Nexus screen tech - PenTile, dpi, SAMOLED

DisplayGeek said:

+1
Right now, both OLED and LCD PenTile panels use two subpixels per pixel. As resolutions increase, the number of subpixels per pixel may be reduced yet further. One such design uses 1.25 subpixels per pixel, and still meets the VESA spec for resolution. There is even a layout, that also meets the VESA spec, that is only one subpixel per pixel, dispite using five different color primaries (one of them being W)

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I have read the VESA spec cited before on the pentile blog. But a 4" 800x480 pentile AMOLED display has clear problems compared to 4" 800x480 RGB stripe display. They both meet the VESA spec, so that must mean the VESA spec has little meaning in relation to how the display appears to a user and two identical resolution displays by the VESA standard are not necessarily equally good.


Samsung made a conscious move to AMOLED+ RGB stripe with the Galaxy S II. Here we can see a Samsung rep explaining the improvement: Super AMOLED Plus - YouTube

Now with their next generation phones, they seem to have gone back to pentile matrix technology. The only conceivable reason seems to be that they can't make 3 subpixels/ pixel HD displays in a 4.3" screen. For instance they chose to not use the pentile layout for the Galaxy Tab 7.7 since the larger screen means they could use the RGB layout.

When Samsung move to the new LITI process it seems they will be making SAMOLED+ HD displays for their phones.

The question is will they again ditch the pentile layout? I think they would based on current evidence where they seem to have been forced to return to the pentile layout to made HD 300+ ppi displays possible.

So the subpixel density of the new Galaxy Nexus display is similar to the Galaxy S II. From the images I don't doubt that your algorithms are clever and the increased density over the Galaxy S pentile display helps reduce the issues, and the altered subpixel layout would deliver an improvement over the G S II.

However I really question whether the pentile 300+ ppi display is completely indistinguishable from a 300+ppi AH-IPS display. The phonearena article that you praised and several others quoted has such poor quality macro images that it's hard to tell anything.

This image suggests that there is still a difference and the patterns from the unaligned pixels will still be visible.

It does seem that pentile is a stop gap measure until Samsung's new manufacturing process comes online and then it will be ditched yet again? Or maybe pentile will still have a place since Toshiba can already produce 500ppi displays so Samsung will be playing catch up for a while at least.

This is my current understanding, feel free to correct me.

scynaz said:

Now with their next generation phones, they seem to have gone back to pentile matrix technology. The only conceivable reason seems to be that they can't make 3 subpixels/ pixel HD displays in a 4.3" screen.

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Yes, from PenTile blog:

The reality is that this is the only way to achieve 300 dpi OLEDs. When people try to compare this technology to other panels it is not possible to compare a PenTile OLED at this resolution to any other high resolution RGB stripe OLED for one reason. Such RGB stripe OLEDs do not exist . Such technology is not possible.

When people say that this is a low cost alternative, they have it entirely wrong. It is not less expensive to make and there is no high resolution alternative. We only wish it were lower cost, but so far that has not proven to be the case. Yes, a 720P OLED could be made, but only if it were one-third larger diagonal, which no doubt would most likely be more expensive. The use of PenTile technology for OLED has been to achieve high resolution for OLED, plain and simple.

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scynaz said:

However I really question whether the pentile 300+ ppi display is completely indistinguishable from a 300+ppi AH-IPS display. The phonearena article that you praised and several others quoted has such poor quality macro images that it's hard to tell anything.

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novox77 said:

On principle, I don't buy the argument that the issue goes away as you increase the resolution, even though it's a true statement.

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This is the line of argument I can't get my head around. Yes, different people have different levels of visual acuity, which has been proven with older PenTiles. It also has to do with knowing what to look for. But that acuity still has a limit set by human biology. There is a point where the underlying sub-pixels are practically meaningless, when from normal viewing distance no human eye can detect the pattern. At that point it's merely a theoretical discussion, for which I fail to see any value from a consumer point of view.

Whether that point has been achieved with Galaxy Nexus I don't know. But it isn't something you can determine by looking zoomed up photos. All I know is that there hasn't been a single hands on review yet to notice these problems.

Sandroidfan said:

Honestly at 720p resolution, this won't be issue except for someone like you staring phone at distance less than inch or using magnifier on screen to look for any artifacts. Even on the notorious Bionic screen with RGBW pentile, I couldn't see artifacts until I put it very close to eye.

