PenTile – A Gimmick?

There was a review at PhoneDog  by  Taylor Martin on July 18th of the Droid 3 which uses a PenTile RGBW qHD display  http://bit.ly/pP42xV.  He said:

“…One of the key features of the DROID 3 is the qHD display. I’m no display expert, far from it, actually. But the display on the DROID 3 is disappointing. It’s fairly bright, there is plenty of contrast and the color reproduction is spot on. That said, the “qHD” title of the display is more or less a gimmick. Motorola stuck with the same PenTile display as seen in previous devices, which is known for some gruesome pixellation…”

Mr. Martin’s article calling PenTile technology a “gimmick” has compelled me to reply on behalf of Nouvoyance, the creator of this technology.  [Mr. Martin corrected me to say that he did not call PenTile a gimmick, but rather called the qHD rating of the Droid 3 a gimmick.   This is a fine line point since the Droid 3 uses a qHD resolution PenTile RGBW display. ] PenTile display technology is the result of a decade of R&D and more than 50 issued US patents.  A lack of understanding of how we can use two-thirds the number of subpixels to achieve the same resolution as the equivalent RGB stripe has led this blogger to question the ability of PenTile technology to achieve the claimed resolution or in this case referring to it as a gimmick.

Perhaps the best way to understand PenTile methodology is to compare it to that which was done for CRTs in yesteryear when Gaussian distributions of energy mixed at the correct levels of chrominance gave rise to the right color at each and every pixel location http://bit.ly/lvIlsO.  As many as 10 subpixels can be used to write to any given logical pixel.  Through the use of subpixel rendering and PenTile algorithms it is possible to render details such as fine black and white text equally well to RGB stripe.  You can see proof of this yourself at an earlier blog on this site http://pentileblog.com/?p=619 where tiny, single stroke fonts were compared between RGB stripe, PenTile RGBW LCD, and PenTile RGBG OLED.

PenTile resolution meets the only industry standard for resolution, developed by the top industry experts of the VESA committee who have defined resolution in terms of modulation contrast ratio for black and white line pairs, not based upon counting dots. Proof of this is can be seen at http://bit.ly/qLX9Xf .  It is not, by any definition, a “gimmick” as the author suggests.

Gruesome pixellation?  Well, for fully saturated solids like green on black, if you have the ability to view it from rather close, you will see the pattern that give an impression of a texture or graininess. Not everybody thinks this is so gruesome.  Such pattern visibility or graininess is not visible for anything except for fully saturated green on black backgrounds or single stroke black text on fully saturated green.  Pattern visibility is there for RGB stripe as well, but it has been many years since I have heard that called gruesome, since we are accustomed to seeing it.

So why does Motorola use PenTile?  It saves nearly half of the power of an equivalent RGB stripe display for typical usage and more for black and white like ebook applications. Some like akronevan2, a commenter at Android Central, have already noticed this benefit and changed their minds about PenTile http://bit.ly/pXaftL.  Displays are one of the major consumers of power in a handheld product.  As the industry migrates toward higher and higher resolution where display transmissivity declines, in phones with more and more horsepower, saving power will become increasingly important to those wanting a slimmer, lighter, brighter and more powerful smartphone. The author did acknowledge that it looked very bright and with good color.  PenTile is an engineering choice that is fit for use in this type of high performance handheld product.

Those who can see a panel from 3 inches away, and who expect to see an RGB stripe pattern, may be troubled to see something different, and if this describes you, then perhaps this technology is not for you.  For those others who look at phones from 12 inches away and do not go looking for the pattern visibility in fully saturated colors, please consider PenTile displays for the total performance of a phone and display. With that in mind you may find that this very much fits the bill for you.

