All posts tagged Misinformation

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.

PenTile Display looks Pinkish?

Not really. When PenTile OLED is used in applications that run in 5-6-5 color modes, it’s possible for whites at low levels of luminance to have a quantization error that has slightly more red than green. As shown in the chromaticity chart below, such a minor shift away from white toward red or magenta is easily seen by the human vision system.  With displays of very high contrast any shift toward red will be perceived as pink. The very same displays where viewers saw such “pinkishness” showed no such artifact in other applications that were running in 24-bit color mode.

Image credit: http://lightemittingdiodes.org

 

 

Interface to a PenTile RGBW Display

We noticed some PenTile related comments in the Russian publication at HABRAHABR.RU.  Since so many readers of that site went to our blog, I thought it would be appropriate to answer a question raised there ( shown below for those who can read Russian).

Это понятно: попасть в устройство от Джобса лестно каждому. Но этому дисплею такая честь вряд ли светит: во-первых iPad использует другое соотношение сторон, во-вторых пикселы PenTile сильно отличаются от нормальных. Чтобы работать с таким дисплеем, программа должна понимать, что экран состоит не из пикселов, а из полупикселов двух разных типов. В основном это решается на уровне драйвера, но многие приложения придётся адаптировать. В-третьих такое разрешение даст слишком большую нагрузку для мобильных процессоров, что выльется в лаги и повышенное энергопотребление.
Но успехи в увеличении разрешения дисплеев радуют.

If we understand this correctly, there is some concern about connecting an existing system to a PenTile RGBW display panel.  It was correctly understood at this site that we have, to date, put the electronics for driving PenTile into the driver chip, but it was not clear how the signal had to be prepared to drive this display.

The answer is simple.  One feeds the display input a conventional RGB signal since the display module is plug and play.  Internally to the driver chip, we perform  a gamut mapping from RGB to RGBW.  The driver can handle 24-bit color, but if one puts in less bits of color the module will handle that as well.

DisplayMate’s Twitter on PenTile Resolution

We came across a few tweets from Ray Soniera of DisplayMate yesterday where he made several comments about PenTile. And we wanted to address that.

When Ray Soniera says that PenTile has half of the R, G, & B subpixels as an RGB stripe he is correct. What Dr. Soneira is doing is counting only the R, the G, and the B subpixels… ignoring the W… and ignoring subpixel rendering.

First, imagine that we had a purely monochromatic B&W panel. Do we say it has no resolution because it has no color? (Seriously?) In the PenTile case, each white subpixel would be half of the B&W resolution, and the combined RGB triplet would be the other half. So, it looks like a full resolution B&W display. This is good, because the human eye can see tremendous detail in black & white… But not so well in color!

The human vision system can only see a very low resolution in pure color. In pure red to green color our eyes see only one tenth as well as it can in pure black & white. What we see in everyday life is a combination of pure color and pure black & white, so it seems very richly detailed.

So, having high resolution in black & white, but only half the resolution in pure color, is still more than we need. Why waste putting detail into color which we can’t see?

So, Dr. Soneira is right, we do have only half the number of RGB triplets… but that is a good thing.

RE: Expiance’s post on RGBW, PenTile, Subpixels and Graininess of mobile displays

I wanted to take a moment to respond to Alex Taylor’s blog post on Expiance.com last Friday. For starters, I am very impressed at how much thought and work you put into your post, Alex. Well done!

Still, I feel I need to add some clarification and correction to a couple of things you said in your blog.
Many people like yourself who have, for so long, thought of pixels as having a fixed number of dots, typically three per pixel, so it is not surprising you look at this layout and say there are two per pixel. Certainly, on the average that is true, but it is important to think of pixels in a subpixel rendered display as logical pixels.  This is not unlike it used to be for CRTs. How many subpixels are in a CRT spot? A CRT spot is comprised of a Gaussian distribution of light about a logical pixel center. Such logical pixels can overlap, but when the modulation ratio drops below 50% one loses resolution, per the VESA specification.
PenTile works much the same way.  As many as 10 subpixels can be involved in a given logical pixel, so it is misleading to say one pixel lacks blue and the next lacks red or green. Every pixel is addressed at 8 bits/color and each luminance center is lit by the proper combination of the layout and the algorithms that analyze the image and render the display. It is nothing like compression or zipping.

You seem to agree that pictures look similar for RGB stripe and PenTile. Imaging scientists call these images bandwidth limited images. I would say that these look equivalent between RGB stripe and PenTile displays and can show this show this with MTF characterization plots.

One correction to what you said is that those of us at Nouvoyance never say that PenTile looks identical to RGB stripe. There are differences, but the differences that people point out are sometimes not correct.  For example, we render black and white text perfectly.
I know how tough it is to take a good photograph of a display, but even with the ones you show of very small, single and double stroke  black and white text prove that black and white text is not fuzzy, blurry, or otherwise defective. Look at the single pixel at the top of the “n”, where the curve joins the upright stem. You can see that black pixel every bit as well on the PenTile displays as on the RGB stripe. There is some softness at the edges of each of these that is attributable to the original anti-aliased font, which is also fully and faithfully rendered on the PenTile panels; so there should be no doubt that for black and white text it is rendering perfectly.

