Dr. Raymond Soneira of DisplayMate Technologies has made it his mission to suss out the best smartphone, tablet, HDTV, and multimedia displays from the worst with his Display Technology Shoot-Out series. Here, the best of the tablet readers fight.
A new wave of Tablets has arrived just in time for Christmas… But as we have seen many times before, most new Tablets are poorly thought out contenders that just wash away with the next wave. To survive (let alone succeed) in this incredibly competitive marketplace you had better have a really good "reason de existence." The Amazon Kindle and Barnes & Noble Nook series of Tablets clearly fall into this category because they both started by providing a great reading experience with excellent E-Ink displays that behave like electronic paper. But these are pretty much restricted to displaying printed text because of their very limited imaging and graphics capabilities (black and white, 16 intensity levels, and very slow speed screen updates).
In order to stay competitive with the incredibly successful Apple iPad the next logical step was to offer a color LCD display. Tablets are essentially large portable displays – so if you are going to offer a product in this area you had better do the display right! Apple did that from day 1 with the iPad. For Tablets the display is the single most expensive and important hardware component because it determines the quality of the visual experience for every application on the Tablet. In this very hot ultra-competitive category an outstanding display is the single best way for manufacturers to make their Tablets stand out from the competition because the display enhances or degrades the appearance of everything that runs on the Tablet. Cutting corners, costs and quality for the display is a serious mistake because it results in sub-standard image and picture quality for everything that runs on the Tablet. Two examples of what not to do are the Motorola Xoom and Acer Iconia, which had low-end LCD displays and tested poorly in our 10 Inch Tablet Display Technology Shoot-Out.
Manufacturers now seem to have gotten this message because many of the latest Tablets are offering improved IPS LCD displays, the same screen technology that Apple uses in the iPad and iPhone. It offers wider viewing angles, better image contrast, and faster response times than the cheaper LCDs used in many products. IPS stands for In Plane Switching, which has two transistors for every sub-pixel. It was developed by Hitachi, but LG is now the world's leading manufacturer of IPS LCDs, and the principal supplier of displays for the iPhone as well as the Tablets in this Shoot-Out (but most Tablets have more than one supplier). Other manufacturers offer similar technologies that are often called IPS displays, such as Fringe Field Switching by Hydis and Plane Line Switching by Samsung.
The two new Tablet stand-outs for this Display Shoot-Out are the Amazon Kindle Fire and the Barnes & Noble Nook Tablet. It was nice to hear that they both feature IPS LCD displays like the iPad. But IPS displays are not all the same and do not perform equally because, like cars, they are actually complex assemblies that include lots of options and variables. So we decided to see how these newbies compare with the grand-daddy of them all – the Apple iPad…
To compare the performance of these IPS displays we ran our in-depth series of Display Technology Shoot-Out tests on them. We take display quality very seriously and provide in-depth objective side-by-side comparisons of the displays based on detailed laboratory measurements and extensive viewing tests with both test patterns and test images.
The Kindle Fire and Nook Tablet are competing head-to-head with similar price points, feature sets, and 7 inch screens. The iPad 2 has a much higher price point, much greater feature set, and much larger 9.7 inch screen – non-the-less these Tablets are competing in functionality and particularly for finite consumer dollars. It remains to be seen whether the Kindle Fire and Nook Tablet grow at the expense of the iPad, or whether they just expand the market for Tablets. I predict the latter… Tablets are so useful that there is plenty of room for 7 inch, 10 inch, and even 12 inch screens – the first for extra portability and the latter for professional and office applications… and there are lots of people that would own more than one size based on their varying needs. One of the more credible rumors flying around is that Apple will introduce a 7-8 inch iPad in 2012. I hope so…
In this Results section we provide short comparative Highlights for each Tablet display based on the comprehensive lab measurements and extensive side-by-side visual comparisons using test photos, test images and test patterns that are presented in later sections. The Comparison Table in the following section summarizes the lab measurements in the following categories: Screen Reflections, Brightness and Contrast, Colors and Intensities, Viewing Angles, Display Backlight Power Consumption, and Running Time on Battery.