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I thought i made it sufficiently clear that I am not staring at the screen at close distance and/or using a magnifier. Nor am I trying to find fault in the screen in any way. My entire point is that I have high sensitivity to the artifacts without needing to take a close look. People said the same thing about PenTile on qHD, including Nouvoyance: that the increase in pixel density would make the artifacts a non-issue. qHD on a 4.x" screen wasn't enough for me not to notice. Maybe 720p will be. But I'd rather wait for RGB stripe at 720p. No compromise. I'll pay more for that screen and take a larger hit on battery life to have the best image quality.

Speaking of power savings, the new generation of Android phones have proven to be very good at managing power. Plus, the biggest drainer of battery is radio usage, followed by CPU usage. The display is a distant third. So whatever PenTile saves on juice is not worth the sacrifice in image quality, IMO. But again, it all depends. If you think Splenda tastes exactly like sugar, then you've essentially got the best of both worlds. Which is what PenTile is for many people.

ferdasyn said:

This is the line of argument I can't get my head around. Yes, different people have different levels of visual acuity, which has been proven with older PenTiles. It also has to do with knowing what to look for. But that acuity still has a limit set by human biology. There is a point where the underlying sub-pixels are practically meaningless, when from normal viewing distance no human eye can detect the pattern. At that point it's merely a theoretical discussion, for which I fail to see any value from a consumer point of view.

Whether that point has been achieved with Galaxy Nexus I don't know. But it isn't something you can determine by looking zoomed up photos. All I know is that there hasn't been a single hands on review yet to notice these problems.

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There is definitely a threshold where 100% of the population doesn't notice any artifacts of a pixel-based display. It's easy to prove that to yourself by choosing a pixel density way beyond such a threshold, like 1 million pixels per inch, for example.

It works on a bell curve. Let's say WVGA PenTile (assuming a 4.x" screen for all future scenarios) only bothers 10% of the population... Pentile on qHD maybe affects 5%. At 720p, maybe 2%. And maybe by 1080p, the problem truly goes away.

Just keep in mind that even for a given individual, our resolving power differs depending on what we're looking at. For example, if you had a "retina" screen like that of the iPhone 4, and you created an all-white screen with a single black pixel, there's a good chance your eye can resolve that black pixel. Maybe not. The luminosity of the white might overpower the black pixel.

However, if you invert that image such that the whole screen is black and you have one white pixel, the vast majority of people are going to see it.

That's why when it comes to resolving power and perception, only considering resolution and density is not giving you the full picture. There are lots of variables at play, especially when you start dealing with motion.

I feel like my voice is getting too loud in here, so I'll step off my soapbox now. I'm simply standing up for the minority that have legitimate reason to be bothered by PenTile artifacts. But in the end, you should all observe for yourself when the opportunity arises and see if PenTile is a big deal for you or not. There's a good chance that at the densities of the Galaxy Nexus, PenTile is completely a non-issue for most people.

novox77 said:

I thought i made it sufficiently clear that I am not staring at the screen at close distance and/or using a magnifier. Nor am I trying to find fault in the screen in any way. My entire point is that I have high sensitivity to the artifacts without needing to take a close look. People said the same thing about PenTile on qHD, including Nouvoyance: that the increase in pixel density would make the artifacts a non-issue. qHD on a 4.x" screen wasn't enough for me not to notice. Maybe 720p will be. But I'd rather wait for RGB stripe at 720p. No compromise. I'll pay more for that screen and take a larger hit on battery life to have the best image quality.

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Sorry I missed the part what you said (not staring and using magnifier on screen) before. I think WVGA to qHD is not that big step up in resolution to diminish pentile issue enough. But qHD to HD (540p vs 720p) is bigger step up, so it won't be issue to most people, IMO.

novox77 said:

People said the same thing about PenTile on qHD, including Nouvoyance: that the increase in pixel density would make the artifacts a non-issue. qHD on a 4.x" screen wasn't enough for me not to notice.

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Just have to point out - Motorola uses RGBW, not RGBG like Samsung's OLEDs. They have a whole different set of.. 'attributes'

The Atrix's 4.0" 960x540 RGBW screen looks terrible to me, but I don't really have a problem with 4.0" WVGA RGBG.

scynaz said:

Now with their next generation phones, they seem to have gone back to pentile matrix technology. The only conceivable reason seems to be that they can't make 3 subpixels/ pixel HD displays in a 4.3" screen. For instance they chose to not use the pentile layout for the Galaxy Tab 7.7 since the larger screen means they could use the RGB layout.

