SLCD, SAMOLED, Pentile, RGB Does it matter?

[Kevin OQuinn]

First, a quick glossary:

Contrast Ratio - The difference between the darkest black and brightest white a display is capable of.

Color Gamut - The percentage of visible light a display is capable of reproducing.

TFT - Thin Film Transistor. This is the layer that turns individual pixels on and off.

Digitizer - The part of the display that actually registers the touch input.

TL;DR Yes, it matters.

I'm sure a lot of us have some a few different types of displays. There are numerous threads debating which one is better, or can you see a difference, or does it even matter. I'm here to try and explain the differences between the technologies in an unbiased way (if that's possible LOL).

LCD - Liquid Crystal Display - The basic type of display. Just like on your computer monitor. There's an array of liquid crystals that will determine which color is displayed. They don't emit their own light, so there needs to be a backlight. In larger LCD's it's typically CCFL (cold-cathode fluorescent light). In phones and tablets it's LED, edge-lit to be exact.

OLED - Organic Light Emitting Diode - An LED made with organic materials that react to electrical currents. By there very nature they don't need a backlight, resulting in thinner displays. Each individual pixel generates its own backlight, meaning that when black is being displayed the pixel is effectively off.

These are the two basic types of displays that we have to deal with on our mobile devices. Below we'll dig into specific types a bit more, and why one might be more advantageous than the other.

 

[Kevin OQuinn]

LCD​

First, all LCD's that we're dealing with are active matrix. This means that each pixel has it's on transistor that can be turned on individually. That's what allows them to keep up with the demands of the modern smartphone or tablet.

TN and IPS are the two main types of LCD displays.

TN - Twisted Nematic - When a voltage is applied to the liquid crystal it twists perpendicular to the glass substrate to allow light to pass through. The amount of voltage applied will determine how much light is blocked. Unless you're dealing with an IPS LCD then you most likely have a TN LCD on your device. These are cheaper to manufacture, which is why they are so prevalent. There are generally considered to be poor quality compared to IPS or OLED, with less than ideal viewing angles and a small color gamut.

IPS - In Plane Switching - The liquid crystals are aligned parallel to the glass substrate. Being parallel to the glass gives it a huge advantage over a typical TN panel. It's an important difference because the light scatters less as it passes through the display matrix. That's why IPS panels have much better viewing angles. Color reproduction is also more accurate, and shifts significantly less than TN panels when viewed off angle.

PVA - Patterned vertical alignment - Drastic improvements in viewing angles and gamma (color) changes when viewing off-angle. Better color gamut and fast response time when compared to IPS or standard TN panels. The panels we're dealing with are the SPVA, which is what gives us the viewing angles and response time improvements. Standard PVA has a slower response time, but high contrast ratio and good color reproduction.

There are other display technologies that you'll hear about, but these are the two basic technologies behind them. Keep in mind that it's hard to get technical details on some of these.

Super LCD - An improvement on the traditional TN LCD offering better contrast ratios and higher color gamut. One of the ways it does is this is by a better manufacturing process. Typically there's an air gap between the LCD and top glass that you touch. Super LCD eliminates this air gap, meaning the light does less bouncing around. It also eliminates some of the sources of glare.

Super PLS - Developed by Samsung, this is a take on the IPS technology, purpotedly offering 100% improvement in viewing angles and 10% better brightness. They are also saying it's cheaper to produce, so expect to see this in more devices.

NOVA - This is LG only. It's an IPS based display with a brightness level of ~700 nits (for comparison the iPhone 4's display is 500 nit) and a supposed 50% reduction in energy consumption.

There's also a Super LCD 2, but I couldn't find anywhere that listed what the specific improvements were over any other LCD display. Eyes on are saying it's absolutely beautiful, but that doesn't give us any information about the technology behind it.

 

[Kevin OQuinn]

OLED​

For the purposed of this breakdown we're going to ignore PMOLED. PAMOLED is a passive matrix OLED. Just as with LCD, we're only interested in AMOLED (active matrix OLED), which employs a TFT layer to turn the individual pixels on and off. OLED's are also mainly a Pentile layout, which has it's own advantages and disadvantages.

SAMOLED - Super AMOLED- The main advantage here is that the digitizer is integrated into the display rather than being a separate layer on top. This improves viewing angles, contrast ratio, brightness, reduces glare, and makes the display thinner. This is still a Pentile layout.

SAMOLED+ - Super AMOLED+ - This moves from a Pentile layout to a traditional RGB layout, improving color accuracy and sharpness. Improvements were also made in brightness and energy efficiency. The + is what denotes the RGB layout instead of Pentile.

SAMOLED Advanced - Super AMOLED Advanced - Not having a + should tell you that this is again a Pentile layout, but with a sightly higher resolution.

HD SAMOLED - High-Definition SAMOLED - Exactly like it sounds. 1280x720 or 1280x800 resolution. It's a Pentile layout, though at this resolution that arguably isn't discernable to the human eye.

