OLED Displays and the Monitor Market

Simon Baker, 3 July 2020

 

 

 

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Introduction

When you read about any display nowadays, one term you can’t avoid hearing about is OLED. An Organic light-emitting diode (OLED or Organic LED) is a light-emitting diode in which the emissive electroluminescent layer is a film of organic compound that emits light in response to an electric current. This organic layer is situated between two electrodes; typically, at least one of these electrodes is transparent. The OLED pixels emit their own light at a sub-pixel level meaning they do not need an additional backlight unit like a traditional LCD display would. Each sub-pixel emits white light which is then passed through a passive colour filter to produce red, green and blue. If you want to display black you can simply turn off the sub-pixels so they omit no light.

OLEDs are used to create digital displays and have become quite widely used in the TV and Smartphone market. OLED TV’s are known for their excellent multimedia performance, with very dark blacks, fast response times and excellent per-pixel local dimming.


Image courtesy of LG.com

OLED has not however yet made any real impact in the desktop monitor market, and LCD panels are still the only real choice in this segment. But why is that? We will look in this article at the strengths and weaknesses of OLED technology, at the few attempts manufacturers have made to release OLED options in the desktop monitor space, and also consider whether buying a modern OLED TV would be a good alternative for a desktop monitor. We have spoken to many of the leading display manufacturers to get their thoughts and comment on this article including Acer, AOC, Philips and BenQ.


Image courtesy of JOLED
 


OLED Strengths

  • True black

  • Infinite contrast ratio

  • Per-pixel level local dimming

  • Superior HDR performance

  • Faster response times

  • Thinner and lighter

  • Wider viewing angles

 

Black Depth and Contrast


Image courtesy of LG.com

OLED panels are well known for their excellent black depth capability. Because each pixel is individually lit, when it is told to display black it can turn fully off the pixel and therefore produce a true black. This is different to an LCD display where a backlight is shining through the LCD layer, and when black is shown the pixel has to try and block out that light behind it as best it can. The backlight unit on an LCD display Is still shining and so you get varying success of blocking that light out and creating a black image. This varies by panel technology as we’re sure you know, with VA panels for instance being much better at blocking out the light when displaying black and so producing deeper black depths than IPS or TN Film panels. Even the best VA panels cannot offer a contrast ratio any better than around 5000:1 because the backlight is still turned on and shining through the LCD panel. Some modern backlight dimming technologies such as “Full Array Local Dimming” (FALD) can help improve the active contrast ratio, which we will talk about in a moment in more detail.


Image courtesy of Sony.com

With an OLED display capable of turning a pixel fully off when it displays black, this creates basically an infinite:1 contrast ratio between bright areas of the screen and black (off) areas of the screen. In high contrast scenes this produces incredible detailed and accurate pictures, as well as allowing for great shadow detail. It is also particularly beneficial in darker ambient light conditions and night time viewing.

 

Local Dimming and HDR Performance


Above: simulated images of local dimming, showing blooming on the LCD screen and less detail in darker scenes. Image courtesy of LG.com

The other major benefit of OLED being able to turn off each individual pixel fully is that it can allow excellent per-pixel local dimming for HDR (High Dynamic Range) content. This offers vastly superior performance to LCD panels and can create a “true” HDR effect. At least from a local dimming point of view.

On LCD panels any local dimming has to be done in regions or zones from the backlight. These zones vary in sizes depending on the technology used. Although keep in mind also that many monitors including all those advertised as supporting VESA DisplayHDR 400 don’t even have any local dimming capability! Anyway, on LCD panels this local dimming backlight technique can often help improve the perceived contrast ratio across the screen as a whole and allows some areas of the screen to be brightened while others are dimmed. The actual quality of this local dimming is largely impacted by the number of local dimming zones the backlight has available. Some LCD screens only have a hand full of zones, perhaps 8 or 16 for instance across what could be a pretty large display area, and the backlight is situated at the edges of the screen normally. Turning one section off can dim that area of the screen but it can only go so far towards improving the contrast ratio because the zones are so large.

Some far more expensive LCD backlight options called 'Full Array Local Dimming' (FALD) are available as well, but are reserved for very high end and expensive monitors at the moment. These FALD backlights will typically have hundreds of zones (e.g. 384 zones on the 27" Asus ROG Swift PG27UQ, or 512 zones on the 35" ultrawide Asus ROG Swift PG35VQ we've reviewed). Some 'Mini LED' backlights are also starting to appear now as well, which basically extends the number of local dimming zones further, up to over 1000 for a screen of similar size (e.g. 1152 on the forthcoming 32" Asus ROG Swift PG32UQX and Acer Predator X32 gaming displays).


Above: illustration of additional HDR "stops" thanks to improved black depth and contrast on OLED. Image courtesy of LG.com

In general, the more local dimming zones the better. This allows for more finite control over the content shown on the screen, allowing the backlight to dim smaller areas while also brightening others. This can help create better local contrast ratios between different areas of the screen. “Blooming” is a problem though on all these LCD local dimming techniques. It is where there is a bright halo around an object on the screen, more than there is supposed to be. For instance you might have a small comet on a dark sky as in the simulated images above, but there may be a halo of brightness around this comet where blooming is visible. This is a result of the backlight dimming zones, where they are not small enough to only brighten the comet on its own, and instead have to brighten the full zone that it is in. In theory the more zones there are, the better, as each zone is then smaller and so can control a smaller area of screen. This blooming effect will always be an issue though on screens dimmed in this ways, until the zones get sufficiently small enough to control the content in sufficiently small areas. For LCD panels, that currently means adding more dimming zones, through Mini LED or future Micro LED backlights even. Some panel manufacturers such as Innolux are investing in development of Mini LED panels with >10,000 dimming zones, and even their 'MegaZone' backlight with >2 million dimming zones. These have yet to appear in any monitor though, although could represent a decent step forward when it comes to local dimming on desktop displays.

On OLED panels because each pixel is individually lit, each one can be dimmed on its own (and turned off to true black if needed). This means that for HDR content every single individual pixel can be controlled as intended, meaning not only amazing contrast ratios but also freedom from all blooming issues. This is one of the primary reasons why OLED is so popular for modern HDR console gaming and movies in the TV space.

