Thursday, December 28, 2017

Smartphone Display Technologies and Terminology Explained: OLED, LCD, Strengths & Weaknesses

In light of recent conversations about smartphone displays, it's important to take a step back and consider all the terms we keep reading about in context. Phones like the Google Pixel 2 XL have been criticized for their displays, but on the other hand, consumers have generally praised OLED panels. With such a robust ecosystem, there's a lot to learn about our devices' screens in 2017, and the more we know about their strengths and weaknesses, the more we can get to the root of these online debates.

What is the difference between an AMOLED display and a P-OLED display, or between a LTPS display and a IGZO display? What makes one smartphone display better than the other? Should we base our assessments on objective data or on subjective impressions? This is where the topic of smartphone display analysis plays a key role.

Smartphone display analysis isn't an easy field, and to accurately measure the properties of smartphone displays, reviewers need hundreds to thousands of dollars worth of equipment, including (but not limited to) colorimeters, spectrophotometers, color calibration software, luminance meters, and more. But having the equipment isn't enough; smartphone display testers have to adopt stringent methodologies to ensure valid and replicable data that accurately showcases the differences across various panels. This is a field where tech jargon is used in abundance, yet often poorly explained, leaving most people who read reports from sites like DisplayMate a bit confused. That's just the tip of the market's iceberg of problems, though.

So why go to all the trouble of giving the smartphone displays a hard look? The reason is simple: Without their high resolution, high-quality touchscreen displays, modern smartphones wouldn't have the same appeal as they do now. Screens are the medium through which we interact with and consume the content that millions of creators and developers work hard to produce, and screens should do that content justice.

We can see how smartphone display quality has steadily improved over the years along with the problems that displays face today. For the purposes of this article, we're only considering display quality on touchscreen smartphones released on or after 2007.

You read the title, you know what this piece is about, so let's begin!


Evolution of smartphone displays

Apple's original iPhone, released in 2007. Source: Apple

The original iPhone had a 3.5-inch TFT display with HVGA (480×320) resolution. The first Android phone, the HTC Dream / T-Mobile G1, had a smaller 3.2-inch display with the same resolution. These displays were not IPS (an acronym for in-plane switching, which we 'll come back to later on), and they didn't have a 16:9 aspect ratio — indeed, to most people, their old 3:2 aspect ratios look a little outdated. In terms of display quality, the screens weren't usually calibrated for color accuracy, and brightness, contrast, and viewing angles were sub-par compared to today's screens.

Smartphone displays have come a long way since then. In 2009, the first Android phones arrived with WVGA (800×480) displays and  15:9 aspect ratios. Then, in early 2010, the first OLED phones were released. Samsung's AMOLED displays were used on the Nexus One and HTC Desire, with the same nominal WVGA resolution but a PenTile matrix pixel arrangement, which lowered the screens' effective color resolution (more on this later). As these were the early days of this technology, the display quality on AMOLED wasn't up to scratch yet.

Apple stole Samsung's thunder with its Retina display, which debuted on the iPhone 4 in June 2010. It had a then-unmatched 960×640 resolution (326 ppi) with IPS technology, which was as good as the technology could get at the time.

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Apple's iPhone 4. Source: Apple

The iPhone 4's Retina display was without equal in the Android world. But that didn't discourage Samsung from attempting to one-up it. The Galaxy S, which was released around the same time as the iPhone 4, featured the South Korea-based company's new Super AMOLED display technology. It was a newer generation compared to the Nexus One's display, and it boasted better visibility in direct sunlight. Unfortunately, though, it used a PenTile pixel arrangement and its image sharpness fell short of the LCD competition.

But display quality on smartphones kept getting better over time. 2011 saw Samsung's Super AMOLED Plus display with an RGB matrix pixel arrangement, the first and last of its kind. And it saw the rise of 720p HD displays both in LCD and OLED screens, which overtook Apple's original Retina resolution and kicked off a new front in the display wars: Pixel density one-upmanship.

Displays have advanced at an ever-more-rapid pace in the intervening years. LCDs improved substantially, reaching 1080p Full HD and then QHD resolutions with RGB matrix technology; brightness up to 700 nits; 178-degree viewing angles (at the high end of the spectrum, thanks to IPS); and contrast ratios cracking 2000:1.

Samsung's AMOLED displays improved so quickly, in fact, that the technology began to leapfrog LCD in 2014. For a few years running, every Samsung flagship has topped DisplayMate's list of top smartphone screens — until the trend was broken with the iPhone X's OLED display (a Samsung-made panel), which DisplayMate crowned this year's best smartphone display.

