LG CX OLED

Introduction

The TV market is not really an area we follow at TFTCentral as we are focused primarily on desktop monitors. However, in recent times we have seen a growing number of people interested in buying a modern high end TV and using that as a monitor. The most common reason for this is the use of OLED (Organic Light Emitting Diode) technology, something that you cannot find in any mainstream or more affordable monitor line-up. OLED is becoming more and more popular as a TV technology thanks to its incredible contrast ratios, real blacks, super-fast response times and excellent per-pixel local dimming for HDR content. If you’ve not done so already, we would recommend a read through our recent OLED Displays and the Monitor Market article which talks a lot more about the strengths and weaknesses of this technology.

In years gone by, most OLED TV screens have been far too large for practical desktop monitor use, commonly being 55 – 77″ in size. Those who are interested in using an OLED TV as a monitor have also tended to be those primarily looking for a gaming and movie display, but until fairly recently these OLED TV’s have lacked some of the key features available from their gaming monitor alternatives. All that is beginning to change as LG, one of the key players in the OLED TV market and the producer of all the mainstream OLED underlying panels, have now released a smaller 48″ model which makes the size a little more reasonable and practical for desktop monitor use. In the last couple of years we’ve also seen technologies like high refresh rate (120Hz), Black Frame Insertion (BFI – a motion blur reduction method) and even variable refresh rate technologies like G-sync and FreeSync appear in this space. Suddenly not only are the screens a little smaller and perhaps more viable, but these screens are combining all the significant benefits of OLED technology with some of the key monitor gaming features that people look for. When you also consider that even the most recent OLED TV’s in this kind of size range are more modestly priced than some of the top-end desktop monitors, they become an attractive option to consider.

There are of course still challenges with using a screen like this for desktop use, and we talked about some of these in our article linked above. We wanted to take a look for ourselves though and experiment in using one of LG’s most recent OLED TV’s (the 2020 CX OLED) and putting it through our normal tests. This is not designed to be a review of the screen as a TV, so we won’t really be talking much about some of the TV features. We are instead going to put it through all our normal tests and analysis as a PC monitor and see how it holds up. The CX series offer specs including a 3840 x 2160 Ultra HD resolution, NVIDIA G-sync Compatibility, recently added AMD FreeSync support and multiple next generation HDMI 2.1 ports.

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Specifications and Features

Introduction and Range of Screens

There are four models currently in LG’s latest 2020 line-up which is their CX range (“C-10″ which is this year’s replacement to the previous C9 models). The specs and features are identical on all four models, with the only thing changing being the size, and therefore the price. They are available in sizes of 55″, 65″and 77″ like the previous generation, but also now a 48″ model which is receiving the most attention as a potential desktop monitor. We should note that we are testing the 55” model (OLEDCX55) but the results and performance should be applicable to all sizes of this screen.

One thing to note also is that there are several different versions of the same models available in different regions, and even from different shops. For instance in the UK there is the OLED55CX6LA (available as an exclusive version from Currys) and the OLED55CX5LB (available from other places like John Lewis). These represent only minor aesthetic differences as far as we know, where the Currys model has a dark silver stand section and the other model has a light silver stand. The whole thing makes it a bit confusing when trying to buy one of these screens, but apart from a few minor differences like that, the actual screen, specs and performance are identical.

The screens are commonly referred to the CX48, CX55, CX65 and CX77 online by the way, so those are the model numbers we will stick to throughout this review. We will also talk more generically about the “CX OLED” as a series of screens.

Specs and Features run-down

The following table gives detailed information about the specs of the screen as advertised, looking primarily at the normal monitor-type specs we would consider. There are a very wide range of additional specs and features listed on LG’s website if you want to know more about the TV side of things.

The CX OLED offers a fairly limited range of modern connectivity for monitor usage with only 4x HDMI 2.1 ports offered for video connections. This is the newest version of HDMI which can support high bandwidths allowing for 4K @ 120Hz and 10-bit colour depth which is considerably beyond the capability of older HDMI 2.0 connections. There are, at the time of writing, a limited number of commercially available graphics cards though that support HDMI 2.1 although the first options have recently appeared from NVIDIA with their RTX 3080 and 3090 series. These are of course the latest and most expensive graphics cards in the range so you will need to keep in mind that you’d need to invest a considerable amount of money in a graphics card as well if you want HDMI 2.1. We will talk a bit later about the resolutions and refresh rates you can run on this screen even with a current HDMI 2.0 card.

There are no other common monitor connections available though on this screen such as DisplayPort or USB type-C. This might make connectivity more restrictive to many PC users, depending on your graphics card and available video outputs.

Above: Connections on the side section of the screen, back left hand side. Click for larger version

Above: connections on the back of the screen. Click for larger version

There are 3x HDMI ports located on the back left hand side of the screen which are fairly easy access, and a fourth port a little more centrally on the back of the screen. There are 3x USB ports on the screen although these are to show content on the display itself (like photos or videos). There is no USB upstream to connect it back to your PC so you can’t use them like you would a normal USB hub for connecting devices or storage as if it was part of your PC. There is also a headphone out connection for audio and an optical SPDIF connection. A LAN port is provided to allow usage of the Smart TV functions / applications / streaming services etc, as well as built in Wi-Fi if that’s likely to be easier to use for most people. There is also an antenna input and a satellite input for TV content. The screen has a built-in power supply and the power cable comes pre-attached to the back ready for you to plug in.

Below is a summary of the features and connections of the screen.

Design and Ergonomics

The CX OLED comes in a black and dark silver design. There are some very thin dark silver bezels around all 4 sides measuring only  2.5mm and then an additional 6.5mm black panel border before the image starts. Along the bottom edge to hide the monitor stand is a long silver metal section which slopes down towards you. On some editions of the screen this is dark silver, on others is it lighter in colour. It provides a sleek and attractive finished we felt and the screen looks attractive from the front and fairly minimalist.

The bezel is very thin on all sides as shown above. The screen has a glossy coating like most TV’s but this does not pick up reflections too badly. For PC usage if you have a window or a light source directly behind you this might cause some unwanted reflections though relative to a traditional anti-glare coating on most monitors. Keep that in mind. However, the glossy coating does help provide a sharp and clear image and helps the image “pop” a little more.

The back of the screen is encased in a dark silver plastic. There is a protruding lower half at the back where all the power boards, connections etc are contained. You can see from the side view photo below that the panel itself has an incredibly thin profile, and even with this section containing all the electronics, the overall profile of the screen is very thin. This measures ~46mm thick without the stand attached.

You can see from the above photo the connection sections on the right hand side (when viewed from behind) and on the back right hand side. The cables can be tucked in to the small removable plastic section you can see on the base of the stand to keep them tidy. We found this a little fiddly to re-attach once you have all the cables fed through to be honest, but it’s not the kind of thing you will need to mess around with much thankfully.

 Above:  side view of the screen with thin profile. Click for larger version

On the subject of the stand, we did find this particularly confusing and tricky to attach when we first opened the box. The provided instructions are a bit vague and confusing, and you have to first attach the long metal sloping section to the stand itself, and then attach that stand to the back of the screen. A tip: rest the screen on a couple of pillows to allow you to get it to the right height so you can attach the stand more easily to the back! This has to be screwed in to place but once attached it does provide a sturdy and stable base for the large screen, just with no ergonomic adjustments which is quite restrictive for a desktop monitor. If you would rather, you can also do away with the stand and use the provided 300 x 200 mm VESA mounting holes you can see on the back.

The stand provides no adjustments at all, like on most TV’s and so it is very limited as a desktop monitor. The screen is obviously very large, even with the smallest 48″ model so actually if you have it on a desk you don’t really need things like height adjustment. It just makes it pretty inflexible though overall if you want to also view the screen from a different position for gaming or movies or move away from your desk to a sofa or bed to watch a movie or play a console. To add more flexibility in positioning and adjustments you may want to consider a VESA wall mount for it if you can.

A summary of the ergonomic adjustments are shown below:

The materials were of a very good standard and the build quality felt solid. There was no audible noise from the screen, even when conducting specific tests which can often identify buzzing issues. The whole screen remained cool even during prolonged use.

