Why OLED screens, even with their failures, mark the future of the smartphone

OLED technology marked the world of mobile telephony in 2017. On the one hand, by reaching the best-selling high-end terminal , the iPhone. On the other, to weaken with a strong bluish tone with tiny variations of angles to a smartphone as good overall as has been the Google Pixel 2 XL , as we saw in his analysis.

Its evolution deserves to be reviewed in depth, because not so long ago it seemed to be a member of the group of technologies that promised a lot, but did not quite comply . The technical deployment of Samsung in smartphones and LG in televisions has made it possible to implement them at forced marches, until today offering some of the best screens in the market .

Along with this, we will see challenges of OLED technology to improve, that although it may be thought that it has already reached perfection, it has much room for improvement in terms of dealing with known problems such as image retention, but all where his best ally, the black, is the protagonist.

Finally, we will see what the future holds for organic diode technology, if it is not soon followed by a superior technology.

Brief history of OLED in smartphones

After researching OLED technology since the 90s, Sony announced the start of commercial production of OLED panels for mobile phones in the spring of 2004. Given the small quantities, the company only used the panels for its own products. The first smartphone to integrate this technology was a PDA, the Sony Clie VZ90 in September of that same year, although it never left Japan.

As of that moment, it was Nokia who premiered the AMOLED technology in the Nokia N85 . The terminal benefited from the innovative screen technology to save energy with its predominantly black theme. In addition, Nokia implemented something that is now very fashionable, but at the time was an unknown function: a kind of “Always On” mode that showed the time in white on a pure black background when the terminal went into standby mode.

The Nokia N85 kicked off the AMOLED technology in mobile phones.

But what did the AMOLED panels provide ? Within the OLED, there is the passive matrix and the active matrix (Active Matrix Organic Light Emitting Diode). The first is used in music players with small screen, wearables or car information screens: simple solutions, because the screen is controlled by the lighting of its rows and columns. AMOLED have different controllers, and as we know each pixel is managed independently. In addition, there is a TFT matrix that controls which pixels should be turned on, which helps to save a lot of energy , because in passive matrix that action is done with external circuits.

One of the aspects that greatly delayed the arrival of OLED technology to the public was the need to invest large amounts in research and factories.

Thanks to a growing production since 2002, Samsung reached 30 million panels manufactured in 2005 , which, together with the opening of more plants, allowed it to reach its own and non-owned terminal shelves since 2009, where the first Galaxy and the Omnia . In 2010 we also saw AMOLED technology on the Nexus One and the HTC Desire , although only temporarily, as Samsung began to have problems supplying panels, something that only time has solved with more factory extensions and a notable increase in production. The low availability of OLED screens (which generates a higher price) is still something that manufacturers continue to struggle with.

All this was just the prelude to the terminals that began the massive popularization of OLED technology under its own brand: SuperAMOLED and the family, formed by the Samsung Galaxy S. However, the first terminal to assemble the new panels was , for months (from April to June), the Samsung Wave.

It is with the original Galaxy S when we see for the first time, in a massive way, some colors with an intensity never before present in a mobile phone (and practically no commercial screen). It had the bad luck to coincide with the most realistic calibration, the very superior brightness and the absurd sharpness of the Retina display of the iPhone 4.

Samsung Galaxy S, the massive starting point of SuperAMOLED technology.

In any case, began a broad debate that would last until today, with many users prefer the extreme saturation in the colors against the first, moderation, and then screen color accuracy. The numbers could be more or less close to reality, but came through the eyes before LCDs that despite being more mature, had more difficult to fill the spectrum of desired color, sRGB.

The good work done in clarity and calibration of the LCD screens from 2010 subtracted brilliance to the enormous achievements of the first AMOLED.

So, it is not until the end of 2013, with the Samsung Galaxy Note 3 , when we can finally talk about screens that are not only effective and showy indoors, but also outdoors, launching the boost mode of brightness in high-light environments . It was a very important step, because in addition to competing in representation of color and efficiency, the great war between OLED and IPS was in search of maximum luminosity, which at that time clearly led the second.