 

Faster Response Times


Image courtesy of LG.com

OLEDs also have a much faster response time than an LCD which can help avoid motion blur, as well as allow support for higher refresh rates in the future. Because OLED pixels combine the light source and the color in a single diode, it can change states incredibly fast. By contrast normal LCD displays use a backlight unit to produce brightness, and tiny LCD “shutters” to create color and control that light output. While the backlight brightness can be changed in a near instant, LCD pixels are by their nature slower to respond to state changes. Using "overdrive" technologies, the fastest modern LCD's can reach response times around 1ms G2G in the best case without introducing a lot of overshoot artefacts in doing so. If you're read some of our reviews you will realise though that this is really the "best case" response time, and on average the response times will be slower. Somewhere around 3 - 5ms G2G is a fairly good result for an overall LCD panel at the moment. According to LG, OLED response times are up to 1,000 times faster than LCD, putting conservative estimates at under 10 μs (0.01 ms), although some of their modern TV's such as the new LG CX48 are advertised with a more conservative (but likely realistic overall) "1ms" figure.

Having super-fast response times isn't the whole picture though when it comes to motion clarity and gaming performance. OLED displays are still subject to the perceived motion blur the human eye sees from a sample-and-hold display like this (something talked about more in our article here). While response times are important to ensure solid performance, it is the displays refresh rate that has a more direct impact on the motion blur you experience and see on these kind of screens. A 60Hz OLED display with 0.01ms response times will still look more blurry and with much poorer motion clarity than a 120Hz LCD display with say 5ms G2G response times. The response times need to be consistently and reliably fast enough to keep up with the refresh rate and frame rate demands, but it's the refresh rate that really has the more significant impact on motion clarity and gaming experience.

On current LCD panels a good, consistent overall response time performance would be around 3 - 5ms G2G, without introducing lots of nasty overshoot or other problems. That's fast enough to accommodate refresh rates of around 200 - 330Hz. The higher you get, the more you are in to the realms of diminishing returns, but there are still benefits of reaching higher refresh rates as long as the panels and response times can keep up. Our friends over at Blurbusters will talk about the inspirational "retina refresh rates" of 1000Hz for instance, which they would consider to offer excellent motion clarity. LCD displays with their current response times cannot accommodate 1000Hz unless response times could be consistently and reliably 1ms G2G overall. While certainly nowhere near being necessary or available at the moment, OLED's super-low pixel transition time of 0.01ms could theoretically accommodate refresh frequencies approaching 100 kHz (100,000 Hz) if ever produced. So this is a technology more capable of reaching to those heights in the future.

Due to their extremely fast response time, OLED displays can also be easily designed to include a motion blur reduction backlight, with strobing to avoid the sample-and-hold behaviour seen on both LCD's and some OLED displays, which creates the perception of motion blur. The fast response times help ensure effective blur reduction when these strobed backlights are added. We explored this concept in a lot more detail in our article talking about motion blur reduction backlights for those interested in learning more.

 

Thinner and Lighter


Image courtesy of LG.com

Because an OLED panel does not need an added backlight unit, they can be thinner and lighter than LCD counterparts, offering potentially sleeker and slimmer screens for wall-mounting and generally improved aesthetics.

 

Wide Viewing Angles


Image courtesy of LGdisplay.com

OLED TVs can be viewed with no luminance degradation at drastic viewing angles, up to ~84 degrees. This is a lot higher than LCD displays which show more noticeable luminance degradation from an angle, although this does vary by panel technology of course. For LCD panels IPS technology can show pretty wide viewing angles, with VA technology being a little more restrictive and TN Film being a lot more restrictive.

 


OLED Weaknesses

  • More limited brightness

  • Lifespan

  • Colour shift

  • Dark Spots

  • Image retention and burn-in

 

Limited Brightness


 Image courtesy of LG.com

Because OLED pixels are individually lit, it is not as easy to make them as bright as an LCD display where a large backlight unit can shine through the panel. You also need to keep in mind the potential impacts to lifespan and image retention discussed below when it comes to brightness levels. As a result, OLED panels struggle with peak brightness relative to LCD displays. For example Samsung claims its QLED TV range (Quantum Dot LED displays with a traditional backlight unit) can deliver brightness levels of 1,000 - 2,000 cd/m2 and colour reproduction of more than 100 percent of DCI-P3 reference, which is the colour standard used by Hollywood films. Samsung has also been keen to promote the concept of colour volume, which is a combination of a display’s peak brightness and its colour reproduction. The reason for this is that QLED’s inherent brightness results in a larger colour volume when compared to OLED, which struggles to reach even 800 cd/m2of peak brightness. As an example one of LG's latest OLED TV's was tested by Flatpanelshd.com and reached 744 cd/m2 peak brightness in HDR.

 

You can also see how this brightness comparison plays out by looking at VESA's 'DisplayHDR' certification levels, which are separated and distinguished by the peak brightness level. They have certification levels for LCD displays that offer peak brightness support of up to 1400 cd/m2 (DisplayHDR 1400 level) but for future OLED displays in this scheme they only currently account for peak brightness of up to 500 cd/m2.

 

OLED is certainly improving over time in its ability to support higher peak brightness levels, and some may argue that because of the true black level, and incredibly HDR control it isn't really needed as much anyway. The overall HDR effect is still greater on a decent OLED thanks to the extreme contrast ratio, even if the peak brightness isn't reaching as high. Still, to truly support HDR content standards the ability to be able to reach higher peak brightness for certain scenarios is desirable.


Lifespan

One of the biggest technical problem for OLEDs is the limited lifetime of the organic materials. The brightness of OLED elements directly correlates to the strength of the current being applied. OLED lifespan decreases as current increases and current increases with higher brightness output. This might present potential concerns for viewing brighter content, including HDR with higher peak brightness over time. An article over at Techhive.com discusses this in more detail and is worth a read. A US Department of Energy paper shows that the expected lifespan of OLED lighting products goes down with increasing brightness, with an expected lifespan of 40,000 hours at 25% brightness, or 10,000 hours at 100% brightness.

