Nouvoyance CEO to Give Keynote Address at Interactive Technology Summit

Candice Brown Elliott will be giving a keynote address at the IHS Technology Summit on Friday, 25th of October 2013.  The abstract of her talk is:


Keynote – Leveraging the Human Vision System: A Roadmap to High Performance Displays


The path to displays that are both high performance and cost effective is being blazed by students of the Human Vision System (HVS).  Simply using more of the same, same pixel structures, same colors, same architectures, leads to diminishing returns.  But knowing how the HVS operates and what it needs to create high performance perception can guide us to high performance displays, at lower cost.  Ms. Elliott will layout her vision for the path toward high resolution, high frame rate, very wide color gamut, high dynamic range displays by first showing the HVS landscape. 

60″ Plasma HDTV w/ PenTile RGBG Now Available

Samsung is now selling a PenTile RGBG 60″ HDTV Plasma television,  in the F5500 and F5300 series models.  This has the same subpixel structure and layout as the (pre-S4 Diamond subpixel) PenTile OLED panels.  At Nouvoyance, we’ve been using a preproduction unit in our conference room for nearly a year, to test it in real world conditions, after we evaluated and measured it in our display lab.  We are quite happy with it.  The CNET review was mostly positive, save for some concern for loss of contrast in bright environments (like well lit TV studios).  However, for most home entertainment environments, this isn’t a problem.

The use of PenTile technology in plasma panels reduces the power usage of the display.  Given that a typical home TV is used for 34 hours a week, this is not a trivial concern for one’s electricity bill, nor for the power utilities.


Where Can I Learn More About PenTile Technology?

Book Cover:  Mobile DisplaysI occasionally get asked this question at conferences and symposisia. I always point to our website and this blog, of course, but oft times, my interlocutor is interested in a deeper, more technical understanding. For this, I can proudly point to chapter 12, “Image Reconstruction on Color Subpixelated Displays”, of Mobile Displays: Technologies and Applications of the SID / Wiley series. Although the book was published five years ago, it is very up to date still.  For the engineer or technologist interested in the theory and operation of PenTile displays, both OLED and RGBW, it is a very good place to start.

This chapter includes a background on the history and theory of subpixel rendering, optimization of color subpixel layouts for subpixel rendering, a simple method to generate subpixel rendering filters, RGBW color theory, Dynamic BackLight Control (DBLC, aka global or local dimming of the backlight to save power on RGBW LCD displays without compromsing image or color quality), and finally, the data processing pipeline used in all PenTile digital signal processing cores.  In writing this chapter, I viewed it as a basic primer on the technology, though of course, many details were left out by necessity in favor of brevity.

The book may be purchased at the Society for Information Display website bookstore.

Handing Off the PenTile Blog to Nouvoyance CEO – Candice Elliott

This blog will be my last as I hand this blog over to Candice Elliott, the founder of Clairvoyante and the principal inventor of the technology we refer to as PenTile.  PenTile technology has experienced a long and arduous evolution over which we have learned many important lessons.  Some have said that the technology was introduced too soon—business compelled us to introduce the technology into phones at 280 PPI and less, where some noticed pattern visibility.  Now that the standards have moved well beyond 300 PPI, to even 441 PPI for the Galaxy S4, there are few who can see any pattern visibility and are enjoying the benefits of PenTile technology.

Although Motorola and Nokia had developed phones based upon PenTile RGBW LCDs, PenTile LCDs have seen less adoption than has PenTile OLED.  However, now that resolution is creeping up for tablets to match that of phones, we again are seeing new opportunities to bring PenTile RGBW LCDs to the market to solve the battery life and brightness demands of tablets.  Samsung Display demonstrated at Display Week both the 10.1” WQXGA (2560 x 1600) “Green” display as well as the 13.3” 3200 x 1800.  Keep your eyes open for these in tablets this year.  The 10.1” WQXGA is already being used by one tablet provider in the USA and reviewers have noted the very long battery life that is spec’d.

Although I will be moving on to new challenges elsewhere, I remain a dedicated user of PenTile based products and foresee a continued path of adoption for PenTile technology as people continue to buy thinner, lighter and higher performance consumer electronics.  There is still no technical display solution that surpasses the benefits of PenTile for highly efficient, high resolution displays.



