When Apple released the iPad in 2010, it entered the book publishing competition by introducing the iBooks app and pitching the new tablet as an e-reading device. Book publishers and authors alike wondered if the iPad would accelerate the sales of e-books and possibly even challenge Amazon's Kindle bookstore. Amazon presently maintains its crown as the largest retailer of e-books, but the company does not publicly release Kindle sales data. Meanwhile, the competitive landscape of e-readers has changed.

In the wake of the third-generation iPad release, most reviewers were transfixed by its high-resolution "retina" display, which delivers incredibly sharp text and images on the tablet. We decided that additional examination was warranted, and Amazon's recent Kindle App update brought support for the retina display that some say leaves e-ink blotchy with embarrassment. So we set out to answer the question: does the new retina display make the iPad the new must-have e-reader? Does the retina display trump e-ink when it comes to reading?

We compared a third-generation Kindle to the new iPad (using the iOS Kindle app) based on features that matter for reading, such as screen brightness, text rendering, and backlighting. This article is not a full-blown e-reader comparison, but instead an evaluation of the screens for people considering these devices to read books.

How does book text look on the retina display?

The iPad's increased pixel-per-inch count delivers a new level of sharpness and detail to images and text. To demonstrate, we loaded up an e-book on the first-generation iPad and compared it to the third-generation iPad. As we noted in the Ars iPad review, the new iPad has doubled its resolution in both directions from 1024x768 to 2048x1536, and we can really see the difference. This higher pixel density means that apps and websites that previously relied on aliasing to smooth out the text can now rely on sharp-looking text at a wider range of sizes.

Dr. Raymond Soneira, president of DisplayMate Technologies, recently published his full analysis of the iPad's new display. The report states that the display of text in the new iPad is "incredibly razor sharp," but that the new resolutions of the iPad may not be altogether necessary. He cites several reasons why Apple's retina pixels might be overkill: not everyone has 20/20 vision, holding the iPad further away than recommended nullifies the benefits of the detail, subpixel rendering is truly the way to improve a display, and most people seem to be happy with 1600x1200 displays on large screens.

The current pixel density will render a lot of detail, but the only way to add more clarity on a display is to perform subpixel rendering, says Soneira. So you can be assured that text looks pretty sharp on the new iPad, but there are various scenarios in which all that sharpness may not matter.

Text rendering

Although the text on the new iPad is certainly sharper than that of its predecessors, the display on the original iPad still performed well enough for long periods of reading. Flipping through several pages of the same book on the first- and third-generation iPads felt pretty much the same when it came to actually reading. We should also note that we have used the Kindle app on the original Kindle over the past several years on a regular basis without much effort or strain.

Amazon's latest Kindle features a display resolution of 600x800 pixels on a 6-inch screen using e-ink and Amazon's proprietary font-rendering technology. The Kindle is eclipsing competitors in the e-reader market, and even helping e-books surpass print sales. A Pew Internet study found that tablets and e-readers are becoming extremely popular among the general population, as ownership nearly doubled in the 2011 holiday period.

The Kindle displays fewer pixels than the iPad, but a lower resolution on e-ink doesn't mean it's not sharp. In order to understand e-ink's appeal to readers, let's take a look at how it works.

E-ink is considerably different from LCD displays: it's made up of microcapsules (each about the width of a human hair), which are set in gel or liquid inside the screen. These microcapsules are controlled through a process of electrophoresis. Each microcapsule contains smaller ink granules inside each one. These ink granules (which come in various grayscale shades) are charged positively or negatively. By changing the electric field between the electrodes, it's possible to make the white or black granules move to the top of a capsule. These microcapsules set into the screen are squeezed between electrodes. A circuit controls each microcapsule individually, and can therefore display images—and most importantly, sharp text. Below, you can see a photo of the title page of the book title we compared for our test.

Soneira says e-ink offers several features that make for good reading: "The e-ink displays have a natural anti-aliasing that eliminates the jaggies that are annoying at lower resolutions."