Above: the included remote control

The OSD can be controlled through a few buttons located on the front bottom edge of the screen near the power LED, but there are very limited options and it’s not particularly easy to use either. You can turn the screen on/off, change the input, control the volume and the programme (channel) but that’s about it. The far easier option is to use the provided “Smart Remote” pictured above. This makes navigation quick and easy, and includes a virtual mouse pointer as well for simple navigation and quicker access, along with entering characters when typing in to on-screen keyboards and apps. The menu itself provides a wide range of options and features to play with. You can customise the settings for each HDMI input as well, and each one has multiple modes depending on whether it detects an SDR or HDR input (of various types). So you can easily set up the standard SDR mode for desktop for instance, and then have the settings more aimed at movie or game usage when an HDR input is detected. The menu was quick and easy to navigate, although we did feel that some of the advanced settings were a bit too deep in to some sections, requiring a fair few clicks to get to some of them.

Sound

The screen features integrated Dolby Atmos speakers which are considerably more powerful and capable than the kind of speakers you would typically find in a desktop monitor. This is certainly one big benefit with the screen being a TV. LG’s “AI Sound Pro” includes a range of modes that create a wide range of environments, including useful features like a mode to enhance voice quality and levels. For optimal sound you can also connect the screen to an external amplifier and speaker system using HDMI ARC/eARC, or even wirelessly using Bluetooth if you have suitable speakers. For other systems you can also output over the optical SPDIF connection although the pass-through of certain audio types will be more limited. Overall for desktop monitor use the sound system and speakers are far more capable here than you would get from a desktop monitor.

Initial Setup

We wanted to quickly cover some of the default setup options you should select when using this screen as a desktop monitor:

• In the ‘home dashboard’ you need to label the HDMI input in the settings section you are using with the ‘PC’ icon, and then name it whatever you want. This is the preferred option to use the screen in ‘PC mode’ although some of the OSD options are then unavailable. If you are primarily going to use the screen for movies or games from a PC you may wish to label the input with a different icon (not PC mode) and use some of the other preset modes then where a fuller range of OSD options are selectable. For our tests here, we did label it as PC.
   
• For gamers and those wanting to use G-sync and with minimal input lag you will want to turn on ‘instant game response‘ from the ‘picture menu’. The one issue we found with this is that in PC mode the screen always enables this setting. By default then the screen enters the ‘game’ preset mode which has a range of options pre-selected for reduced lag, and many that are not available to change. You can see our setup measurements in the game preset mode in later sections to decide if this is a mode you want to use. It’s likely to be optimal for PC gaming but you may want to make a few tweaks to some settings perhaps. You do seem to be able to change to other preset modes as well while still working with the instant game response mode activated but while this might give you access to some other options, it might not be as suited for PC gaming.
   
• Leave on HDMI Ultra HD Deep Color
  
• Turn ‘Energy Saving Mode’ to Off to avoid dynamic control of the screen’s brightness via the ambient light sensor (unless you want that on for movies or gaming perhaps at different times of the day)
  
• ‘Eye Comfort Mode‘ we left turned off, which provides some blue light reduction benefits which we will test a bit later on
  
• Within the chosen preset mode you’re using for PC connection (e.g. if using the ‘Expert (dark room)’ mode as recommended in our calibration section below, change the sharpness control to 0 – you don’t need the screen to artificially sharpen the image here as the PC provides the relevant resolution input at 3840 x 2160. If you want to sharpen movies etc you are probably better doing that with the software player on the PC than using the screen’s built in sharpening system
  
• Make sure the following are left turned off (many are off by default in some modes) within the chosen preset mode in the ‘Advanced Controls’ menu – Dynamic Contrast, Dynamic Color, Super Resolution
  
• In the ‘Picture Options’ menu we also turned off Noise Reduction, MPEG noise reduction, Smooth gradation, Real Cinema Motion Eye Care, Tru Motion – you may want to experiment for movie viewing or games perhaps, and we will look at some of these features a bit later on as well
  
• Leave the ‘Black Level’ setting at auto, and it will be dictated by the selected RGB output of your graphics card – which you want to ensure is set to full range RGB
  
• Further recommended calibration sections for SDR and HDR mode are included later on in the review

Panel and Backlighting

Backlight dimming at 100%, Calibrated and 0% OLED Light levels

The screen does not use PWM for backlight dimming which is great news and it can be considered as flicker free. There are some very minor brightness fluctuations every 8.33ms which are in sync with a 60Hz refresh rate. This is the same frequency even when running at 120Hz input, but the fluctuations in luminance are very minor. We measured only a 7.5% drop in luminance for these fluctuations, and these should not cause any issues though and you certainly can’t see this in practice.
 

Above: confirmation of the panel used in our tested 55″ CX model

Brightness and Contrast

This section tests the full range of luminance (the brightness of the screen) possible from the screen, while changing the brightness setting in the OSD menu. This allows us to measure the maximum and minimum adjustment ranges, as well as identify the recommended setting to reach a target of 120 cd/m² for comfortable day to day use as a PC monitor in normal lighting conditions. Some users have specific requirements for a very bright display, while others like a much darker display for night time viewing or in low ambient light conditions. At each brightness level we also measure the contrast ratio produced by the screen when comparing a small white sample vs. a black sample (not unrealistic full screen white vs. full screen black tests). The contrast ratio should remain stable across the adjustment range so we also check that.

Graphics card settings were left at default with no ICC profile or calibration active. Tests were made using an X-rite i1 Display Pro Plus colorimeter. It should be noted that we used the BasICColor calibration software here to record these measurements, and so luminance at default settings may vary a little from the LaCie Blue Eye Pro report you will see in other sections of the review.

Quick notes

• Energy Saving Mode = turned Off
• To change the brightness of the image = use the ‘OLED light’ setting
• Leave the OSD ‘brightness’ control at default
• If you want a brighter image for SDR you would have to change out of the PC input mode in the home dashboard

We turned off the ‘Energy saving mode’ which basically offers an ambient light sensor to dynamically control your screen’s brightness depending on your room lighting conditions. For the purposes of completing these tests we switched that to the ‘off’ state. The brightness of the screen should be controlled via the ‘OLED light’ setting which basically controls the intensity of the OLED pixels, akin to controlling the backlight on an LCD display. There is a separate ‘brightness’ control which handles digital white level adjustments but that will impact gamma and potentially contrast so should be left at default.

In SDR mode at the full brightness setting in the OSD the maximum luminance reached a fairly modest 260 cd/m². Not super-bright but certainly sufficient for close up desktop use as a PC monitor. This was for a small sample area of white being measured. Because the screen is OLED and it has built-in measures like an ‘Automatic Brightness Limiter’ (ABL) to help protect the lifespan of the organic material, if you run a full screen white test the maximum sustained brightness is lower at 158 cd/m². So if you are working with a lot of white/bright content on the screen you may find that the ABL feature kicks in and reduces the overall luminance somewhat.

Assuming a small sized sample measurement area there was a decent 221 cd/m² adjustment range in total, so at the minimum setting you could reach down to a luminance of 39 cd/m². This should afford you a low luminance option for working in darkened room conditions with low ambient light. An ‘OLED light’ setting of ~36 in the OSD menu is suggested to return you a luminance as close to 120 cd/m² as possible at default settings.

These tests were conducted in the default ‘Standard’ preset mode and in SDR mode. Note that with the input label set to PC, the setting for “peak brightness” in the OSD is greyed out and not available. That could normally be used to boost the maximum brightness of the display so if you want to reach brighter content for PC use then you might want to use an alternative input mode label. That might perhaps be useful for movie viewing or some gaming, but for close-up desktop monitor use the maximum brightness above is still sufficient. If an HDR input is detected (game or movie) the screen will switch to HDR mode automatically (subject to your software and graphics card) which will then enable the ‘peak brightness’ setting at ‘high’ and produce higher peak brightness for HDR content anyway.

We have plotted the luminance trend on the graph above. The screen behaves as it should in this regard, with a reduction in the luminance output of the screen controlled by the reduction in the OSD brightness setting.

