Nexus screen tech - PenTile, dpi, SAMOLED

[BlueBiker]

Smaller the subpixel size the shorter the life of the display for a given brightness. So these tiny HD displays will be pentile.

Wait, what? Wouldn't that mean iPhone 4/4S would have awful screen longevity?

 

[Loriolus]

Guys Guys have you ever seen or had Samsung S8000 Jet with supposed 301 ppi? The screen size is 3.1 inches and 480 by 800 pixels Amoled screen. Well I've had the phone and the second I turned the screen on I noticed the pentile screen. 4.65 inches is a lot bigger than 3.1, and even at 720P res I don't think that it's gonna hide that ugly pentile look.

 

[jasaero]

The possibilities are endless

No doubt. Stuff like storage facilities could go totally unstaffed and be built without any office at all allowing for a few more storage units on a property. And thats just something that came to mind immediately/randomly when I saw the "endless" point.

Guys Guys have you ever seen or had Samsung S8000 Jet with supposed 301 ppi? The screen size is 3.1 inches and 480 by 800 pixels Amoled screen. Well I've had the phone and the second I turned the screen on I noticed the pentile screen. 4.65 inches is a lot bigger than 3.1, and even at 720P res I don't think that it's gonna hide that ugly pentile look.

Never seen one of those, but they are somewhat old. What did you have prior to it that was a better screen?? Surprised you would have something before it that was sharper??

 

[sjael]

Guys Guys have you ever seen or had Samsung S8000 Jet with supposed 301 ppi? The screen size is 3.1 inches and 480 by 800 pixels Amoled screen. Well I've had the phone and the second I turned the screen on I noticed the pentile screen. 4.65 inches is a lot bigger than 3.1, and even at 720P res I don't think that it's gonna hide that ugly pentile look.

In addition to the PenTile thing being a very subjective thing, Samsung have also changed their PenTile arrangement. In older screens the Red/Blue sub-pixels were 2:1 the size of the Green sub-pixels. In these new ones they appear to be 1:1 which will very much change the characteristics of the display.

Wait and see.

 

[jasaero]

In addition to the PenTile thing being a very subjective thing, Samsung have also changed their PenTile arrangement. In older screens the Red/Blue sub-pixels were 2:1 the size of the Green sub-pixels. In these new ones they appear to be 1:1 which will very much change the characteristics of the display.

Wait and see.

Did not know this, but still confused someone woulda had a phone before that one that they liked the screen on better?? Unless he got that one used a while after release.

 

[Loriolus]

In addition to the PenTile thing being a very subjective thing, Samsung have also changed their PenTile arrangement. In older screens the Red/Blue sub-pixels were 2:1 the size of the Green sub-pixels. In these new ones they appear to be 1:1 which will very much change the characteristics of the display.

Wait and see.

Didn't know this either. Thanks. That would make a big difference.

 

[BlueBiker]

Samsung have also changed their PenTile arrangement. In older screens the Red/Blue sub-pixels were 2:1 the size of the Green sub-pixels. In these new ones they appear to be 1:1 which will very much change the characteristics of the display.

Yeah, I bet it will. Does that mean they miscalculated the eye's sensitivity to green? I mean, wasn't that the whole purpose of RGBG?

 

[sjael]

Yeah, I bet it will. Does that mean they miscalculated the eye's sensitivity to green? I mean, wasn't that the whole purpose of RGBG?

I'm not an eye scientist (eyeintist?) so I can't give you a real technical answer for that, but as I understand it, the eye isn't exactly more sensitive to green, but it sees detail in green better than in blue and red. That's the reason they chose to double green pixels - technically any image that uses some amount of green should maintain a comparable level of perceivable detail on an RG/BG display to an RGB one. I'm assuming they went with 2:1 so that for every two pixels (PenTile doesn't render to exact pixels, it has a virtual resolution) there is the same area of red, green and blue.

The biggest issue comes with sharp contrast areas - because PenTile screens use sub-pixel-rendering, they encounter instances where due to the 2:1 sub-pixel ratios, a vertical black/white line will look fuzzy because the subpixels aren't all the same width along that line, and interpolation of colors to achieve the virtual resolution serves to exacerbate the issue. That means a 1:1 sub-pixel layout won't resolve blurry edges, but if I'm right it should be a lot better.

