The Best Tablet Display: Guess Who?

Dr. Raymond Soneira of DisplayMate Technologies separates the best smartphone, tablet, HDTV, and multimedia displays from the worst with his Display Technology Shoot-Out series. So there's no one more qualified to tell you if that new iPad retina lives up to the hype:

Introduction

The iPad has been a phenomenal runaway success – to a degree that may have even surprised Steve Jobs. At the new iPad launch Tim Cook remarked that people have been wondering who would improve upon the iPad. Amazingly, but to no one's surprise, that would be Apple (again). Much to my delight the display is its flagship and number one marketing feature. Tablets, after all, are essentially large portable displays so a top notch display is the key to a successful product – something most manufacturers haven't figured out yet. Apple has from day 1 – and the new iPad display is impressive – Apple calls it "Resolutionary." This article will be a combination of objective praise and critical analysis of the Retina Display on the new iPad.

First of all, the Apple Retina Display is pure marketing brilliance. While the enhanced screen resolution is getting most of the attention, the enhanced color saturation is equally responsible for its wow factor. These are the two wonders of the new iPad. Both are technically challenging because they require lots of additional battery power. In fact, the battery on the new iPad has 70 percent higher capacity than the iPad 2.

While the enhanced resolution is important, it's also a technical overkill that parallels the Mega Pixel wars of digital cameras. More pixels are better up to a point, and then they wind up adversely affecting both performance and manufacturing costs. To a certain extent that is definitely the case for the new iPad as we explain below. Still Apple has managed to pull everything together nicely so that in the end it all performs quite well. Just as surprising is that Apple has managed to keep the retail price the same as the iPad 2. That's the third wonder of the new iPad. We will show and tell you below a lot more than you'll learn anywhere else about the iPad Retina Display…

A True "Retina Display" But Not an Actual Retina Display

The original Retina Display on the iPhone 4 has 326 pixels per inch (ppi). But to qualify as an Apple Retina Display the new iPad does not require the same ppi as the iPhone 4 Retina Display because it is typically held further away from the eye, whose visual sharpness is based on angular resolution rather than the linear ppi resolution on the display. The iPad is typically held 15-18 inches away as opposed to the iPhone 4's 12-15 inches. As a result, to meet the 300 ppi Retina Display specification made by Steve Jobs at WWDC for the iPhone 4, an iPad Retina Display only needs 240 ppi – and it has 264 ppi. So according to Apple's own definition, the new iPad is indeed a true "Retina Display."

However, Apple's definition of a "Retina Display" is actually for 20/20 Vision (defined as 1 arc-minute visual acuity). 20/20 Vision is just the legal definition of "Normal Vision," which is at the lower end of true normal vision. There are in fact lots of people with much better than 20/20 Vision, and for almost everyone visual acuity is actually limited by blurring due to imperfections of the lens in the eye. The best human vision is about 20/10 Vision, twice as good as 20/20 Vision, and that is what corresponds to the true acuity of the Retina. So to be an actual "True Retina Display" a screen needs at least 573 ppi at 12 inches viewing distance or 458 ppi at 15 inches. The 326 ppi iPhone 4 is a 20/20 Vision display if it is viewed from 10.5 inches or more. Unfortunately, a "20/20 Vision Display" doesn't sound anywhere near as enticing as a "Retina Display" so marketing and science don't see eye-to-eye on this…

Do You Really Need All of That Resolution and Sharpness?

I am definitely not proposing a new display Mega Pixel war for 400+ ppi (but several manufacturers are working on it, so we'll see). The new iPad display is incredibly sharp with 264 ppi and 3.1 million pixels on a 9.7 inch screen. The iPad 2 screen with 132 ppi, a resolution of 1024x768 and 0.8 million pixels is noticeably pixelated, but was it really necessary to double the resolution and therefore quadruple the number of pixels? Marketing considerations aside, the real reason for doubling the iPad's resolution to 2048x1536 is for the convenience and ease in up-scaling the older 1024x768 Apps from the iPad 1 and iPad 2 – every older App pixel is simply replicated 2x2=4 times. Rescaling to lower resolutions like 1600x1200 would have required more complicated processing, but the high power A5X processor on the new iPad could have easily handled that.

