Comparing RGB Stripe Text to PenTile RGBW Text

My post showing the comparison of fonts with RGB stripe to PenTile RGBW LCD and PenTile RGBG OLED still left a few people confused, so I am going to illustrate this one more way.  Previously, I compared the results for the same number of columns.  Since PenTile RGBW can represent the amount of information in one-third fewer columns my prior blog showed the PenTile RGBW with one-third more font information.

This time I am comparing the same amount of font information, where PenTile RGBW used one third fewer columns, but have stretched the columns horizontally to match the horizontal space of the RGB stripe, just as it is done in products today.  This allows the comparison of equivalent size single stroke Arial fonts between RGB stripe and PenTile RGBW.

RGB Stripe (Top) - PenTile RGBW (bottom) As Rendered (left) - Blurred to Simulate Viewing Distance (right)

 

Perhaps you may wonder why there are some color subpixels turned on in places such as the vertical stroke of the “D”.  The reason is that if viewed at the normal distance, and if these subpixels were turned off, such a rendering would cause a color error to the white that was adjacent to the black line.  Rendering this as has been done prevents such color error at the edge of this font.  And, yes the PenTile RGBW should look brighter than the RGB stripe since this is a representation of the relative light transmission of PenTile RGBW vs RGB Stripe

The only problem is that this magnification is not at all how the human vision system sees this.  At the viewing distance for which this is design, that which you see will be blurred to hide the subpixels.  Move away from your screen until the subpixels on the lft hand images  are not apparent and you will see this as finished product would appear.

Moving away from the display has also be emulated by taking the images on the left and blurring it in Photoshop HSL space to create the images on the right that more accurately represent how the vision system sees these font renderings.

Perhaps you may wonder why there are some color subpixels turned on in places such as the vertical stroke of the “D”.  The reason is that if viewed at the normal distance, and if these subpixels were turned off, such a rendering would cause a color error to the white that was adjacent to the black line.  Rendering this as has been done prevents such color error at the edge of this font.

The only problem is that this magnification is not at all how the human vision system sees this.  At the viewing distance for which this is design, that which you see will be blurred to hide the subpixels.  Move away from your screen until the subpixels are not apparent and you will see this as finished product would appear.

Moving away from the display has also be emulated by taking the image on the left and blurring it in Photoshop HSL space to create the images on the right that more accurately represent how the vision system sees these font renderings.

5 comments on “Comparing RGB Stripe Text to PenTile RGBW Text

  1. oh, if I wanted a brighter panel, I’d probably use a more powerful backlight, and a bigger battery

    NOT. CUT. THE. AMOUNT. OF. PIXELS. IN. HALF. (and do my best to approximate what’s left of it with all sorts of algorithms, nevertheless half is still half)

    do not want

    • I am not here to say that everyone should like PenTile. Surely if you do not see the merit in cutting power in half and preserving brightness, there is little I can say.

      At the same time perhaps you should try to find products that do not use JPEG, MPEG or MP3 compression, even if you need a larger hard drive or fatter pipes to get your data.

      It was clearly demonstrated here that we do not get rid of pixels, only subpixels. If we had we could not render so perfectly the finest single stroke black and white text. Your issue is with pattern visibility, which PenTile has to a larger extent than RGB stripe. Likewise all compression formats, such as MPEG have artifacts that some people are more sensitive to than others.

      There are engineering considerations for the design of every product. As resolution climbs to higher and higher levels PenTile will be a choice that every manufacturer will consider in comparison to having a thick and heavy or short life battery. As they do there will be those who insist on legacy technology.

      • I have a Motorola Photon, and I have noticed that pattern visibility is definitely an issue. There is a very perceptible 45 degree “screen door”-type effect going on. However, it’s not a big deal to me, especially if vastly increases battery life. I run my screen at minimum brightness, which reduces pattern visibility and maximizes battery life, and even at minimum brightness, the screen is still bright enough to read in sunlight.

        I think the RGBW screen is a great technology, which will only get better in the future.

        Is it possible to combine RGBW with AMOLED? It would be nice to get the deep blues of AMOLED and the battery savings of RGBW

        • Thanks for the feedback on your Motorola Photon.

          This 45-degree stripe was pointed out to me by another Photon owner two weeks ago, so a couple of us from Nouvoyance went to have a closer look at the nearest Sprint store. At first we had trouble seeing this and had to look at just right kind of gray image, mostly in motion, to pick this up. I am wondering if this is seen to the same extent in every phone. After looking at this closely, we are quite sure that this is not a PenTile effect. There is nothing about our PenTile layout or algorithms that favors one diagonal over the other. The effect has not been seen in any other PenTile display and we cannot reproduce it here in our lab. While I have some ideas what can cause this, I am not yet certain of a root cause. I did provide some feedback to some people about this and hope to get a Photon provided to us so we can study it more carefully here where we are best equipped.

