All posts tagged Atrix

Motorola Battery Indicator- Really a Color Error?

While I do not have the time to respond to everything that is written about PenTile technology, occasionally I will see something that is not quite right which is then picked up by other blogs and gets a life of its own. This can happen from a single photograph. Perhaps you have seen one or more recent blogs that claim that PenTile cannot render color correctly and then go on to illustrate this using the same badly focused photo.

Here is one that appeared today from androidphonetech.com.

As indicated by the logo, this photo seems to have originated with XDA.CN.

Several bloggers have shown this photo of a Motorola smartphone display stating that this proves that PenTile RGBW displays in Motorola’s phones exhibit this type of color error. I would be the first to agree that photographing high resolution displays is very challenging, especially at such high magnification. It is easy to overexpose the image, as was done here. Overexposure can cause color shifts, because the elements in the camera’s CCD of the proper color will become saturated and can no longer respond. Only at the right hand edge, where there is less light due to blur, did the camera capture the correct color.

Battery indicator on Motorola Atrix

With the proper exposure, from the equivalent display in a Motorola Atrix, you can see above that the highly magnified battery icon is rendered with the correct color over the entire area. You will see that there are more red subpixels on the top of this, since it was the intention to shade the green toward yellow at the top. And, here is the same photo, but zoomed in to show just the battery indicator:This photo matches exactly with what I see with my own eyes when looking through an eye loop.

Some of you may say it is different in a Droid X2 or another Motorola phone, but it is the same technology and the same PenTile firmware.

Of course, it was never intended that viewers examine these displays at this magnification, so you will see pattern visibility in these photos that is not apparent to people with normal vision for normal use. Fully saturated green on PenTile RGBW will have a bit of a checkerboard look that can be seen at this magnification. This does not occur with less saturated colors.

Finally, I tried to reproduce the color error by overexposing my photo of this same display and was able to reproduce the effect below. Of course, this will be slightly different for different cameras with different camera CCDs.

Battery Indicator Overexposed - note the yellow center with the green edge.

As you can see for yourself, PenTile RGBW is rendering the colors in this battery icon correctly in Motorola phone displays.

Why Bother With a PenTile RGBW LCD if an RGB Stripe is Available?

People have written about the PenTile RGBW in the Motorola Atrix and have wondered why Motorola would choose PenTile if they could have used the conventional RGB stripe. In following some blogs it was interesting to see that some people understood the reason, but let me explain it again here.

The key value proposition for PenTile RGBW LCDs is to save power. And not just a small amount of power but a sizable amount of power. Using one industry standard for a usage model, JEITA, it is easy to show that PenTile RGBW can save about 40% of the power compared to the equivalent legacy RGB stripe LCD. That is nothing to sneeze about. Baseband processor developers have spent countless hours just trying to save 10 microwatts of power, but this saves  tens of milliwatts.

For a phone, a very significant consumer of power is used by the display and in particular the backlight in the display. The PenTile RGBW saves power in two ways. First, it has larger subpixels which means that a smaller percentage of light is blocked by the subpixel transistor and buss-bar and more is available to light up the panel. This is sort of like comparing a fine mesh window screen to a coarser mesh screen. More light gets through the coarser mesh screen.

Secondly, one-quarter of the subpixels are  white subpixels. By white, it means that these are clear, letting light from the white LED backlight  pass though almost unobstructed. R, G, and B subpixels each absorb all colors except for one. Light that is absorbed in color filters is turned into unwanted heat and is wasted. So much of almost all content is white or near white that this is worth writing home about.

This translates into either more brightness, or longer time between charging, or thinner and lighter phones. In a compute intensive phone like the dual-core Atrix saving power is important.

So, not only is a bunch of power saved, but the white subpixels allow you to have really brilliant whites. For images where light reflects off of water or metal it now displays a brilliance that is much more like real life than has been experienced with legacy RGB stripe displays.

Save some power with PenTile RGBW.

Is Sharpness the Same as Graininess?

I recently came across this FoneHome article comparing the Galaxy S 2 Super AMOLED Plus to the HTC Sensation qHD and noticed that there seems to be some confusion about graininess and sharpness.

It is possible to have a grainy appearance and still have a sharp display.  And if so, how?

When people talk about a grainy appearance they are really speaking of pattern visibility. The structure of the subpixels can be seen, especially if the display is larger diagonal and the format is low. That is why PenTile is not applied to very low dpi applications. Since PenTile has fewer dots, but the same number of pixels, it is easier to see the pattern than in an RGB stripe display of the same format and size. I have met some people who have exceptional vision, or the ability to view displays from very close range, who can see such graininess even in the iPhone 4 display, so this is a very individual thing.

For qHD displays like the Motorola Atrix, it far more difficult to see the pattern. There are, for example,  3.1-inch PenTile OLED displays where nobody has ever commented in any blog on any graininess or that these phones use PenTile technology.

So can a grainy display still be sharp? Yes, sharpness is measured and perceived as modulation ratio. When you write a black and white line pair can you still see the difference between the white and the black and you must be able to measure 50% contrast modulation or more. PenTile displays have no difficulty meeting and exceeding 50% contrast modulation ratio to the full resolution of the panel and in any direction. So a WVGA panel should be capable of 400 black and 400 white lines in one direction and 240 black and 240 white lines in other direction. This is possible because the algorithms for PenTile display analyze each image and apply adaptive filters to enhance edges of text and fine line graphics, thereby assuring sharpness.

In short, the answer is yes; a display that may look a bit grainy can still be sharp.
Hopefully that helps clear things up (no pun intended).