 

Some manufacturers have attempted to get around this by introducing brightness regulation features to their OLED displays. For instance LG upset buyers of its 2018 OLED TVs by releasing a firmware update that increased the extent and speed with which bright images were dimmed down (as covered here at Forbes). LG confirmed  that this was ‘intended to reduce consumer discomfort in situations where temporary image retention can occur in certain viewing conditions’.

 

An LG claim in 2016 states that their OLED TV's had a lifespan of 100,000 hours, up from 36,000 hours claimed 3 years earlier in 2013. That's 10 hours a day for 27 years. Clearly advancements have been made in this area. You do need to keep in mind that this is a long slow decay though to 50% brightness which can be very noticeable, so it's not the full picture. OLED hasn't been around enough to put any of these claims to the test properly, but some extensive testing though from Rtings.com revealed at least that "after more than 5000 hours, there has been no appreciable change to the brightness or color gamut of these TVs." Lifespan and brightness over time should be fairly good nowadays, but is generally still considered a concern for the technology.
 

 

 

Colour Shift

 

OLED life-span is particularly problematic for the blue shades in fact. Although old now, one 2008 technical report gives some context and showed that after just 1,000 hours (around 18 weeks if used 8 hours per day), the blue luminance of the OLED panel degraded by 12%, the red by 7% and the green by 8%. In particular, blue OLEDs historically have had a lifetime of around 14,000 hours to half original brightness (5 years at eight hours per day) when used for flat-panel displays. With colours potentially degrading at different rates this can lead to colour shift and inconsistencies over time which is a problem.

 

Because the blue OLED degrades at a faster rate to the other colours, this can also lead to yellowing of the image over time. Some manufacturers like LG have gotten around this by using White OLED's ("WOLED" or sometimes "WRGB OLED"). LG don’t actually use true blue, red, and green OLED sub-pixels. Instead, they use white (usually, a combination of blue and yellow) sub-pixels with red, green, and blue filters on top. This can have an impact on brightness and so LG also then add an additional white sub-pixel to compensate as shown below. Back when Samsung were dabbling with OLED around 2013 they favoured a different approach where the size of the blue OLED was increased instead to compensate. Samsung later dropped OLED production in 2014 in favour of pushing traditional LCD displays and Quantum Dot LED screens, until more recent announcements that they are going to look in to OLED again in the future.
 

 

 

 

LG's WOLED approach is still their method for overcoming colour shift challenges in their OLED TV's. This has many advantages when it comes to large panel manufacturing and wear levelling, but filters also block light and reduce brightness hence the need for the additional white sub-pixel. This additional sub-pixel also adds to the challenge of improving pixel density further as overall the structure is now larger in size.

 

 

 

Dark Spots

 

Another challenge for OLED displays is the formation of dark spots due to the ingress of oxygen and moisture, the presence of impurities and also related to the high current intensity. These factors can all be responsible for degrading the organic material over time whether or not the display is powered. These can often form at random and sometimes even after only short periods of time.

 

 


Image courtesy of Sony.com

 

Image Retention and Burn-In

This is perhaps the most well-known risk and challenge with OLED technology. "Image retention" is when you are left with a ghost image on the screen where certain images are stuck or retained even when the image changes. This might be temporary and may gradually fade in time, or with the screen turned off for a while. However there is a risk that if this become too severe it might result in permanent "burn in" of the ghost image, leaving permanent traces of images or graphics on your screen.

While there have certainly been improvements in this area over the years, it is still very much a concern for display manufacturers. Each of the leading manufacturers we spoke to all told us that image retention and burn-in risk were a concern with trying to bring OLED to the desktop monitor market where usage types are generally different from the TV market (more on that in a moment).

OLED technology still has a risk of this problem, something that generally doesn't impact LCD screens. You can tell that it is still a concern, as the instruction manuals you get with every OLED TV will tend to include statements explaining first that image retention is an issue for OLED TVs, and second, what precautions you should take as the owner to avoid image retention happening. You can see an example of this on the right from a Sony OLED TV instruction manual.

LG, one of the main OLED manufacturers in the TV market also have a specific page on their OLED TV website dedicated to how to prevent image retention, and the technologies they've added to their screens to help prevent it or remove it. Clearly this issue is at the fore-front of OLED manufacturer's minds.

The burden of trying to prevent this from happening also seems to be quite firmly on the user too, with guidance to be careful of the content they view, how long they view it for, and being directed to make use of image-saving features that are part of the screen. The other issue is that OLED TV warranties will generally not cover image retention problems, and it is considered a user-fault if something does appear over time.

Prevention Measures

LG talk on their website about how they "address any risk of Image Retention that may occur when consumers are using the technology out of normal viewing conditions (i.e. when a static image is displayed for an extended period)". They go to explain that to prevent and reduce the occurrence of Image Retention, LG OLED TVs provide a variety of technologies as listed below.

  • Screen Shift - This technology reduces the potential of retention when the screen image is fixed for a long time. Screen Shift moves the pixels of the static area.

  • Logo Luminance Adjustment - This technology detects on-screen logos and reduces the luminance in the affected areas.

  • TPC (Temporal Peak Luminance Control) - LG OLED TV's have technology to detect which stationary images pose a high risk of retention and adjust the pixel luminance accordingly.

Example manual guidance for Sony’s A1 OLED TV relating to Image Retention and Burn In Risks
 


The following are examples of images that may cause image retention:

  • Content with black bars either on the top and bottom and/or the left and right sides of the screen. (for example, Letterboxed,4:3 screen, Standard definition)

  • Static images such as photos.

  • Video games that might have static content in some part of the screen.

  • On-screen menus, programme guides, channel logos etc.

  • Static content from applications.

  • On-screen tickers, such as those used for news and headlines.

To reduce the risk of image retention:

  • Sony recommends that you turn off the TV normally by pressing the power button on the remote control or the TV.

  • Fill the screen by changing [Wide mode] to eliminate the black bars. Select [Wide mode] other than [Normal].