You say ”… edges which appear straight on a RGB stripe display will appear jagged, with odd pixels sticking out, just like on those old camera screens, and vertical lines will zig-zag across the screen.” I think that the photos you exhibited to prove this seem to prove the opposite. The same could be said for horizontal line edges on an RGB Stripe, as the red and blue subpixels appear so much more darker than the green. What makes it acceptable in either case is the fact that the resolution is chosen to be high enough that the subpixels blend together by the human eye, when viewed at the appropriate distance.

Let me add that much of the IP for PenTile is in our algorithms. There are several adaptive filters that look at many aspect of images and provide sharpening to edges, especially things like diagonal lines.
You pointed out that this image above demonstrates that the low res layout causes a grid artifact. There is, in fact, some graininess that is possible for a fully saturated green on a black background. The algorithms, for anything less than fully saturated colors, fills in the black regions with white or other color subpixels. This is the same as what is experience on an RGB stripe display that is fully saturated green on black, but in the PenTile case it appears as a checkerboard whereas on the RGB stripe it appears as green vertical stripes, albeit 30% closer together for stripe. Most people will be hard pressed to see this on a 300 dpi screen even at close range. This is especially the case since the human vision system has less resolution in the diagonals. It is also why photographic dot half tones have the same diagonal grid pattern.

As for your assessment that there is a diagonal organization to the display, I would agree, but I disagree with your conclusion. So, allow me to take it up a notch on the technical aspect of the answer. I would agree that the MTF of the display is less on the diagonal for the PenTile OLED RGBG panels than on the horizontal or vertical, but in all directions PenTile can write to the Nyquist limit. While the MTF of PenTile is slightly less than RGB stripe on the diagonal for fully saturated colors, it is still well in excess of the requirement of the VESA/IMID standard of 50% modulation, so it is not reasonable to downgrade the resolution by a factor of 1.4.  For the PenTile RGBW, the MTF, even in the diagonals, is the same as the RGB Stripe panel for black and white, that is to say, that they both will show a checkerboard pattern of equal modulation when the diagonal resolution limit is reached. The checkerboard is the result of an alias that occurs in the original data, before it reaches either display.

Let me turn to one other aspect of fitness for use, which is another name for good engineering, it is known to vision scientists that the human vision system is less capable of resolving detail on the diagonal than on the horizontal or vertical. So the slight fall-off in MTF on the diagonal nearly perfectly matches the sensitivity to detail on the diagonals. Any advantage of RGB stripe in this direction is often not seen, especially as we get into the resolution range of theis WQXGA panel.

So, I am troubled by calling the PenTile resolution claim “somewhat dishonest”. Samsung is saying that our WQXGA display is a PenTile RGBW LCD. And Nouvoyance is even directing those who are interested to our website, showing how it meets the industry standards for modulation contrast ratio when measuring Michelson contrast through a moving aperture grille. This is the test provided by the industry’s leading experts in display metrology. We have disclosed a great deal about what we do.

Do PenTile displays look the same as RGB stripe displays?

No, they look different in some special cases especially at the lower end of the resolution applications for  those with very good vision and well trained eyes, and, as stated above, with a bit more of a textured look for fully saturated green on black. At the higher end of the dpi range, e.g. products with 3.1” wVGA PenTile OLED, I have yet to see even one person who has blogged about a specific product about it looking grainy or less than sharp.

PenTile RGBW can look better than RGB stripe for things like the glint from metal and the reflections from water. It takes that white subpixel to give it that extra punch.

It is very important to apply PenTile to the resolutions where it makes sense – where pattern visibility is not visible for the bulk of the market. To us at Nouvoyance this seems to be good engineering for making a product that saves 40% of the power over the equivalent RGB stripe and meets the needs of the product. Surely, battery life and brightness are important engineering design parameters that as a package make it fit for use.

In the WQXGA product at 300 dpi in a product that is typically viewed from a greater distance in normal use than for a smartphone, so I am hard pressed to think that anyone will feel that this panel will look grainy or textured .

I hope to see you at SID to show you how good this panel can look.


Altered photos showing PenTile comparisons to create a “grainy” effect

Today we’re seeing a lot of coverage about our new WQXGA tablet display module.  We’re proud of the positive reviews and reactions so far. One post caught our eye, from Phandroid, who posted some comparison graphics between PenTile SAMOLED and LCD-TFT displays. Unfortunately the source of the graphic was not cited, but it appears to our expert eye that someone has manually edited the SAMOLED image to superimpose an artificial grid over the top of the pixel structure. Their goal is to highlight a perceived problem of “graininess,” but unfortunately all the graphic does is confuse the viewer about what the real display looks like.

The piece also compares a color PenTile display to a black and white image. Which is not apples to apples at all… and no way to allow a viewer to truly compare the two displays. Please, in the future, give readers a fair opportunity to compare apples to apples by offering a fair and accurate comparison visual.

Questionable images aside, we and Phandroid can fortunately agree on one point: The super-definition of our newest tablet display will offer tremendous benefits over LCDs of the same resolution.