All posts tagged WQXGA

PenTile RGBW – Why it has Higher Contrast

Recently, when showing the new WQXGA PenTile RGBW panel to editors I was asked if this was an OLED panel.  When I asked why she thought it was OLED she told me it was because the contrast was so high.  I decided then to generate a blog to explain why PenTile RGBW has such high contrast.

First let me say that OLED panels have the best indoor contrast of any displays.  This is simply because they only emit light where they are driven.  This leads to extraordinary blacks.  LCDs have a lower level of contrast than OLEDs unless one views them outside, where the reflective component of the LCD optics starts to have an impact.

PenTile RGBW, however, has contrast that is higher than other LCDs both inside and outside.  This is entirely due to the nature of light leakage in LCDs.  As it turns out, LCDs primarily have most of their light leakage near the perimeter of each subpixel.  This is a result of the way that an LCD is fabricated and driven.

If one compares RGB stripe to PenTile RGBW you can see that there is far less perimeter for the subpixels in a PenTile RGBW.  Keep in mind that in a PenTile RGBW that we have one-third fewer subpixels that an RGB stripe.  This changes the shape of each subpixel from a 3:1 aspect ratio to a 2:1 aspect ratio as is illustrated below.

RGB Stripe LCD Perimeter

 

 

 

 

Remember that PenTile only uses 2 subpixels per pixel on the average, compared to RGB stripe that used 3 subpixels per pixel.  When one calculates the relative amount of subpixel perimeter in the PenTile RGBW, and compares this to the RGB stripe, one finds that it has 28% less perimeter to leak light.  This directly leads to a comparable improvement in contrast ratio.

Illustrated below is roughly how this leakage would appear if viewed at high magnification.

RGB Stripe LCD Dark State Leakage

RGB Stripe LCD Dark State Leakage

So it is should come as no surprise that a PenTile RGBW LCD appear higher contrast than the comparable RGB stripe LCD.

OneIndia Video Post

There was some terrific video coverage of the new Samsung WQXGA, PenTile RGBW 300 dpi tablet panel that was shown at the recent SID DisplayWeek.

While this video mentions other high resolution tablets, no company, other than Samsung, has publicly demonstrated any 10.1-inch prototypes of more than 150 dpi to date.

This video raises lots of interesting questions about the application of this panel to products, but, as I have already said, Samsung is still in the prototype stage of product development  so you will not see any tablets with PenTile RGBW 300 dpi within this year.

Samsung Experience Media Tour

300 dpi PenTile tablet panel

On June 6-7, Samsung hosted a media event in their amazing facility on the third floor of the Time Warner Bldg at Columbus Circle in NYC.

This gave us a chance to show off our 10.1″ WQXGA to editors and bloggers who didn’t have the chance to see this at SID DisplayWeek in LA. Scott Birnbaum VP of New Business Development for Samsung Electronics presented both PenTile and Transparent Display technology that Samsung is now developing. It is always very useful to collect live feedback on our newest displays.

Joel Pollack demonstrating PenTile RGBW display.

Day 1: SID recap

Visitors to the PenTile SID demonstrations at SID

Day 1 at SID is behind us and we’re pleased to say we had an incredibly busy day. The Samsung/Nouvoyance demonstrations were mobbed, almost to the point that it was difficult to walk through virtually all day. The demos of the new WQXGA 10.1″ tablet display, as well as those for the multiprimary PenTile displays, performed stunningly.  We were glad to see some tech industry experts, including some folks from Engadget, come through and take a tour of the new tablet display.

But we were also pleased to see that the PenTile multiprimary display demonstration got a bigger crowd throughout the day. We are encouraged that this means good things to come for our entire line of PenTile displays.

Demonstration of PenTile Multiprimary Display

Thanks to all who stopped by yesterday. If you’re in the neighborhood of SID, stop by our booth #707 and see the displays for yourself!

Engadget video review: 10.1″ PenTile WQXGA Tablet Display

Live from the SID 2011 show floor, check out one of the first reviews of the PenTile WQXGA tablet display, courtesy of Engadget. The video shows “why you should join the RBGW revolution” (their words, not ours).

Engadget preview of PenTile WQXGA Tablet display:

300 dpi is Fine but I Would Rather Have IPS

This is not an “either/ or” condition. This a case of having your cake and eating it too. PenTile RGBW technology is perfectly compatible with all types of wide viewing angle technology such as IPS, multidomain (PVA, MVA, etc). In fact, as a power saver it makes it a bit easier to use a wide viewing angle (WVA) technology with PenTile RGBW since many of these WVA techniques reduce light throughput.

IPS (in plane switching) was the name given to a type of WVA technology many years ago by Hitachi and was licensed to other display makers. Other variants of this methodology are in use by Samsung. Samsung uses a few different types of WVA technologies depending upon the application.