Marketing considerations aside, do you really need all of that "Retina Display" resolution and sharpness? In many cases no, for these five reasons: 1. Most adults don't actually have true corrected 20/20 Vision even with glasses or contact lenses. 2. If you view the display further away than the recommended viewing distance your eye can no longer fully resolve the sharpness of the display, so that high resolution is wasted. <>3. Unlike computer graphics images, photographic images (including videos) are inherently fuzzy, with the sharpest image detail spread over multiple pixels. Similarly, you would be hard pressed to visually tell the difference between 640x480 and 2048x1536 photographic images of a (Granny Smith) Apple. 4. Sub-pixel rendering, rather than ordinary pixel rendering, will significantly improve the visual sharpness of any display, especially for computer generated text and graphics, so that is the most efficient approach to improving sharpness. 5. Most people don't even have 1600x1200 resolution on the much larger 15-19 inch screens on their (Apple or Windows) laptops and desktop monitors and are happy with them (even the tech journalists that I asked).

The Best Tablet Display: Guess Who?

So where will the 2048x1536 3.1 Mega Pixel Retina Display actually make a noticeable visual improvement over other displays? All (computer generated) text will appear much sharper, but it will make the most difference whenever there is tiny text and fine graphics, which you often see when surfing the web (like the front page of The New York Times) or in a complex spreadsheet. Then there is a tremendous visual difference between the new iPad and the iPad 2 or existing Android Tablets. You won't have to zoom in as much or switch to Landscape mode as often when reading tiny web content. Full screen high quality photographs with lots of fine detail will also stand out and take full advantage of the new iPad's High Definition screen. The larger Tablet format also makes the iPad appear visually sharper and more stunning than the much smaller (and higher ppi) iPhone 4. One final note on Retina Displays: your existing HDTV is already a Retina Display. For example, a 1080p 46 inch TV viewed from 6 feet or more and a 1080p 60 inch TV viewed from 8 feet or more (the typical TV viewing distance in the US is 9 feet) are already 20/20 Vision "Retina Displays" so don't worry about upgrading them to get Retina Display resolution and sharpness…

IGZO and Other Apple Display Rumors Explained

A high resolution display for the iPad 2 and then the "iPad 3" was the number one rumor in the tech world for all of 2011. In fact, it resulted in hundreds (possibly thousands) of rumors for if, when, where, and how it would be done. Actually, the question was not whether it could be done, but rather whether it could be done with satisfactory yields, production volumes, and costs. While Apple was rumored to have invested in production facilities for Sharp, essentially all of the advanced display technology for Apple displays comes from its three principal display suppliers: LG, Samsung and Sharp. Chimei Innolux and Au Optronics also supply displays. In many cases new Apple products launch with just a single supplier (rumored this time to be Samsung for the new iPad) and then expand to between 3 and 5 suppliers for high volume products like the iPad and iPhone. New teardown reports now indicate that there are actually 3 display suppliers at launch: LG, Samsung, and possibly Sharp.

The iPad 2 uses amorphous Silicon for the LCD Active Matrix Thin Film Transistors (AM TFTs), the same display technology found in most Tablets, laptops, and desktop monitors. On the other hand, the iPhone 4 uses Low Temperature Poly Silicon (LTPS) because the much higher ppi requires smaller AM TFTs in order to maintain satisfactory brightness and efficiency. However, it's more complex and costly to produce. One of the biggest rumors was that Apple was going to use Sharp's IGZO (Indium Gallium Zinc Oxide), which is better at high ppi and lower cost than LTPS. But it's a new technology and Sharp publicly announced in December that it was experiencing startup delays. LG and Samsung have also been working on IGZO technology. The question is when, not if, this technology will be coming to future Retina Displays (and non-Apple Tablets and Smartphones). It will also be coming to laptops, monitors and televisions, possibly even Apple's. Our lab measurements show that IGZO is desperately needed for the new iPad high ppi display. And, counter to the rumor mill, IGZO can do IPS (in Plane Switching) technology that is found on the iPad 2 and iPhone 4 displays, see below.

