by Jin Kim
In Nexus One PenTile Matrix OLED Display (January, 20, 2010), I originally argued that because of the different sub-pixel structure used in the Nexus One the claimed 800×480 pixel format was not accurate. A simple calculation yielded more along the lines of 533×480 because of the 2×2 sub-pixel structure instead of the typical 3×1 found in most LCDs. Soon after the blog was published I was contacted by Joel Pollack, Sr. VP of Strategic Sales and Marketing at Nouvoyance and subsequently had a meeting involving Joel, Candice Brown Elliott (CEO) and Tony Botzas (Director of System Apps and Engineering) on February 3.
After some consideration, I updated the post by stating:
I came out of the 2 1/2-hour meeting impressed and convinced that the 3.7-inch PenTile Matrix OLED display used in the Nexus One does indeed have a resolution that is equivalent to a 3.7-inch TFT LCD with a 800×480 pixel format using red, green, blue 3×1 striped sub-pixels.
I argued in Display Showdown Part 1a: Nexus One that mere hardware specs cannot determine resolution. The Video Electronics Standards Association (VESA) Display Metrology Committee has a definition for resolution in Section 303-7 of Flat Panel Display Measurements Standard Version 2.0: “… the number of alternate black and white lines that can be displayed with a stated minimum contrast modulation.” I also added that the requirement that these black and white lines not only be displayed but viewed by the human visual system and concluded:
So, let’s move from vision back to hardware specification: does the Nexus One’s PenTile Matrix OLED display have a resolution equivalent to a 800xRGBx480? The answer is: yes, it does.
I thought the debate ended there, but Luke Hutchison in Secrets of the Nexus One’s screen: science, color and hacks on Ars Technica showed the resolution of the Nexus One screen is not as high as claimed. Luke claims that VESA’s resolution measurement methodology in Section 303-7 in the FPDM Standard Version 2.0 is “insufficient to test the display’s true resolution, at least for the way the PenTile display is configured on the Nexus One.” Luke then supported his argument by looking at diagonal white and black lines, which “exhibit significant color banding…” He then concluded:
My main point about screen resolution in this article is that both the Nexus One and the Droid screen were specced at almost the same resolution so they should look the same (I think this is a fair assumption)—and they simply don’t.
In the most recent High Resolution newsletter (March 2010) published by Veritas et Visus, Luke continues his assertion that the Nexus One’s PenTile Matrix OLED display is not as high as claimed in Resolution and false color images on the Nexus One:
PenTile’s creater, Nouvoyance (formerly Clairvoyante), claims that the PenTile’s resolution is exactly comparable to an LCD display of the same number of physical pixels. It is completely impossible for this claim to be correct, given that there are fewer total subpixel elements on the PenTile screen than on an RGB-striped LCD screen of the same number of physical pixels.
Luke pointed to effective pixel size, subpixel positioning, and offered links to full-resolution sample black and white stippled images that induce color artifacts on the Nexus One display. In the same High Resolution newsletter Candice H. Brown Elliott and Joel Pollack responded in PenTile OLED resolution to Luke’s original post on Ars Technica:
In Mr. Hutchison’s article he tries to examine the functionality of the layout independently from the algorithms. That is not possible, as the algorithms are an integral part of how PenTile technology works.
I think the confusion lies in not accurately creating the boundaries of discussion. As I have mentioned already in Display Showdown Part 1a: Nexus One there is a difference between hardware specifications and vision. The PenTile Matrix OLED display was developed and tuned for the way the human visual system works. Our vision system is not simply the sum of the biological capabilities within the eye but works in conjunction with our brain. That sounds simple but it is really quite complex. I don’t pretend to fully know how the brain works when it comes to vision, but I was intrigued to find out that most of what we see are things that we expect to see. Only in a few instances does our brain react to what we see; most of the time our visual system is confirming what the brain is already expecting, which points to a strong correlation of vision to our expectations, a function of the brain. So in agreement with Candice and Joel, I must say the PenTile Matrix OLED display cannot be examined without the underlying algorithms that make it work.
Candice and Joel goes to great lengths to provide ample analyses, some of which I will honestly admit the author does not fully understand. In regards to color banding on diagonal black and white lines:
… the PenTile OLED is capable of reconstructing black and white line pairs, with at least 50% Michelson Contrast, out to the full Fourier space of the input conventional image.
Close-up text images are then shown as examples for the reader to examine in response to Luke’s claim that text were fuzzy. From my point of view, reading the High Resolution newsletter on a 17-inch MacBook Pro at 1920×1200, the close-up text images look quite clear without fuzziness. And in response to color artifacts on stippled images Candice and Joel point to the cause:
… this artifact is caused by a very slight color error that occurs at the boundaries between two different filters in our locally adaptive SPR [Subpixel Rendering] algorithm. Mr. Hutchinson has literally found a “hack” in which he forces the SPR engine to switch between filter sets in a highly structured manner, forcing a negligible, but real color error, to be repeated over and over again until that error is visible.
It wasn’t stated in the article but I am sure Nouvoyance, Samsung, Google, and HTC will make sure the next version of their smartphone (Nexus Two?) will sport a much smarter display allaying fears or doubts that the PenTile Matrix OLED display technology is up to the task of delivering a viewing experience that meets consumer expectations for a “800×480″ display. Even then, I’m still a sucker for high-end LCDs… iPhone HD anyone?