Like I said, this is almost all conjecture on my part, so take it with a grain of salt.

 

[jasaero]

Yeah, I bet it will. Does that mean they miscalculated the eye's sensitivity to green? I mean, wasn't that the whole purpose of RGBG?

My guess is it was more related to getting good brightness that they used huge RB pixels. Think there are greens on every pixel as our eyes make out fidelity mostly with green colors if I am not mistaken and you can kinda use some trickery with the red and blue on only every other pixel.

And the newer 1:1 are probably due to improvements in the actual subpixel brightness capability.

I am guessing as much as sjael, but that would be my guesses.

 

[BlueBiker]

The biggest issue comes with sharp contrast areas - because PenTile screens use sub-pixel-rendering, they encounter instances where due to the 2:1 sub-pixel ratios, a vertical black/white line will look fuzzy because the subpixels aren't all the same width along that line, and interpolation of colors to achieve the virtual resolution serves to exacerbate the issue. That means a 1:1 sub-pixel layout won't resolve blurry edges, but if I'm right it should be a lot better.

I'd think that doubling the green would make jaggies even worse, as the red and blue subpixels will be even further from each other, but I'm probably not understanding it right. We need new RGBG pictures!

I guess I was thinking of RGBW for power savings, and I was under the impression that RGBW gave a sharper looking display with typical text presentations.

 

[BlueBiker]

And the newer 1:1 are probably due to improvements in the actual subpixel brightness capability.

You may be right, but it seems they might as well have redesigned themselves back to straight RGB then.

Anyway, I'm glad the two of you with actual display tech background are here to explain the intent behind the designs.

 

[jasaero]

You may be right, but it seems they might as well have redesigned themselves back to straight RGB then.

Anyway, I'm glad the two of you with actual display tech background are here to explain the intent behind the designs.

Well RGB is actually RGBRGB in the RGBG nomenclature sorta. PenTile only has two pixels per subpixel in RGBG so the subpixels end up bigger for same resolution and size display allowing them to be brighter without blowing out. As state earlier the 7.7" Tab will have an HD AMOLED display with RGB stripe as that one is big enough to allow it. And really probably all of them might work with RGB if all you expected outta the display was a year or so before the blue color started to get way to weak.

And your confusion about why there is green in every pixel is something only someone with lots of knowledge of how our eyes receive and process what we see works. I think the best way I can try to guess it is that we kinda see the contrast and edges and such of stuff with the green color, while the reds and blues are added somehow onto this kinda green/black monochrome image if you will. So basically the sharper that green/black monochome image the more our brain will tend to see the overall image as sharp. And as humans go this all probably varies a good bit with genetics as you get stuff like color blindness that totally messes color up all together.

 

[sjael]

I'd think that doubling the green would make jaggies even worse, as the red and blue subpixels will be even further from each other, but I'm probably not understanding it right. We need new RGBG pictures!

There are two things to consider here. You create colors on a display like this by turn off/down certain sub-pixels. To create a solid black line, you turn off all the sub-pixels in an RGB stripe. In a PenTile display, however, you don't turn whole pixels off because the pixels don't have real physical coordinates.

Combined with the fact that, say, next to each other RGBG pixels still appear white (and not some super green white,) there will be instances where you end up making a black line by turning individual sub-pixels off. Where a hi-red, hi-green, low-blue color meets black, you will end up with something like (X means off/black) this:
XGRX
RGXX
XGRX
RGXX
Which results in a fuzzy edge.

If you then take a 2:1 ratio, it would look something like this:
XXGRRX
RRGXXX
XXGRRX
RRGXXX
Which makes the edge look even worse.

Of course there's a lot of 'magic' that goes into blending pixels together, but you get the basic idea.

I guess I was thinking of RGBW for power savings, and I was under the impression that RGBW gave a sharper looking display with typical text presentations.

RGBW actually gives the power savings. Because the white pixel doesn't affect colors, it effectively increases your brightness by 25% at the same backlight power. Unfortunately it also increases the distance between colored sub-pixels, making blending less effective, and thus harming color reproduction.

RGBG gives more accurate colors though.

 

[BlueBiker]

There are two things to consider here. You create colors on a display like this by turn off/down certain sub-pixels. To create a solid black line, you turn off all the sub-pixels in an RGB stripe. In a PenTile display, however, you don't turn whole pixels off because the pixels don't have real physical coordinates.