          Thanks for your positive feedback on PenTile RGBW. We know, based upon resolution trends and demands for high power processors, that you will be seeing much more of this in months and years ahead. Those that appreciate PenTile RGBW are far less vocal than those who do not.

          As for your OLED question, it is, in principle, possible to have an RGBW OLED, but the primary technology in the market is of the emissive type. There is no white emissive OLEDs yet that surpasses the luminous efficiency of R, G, B OLED emitters. OLEDs today save power by virtue of only lighting up where they want information. At the time time, if your need is to light up an entire screen as white, they are still far less efficient than LCDs, especially when compared to PenTile RGBW LCDs. PenTile RGBG technology today is in every handheld product with OLED displays of WVGA resolution of less than 4.3-inch diagonal and also in a few high resolution VGA displays. Our value proposition for emissive OLED has been to enable high resolution. At very high resolution the current density is increased to the point that it becomes impossible to maintain sufficient brightness for the target life of the product. Only when the WVGA panels went to some models with 4.3-inch and larger did Samsung SMD offer OLEDs with RGB stripe. Nouvoyance never recommends use of PenTile for such low DPI as 4.3-inch WVGA.

          As for deep blue, this is also possible with LCD. Expanding color gamut is possible, but generally at the expense of light transmission and efficiency. In time RGB LEDs will become more affordable and then such designs with better color filters will allows blues that will impress even the OLED fans.

  2. I understand that you put the highest value in the quality of your imaging over other factors in your phone, especially when the content merits those measures. You have acknowledged that this is not everyone’s priority, and I can fully understand that this is yours. I maintain that that even h.264 has artifacts and this is not apples to oranges with what we are doing.

    So allow me to clarify the meaning of pixels and how we use them. Pixels are really only points on the screen plus a reconstruction filter (not my definition, but an industry definition going back at least to the 1970s well before PenTile technology). The reconstruction filter is different for RGB stripe, CRTs, and PenTile RGBW LCDs. When you look at a PenTile screen the center of a pixel can be an RGB or a W. We do our best to keep the center of the luminance to that position, but we address the chrominance of that pixel with as many as 13 surrounding subpixels to insure that they correct color is seen at that pixel point.

    I can imagine that you may say that this is not good enough as we do not have the same chrominance resolution, but in reality the human vision system does not resolve chrominance nearly so well as luminance. We can only resolve 8 cycle/degree of human vision of chrominance detail along the red/green line and 4 cycles/degree along the blue/ yellow line. As a consequence, not having a little square with a red, green and blue pixel generally doesn’t matter, especially for bandwidth- limited images such as pictures. One more thing—if you think that your best RGB stripe display (e.g iPhone 4) has perfect chromatic resolution, try this exercise. Write a pattern of blue and yellow lines immediately adjacent to each other and tell me what you see. You will see fine black and white lines http://pentileblog.com/?p=656.

    So you would agree that black and white single stroke fonts are fine, but you said such a claim is “sneaky” as we can do this better as all subpixels are on. The reason I cite black and white text is that is what is referenced in the only industry spec by VESA. They chose white since it presents many challenges such as chromatic aliasing, so not all subpixel rendering can do black and white text as well as PenTile. As for the fully saturated corner cases of green on black or red on black, it is a limitation that can lead to frail looking single stroke diagonal lines in those very small fonts, and is one of the reasons why we only recommend PenTile for high dpi.

    Resolution is steadily climbing and is now in the 300 dpi range. As good as your vision may be, you will very likely not see pattern visibility for frail text for single stroke 6 point fonts on a 300 dpi PenTile RGBW panel. It is at that level where the power advantage also more strongly favors PenTile designs. IMHO we are not so far from 300 dpi or even 400 dpi displays for these types of applications. This is not insanely high. Some of the youngest and sharpest eyes who have looked at our new 10.1” WQXGA (2560×1600) PenTile RGBW could not see any pattern visibility of frail text to the 6 pt level. At this 300 dpi level 6 pt fonts are mighty small.

    As for better patterns, yes we have those. We also have methodology for combining PenTile technology with field sequential technology for high color gamut, and perfect text of any color. The problem is that those patterns and technologies are not yet compatible with state of the art display fabrication technology. Perhaps soon the fabrication will catch up and these artifacts will be reduced even further, but like any new technology we take it one step at a time and do not expect that we will please everyone at every step along the way.

    It is not my goal to convince you to buy a Milestone 3. Personally, I don’t care what you buy and would prefer that you buy whatever makes you happy. I would only ask you to remember that our OEM customers have more customers who have voiced concerns about battery life in their new, high performance phones than they do with these artifacts of PenTile screens.

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