While there are numerous debates about how sharp text needs to be in order to create a proper reading experience, the human eye and brain are pretty good at interpreting text on screens. The brain's own top-down processing works quickly to try to interpret shapes and images. Here's an example in the visual puzzle below:

What is the image you see first in the black and white drawing? Some users see two human profiles, and some see the shape of a table. Some of us will even identify it as a letter I. The brain is constantly looking for shapes that are familiar, and in the case of text, letters can look quite fuzzy and the brain will still be able to identify them correctly.

On LCD screens, anti-aliasing helps trick the eye into seeing smooth edges on letters, even if the pixel display is a little fuzzy. The Kindle's proprietary text rendering is very good at creating sharp edges on letters, though at very small text sizes, text looks grainy. Sure, you may be able to detect the jagged edges of the fonts if you bring the device right up to your face and read at a smaller font size, but who reads their copy of The Girl with the Dragon Tattoo that way? Font sizes can be increased to very large sizes to help those with vision problems, and at its native resolution, the Kindle performed well against the iPad.

Reflective vs. backlit displays

E-ink is designed to imitate the non-reflective qualities of paper, though it can also generate annoying effects like ghosting. In the case of of Amazon's Pearl e-ink displays (found in all models after the third-generation except Kindle Fire), the display is able to offer a 180-degree angle, which also resembles the experience of reading on paper. Amazon has built its own proprietary software and rendering stack in order to render text on its devices.

Ars spoke to Sriram Peruvemba, chief marketing officer at E-Ink Holdings (which provides e-ink technology to multiple e-reader device makers), about some of the ways in which Amazon is able to display text on the Kindle without subpixel rendering. "Subpixel rendering is dictated by the transistors in the TFT backplane. In LCD there are typically 3 subpixels, each with its own transistor so you can address individual subpixels," he said. "In the case of our monochrome Pearl platform used in the Kindle (all models except Fire), Nook, Sony, Kobo and others, there is one transistor per pixel and there are no subpixels per se."

As a subjective benchmark, we read on both the Kindle 1 and the Kindle app on the new iPad for three hours on each device. We repeated this on three occasions to observe our results. As you can see in the previous image, e-ink renders its text with clarity and a good amount of contrast. We could read text on the Kindle screen from multiple angles both outdoors and indoors (with decent indoor lighting, of course). When we tried the smallest and largest end of the font sizes available, it was possible to notice imperfections in the way the letters render, but it didn't prove to be a distraction while reading. Font sizes in the middle range looked quite clear. The Kindle has no settings for contrast or brightness and, as such, we needed to use indoor lighting to see text properly under low-light conditions.

Viewing angles, brightness, and more

LCD devices begin to lose brightness when tilted past a certain angle, and in the case of the iPad, DisplayMate's report states that the iPad lost 57 percent of its brightness after changing the viewing angle by 30 degrees. The Kindle, on the other hand, has a very wide angle of 180 degrees, since it doesn't have any backlighting. In this respect, the Kindle outperforms the iPad easily. The reflective properties of each screen's surface also matter. The iPad's glossy screen can practically act as a mirror. That much glare does not make for a fun reading experience, and the Kindle's e-ink screen doesn't generally suffer from this problem.

Does a backlit screen matter? Only inasmuch as whether you prefer fluorescent or natural light when you read. If you are visually impaired, the iPad's accessibility features (and the Kindle app's white text on black background) can offer an advantage over the hardware Kindle. If you tend to get headaches while reading backlit screens or suffer from eye strain, however, you may want to reconsider long sessions of reading on the iPad screen. Still, most users should be able to read decently well under both devices. Many of us now regularly spend long hours in front of work PCs, televisions, and video games, so adding a bit of reading on an iPad can either seem negligible or just-too-much, though e-ink does have a very comforting effect in our experience.