  • Turn off the OSD (On Screen Display) by pressing the / button, and turn off the menus from connected equipment. For details, refer to the instruction manuals for the connected equipment.

  • Avoid displaying static images with bright colours (including white), clocks or logos on any portion of the screen.

  • Set the picture settings based on the ambient conditions. The Standard Picture is recommended for home use and when viewing content that often displays the station logos, etc.

Recovery Measures

LG OLED TVs also support recovery technology for Image Retention that may occur when consumers are using the display out of normal viewing conditions. Their 'Pixel Refresher' feature automatically detects pixel deterioration through periodic scanning, compensating for it as needed. It also senses any TFT (Thin Film Transistor) voltage changes during power off to detect and correct pixel degradation by comparing it with a set reference value. Pixel Refresher is automatically operated when you turn off the TV after watching it for more than four hours in total. For example, if you watched TV for two hours yesterday and three hours today (more than four hours in total), Pixel Refresher will automatically run, deal with potential image retention issues and reset its operation time.

After watching for a total of 2,000 hours or more (five hours per day for a period of one year) the Pixel Refresher is automatically operated, and the function runs for about an hour once you turn off the TV. You may see some Vertical lines on the screen during this process, however, this is not a malfunction. It is designed to remove Image Retention by scrolling a horizontal bar down the screen. You can also start the feature manually if you detect any image retention forming. Sony’s advice on its own similar 'Panel Refresh' feature states that "The Panel refresh function may affect the panel. As a reference… do not perform it more than once a year, as it may affect the usable life of the panel.” Which does also beg the question how much impact these features have on overall lifespan and image quality.
 

Burn-In Testing

How much of a problem is image retention in real life? Rtings.com carried out some extensive image retention and burn in tests over the last couple of years with a range of TVs controlled by a microcontroller to repeat a five hour on and one hour off cycle four times per day. Retention preventing technologies like the 'Screen Shift' option were left enabled on all TVs, and 'Pixel Refresher' was also performed before each set of measurements taken on each TV. They set the TV's up to play real content (not test patterns), from live cable TV sources, video game clips or recorded sports. They have provided some interesting analysis based on these tests:

Original statement from 5 November 2018 (courtesy of Rtings.com): "After more than 5000 hours...long periods of static content have resulted in some permanent burn-in (see the CNN TVs), however the other TVs with more varied content don't yet have noticeable uniformity issues on normal content. As a result, we don't expect most people who watch varied content without static areas to experience burn-in issues with an OLED TV. Those who display the same static content over long periods of time should consider the risk of burn-in though (such as those who watch lots of news, use the TV as a PC monitor, or play the same game with a bright static HUD). Those who are concerned about the risk of burn-in should go with an LCD TV for the peace of mind."

They went on to provide a further update more recently on 31 May 2019: "The TVs have now been running for over 9000 hours (around 5 years at 5 hours every day). Uniformity issues have developed on the TVs displaying Football and FIFA 18, and are starting to develop on the TV displaying Live NBC. Our stance remains the same, we don't expect most people who watch varied content without static areas to experience burn-in issues with an OLED TV."

Rtings found that the brightness of the screen had an impact on image retention, with the brighter screens showing more severe burn-in. Also the red sub-pixel seemed to degrade fastest it seems in this area.

The crux of it is fairly obvious. Varied, dynamic and regularly changing content is unlikely to lead to any image retention or burn-in, even after very long periods of use as long as you're careful and make use of the included prevention measures. However, there is still a risk if content is more static, and this is where OLED in the desktop monitor market becomes a lot more of a challenge. We will talk about that more in a moment. We would encourage you to read the full report at Rtings.com for more information.

 

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Challenges with Development for the Monitor Market

So why haven't we seen OLED panels properly appear in the monitor market when they are more and more common in the TV space? We reached out to various leading monitor manufacturers for thoughts and input here including AOC, Philips, Acer and BenQ. There were 3 common themes from all the feedback we had, and explanations as to why OLED had not really made a dent in this market yet.

  1. It is difficult to manufacture and therefore expensive

    One of the key things to keep in mind here is that the pixel density of a desktop monitor is generally a lot higher than a typical OLED TV, and that's a challenge when it comes to manufacturing. Most OLED TV sizes are around 55" - 65" and above. Even the smallest OLED TV such as the forthcoming LG CX48 is an exception right now and is 48" in size with a 3840 x 2160 "4K" resolution. At best that gives a pixel pitch of 0.2767, or 91.79 Pixels Per Inch (PPI) which is the same as a 24" monitor at 1920 x 1080. That could be considered sufficient for a desktop monitor in terms of pixel density, but it is far from the norm. Most OLED TV's are much larger than this but still with the same 4K resolution in most cases which leads to a much lower pixel density.

    The challenge with desktop monitors is that the pixel density will often need to be higher than this because you are using it from a much shorter distance and need much sharper images as a result. This is especially true for use like CAD/CAM, design, medical imaging and even text/spreadsheet work. 27" monitors with 2560 x 1440 (108.79 PPI) and even 3840 x 2160 (163.18 PPI) are very common and the norm now for desktop monitors. At the moment it is easy for manufacturers to make mobile OLED panels despite their high pixel density as they are small in size; and it's easy for them to make TV OLED panels as they are large and generally have much larger pixels. The desktop monitor market is in the middle, with moderately sized panels needed in the range of 24 - 34" commonly, but with high pixel density. That's where the manufacturing challenge is at the moment. This results in a very low yield rate (how many good samples there are in a batch) which makes them expensive to produce. You have to account for a large buffer for bad samples and faults in a production run to get to the desired volume which adds to the overall cost. Until the panels are easier to produce and  yield rate is improved significantly it is unlikely that they would become affordable enough to be considered mainstream in this market.

    When OLED is used for mobile phones and TV's it is sometimes easier currently to justify the relatively high price point as there are other "things" within the product offering besides just the panel. While the OLED panel could well make up the majority of the cost, being able to offer the buyer the rest of the mobile phone features and benefits can help somewhat mask that high retail cost relative to alternative phones. Likewise with TV's where you often have more built in capabilities and features for a more all-round functional device. In the desktop monitor space it's pretty much just the screen, so it's harder to sell additional value in the overall product and it's harder to mask that high panel cost.