For a time, Samsung Display was the only manufacturer of note in the OLED space, but that changed in 2017 when LG Display secured a high-profile contract to ship its P-OLED displays on smartphones.

So, we've seen the rise of sRGB and DCI-P3 color calibration in smartphones, and both major mobile operating systems support color management now. We've also seen the emergence of mobile HDR displays, and of adaptive screen refresh rates up to 120Hz. There can be no doubt about it: The future is bright for smartphone displays.

With all that in mind, let's clear up and expand on some common display terminology.


Display terminology in Simple Terms

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A comparison of several display technologies and pixel arrangements. Source: Wikimedia

LCD (Liquid Crystal Display): An LCD is a flat-panel display that's based on the light-modulating properties of liquid crystals. Although LCDs are very thin, they are composed of several layers. Those layers include two polarized panels with a liquid crystal solution between them — light is projected through the layer of liquid crystals and is colorized, which produces the visible image.

The important thing to note is that the liquid crystals do not emit light themselves, so LCDs require a backlight. They're thin, light and generally inexpensive to produce, and the most mature display technology used in smartphones.

Some of the advantages of LCDs include high brightness, consistent color fidelity at different viewing angles, better color sharpness thanks to the use of an RGB matrix, and longevity (LCDs aren't susceptible to burn-in, though they can suffer temporary image retention). They also tend to exhibit lower contrast and response times compared to some OLED equivalents.

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A diagram of in-plane switching technology. Source: SIIM

IPS (In-Plane Switching): In-plane switching involves arranging and switching the orientation of molecules of the liquid crystal layer between the glass substrates of the display. Simply put, it's a technology that's used to improve viewing angles and color reproduction on TFT displays, and that's intended as a replacement for TN (Twisted Nematic) displays. It's used on LCDs to get up to 178 degree horizontal and vertical viewing angles.

OLED (Organic Light Emitting Diode): OLED, unlike LCD,  does not require a backlight, because the pixels contain light-emitting diodes that power on and switch off on an individual basis. The advantages of OLED displays include a theoretically "infinite" contrast ratio, and also a wider native color gamut, a lesser shift in brightness at different viewing angles, and better power efficiency with low APLs. The downsides include color shifting at different viewing angles, burn-in, and lower power efficiency in high APL applications.

APL (Average Picture Level): APL determines how much white content is on a given screen. Without knowing the APL of a piece of content, the true brightness of an OLED display can't be determined, which is why we show typically see multiple measurements at different APL percentages. 100% APL is completely white, while 0% APL is a completely black screen without any trace of white. Brightness in OLED panels is variable — it increases in low APL scenarios and vice versa.

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The benefits of LTPS. Source: Ubergizmo

LTPS (Low-temperature Polysilicon): This is a manufacturing technique in LCDs. It substitutes amorphous silicon for polysilicon to increase display resolution and maintain low temperatures. It is used to increase power efficiency and pixel density.

IGZO (Indium Gallium Zinc Oxide): A IGZO is a display made with an artificial transparent crystalline oxide semiconductor, first produced by Sharp. It is composed of indium, gallium, zinc and oxygen, and it's mostly used in tablets, though some smartphone manufacturers are starting to use it, too. (A good example is the 120Hz displays on Android devices like the Razer Phone.) It promises large power efficiency improvements, but the downside is that some displays have reduced brightness and contrast compared to LTPS LCDs.

HDR (High Dynamic Range): HDR, or high dynamic range, is a display feature in some newer devices and future flagships that promises a more lifelike media-viewing experience. Here's the simple explanation: HDR-capable displays have a high peak brightness, giving scenes more detailed shadows without sacrificing detail in highlights. On top of that, they can display wider color ranges and richer color depths, leading to a higher number of colors with more steps in each color gradient.

This is because HDR displays support wide color gamuts (DCI-P3 is currently the most widely supported wide color gamut), and also support 10-bit color (per the UHD Alliance). This theoretically allows HDR-enabled smartphones to display over 1 billion colors. As of now, flagship smartphones are starting to support the HDR10 and Dolby Vision standards.

Candela per meter square: Candela per meter square, also known as nits, is a function of the intensity of the light source, and it's used to measure the brightness of any screen). The higher the cd/m^2 number, the brighter the display. You'll find most display reviews for smartphones carry out measurements at around 200 nits.

