frontline technology Tablet Display Technology Shoot-Out Smartphones and tablets represent a new class of displays with requirements different from that of TVs and monitors. Here is where manufacturers are – and are not – meeting the challenges of ambient light and other considerations. by Raymond M. Soneira MARTPHONES AND TABLETS In addition to being mobile computers that Tablet Displays and Display Technologies Srepresent a major product revolution for con- produce high-resolution text and graphics, The line between smartphones and tablets has sumers, but these mobile devices have had an these devices are also mobile HDTVs and become increasingly blurred, which has given even greater impact on the display industry. photo viewers. They are expected to deliver rise to an intermediate category called Up until recently, most display technology excellent picture quality and color accuracy phablets. For this article, I am classifying any was dedicated to producing large AC-powered over a wide range of ambient lighting. Their mobile display with a 5.5 in. or greater screen TVs and computer monitors that are used onboard digital cameras and their frequent use diagonal as a tablet. I picked a representative almost exclusively indoors under controlled for photo sharing among family and friends set of high-end displays and display technolo- and often subdued ambient lighting. Laptops make picture quality and color accuracy much gies in this size class, with the additional are the original mobile displays, but they have more important than for HDTVs because the requirement that they had to be tested on a hefty batteries, often run on AC power, and viewers often know what the photo subject production class device (rather than as a are also typically used indoors under con- matter actually looks like, especially when the standalone display or prototype). Four tablet trolled and subdued ambient lighting. photos are viewed on a large tablet screen displays were tested and analyzed in-depth, Enter smartphones and their bigger cousins, moments after being taken. plus many others are mentioned where appro- the tablets, as the first truly mobile displays. Last, but definitely not least, the displays priate. Here they are: They are essentially handheld screens operat- are used at relatively close viewing distances, ing primarily on battery power that are typically less than 15 in. Given their small OLED Displays and Technology designed for the convenient viewing of con- screen sizes and high pixel resolutions, they While most mobile displays are still LCD tent and images virtually anywhere. More require very high pixel densities, starting from based, OLEDs have been capturing a rapidly importantly, they are often used under rela- around 125 up to the latest 450+ pixels per increasing share of the mobile-display market. tively high ambient lighting and with screens inch (ppi) displays. Compare this to a 50-in. The technology is still very new, with the that are typically oriented anywhere from 45° 1920 × 1080 HDTV, which has just 44 ppi. In Google Nexus One smartphone, launched in to entirely horizontal (as when resting on a terms of the more physically relevant area January 2010, as the first OLED display prod- table). These angles typically catch and density, pixels per square inch, that is up by a uct that received widespread notoriety. In a reflect substantially more light than the verti- factor of 100:1 – very impressive! span of just a few years, this new display tech- cally oriented screens of TVs, monitors, and The above represents an incredibly tough nology has improved at a very impressive laptops. Because they are carried around and comprehensive set of requirements for rate, now challenging the performance of the everywhere, these devices are also much more any display to deliver. While much has been best LCDs. Virtually all of the OLED displays vulnerable to breakage, so they almost always accomplished in just a few years, there is still used in current mobile devices are being pro- come with a hefty cover glass, which further much more that needs to be done. In this arti- duced by Samsung Display. Here, I test the complicates reflections from ambient lighting. cle, I will use an extensive set of lab tests and Samsung Galaxy Note II, a 5.5-in. 1280 × 720 measurements on a number of cutting-edge RGB OLED tablet, which is the largest OLED Raymond M. Soneira is the founder and displays and display technologies to see how tablet display currently available. Samsung President of DisplayMate Technologies they are meeting these challenges. I will also had previously offered a Galaxy Tab 7.7-in. Corporation. He can be reached on the suggest areas and paths for improvement in RGB OLED tablet – so larger screens are www.displaymate.com website. future mobile displays. likely again in the near future. On the high- 12 Information Display 4/13 0362-0972/4/2013-012$1.00 + .00 © SID 