PenTile for 720 HD OLED Smartphones

With the introduction of the 4.65-inch 720 HD OLED, people have now figured out that Samsung is still heavily invested in using PenTile OLED technology for high resolution applications.  The reality is that this is the only way to achieve 300 dpi OLEDs.  When people try to compare this technology to other panels it is not possible to compare a PenTile OLED at this resolution to any other high resolution RGB stripe OLED for one reason.  Such RGB stripe OLEDs do not exist .  Such technology is not possible.

When people say that this is a low cost alternative, they have it entirely wrong.  It is not less expensive to make and there is no high resolution alternative.  We only wish it were lower cost, but so far that has not proven to be the case.  Yes, a 720P OLED could be made, but only if it were one-third larger diagonal, which no doubt would most likely be more expensive.   The use of PenTile technology for OLED has been to achieve high resolution for OLED, plain and simple.

One blog http://techcrunch.com/2011/10/20/the-scourge-of-pentile-returns-with-the-galaxy-nexus/

by Kevin Coldewey of Techcrunch  says, “..For me personally, it’s a deal-breaker sight unseen…”  How can someone who claims to be an expert criticize a technology without seeing it?  PenTile has been continually improved and now is being used at a level of dot pitch where it makes more sense than ever. Still Mr. Coldewey is quick to criticize without the benefit of looking at it with his own eyes.

In this same blog, Mr. Coldewey shows our diagram that demonstrates how it can get resolution with one-third fewer subpixels, but then asks, “Does it seem logical to you that a display can increase the number of pixels created by a number of sub-elements by a third and suffer no ill effect?”  First of all I should point out that Nouvoyance never said that there were no differences between RGB stripe and PenTile displays, but that we have designed them to work well with the human vision system to take advantage of the ability to discern high resolution for luminance.  The human vision system has far less resolution for chrominance, so any relative loss of chominance resolution by PenTile is of little impact.  In short, PenTile displays are designed to look virtually the same as RGB stripe displays when applied to high resolution formats.  Through the use of subpixel rendering, along with some very effective image processing algorithms, we have achieved the ability to make displays that have superb performance at high resolution.

The analogy would be image compression.  Does it seem logical that the electronics industry can achieve image compression, allowing high quality images with so much of the raw data removed?  Perhaps to the uninitiated it seems illogical, but to the well informed it is totally logical.  The same is the case for those who are well trained in the principles of imaging science when they fully grasp the principles of PenTile image processing  technology.

Again we are seeing people going down the path of counting dots and trying to discount the resolution that is published in the spec.  This has been covered many times in the past and can be reviewed on this blog http://pentileblog.com/?p=712 and http://pentileblog.com/?p=809 where we show how this panel meets the only industry spec for display resolution from VESA http://bit.ly/qLX9Xf .  I also have published  http://pentileblog.com/?p=778, a reference to an article by the industry icon, Alva Ray Smith, written in 1995, well before PenTile.  This article makes the case very clearly that pixels are not little squares of red plus green plus blue dots.  Instead, a pixel is a simply a point plus a reconstruction filter.  It is nothing more.  PenTile uses an area resampling methodology that uses such a reconstruction filter to bring the desired luminance to each and every pixel in the display.  Color resolvability, albeit less than luminance, also can be realized at this spec.  The human vision system can resolve far less accurately the position of color than luminance so it enables PenTile to be an engineering solution that is fit for use.

Perhaps the biggest and most valid criticism of PenTile technology has be pattern visibility since the pattern is one-third larger than that of RGB stripe.  As we get to these very high resolution formats such pattern visibility disappears.  It is only easy to see the differences between RGB stripe and PenTile through the use of magnifiers.  Yes it is different than RGB stripe, but it doesn’t matter.  One has to doubt the credibility of the pundits who are so quick to criticize PenTile before they even take their first look at these panels.

My hat is off to to Daniel P at PhoneArena.com http://bit.ly/nDAdaq who provided a well-studied and balance review of PenTile OLED in this application.  As he pointed out, we have been very open about the benefits and deficits of PenTile technology and will continue to do so.  We will however continue to provide corrections when the technology is falsely implicated in artifacts that are not caused by PenTile.

One valid criticism of these new panels is that the white point is a little too blue.  This is not a PenTile issue, but rather a design choice of the panel maker since such a bias toward blue favors the lifetime of an OLED panel .  This is true for both PenTile OLED and RGB stripe OLED, so it would be good if people would stop attributing this to being a PenTile artifact.  Likewise, there has been some criticism of color shift off axis for PenTile OLED.  Again this is not a PenTile artifact, but is a result of thin film interference in the OLED layers.  This would be the case with an RGB stripe OLED just as it is for PenTile OLEDs.

