Something early iPhone X reviewers have noticed but Apple only briefly mentioned during the September event: iPhone X uses a different pixel layout from all iPhone models before it.
Apple sources its OLED panels for iPhone X from Samsung.
However, Samsung manufactures them based on Apple’s design and exacting requirements, they’re not off-the-shelf parts. Whereas LCD-outfitted iPhones traditionally use the RGB stripe pixel arrangement, iPhone X’s OLED display uses a diamond pixel arrangement.
Also known as PenTile, this has larger, oval green pixels with smaller red and blue pixels wedged in between them, according to iMore’s Rene Ritchie. PenTile matrices are widely used in Samsung’s AMOLED displays—in fact, “PenTile” is a trademark of Samsung.
“It’s a way to mitigate against the significantly lower lifespan of blue pixels in OLED, and it’s what can currently be supplied at scale,” he wrote. PenTile tech uses sub-pixels that don’t actually belong to a grid of well-defined pixels, meaning any sub-pixel can be part of any pixel.
Specifically, each unit cell is comprised of two red sub-pixels, two green sub-pixels and one central blue subpixel. Subpixel layouts are specifically designed to work with proprietary algorithms for subpixel rendering embedded in the display driver.
Yes, Apple is using subpixel anti-aliasing to make the PenTile layout look as good as possible.
iPhone 8 Plus’s RGB stripe pixel layout (left) and iPhone X’s diamond PenTile pixels (right).
Subpixel antialiasing takes into account the OLED panel’s physical properties and takes advantage of the sub-pixels to anti-alias text and other content with greater detail.
It should be noted that antialiasing is inherent to PenTile technology, it has nothing to do with Apple. It’s also used on LCDs: macOS’s Quartz 2D has used antialiasing for years in order to make the text, line art and other vector graphic appear smoother.
The OLED panel on iPhone X is also Apple’s first smartphone display that supports HDR video natively. Some reviewers noted that some amount of blue shifts in off-axis viewing.
While the drop in saturation and shift to blue affects all OLED screens, Apple told TechCrunch’s Matthew Panzarino that it’s done work to counter this effect.
“I can tell you that, compared to other OLED screens, you have to get further ‘off of center’ to see a real shift in color, holding the phone 30 degrees or more off of dead on,” Matthew wrote.
For example, Apple individually calibrates every iPhone X before it leaves the factory.
Moreover, the iPhone X display is TrueTone-compatible and iOS automatically applies system-level color management to everything shown on the screen.
“On some phones, OLEDs go super blue. On iPhone X, it’s more of a slight blue shift with a reduction in saturation and dynamic range. It’s not terrible, but it definitely exists,” he added.
Despite these woes, the vast majority of reviewers called the bright, vivid power-saving OLED display on iPhone X a pleasure to look at, especially in direct sunlight.