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Today, 8/2,  Mr. Taylor of PhoneDog went back to further clarify what a “gimmick” was and why the qHD rating of the DROID 3′s display is still a gimmick.  http://bit.ly/pndwEK

There is one section of this blog to which I would to post further reply:

“…For starters, let’s begin with the definition of a gimmick. From the online Merriam Webster dictionary, the term (marketing) gimmick in the context it was used is “a trick or device used to attract business or attention.” The term qHD is an abbreviation of the term “quarter HD,” implying that the resolution of the DROID 3′s display is higher than those of standard definition (WVGA or 800 by 480 pixels). Even though the qHD display found on the DROID 3 is technically a higher resolution, this particular display shows more pixelation and grain than that of a standard resolution display (i.e.: EVO 4G, DROID X, Nexus S, etc.), thanks to the PenTile subpixel layout. Any average consumer will see “qHD” in a long list of specifications and assume the display on that particular phone is better or more clear than that of its counterparts. This is not the case with the DROID 3, Atrix or DROID X2, plain and simple…”

My reason for reacting to the word gimmick was that it has many negative implications, varying from ways to gamble dishonestly to ingenious and novel devices (from Merriam Webster the rest of the definition below).

Merriam Webster Definitions of "Gimmick"

So is PenTile technology a “trick or device used to attract business or attention” as Mr. Taylor implies?  He clarified his comment today to indicate that he was referring to the Merriam Webster marketing definition (2c) of gimmick, which implies it was (only) used to attract business or attention.   Perhaps one could perhaps argue that a camera on a phone is a gimmick, but you might be less inclined to say, for example, that a touchpanel is a gimmick.  I cannot deny that we sought to create new business.  The fact is that in several of these designs PenTile has been an enabler.  Smaller diagonal (<4.1”) wVGA OLED, simply stated, would not have existed without PenTile.  So if you don’t think that 3.1-inch or 4.0-inch wVGA is a gimmick, then PenTile should also not be considered a gimmick.

For LCDs our goal has been to offer a way to get to far higher resolution without paying the penalty of power or brightness in order to enable designs that would otherwise have not been offered in the market.  It has always been our intention to grow business for high resolution phones that would attract attention.  An amazing number of OLED and LCD display phones have come to the market thanks to PenTile technology.  For the better part of two years it attracted little if any attention since nobody even noticed it was PenTile or cared how we enabled those phones.

At this blog I have pointed out in several entries that pattern visibility is greater for PenTile for fully saturated colors like green on black, but also pointed out that for PenTile RGBW that whites are more brilliant with extraordinary punch. There are benefits and tradeoffs with every technology.  Nobody associated with this product development ever  said that PenTile displays looked better than or even the same as RGB stripe displays of any particular resolution. Mr. Taylor indicates that it is implied by the qHD label and is generally would be understood to look better by virtue of this spec. This  qHD spec means nothing other than the resolution that display can be measured to show.  No two display technologies look the same.  We can even see the subtle differences between different backplane technologies or WVA technologies, so certain people who look for it can see difference between subpixel rendered displays and conventional RGB stripe. When Mr. Taylor says he likes the Nexus S display better than PenTile, he probably didn’t realize that the Nexus S is also a PenTile design, so perhaps not all PenTile displays are created the same.

I do take issue with the term pixelated.  For years in the display industry, pixelated has referred to having blocky lines and text due to having too large of a pixel.  If anything, subpixel rendering reduces that jagged appearance of diagonal lines, much as is the case for Microsoft’s ClearType where subpixels are also used to soften pixelation.  We should not confuse the term pixelated as appearing grainy or showing pattern visibility.  All displays have pattern visibility. The pattern visibility of a PenTile display is similar to the pattern visibility of an RGB stripe of one-third lower resolution.  If you are not using in a high resolution display, pattern visibility can be noticeable for more people.

The world’s leading experts in display metrology of the VESA (Video Electronics Standards Association) have defined display resolution of black and white line pairs in terms of Michelson contrast modulation ratio measured through a moving aperture grill.  Mr. Taylor seems to agree that we are “technically” higher resolution, but says that it is  “implied” that a PenTile qHD resolution should look better than an RGB stripe wVGA.  The fact is that nobody ever said anything of the sort, although some users have said on blogs that they think it does look better.  I am not sure what people think that “resolution” means.  We do claim it to have higher resolution, because, by the only Flat Panel Display Measurement Standard Ver. 2.0, Section 303-7, we measure and see more than 50% modulation of black and white lines, 540/2=270 line pairs by of 960/2=480 line pairs, whereas this cannot be done for a WVGA 800 x 480 RGB stripe display, plain and simple.  Such a definition has nothing to say about any screen door effect of PenTile displays, or the stripiness of RGB stripe displays, or pixelation, or any other artifact that may be present in any display independent of resolution.