    We also need to keep in mind that Chinese manufacturers have already invested heavily over the years in LCD production and plants, and it can be an expensive risk and investment to switch this to OLED production. Particularly when LCD panel production is very stable, has a high yield rate and is very profitable. With panels being available widely from many manufacturers, in a wide range of sizes and options and at comparatively very low prices, it is hard for monitor manufacturers to ignore that.

    It might take Japanese or Korean suppliers to accelerate growth here more widely like we've seen with JOLED who are discussed below. We have seen recent announcements from Samsung Display though that they plan to close their LCD factories by the end of 2020 and instead begin focusing on their own OLED production. We know LG.Display already produce lots of TV OLED panels, so perhaps could also more easily switch to OLED production in favour of LCD in the monitor space - if they can solve the problems of more difficult production and low yield rates. All in all it will take significant investment in OLED production and plants to really venture in to the monitor market, and probably many years before they reach a level where the panels produced can really go mainstream. If you look back at LG's investment in OLED TV panels it took more than five years and billions of dollars in investment before the gamble paid off, and not until 2017 did OLED TVs reach mass-market price points. When they reached that point it allowed LG to knock Samsung off the number one spot in terms of premium TV sales but it took a lot of time, money and effort to get there.

     

  2. It is organic in nature and therefore has a finite shorter life expectation

    When it comes to life expectancy we have already talked above about the issues with organic material degradation over time, and the display manufacturers were quick to call out the problems with blue pixels in particular when discussing monitor development. While manufacturers like LG have helped get around this challenge in the TV market by using their White OLED solution with colour filters, this is not really physically or economically viable in the desktop monitor market where pixel density is generally higher and therefore pixels are of a much smaller size. With White OLED solutions being impractical in the monitor space, that leaves normal RGB OLED structures which then have the risk of colour shift, yellowing and blue degradation over time. With OLED pixels degrading at different rates over time this can lead to noticeable colour shift and inaccuracies. This is less of a problem on OLED TV's with constantly moving multimedia images and less of a need for accuracy, but for desktop usage colour accuracy is more important and necessary. A monitor based on OLED would probably need a reliable calibration function or device to help maintain accuracy over time, further adding to the production cost.

     

  3. Image quality for static images it not great and susceptible to image retention and burn-in

    You need to keep in mind the major difference between a TV and a desktop monitor - usage type. A TV is designed to show ever-changing images for movies, TV shows and gaming. A Desktop monitor on the other hand will be used  for a whole wide range of uses. Sure, it might be used for movies and games still but it will also more commonly be used in other areas including for office work, text rendering, photo editing, spreadsheets, internet browsing etc. An OLED can normally avoid image retention because the content is always being refreshed and changed. For desktop monitor usage this isn't really realistic or viable and so there is a much bigger chance of burning in the image. Just think about reading this article now where your Windows task bar and icons are static, parts of your desktop and browser and static and even the page on the screen is remaining pretty static as well.  Even in PC gaming you have to contend more with head up displays, maps and stats etc so there remains a risk there too. Manufacturers have been working on improving image retention on OLED in recent years and the latest stats and figures are promising. Despite this, each display manufacturer we spoke to said that image retention was still a consideration and a risk for using this technology in the monitor market.

 

We asked LG, the leading manufacturer of OLED panels and TV's for their thoughts, and they kindly provided us with the following feedback:

What will it take for OLED to really make its way in to the monitor segment? Do you see this happening or know of any plans?

It’s important that OLED technology is compatible with a monitor display without compromising computer user interface or any other features. That’s why so much research is being done on how best to harness OLED, and the benefits it provides. While OLED monitors are currently in the research stage, we are continuing to explore more flexible and different size displays for TVs – such as the LG CX series - helping to provide that stepping stone to the development of OLED monitors.
 

 

 


OLED Monitor Attempts To Date


Above: Dell UP3017Q, released for a short time and then cancelled

We have seen a very small hand full of desktop monitors released in the market over the last 3 - 4 years. All the way back in January 2016 we saw the Dell UP3017Q announced. This was a 30" size screen aimed at professional uses and part of Dell's UltraSharp Premium (UP) range. It offered a 3840 x 2160 resolution, 1 million:1 static contrast ratio, a 10-bit colour depth and a wide colour gamut covering 100% Adobe RGB and 97.5% DCI-P3. The response time advertised was also 0.1ms although the screen had only a 60Hz refresh rate. Brightness was somewhat limited at 300 cd/m2.

To prevent image retention, Dell incorporated a pixel shifting algorithm to prevent image burn-in. Given the shorter life-time of OLED a human motion sensor was incorporated to help turn off the display when not being used. It was originally touted for a March 2016 release, but then didn't appear in the market until around April 2017. This gives you some indication of the complexities of releasing a screen based on this technology too. It was available in the US at a price of $3499.99 for a very short period of time in low volumes and was then subsequently cancelled before it went in to mass production. It never made its way to Europe either, and by late June 2017, about 2 months after it was first available, it was withdrawn. There were some reports at the time that Dell scrapped it due to issues with colour shift when viewed from an angle. Some early adopters reported issues with the image burn-in prevention option creating a strobing function at 120Hz frequency which resulted in double images and distracting issues in many uses.


Above: Asus ProArt PQ22UC, one of only a couple of desktop monitors with an OLED panel released

Since then, the OLED monitor market has been lacking entirely. The only company so far who have been successful with recent OLED production for a reasonable monitor size has been JOLED.  They have managed to produce a 21.6” 4K OLED screen as used in high end, expensive professional models like the Asus ProArt PQ22UC (pictured above) and alternative Eizo Foris Nova 21.6"

These 21.6" sized screens are very small by today's monitor standards, although are at least a start in providing OLED in this sector. They are unfortunately very expensive though with the Asus model for instance retailing for a whopping $3,881 USD or £4,299 GBP (Amazon affiliate links) in the UK at the time of writing.

