Tablets are essentially large portable displays — handheld screens designed for conveniently viewing content and images anywhere you want while untethered. 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 — particularly for Android based devices that have nearly identical OS. On the flip side, 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.
When these five tablets are viewed together side by side, the differences in their displays are blatantly obvious. This is especially true for the Android tablets, because they all have identical 10.1-inch 1280×800 screens running virtually identical software. How could there be such a large disparity in a highly competitive market? The price points are all reasonably similar, so that is not the primary factor. One major issue is the manufacturers are all scrambling to get their products to market so there isn’t enough time to properly engineer everything. But the biggest factor is undoubtedly the explosive growth in the demand and volume of mobile displays, so many existing and new factories don’t have the time and/or expertise to properly manufacture and calibrate all the displays they are producing.
First: All of these tablets have large shiny mirror-like screens that are good enough to use for personal grooming. Think of it as one less thing you need to carry — seriously, it’s actually a very bad feature that requires higher screen brightness and more battery power to offset the reflected light, and it also causes eye strain. The larger tablet screen size makes it harder to position both yourself and the screen to avoid bright reflections.
Second: All of these tablets have a reduced colour Gamut that produces images with less saturated colours. It’s an intentional tradeoff made to increase screen brightness, power efficiency and battery run time.
Third: All of these tablets have a sharp decrease in Brightness and Contrast with Viewing Angle. This is a significant issue only when multiple viewers are watching a tablet but may also require a single viewer to carefully adjust the tablet orientation.
Fourth:All of these tablets have an unsatisfactory Ambient Light Sensor and Automatic Brightness Control, which wastes battery power and causes eye strain — see the Recommendations below.
Fifth: All of the current 1280×800 Android 3.1 tablets have only 1280×752 available pixels because 48 pixels are reserved for the system bar with the navigation buttons.
Sixth: Android 3.1 continues with a substandard Gallery viewer for photos and images that provides 16-bit colour processed up to 24-bits with poorly implemented dithering. It’s about time that gets fixed. Samsung, to its credit, has fixed this on the Galaxy Tab.
Finally: There was not a single bad pixel on any of the tested units — congratulations to all! But most of the manufacturer warranties state that bad pixels are entirely normal and not a defect, which is not right. Asus is the only manufacturer to offer enclosed documentation with a precise pixel defect policy, but it requires two adjacent bad pixels, or up to a total of eight bad pixels for replacement, which most consumers would find highly objectionable.
Most people (and reviewers) seem to believe that the 10.1-inch screens (measured diagonally) on the Android tablets are larger than the 9.7-inch iPad screen — but they are actually 5 per cent smaller than the iPad in terms of the image area of the screen, which is what really counts. This is due to both Aspect Ratio geometry (the screen area decreases as the Aspect Ratio increases) and the Android system bar, which reduces the image area.
The shape of the screens are also significantly different: the iPad has an Aspect Ratio of 4:3 = 1.33 (the ratio of width to height) and the Android Tablets all have an Aspect Ratio of 16:10 = 1.60. But because of the Android system bar the Aspect Ratio of the image area is larger, 1.70, which is rather close to the HDTV 16:9 Aspect Ratio of 1.78. So Android Tablets are very well suited for watching widescreen video in Landscape mode. However, they are generally considered too narrow to be very useful in Portrait mode. On the other hand, the iPad does not have a widescreen, but instead an Aspect Ratio very close to standard 8.5 x 11 inch paper, so it is naturally very good for reading lots of content in Portrait mode. In many cases it is also better for reading content in Landscape mode because the iPad’s image height is 5.8 inches while the Android Tablets have an image height of only five inches, so you can see more on the iPad before needing to scroll. On the other hand, for watching 16:9 widescreen videos, the iPad image height is only 4.4 inches, which is smaller than the Android height of 4.8 inches for 16:9 widescreen videos. So the best screen shape depends on your intended mix of applications.
For details and in-depth analysis see the Comparison Table below.
Apple iPad 2 Highlights
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 colours and very good Viewing Angle performance with small colour shifts but a large decrease in Brightness, which is the case even for the best LCDs. A major shortcoming is a reduced colour Gamut, but the iPad 2 improves on-screen image colour saturation by steepening its intensity scale — a simple trick that is also used by the Galaxy Tab, but the other displays fail to implement this (and the Motorola Xoom does the reverse).
Asus Transformer Highlights
The Asus Transformer also has an IPS LCD like the iPad 2. It’s not as bright or as well calibrated as the iPad 2 but it still delivers very good performance including very good contrast, reasonably accurate colours and very good Viewing Angle performance like the iPad 2. But the Transformer screen reflects 66 per cent more ambient light than the iPad 2. It has an 18-bit colour display, but produces 24-bit colour by using dithering (except in the Android Gallery viewer where there is 16-bit colour with dithering as discussed above).