Contrast ratio: This is the ratio of a display's  peak brightness to its black level. OLED displays have a theoretically infinite contrast ratio because the pixels can be completely switched off, though in practice, ambient light prevents this from being realized except in a completely dark room. Thus, OLED panels can improve their contrast ratio by reducing screen reflectance.


Issues in modern LCDs

LCDs are the most popular smartphone display technology on the market. The vast majority of budget and mid-range smartphones have LCDs rather than OLED displays, mostly because of cost. In non-flagship smartphones, using LCD instead of OLED reduces the manufacturers' bill of materials (BOM), which subsequently increases the profit margin and lowers the cost.

That doesn't mean, though, that LCD is free of drawbacks. While it's regarded as a more mature technology than alternatives like OLED, LCD is inferior to OLED in several respects. Let's take a look at them one by one:

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OLED and LCD contrast ratios compared. Source: 4K LED TV Review

Contrast. Modern LCDs have up to 2000:1 static contrast, though manufacturers sometimes market a higher dynamic contrast. In that respect, LCDs fall far short of OLED's theoretically infinite contrast, though vendors such as Apple and Huawei choose to forgo the infinite contrast rating. The reason? Blacks on LCD displays aren't true blacks because of the screens' backlight. Even the deepest blacks look like a  dark shade of grey, and this is especially noticeable in the dark.

There's no real solution to this problem, because LCDs require a backlight to function — the screen wouldn't be visible otherwise. Display manufacturers' only recourse is reducing the luminance of the black levels — the darker they are, the higher the contrast.

In environments with a lot of ambient light, there's actually very little perceptible difference between LCD and OLED displays (at least on this aspect), because the advantages of the latter are basically negated. However, when you're watching a video or using a dark theme or wallpaper, LCD's weaknesses are highlighted. The issue is also apparent in the displays' viewing angles, as blacks tend to wash out as the angle shifts from left to right. This can make the media-viewing experience feel less immersive.

LCD displays' contrast shortcomings also affect legibility in sunlight. In the past, LCDs used to be unquestionably superior to OLED displays in direct sunlight, but that's no longer the case. OLED displays equipped with auto brightness boost modes and other technologies are able to take advantage of low reflectance and higher contrast to outclass LCDs.

Despite the fact that LCDs have higher sustainable brightness levels than OLED displays, sunlight legibility tends to be better on OLEDs thanks to the reflectance and contrast deficiencies in modern LCD panels. They might be mitigated in the future with brighter displays with higher native contrasts, but LCDs have lost momentum here.

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LCD viewing angles compared. Source: Mitsubishi

Brightness fidelity in viewing angles. The best IPS LCDs are mostly free of color shift, which means that their colors don't change or exhibit a tint at angle shifts. However, even a slight shift in angle unavoidably impacts the perceived brightness level. It's not a dealbreaker, but it's more palpable in budget and mid-range smartphones, which tend to experience a higher degree of color shift than premium devices.

OLED displays aren't affected by brightness and loss of contrast  when their viewing angles are shifted, so it really comes down to picking the lesser of two evils: Can you live with color shift, or a loss in brightness? In case of the former, you should opt for an OLED display, and in case of the latter, LCD is your best bet. Higher quality panel (typically found in flagships) can essentially eliminate this dilemma.

Inferior response times compared to OLED. LCDs have been steadily improving on this front, with newer-generation LCDs suffering from less ghosting compared to older displays. However, this is another problem which can be mitigated but not solved. OLEDs are simply superior in this area, and that's one of the reasons why Google's Daydream mobile VR platform requires OLED displays.

LCDs in budget and mid-range smartphones are more prone to ghosting and lower response times. This can make the phones feel less smooth and responsive than competitors with OLED displays.

Overall, it's tough to severely criticize LCDs because of how immensely they've improved in the past few years. It's not uncommon for budget smartphones to have 5.5-inch Full HD IPS displays without color shift, which is measurably better than the flagship smartphones of a few years ago with inferior resolutions, brightness, and color accuracy.

But it's in the flagship (and increasingly mid-range) devices that LCD's limitations rear their ugly heads. The evidence from experts suggests that OLED, despite its relative immaturity, is overall better than LCD at the high end. That's why LCDs are becoming much less common in flagship smartphones, despite the fact that they support wider color gamuts (such as DCI-P3), HDR standards such as HDR10 and Dolby Vision, and higher response times than ever before.