So what display technology is in the new iPad? According to DisplaySearch it is still amorphous Silicon that has been pushed to its extreme upper ppi limit. Apple has a nice video on their website that discusses advanced dual plane LCD technology that they say is there to reduce sub-pixel crosstalk in the new iPad. It's actually technology originally developed by Sharp and other companies to increase the aperture ratio and brightness efficiency of these very high ppi LCDs. Another interesting display technology mystery: while Apple's official website Tech Specs and Features list IPS (In Plane Switching) as the LCD technology used in both the iPads and iPhone 4/4S (which provides wide viewing angles) the displays from all suppliers actually come with FFS (Fringe Field Switching) licensed from Hydis, which is related to IPS technology. This is also the case for many Android Tablets, including the Amazon Kindle Fire, Barnes & Noble Nook Tablet, and even the Samsung Galaxy Tab 10.1.

The Shoot-Out

To compare the performance of the new iPad we ran our in-depth series of Display Technology Shoot-Out tests on the new iPad. We take display quality very seriously and provide in-depth objective analysis side-by-side comparisons with the iPad 2 and iPhone 4 based on detailed laboratory measurements and extensive viewing tests with both test patterns and test images. We used the iPhone 4 rather than 4S because it performs slightly better. For comparisons with other "popular" Tablets see our 10 Inch Tablet Display Technology Shoot-Out and our IPS Tablet Display Technology Shoot-Out for comparisons with the Amazon Kindle Fire and Barnes & Noble Nook Tablet.

Results Highlights

In this Results section we provide Highlights of 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.

Comparison with the iPad 2 and Current Android Tablets: The display on the new iPad decisively beats (blows away) all of the Tablets we have previously tested including the iPad 2 (below), the Samsung Galaxy Tab 10.1, the Barnes & Noble Nook Tablet, and the Amazon Kindle Fire at the back of the pack. The articles also show that the iPad 2 display has recently slipped behind the Galaxy Tab and Nook Tablet. See the Conclusion section below for the evaluation and the article links for other tested Tablets.

Display Sharpness: As expected, all of the images, especially the text and graphics, were incredibly and impressively razor sharp. In some photographs, that extra sharpness made a significant difference, especially in close-ups and when fine detail like text was photographed.

The Best Tablet Display: Guess Who?

Improved Color Saturation and Color Accuracy: A major shortcoming of the iPad 2 and iPhone 4 is their reduced Color Gamut, they only have 61-64 percent of the sRGB-Rec.709 Standard Color Gamut needed for accurate color reproduction. That produces images with noticeably under saturated colors, particularly reds, blues and purples. This is due to efficiency issues from the Backlight LEDs. Apple claims "44 percent greater color saturation." Technically it's not clear what that means in this context, but the new iPad has a virtually perfect 99 percent of the Standard Color Gamut (a 38 percent improvement over the iPad 2). The colors are beautiful and accurate due to very good factory calibration – they are also "more vibrant" but not excessively so or gaudy like some existing OLED displays. See the Conclusion below for our overall assessment and the screen shots for a side-by-side screen comparison.

The Best Tablet Display: Guess Who?

Viewing Tests: What makes the new iPad really shine is its very accurate colors and picture quality. It's most likely better and more accurate than any display you own (unless it's a calibrated professional display). In fact with some minor calibration tweaks the new iPad would qualify as a studio reference monitor. See our detailed measurements.

The New iPad as a Camera: The main (rear) camera on the iPad 2 was awful but the camera on the new iPad appears to be the same as the camera on the iPhone 4, and it does take very good photos, but no where near as nice as a DSLR camera. Many reviewers have commented that it's awkward and dorky to hold up a Tablet to take a photo. But the real advantage of the new iPad over any other camera is that you immediately see your photo on a beautiful and color accurate 9.7 inch display. Even $2,000 DSLRs have only 3 inch low resolution screens, which are less than one tenth the area of the iPad screen, so you really don't know how good your photo is until you download it later on after the opportunity to take a better shot is gone (the same problem that film cameras had). Fortunately, DSLR cameras are beginning to offer WiFi.

The Best Tablet Display: Guess Who?