The Asus model had some impressive specs though with an RGB OLED pixel structure being used. It offered a 3840 x 2160 resolution, 1 million:1 contrast ratio, 10-bit colour depth and wide colour gamut covering 99% DCI-P3. It does have only a very low typical brightness though of 140 cd/m2, with a peak of 330 cd/m2 for HDR content showing again the challenges in this area. Asus offer some solutions for getting around the colour accuracy challenges. The PQ22UC comes factory calibrated with a dE <2, while the screen also supports hardware level calibration.

Although this is a professional range monitor aimed at creative professionals, Asus do still talk about the screens gaming capabilities in the marketing material. It’s bound to still attract some interest from gaming enthusiasts thanks to the OLED panel, promising fast response times, deep blacks and great HDR support. There is a 0.1ms response time spec which on paper makes it the fastest monitor in the market (as Asus like to state). While pixel response transitions may well be very fast here thanks to the OLED panel, the screen is limited to 60Hz only and doesn’t have the motion clarity of a high refresh rate screen, or any of the other gaming enhancements you might see from a normal gaming screen or support for variable refresh rates (VRR).

JOLED (Japan OLED) was established in August 2014 by Japan Display, Sony and Panasonic with an aim to become an OLED medium sized display producer (focusing at first on OLEDs for tablets, monitors, laptops and signage).

JOLED received an investment from the Innovation Network Corporation of Japan, a public-private investment fund, which still holds the majority sake, with JDI, Sony and Panasonic holding smaller stakes.

In October 2017 Japan Display has decided to halt its plans to turn its minority stake at JOLED into a majority one, and so JOLED started to seek external financing to support its plan to start mass producing OLEDs in 2019 at the JDI plant in Nomi, Ishikawa. In December 2017 JOLED started commercial shipments of 21.6" 4K OLED monitor panels from its 4.5-Gen pilot line.

JOLED Is using an ink-jet printing process, which (according to the company) may enable it to produce at a lower cost - around 30-50% cheaper compared to evaporation. JOLED is using Sumitomo's P-OLED materials. JOLED says that it is ”aiming for printing OLED panels to penetrate the market for medium-sized professional monitors”.

 


Modern OLED TV’s as Computer Monitors?


LG CX48 OLED TV

With the lack of any real options in the monitor market if you're after an OLED panel, many people are today turning to more readily available OLED TV options instead. There has been a good improvement in monitor-type functionality on OLED TV's in the last couple of years, with features like high refresh rate and VRR support appearing. Using an OLED TV for these uses has its pros for sure, and we are certainly not saying that some users won't find great value in this option. However, there are also plenty of cons. It's not as easy as the often suggested "just buy x OLED TV, it's cheaper and better" that you will often see suggested on internet forums. Here are some of the pros, cons and considerations for buying an OLED TV for monitor usage.

 

Pros - When an OLED TV could suit you well


 Image courtesy of NVIDIA.com

If you're looking for a monitor primarily for movies, HDR content and console gaming then getting and OLED TV could be a no brainer.

  • Larger size - These screens are going to be much larger than any desktop monitor and far more suited to this kind of content when viewed from a further distance. This provides a much larger screen area and improved immersion and allows you to use it with more viewers, and from a wider range of viewing positions thanks to the bigger format and also the excellent viewing angles OLED offers.
     

  • 4K Resolution support - the OLED TV will support 4K resolution for the latest Ultra HD content from games consoles and Blu-ray players too. If you really need it, and have the money to spend, 8K resolutions are even available.
     

  • Fast Response times - response times will be excellent (although refresh rate may be limited still) for reduced smearing and blurring, and far fewer problems with overshoot like you might see on some desktop monitors using LCD.
     

  • High Frame Rate (HFR) is available - some high end OLED TV's will also support high refresh rates nowadays, up to 120Hz. This will offer significant improvements in perceived motion clarity (even on OLED where response times are so good) and provide support for higher frame rates in PC gaming and next generation games consoles.
     

  • Bright and vivid colours -  thanks to the wide colour space offered, typically a high DCI-P3 coverage as standard.
     

  • Amazing contrast - the infinite contrast ratio will provide excellent black depth and shadow detail for darker content, and in darker room conditions, and will be vastly superior to LCD panels.
     

  • Amazing HDR performance - The per-pixel local dimming will provide vastly superior HDR to any current desktop monitor option as well, making it a truly excellent option for movies and HDR content.
     

  • Variable Refresh Rate now supported - this was a feature previously not available in the TV market, but an October 2019 firmware and driver update added NVIDIA G-sync Compatibility from some top end LG OLED TV's, allowing them to finally support this feature. Certainly a very welcome addition when considering PC gaming, especially where the screen can also support a high refresh rates and you are likely to need to worry about varying frame rates and performance when powering a screen at 4K @ 120Hz from your PC. FreeSync support is expected to be added for AMD graphics cards at some point as well to some OLED screens, and HDMI-VRR is available to support games consoles.

 

Cons - When an OLED just isn't right as a replacement

While some people might be primarily gaming or watching movies on their monitor, most people are buying a desktop monitor because they use it for a wide range of uses. This will include office-type work, internet browsing, photo editing, colour critical work, spreadsheets etc. A whole host of other uses that you need to take in to account when selecting a display, and plenty of uses that make selecting an OLED TV impractical and a poor choice.  You need to realise that while an OLED TV can offer exceptional performance for movies, HDR and games that doesn't fit the requirements niche that the majority of people need from a desktop monitor.



Above: the Asus ROG Strix XG438Q (LCD display) is impractical for most people as a desktop monitor, even at its comparatively small 43" size

  • The Size is impractical for many -The size of these OLED TV's in totally impractical for normal close up desktop usage for most people, even the smallest OLED options like the new 48" LG CX48 is too big really. That's just not a comfortable size for normal close up viewing positions and on a typical desk. Even "monitors" in 40 - 43" size that we've tested in the past such as the Asus ROG Strix XG438Q are not really comfortable for these uses in our opinion. You end up with a sore neck and constantly having to move your head around to see different areas of the screen. Sure, they might be ok if you can position it a bit further back than normal and have a deep desk, but for most people that's not practical for a desktop setup. The sheer size of an OLED TV is also impractical for many people in terms of how much space they have in a home office or bedroom, often being far too big for their desk or general PC space.