Clear Black - Nokia specific technology that reduces glare, raises contrast level, and allows for some seriously deep blacks. They use some polarization tricks to achieve this.

 

[Kevin OQuinn]

Pentile vs RGB​

There seems to be this stigma that a pentile layout automatically makes a display bad. There are a few factors that play into this. The major ones are screen size and display resolution. But first we need to know exactly what a pentile layout is.

Above is a picture of an RGBG pentile layout. This is the type of layout used by Samsung in the Galaxy S phones, as well as the Nexus One. This layout was used due to the human eyes sensitivity to green. In particular, our eyes are more sensitive to green luminance, or put simply, brightness. So green pixels don't need to be as physically large to appear just as bright to our eyes. The downside is that text isn't as sharp as an RGB layout, nor are any hard vertical lines, like when a black box meets a white background, or vice verse.

There's also the RGBW layout, which adds a white subpixel next to the standard RGB subpixels. This allows the display to have an edge in brightness due to a dedicated white subpixel. With that advantage the backlight doesn't need to be as bright, which saves battery since the backlight is a major user of battery in a mobile device. The Motorola Atrix 4G is one example of this type of layout. While sharpness is better than the RGBG layout, it still isn't as good as the standard RGB stripe layout.

Above is a picture of different types of subpixel geometries. We're interested in the bottom right image, specifically, because that represents the standard RGB subpixel layout. This is used in the majority of LCD displays, and in Samsung's SAMOLED+. It offers the best sharpness and generally the best color accuracy because all of the subpixels are the same size and have the same count (no extra colors).


Now that we have an understanding of the differences what does it mean in real life? Here's an example:

Above are close up pictures of the display on the HTC One S on the left and the HTC One X on the right. The One S has a 4.3" SAMOLED display at qHD (960 x 540) resolution with the pentile layout. The One X has a 4.7" 720p (1280 x 720) Super LCD 2 with the standard RGB layout.

Above are close up pictures of the display on the Samsung Galaxy Nexus on the left, and the HTC One X on the right. The Galaxy Nexus has a 4.65" HD SAMOLED display at 720p (1280 x 720) with the pentile layout. The One X has a 4.7" 720p (1280 x 720) Super LCD 2 with the standard RGB layout.

​

The above image is the Galaxy Note II with an RGB SAMOLED HD display on the left, and the Galaxy S3 with a Pentile SAMOLED HD display on the right.

 

[opec]

Amazing post. What about white balance? There is a big difference in between phones in the "whiteness" of their whites, and how bright that white actually is.

 

[lennydude]

I guess the biggest difference to MY eyes is the ability of the screen to produce the color WHITE.

I bought a Galaxy Nexus and was very disappointed in the screen. It would not produce white at all. The basic colors it produced can be argued over and over but did look good to me 99% of the time.

I recently read an ad HTC has comparing the SAMOLED screen and the SLCD2 screen of the One X. They included a picture of the One X screens ability to actually produce the color white.

If this is indeed true, i will be standing in line waiting for this phone! And the ad states it produces the white and uses less power doing so!!

Take a quick look at the HTC comparison picture i have included in case you have not seen it.

 

[Mtn_Scott]

Great write up. I would love to see a comparison of a SAMOLED vs. Super LCD2 running the same resolution. Right now it seems a little apple to oranges.

 

[Kevin OQuinn]

White balance has a lot of factors that play into it. Obviously the comparison is photography. The type of lighting has a huge affect on white balance. On a display it's very similar. The backlight for LCD's are white, so it makes sense that they are able to produce a "truer" white.

Another major factor is the calibration that is done by the manufacturer, and what the target color temperature is. I believe Samsung shoots for somewhere in the 5,000k range, which puts it below the established standard for sunlight, which is 6,500k (kelvin). That's why it has a slight yellow tint when displaying white.

Also, each persons eyes are slightly different. Just like when we're dealing with audio, what looks awesome to you might not to me, or to someone else for that matter.

@lennydude LCD is most efficient when displaying white, while OLED is most efficient when displaying black, and least efficient when displaying white. Do the same test with a black background and I would bet that the results change. Keep in mind that comparison was put together by HTC, who of course is going to do their best to make their stuff look awesome.

It's also worth noting that a lot of AMOLED displays seem to change their white balance with brightness, which is weird. I'm sure all displays do this, but it's definitely more noticeable with those.

 

[Kevin OQuinn]

Updated closeup display comparison in post #4. Which one do you guys think looks better?

 

[DaRkL3AD3R]

Nice writeup!

Obviously since both cases AMOLED is using Pentile, the LCD wins in quality, color and maybe losing in contrast. But realistically in a full lit area, LCD is all you really need for blacks to be apparently black. Yes in a pitch black room AMOLED will dominate the contrast arena, but eh I don't sit in the dark looking at my phone that's for you to decide.


Now if we had some Super AMOLED Plus (HD, not out yet) comparisons, then it'd be a different game.