It seems likely that the current pace of improvement in OLED will ensure its superiority over LCD. But OLED isn't perfect either. Let's move onto its biggest issues.


Issues in OLED displays

Samsung has gone all-in with OLED since 2010's Galaxy S. A multitude of OEMs now seem to prefer OLED displays in their flagship smartphones, and the technology is slowly permeating mid-range and affordable flagship devices. And although budget phones with OLEDs aren't particularly common, that could change in a few years as the price of OLED displays continues to go down.

Just because a particular technology is popular doesn't mean it's free of issues, though. OLED screens are visibly imperfect, to the extent that the quality can start deteriorating in days, with some users noticing signs of burn-in not long after they began using their phone. The display tech also has long-standing issues that haven't been addressed after multiple generations.

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PenTile matrix OLED displays compared to S-Stripe. Source: SamMobile

PenTile matrix. PenTile matrix OLED displays fall short in image sharpness. Most LCDs use an RGB matrix, which means they have three uniform subpixels (red, green, and blue) per pixel. PenTile OLED displays have only two subpixels per pixel (red and green, or blue and green) in an uneven layout. Since the Galaxy S4 in 2013, PenTile OLED displays have used a subpixel layout that resembles the shape of a diamond —  hence the term "Diamond PenTile". While the number of green subpixels in a PenTile OLED display are equivalent to the number of green subpixels in an LCD, the number of red and blue subpixels is smaller.

To be precise, PenTile OLED displays contain only half the number of red and blue subpixels compared to the number of green subpixels. That means that despite having equivalent nominal pixel density compared to LCDs, PenTile OLED displays are not as sharp because their subpixel density is lower.

Therefore, a Full HD (1920×1080) LCD display is sharper than a Full HD PenTile OLED display, though that difference varies depending on the content displayed on the screen. The effective color resolution of a PenTile OLED display is always lower than its nominal resolution. In case of a Full HD (1920×1080) display, the effective color resolution is 1357×763 (divide both vertical and horizontal resolution by the square root of 2).

That doesn't mean that PenTile OLED displays are only half as sharp as their LCD competitors with RGB matrix pixel layouts. PenTile OLED displays feature a technique called subpixel anti-aliasing to cover up the pixel deficit. Though it doesn't fully close the gap, it helps to mitigate the loss of effective color resolution.

The effect of PenTile arrangements are most obvious in text rendering. Because the subpixels have an uneven layout, the edges of the letters have a PenTile effect. In essence the text isn't as sharp as RGB matrix LCDs, to the point where QHD PenTile displays are about as sharp in practice as Full HD RGB displays.

So is there a solution? In 2011, Samsung shipped an RGB matrix AMOLED display in the Galaxy S II called Super AMOLED Plus. In 2012, the Galaxy S III adopted a PenTile arrangement again to accommodate the HD resolution, but with the Galaxy Note II, Samsung tried something different.

The Note II had an S-Stripe display (on the basis of leaked marketing material) with a non-standard RGB matrix. Although the subpixel layout wasn't as even as a traditional RGB matrix, the key point was that the display had three subpixels per pixel, overcoming PenTile's sharpness issues while maintaining a relatively high resolution (HD).

But the S-Stripe display was short-lived as Samsung moved to diamond PenTile with the Galaxy Note 3, and while the company continued to use S-Stripe AMOLED displays in 10-inch tablets such as the Galaxy Tab S, the tech hasn't made an appearance in other smartphones.

Even the iPhone X uses a PenTile display with subpixel anti-aliasing, proving that S-Stripe at high PPI (pixels per inch) remains financially or technically infeasible. (Blue subpixels age the fastest in OLED, which Samsung cited as the reason for its move back to PenTile with the Galaxy S III).

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The iPhone X's PenTile OLED screen. Source: The Verge

In summary, PenTile remains an issue with OLED, particularly at lower resolutions. PenTile HD displays are sub-optimal in sharpness. Things get better at Full HD range, but individual pixels may still visible at normal viewing ranges and in particular contexts. It's not until QHD resolutions and higher that PenTile starts becoming less of an issue.

Color shift. This is the second fundamental problem of OLED displays. OLED displays traditionally have had excellent brightness and contrast, which means that the displays don't lose their color contrast as viewing angles change. On the other hand, they suffer from color shift, meaning that the display's color tone or tint shifts as the angle changes.