Playing with the settings of e-reader apps like Kindle also produced some better results for some readers. Changing the display to the sepia or white-text-on-black background does tend to offer relief for those who experience eye strain and fatigue from the sometimes blindingly white retina display.

Pablo Defendini, a product manager at Safari Books Online told us that choosing e-ink over a backlit screen is a matter of preference: "Some people who like e-ink devices for long-form reading now might reconsider a backlit display with retina-class resolution. Body text on the new iPad's retina display is dramatically better than on previous iPads, and is comparable to what you see in print."

"For e-ink displays, make sure you have sufficient ambient light," Soneira added, "because they use ambient light like paper. For LCDs, carefully adjust the screen brightness for comfortable reading. I don't recommend using the automatic brightness setting on tablets and smartphones because they are functionally useless."

We avoided comparing contrast between the Kindle and the new iPad—it's not a fair comparison because of how contrast is usually measured. LCD contrasts are measured in darkness, while e-ink is measured with indoor light. (In total darkness, e-ink is not visible at all.) We found the contrast on the iPad to be quite good, and the DisplayMate report measured its contrast ratio in low ambient light at 877 to 1.

Feature Amazon E-Ink Kindle (3rd-gen) 3rd Gen iPad Pixel density 167 pixels per inch 264 pixels per inch Color 16-level grayscale Millions of colors; higher color saturation than iPad 2 Text rendering Proprietary software and rendering stack; no subpixel rendering Subpixel rendering of text is available, though not implemented by every app yet Screen 6 inches (Wifi model) 9.7-inches Weight 5.98 ounces 23 ounces Brightness N/A; reflective display 421 cd/m2 Viewing angle 180 degrees 57 percent decrease in brightness at 30 degrees Battery life (with wifi enabled) About 3 weeks About 10 hours

Other battlefields in the e-reader wars

What really makes an e-reader stand out is its user experience. Aside from screen resolution, there are many other elements that make an e-reader a fun and durable reading object. If a device lets us read on it for more than a handful of minutes, extending into hours, then it's probably got something good going for it.

Portability makes for a good e-reader. Users often complain that the iPad is too heavy to hold for long periods of time, and that may be true, but those who finished Don Quixote on paper did so without spraining their arms and lived to tell the tale. The Kindle, on the other hand, has only gotten smaller and thinner over time. The weight of the device is a matter of user preference, though it should be noted that many staffers at Ars do appreciate the lighter weight of the Kindle.

Battery consumption will also influence how much enjoyment you can get out of a device. Depending on your wireless settings, you can now get a full month's charge from a Kindle, while the iPad can push itself a little past ten hours. Of course, if you don't mind recharging often, the battery technology inside each device is also quite different for each. The iPad's battery (and components) weigh in at almost a pound and a half. That's a big boy when compared against 6 ounces for a Kindle. But not everyone will necessarily care about this; some users prefer a heftier device that feels solid, while some may be more concerned about its portability for work or travel.

So should I buy an iPad as my e-reader?

If you love reading and are looking to invest a chunk of money into a device as a dedicated e-reader, then the iPad is not your best bet. The value you can get from devices like the Kindle (or several other competitors like the Sony Reader or Kobo), will allow you to save money to spend on what is presumably your main passion: books. The iPad's retina display is sharp and bright, but the display is unlikely to be the sole deciding factor for spending more time with the books you love.

The trouble comes when you start to think of your e-reader as more than an e-reader. E-ink Kindles are abysmal at Web browsing, for example, and they don't run popular apps and games like the iPad and other tablets on the market today.

Things won't always be this way, though, because color e-ink and other technologies are still on the horizon. There are other types of reading, like webpages and magazines, that matter just as much as books to many readers, too. For those needs, an iPad's retina display will display images and text like a champ. But if your focus is on reading many books for many hours, e-ink still provides readers with the best support.

Note: We updated the comparison table to specify pixel density for each device. We also fixed an issue where the two comparison photos of the title pages on iPad 1 and 3rd-gen iPad were transposed.