DisplayMate , reference web analysis screens (though not measuring problems then we will see in depth), is a good source to see how it has grown in SuperAMOLED brightness of the Galaxy S. The first figure corresponds to the maximum brightness in a 100% white screen, and in parentheses, to the maximum brightness mode with automatic brightness in very bright environments:

Brightness in nits. More is better. Graphic: Own elaboration - Source: DisplayMate — Created with Datawrapper

Evolution of brightness in Samsung’s SuperAMOLED displays

For years, the low maximum brightness was one of the big problems of OLED screens. From 2013–2014, everything changed.

And finally, just a year later, DisplayMate speaks of “screen indistinguishable from perfect in color reproduction accuracy” on the Samsung Galaxy Note 4 , provided that the “Basic mode” was selected in the screen settings. The Note of 2014, released, in addition a QHD panel that eliminated with a huge density the sharpness problems of its subpixel pattern PenTile. Unlike the classic RGB pattern, where each pixel contains a red, green and blue sub-pixel, in the PenTile panels there is a lower number of sub-pixels, specifically, one third less.

Instead of having the same number of subpixels of all colors, there is twice as many greens as blue and red, and with different sub-pixel sizes. This is because the green sub-pixel is the most durable and efficient , while red and particularly blue tend to die earlier. Visually, the sensation that this arrangement produces in screens with low density is of little definition, something caused by the black space that leaves the smaller number of the subpíxeles. The explanation of use behind the PenTile, theoretically inferior to RGB, is found in the search for maximum longevity, since the degradation is much greater than LCD screens.

Samsung Galaxy S6 Edge, the curves that marveled in 2015.

Samsung began to be highly acclaimed in analyzes, and in many ways, the envy of the industry , saving Apple, maybe HTC. Despite this superiority, the South Korean company did not stop the innovative pace and impressed technically with the curve in the Note Edge and the curves in the Samsung Galaxy S6 Edge .

The present of OLED technology: brightness with a long way to go

It is from 2014 when referents such as DisplayMate begin to talk about the perfect screen in terms of colors and saturation. Clearly it was an exaggeration, because Samsung has continued to bring great perceptible improvements in virtually every generation. The vertiginous pace that the South Koreans have printed since 2010 has made us think that we were facing a mature technology, being really adolescent.

It is more evident when leaving Samsung and we turn to panels manufactured by LG, with the aforementioned case of Google Pixel 2 XL. We speak only of smartphones, because in panels of televisions (with greater difficulty of production) and wearables (making the one of the Apple Watch) they have shown to be at a great level.

However, even going back to Samsung and its implementations in own terminals, there are realities that may lead us to think that we have only passed a first stage of OLED / SuperAMOLED technology where the priority objectives have been reached, to move now to solve problems maybe not so relevant users who are not so expert.

The debate between OLED and LCD has always been tremendously subjective and a matter of taste.

In that sense, we have to remember the debate we were coming from, and how the advantages and disadvantages were valued: the unbridled saturation and the white balance fired towards cold tones. What the experts of the industry considered unpleasant defects that with time could be controlled, for the public supposed one more reason than to show off .

Black crush , or the lack of detail in dark areas close to black

Generally, when talking about OLED technology, it is praised how these panels reproduce the black, or rather how they do not reproduce it, since being self-emitting what is done is turning off the pixels. In this they differ from the IPS LCD screens, which depend on a lighting source that, in the best case, can only show a black near the cigar thanks to the zone or local dimming.

However, there is little talk that black can also be the worst enemy of any OLED screen, for reasons not yet solved in Samsung Galaxy S and high-end TVs.

Playing grayscale is not easy for these screens, because as colors approach black, they tend to get lost in it and “burn” in what we know as “ black crush “ or “ black clipping “. As in high lights the overexposure makes lose all the detail of a zone, in dark images or with dark zones the same thing can happen when certain tones that are not totally black reproduce as such.