Screen Reflectance: The screens on almost all Tablets and Smartphones are mirrors good enough to use for personal grooming. Even in moderate ambient lighting the sharpness and colors can noticeably degrade from light reflected by the screen, especially objects like your face and any bright lighting behind you. Screen Reflectance on the new iPad is 7.7 percent, in the middle of the range that we have seen for Tablets and Smartphones. The best we have ever measured in our lab tests are the Samsung Galaxy S and the Nokia Lumia 900 with its ClearBlack display, with about half of the Reflectance of the new iPad, and the current worst is the Amazon Kindle Fire, with about double the Reflectance of the new iPad. This article shows how screen images degrade in bright ambient light.

Viewing Angle Performance: According to Apple the new iPad has an IPS LCD like the iPad 2 and iPhone 4, and our lab measurements confirmed excellent Viewing Angle performance, with no noticeable color shifts. However, all LCDs, including IPS LCDs, do have a strong decrease in brightness with Viewing Angle, and the new iPad performed as expected, with a 57 percent decrease in brightness at just 30 degrees Viewing Angle. The Viewing Angle performance for the new iPad, iPad 2 and iPhone 4 are all virtually identical.

Much Lower Display Power Efficiency: The new iPad uses 2.5 times the Backlight power of the iPad 2 for the same screen Brightness. As discussed above that results from the TFT transistors in the LCD blocking much more of the light at higher ppi. On the other hand, the highest ppi iPhone 4 is the most power efficient display of all because it uses Low Temperature Poly Silicon LTPS, which is much more efficient than amorphous silicon in the iPads. All of this points to the need for the IGZO display technology discussed above, which is more efficient and lower cost than LTPS. It should be in production shortly, and is the first in a whole series of enhanced Metal Oxide semiconductors for LCD and OLED displays.

Much More Power and Battery But Not Thickness or Weight: There are 4 times as many pixels in the display that need to be kept powered. Also 4 times as much memory and processing power is needed for the images. In addition, the light transmission of the LCD decreases as the pixel density increases, so a brighter Backlight is necessary. In fact, the number of Backlight LEDs has roughly doubled (from 36 to an estimated 72 to 82), so the Backlight power has approximately doubled. Since the display normally consumes about 50-60 percent of the total Tablet power, the new iPad needs at least a 50 percent larger battery. In fact, the battery increased from 25 to 42.5 watt hours, a 70 percent increase. Our measured Backlight power for the new iPad is 2.5 times the iPad 2 for the same screen brightness. In spite of the larger battery the running time at Maximum brightness in our tests was 5.8 hours, 20 percent less than the iPad 2's 7.2 hours. But at the Middle brightness slider setting, which is closer to typical user settings, the running time was 11.6 hours, which is almost identical to the iPad 2, indicating that Apple has used an appropriately larger battery (and confirms Apple's 10 hour claim). Surprisingly the overall iPad thickness increased by only 0.6mm (0.03 inches) and the weight increased by only 1.8 ounces (8 percent). That small increase in weight in spite of 70 percent more battery capacity indicates that the case and cover glass are significantly lighter.

New iPad Conclusion: Impressive… but Lots of Room for Improvement

Apple has taken the very good display on the iPad 2 and dramatically improved two of its major weak points: sharpness and color saturation – they are now state-of-the-art. Our lab tests and visual tests agree with Apple's claim that the new iPad has "the best display ever on a mobile device" so we have awarded the new iPad the Best Mobile Display Award in DisplayMate's Best Video Hardware Guide. But there's more…the new iPad's picture quality, color accuracy, and gray scale are not only much better than any other Tablet or Smartphone, it's also much better than most HDTVs, laptops, and monitors. In fact with some minor calibration tweaks the new iPad would qualify as a studio reference monitor. So we have also awarded the new iPad the Best Mobile Picture Quality Award, which was previously held by the original Motorola Droid (not the more recent Droids, which all have poor picture quality). Finally, almost as impressive is that Apple has maintained the base price of $499. Who says Apple doesn't compete aggressively on price!

