Smartphone Displays - AMOLED vs LCD
Apart from the major supply issues, the commercial AMOLED screens at first seemed to have some drawbacks such as being too reflective, which diminished their sunlight visibility. Moreover, despite the lab claims for power efficiency, battery life on smartphones with AMOLED screens was nothing to get excited about at first.
Then, in January 2010, Samsung announced the next generation of “Super" AMOLED screens. Super AMOLED is 20% brighter, 80% less reflective, and uses 20% less energy than regular AMOLED screens, thanks to having only two major components – the actual AMOLED emitting layer, and the tough but thin Gorilla Glass, sealed over it. The touchscreen coating Samsung has managed to apply as an only 0.001mm thin layer in-between, bringing the light-emitting layer closer to the glass, to show raw, vivid colors.
On the other hand, the IPS-LCD (in-plane-switching LCD) technology, has largely overcome the usual troubles with LCD screens, namely power consumption and viewing angles, plus it allows for smaller pixels, making possible the incredible resolution of the iPhone 4. The iPad and iPhone displays are mainly produced by LG, and exhibit much more contrast, compared to regular LCDs. It is probably the best the LCD world can offer, without being cost-prohibitive.
Asked about why Apple didn’t go with the emerging OLED screen technology for the iPhone 4, Steve Jobs said that the high-res IPS-LCD in the iPhone 4 is better than OLED. And he was right - at the time when millions of iPhones had to be produced, the only OLED technology that might have met Apple’s requirements is Super AMOLED. Since it belongs to Samsung, it will not be until 2011 that the Koreans would be able to mass-produce such screens. Apple approached Samsung for their AMOLED screens, in the preparations to launch the iPhone 4, but the capacity just isn't there. There are rumors that Cupertino is talking again with Samsung regarding the Koreans' new plant capacity for an eventual Super AMOLED display in the upcoming iPhone edition next summer.
Still, the more mature LCD technology managed to come up with an IPS-LCD screen for the iPhone, which hits AMOLED in a few areas where it hurts. A major advantage of Apple’s IPS-LCD is the so-called Retina Display technology, which has miniaturized pixels in order to cram a 640x960 resolution into the 3.5” display. At this resolution, only perfect vision can distinguish the individual pixels from a certain distance. That makes high-contrast situations, such as e-books and web pages look very crisp and legible.
Also, with one of the major advantages of OLED-based displays being their slender profile, Apple still managed to produce the thinnest smartphone on the market, helped by LG's slim display. Despite LCD’s need for backlighting, the advancements in power management in the IPS-LCD brought along similar battery consumption on comparable chipsets for both phones. This is not easy to be explained, until we look at one table from the dawn of OLED-based screens a few years ago:
The fact of the matter is that LCD screens draw fairly constant power, no matter what images are shown on the screen. AMOLED, in its turn, needs the most powerful current applied to pixels that are showing white. Thus, while OLED displays are up to 90%+ more efficient when the background is black, when showing pure white, OLED screens can be consuming 3 times more power than an LCD display. This is why black menu backgrounds and colorful icons are recommended in user interfaces developed for AMOLED screens.
In a recent battery endurance test, consisting of websites display on several last-gen phones, it wasn’t the Super AMOLED phones that came ahead, but rather the Motorola DROID 2 and Motorola DROID X with their last-gen LCD screens. If the test had been on a looped video, the Super AMOLED phones would have probably given up the ghost last, since websites mainly use white backgrounds.
AMOLED screens also have shorter lifespan of the blue organic diodes, compared to the green and red ones, which might result in a shorter overall lifespan of the device. Using a PenTile matrix (developed by a company, whose IP Samsung bought not long ago), is one way to remedy this shortcoming. It arranges one green subpixel with double-width red or blue ones, thus showing only two colors per pixel, instead of the usual three. Some researchers claim this effectively lowers the interpolated 480x800 resolution of the Samsung Galaxy S, to actual 392x653, making text and web pages appear more pixelated. Recent advancements of the blue diodes' lifespan, however, puts it at over 30 000 hours, which means the screen will be around for many moons after you have moved on to another phone anyway.
Both handsets use Gorilla Glass, but the OLED-based screens are more withstanding to concussion due to less layers in them, and glass elements in general. On the other hand, OLED is easily damaged by water, that is why the Gorilla Glass is sealed over the touch coating of the AMOLED layer. Not that LCD would survive much water, but we are just nitpicking here, for comparison's sake.