Being an OLED panel each pixel is individually lit and so when it is asked to show black, it just turns itself completely off. This creates true blacks so at all brightness settings the minimum black depth is 0.00 cd/m². This in turn creates an infinite contrast ratio regardless of the brightness setting. No LCD panel can do this in the same way, and this is one of the major strengths of OLED technology. Far beyond what is possible from even VA technology panels in the desktop space.

Testing Methodology

An important thing to consider for most users is how a screen will perform out of the box and with some basic manual adjustments. Since most users won’t have access to hardware colorimeter tools, it is important to understand how the screen is going to perform in terms of colour accuracy for the average user.

We restored our graphics card to default settings and disabled any previously active ICC profiles and gamma corrections. The screen was tested at default factory settings using our new X-rite i1 Pro 2 Spectrophotometer combined with LaCie’s Blue Eye Pro software suite. An X-rite i1 Display Pro Plus colorimeter was also used to verify the black point and contrast ratio since the i1 Pro 2 spectrophotometer is less reliable at the darker end.

Targets for these tests are as follows:

• CIE Diagram – confirms the colour space covered by the monitors backlighting in a 2D view, with the black triangle representing the displays gamut, and other reference colour spaces shown for comparison. Usually shown as a comparison against the common sRGB space
• Colour space coverage volumes – we also measure using a piece of software called ChromaPure the colour space (gamut) volumes produced by the backlight in comparison to the sRGB, DCI-P3 and Rec.2020 colour spaces. sRGB is the most commonly used colour space so it is important to have a decent coverage from the screen here. If the colour space is >100% sRGB then the screen can produce a wider colour gamut, often reaching further in to the wider gamut DCI-P3 (commonly used for HDR) and Rec.2020 reference spaces.
• Gamma – we aim for 2.2 which is the default for computer monitors
• Colour temperature / white point – we aim for 6500k which is the temperature of daylight
• Luminance – we aim for 120 cd/m², which is the recommended luminance for LCD monitors in normal lighting conditions
• Black depth – we aim for as low as possible to maximise shadow detail and to offer us the best contrast ratio
• Contrast ratio (static) – we aim for as high as possible. Any dynamic contrast ratio controls are turned off here if present
• dE average / maximum – we aim for as low as possible. If DeltaE >3, the color displayed is significantly different from the theoretical one, meaning that the difference will be perceptible to the viewer. If DeltaE <2, LaCie considers the calibration a success; there remains a slight difference, but it is barely undetectable. If DeltaE < 1, the color fidelity is excellent.

Default Performance and Setup

Default settings of the screen were as follows:

ut of the box the screen was set in the ‘Standard’ preset mode and with the settings shown above. The image looked pretty cool (temperature wise) though and this is perhaps related to the ‘Colour Temperature’ setting of “C20” by default (Cool 20). The colours looked vivid and saturated and you could tell the screen offered a wide colour space/gamut natively. We went ahead and measured the default state with the i1 Pro 2. The CIE diagram on the left of the image confirms that the screens colour gamut (black triangle) extends a considerable way beyond the sRGB reference space (orange triangle), mostly in green and red shades. We measured using ChromaPure software a 132.1% sRGB gamut volume coverage which corresponds to 97.4% of the DCI-P3 reference and 6.9% of the Rec.2020 reference. LG don’t list a specific spec for this, only that the screen offers a DCI-P3 gamut – which it does. There is an sRGB emulation mode available in some of the other preset modes if you change the ‘Color Gamut’ setting in the OSD from ‘Wide’ to ‘Auto’. We will test that in a moment. The wider gamut here with more vivid and saturated colours is nice for gaming and movies which is the screen’s primary target usage given it’s a TV and we suspect many people will want to use it with a wide gamut anyway.

Default gamma was recorded at 2.1 average with a fairly small 7% overall deviance from the target, although you can see the gamma is a bit lower in lighter tones. White point was far too cool by a massive 62% being measured at 10,506k. This is going to be the main thing we need to try and correct for comfortable desktop use.

Luminance at the default 80% OLED light level was recorded at 186 cd/m² which is a bit too high for prolonged general use, you will need to turn that down a bit to get a more comfortable level for close up desktop use. The black depth was 0.00 cd/m² thanks to the self-emitting OLED panel and per pixel dimming and so this gives you an infinite contrast ratio – an obvious and major benefit of this technology. Colour accuracy measurements are comparing the produced wider gamut display colours against an sRGB reference which will always lead to differences. There was no sign of any colour banding when testing gradients which was good news, and only minor amounts of gradation in darker tones evident. If you can switch up to the higher 10-bit or 12-bit colour processing levels it can help ensure gradients are smooth, but this will depend on your resolution, refresh rate and graphics card (discussed more later on).
 

Cinema Mode Default Setup

We also tested the default setup of a couple of other preset modes. The cinema mode showed an overall better and more accurate setup for our targets. It still operated with the wide gamut (97.5% DCI-P3) but had a slightly more accurate gamma curve, and certainly a much better white point closer to our 6500k target. If movie viewing is your primary use for the screen alongside only some minor desktop work, then this might be a good mode to have as your default SDR preset mode. It’s also a good mode to use when the screen switches in to HDR mode so again if your primary HDR usage is for movies, maybe the cinema mode would be the best to use.
 

Game Mode Default Setup

The Game mode offers an sRGB emulation by default, restricting the wide native gamut and now covering 97.1% sRGB (which is 71.6% DCI-P3, and 51.4% Rec.2020). You cannot force-enable the wide gamut mode in this preset as the option is locked in the OSD menu. It is locked to ‘auto’ so should a wide gamut game/movie be displayed it should kick in to wide gamut mode. For desktop use it locks the screen basically with an sRGB gamut in this auto mode. Many other settings are also unavailable in this mode which is optimised for low input lag and PC gaming.

Thankfully the gamma curve is pretty good, but white point is now a lot cooler again, and the screen looks noticeably more blue than the ‘Cinema’ mode we’d just tested. You do have access to change the white point though to help correct that. With the screen now operating with an sRGB gamut we can take note of the dE figures which show a decent accuracy of 1.5 average which was pleasing and provided good default colour accuracy.

Expert (Dark Room) Mode Default Setup

The Expert modes in the menu give you access to change all the settings and options in the OSD and so are probably the best modes to use for desktop PC use. There is a bright room mode which has a default OLED light of 80, or a dark room mode which has an OLED light setting of 60. The latter seems better for close up desktop use so we will stick with that here and tweak the settings later on. You might want to use the Expert (bright room) mode to set something up for more distant viewing positions and movies or TV perhaps.

The colour gamut mode is available to select in this mode. At the default ‘wide’ setting we saw the same 97.4% DCI-P3 coverage as we’d measured in the ‘standard’ preset mode before.

You can change the gamut setting to ‘Extended’ or ‘Auto’ which both appear to offer a decent sRGB emulation. This covers a little more than the 97.1% sRGB (71.6% DCI-P3) we had seen produced in the ‘Game’ preset mode and we measured here a 105.0% sRGB coverage (77.4% DCI-P3). This significantly reduces the over-coverage in all shades, especially greens. This gives you the flexibility to work with sRGB content without worrying about complicated colour management workflows, so it was great to see the feature offered here even though it’s a TV. The gamma is a bit high by default in this Expert (dark room) mode but within the OSD menu the gamma setting is set at BT.1886, and we might have a better setup if we change that to 2.2 (tested in a moment). The white point was at least close to the target 6500k with the screen set by default in the ‘Warm2’ colour temperature mode here.

Optimal Settings Pre-Calibration

We also measured the screen after adjusting only the OSD controls, to obtain the optimal setup without a full calibration, and without the use of an ICC correction profile. This represents what could be achieved through just simple changes to the monitor itself, and also what you could expect when working with content outside of an ICC profile managed workflow. The early stages of our calibration software helped identity these optimal OSD settings.

 

It doesn’t really matter which preset mode you use, whether its the expert mode or the game preset. The same OSD settings above can be used in either to obtain an optimal appearance and colour setup. We stuck with the ‘auto’ gamut mode which produced an sRGB gamut, but if you would rather stick with a full wide gamut then you can change that setting to ‘wide’ instead. The other settings for gamma, colour temperature, RGB, OLED light etc are all still applicable and will help achieve an optimal setup for desktop use even without a calibration tool.