Joel Pollack

GAlaxy S4′s Diamond PenTile Display

Today I had my first chance to lay hands on the production version Galaxy S4 in an AT&T store.  My feeling was that it would be an incremental improvement over my Galaxy S3, but I was soon convinced that I would trade in my S3 in a heartbeat.  Not only was the HD screen able to display more information in crisp detail, but the phone gave me the impression of being smaller, thinner, lighter, brighter, and faster.

It is no secret any more that the display in the new Galaxy S4 is configured a bit differently and has been given the nomenclature of Diamond Pixel by Samsung, but as Bogdon Petravan  pointed out in his comprehensive article, the diamond shape refers to the subpixels.  ( )  The pattern is actually much like the pattern in the Galaxy S3 in that is uses subpixel rendering and PenTile type algorithms to achieve the resolution.  The diamond shape is Samsung’s innovation further improves the fill factor and is useful in their drive toward still higher resolution OLEDs.  As you can see in this photo that Ray Soneira of DisplayMate obtained from Samsung, there remains a difference in the suppixel area of the red green and blue subpixels that correlates to the relative efficiency of each of the OLED materials. (

There are as many green subpixels as there would be for the legacy RGB stripe configuration, but there are half as many red and blue subpixels.  Thanks to subpixel rendering there are just as many pixels as for the RGB stripe displays with 2/3s the number of dots.  At the resolution of 441 pixels/inch reviewers no longer able to see any issues with text clarity even for the most challenging fonts such as red on black.

Diamond PenTile Layout micrograph from Samsung via Ray Soneira

Galaxy S4 raises the bar with 440 PPI PenTile OLED display

With the introduction of the Galaxy S4 and its 440 PPI PenTile OLED display, a new bar has been set for high resolution OLED displays and for high performance smartphones.

Friends and colleagues have heard me repeat an old expression, “ There is no such thing as being too thin or too rich.”  When it comes to displays it seems that there is a similar thing that can be said that a display cannot be too thin or too high in resolution.  In point of fact there are people who are too thin and there are limits to how much resolution can be seen.  But, we are not at that top end resolution yet.  My prediction is that the march toward increasingly higher resolution will end only when we get to 600 PPI.  The reason for this is that there are people who can focus (accommodate) a display at very close distances and can also resolve 50 cycles/degree.  Consequently, there will be some people who can still perceive pattern visibility.  At 440 PPI the PenTile OLED in the Galaxy S4 has exceeded the ability to see pattern visibility for all but those very few people with better than average accommodation and visual acuity.

At 440PPI the only way to retain the brightness and lifetime of an OLED display is with PenTile technology.  Don’t get me wrong, Samsung has made great strides in pushing their resolution capability to higher levels for both RGB stripe OLED as well as for PenTile OLED.  There have been reports that this is a result of combining PHOLED for improved red and green efficiency and OLED technology for blue (  Such a technique would allow for red and green subpixels to occupy still smaller percentages of the display real estate.  If a 440 PPI PenTile OLED is possible, then, by definition, an RGB stripe at 293 PPI is also possible.  That said, even for a 293 PPI display if one uses PenTile technology one can push up the brightness to improve outdoor viewability—a better choice for most users.

One blog today (  ) quoted me as saying that there is no technical solution for replacing PenTile in OLED smartphone displays on the horizon.  This is due to the inherent weakness in blue OLED materials, as confirmed to me by Professor Ching Tang, the inventor of OLED technology.  He said that the energetics involved in blue quantum excitation was at just at the right level to break the bonds in the OLED materials which means that there’s no solution in the forseeable future for improved blue OLED efficiency.

Can OLED displays extend beyond 440 PPI?  Only time will tell.

Galaxy S3 beats iPhone5 for best device of 2012 – CNET










Galaxy S3 beats iPhone5 for best device of 2012 according to Lindsey Turrentine of CNET.

After reviewing  the 10 best and most influential tech products of the year CNET found the Galaxy S3 as the leader and “worldwide hero”.  She specifically cited the large, vibrant HD display as a key attribute.  This phone uses a 300PPI HD PenTile RGBG OLED display.