At the top we see a screen that shows no detail in the shadows of objects (jacket or hair) because of the black crush, while the lower one perceives many more details.
The Samsung Galaxy Note II (top) managed the gray scale very well and did not present black crush. The Samsung Galaxy SIII (bottom), on the other hand, was the perfect example of how SuperAMOLED displays were not yet consistent. Source: Erica Griffin.

This may not seem important but while content is reproduced in dark environments, in theory the ideal scenario for OLED, where you can look at the low contrast and black level of LCDs, the feeling may be that you do not perceive much detail that does. go in the second, even if it is a little washed. Another problem with black crush is that it is often accompanied by artifacts and banding that can be very visible by changing the black pixels to another color.

All this, more than an issue inherent in OLED seems a matter of calibration. Deepening, as discussed in Anandtech, a medium dedicated to technical analysis and whose editors have extensive experience in the industry, DDIC controllers also have responsibility and use PWM or pulse width modulation.

If the multimedia section is crucial in the choice of smartphone, the “black crush” conditions the visualization of contents.

The “black crush” is not an issue that is usually played in the majority of media analysis and YouTube channels, but those more technical, such as the aforementioned Anandtech, or the Erica Griffin channel, often go deeply into the problem. Erica usually shows how each terminal that it analyzes represents the gray scale with a table with black numbers and a color below. In a perfectly calibrated screen, all the numbers would be perceptible, except the 0, whose background the pure black. The less you see, from 21, with a gray background, the worse it is in that sense. Let’s see some examples.

The first corresponds to his analysis of Pixel 3XL , where she compares the issue with the iPhone XS, which together with his brothers with OLED is considered the best screen in this regard. Without being perfect, the terminal of Apple allows to discriminate much more tonality.

Because it only shows numbers clearly from 9, dark scenes will not be seen in much detail on the Pixel 3 XL, particularly at low brightness. Source: Erica Griffin.

Secondly, we see the results obtained by Erica in the analysis of the Huawei P20 Pro, where the Chinese terminal gets much better results than the Samsung Galaxy S9 +, considered by many to be the best screen terminal on the market, next to the Samsung Galaxy Note 9, whose image of the analysis we see later.

The P20 Pro is next to the iPhone, the best in black crush management. The Samsung Galaxy S9 +, despite having a very superior panel in other ways, can not say the same here. Source: Erica Griffin.
The Samsung Galaxy Note 9 also suffers from the same problem as the Samsung Galaxy S9 +. Not only is not perceived too much from the number 6, but the degradation between colors does not occur smoothly, but too staggered. Source: Erica Griffin.

Black smear: when the speed of ignition of the pixels is not enough

The dark modes are fashionable, having recently reached macOS Mojave and Windows 10. In Android, which has always been good representation of OLED screens, there have been advances and setbacks in this regard. Android 2.3 Gingerbread and Android 4.0 Ice Cream Sandwich brought many dark elements to the system benefiting the different Nexus (and terminals with OLED screens) launched next to each system, but later returned to the “bright side” with Android 5.0 Lollipop.

The point is that there is always a dark or black theme associated with helping reduce the consumption of OLED screens, and energetically speaking, it is a real and measurable advantage.

However, to give an example, if the subject is not completely black and other colors are also present, it is relatively easy to see what is known as “ black smear “. To better understand what it is about, we will now see it in a GIF from this explanatory video, but it can be defined as an existing latency with the movement of the contents in black when they change their position in contact with colors that require the turning of the pixels.

“Black smear” on a Huawei P20 Pro. Unlike black crush, it is inherent in any current OLED screen.

The slow lighting of the pixels that are in black (produced in turn by the slow response time of the blue sub-pixel , the weakest of the three) to move to another color has not yet been solved, and in actions as in A scrollin a Twitter or Reddit client can become annoying, worse than the slight “ghosting” effect.