We switched to the gamma 2.2 mode which returned us a more accurate gamma for our setup at 2.3 (3% deviance from our target). The ‘Warm2’ colour temperature mode had returned a decent white point before, but we also tweaked the RGB levels in that menu by bumping the red up to a setting of 6 (from its default 0). This helped get the white point to basically spot on the 6500k target. The OLED light setting adjustment also allowed us to reach a much more comfortable level of brightness. The contrast ratio was still excellent here of course thanks to the OLED panel.

These optimal settings helped the screen look a lot better than out of the box, especially correcting the white point and brightness. Further calibration and profiling below will help improve things even further in the next section. The dE measurements can be considered here as well since we are operating with a standard sRGB gamut and with a dE average of 1.1 the colour accuracy after a few simple OSD tweaks was excellent.

Calibration

We used the X-rite i1 Pro 2 Spectrophotometer combined with the LaCie Blue Eye Pro software package to achieve these results and reports. An X-rite i1 Display Pro Plus colorimeter was used to validate the black depth and contrast ratios due to lower end limitations of the i1 Pro device.

The OSD settings were adjusted as shown in the table above, as guided during the calibration process and measurements. These OSD changes allowed us to obtain an optimal hardware starting point and setup before software level changes would be made at the graphics card level. We left the  LaCie software to calibrate to “max” brightness which would just retain the luminance of whatever brightness we’d set the screen to, and would not in any way try and alter the luminance at the graphics card level, which can reduce contrast ratio. These adjustments before profiling the screen would help preserve tonal values and limit banding issues. After this we let the software carry out the LUT adjustments and create an ICC profile.

The default gamma curve had been 7% out overall from a 2.2 average in the ‘standard’ mode, and so the setting changes and calibration had now helped us match that 2.2 within 0% deviance. The very cool out of the box white point (10,506k at 62% deviance) had been corrected nicely too, now being basically spot on to our 6500k and feeling much warmer and more comfortable for desktop use. Colour accuracy of the resulting profile was excellent with a dE average of 0.7 which LaCie would consider excellent. Gradients remained smooth and banding free. We should note that if the screen’s ABL feature kicks in it seems to impact the setup quite a bit. Luminance drops to about 80 cd/m² and it seems to impact the gamma of the screen as well.

The above calibration was completed with the gamut set to ‘auto’ which produced an sRGB emulation. We also calibrated the screen in the native wide gamut mode with the same OSD settings recommended as shown above and producing very similar results (with wide gamut covering 97.4% DCI-P3 and 132.1% sRGB though of course).

You can use our settings and try our calibrated ICC profiles which are available for sRGB emulation mode and wide gamut mode if you wish, which are available in our ICC profile database. Keep in mind that results will vary from one screen to another and from one computer / graphics card to another.

Hardware Calibration

The LG CX series supports hardware level calibration using the CalMAN Home software package. The screen features a built-in pattern generator for the software which means that you no longer need an external and expensive  pattern generator. This allows you even better control over the setup if you have a compatible calibration device and the CalMAN software package. Note that for many casual users, simple setting changes will be sufficient given the results we’ve seen above to get an accurate and comfortable setup. You can check our our comprehensive guide to using the CalMAN ‘LG AutoCal’ software here.

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Viewing Angles

Viewing angles of the screen were excellent which is a strength of OLED technology. There is very little colour tone or contrast shift from any viewing position which is great news. On darker content and a black image there is also no glow like you get from desktop monitors, like IPS tech where it has the widest available viewing angles in the monitor market, but which shows common pale/white glow from an angle. None of that here, and viewing angles are excellent.

Panel Uniformity

We wanted to test here how uniform the brightness was across the screen, as well as identify any leakage from the backlight in dark lighting conditions. Measurements of the luminance were taken at 36 points across the panel on a pure white background. The measurements for luminance were taken using BasICColor’s calibration software package, combined with an X-rite i1 Display Pro colorimeter with a central point on the screen calibrated to 120 cd/m². The below uniformity diagram shows the difference, as a percentage, between the measurement recorded at each point on the screen, as compared with the central reference point.

It is worth noting that panel uniformity can vary from one screen to another, and can depend on manufacturing lines, screen transport and other local factors. This is only a guide of the uniformity of the sample screen we have for review.

Uniformity of Luminance

Luminance uniformity of the screen was excellent on our sample, with 100% of the screen within a 10% deviance of the centrally calibrated area. The right side of the screen was slightly brighter than the left but not by anything meaningful or noticeable. Excellent performance here.

It should be noted that if you display a full black image to test for backlight bleed there is none – as there is no backlight on this screen and each pixel is individually lit. Sowing an all-black screen causes all pixels to turn off, and the screen shows true black as result, and looks like it’s just turned off.

General and Office Applications

This is a very different section to write when reviewing the CX OLED display. This is primarily a TV and so even the smallest model available is a an extremely large 48″ in size for a desktop monitor. Our personal opinion is that this is going to be too large for most people for comfortable and practical desktop / office use. It is more suitable for those who want to sit a further distance away for gaming, consoles, movies etc and isn’t very practical for up-close desktop work. We feel the same way about actual desktop screens we’ve reviewed in the past like 40″ and 43″ models, they are just pushing the limits of what is comfortable for a desktop monitor. You end up with a huge screen up close which although it has a decent resolution and text/fonts don’t appear too large, gives you such a large area to look at that it’s hard to make use of it properly. You end up craning your neck to look around the screen given it is so big.

If you have a deeper desk, and can manage to sit at a further distance (maybe 1m or more away from the screen) then it might be more useable as a size, but you need to have the space for it and then there’s issues around text size to consider. That’s another thing, you need to keep in mind you’re going to need a big desk and a big PC area for a screen this size, it’s not like using a typical 24 – 27″ sized desktop monitor.

The resolution is a sensible size for the screen at least and 3840 x 2160 Ultra HD makes it more viable than if it was a 1080p only. On the 48″ model (which is certainly the better choice relative to the others for desktop use) the pixel pitch is 0.2767mm which is exactly the same as a 24″ monitor at 1920 x 1080. That means that from up close from a normal PC monitor viewing distance the font size is comfortable and comparable to a common desktop monitor. That’s fine, but it means you need to be at a normal PC monitor viewing distance which then means the screen is far too large and in your face. If you move yourself back to a more comfortable distance so that the screen size is less of a problem, the text size becomes too small and so you then have to use Operating System scaling to make it bigger. This reduces your desktop real-estate and adds complications for some applications, games, and systems. Scaling isn’t always the easiest thing to use on PCs.

The larger CX OLED screens in 55″ and above start to become far less practical as a desktop monitor though. Their size becomes even more of a problem for viewing the screen up close, and the pixel density decreases too. We can imagine some people managing with the 48″ model, but the others are really too big for practical desktop monitor use.

Above: text clarity in PC input mode, click for larger version

Update 15/10/20 – After some reader comments we went back to revisit this section the day after the review was first published. Text clarity seems to vary slightly depending on what input mode you select. The panel uses an RGBW (Red/Green/Blue/White) pixel layout although this seems to have little impact in our re-testing. With the HDMI input set to PC mode in the home dashboard you get very clear text and it looks normal, like a desktop monitor would which is great news. You can see the clarity captured in the photo above at native resolution. This is with the screen set to full RGB range / 4:4:4 chroma. There does appear to be a small issue though in the PC input mode in that colour gradients then seem to show a bit of banding in darker tones. It wasn’t major, but we couldn’t eliminate it. Dropping down to lower chroma levels (4:2:2 and even 4:2:0) didn’t help the banding, and just made the text look progressively worse, especially at 4:2:0.

Above: text clarity away from PC mode, click for larger version

One way to improve the gradient performance and remove the banding is to switch the HDMI input mode to something other than PC, which then treats it like a normal media input. You get access to move settings in the OSD as well, but this does impact text clarity a bit unfortunately. We don’t believe that moving out of PC input mode changes the lag of the screen, as long as you still have things like ‘instant game response’ turned on. The gradients are better and the banding is gone, but the text clarity is a little worse. Despite the NVIDIA control panel being set to full RGB/full chroma, it looks like chroma 4:2:2 sampling has kicked in for some reason. A photo of the text clarity in this mode is shown above too. The text doesn’t look terrible, but you get a bit of blurring on coloured backgrounds as you can see above. The PC input mode is the optimal option for desktop monitor use and office work, despite the bit of banding that’s introduced.