Industry Pioneer – Bill Hill Passes

It seems that all that I am able to blog about this week are industry pioneers who have passed away. Perhaps this has more to say about the maturity of our industry then about the health of our contributors.  There was a nice writeup in Forbes


Hill started out as a newspaper writer for 20 years in Scotland. In 1986 he joined Aldus to work on the development of their PageMaker layout program. He moved on to work at  Microsoft in 1994 to run its typography group and left Microsoft in 2009 to work on screen-reading projects. He died last Wednesday of a sudden heart attack.  He will be most remembered for his contributions in the development of ClearType, the application of subpixel rendering to the display of fonts.  It is difficult to imagine anyone who has not had the use of ClearType in today’s world.

Without question Bill Hill will be one of those people who so many will miss.



Industry Pioneer, Bryce Bayer, Passed Away

On November 13th the digital imaging industry lost one of the key pioneers, Bryce Bayer, who died in Bath, Maine at the age of 83. While working at Kodak he understood the key issues associated with digital cameras even before there were any digital cameras.  He used his knowledge of human vision to design a color filter layout for imaging sensors that more closely mimicked how the human vision system perceived images to more efficiently capture higher resolution images.  Our eyes primarily see luminance in green and resolve primarily through the modulation of luminance, rather than chrominance.   By developing a layout of filters that populated colors in ration of 25% red, 50% green, and 25% blue it was possible to emulate the manner in which the human vision system primarily uses luminance to resolve details.  The layout he used is shown below:

Bayer color filter pattern














Today this layout is universally used in all digital still cameras and smartphone cameras to enable ultra-compact cameras to capture images that are far better than would have otherwise been possible.  We owe Bryce Bayer an enormous debt of gratitude for his fundamental inventions in digital imaging and digital photography.  No doubt he will be missed by many.

PenTile and Sharp Eyesight

Here is an email I received from someone who was unable to post his comment:


Hi Joel,


I could not find a way to leave comments on the PenTile blog site, so I am emailing you instead.

I went to a Verizon store recently to look for a good replacement for my old Droid, and the widespread adoption of PenTile displays is significantly reducing my options.  The contrast, brightness, and saturation of Super AMOLED displays is excellent, and to my eyes they look superior to LCDs from a distance of a few feet or more, but held close enough to read, the PenTile checkerboard pattern is very apparent and distracting, especially at ppis in the mid 200s.  It’s less perceptible at 300-330 ppi in the latest applications, but still noticeable enough that I wouldn’t want to own one.

I understand the principle of the PenTile sub-pixel arrangement and sub-pixel rendering (which can also be applied to RGB stripes or other patterns), and find it very interesting.  However, there’s just no getting around what PenTile actually looks like to people with sharp eyesight.  It makes text, lines, and edges look fuzzy, and solid areas (other than green which is on every pixel) look visibly grainy.  For PenTile to look as crisp and smooth to my eyes as an LCD retina display at 326 ppi, it would probably have to be at least 400 ppi, maybe 450.  Once PenTile displays are in that range and I can no longer see the ugly artifacts, I will have no complaints with them.  Until then people with sharp eyesight like mine will continue to hate them no matter how good the contrast, brightness, and saturation.

For people who just don’t get it, and think PenTile displays look fine, try reading small text and looking at colorful and detailed pictures and icons on one through a powerful magnifying glass for a while.  That’s what it looks like to some people all the time!  Then do the same with an LCD, and even if you can see the sub-pixel pattern it doesn’t look nearly as annoying.  In fact, I would take a full RGB display over a PenTile display with the same number of sub-pixels any day, even though the ppi would be almost 20% lower and the brightness would be somewhat lower.  I can’t wait until Super AMOLED Plus (full RGB AMOLED) or 400+ ppi PenTile displays become mainstream.


- Dave


And my reply to Dave:


Hi Dave,

Thanks for your note.  I am sorry to hear that you had difficulty leaving a comment on the blog site.  I will look into why that might be.

