All posts tagged qHD

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.

 

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).