Above: text clarity away with 4:2:0 chroma sub-sampling in place

For reference, and to include it in the same section, above is the text clarity if you have to drop to 4:2:0 chroma for any reason. This would apply if you wanted to run the screen at 4K and 120Hz, but from an older HDMI 2.0 generation card (discussed later). For office work you will definitely want to ensure you’re running at full RGB, even if that means dropping to 60Hz and then changing back to 120Hz when you game (or get an HDMI 2.1 card to avoid all that messing!)

[End of update from 15/10/20]

The glossy coating of the panel is a little more challenging as well for desktop use, and is one of those things that’s down to user preference. It helps to provide a clear looking image, but at the same time could cause complications for reflections. For office work you’re likely to have a better lit room than if you were gaming or watching movies, and so this can become a challenge because of the increased reflections from the coating. The wide viewing angles provided by the panel on both horizontal and vertical planes, helps minimize on-screen colour shift when viewed from different angles which is certainly a strength of OLED.

The out of the box setup in the default ‘Standard’ mode was not great for monitor use being much too cool and with a too high gamma. Thankfully a simple switch to the Expert (dark room) mode gives you access to far more settings in the menu, and also provides a far more reliable setup for these uses. There was of course an incredible contrast ratio with deep blacks for great shadow detail and contrast in photo and colour critical work thanks to the OLED panel. The default wide gamut offers an impressive DCI-P3 coverage although you may prefer to switch to the ‘auto’ mode which should then detect a PC input and emulate the more common sRGB colour space for SDR content. It was good to see a reliable sRGB emulation mode provided here, even though this is a TV and aimed at multimedia primarily.

The brightness range of the screen was decent enough for desktop use, with the ability to offer a luminance between 260 and 39 cd/m². This should afford you a decent enough range for darkened room conditions and low ambient light. A setting of around 36 in the OSD ‘OLED light’ control should return you a luminance close to 120 cd/m² out of the box. The brightness regulation is controlled via a flicker free backlight, without the need for Pulse Width Modulation (PWM), and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry. There was no audible noise from the screen, even when conducting specific tests which can sometimes cause issues.

One thing which can come in to play for office applications, and any time you have large areas of white or bright content is the Auto Brightness Limiter (ABL) feature. This can impact the overall brightness of the screen so could become annoying for colour critical or photo work. Generally for normal office work it’s unlikely to be a major issue and you probably won’t notice it. You’re also not going to be running the screen at high brightness levels for close up office work too.

Spectral distribution graph showing calibrated mode at 6500k

At our calibrated 6500k colour temperature you can see a the spectral output above. However the blue wavelength peak is shifted from the typical 448 – 450 nW/nm level and is instead nearer to 460 nW/nm which is supposed to be less harmful on the eyes.

Spectral distribution graph in the ‘Eye Comfort mode’

There is an option in the OSD for ‘Eye Comfort mode’ which is designed to change the screen’s colour temperature depending on your ambient light and usage conditions. When testing the screen at midday and in normal daylight settings we enabled this feature and saw a reduction in the blue light output as shown above. The white point did change to a slightly warmer  5375k as well. This might vary dynamically but might be a useful option to play with for reducing blue light and doing a lot of reading/office type work.

The screen does feature some USB ports but these are for connecting media devices to the display like other TV’s. Unlike on a desktop monitor they cannot be used as a hub for the PC as there is no USB upstream to connect back to your PC, and so you cannot see the USB sticks in Windows, or plug things like keyboards and mice in to them to operate your PC. There are no other extras like motion sensors or card readers on this screen which are sometimes useful for office-type uses. The stand offers no ergonomic adjustment so is very inflexible if you want to move the screen around. Wall mounting is a possible option instead if you want more flexibility.
 

Image retention risks and OLED issues

We will not go too much in to potential concerns around lifespan of the OLED panel, colour shift, dark spots or image retention/burn-in here. You can read our OLED Displays and the Monitor Market article for more information about those potential issues. As a desktop monitor if you are going to use the screen for many hours per day, some of these things might become an issue in time. In our fairly short period of time testing and using the screen we noticed no issues in any of these areas. The ABL feature was more of an annoyance and distraction to be honest, and although it’s there to try and help with life-span it might become an issue for some people for desktop type use, where it is more common to display white backgrounds and a lot of lighter content. If you are using the screen a lot as a desktop monitor and working with a lot of static content you will probably want to consider things like auto-hiding your taskbar, setting a screensaver to run etc. If you’re working with a lot of stationary windows for office work, internet browsing, photos etc then the risk of burn-in increases and to be honest that’s a bit of an annoyance with an OLED screen like this. These are things you don’t need to worry about with a typical desktop monitor but it’s always in the back of your mind when using an OLED screen. Leave the built-in prevention measures turned on to help, but you might want to read our article linked above to learn more about these risks and concerns.

Responsiveness and Gaming

The screen uses an OLED panel which is well-known for its near-instant response times. As a result it does not need to use overdrive technology in the same way as a desktop LCD panel would, or there at least aren’t any controls for the response time or overdrive in the OSD menu here. The part being used is a LG.Display LE550AQDEN-A1 (on the 55″ model we are testing) OLED technology panel which is self emitting and so does not need a backlight. Have a read about response time in our specs section if you need additional information about this measurement.

We use an ETC M526 oscilloscope for these measurements along with a custom photosensor device. Have a read of our response time measurement article for a full explanation of the testing methodology and reported data.

Graphics Card Requirements

The LG CX OLED like all other TV’s unfortunately does not offer a DisplayPort input which is by far the most widely used video interface output on PC graphics cards, including older generation options. If you wanted to use high refresh rates and VRR from a desktop monitor its much easier to use from most systems as DisplayPort is widely used on those displays as the connection of choice. 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.

To connect a PC to the LG CX OLED you are going to need a graphics card with an HDMI output, this will need to be v2.0 at a minimum which thankfully has become more widespread in recent years. If you want to use the LG CX OLED for gaming, and ideally make use of features like the 120Hz refresh rate, G-sync/FreeSync to their full extent that you’re going to invest in the latest generation of graphics cards with HDMI 2.1. Right now the only commercially available graphics cards with HDMI 2.1 are the recently released NVIDIA RTX 3080 and 3090 series.

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You can use HDMI 2.0 but with colour sacrifice and chroma sub-sampling required to support the bandwidth properly which isn’t ideal. Below shows the options available depending on your HDMI output.

So basically in summary if you have only an HDMI 2.0 output graphics card you can run the screen at 60Hz and native resolution without much issue, which is fine for desktop use and movies. You cannot use the full 10-bit colour depth panel / 12-bit processing, but 8-bit is supported and should be sufficient for most people anyway who might buy this kind of screen. It’s not really the kind of screen you’d buy for high-end graphics or photo work anyway. The issue is that if you want to use 120Hz for gaming, and you definitely should if you want vastly improved motion clarity, then you have to make some sacrifices to the colour output to get there from HDMI 2.0. Chroma sub-sampling is explained in more detail in our review of the Asus ROG Swift PG27UQ (where it is needed to reach the maximum 144Hz refresh rate at 4K) so we won’t go in to loads of detail here about what it is. In basic terms it will restrict the colour output to allow enough bandwidth to support the resolution and refresh rate, but this can lead to some loss of detail and clarity, especially evident when viewing text.