Many New Professional Level Applications: With this degree of picture quality and accuracy the iPad is now qualified for many interesting professional level applications. If you are a professional (or serious amateur) photographer the new iPad will show your photographs more accurately than any other display you have (unless it's a calibrated professional display). More importantly, for medical imaging – every MD should have one for both mobile and office use. It will also be great for anyone that needs to refer to detailed documents and manuals – like field service technicians (millions of them), warehouse workers, and pilots just to name a few. Tens of millions of sales people often need a portable device that displays very sharp and accurate color representations of their products and sales information. For this the new iPad beats every laptop, Tablet, and mobile projector I have seen. It's impressive, but there is still…

Lots of Room for Improvement by Apple and Other Manufacturers

If you read our earlier Mobile Display Shoot-Outs for the iPhone 3GS, iPhone 4, and iPad 2, it certainly appears that Apple has been following our display advice (see Figure 3 on the evolution of the iPhone and iPad gray scale). So what's next… While Apple has zeroed in on sharpness and done an excellent job of it, and improved the color saturation and color accuracy to an impressive level, there are still plenty of other very important display issues that need to be addressed by all of the Tablet and Smartphone manufacturers, including Apple. Here are just a few: 1. Screen Reflectance: The typically large screen reflections can make the screen much harder to read even in moderate ambient light levels, requiring ever higher brightness settings that waste precious battery power. Manufacturers need to significantly reduce the mirror reflections with anti-reflection coatings and haze surface finishes. This article shows how Tablet and Smartphone screens degrade as the Ambient Light increases from 0 to 40,000 lux. 2. Ambient Light Sensor: The forward facing Ambient Light Sensor on virtually all Tablets and Smartphones measures the brightness of your face instead of the surrounding ambient light, which is what is needed to accurately set the screen's Automatic Brightness. 3. Automatic Brightness: The Automatic Brightness controls on all Tablets and Smartphones that we have measured are positively awful and close to functionally useless. As a result they often get turned off, which reduces battery run time and increases eye strain. This article explains how to do it properly. 4. Display User Interface: The User Interface for most Tablet and Smartphone displays consists of a Brightness slider and an Automatic Brightness checkbox. People have very different visual preferences that should be accommodated with a display Pizzazz control that is similar to the functionality provided by the audio Equalizers found on most Tablets and Smartphones. 5. RGB LED Backlights: Using separate red, green and blue Backlight LEDs instead of just white LEDs will allow more accurate calibration, allow the image color saturation to be increased under high ambient lighting, and also accommodate people that like extra vibrant rather than accurate colors on-screen. 6. OLED Displays: Once their cost significantly decreases and their power efficiency and production volumes significantly increase we'll start to see lots of Tablets with OLED displays. Until then, IPS LCDs can't be beat. 7. Size: 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 1024x768 iPad in 2012. I hope so… and so does my daughter, saying it will then fit in her handbag.

Display Shoot-Out Comparison Table

Below we compare the displays on the iPad 2, new iPad, and iPhone 4 based on objective measurement data and criteria. For additional background, context, and information see the Tablet Display Technology Shoot-Out article that compares the larger Motorola Xoom, Asus Transformer, Acer Iconia A500, and Samsung Galaxy Tab 10.1 Tablets with the Apple iPad 2, and the IPS Tablet Display Technology Shoot-Out that compares the Amazon Kindle Fire, Barnes & Noble Nook Tablet with the iPad 2.

The Best Tablet Display: Guess Who?

Click to embiggen chart. For further details, measurements, in-depth explanations and analysis see reference the links above at DisplayMate.

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 dtso.info@displaymate.com.

About DisplayMate Technologies
DisplayMate Technologies specializes in proprietary sophisticated scientific display calibration and mathematical display optimization to deliver unsurpassed objective performance, picture quality and accuracy for all types of displays including video and computer monitors, projectors, HDTVs, mobile displays such as smartphones and tablets, and all display technologies including LCD, OLED, 3D, LED, LCoS, Plasma, DLP and CRT. This article is a lite version of our intensive scientific analysis of Tablet and Smartphone mobile displays – before the benefits of our advanced mathematical DisplayMate Display Optimization Technology, which can correct or improve many of the display deficiencies. We offer DisplayMate display calibration software for consumers and advanced DisplayMate display diagnostic and calibration software for technicians and test labs.

For manufacturers we offer Consulting Services that include advanced Lab testing and evaluations, confidential Shoot-Outs with competing products, calibration and optimization for displays, cameras and their User Interface, plus on-site and factory visits. See our world renown Display Technology Shoot-Out public article series for an introduction and preview. DisplayMate's 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 to turn your display into a spectacular one to surpass your competition then Contact DisplayMate Technologies to learn more.