HD Super AMOLED versus Retina Display

When Raymond Soneira compares smartphone displays, he doesn't just stare at side-by-side screens, using his highly-trained eye to detect differences in color temperature and contrast. He does that, make no mistake, but he also uses a suite of scientific tests that measure factors like brightness, color gamut, and reflection. Soneira is the president, CEO, and founder of DisplayMate Technologies, a gold standard toolkit among manufacturers and display reviewers, CNET included. A PhD in theoretical physics, Dr. Soneira has spent 23 years fine-tuning the algorithms that analyze visual data on screens of all sizes, from smartphones to TVs. Mathematical models are a specialty of his; in past positions, Soneira has developed intricate tests for both AT&T Bell Labs and CBS (CNET's parent company,) among others. This mountain of experience and expertise is why I'm paying attention when Soneira tells me quite plainly over the phone, "Just about every single spec on displays is exaggerated." And by "exaggerated," he suggests skewed, misleading, and sometimes utterly useless. Why? Because while a screen's resolution and other specs can indicate a certain level of performance, there are many more factors involved in determining a display's actual level of performance. That's because what makes a smartphone screen great is a combination of factors like the physical screen materials, screen technologies (LCD versus OLED), pixel layouts (RGB variations), brightness, color accuracy, contrast ratio, reflectance, screen size, and pixel resolution. Got all that? Good, now let's dive in. The anatomy of a smartphone screen Your smartphone screen is comprised of several layers of material, starting from the bottom with the display's backing material. This "substrate" could range from the thin, pliable plastics of concept phones with flexible screens, to the tougher stuff of today's handsets. On top of the substrate is the lighting element (like the backlight for LCD screens), which is then topped with a TFT (thin-film transistor) layer, which uses voltage-sipping transistors to keep the display's pixels shining until you refresh or change the image. There's also the touch-sensitive panel; various films and filters that might reduce glare, for instance; and the cover glass, which might lay on top as a separate layer, or could be bonded to the touch layer. Gorilla Glass is one designer brand of cover glass. Why am I telling you this? Because the physical components can affect the screen's ultimate visual quality. For instance, screens with bonded cover glass remove trapped air you would otherwise have between the cover glass and lower layers. Removing that air can generally improve reading legibility by cutting down on some of the reflection you get when light pouring out from the screen bounces back to the display. Lower-quality materials can also narrow the device's viewing angle and diminish the color, both of which make for a degraded experience overall. LCD versus OLED There are warring schools of thought surrounding which type of display technology is better: LCDs (which act as valves to allow varying amounts of the backlight through to the viewer) or AMOLED/OLEDs (a different approach that uses "active-matrix organic light-emitting diodes" to directly emit light.) There are complex ins and outs, but in a nutshell, you can think about LCDs and OLEDs as follows. LCD screens start with an always-on backlight; this technology requires light to create black, white, and colors. In general, high-end LCDs are known for producing the most accurate colors and grays, though their manufacturers sometimes intentionally calibrate LCDs to produce weaker red, blue, and purple shades in order to reduce the device's power consumption. LCDs generally age slower, Soneira says, with the brightness and color balance holding up fairly well over thousands of hours of use. OLED on the other hand, doesn't require any light to produce black, just white and colors. Therefore, it's considered battery-saving (since it requires no energy to create black) and can produce inky blacks. OLEDs are often considered brighter as well, creating punchy hues. As a side effect, OLED screens tend to oversaturate green. A more pressing problem, OLEDs also age more rapidly than LCDs, according to Soneira and other experts, which means that the red and blue colors deteriorate faster than green, which can further throw the color balance out of whack. OLEDs can also be expensive to make, at least at its current stage of development, and in the past, limited production has caused some manufacturers, like HTC, to switch from AMOLED to LCD smartphone screens. What makes the two differing technologies more confusing is that there are multiple flavors of each. For instance, IPS (in-plane switching,) is a type of premium LCD technology that's touted for its wide viewing angle and clearer picture. LG uses IPS in the LG Optimus LTE, and Apple also lists it in the iPhone 4/4S and iPad specs (although Soneira mentions in one shootout that it's really a related technology called Fringe Field Switching, or FFS). Soneira says that the cheaper versions of LCD technology found in the Motorola Xoom and Acer Iconia A500 tablets can account for their poor color saturation, narrow viewing angles, and increased reflection, the latter that impeded a clear view of the stuff on the screen. So what about Super AMOLED? The most common OLED smartphone screens also come with the prefix "Super." Don't let that throw you. Super AMOLED is simply Samsung's proprietary name and approach to making OLED smartphone displays. Unfortunately, Samsung politely declined to participate in this story; so I can't share with you Samsung's in-house take on technical variances between their brand of AMOLED screens compared to others. What I can elucidate is the main difference among the three Samsung AMOLED types: Super AMOLED, Super AMOLED Plus, and HD Super AMOLED -- and that difference comes down to sub-pixels. Each screen pixel is actually comprised of red, green, and blue sub-pixels that can turn on and off in combination to create any supported color combination (turn them all on at full blast to shine white.) There are numerous ways to pattern the sub-pixels. Super AMOLED uses Samsung's PenTile layout, and its pattern of red, green, blue, green (RG-BG) sub-pixels. PenTile, in fact, uses fewer red and blue sub-pixels as it does green. As such, PenTile also has fewer sub-pixels than the typical RGB layout found in LCDs and in other AMOLED screens, like the Nokia Lumia 900. Examine a PenTile screen closely and you might be able to detect a little more image granularity when you're looking at fine details and text. For the most part, though, your eyes fill in the blanks. It was with great fanfare that Samsung trotted out its Super AMOLED Plus displays in early 2011, extolling the virtues of "50 percent more sub-pixels" on a total display. That's 12 sub-pixels per pixel rather than 8, Samsung says. This might be a good time to address the fact that PenTile has multiple combinations and permutations that help reduce pixelation artifacts. So while you could count an 8 sub-pixel pattern (with four pixels in different sub-pixel combinations,) Soneira maintains that there are still only two sub-pixels per pixel either red-green or blue-green. However you dice it, the increase led to crisper, smoother, brighter images since the larger sub-pixels also let in more light. The sub-pixel arrangement, which was simply an RGB pattern, is found on the Samsung Galaxy S II, Samsung Droid Charge, and Samsung Infuse 4G. Another by-product of Super AMOLED Plus' larger pixels is the need for a larger total screen size in order to achieve the same pixel count, like an 800x480-pixel resolution. As for HD Super AMOLED, if you guessed it's a regular PenTile Super AMOLED display, but with a 1280x720 pixel resolution, you'd guess right. You can find HD Super AMOLED on phones like the Samsung Galaxy Nexus, the Samsung Galaxy Note, and the Samsung Galaxy S III. So why stop now? With HD Super AMOLED, Samsung seems to have backed away from Super AMOLED Plus, with its RGB layout, and returned to Super AMOLED and its PenTile sub-pixel array -- a move that's disappointing some followers. Plenty of CNET readers and other smartphone enthusiasts have complained that Samsung isn't putting its best technology forward, reverting from the "Plus" screen in the Galaxy S II to the regular PenTile screen in Sammy's next flagship phone, the Galaxy S III. Although Samsung didn't comment for this piece, an employee of Samsung America (but not Samsung Display,) has said elsewhere that Samsung selected PenTile for its durability. From cnet