Combined with the fact that, say, next to each other RGBG pixels still appear white (and not some super green white,) there will be instances where you end up making a black line by turning individual sub-pixels off. Where a hi-red, hi-green, low-blue color meets black, you will end up with something like (X means off/black) this:
XGRX
RGXX
XGRX
RGXX
Which results in a fuzzy edge.

If you then take a 2:1 ratio, it would look something like this:
XXGRRX
RRGXXX
XXGRRX
RRGXXX
Which makes the edge look even worse.

Of course there's a lot of 'magic' that goes into blending pixels together, but you get the basic idea.

Excellent examples, thx! I gather the 2:1 vertical lines would've been a lot smoother if they were aligned over a red/blue column.

Where does the subpixel rendering happen? I know w/ClearType the CPU/GPU is pre-calculating the subpixels as it writes RGB values to graphics buffers that get sent out to the monitor. Do PenTile panels take vanilla RGB signals and do their own rendering in hardware? Or is there some sort of assist on the CPU/GPU?

 

[sjael]

Excellent examples, thx! I gather the 2:1 vertical lines would've been a lot smoother if they were aligned over a red/blue column.

Where does the subpixel rendering happen? I know w/ClearType the CPU/GPU is pre-calculating the subpixels as it writes RGB values to graphics buffers that get sent out to the monitor. Do PenTile panels take vanilla RGB signals and do their own rendering in hardware? Or is there some sort of assist on the CPU/GPU?

To the first part of your post, yes. Take this image for example:

The green edges of the lighter color form a hard edge against the black of the icon, but imagine there are no active blue sub-pixels, you're left with a jagged red edge that appears blurry when viewed from a normal distance. Hell, even with them on, the blue sub-pixels appear to blend into the black anyway.

To the second part, as far as I'm aware, PenTile screens have some form of hardware processing that is interposed between the GPU and the display itself. I don't know any specifics though.

 

[EarlyMon]

OK. Power savings with PenTile - no.

Consider two screens at 720p, same size. Put up a solid red image on both. The rgb one will have 1/3 of its subpixels lit, the PenTile one will have only 1/4.

The only way for them to appear the same would be if the PenTile one increased brightness (increased power consumption) to compensate.

When I questioned the CEO and lead developer of the company that makes PenTile, she confirmed that, indeed, PenTile has a form of dynamic brightness control built in that is constantly making that adjustment.

Some color combinations will save power, others will use more, and in the end, it's a wash.

That conversation took place in our Photon forum, I'll provide a link for those who need to hear her say it - or think of my example and let common sense guide you: no power savings.

I know what their website says, its a marketing claim, we discussed that as well.

They even have their own trade name for their dynamic brightness scheme, making it sound more magical, because if you think about color combinations in detail, it's quickly apparent that a whole lot of brightness processing is going on there to make it work.

As for rgbw vs. rgbg and subpixel sizes, that's not magic either. The odd sized pixel scheme comes from differences in light output per unit area for different chemical formulations used to produce different colored light. Discussion of that is avoided because they're concealing industrial secrets on the matter.

You want to like PenTile, fine, great, but there's no such thing as a free lunch. PenTile is simply a form of tech, not Kool-Aide, so don't drink it.

Everyone sees differently, trust your eyes, buy what works for you.

Pretty much you won't care about resolution or dot pitch on this class of screen. A percentage will, because a percentage has an inordinate sensitivity to that, but it's not 100% - that's an Apple myth.

Remember - retinal display resolution chosen by doubling iPhone 3gs in each direction, to make graphics software updates easier, and then given the big marketing pitch.

Common sense explains the physics here quite easily.

Take your phone at night, have someone walk down the block and point it at you.

Guess what the effective resolution will be? Yep - 1 pixel, you'll see it or not. You will see zero detail at distance.

What does that tell you? That individual pixels integrating into a cohesive image isn't just dots per inch - it's that plus the distance from your face.

And if this is your first big phone, believe me - you won't hold it as close to your face as a 3.5 iPhone.

Retinal display dot pitch importance - more Kool-Aide.

If you are qualified to buy a color TV or computer monitor by looking at a few, you're qualified to pick out a good phone display without ever hearing the words PenTile or retinal again.