Some OLED displays are better than others in this regard. For example, Samsung's AMOLED displays used to suffer from a high amount of color shift, but the company has worked to gradually reduce the effect. With each new generation, the color shift has become less pronounced — but it hasn't been eliminated. Samsung's latest AMOLED displays, seen in phones such as the Note 8, still suffer from slight color shift at oblique angles. It's noticeably better than AMOLED displays from 2012/2013, but not dramatically improved from the Galaxy S7's display, for example.

On the other hand, LG's P-OLED display tech, seen in the V30 and the Pixel 2 XL, suffer from much more obvious color shift. The displays develop a blue-tinted color shift even at minute angle changes, which is reminiscent of Samsung's 2012/2013-era displays.

Is color shift a major issue? The prevailing opinion is that it's a major issue on P-OLED displays, but "not a big deal" for most AMOLED displays. However, in our view, the next major step forward is completely eliminating color shift. Color shift reduces color accuracy if you don't watch the display head on. Also, when multiple people are viewing a display at the same time, color shift prevents a consistent viewing experience.

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Image burn-in on the Google Pixel 2. Source: The Verge

Aging. Another unfortunate characteristic of OLED displays is that they tend to age faster than LCDs. OLED displays suffer from two aging problems: Image retention (short-term) and display burn-in (long-term).

Image retention is temporary in nature, and occurs when part of the onscreen content is superimposed or "stuck" on the display. The problem is more common in LCDs (particularly in the Quantum IPS displays in LG's flagship smartphones), but it occurs in OLED displays, too.

More commonly, OLED displays suffer from burn-in. It appears in the form of permanent discoloration in areas on the display, and it's most commonly found in areas that remain static for a long time, such as the navigation and status bars on Android phones.

The time taken to develop burn-in is normally several months, and years in the best cases. However, burn-in is a highly variable phenomenon. Some users have reported permanent burn-in even after only a few days or weeks of use, even with smartphones that have the latest AMOLED displays from Samsung (such as the Galaxy S8). Users have also reported burn-in occurring after a short period of time on the P-OLED displays used in the LG V30 and the Google Pixel 2 XL.

Is there any solution for the burn-in issue? Again, manufacturers can mitigate it, but they can't solve it — it's an inherent characteristic of current-generation OLED displays. OEMs often mitigate it by using white navigation bars, dimming the navigation bar buttons, and making other software tweaks such as slightly-moving clocks in always-on displays. Samsung, Apple, and Google have all said that they're using software to fight burn-in, but all three have stated that burn-in is unavoidable. Simply put, OLED display quality permanently deteriorates after a few months' regular use (though not to substantial degrees in that timeframe).

One of the reasons why burn-in occurs is the organic nature of the LEDs in OLED displays — and the blue subpixel ages the fastest, as previously mentioned. MicroLED is a technology that can theoretically solve the issue by combining inorganic LEDs with OLED's subpixel technologies, but it hasn't been commercialized yet. In the near future, OLED will continue to be characterized by permanent burn-in unless in lieu of a  breakthrough.

Power efficiency at high APL. As explained in the terminology section, display brightness in OLED is variable, because it decreases with high Average Picture Level (APL) and decreases with low APL. Power efficiency in OLED is related to the APL of the content seen on the display.

At low APL (<65%), OLED is more power efficient than LCD, according to DisplayMate. That means that if the content on the display doesn't have a lot of white backgrounds, it will draw less power. That's important for media content such as videos which don't have predominant white backgrounds, where more sub-pixels light up to combine into the resulting white light.

On the other hand, web content typically causes OLEDs to draw more power because webpages predominantly have white backgrounds, and thus high APLs. (It's worth noting that the average APL in Android 5.0 Lollipop's UI was found to be 80%, according to Motorola).

Here's the deal: For tasks like web browsing, LCD will almost always be more power-efficient than OLED, despite the substantial emitter efficiency improvements in the most recent generations of OLED. OLED is closing the gap in high APL, and has already overtaken LCD in low APL. It's not completely there yet, but it isn't far-fetched to expect OLED to be more power efficient than LCD in high-APL scenarios in a few years' time.

Now that we've taken a brief look at the issues affecting both OLED and LCD display technologies, let's now consider the misleading specifications bandied about by OEMs regarding display quality.


Misleading specifications in smartphone displays

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Samsung's Galaxy Note 8.