2013 resolution side, the recently released Galaxy 1280 × 800 displays in 2012. After dismiss- been E Ink, including its 6–10-in. Pearl mono- S4 smartphone has a 1920 × 1080 5-in. ing the smaller 7-in. tablets, Apple subse- chrome and Triton color displays. Here, I will 441-ppi PenTile OLED display, which will quently introduced its own iPad mini, with a test E Ink’s 8-in. 800 × 600 Triton II color undoubtedly be extrapolated into the next 7.9-in. 1024 × 768 display with a (surpris- tablet in the High Ambient Light section generation of OLED tablets. ingly) lower performance and a much smaller below. color gamut and higher reflectance than both LCDs and Technology the Nexus 7 and Kindle Fire. The Google Display Properties and Display LCDs encompass a very broad range of Nexus 7 was tested as a representative of the Marketing display technologies. While some tablets 7-in. tablets. The tablets are compared in Table 1, which have launched with lower-performance 10-in. High-Resolution LCDs: Apple lists their product specifications and display twisted-nematic (TN) LCDs, most successful started the tablet revolution in 2010 with the properties. While this article provides objec- tablets now use higher-performance LCDs, iPad, a 9.7-in. 1024 × 768 132-ppi display. It tive technical data and analysis of the dis- often with in plane switching (IPS), fringe had a high-quality IPS/FFS display. Follow- plays, it is important to understand that all of field switching (FFS), or plane-to-line switch- ing the revolutionary iPhone 4’s 326-ppi these products are configured by marketing ing (PLS). Retina Display, Apple introduced a third- requirements designed to get the attention of 400+ ppi LCDs: Apple started a major generation iPad in 2012 with a 2048 × 1536 consumers by appealing to their interests, revolution in display marketing by introducing 264-ppi Retina Display. There have been lots preferences, and biases, and in some cases to its “Retina Display” in 2010, having 326 ppi of competing 10-in. tablets, first typically with their lack of technical knowledge. on the iPhone 4. While the display is not 1280 × 800 displays and then later with 1920 actually equivalent to the resolution of the × 1080 and above displays. The Google Color Gamut human retina, people with 20/20 vision cannot Nexus 10 is the iPad’s current closest display The color gamut is the range of colors that a resolve the individual pixels when the Retina competitor with a 10.1-in. 2560 × 1600 display can produce. In some cases, color Display is held at normal viewing distances of IPS/FFS display. For the large 10-in. high- management is used to adjust the display’s 10.5 in. or more. The introduction of the resolution tablets, I will test the Apple Retina native color gamut in order to better match an Retina Display made it clear that displays Display iPad. industry-standard gamut. I am bewildered were no longer commodities but rather an that the display industry is still widely using important sales and marketing feature for Reflective Displays and Technology as a reference the NTSC color gamut, which mobile devices. The iPhone 4 also started a A number of reflective tablet display tech- was defined in 1953 and has been obsolete for ppi and megapixel war similar to what hap- nologies have been under long-term develop- over 30 years. This confusion spills over pened with smartphone digital cameras, which ment, including E Ink’s electrophoretic from display manufacturers, to device manu- are still experiencing an ongoing wild goose displays, Qualcomm’s mirasol, Amazon’s facturers, to journalists and consumers, who chase heading into the stratosphere. Hope- Liquavista, and Pixel Qi. The only one to frequently quote and evaluate the color gamut fully, the same sort of competition will not reach a significant production stage so far has in terms of the totally irrelevant NTSC gamut. occur with mobile displays. The real question is how high do we need to go before reaching a practical visual ppi Table 1: Four tablets representing different display technologies are limit? That is a topic that I will analyze in compared in terms of their product specifications and display properties. detail in a future article. However, a new gen- eration of 400+ ppi displays is already here, Samsung LG Optimus Google Apple iPad driven by the desire of many manufacturers to Categories Galaxy Note II G Pro Nexus 7 Retina Display produce a full-HD 1920 × 1080 display in a Display Technology OLED LCD LCD LCD IPS/ phablet screen size. In 2012, HTC introduced RGB Stripe IPS LTPS FFS aSi FFS aSi its Butterfly/Droid DNA smartphone with a 1920 × 1080 5.0-in. 440-ppi display manufac- Display Manufacturer Samsung LG Hydis Multiple tured by Sharp that uses continuous grain sili- Display Display con (CGS) rather than amorphous silicon Screen Diagonal (in.) 5.5 5.5 7.0 9.7 (a-Si), which becomes increasingly inefficient at high pixel densities.