Seriously.

Hope this helps.

PS - I don't like credential-based arguments but some do. My profile page lists mine for those that care about that sort of thing. I prefer common sense explanations of science and engineering, that's just me.

Remember - TANSTAAFL. There ain't no such thing as a free lunch, and this is all just tech.

Way fun tech to be sure! But just tech.

 

[BlueBiker]

The green edges of the lighter color form a hard edge against the black of the icon, but imagine there are no active blue sub-pixels, you're left with a jagged red edge that appears blurry when viewed from a normal distance. Hell, even with them on, the blue sub-pixels appear to blend into the black anyway.

Okay I get it. And with twice as many half-width greens there's twice the opportunity for clean edges.

Found the ars technica article where that came from. The author takes a dim view overall, estimating that a claimed 800x480 PenTile effectively carries the RGB color information of only about 653x392. Using the same method (multiplying by the sqrt of 2/3), the Galaxy Nexus' HD PenTile display is equivalent to an RGB resolution of 1045x588, which is better than both WVGA and qHD. He also noted some bizarre color artifacts.

To the second part, as far as I'm aware, PenTile screens have some form of hardware processing that is interposed between the GPU and the display itself. I don't know any specifics though.

The article said that the panel "uses a series of local filter operations to convert the underlying image into display intensities, including convolution, thresholding, color curve adjustment, and postprocessing with locally-adaptive filters" but doesn't mention what happens on the host side.

 

[BrknKing]

Pretty much you won't care about resolution or dot pitch on this class of screen. A percentage will, because a percentage has an inordinate sensitivity to that, but it's not 100% - that's an Apple myth.

I must be among the inordinately sensitive to this technology, as I can't look at a solid color or any sort of motion on these screens without seeing the effects of the PenTile. I guess it's not a deal breaker, but it is very noticeable and distracting for me. And I am a bit disappointed that I still see it in BruceWayne's video..assuming it will be a similar screen in the Nexus.

 

[sjael]

Found the ars technica article where that came from. The author takes a dim view overall, estimating that a claimed 800x480 PenTile effectively carries the RGB color information of only about 653x392. Using the same method (multiplying by the sqrt of 2/3), the Galaxy Nexus' HD PenTile display is equivalent to an RGB resolution of 1045x588, which is better than both WVGA and qHD. He also noted some bizarre color artifacts.

This is something a lot of journalists like to claim because it's sensational. In the real world though, pixels are defined as pretty much the number of vertical and horizontal alternating black/white stripes that a display can produce while maintaining a certain contrast between each. These PenTile screens actually are their advertised resolution. They just use a different sub-pixel layout, that unfortunately some people are especially sensitive to, and tend to get a tad fuzzy on sharp, hi-contrast edges.

 

[EarlyMon]

I must be among the inordinately sensitive to this technology, as I can't look at a solid color or any sort of motion on these screens without seeing the effects of the PenTile. I guess it's not a deal breaker, but it is very noticeable and distracting for me. And I am a bit disappointed that I still see it in BruceWayne's video..assuming it will be a similar screen in the Nexus.

Everyone's mileage varies on this aspect.

Those that can see it sometimes find it hard to understand that others can't, and those that can't see it sometimes think that those that can see it are making it up.

This isn't necessarily a quality of vision issue - it's certainly a proof to what we all already know - everyone sees differently.

Fun fact - you can take a series of gray/black/clear transparencies of a picture, stack them just so on a light table, or in front of a projector, and when you hit the right combination of contrasts, the image suddenly goes from black and white to vivid colors. Cool stuff.

Just goes to show, eyes are easily fooled. Display technology works by relying on that fact.

When I said inordinate, I hope I chose the right qualitative word. I intended for the word (and concept) to be neutral - but I don't intend to inflame or diminish the importance of this issue to those with a sensitivity to it, one way or the other.

 

[BlueBiker]

OK. Power savings with PenTile - no.

I believe that's true w/RGBG (what the Nexus is expected to have), but my understanding is that white pixels in RGBW are especially power efficient, and large white backgrounds are a very common use case on a phone -- that has to be a big win. I thought someone mentioned RGBG being exceptionally energy efficient w/darker pixels, but I could be wrong about that.