According to DisplayMate, the Galaxy Note 8's display can get as bright as 1200 nits. However, that figure only applies to the auto brightness boost in sunlight. At 1% APL, which means that the display is showing a full-screen, nearly-black background, the Note 8's display can reach 728 nits with the brightness cranked up manually. Its true brightness, though, is 423 nits at 100% APL in Adaptive mode. There's obviously a huge discrepancy between the two numbers, and it's misleading to promote the 728 nits figure as a feature of the Note 8 without adding the necessary qualifying information.

In terms of contrast, manufacturers tend to advertise a deceptively high dynamic contrast. Static contrast is often lower than rated contrast, which is a problem that affects LCDs (thanks to their true blacks, OLEDs don't have contrast issues). Dynamic contrast tends to be much  higher than static contrast, but that's not of much use to the average user  Then there's the fact that static contrast figures don't account for environments with high amounts of ambient light. At that point, real contrast decreases to 100:1-200:1, a massive difference from the rated contrast of the display.


The supply side of the equation

OLED displays can achieve great image accuracy, and they're increasingly in demand. But is the supply up to scratch?

The answer is: Not at this time. The display manufacturers of note in the LCD space are many, and they include Japan Display (JDI), Sharp, LG Display, Tianma, BOE, and others. However, when it comes to OLED technology, Samsung Display occupies a dominant position in the market. LG Display notably started selling P-OLED displays in 2017, and the Chinese manufacturers such as BOE are gearing up to manufacture OLED displays as well. But Samsung Display has the advantage of being multiple years ahead of the competition.

In the past, Samsung Display used its position to sell n-1 AMOLED displays to other OEMs and keep the best current-generation AMOLED panels for Samsung Electronics' mobile division. Even today, few smartphones have 18:9 WQHD+ (2880×1440) AMOLED displays. Devices like the Huawei Mate 10 Pro and the OnePlus 5T have a 6-inch Full HD+ (2160×1080) 18:9 displays. Even though those displays are current-generation panels, they're lower in resolution. If companies are willing to pay more for OLED panels, of course, Samsung Display will happily supply them with its highest-quality AMOLED technology. One example is Apple, which has significant leverage in the industry. The company demands top-quality displays from its supply sources, and the OLED display in the iPhone X is no exception.

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Samsung Display's revenue growth. Source: Display Daily

The iPhone X's display is said to be a custom-built panel designed by Apple and manufactured by Samsung. It has a different aspect ratio (19.5:9), resolution (2436×1125), and pixel density (458 PPI) than the displays in Samsung's smartphones.

Because the iPhone X is a high-volume product, demand for OLED displays is such that Samsung Display is nearly unable to fulfill it. The company supplied about 50 million OLED panels to Apple in 2017 for the iPhone X, and is expected to increase the number for the next iPhone. It could lead to a shortage in the OLED display market — most of the AMOLED displays being supplied are headed to Apple and not to Android OEMs.

Competition in the OLED is one solution. LG Display previously used P-OLED displays in its G Flex smartphone series, and entered the OLED display business again in 2017. Google signaled its interest by entering into a deal worth millions of dollars to use LG's P-OLED displays. Apple, too, has shown interest in the past.

P-OLED displays aren't competitive with AMOLED displays yet, but LG Display could close the gap in 2018 and beyond. That'd only be good news for the industry.


Final words

Over the course of this article, we have seen just how complex the field of display analysis is. Many display experts say that you should never judge any display subjectively. However, for most people, subjective assessments can still be useful — especially considering the fact that it's very difficult to set up an objective testing workflow. The thing to keep in mind is that before passing judgement, users should have prior knowledge of smartphone display technologies in order to prevent misinformation from coloring their opinions.

Folks have different subjective preferences, of course, and that's fine. Many prefer saturated colors that are objectively inaccurate. Others prefer accurate color modes that are calibrated with respect to the sRGB or DCI-P3 color spaces. Some prefer Quad HD resolution, while others are perfectly happy with PenTile Full HD resolution in OLED displays. Choice is good when it comes to smartphone displays, and both display manufacturers and smartphone vendors should respect it.

Here's the takeaway:  LCD and OLED have their advantages and shortcomings, and both have progressed with different trajectories. It's likely that OLED will remain the technology of  choice for smartphones in the next few years, but for now, issues such as PenTile, color shift, and burn-in hold the technology back from achieving a flawless user experience. The supply side needs to be improved, too, before it becomes viable at low-end device ranges.

We've come a long way from the first touchscreen smartphone displays in 2007, but there's quite a way to go.


 



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