In the 1990s I can remember people being very upset with the pattern visibility of RGB stripe; they seriously missed the familiar look and feel of CRTs.  For some percentage of people who have better than average visual acuity the checkerboard organization of PenTile jumps out at them because they are not accustomed to this.  The texture of pattern visibility apparently bothers people like Mr. Taylor, a great deal.  Others either don’t see it or are not bothered by it and simply appreciate the benefits of power efficiency that PenTile has brought to the market.  This is a very individual thing.  Do not take the word of bloggers.  Go look for yourself.

 

12 comments on “PenTile – A Gimmick?

  1. I guess the “gruesome” pixelation of the pentile screens comes from the fact the screen has less horizontal subpixels of each color compared to RGB stripe for the actual resolution of the screen. If we do the math this way – qHD screen which is 540 pixels wide, instead of having 540 individual pixels that can be lit in any color has like 405 (2/3). Which is less than WVGA’s 480 classic RGB stripe. Or pentile technology is using less sub-pixels to try to display same amount of actual pixels compared to RGB. Something like the “interpolation” in the older projectors which had 800×600 matrix, but were capable of displaying 1024×768 images. Everyone will agree picture quality suffers when doing this. What pentile does is bringing similar idea on a sub-pixel basis – no?

    So based on what the display is showing, quality could suffer. If it is a picture with fluent color transitions, image will be very good, but if it is solid colors, like business graphs for example, it will seem pixelated, compared to presumably “lower resolution” RGB WVGA of same physical size. And because today’s mobile OS user interfaces are more like business graphics, screen might look “gruesomely” pixelated especially at the beginning. Droid 3′s battery charge indicator is a great example for this.

    The pentile “pixelation” problem will disappear when they bring the pixel density high enough. Good example is Nokia E6 – screen is pentile, but due to the much higher pixel density, it doesn’t look pixelated held at same distance as Droid 3 or Motorola Atrix for example. I guess this discussion will be put to an end once the 4 inch displays with resolution of 1280×720 become main stream.

    • Leobg, thanks for posting your comment. I appreciate your effort to better understand PenTile technology and for the opportunity to answer some of your points. I would like to first of all replace your use of the word pixelation with pattern visibility. These really are different things. In the next few days, Candice Elliott, our CEO and Chief Technologist, promised post something her to better illustrate the difference. That said, pattern visibility, can be problematic for some people looking at PenTile displays, but it really has nothing to do with resolution. Pattern visibility is there because the subpixels are one-third bigger and same color subpixels are a bit further apart. That is why PenTile only works best for high resolution panels.

      We display 540 horizontal pixels, each of which can have chrominance information from as many as 10 subpixels. These logical pixels do not have any overlap in luminance, and we always maintain 100% modulation contrast ratio (remember 50% modulation contrast ratio is the minimum spec). In short, you can see any color you choose on a string of 540 pixels across the screen and you will have more than a 50% modulation contrast ratio between any two adjacent pixels (much like was true in days of color CRTs, but PenTile is measurably sharper in definition). This is not like interpolation. Candice will explain this in more detail soon.

      So where do people see objectionable pattern visibility on PenTile RGBW LCDs? They see it on lower dpi screens, when viewed from a relative close distance; and when they are looking at fully saturated color like green or red on black backgrounds. Blue is no problem since the human vision system cannot focus well on blue. If it is anything less than fully saturated color then the algorithms can fill in the dark wells that are otherwise present with a little white or other colors as needed. Droid’s totally saturated green battery indicator is, unfortunately, one example of this patch of fully saturated green.

      The other reason that people see pattern visibility for PenTile is that they are not accustomed to the checkerboard periodicity of the pattern as they have spent years looking at a stripe pattern. The human vision system and brain have the ability to filter out such patterns over time to make them unnoticeable. I can see the pattern visibility in every one of my RGB stripe screens, but I no longer think it is gruesome since i have developed the ability to filter this out from the image information. I no longer see this. In time, people will do the same for PenTile layouts.