One major issue for most Tablets has been that the manufacturers are all scrambling to get their products to market so there isn't enough time to properly engineer everything. It's clear that this was the case for both the Kindle Fire and Nook Tablet – ship by Thanksgiving and provide patches, tweaks and enhancements later. That's understandable, while both the Kindle Fire and Nook Tablet are quite functional, they are both going to need lots of fixes and tweaks. It's possible that the serious display issues we found for the Kindle Fire will be improved in future software updates.
We'll begin with the iPad because it's the standard that all other Tablets are compared to… The iPad 2 has an excellent display, virtually identical in performance to the impressive iPhone 4 Retina Display, with a somewhat higher pixel resolution but a much lower pixel density of 132 ppi due to its much larger screen size. The iPad 2 IPS LCD display is fairly well calibrated and delivers bright images with excellent contrast, reasonably accurate colors and very good Viewing Angle performance with small color shifts but a large decrease in Brightness, which is the case even for the best LCDs. A major shortcoming is a reduced Color Gamut, but the iPad 2 improves on-screen image color saturation by steepening its intensity scale. For more details see the dedicated iPad 2 LCD Display Shoot-Out.
In principle, the LCD on the Kindle Fire is a fairly good display, comparable in most respects to the Nook Tablet and iPad 2 – but it has two major flaws, and only one of them is fixable with a software update.
Amazon advertises that the Kindle Fire has an "anti-reflective treatment" but our lab tests found it to have among the highest reflectance levels we have ever measured – it's 70 percent higher than the iPad 2, and more than double the reflectance of the Nook Tablet. That may not matter much if you are reading in bed but it's likely to be a significant factor indoors and especially outdoors. It's also a surprising piece of puffery for Amazon – who's generally a very straight shooter…
Another big disappointment for the Kindle Fire is the Gallery, the native application that is used for viewing photos and images. First, the gray-scale is way off, and overdriven so hard that significant picture detail will be lost with bright images. It's very similar to what happens with an over-exposed photograph – all of the bright content appears washed out or even lost all together – see the screen shots in Figure 4 below. Like the Nook Tablet, the Kindle Fire uses a version of Android for its OS, but the User Interface on the Kindle Fire is much closer to vanilla Android – and most of the time it's much nicer than the Nook's own UI. But the Kindle Fire still carries a major flaw in Android that I pointed out almost 2 years ago with the Nexus One, and which Google acknowledged. The Gallery provides only 16-bit color – that's 65 thousand colors not the "16 million colors" that Amazon advertises. It also produces noticeable steps (called false contours) in some images. While the display hardware can do 24-bit color it doesn't show up on-screen in the Gallery viewer due to the software design. It's about time that Amazon and Google fix this… Fortunately, the Web browser on the Kindle Fire does support full 24-bit color for web images.
Another display related issue is that the chunky menus in the Kindle Fire Gallery eat up 100 pixels of the screen, so photos only get 500 of the screen's 600 vertical pixels. If you display a standard 4:3 digital camera photo it only fills 54 percent of the screen and a 16:9 photograph only fills 72 percent of the screen. To fix this the UI needs to be updated so that the menus disappear after a few seconds the way they do in other parts of the Kindle Fire UI.
The LCD on the Nook Tablet is also a fairly good display comparable in most respects to the Kindle Fire – but Barnes & Noble has done a much better job in pulling everything together into a nice all around display.
Barnes & Noble advertises that the Nook Tablet has "reduced reflection and glare" and they have clearly done their homework on this one because it has the lowest reflectance of any Tablet we have ever tested – the iPad 2 has 28 percent higher reflectance and the Kindle Fire has more than double that of the Nook Tablet (lower is better).
The Nook Tablet also has a very good factory display calibration. Its gray-scale is actually more accurate than most living room HDTVs. The White Point at 6,016K degrees is somewhat more yellowish than the 6,500K standard – that was most likely done in order to increase the screen's maximum brightness, power efficiency, and battery run-time.
