do on the computer screens that they stare at daily. And a recent study found that reading on E Ink and LCD devices produced similar eyestrain results, and that image quality and resolution might have more effect on eye fatigue levels than type of display [sources: Hoffelder, Siegenthaler].

Tablets, however, are more subject to glare due to their glossy screens, making bright-light reading difficult. In many cases, the reading comfort level of different types of devices might just boil down to things like photosensitivity, glare and personal preference.

Aside from the obvious hardware similarities, there are lots of common features across all Kindles as of spring 2013. They include access to Amazon's Whispernet service for downloading content wirelessly, eliminating the need to download content via a computer. Whispersync allows the Kindle to sync to your last read page across multiple devices (say, if you have a physical Kindle as well as the Kindle apps on your computer and smartphone). From Kindles, you can even surf the Web, albeit slowly, on a limited-function "experimental" Web browser.

But a few features differentiate the Kindle Paperwhite from its predecessors. One is the slick graphical interface that shows your books, and potential purchases, as book cover icons rather than text-based lists of items.Since the only ways to interface with the new device are the power button and the touch screen, you navigate the Paperwhite via screen icons, and touch various parts of the screen to make selections and switch pages.

While within a book or periodical, touching the top of the screen brings up the toolbar icons, touching a thin strip on the left takes you back a page, and touching anywhere to the right of that strip (the majority of the screen) takes you forward a page. You can also swipe across the screen right to left to page forward, and left to right to page back, if you prefer. In any situation where you need to type, say to do a search, a virtual keyboard pops up.

The toolbar includes the following virtual buttons:

Home (a house icon) -- As the name implies, this takes you back to your home screen, which on the Paperwhite displays your library as a series of book icons. There is also a row of featured Kindle Singles (smaller book icons) below that for possible purchase, along with a banner ad below the Singles. You can opt out of seeing the banner ads at any time for a $20 payment to Amazon.

Back (a left-facing arrow) -- This button takes you back a page.

Screen brightness (a light bulb) -- The screen brightness button allows you to adjust brightness from the settings of one to 24.

Kindle Store (a shopping cart) -- Touch this icon to purchase books, provided you are connected to a network via either WiFi or 3G.

Search (a magnifying glass) -- Select from various sources, including your current book (if you are within a book), the Kindle Store, a dictionary and Wikipedia. The search function also brings up a virtual keyboard for text entry.

Menu (three horizontal lines) -- Menu brings up a relevant menu based on what you are doing at the time you hit the button (whether reading a book, on the home screen or elsewhere). It allows you to do things like change settings and surf the experimental Web browser.

If you tap the top of the screen within a book, there is a secondary toolbar that comes up underneath the main toolbar. This includes the following icons:

Both toolbars have slightly different choices for periodicals, including icons to display highlights, to show hierarchical lists of sections and articles and to save an article to a My Clippings file, where clipped articles, notes, bookmarks and highlights reside. Go To, X-Ray and Share are omitted for from the periodicals toolbar.

Other new features:

The Kindles still available through Amazon as of March 2013 include the basic Kindle for $69, the Kindle Keyboard 3G for $139, the Kindle Paperwhite for $119 and the Kindle Paperwhite 3G for $179. Paperwhite is slightly smaller than the current Kindle Keyboard 3G and slightly larger than the basic Kindle. The Kindle Paperwhite is quite similar to the now discontinued Kindle Touch in size, appearance and functionality, with a couple of key differences.

As the name implies, the Kindle Keyboard 3G has a built-in physical keyboard. The cheapest base Kindle has a five-way controller underneath the screen for navigation. Both also have page forward buttons and page back buttons on either side of the device for flipping through reading material. Kindle Paperwhite eliminated all these buttons in favor of the touch-screen interface.

Kindle Touch was the first touch-screen Kindle, and Paperwhite has entirely replaced it. The Paperwhite has a two-point multi-touch capacitive touch-screen, whereas the Touch had a less responsive infrared (IR) touch-screen. The bezel is a little thinner on the Paperwhite because there is no longer the need for built-in IR transmitters to detect your hand motions on the screen. The new capacitive touch screen has more in common with the touch screens of most tablets, and is possibly the result of Amazon's acquisition of the multi-touch hardware manufacturer Touchco in 2009.

With the Paperwhite, the resolution jumped from the 600 by 800 pixels of all previous Kindles to a crisper 768 by 1024 pixels. Pixel density increased from 167 PPI to 212 PPI, about 62 percent more pixels than the Touch. Contrast has increased significantly from earlier models for sharper text and images. The number of fonts available increased from three to six.

The most obvious change is, of course, the lit screen, which no other Kindle has as of the Paperwhite's debut. Also, unlike previous models, the Paperwhite can switch between portrait and landscape views.

But not every change has led to a new capability. Kindle Paperwhite has lost the speakers and audio jack of previous models like the Kindle Keyboard 3G (still available), the Touch and some other discontinued models. This means you can no longer listen to audio books or have the device read the books to you digitally via a text-to-speech feature. Memory has also gone down a bit compared to the Touch and Keyboard, from 4GB to 2GB (or from 3 GB to 1.25 GB of user-available space).