Consider two screens at 720p, same size. Put up a solid red image on both. The rgb one will have 1/3 of its subpixels lit, the PenTile one will have only 1/4.

The only way for them to appear the same would be if the PenTile one increased brightness (increased power consumption) to compensate.

PenTile has fewer subpixels, but they're larger. An HD RGB screen will light up 921600 small red subpixels, while PenTile will light up 460800 big red ones. I have no idea how power comparisons come out here.

Some color combinations will save power, others will use more, and in the end, it's a wash.

That conversation took place in our Photon forum, I'll provide a link for those who need to hear her say it - or think of my example and let common sense guide you: no power savings.

Link please!

I know what their website says, its a marketing claim, we discussed that as well.

Heh, no argument here. Their site is smoke'n'mirrors.

Everyone sees differently, trust your eyes, buy what works for you.

Definitely. I can readily see the difference between Droid Charge's 216dpi and OG Droid's 264dpi at normal distance, but doubt I could pick up anything beyond that -- and really, the 216dpi was all I need.

Calculated earlier, the Galaxy Nexus' PenTile HD display could be considered to have an effective RGB resolution of 1045x588, which yields a very nice 257dpi.

PS - I don't like credential-based arguments but some do. My profile page lists mine for those that care about that sort of thing.

And I don't like name-dropping, so I won't tell you about my lunch with Stephen Hawking.

 

[EarlyMon]

I believe that's true w/RGBG (what the Nexus is expected to have), but my understanding is that white pixels in RGBW are especially power efficient, and large white backgrounds are a very common use case on a phone -- that has to be a big win. I thought someone mentioned RGBG being exceptionally energy efficient w/darker pixels, but I could be wrong about that.



PenTile has fewer subpixels, but they're larger. An HD RGB screen will light up 921600 small red subpixels, while PenTile will light up 460800 big red ones. I have no idea how power comparisons come out here.



Link please!



Heh, no argument here. Their site is smoke'n'mirrors.



Definitely. I can readily see the difference between Droid Charge's 216dpi and OG Droid's 264dpi at normal distance, but doubt I could pick up anything beyond that -- and really, the 216dpi was all I need.

Calculated earlier, the Galaxy Nexus' PenTile HD display could be considered to have an effective RGB resolution of 1045x588, which yields a very nice 257dpi.



And I don't like name-dropping, so I won't tell you about my lunch with Stephen Hawking.

Your wish is my command - Nouvoyance CEO chats with us here, note we were discussing rgbw, so my substantiated claims about power being a wash applies fully -

http://androidforums.com/motorola-photon-4g/374557-photon-lcd-screen-pentile-not-2.html

TANSTAAFL, compadre.

Where else can you go to get a first-hand interview with the progenitor of this technology?

I think you owe me a Steven Hawking story!

PS - interesting that you think that producing a white field that looks solid will be done so easily. I am not so sure about that. Could be wrong.

 

[BlueBiker]

Your wish is my command - Nouvoyance CEO chats with us here, note we were discussing rgbw, so my substantiated claims about power being a wash applies fully -

http://androidforums.com/motorola-photon-4g/374557-photon-lcd-screen-pentile-not-2.html

TANSTAAFL, compadre.

Where else can you go to get a first-hand interview with the progenitor of this technology?

I think you owe me a Steven Hawking story!

Got it, thanks Early! I'm about to crash right now, but it's bookmarked for later.

And, um, I've never actually met any famous physicists.

 

[BlueBiker]

This is something a lot of journalists like to claim because it's sensational. In the real world though, pixels are defined as pretty much the number of vertical and horizontal alternating black/white stripes that a display can produce while maintaining a certain contrast between each. These PenTile screens actually are their advertised resolution. They just use a different sub-pixel layout, that unfortunately some people are especially sensitive to, and tend to get a tad fuzzy on sharp, hi-contrast edges.

Guess it's a matter of semantics, as a one-bit monochrome display would satisfy the same requirements. Just seems to me if a test doesn't measure what people actually perceive, then it's not a useful test for measuring a device's suitability to be used by people.

 

[EarlyMon]

Competing technologies tend to cause technology advances.

PenTile, qHD, RGB, 720p, LCD, SAMOLED, in the end it all comes down to two things -

This is Android, where choice is good.

Manufacturers are competing hard to give choices that people want - we win.