Another invalid criticism is that of banding .  That was an issue last year with the original Nexus One when 5-6-5 color depth was input into the 8-8-8 PenTile engine for certain SW applications.  These new products are, to the best of my knowledge, all 8-8-8, so there is no banding to be seen.  If people claim this is still present, they need to provide some evidence rather than just conjecture.

It is our impression that consumers will be delighted with the new PenTile OLED panels in the 720P format.  The industry is now coming into the sweet spot for PenTile technology.  Do yourself a favor and go look at this with your own eyes rather than taking the word of those with a predisposed bias and an anti-PenTile agenda.

9 comments on “PenTile for 720 HD OLED Smartphones

  1. I’m really sorry you have to write these blogs to deal with ignorant people like Mr Coldewey. At the same time I’m glad you do write them to show people that writing articles from ignorance is not journalism, it’s sensationalist fictitious headlines.

  2. I would refrain from statements like “such technology is not possible”. Especially with technology things tend to change rather quickly. This year it might not be possible, next year it will be “old technology used by discount brands”. I am totally not going to be surprised if we see Galaxy Nexus 2 next year (or whatever they decide to call it) with super AMOLED PLUS 720p screen (RGB stripe).
    But let’s wait and see.

    • What I said was that an RGB stripe OLED in this dot pitch was not possible. I didn’t say it will “never” be possible. Even if LITI can deposit OLED at sufficiently high density to get past the shadow mask issues, the luminous efficiency of OLED materials just are not there “yet”. We have heard that PenTile was a “temporary” solution for high resolution OLEDs four years ago, and still the progress with OLED materials has not improved as quickly as the demand for higher resolution OLEDs has increased. There is still room to go to get to 50 cy/degree of resolution that the human vision system can see. We are not getting into a much better range for PenTile where it merits can be better appreciated.

      • “Yet” – that’s the keyword. I would have not thrown in the comment I did if “yet” was present in that sentence.

        Anyways – I am eager to see that screen (Galaxy Nexus) in person. If I am doing the math right the physical sub-pixel density is pretty much the same as on Galaxy S II (4.3 inch Super AMOLED plus screen), which certainly doesn’t look bad, except maybe a bit too over-saturated in colors.

        • Ivan- The 720 HD format on 4.65-inch has a pixel density of 315 dpi whereas a WVGA 4.3-inch has a pixel density of 217. The subpixel density would be the same for the horizontal, but is definitely higher for the vertical as PenTile only eliminates subpixels in one direction. While it is not as simple as comparing subpixel density, since subpixel rendering does allow better resolution, when some multiply the subpixels by 2/3s in both horizontal and vertical directions it is discounting the subpixel density one more time than is reasonable. I would expect that you would find the 720 HD on 4.65-inch to look better.

  3. Bret, I can accept that not everyone will accept the look of PenTile, but please understand that there are many consumers who appreciate the benefits. As we get into the range of higher dpi those who will see a “bugscreen” for fully saturated color on black will continue to diminish.

    I have heard from those who appreciated the battery life and the improved outdoor viewability. There continues to be choices for people. As long as that is the case, OEM phone makers will judge the merits of PenTile by how consumers vote with their dollars.

    • Consumers really do not make the choice. Or do they? Let’s take an example – Motorola Atrix. Original Atrix shipped with qHD 4 inch LCD screen based on RGBW pentile matrix. I can clearly see why Motorola chose to go with it. Outdoor visibility and especially battery savings were the major decision pushers. I remember the first time I saw the ATRIX I was unpleasantly surprised to see that screen looked less crisp compared to my older DROID2. I was expecting better pic than what I have with the D2 due to the higher (qHD) resolution and overall pixel density. Then the whole PenTile talk started. So it wasn’t my eyes wrong, throwing in the “2/3″ adjustment in the equation made a lot more sense.

      Now – freshly introduced ATRIX2. “Traditional RGB screen”.
      So you seem to turn to be right people make the choice after all.

      Don’t get me wrong – I am not against the PenTile technology. Now I use Droid 3 and love the outdoor visibility of the screen. Nokia E6 proves PenTile LCD screen can look as good without the “insect screen” effect. Just get the DPI north of 300 and everyone will be satisfied.

      • We have been trying to shoot ahead of the duck. Only now is display dpi catching up to where we would like it to be. Even at 300 dpi not everyone will be satisfied, but those who will see any screen door effect on saturated patches of color will be a significantly reduced population.

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