      You are right about the move to higher resolution. There are many phones with PenTile that nobody ever noticed anything different even for patches of fully saturated green, such as 3.1″, 3.3″ and 3.5″ WVGA PenTile OLED displays. The same will be true for PenTile at 270 – 300 dpi for tablet displays, especially considering the increased distance from which this are typically viewed.

      • I would agree that it is not a pixilation problem and more of a pattern problem.

        I can see the pixels in the green as you stated, but where I see the biggest pattern issue is when things are moving. Looking at a static screen all is good. As soon as it starts to move It appears to have diagonal lines all across the display with the shades of grey appearing to be the worst…and I can see it at a 12″ distance.

        I have the new Photon so it is the larger 4.3″ display. When I look at other phones, HTC 3D, I do not see that.

        It is disappointing to see that, but not necessarily a deal breaker. Is it possible that a faster refresh could help that issue?

        • Jeepdude, thanks for taking the time to explain this more completely to me. At 4.3″ this is the largest PenTile display to be marketed, but at 256 dpi it should look fine. I have yet to get my hands on the Photon, but will make it a point to do so at the earliest convenience. Is there any chance that you can send me a copy of the images where this is worst? There is nothing intrinsic to our subpixel rendering algorithms that would make such a diagonal artifact appear for moving images versus static. While several possibilities for a cause are being tossed about here, I want to look at this first before further comment. You can send that image to my Twitter account @PenTile_Tech. Thanks again–Joel

          • I am not sure I have a camera that would pick it up correctly. Like I mentioned, when the image is static, it looks fine. Not sure I can send a picture of it moving and have it display the same thing I am seeing.

            It reminds me of the older DLP sets Mitsubishi used to make. Instead of having square mirrors, they went to diamond shaped mirrors. It looked good when images were static or moving up, down, left or right, but when moving diagonal, it was easy to see artifacts in the picture.

            It may just be they way the gaps in the pixles are reacting to the movement of the screen. Instead of looking at one fixed spot your eyes are scanning along with the image and picking up the gaps in the pixels better.

            I have done the same thing with my daughter’s EVO 3D, and the Sprint Nexus at the retailer and I have not seen antything like that.

            Thanks for the replies,
            Bryan

          • Bryan,

            Rather than a photo, is there any particular website that shows this up particularly well? I am organizing an outing to the local Sprint store with a couple of our Nouvoyance experts to have a closer look at the Photon. — Joel

          • Bryan,

            We went to have a closer look at the Photon.

            At first we could not see the diagonal lines on the demo here, but thanks to your guidance, when looking at the gallery application, where the apron below the photos is gray, we could see some faint diagonal lines when the photos were moving. Actually, for the same image in a fixed position I could see this if I moved my head or rotated the display. I am not yet sure that we know 100% for sure what we are seeing, but it is very unlikely a PenTile effect as PenTile algorithms have no preferred direction. Still we, at Nouvoyance, are trying to figure out what it can be. Would you have a chance to compare your phone to another Photon at the Sprint store to see if the effect is the same level for both? If our theory is right, this effect will vary in severity from one phone to the next.

            Thanks!- Joel

    • So what do you really think?

      You are somewhat misinformed on your point about Samsung switching from PenTile to RGB. While there was press that said such things, the fact is that Samsung has not dropped PenTile for production of designs.

      PenTile technology has never been recommended for displays below a certain level of dpi since pattern visibility become objectionable to larger numbers of people. When Samsung decided to offer a 4.3-inch and a 4.5-inch WVGA the pixel dpi was too large for PenTile design rules. The fact remains that Samsung is still making a very large number of PenTile displays for phones, both captive and OEM. There are still new designs in the works. PenTile was featured in a new 300 dpi tablet design (10.1″ WQXGA format). I covered much of this in an earlier blog http://pentileblog.com/?p=193.

  2. NO.

    PENTILE IS BAD AND YOU SHOULD FEEL BAD FOR MAKING IT.

    It’s not “horrible”, it’s outright awful. If Milestone 3 comes with this garbage I’m _NOT_ buying it and I swear to god I so really wanted that phone.

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