  • The pixel density is too low -  Most OLED screen sizes are around 55" - 65" and above. With a 3840 x 2160 "4k" resolution that gives you an 80.11 pixels per inch (PPI) density which is the equivalent of a 0.3171 mm pixel pitch.  That's about the same pixel density as a 27" 1920 x 1080 monitor, and those are often criticised for having too low a resolution when viewed up close as a desktop monitor (81.59 PPI, 0.3113 mm pixel pitch). You end up with larger pixels and less sharp text and images when viewed up close. The lower density is probably fine for gaming and multimedia where you won't notice it as much, but for general office use, text work, browsing, photo editing etc it's not great. You won't get the sharpness or image clarity that a higher resolution screen can offer. A 27" at 2560 x 1440 resolution is a very common option nowadays in the monitor market and will offer you a much better pixel density (108.79 PPI, 0.2335mm pixel pitch) for these kind of uses. Then there's also 4K 3840 x 2160 resolution monitors which offer even more dense pixel structures for sharper and crisper images that many people prefer. You won't get anywhere near this kind of pixel density from an OLED TV right now.

    Even the smallest OLED TV such as the new LG CX48 is an exception right now and is 48" in size with a 3840 x 2160 "4K" resolution. That gives a pixel pitch of 0.2767, or 91.79 Pixels Per Inch which is the same as a 24" monitor at 1920 x 1080 and so is improving the pixel density. As we said though, most OLED TV's are much larger than this but still with the same 4K resolution in most cases which leads to a much lower pixel density. The other aspect to this is that fonts might sometimes not look as good from up close from a typical desktop viewing position, and you will sometimes see fringing or some slight "bleed" from one colour to the next. Not something you'd see from a sensible viewing distance for a screen this size, but something to keep in mind if you are trying to use the screen up close as a monitor.

     

  • Image retention and burn in is still a risk - we won't repeat what we've said earlier in the article, but relative to desktop monitor LCD panels, image retention and persistent burn-in is still a concern when trying to use an OLED TV for these kind of uses, and a lot of static images.

     

  • Color drift can lead to colour accuracy problems - colour degradation over time is a more significant challenge on OLED panels as we've already talked about. This is less of a problem for multimedia and gaming on OLED TV's, but could present an issue for more general desktop uses - especially if you are doing any photo editing or colour critical work. You will need a reliable way to re-test and calibrate your screen over time to ensure continued consistency.

     

  • Setup may be less accurate and more limited in control - Another aspect to keep in mind here is that in the OLED TV market there may not be as much focus from manufacturers in providing what would be considered an "accurate" setup for typical monitor uses. The screens may be more set up for bright, vivid and colourful images for movies and games. Additional image processing measured may also be added to improve the appearance for typical TV uses, but which might not be ideal for desktop monitor usage. This may of course vary, but it's fair to say there's less focus on these areas in the TV space. There may also be fewer controls and options available for the user to improve things, and you may be missing some of the controls that a typical monitor might offer you to correct gamma, colour temperature etc. It's also likely that many will be missing things like an sRGB emulation option, and so you may be stuck with the full wide colour gamut that the screen offers. Again ideal for gaming and movies, but not good if you are wanting to work specifically with sRGB content in the desktop PC space.

     

  • Stands lack much functionality - A OLED TV stand typically won't offer much, if any ergonomic adjustment. You might perhaps get a bit of tilt, or maybe even side to side swivel if you're lucky. But most are too big to be practically moved around, and so stands don't offer much adjustment. This is fine for a TV setup, but might be more restrictive for a desktop monitor space, where perhaps you might need to view the screen from different positions for normal day-to-day use, then movies and gaming. The lack of a height adjustment might also be restrictive. Many OLED TV users end up buying separate mounting options to make the screen more usable as a desktop monitor which helps, but adds further to the cost.
     


 Image courtesy of LG.com

What about if you're just gaming all the time? Even if your uses are primarily for gaming, there are still challenges and considerations when considering an OLED for PC gaming:

  • Your PC gaming viewing position may not be practical - Playing a PC game is a different experience to a console game. If you're using a controller pad then you can sit a fair distance away from the screen and it should therefore be fine using a large OLED TV if you've got the space and a sensible place to sit. If you are using your mouse and keyboard from your desk and doing more typical PC gaming then you are going to be much nearer to the screen, when again things like size, pixel density etc come in to play.

     

  • Many OLED TV's will lack common desktop monitor gaming features - some modern OLED TV's are starting to offer features like high refresh rates and Variable Refresh Rate (VRR) support like NVIDIA G-sync. This makes them a more attractive option even for PC gaming. However, keep in mind these features are more commonly seen on the top-end models, and may not be included on other OLED TV's. Access to high refresh rates and VRR experience is less accessible than in the monitor market where it's been around for a lot longer and is available even on budget range models. Some OLED TV's will support high refresh rates like 120Hz (look for "HFR" - High Frame Rate being discussed), but this is not as high as you can get in the desktop monitor market where refresh rates of 240Hz are becoming more common. We are not talking about all the fake refresh rates of older TV's either, where interpolation is used for interim frames. Most people really dislike those technologies as it leads to the "soap opera effect" and doesn't look right in practice. True high refresh rate support for PC and next gen console gaming is only really available in a hand full of top end OLED TV's so far.

    You might argue that pixel response times are much better on OLED TV's, and they are, but don't forget that refresh rate has a direct impact on perceived motion blur. There's a significant difference going from 60Hz to 120Hz and so that's a very positive change in the OLED TV market. There is a smaller but still noticeable improvement when going higher like to 240Hz, so if you're after super high frame rate support for competitive gaming and older PC games, this is more readily available in the monitor space still.