Since the 5-way controller model was introduced, most Kindle models have also featured on-screen advertisements. While you can opt out of ads via payment, they mostly appear when you are not reading, so you can decide after a bit of use whether they annoy you enough to shell out more money.

There are some notable well-reviewed alternatives to the Kindle, and likely more to come. Competitors with built-in front-lighting include the Nook Simple Touch with GlowLight e-reader, whose price was dropped to $119 when the Paperwhite came out, and the Kobo Glo, which is priced a little higher at around $150. Both feature IR touch-screens and E Ink displays. The Kobo matches the Paperwhite's resolution, whereas the Nook's resolution is that of older Kindles. The Nook is lit via LEDs at the top of the screen and the Kobo Glo via LEDs at the bottom of the screen. Both reportedly have fairly even light distribution like the Kindle Paperwhite. Both are ad-free. The Nook site makes a point of saying that it is both ad-free and comes with a wall charger.

Another possible choice is the Sony Reader PRS-T2, which has IR touch-screen interface and E Ink display. It doesn't come with a built-in light and has 800 by 600 pixel resolution, which makes it more comparable to the other available Kindles. With a price between $130 and $135, It is also a tad more expensive than the Paperwhite or Nook Simple Touch with GlowLight, despite its lack of light.

All three of these competitors are similar in size and functionality to the various Amazon Kindle e-readers. They all let you sync with apps on other devices, and also all allow you to lend certain authorized books to other people with the same devices. They best the Kindle in one area: All these other e-readers come equipped with micro SD card slots to expand memory up to 32 GB.

The types of e-book formats that can be read on all the devices vary a bit, so you can't necessarily switch devices and move your content. All of the devices have access to sizeable libraries of e-books, although Amazon's library is currently the largest.

Another possibility is to eschew a dedicated e-reader altogether and use a multipurpose tablet, which is equally portable and can perform a host of other functions. They typically have back-lit color LCDs (liquid crystal displays), which would lend themselves better to textbook, cookbook, magazine and comic reading since those media generally include color images. Some choices are Google Nexus 7, iPad and Amazon's own Kindle Fire family of tablets. They can all be used to read e-books via e-reader apps, including the Kindle app. And the less expensive tablets are close to the price of the most expensive Kindle Paperwhite at this point.

One disadvantage of LCD tablets is that they do not have nearly the battery life of E Ink readers. They usually last only hours rather than days or weeks on one charge. They are also quite a bit heavier. Tablets also have greater problems with outdoor or other bright light visibility due to glare, but do not have two E Ink related issues: ghosting (faint leftover images of text from previous pages) and flashing (a brief flash that occurs as an E Ink screen resets). However, those E Ink issues do not render a page unreadable, and they are apparently less noticeable on the newer e-readers.

You can avoid an extra device purchase altogether and read Kindle and other e-books on your computer or your phone. Amazon has created free Kindle applications for pretty much all computing devices. And with Amazon's Cloud Reader, you can read your books through most Web browsers without any downloaded software. The Kindle itself is a bit of a loss leader, and Amazon actually makes its money from book sales rather than hardware sales.

As of first quarter 2013, the Paperwhite has been well received and compared favorably to its competitors, including other Kindles. There have been some complaints about a slight unevenness of the light at the very bottom of the screen (the location of the LEDs), but that complaint also occurs for the other front-lit devices. Kindle usually gets high marks for having a slightly more uniform light distribution than the others. The capacitive touch screen and excellent resolution also put it a smidge above the crowd.

The increase in the prominence of ads is one disadvantage of the Kindle Paperwhite, but one that doesn't apply if you've paid the extra $20 opt-out fee. The fact that you have to pay extra for a wall charger (whereas it came with the device before) is also a point of contention. Perhaps this was to reduce cost, or perhaps the wall charger wasn't thought necessary due to the device's long battery life, but if you travel a lot, you may want to invest in the wall adapter.

The Kindle arguably wins on sheer numbers of available books and periodicals. Aside from millions of books and periodicals for purchase, Kindle also has nearly 300,000 books available for lending to Amazon Prime members. As of early 2013, an Amazon Prime account is $79, and aside from book borrowing, it entitles you to free two-day shipping on many physical items and free streaming of lots of movies and TV shows.

You can also upload PDFs and certain other file formats to your device by e-mailing them to a special personal address that you can find in your Kindle settings. Those documents also end up in the cloud, where you can read them via a Web browser.

There are many viable choices if you want to be able to read e-books away from your computer. You can narrow the choice down a bit by deciding whether you want a dedicated e-reader or a more multipurpose device on which you can also play games and surf the net with ease. Whether you are okay with black and white or would rather have color, whether or not you require audio, how often you want to have to charge the device and your budget are also deciding factors. Once you know your parameters, you can check out the various devices and see which appeals to you most. In the dedicated e-reader arena, Paperwhite is definitely a contender.