Above: text clarity at 60Hz (left) in PC input mode and 120Hz (right, with 4:2:0 chroma sub-sampling needed) from HDMI 2.0 output

Above shows some photos of the text quality at native 3840 x 2160 resolution running from an HDMI 2.0 graphics card output. On the left is the screen running at 60Hz (8-bit colour depth, full range RGB). On the right the text running at 120Hz (8-bit colour depth but with 4:2:0 chroma sub-sampling). There is some loss of quality and clarity to the text especially on red and blue coloured backgrounds as you can see here. In real use it’s not too bad from a reasonable distance away so for gaming and movies it’s probably not going to cause you too many issues – just like it didn’t really on the Asus ROG Swift PG27UQ. The benefit from the increased refresh rate more than outweighs some loss in colour and clarity for most people. You would however have to switch between 120Hz for games and 60Hz for desktop use really each time, as you ideally wouldn’t want to be using 4:2:0 chroma for normal day to day use.

The other issue is that many people don’t want to have to give up some of the colour quality in order to run at 120Hz and make full use of their nice new OLED display. They also want to be able to run at 4K, 120Hz and with 10-bit colour depth too for HDR content and gaming. That’s where HDMI 2.1 comes in, as it offers far more bandwidth room and allows the screen to run at its full potential. You will just have to fork out a lot of additional money to get a card that supports it right now.

Reported Issues at 120Hz with the Latest NVIDIA RTX 30 series Graphics Cards You may have seen some user reports that even from the latest NVIDIA RTX 3080 series cards there are a couple of problems with performance and running the screen at 120Hz. The first is a problem displaying 4K content at 120Hz and with full RGB chroma. This seems to be an issue limited to the newest CX series and sees the screen dropping to chroma 4:2:2 when it should be able to show full range chroma within the supported bandwidth of HDMI 2.1. Note that this is one step up though from 4:2:0 that you have to live with from HDMI 2.0, but is still not living up to the full advertised potential of the screen and HDMI 2.1 capability. This leads to some loss of colour quality, particularly evident on text rendering. The CX OLED has a maximum HDMI 2.1 bandwidth throughput of 40 Gbps, not the full 48 Gbps found on their 9-series screens, but even with that smaller capability this should be sufficient to handle 4k @ 120Hz @ 10-bit @ full RGB chroma. A second issue is that some are also reporting issues with G-sync including a complete loss of picture when attempting to use the feature at 120Hz, regardless of the colour settings or resolution. This impacted the 9-series screens from 2019 as well as the newer CX models from 2020. LG have now fixed this second issue on the 9-series, and so hopefully the CX update is not far behind. Here’s LG’s full statement on the situation courtesy of forbes.com: “LG has been made aware that some LG OLED TVs are experiencing certain compatibility issues with the recently launched Nvidia RTX 30 Series graphics card. An updated firmware has been in development with plans for a roll out within the next few weeks to LG’s 2020 and 2019 HDMI 2.1 capable TVs, which should address these incompatibility issues. When ready, additional information will be available on the LG website and in the software update section of owners’ LG TVs. We apologise for the inconvenience to our loyal customers and thank them for their support as we continue to push the boundaries of gaming technology and innovation.” More recently the Korean LG page has seen a firmware update for the CX series that seems to have fixed the issues, confirmed by users to be working in some other regions but apparently not available yet in Europe. This is a good sign that these issues will be fixed overall pretty soon we think. We will update this accordingly when we see more although the first link above to the reddit thread tracks all the updates and news nicely.

The other aspect to all this is whether your graphics card can power the screen at 4K and 120Hz. That’s a huge drain on system resources and so you are going to need a powerful graphics card to run it anyway, and achieve decent frame rates and settings for games. Another good reason why you’re likely going to need to invest at the same time in a top-end card like the new NVIDIA RTX 3000 series. The screen an thankfully support variable refresh rates (VRR) from both NVIDIA and AMD cards, giving you future flexibility with graphics card vendor, and helping to eliminate tearing and provide a smooth gaming experience when your frame rates do fluctuate.

One other option open to users, especially for gaming, would be to lower the resolution and push higher refresh rates and frame rates that way. It will make it easier on your system, and you can also avoid having to sacrifice chroma and colour quality. We found the screen natively supported 1080p and 1440p resolutions from within Windows without us needing to create custom resolutions from the control panel. At 1440p and 120Hz you could run at 8-bit colour depth but with full range RGB chroma (no sub-sampling needed) which was good. Lowering another step to 1080p allowed for up to 12-bit colour processing too. The screen does have a very good upscaling algorithm as well, so this content can look pretty decent even when not running at native resolution, so it’s certainly an option if you have an older graphics card and maybe even if you have HDMI 2.1 but just want to drive higher frame rates and settings. You would probably have to switch between these resolutions in Windows before gaming though which could become a pain.

Update 15/10/20 – we did some further testing of the screen creating custom resolutions like popular 3440 x 1440 resolution (21:9 aspect ratio) and 3840 x 1600 (21:10) formats. From an HDMI 2.0 card you are limited to 60Hz maximum from these resolutions at 8-bit colour depth and full RGB. The NVIDIA control panel feature for creating custom resolutions didn’t seem to like creating these at 120Hz and allowing chroma sub-sampling to get there, but you may have more luck with third party custom resolution tools. The resolutions works fine, giving you a black border at the top and bottom, and also at the sides on the 3440 x 1440 res since that’s a little less horizontally than the native panel resolution. If you want to game in 21:9 or 21:10 aspect ratio then this is viable in theory.

Response Times and Refresh Rate Considerations

There’s various things you need to consider when it comes to response times and gaming, particularly on a display with high refresh rate support. Gaming screens invariably give you a control for the overdrive impulse in the OSD menu which can help you tweak things, but response time performance and overshoot levels can vary depending on the active refresh rate. This behaviour is often different depending on whether the screen is a traditional G-sync screens (with hardware module) or whether it’s an adaptive-sync screen as well, and not all screens behave in the same way. We always try to test each variable in our reviews but the key considerations you need to make are:

1. Performance at 60Hz – this is important if you want to use an external games console (or other device like a Blu-ray player etc) which typically run at 60Hz. Response time performance may well be different than at the higher refresh rates supported, and you may need a different overdrive setting for optimal experience.
    
2. Performance during VRR (Variable Refresh Rate) – bearing in mind that the refresh rate will fluctuate anywhere from 1Hz up to the maximum supported by the screen (e.g. 1 – 144Hz on a 144Hz display). It’s important to understand if the response times and overshoot will vary as the refresh rate changes. There may be a need to switch between different overdrive settings in some cases, depending on your usually attained refresh rate output and graphics card capability. This can sometimes become fiddly if your refresh rates fluctuate a lot, especially between different games, so it’s always easier if you can leave a display on a single overdrive setting which is suited to the whole range. Some screens also feature “variable overdrive” which helps control the response times and overshoot depending on the active refresh rate. This is particularly apparent with traditional G-sync module screens.
    
3. Performance at fixed refresh rates including maximum – this is important for those who have a powerful enough system to consistently output a frame rate to meet the max refresh rate capability of the screen. They may want to run at max refresh rate without VRR active, or even is VRR is active they may know they will be consistently at the upper end of the range. Many gaming screens show their optimal response time performance at the maximum refresh rate. Knowing the performance at high fixed refresh rates may also be applicable if you want to use any added blur reduction backlight which typically operate at a fixed refresh rate.
    
4. Whether the response times can keep up with the frame rate – you will also want to consider whether the response times of the panel can consistently keep up with the frame rate. For instance a 144Hz screen sends a new frame to the display every 6.94ms, so the pixel response times need to ideally be consistently and reliably under this threshold. If they are too slow, it can lead to added blurring in practice and sometimes make the higher refresh rates unusable in real life. We consider this in our analysis.
    

Variable Refresh Rates (VRR)

The screen supports VESA Adaptive-sync and so can support variable refresh rates from compatible AMD FreeSync and NVIDIA G-sync systems. The VRR range supported is between 40 and 120Hz . The screen has been certified by NVIDIA under the ‘G-sync Compatible’ scheme as well as the FreeSync Premium Pro scheme which means the screen has verified VRR performance, support for an HDR input signal and Low Framerate Compensation (LFC). It also supports HDMI-VRR for next generation games consoles which is bound to be a useful feature.

The support for G-sync and FreeSync will be very useful given the significant system demands of running a screen at 3840 x 2160 (Ultra HD 4K) resolution and up to 120Hz refresh rate. It was of course very good to see it included here. You might also want to read our detailed article about Variable Refresh Rates here for more information about these technologies and what they offer.

