What PenTile screens mean for the Droid Bionic and other phones

There is more to the screen on a mobile device than the resolution, or even the panel technology it uses. The way the individual sub-pixels are arranged can drastically affect the appearance and performance of the device. Motorola has been using higher resolution screens this past year on devices like the Droid Bionic, but they come with a PenTile sub-pixel arrangement. Samsung has also been changing up its own sub-pixel design in recent months. There are benefits and drawbacks to the way a PenTile screen operates.

The classic arrangement of sub-pixels is probably familiar to most users as RGB. One red, green, and blue pixel can be combined to display nearly any color. As display technology marches on, some manufacturers have started altering that set up in order to reduce manufacturing costs and improve some aspects of performance.

The Droid Bionic, and other recent Motorola phones have been running qHD (960×540) LCD panels with an RGBW sub-pixel arrangement. These are essentially 2×2 blocks of sub-pixels that contain a red, green, blue, and white pixel element. Under the category of clear benefits is that having that additional white sub-pixel is better for display brightness at no additional power cost.

On a RGB screen, the individual pixel elements are lined up from top to bottom (a red is always below and above another red, for instance). This allows for the crisp lines and borders users expect based on screen resolution. With RGBW PenTile, matching sub-pixel elements are lined up diagonally, which gives the screen a strangely cross-hatched or “screen door” pattern under certain conditions. When viewed up close, the offset sub-pixel matrix makes lines look jagged, but at distances of more than about 18-inches, this effect is mostly undetectable.

The other common sub-pixel arrangement is RGBG, which is seen in Samsung’s Super AMOLED screens and possibly the just announced Super AMOLED HD. Since AMOLED screens do not have a backlight, there is no reason to have the additional white pixel as in the Motorola screens. In RG-BG, each green pixel shares a red and blue element with another green sub-pixel.

The human eye is most sensitive to green, so these screens, which end up with one-third fewer sub-pixels, retain the same perceived color intensity thanks to all the greens. The same cross-hatch pattern mentioned above is present with a RGBG matrix, but since the green elements are oriented in a vertical stripe, the effect is not as pronounced. Usually, very thin horizontal lines are the most affected by RGBG PenTile. Interestingly, this vertical green sub-pixel column is visible in some instances at the very edge of the screen.

A major reason for the continued use of PenTile is that in increases the yield of screen in the manufacturing process, and also results in thinner panels overrall. Despite this, Samsung has moved away from PenTile for most of its current generation phones, instead producing AMOLEDs with RGB pixels. The cost of manufacturing is higher, but there are none of the odd blurring effects up close.

A PenTile matrix does come with drawbacks in the close-up looks department, and we’ve found the “screen door” pattern to be more troublesome with RGBW PenTiles. Motorola has always been very invested in battery life on their devices, so it’s not a surprise that it would go with a more power efficient type of LCD even with these problems. The fact that Samsung seems bent on moving away from PenTile indicates that it isn’t an ideal solution, but sometimes it might be the best we have.