Having owned the Galaxy Nexus, I am going to throw out my 2 Cents on that device. Worst phone purchase I've made in a long time, since my old flip phones. I promptly returned it and got my upgrade back. The screen is a disaster of quality control and poor technology. Pentile just needs to curl up and die somewhere, because it really is hideous. To the naked, untrained eye sure it's "ok" but to someone who knows what types of artifacts Pentile will produce, it's unbearable. Once compression in imagery takes over, Pentile has a hissy fit and shows its true ugly colors. You get blue aliasing everywhere. This is not to mention the beyond bad whites, which are either purple/green/blue/warmish orange, or they have some ugly striping and linen patterns woven into the whole screen; or worse, a combination of color and linen artifacts. Needless to say, there's no comparison in the above images.



Now, once the Galaxy SIII comes out with a 720p SAMOLED Plus screen, then we'll be in a different game altogether. That RGBRGB layout is critical for reproducing accurate colors/digital display that I am surprised Pentile was even brought up.


Here's hoping May 3rd the SIII is revealed in all its rumor-laden glory and it holds up to most of them

Thanks for the write up, will definitely bookmark and use it in any Pentile SAMOLEDHD vs RGB SAMOLED+ arguments

 

[anon(21022)]

great writeup!

I can sum up the "does it matter?" in this way:

It doesn't matter until you get something better and look back at what you had before, or go back to something similar to previous technology.

e.g., my 4" pentile qHD Super Amoled phone was great and I didn't see anything wrong with it UNTIL I upgraded to an HD 4.3" LCD RGB phone.

A day later I turned on my old phone and immediately noticed two things:

1 - pentile/qHD Sucks compared to my new resolution/HD density/clarity
2 - the super amoled was WAY better at dealing with direct sunlight, I kinda miss that.

Overall though I'd have a lot of trouble going back to the old screen. So it DOES matter unless you've never experienced the better one

 

[scoobdude]

I am currently a photon user. I just want to add that display technologies have their limitations but software also plays a major role. For instance on my photon (960x540 4.3 pen tile rgbw screen) the screen was AWESOME in sunlight. But try to watch Netflix and you would get black crush like a MoPho (Motorola Photon) lol. But a quick kernal/rom upgrade fixed this.

Another instance us the nexus was issued a sw update to change the color temperature. And you could instal voodoo to change the display settings.

Another issue dealing with bigger LCD is the fact that green cannot be portrayed correctly when compared to plasma and crt type displays. I am not sure if this has changed much since ups panels and such have come about.

P.s. I am no expert and maybe wrong as I am saying things from memory so please feel free to correct me

 

[razgri5]

Is it possible to have a SAMOLED HD display with RGB? Or would pentile be comparable at that resolution?

 

[movielover76]

I don't own the super advanced displays yet, but I tend to prefer SLCD over Super Amoled
I have both owning an htc and samsung phone and I prefer the more accurate colors on SLCD, that color difference seems to be consistant over all of the versions of SLCD and Super amoled I've seen.

I'm looking for SLCD2 on my next phone

 

[Kevin OQuinn]

Is it possible to have a SAMOLED HD display with RGB? Or would pentile be comparable at that resolution?

Logically it makes sense that Samsung will introduce that next. There's no official word, of course, but we went from regular SAMOLED to SAMOLED+ at the same resolution, so it would make sense to introduce HD SAMOLED+ next.

 

[Kevin OQuinn]

The Voodoo controls available on particular phones used to adjust the display properties would be the same as calibrating your tv. Everything ships with values from the factory, but that doesn't mean they can't be changed. You just need to be given the ability to do it.

 

[Officerpolabear]

All in all, the new 720p screens are all great regardless of being SAMOLED, SLCD, Pentile, or Non-pentile. Come on, we are talking about laptop resolutions on a cell phone screen, a cell phone! I'm sure all of these screens will be more than capable of catering to the user's needs.

 

[Kevin OQuinn]

All in all, the new 720p screens are all great regardless of being SAMOLED, SLCD, Pentile, or Non-pentile. Come on, we are talking about laptop resolutions on a cell phone screen, a cell phone! I'm sure all of these screens will be more than capable of catering to the user's needs.

Definitely a true statement, but look at the difference in quality between the various 1366 x 768 laptop TN LCD mediocrity.

I'm really glad that manufacturers are taking screen quality seriously, and this is one thing that I hope they continue to do.

Keep in mind that we're still bound by physics. You can only fit so much in a given space, and that's why the first SAMOLED+ displays couldn't be smaller than 4.3".

Oh how technology progresses in such short periods of time.

 

[ilkhan]

HD SAMOLED+ (SGSIII) vs SLCD2 (OneX) will be the most relevant comparison.
But those 2 phones in general will be the flagships for 2012, and thus the most relevant comparison in general.

Very nice work here.

 

[prediscover]

Great writeup, but can you add a comparison of a SAMOLED+ screen (ex: Skyrocket or Skyrocket HD for 720p) to HTC One X 720p LCD2 display? Both are RGB Layout.