To make use of G-sync you have to enable the ‘Instant Game Response’ option from within the OSD. G-sync should then be selectable in the NVIDIA control panel. If you want to use FreeSync from an AMD card you will also need to enable the specific ‘AMD FreeSync Premium’ setting in the OSD. We did not have chance to test FreeSync, only G-sync which seemed to work well.

Detailed Response Times

Recommended Settings

Optimal Refresh Rate	120Hz
Optimal Overdrive Setting (for above)	n/a
Optimal Overdrive Setting for 60Hz	n/a
Optimal Overdrive Setting for VRR	n/a

     Detailed Measurements at 120Hz

The response times were near-instant thanks to the OLED panel and were basically the same regardless of the refresh rate. The average G2G was measured at a very impressive 0.47ms G2G, with the maximum response time measured being only 0.72ms as well! There was some very minor overshoot with transitions from black to grey, but nothing that you could see in practice at all. Absolutely no issues with the response times here, and they could keep up 100% with the frame rate demands of the screen as well. You might think that super-fast response times is all you need for an amazing gaming experience, but there is a lot more to motion clarity and appearance than just fast pixel transitions!

Above: pursuit camera photos capturing real perceived motion clarity in practice

To achieve the optimal performance from this display we would recommend using it where possible at the maximum 120Hz. The motion clarity at the higher refresh rates is significantly better than at 60Hz as with all desktop monitors too. At 60Hz the screen doesn’t really look any clearer or smoother than a 60Hz LCD panel from a motion point of view (as long as response times are reasonable and there’s no major overshoot problems on the LCD). At 120Hz there are significant and marked improvements, as with the change in the desktop monitor market from 60Hz to 120Hz. The motion clarity pursuit camera photos above capture this nicely, with the 120Hz image looking clearer, sharper and smoother than 60Hz by a considerable way.

The support for 120Hz is very good for a TV, with many competitors being limited to 60Hz maximum only. So there is no doubt a massive improvement for gaming here, both from a PC and from future games consoles too. Powering the screen at 3840 x 2160 @ 120Hz is also likely to be a significant demand on your system and graphics card too, so getting beyond that is probably unrealistic right now anyway. In the monitor market the few available 4K screens with high refresh rate are also limited at the moment to 120Hz/144Hz maximum refresh rate, so it was great to see the same thing offered here from the CX OLED TV.

If PC gaming is your thing though, you can get a wide range of higher refresh rate PC monitors nowadays though that will offer you higher refresh rates and even better motion clarity. They won’t offer the size, OLED contrast ratios, HDR experience etc that this CX OLED screen can, but if we’re talking purely about motion clarity here then they are still a step beyond what this screen can offer. 240Hz does offer some reasonable improvements in motion clarity compared with 120Hz and certainly supports higher frame rates too, and there are plenty of gamer-oriented 240Hz models out there that are excellent performers for gaming. There are even some 360Hz models appearing now including the recently reviewed Asus ROG Swift 360Hz PG249QN. That offered some small additional benefits in motion clarity and frame rate room compared with the 240Hz models too, and its refresh rate is obviously much higher than the CX OLED can offer. From a pure motion clarity and gaming frame rate point of view, desktop monitors will still offer a significant advantage over even the best and most modern OLED TV’s.
 

OLED Panel Benefits for Gaming and Additional TV features

The OLED panel provides super-deep black depth and infinite contrast ratio which is of course excellent for gaming too. This helps ensure great shadow detail and true blacks. You may find optimal appearance in a darkened room though. There are no ‘Black Equalizer’ type options in the menu on this screen, something that gamers like to have on LCD monitors to adjust the gamma in darker areas and potentially help bring out details in darker scenes. The screen does offer a motion interpolation technology via the TruMotion menu which is designed to help motion look smoother and clearer by interpolating intermediate frames. This produces the “soap opera effect” where motion looks unrealistic and just odd, so it’s not to everyone’s liking. We don’t really like this technology at all and would recommend leaving it off. Although you may still wish to experiment with it via the TruMotion anti-blur settings. This setting is actually not available if you’re in PC input mode, so you would have to label your input as something else if you want access to this option. It will add additional input lag as well due to the frame interpolation and additional processing needed.

Refresh Rate Compliance

In this section we look at the response time behaviour across the range of supported refresh rates and consider whether they are sufficient to keep up with the frame rate demands of the screen. The grey line on the graph shows the refresh rate threshold, that being the average G2G response time that the panel needs to be able to achieve to keep up properly with the refresh rate and frame rate. For instance at a 60Hz refresh rate the response times need to be consistently and reliably under 16.67ms, while at 144Hz refresh rate the response times ideally need to be under 6.94ms to keep up with the frame rate demands. If they are not then this can lead to some additional smearing and blurring on moving content as the pixels can’t keep up. For these tests we will plot the average G2G figure at a range of measured refresh rates, while operating at the optimal overdrive control.

The table to the right then explains whether that overdrive control needs to be adjusted by the user depending on the refresh rate (not ideal), or whether variable overdrive is utilised to keep things simple. Ideally you’d want to be able to stick with a single mode for all refresh rates especially when you consider how these will vary during VRR. We also include a measurement of the % of the overall response time measurements that were within the refresh rate, as well as a slightly more lenient measurement of how many were within the refresh rate window within a 1ms leeway.

The super-low response times meant that 100% of the transitions were within the refresh rate window, including at the maximum 120Hz. In fact the screen could in theory reach up to 2000Hz and the response times would still be fast enough to keep up with the frame rate here! One day maybe…

Motion Blur Reduction (Black Frame Insertion – BFI)

The blur reduction backlight option is available via the ‘OLED Motion Pro’ setting which is available in the OSD in the TruMotion section. In PC input mode the OLED Motion Pro option is actually the only one available in this menu, but if you are in other modes than PC there are some other settings in that menu you may want to experiment with as well. You would only want to enable this mode for gaming or perhaps movies as it introduces a deliberate off/on flicker to the screen which is not what you want for day to day office-type uses. Unlike on an LCD monitor where the backlight is flashed off and on rapidly (referred to as “strobing”), the OLED pixels are turned to black instead since there is no backlight, hence the name ‘Black Frame Insertion’ (BFI) which LG refer to it as in their documentation and on their website. For gaming these blur reduction backlights can normally help improve the perceived motion clarity and make gaming even better.

This OLED Motion Pro mode is only available at fixed refresh rates of 60Hz or 120Hz. Like nearly all other blur reduction modes except a few Asus ‘ELMB-sync’ models in the desktop monitor market such as the Asus TUF Gaming VG279QM, this feature cannot be used at the same time as FreeSync/G-sync variable refresh rates, it’s one or the other.

120Hz BFI Mode

At 120Hz the BFI is in sync with the refresh rate of the display and the pixels are turned to black every 8.33ms. Because of the super fast pixel response times there is no delay to these changes either so you avoid unnecessary ghosting on the moving image. You still have access to the OLED light control (to adjust luminance) thankfully as well as most other OSD settings.

Example strobing at 120Hz in low, medium and high settings, horizontal scale = 5ms

The OLED Motion Pro feature has settings for off, low, medium, high and auto. We measured the off/on pattern as shown above in each mode. As you increase the setting the “on” period is shortened which can help improve the motion clarity further, but does also impact the brightness of the screen. We measured the following maximum brightness levels in each mode (with OLED light setting at 100) – low setting 216 cd/m², medium 148 cd/m² and high 119 cd/m². If the ABL feature kicks in then that will impact the brightness of the screen as well by another 50 cd/m² or so. Even the high setting is likely to be sufficient for PC gaming and for many users we expect as it is still reasonably bright, and does provide the optimal motion clarity for this feature. The medium mode is a good middle ground too with only slightly reduced motion clarity. It’s basically just a brighter version of the high mode in practice.

Above: pursuit camera photos at 120Hz in normal mode (BFI off), then with BFI set to high

The improvement in motion clarity is very good as you can see from the pursuit camera photos included above. The image becomes sharper and clearer which is great. The image also looks the same across the whole screen, you don’t have to worry about some areas having nasty ghosting or worse image quality. At 120Hz this is actually a very good implementation of a blur reduction mode feature and could work very well. You would have to sacrifice using G-sync/FreeSync but the motion improvement benefits are definitely there.
 