In front of the “black crush” of the previous section, the “black smear” is something more inherent in OLED, so even the screens of the Huawei P20 Pro, my personal smartphone, or the iPhone X / XS are not able to mitigate it. Perhaps the degree is less than other terminals, but in addition to slowly turning the pixels on and off black, on the edges of changing colors you see a lilac color that contaminates the image and should not be present. You can check the problem with the gif of the next tweet (it is appreciated above all with the low brightness in a low-light environment, typical and everyday when reading in bed).

OLED no longer has to wait, its sweet moment is the present

We have reviewed defects of OLED screens in smartphones, but that does not mean that it is not a fantastic technology. In addition, it's great rival, IPS LCD technology has also historically presented other shortcomings, such as bleeding, reduced viewing angles or a level of blacks that, in some cases, remains disappointing.

There is no perfect technology, and that is not a problem. The contribution of OLED screens to smartphones has been enormous, and has allowed to enjoy many elements that otherwise might have been delayed for years. Energetically, once the high consumption showing white has been overcome, they have helped to obtain autonomies that despite the feeling of little progress, continue to increase and that can even be improved by optimizing dark subjects better.

But where we can most value these panels is in their physical technical achievements. With the OLEDs, a very precious thickness was eliminated in order to achieve finer and finer terminals, something that the LCDs continue to make complicated. Although they have not yet arrived commercially, OLED screens will also change everything in folding smartphones, a trend that very early, Google already supports it.

The secret of the lower edge of the iPhone with OLED is how Apple and Samsung have folded the panel.

Going further, the Samsung SuperAMOLED screens took us to the future in 2014 and 2015 , with the side bends that seemed impossible. Later, even in the era of the barbles of the terminals without frames, Apple was able to bend its panel in the inferior part of the iPhone X , to avoid losing the symmetry in edges that it keeps with the superior part.

The pure black and the saving of the dull pixels have brought us “ Always On “ modes that many users appreciate for their information at a glance with hardly any extra consumption. For about five years, maximum brightness has also been present when it is most needed, under the sun, and the multimedia experience with well-calibrated screens has allowed the audience to enjoy content even better than in many high-end TVs.

The future challenges of OLED technology

Beyond everything reviewed, the message is clear: OLED technology and its variants are in the best moment of its brief history. In the search for maturity, these problems and other classics already reduced should be solved, such as the retentions and burns of burn-in or the variations of color along the panel, which produce pink or green tones in certain points of certain screens.

On the one hand, it seems that, in the short term, the future that we will see in OLED will be the flexible screens in folding smartphones. However, at the level of technology what is expected is to see refresh rates higher than 60 Hz (120Hz or 144Hz), like those that are already being seen in smartphones for gamers.

The ASUS ROG has an OLED panel of 90Hz, but neither is a massive terminal (like many LCD screens on laptops or the iPad Pro) or exceeds the 1080p resolution. One possible impediment to seeing the refresh rate increase in highly sold terminals may be the “black smear”.

It seems that Samsung is going to re-bet everything on the folding screens.

On the other hand, and starting from the fact that currently available OLED panels are excellent, manufacturers are already looking for alternatives that, without abandoning pure black, solve inherent problems such as the degradation of brightness and the colors they experience together with the retention of color, due to the fact that it is an organic technology.

The most likely successor, or parallel alternative, is microLED , a self- emitting technology that Samsung has already shown on its giant TV The Wall, 146. “The South Korean company has not made announcements related to technology in smartphones, but according to Mark Gurman, Apple already works on its own MicroLED panels, which would first reach the Apple Watch and later the rest of the products in the range.

It makes sense that from Cupertino follow the path started with processors A in other areas, such as modems, or on screens, looking for their own solutions, but also more scalable and cheaper than the OLED.

In any case, as users of OLED technology, we can only hope that the next ten years will keep pace with the splendid path initiated by the Samsung Wave and the Samsung Galaxy S eight years ago.