Like the Kindle Fire, the Nook Tablet also uses a version of Android for its OS. But unlike the Kindle Fire the Nook Tablet delivers very smooth and accurate 24-bit color on-screen, including for its Gallery. Photos and even test patterns are free of the ugly image artifacts seen on the Kindle Fire. The reason is that the Nook Tablet doesn't use the Android Gallery but rather developed its own. Unfortunately, that has a down side…
Barnes & Noble has developed its own distinct user interface for the Nook Tablet – the Kindle Fire is much closer to vanilla Android. Unfortunately, it doesn't work anywhere near as well and still needs lots of work. In particular, the User Interface for the Gallery is primitive and combines all of the photos and videos into one gigantic grid. The only way to organize photos and videos with Folders is through a cumbersome "My Stuff" User Interface that is buggy as well. We use hundreds of test patterns, test images, test photos and videos for the Shoot-Out, so dealing with this problem UI was a major ordeal. User Interfaces are hard to get right… Hopefully Barnes & Noble will keep working to improve it over time.
While these Tablets have very different price points, features, and screen sizes, it is still useful to compare the quality and performance of their displays because the display enhances or degrades the appearance of everything that runs on the Tablet.
There is no absolute winner for this Display Shoot-Out because all 3 Tablets were both winners and losers in some categories, which is interesting in and of itself. In most categories the 3 displays were reasonably close in their lab test performance, which again is interesting, but perhaps not that surprising since they are all IPS LCDs. But the Nook Tablet was the leader in more categories – both in the lab tests and the viewing tests – so it is the declared winner in overall display performance and picture quality, at least for this round…
The iPad 2 also has an excellent display and is very close in performance to the winner. What is impressive is that the iPad 2 is still delivering top display performance close to what many predict is the end of its product cycle, with lots of interesting predictions for its next generation.
The Amazon Kindle Fire came in with a decidedly last place finish behind the Nook Tablet and iPad 2. In most categories it was just somewhat behind the Nook Tablet and iPad 2, but as the Highlights section above explained the Kindle Fire has 2 major flaws. These two significant points aside, it's otherwise a good Tablet display. The Gallery viewer delivers only 16-bit color and has a significantly distorted gray-scale, which could be fixed with a future software update if Amazon chooses to do so. However, its high screen reflectance cannot be fixed. Note that some after-market screen protectors that claim to reduce glare actually increase the overall reflectance but fuzz it out with a matte finish – so they are not recommended as a fix. The best solution is just to carefully orient yourself so that there aren't any bright sources of light behind you that can reflect off the screen and degrade or obscure the image. In fact, a lot more can be done to reduce screen reflections, so I consider all of the Tablets unsatisfactory in this regard, although the Nook Tablet has the lowest reflectance for now.
For a full comparison of each tablet's screen, expand the chart below
This article has been republished with permission from DisplayMate.com, where it can be read in its entirety.
About the Author
Dr. Raymond Soneira is President of DisplayMate Technologies Corporation of Amherst, New Hampshire, which produces video calibration, evaluation, and diagnostic products for consumers, technicians, and manufacturers. See www.displaymate.com. He is a research scientist with a career that spans physics, computer science, and television system design. Dr. Soneira obtained his Ph.D. in Theoretical Physics from Princeton University, spent 5 years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another 5 years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested, and installed color television broadcast equipment for the CBS Television Network Engineering and Development Department. He has authored over 35 research articles in scientific journals in physics and computer science, including Scientific American. If you have any comments or questions about the article, you can contact him at firstname.lastname@example.org.
About DisplayMate Technologies
DisplayMate Technologies specializes in advanced mathematical display technology optimizations and precision analytical scientific display diagnostics and calibrations to deliver outstanding image and picture quality and accuracy – while increasing the effective visual Contrast Ratio of the display and producing a higher calibrated brightness than is achievable with traditional calibration methods. This also decreases display power requirements and increases the battery run time in mobile displays. This article is a lite version of our intensive scientific analysis of smartphone and mobile displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the deficiencies – including higher calibrated brightness, power efficiency, effective screen contrast, picture quality and color and gray scale accuracy under both bright and dim ambient light, and much more. Our advanced scientific optimizations can make lower cost panels look as good or better than more expensive higher performance displays. For more information on our technology see the Summary description of our Adaptive Variable Metric Display Optimizer AVDO. If you are a display or product manufacturer and want our expertise and technology to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.