First of all let me say that I am sorry to hear that PenTile displays are so bothersome to you.  I have no doubts that there are people like yourself who can resolve as high as 50-60 cycles/degree.  For people like yourself there is no doubt that the pattern visibility of PenTile is more apparent and can be bothersome. 

Looking at the chart you can see that normal vision is nowhere this good.  Sensitivity to luminance contrast modulation for normal human vision falls off significantly at 25 cycles/degree.  The ability to resolve chroma is far less as you can see in the 2D version of the plot to the right.

3D Plot of Human Vision System
Luminance Contrast vs Spatial Freq

Nouvoyance has never recommended the use of PenTile for 200 PPI smartphone designs.  In my opinion even a 4” WVGA at 233 PPI is stretching the application of PenTile a bit far, but even that is 24 cy/deg if viewed at 30 cm.  As you can see in the chart the cycles/degree is determined by first stating what your normal viewing distance is for a device.  For example, people rarely complain about TVs which have horribly coarse patterns, because they do not use them up close. 

Perhaps your ability to resolve high cycles per degree is not as much the issue as your ability to look at your phone from an incredibly short distance.  The ability to

Cycles/Degree by Application

accommodate at such short distances can be both a blessing an a curse.  If you can focus on a display from 10 cm could also easily explain why you see these patterns so readily.  Do you, for example, also see the pattern easily on the Galaxy SII which is an RGB stripe OLED?  It is no finer pitch for subpixels than PenTile.  If you see it, but find it less bothersome, this means that you have learned to adapt to that pattern and have not been able to do so for the PenTile pattern.  In the transition from CRTs to RGB stripe LCDs there were many people who had considerable difficulty in adapting to the visibility of the “jailbars”, but, over time, most people have benefited from visual adaption and were able to separate out the image information from the pattern.  Similarly, most people are not trouble by looking through window screens despite their intrusion on visibility. While I have never personally met anyone who could see the PenTile pattern in the Galaxy S3 at ~300PPI, I never doubted that such people like yourself existed.

There are also people who have the ability to see flicker better than most of the population.  They have a horrible time with the field sequential nature of TI based projectors.  They, too, have had to look at projectors in conference rooms that drive them nuts in a market where the technology was proliferating.

So let me give you the bad news first.  There is no technical solution for replacing PenTile in OLED smartphone displays on the horizon.  The highest pitch that has been recently demonstrated is ~260PPI which will go into the Galaxy Note II.  Beyond that, the OLED display industry must use PenTile to maintain a reasonble lifetime and brightness for the blue subpixels.  I had the occasion to chat with Professor Tang, the co-inventor of  OLED technology two weekends ago when he spoke at the 50th Anniversary of SID.  I asked him if the lifetime issue for blue OLED material was fundamental, or if there is a good solution on the horizon.  He explained to me that the energetics involved in blue quantum excitation was at just the right level to break the bonds in the OLED materials.  He doesn’t see a solution in the forseeable future.  For this reason, I predict that you will continue to see many PenTile displays in OLED phones.    Furthermore, we are now seeing critical issues with battery life for tablets, so the ability to cut power consumption in half with PenTile RGBW LCDs will soon bring more PenTile LCDs to the market, starting with WQXGA formats of ~300PPI.  Most people will be delighted, but you, no doubt, will not.

Now for the good news.  There are already LCD alternatives available at your local phone provider for smartphones usng LTPS, and perhaps soon IGZO based backplanes that will give decent performance at 300 PPI.  These may not have the color gamut or response speed of the curent AMOLEDs, but they will be less troublesome for your vision.  The other good news is that the trend for increased resolution continues.  We will be seeing displays continue to 400PPI and 450PPI before too long.  I am guessing that even your vision will not be troubled by PenTile technology when we get there and you may even appreciate the improvements to power efficiency and/or brightness that PenTile technology will bring to LCDs.

Thanks again for your feedback.




PS:  Perhaps you would be willing to share with me a specific image or test pattern that you find most objectionable on the PenTile panels you have seen.  The people in our R&D team are always looking at ways to continue to improve PenTile display performance.  We have already made a series of improvements, not all of which have made it yet into products, but sometimes knowing what customers really find to be problematic will enable us to put our efforts into more productive solutions for future designs.