    Variable refresh rate support like NVIDIA G-sync Compatibility has been added to some top end OLED TV's since October 2019 but again this is only on certain models, and in the more expensive range at the moment. Access to NVIDIA G-sync for your PC gaming is therefore more limited in the OLED space, while being more readily available from a wider range of screens and budgets in the monitor space. According to AMD.com their FreeSync support has not yet been added to any OLED TV, being available only on a range of Samsung QLED (Quantum Dot LED) screens at the moment. We expect this to change soon, but again FreeSync support might be limited to only certain higher end OLED TV's for now. If you're an AMD graphics card user, support for VRR might be more limited in the OLED TV space.

    Access to other gaming enhancements like frame rate counters, cross-hairs and the likes are also likely to be absent on OLED TV's if you like any of those on desktop monitors. Some OLED TV's will at least feature strobe backlight type features for blur reduction (commonly called "Black Frame Insertion" or BFI in the TV space) although again these might be reserved for only the very top end screens, or those with true high refresh rates. They are also sometimes limited in their operation, being only available at 60Hz for instance. You also cannot use these at the same time as VRR (G-sync/FreeSync), whereas in the monitor market some displays such as the Asus TUF Gaming VG279QM now have the ability to run both at the same time.

     

  • Input lag will be higher - while input lag has been a focus in the TV space for a while now, and things have definitely improved a lot, it will still not reach the super-low levels you see in the monitor market. Figures around 12 - 13ms are specifically advertised by LG for some of their more gamer-oriented OLED screens. That's fine for normal TV uses and console games, and is a big improvement over older screens or non-Game mode settings where input lag can commonly be around 100ms! But even in the best case scenario a 12 - 13ms range input lag is still pretty high relative to a good gaming desktop monitor. In fact it's the kind of figure that PC gamers will baulk at when selecting a monitor where figures of only a few milliseconds are very common. 


 Image courtesy of LG.com

  • Graphics card support is limited for PC gaming - While some modern OLED TV's are starting to offer features like high refresh rates and VRR support, these are not as readily accessible to your typical PC user as they are on desktop monitors for PC gaming. None of the OLED TV's offer DisplayPort input which is by far the most widely used video interface output on PC graphics cards. You will find these supported on a wide range of currently available graphics cards, including older generation cards. If you wanted to use high refresh rates and VRR from a desktop monitor its much easier as DisplayPort is widely used on those displays. More people can therefore have access to these gaming features without needing to invest at the same time in the latest and greatest graphics card, even if they've got an older card.

    If you want to use these features on an OLED TV to their full extent that you're going to need to wait for HDMI 2.1 to be readily available. You can use HDMI 2.0 but with colour sacrifice and chroma sub-sampling required to support the bandwidth properly which isn't ideal. HDMI 2.1 has yet to appear on any commercially available graphics card, but it will be coming at some point. That opens the door to using these features at their full potential on an OLED TV, but it means you need to account for upgrading your graphics card to the latest model at the same time. You don't have any real legacy support for older graphics cards if you want to use an OLED TV for high end PC gaming.

 

We asked LG, the leading manufacturer of OLED panels and TV's for their thoughts, and they kindly provided us with the following feedback:

What are your thoughts about the use of OLED TVs as desktop monitors – where do you see the pros and cons in that kind of setup for various uses?

OLED TVs have certainly transformed the viewing experience for consumers with the self-emissive display technology able to control light at the pixel level for the most realistic colours and an infinite contrast ratio. Most manufacturers have stuck with traditional TV model sizes (55 inch and above) which make it more awkward to integrate as part of a desktop. However, LG’s new CX model comes in a smaller 48-inches, heralding the future of mid-size OLED products to address growing demand for a quality display in a smaller size, suitable for those looking for TVs to fit their living space or those looking for a second TV without compromising picture quality.

In particular, there is huge demand for OLED products for serious gaming use. LG 48CX builds on its predecessors to pair superior picture quality with outstanding gaming features, including NVIDIA G-SYNC compatibility, perfectly-rendered graphics, and topline refresh frame rate. Now gamers can have both exceptional picture quality as well as the important gaming features including low input lag and ultra-fast response time. 
 

 


Conclusion

There is no doubting the fact that OLED technology can offer some incredible benefits and improvements over traditional LCD displays. They can offer a true black thanks to their self-emissive pixels, producing an infinite contrast ratio for incredible shadow detail and image quality. The fact the OLED pixels are individually lit means OLED can offer vastly superior local dimming performance to any available LCD option available at the moment, bringing out highlights properly, while being able to show a true black for an amazing HDR experience and dynamic range; all the while avoiding the dreaded blooming you get on other technologies. Response times are also super-fast, helping to produce smooth performance for fast moving content and improving motion clarity especially where modern OLED screens offer high frame rate support as well. These super-fast response times also open the door for this technology to support even higher refresh rates in the future to enhance the experience. Viewing angles are also great and help make OLED technology a great option for multimedia, movies, HDR and gaming.

OLED isn't without it's challenges though unfortunately and it is providing expensive and difficult to bring the technology in to the monitor space, where panels are smaller, pixel density is higher and the yield rate in production is low. For now desktop monitors seem to be restricted largely to the lower cost and mass produced LCD panels, although there are some ventures in to this market from manufacturers like JOLED which are a positive sign. To make OLED more viable in this space manufacturer will also need to be able to tackle some remaining limitations of the technology related to the life-span of the organic material, subsequent colour shift risks over time and of course the dreaded issue of image retention and burn-in. Significant improvements have been made to address these challenges in the OLED TV space, but they remain a potential bigger problem for desktop monitors due to usage patterns and the content viewed.

Some people may not want to wait, and there is always the option to buy an OLED TV now and use that as a desktop monitor, especially when you consider the cost of some of the higher end monitors appearing nowadays. With smaller OLED options like LG's new CX48 appearing it starts to bridge that gap a bit more, and a 48" sized screen is more viable as a desktop monitor than traditional 55 - 75" size ranges but probably still far too big for many people. Using an OLED TV as a monitor though isn't without its own challenges and it definitely won't be an option for everyone. 

 


Further Reading

Flatpanelshd.com OLED vs LCD Comparison article (Sept 2016)
Forbes article on lifespan and image retention (Dec 2018)
Wired.com QLED vs OLED Article (March 2018)
 

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