DisplayMate’s Twitter on PenTile Resolution

We came across a few tweets from Ray Soniera of DisplayMate yesterday where he made several comments about PenTile. And we wanted to address that.

When Ray Soniera says that PenTile has half of the R, G, & B subpixels as an RGB stripe he is correct. What Dr. Soneira is doing is counting only the R, the G, and the B subpixels… ignoring the W… and ignoring subpixel rendering.

First, imagine that we had a purely monochromatic B&W panel. Do we say it has no resolution because it has no color? (Seriously?) In the PenTile case, each white subpixel would be half of the B&W resolution, and the combined RGB triplet would be the other half. So, it looks like a full resolution B&W display. This is good, because the human eye can see tremendous detail in black & white… But not so well in color!

The human vision system can only see a very low resolution in pure color. In pure red to green color our eyes see only one tenth as well as it can in pure black & white. What we see in everyday life is a combination of pure color and pure black & white, so it seems very richly detailed.

So, having high resolution in black & white, but only half the resolution in pure color, is still more than we need. Why waste putting detail into color which we can’t see?

So, Dr. Soneira is right, we do have only half the number of RGB triplets… but that is a good thing.

3 comments on “DisplayMate’s Twitter on PenTile Resolution

  1. Eyes don’t lie, and RGB-based displays are always clearer than any pentile-based display.

    Isn’t the whole purpose of pentile is to allow screen manufacturers to inflate the resolution by using the same amount of subpixels (a rather convenient and cheap way to cut costs)?

    • Your assertion that an RGB-based display is always clearer is a broad statement that I can’t agree with. For other entries in this blog I have shown that they human vision system sees contrast modulation ratio to discern resolution. So if clearer is defined by modulation ratio as the experts say it is, then the eyes see PenTile as equivalent in clarity to RGB stripe. That said, I would agree that PenTile at the lower end of resolution will have a certain graininess that you may not see in RGB stripe. Does that make it look less clear? On the other hand, a PenTile RGBW display will be brighter than the equivalent RGB stripe display running at the same power. Does that make the PenTile clearer? As for OLEDs you will hard pressed to find any OLED of wVGA format in 4” diagonal or less, so when you say the RGB stripe is clearer, what display are you comparing it to?

      Let me touch on one other phenomenon that is known to vision experts. Eyes do lie. Over time the human vision system has the capability of accommodating certain periodic features in displays. Back in the day we all used raster based CRTs we got used to looking at a raster, horizontal scan lines, but, over time, we all began to subtract that raster pattern out from what we were seeing so that raster pattern largely vanished from view. Similarly when we started using RGB stripe displays may people were painfully aware of the vertical stripe pattern and it bothered them. In time we became desensitized. For PenTile displays the organization is on the diagonal and, for some of us, that is not something we are used to seeing and it too will bother certain people. But, in time, that too will be accommodated if there are enough PenTile displays to look at.

      So let’s address the issue of PenTile just being “a rather convenient way to cut costs.” That simply isn’t so. The number of processing steps in making a PenTile display are pretty much the same as for an RGB stripe. For a single chip driver the gate count is about the same where reduced columns are nearly matched by increased logic for algorithms. The value proposition for PenTile OLED is to enable manufacturing at very high resolution without sacrificing brightness. It makes the fabrication practical. As for PenTile RGBW LCDs, it is not a matter of saving cost, but a matter of achieving a high resolution without the increased power of reduced aperture ratio of the equivalent RGB stripe. A 40% power savings is very significant for a mobile product design and enables a manufacturer to maintain or increase brightness that ultimately improves display visibility. In addition, the fewer, larger, more square-ish shaped subpixels, mean less border area in the pixels that cause light leakage in the dark levels. This means darker blacks. Combined with brighter whites, this improves contrast.

      • Power savings and pretty colors and contrast is none of my concern. Most of my activity of my phones involve a lot of text (web browser, reading books, writing, etc.), so that’s why I’m seeing a lot of faults with pentile arrangements.

        I used to use a Motorola Milestone with its excellent 854×480 3.7″ screen to do the things I mentioned. Since that phone died on me, I had someone to lend me his HTC Desire (800×480 3.7″ pentile OLED). Text look nowhere as good as on the motorola, as they look rather fuzzy and have a weird colored outline on them.

        The only solution to the fuzzy text was to turn on the green render effect via CyanogenMod’s settings. Since the green subpixel is the only one that isn’t on a diagonal arrangement like the blue and red, the text now finally appear as clear as it should be. However, what’s the point of a nicely sized screen when it’s just green?

        I admit I haven’t seen the RGBW arrangement in front of me yet to judge it, but looking at the subpixel arrangement, I’m not keeping my hopes up.

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