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Awesome post, and I just wanted to expand on this. It's not the size, but the PPI. For example, their Super Amoled Plus is used on 2 of their 4.5" screens (SGS2 US variants for Sprint and T-Mobile). Their 720p screens (Galaxy Nexus, SGS2 LTE HD) are PenTile due to the PPI, as you stated.

Can't really count the RAZR, as Samsung just isn't sourced SA+ outside of Samsung right now.

As long as it looks better than the bionic I don't care what kind it has.

I just got to play with a Samsung Focus. It has the same screen as the Nexus S (4.0" 800x480 samoled) that I played with a year ago. And I have to say that it was not as bad as I remember. It is still not a display that I would want to read a lot of books on. But with the pixel density going up substantially, I have renewed hope that PenTile will be a non issue for me.

ferdasyn said:

But that acuity still has a limit set by human biology.

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No, there are two factors.

1) Visual acuity is not a function of ppi, there isn't a set threshold. For example, with text content involving complex character shapes, you are far more likely to perceive a difference. Look at the japanese text used as an example for the 498ppi screen:

Toshiba shows off 6-inch tablet display with 498ppi resolution -- Engadget

That's the kind of content where you can tell the difference beyond 300ppi. For example, you open a webpage on your phone. And due to the small screen, some of the text appears very small and unreadable and you would think you can never read text that small. Until you see the same page on a higher ppi screen and even that tiny text is readable. So some of the difference you will only know if you actually see a better screen alongside, otherwise you would think your phone screen is fine.

But when you do compare to a better screen, you can read text so small you thought it was unreadable, you see a level of detail in photos you thought you would never see on a phone, you see real curves and diagonal lines instead of stairs. For me I can't understand why anyone would not want the best screen possible since it's what you look at every time you use your device. We spend so much time and effort on doctors and optometrists and laser surgery to improve our vision, so considering how much time we spend looking at computer screens of various sizes these days, forsome of us it is unfathomable that people can actually be satisfied with a 800x480 pentile screen and say 'I can't see what the problem is, my Galaxy S screen is perfect'.

We have become used to artifacts like the stair pattern in diagonal lines, blocky circle borders due to the way such screens render curves etc. These are things most people don't notice, they don't realize that you don't see these things in high quality printouts on paper, so ideally your screen shouldn't show them either.

Compare a high quality colour magazine or book printout to your mobile screen and see if they are equivalent. Then you will get an idea of the kind of quality we are talking about.

Those of us who have been craving high quality screens on desktops for years, were disappointed that we went backwards with the arrival of LCD screens, and are amazed how much any LCD screen that is not utter crap costs are delighted to see the adoption of high resolution non 6 bit TN LCD screens in mobile devices has been wonderful.


2) The other thing is, the 300+ ppi for pentile screens is an approximation, it won't always behave like a 300+ ppi screen, depending on the content being displayed. So the underlying subpixels are important because pentile screens only have two subpixels per pixel whereas RGB screens have three.

So at the fundamental level, RGB screens at the same resolution are 50% denser in terms of the 'dots' or pixels they are composed of. At around 215ppi this difference was visible in the screen door patterns, coloured and blurred text borders, vector graphics like maps etc.
Nuovyance claim that at 300+ ppi this difference isn't visible. I am impressed by the clever algorithms used but I am not convinced that if you put a 1280x720 RGB sc(2.765 million subpixels) next to a 1280x720 pentile screen (1.843 million subpixels) there will be no perceptible difference.

scynaz said:

No, there are two factors.

1) Visual acuity is not a function of ppi, there isn't a set threshold. For example, with text content involving complex character shapes, you are far more likely to perceive a difference. Look at the japanese text used as an example for the 498ppi screen:

Toshiba shows off 6-inch tablet display with 498ppi resolution -- Engadget

That's the kind of content where you can tell the difference beyond 300ppi.

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I didn't mean to imply PPI doesn't matter or that 300ppi is the best human eye can see. Although technically I'd bet you couldn't tell apart 1500ppi and 1000ppi displays .

scynaz said:

Nuovyance claim that at 300+ ppi this difference isn't visible. I am impressed by the clever algorithms used but I am not convinced that if you put a 1280x720 RGB sc(2.765 million subpixels) next to a 1280x720 pentile screen (1.843 million subpixels) there will be no perceptible difference.

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I guess i'm just a bit more optimistic based on what we know so far. We'll just have to wait and see.

Sorry for the thread necro but this seems to be a very good thread to ask.

Is the pentile matrix causing a faint but visible horizontal/vertical lines when displaying certain colors especially on shades of grey and white?