Motorola Xoom Highlights
The display on the Motorola Xoom is a lower performance LCD than on the other tablets, compounded by poor factory calibration. Colours and colour saturation were much worse than the other displays, and the variation with Viewing Angle is awful. The Xoom screen reflects 49 per cent more ambient light reflectance than the iPad 2. The Xoom also has a Dynamic Backlight that varies the screen brightness in a peculiar fashion — it slowly dims the screen based on the Average Picture Level down to about 60 per cent and then just stops. It makes dim images dimmer — it’s counterproductive and just strange display behaviour. All of the other tablet displays have standard backlights, which don’t vary the brightness with picture content (the Galaxy Tab makes it an option).
Acer Iconia Highlights
The Acer Iconia A500 also has a lower performance LCD like the Motorola Xoom, but it’s better in a few decisive categories and is much better calibrated. Of particular noteworthiness, it was the definitive leader in Contrast Ratio, with more than double that of any other tested Tablet because of its very dark black. We triple checked this with some special DisplayMate test pattern measurements to make sure that it wasn’t due to a Dynamic Backlight. But it really has a true very dark black, which is quite noticeable in a dark room. Unfortunately the black brightness increases rapidly with Viewing Angle. The Iconia also had a nicely calibrated intensity scale, but it would actually have been better off with a steeper intensity scale in order to increase colour saturation in the same fashion as the iPad 2 and Galaxy Tab.
Samsung Galaxy Tab 10.1 Highlights
The Galaxy Tab display has a PLS (Plane to Line Switching) LCD, which is Samsung’s version of IPS, and it performs comparably to IPS — sometimes a bit better and sometimes not. It’s an impressive mobile display with a lot better standout performance than all of the other Android Tablets — except in one very important category. If you like to watch your HDTV with the colour Saturation control set to maximum then you will be right at home with the Galaxy Tab because Samsung has turned the colour obnoxiously high with no way to lower it (see below). It’s tolerable for images that don’t have much colour to begin with, but it hurts to look at images that have strong colour content. Moderation rather than the sledge hammer approach to colour would have resulted in an outstanding display. This could be fixed easily with a software update by adding a colour picture control that lets users adjust the colour to their liking — see our Third to Fifth Recommendations below.
And the Winner Is:
While the iPad 2 display easily outperformed all of the previous Android tablets, with the new Galaxy Tab 10.1, Samsung has delivered the first Android Tablet with an impressive, potentially outstanding display, but then ruined it by turning up the colour level to obnoxious levels — apparently in an effort to overcompensate and blatantly standout from the other mobile LCD displays that have subdued colour. But in the case of colour, too little is a lot better than too much. As a result the iPad 2 still delivers the best colour picture quality and accuracy of all of the tablets, even though its colours are somewhat subdued. As things stand, based on all of the display tests, the iPad 2 and Galaxy Tab 10.1 are reasonably close in performance in most categories, so it’s almost a tie, but the Galaxy Tab is ahead more often than the iPad 2, so the Galaxy Tab is the Winner, by a nose. But should Samsung or Android add a colour picture control to the Galaxy Tab with a software update as we describe below, then the Galaxy Tab would be the decisive Winner, by a lot. Of course, Apple could do the same. What is also 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 the Next Generation, which we discuss and analyse below.
Coming in a solid third place is the Asus Transformer, which delivers very good display performance across the board, all the more impressive because it is less expensive than the iPad 2, Galaxy Tab and the Motorola Xoom. Next is the Acer Iconia A500, which has a display that is somewhat similar in performance to the last place Motorola Xoom, but is better in a few decisive categories and is much better calibrated. It’s a bit cheaper than the iPad 2 and Galaxy Tab, but more expensive than the Asus Transformer. And finally, the Motorola Xoom comes in last place — like the Acer Iconia it’s not a horrible display but definitely significantly below the display quality of the iPad 2, Galaxy Tab and Asus Transformer. This is all the more surprising because the Xoom is by far the most expensive Tablet, and Motorola previously included an outstanding display in the original Motorola Droid Smartphone, which still delivers the best picture quality of any mobile display we have ever tested — so they once knew how to deliver a great display. This time it seems they just settled for a cheap low-end poorly calibrated display. For details on all of the Tablets see the Comparison Table below.
This article has been republished with permission from DisplayMate.com.
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 PhD in Theoretical Physics from Princeton University, spent five years as a Long-Term Member of the world famous Institute for Advanced Study in Princeton, another five years as a Principal Investigator in the Computer Systems Research Laboratory at AT&T Bell Laboratories, and has also designed, tested, and installed colour 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 [email protected].
About DisplayMate Technologies
DisplayMate Technologies specialises in advanced mathematical display technology optimisations and precision analytical scientific display diagnostics and calibrations to deliver outstanding image and picture quality and accuracy â€“ 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 colour and grey scale accuracy under both bright and dim ambient light, and much more. Our advanced scientific optimisations 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.