Perhaps there are some who are still asking, “Does a tablet PC that is being used by one person who is looking directly at the display really need WVA technology?”. The answer is a definite yes it does. Even a mobile display is used laying on the desk in front of you or held in your hands. Then consider viewing in both portrait or landscape modes and you realize that WVA capability is a generally a good idea.

So, here is the interesting thing about the new Samsung WQXGA PenTile RGBW prototype panel–it has a very wide viewing angle technology, not so different from IPS. Judge for yourself when you come see this at SID Display Week in LA this week.

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.

Regarding WQXGA Pixel Density

I’ve come across a number of comments made online today in regard to pixel density in the WQXGA display, and I’d like to address that. One post in particular, in response to an article on PCMag.com, said the following:

Saying that this screen has a resolution of 2560×1600 is pure marketing BS, and I’m kind of surprised that you fell for it. As you noted, “Or, put another way, a panel with the same number of pixels as a traditional screen will have higher resolution.”

That’s because there are only two subpixels per pixel: half of the pixels are red-green, the other half are blue-white. This means that no single pixel can ever produce the color assigned to it without help from its neighbors. If the pixel at x123,y234 is asked to produce color #ABCDEF, it can’t do that because it has no blue if it’s a red-green pixel, and it has no red or green if it’s a blue pixel. These displays fudge a 2560×1600 resolution by using the missing colors from neighboring pixels to fool the eye into thinking that the other pixel is actually displaying a color composed of all three primary colors. If the pixels are small enough, you may actually be fooled, but the image will be subtly inferior to a true 2560×1600 display.

I appreciate the passion that DOSGuy and others show, but I must disagree with assertions about resolution. They seem to be confusing pixels with subpixels or dots. And DOSGuy, in particular, sounds like he’s of the camp that believes that resolution is based upon counting dots.

That assertion is, however, in contradiction to how the world’s leading metrologists for the display industry, who have written the accepted standard for measuring display resolution. Display resolution is based upon measurement of modulation contrast ratio—more specifically Michelson contrast ratio. There is currently only one display metrology standard organization, Video Electronics Standards Association (VESA), who’s standard is now being combined with the ISDN standard for a new and comprehensive standard to replace the VESA Ver 2.0  standard by an SID subcommittee. Nothing in this standard talks about counting dots—nothing.

So why not? The reason is partially historical. At one time the display of choice was a CRT. It had a Gaussian shaped spot. Two adjacent spots overlapped and compromised resolvability when the overlap reduced  the modulation contrast ratio. The lower limit was then set  50%.

Later passive matrix LCDs came out that had well defined dots in an RGB stripe pattern and people could count dots. A white pixel had a combination of one red, one green and one blue dot. Still there was crosstalk, so modulation contrast ratio could be compromised.

Display metrologists realized that modulation contrast ratio was where the rubber met the road. It was what the eye really saw and what could easily be measured. What good did it do if there were lots of dots that bled into one another for any reason? For many years this definition using modulation contrast ration has stood the test of time with display experts.

PenTile displays meet and exceed the definition of modulation contrast ratio for the resolution as defined. In this case for 2560 x 1600, meaning that one can write a series of 1280 black and white line pairs in one direction and 800 line pairs in the other direction and can write diagonal line pairs in any other azimuth of the same pitch and always meet or exceed 50% modulation contrast ratio. While the spec on speaks of black and white lines the PenTile display can do the same with all other colors.

So can the PenTile display write any color at any pixel? Yes it can. Remember that we are dealing with logical pixels that are comprised of varying numbers of subpixels. What the instrument measures and what the eye sees is the center of luminance energy at each and every one of the corresponding 2560 x 1600 pixels and it is possible to write every color to each of these that one can write to an RGB stripe display. The instruments can measure this and the human eye can see all of these dots of all colors.

For more detail on Michelson contrast modulation measurements and PenTile, please read this white paper on the topic.

It’s definitely not marketing BS — it’s perfectly within the specifications defined by the display industry’s metrology experts.

5 Reasons to be Excited about WQXGA

This panel has a dot pitch of 300 dpi, which is as high as the highest resolution smartphone on the market today – and it’s in a 10.1” diagonal.

This allows for more than 5x the data of the display on other leading tablet displays. You’ll be able to watch an HD video at full resolution and still have room for other applications on the same screen. It’s amazing. Plus, all of this is possible while still operating at about 60% the power of an equivalent RGB stripe display.

Which makes the following five exciting things now possible:

  1. Detailed maps for the big view prior to zoom
  2. HDTV sports – plus stats on the same screen
  3. Magazine quality text and photos
  4. Photo editing with detailed thumbnails
  5. Portable repair manuals with details, charts and drawings