60Hz BFI Mode

Above: pursuit camera photos at 60Hz in normal mode (BFI off), then with BFI set to medium and then high modes

At 60Hz the BFI behaves a bit differently. In the low and medium modes it is unfortunately not in sync with the refresh rate and you get two “strobes” per refresh rate cycle. It inserts a black frame every 8.33ms which has the negative impact of causing a doubled ghost image to moving content and doesn’t look very good. You can see this clearly from the pursuit camera photos above. If you switch up to the high mode then the “strobing” is brought in sync with the refresh rate at 60Hz and you get a much clearer picture with great motion clarity again. It makes a huge difference relative to normal mode (BFI turned off) at 60Hz making the moving image much sharper, clearer and easier to track. The issue though here is that the BFI is then every 16.67ms which introduces a noticeable flicker to the screen (at 60Hz frequency). For motion and gaming this is harder to spot, but could still cause you issues with eye strain and discomfort. It’s certainly very noticeable for static images when you first turn it on. Some people may like it still and at least at 60Hz it’s a usable option that really helps with motion clarity. We would not recommend using the low or medium modes at 60Hz though.

Blur Reduction Tests Summary

The following pursuit camera photos give you an indication of observed motion clarity as the human eye would see it in each of the modes we’ve discussed.

Pursuit camera photos capturing perceived motion clarity in each mode

There is a significant improvement in motion clarity when going from 60Hz to 120Hz with BFI off as with all desktop monitors as well. If you have the graphics card power to run the screen at 120Hz it will certainly be preferable for gaming. You may want to consider lowering the game resolution to accommodate higher frame rates here we think if you don’t have the system power to run 4K @ 120Hz reliably. Turning BFI on brings about some decent improvements in motion clarity as well which is great. At 60Hz the only mode usable really is ‘high’ where the strobing is in sync with the refresh rate at 60Hz. This massively improves the motion clarity relative to normal 60Hz mode, but does introduce a very noticeable flickering. At 120Hz all the low/medium/high modes are usable and improve the image very nicely, just with differing max brightness levels. Go for the highest level you can while still having the screen at the right brightness for your preference.

Additional Gaming Features

• Aspect Ratio Control – the screen offers a range of aspect ratio controls from the menu including 16:9, original, 4:3, vertical zoom and 4-way zoom. The ‘original’ mode will probably be most useful for handling any weird aspect ratios, although the native 16:9 is very common across different devices.

• Preset Modes – There is a preset mode for “game” available which is optimised for gaming. This has quite a few settings locked and unavailable though but this should offer the smallest amount of lag and image processing for gaming. You can still tweak settings in this mode to correct things like the overly cool default setup.
   
• Additional features– there are no other gaming features like cross-hairs, FPS counters or timers on this screen

Lag

Read our detailed article about input lag and the various measurement techniques which are used to evaluate this aspect of a display. The screens tested are split into two measurements which are based on our overall display lag tests and half the average G2G response time, as measured by our oscilloscope. The response time element, part of the lag you can see, is split from the overall display lag and shown on the graph as the green bar. From there, the signal processing (red bar) can be provided as a good estimation of the lag you would feel from the display. We also classify each display as follows:

Lag Classification

• Class 1) Less than 8.33ms – the equivalent to 1 frame lag of a display at 120Hz refresh rate – should be fine for gamers, even at high levels
• Class 2) A lag of 8.33 – 16.66ms – the equivalent of one to two frames at a 120Hz refresh rate – moderate lag but should be fine for many gamers. Caution advised for serious gaming
• Class 3) A lag of more than 16.66ms – the equivalent of more than 2 frames at a refresh rate of 120Hz – Some noticeable lag in daily usage, not suitable for high end gaming

For the lowest lag performance you will need to turn on ‘instant game response’ from within the OSD menu. Without this on and outside of the game preset mode the lag is super-high like with many TV’s and you will definitely want to avoid that for gaming. The more processing features you turn on in the menu as well, the more lag you will potentially add outside of this game mode.

The total lag measured at native 4K resolution was decent for a TV at 11.2ms. The pixel response times should account for very little of that, around 0.24ms, and so we can say that there appears to be around 10.96ms of signal processing lag on this screen which is low for a TV. This is higher than many desktop monitors though where they are commonly 1 – 2ms, especially those with hardware G-sync modules. The lag here is unlikely to cause any major issues though for gaming and is certainly better than many TV’s which can commonly be somewhere in the region of 40 – 90ms, sometimes even higher. If you lower the resolution to 1440p or 1080p then the lag improves a little, down to 7.06ms signal processing which is good.

Movies and Video

The following summarises the screens performance for videos and movie viewing:

Category	Display Specs / Measurements	Comments
Size	48 – 77″ ultrawide dependent on model	Much larger than any desktop monitor as this is a TV primarily
Aspect Ratio	16:9	Great support for common inputs and devices natively
Resolution	3840 x 2160	Can support native 1080p content and Ultra HD 4K natively
HDCP	Yes v2.2	Suitable for encrypted content
Connectivity	4x HDMI 2.1 1x composite	Good range of HDMI connectivity for consoles, Blu-ray players etc. While they are all v2.1 they are all backwards compatible with earlier versions
Cables	None	Not provided with an HDMI cable in the box
Ergonomics	None	No adjustments from the stand so might be tricky to position for a variety of viewing positions. Wall mounting is an option popular with many owners
Coating	Glossy	Provides clear, non-grainy image and but may lead to some unwanted reflections in some situations depending on your ambient lighting
Brightness range	33 – 222 cd/m2 (SDR) 772 cd/m2 peak (HDR)	Reasonable adjustment range offered in PC mode although not super bright. When in HDR mode the peak brightness is decent, more on that in the next section. Flicker free backlight operation with no PWM
Contrast	Infinite:1	Amazing contrast thanks to the self-emitting OLED panel where pixels are turned fully off for full black. Produces incredible contrast ratio and shadow detail
Preset modes	Cinema (plus others)	There is a cinema mode available which has a pretty decent setup and allows access to more settings than the default profile. May be useful to use if you want something else set up for movies away from your desktop profile. When an HDR input signal is detected the display will also switch in to the HDR mode which can be customised separately as well. We would recommend the cinema mode for the HDR input as well for a decent setup if you’re watching a lot of movies
Response times	0.47ms G2G with very low overshoot at all refresh rates	Response times are excellent and near-instantaneous thanks to the OLED panel. Don’t expect wonders for motion clarity at 60Hz though still. Refresh rate plays an important role here. You do get some additional judder on 24p content for panning shots in movies as a result of the response times being so fast. You may want to experiment with the TruMotion anti-judder settings here if it’s a problem
Viewing angles	Excellent	Super-wide viewing angles thanks to the OLED panel and no glow like you would get on an IPS panel on dark content
Backlight bleed	None	No bleed as when an all black image is shown, the pixels are turned off thanks to the OLED panel
Audio	Headphone output and very good Dolby Atmos speakers	Being a TV this screen provides very good integrated speakers well beyond anything you’d get from a normal desktop monitor. A headphone jack is also provided
Aspect Ratio Controls	16:9, original, 4:3, vertical zoom and 4-way zoom settings	Good options to account for non-16:9 format inputs via the “original” and “4:3” modes if needed. Many inputs will be the native 16:9 though
PiP / PbP	Neither supported	n/a
Additional features	Remote control In-built apps Smart TV features	Being a TV there are also a range of extra features that will be very handy for movie viewing. The packaged Smart Remote is versatile and efficient. There are many in-built applications like Netflix, Amazon Prime, Apple TV, Disney+ etc as well for easy access and use.

High Dynamic Range (HDR)

The screen is perfectly positioned to handle HDR content and surpasses anything available currently in the desktop monitor space. OLED technology has long been regarded as the best technology for HDR thanks to its pixel-level dimming capability. This allows each pixel to be individually lit, meaning you don’t need backlight local dimming zones or need to worry about issues like “blooming” or halos like you get on other technologies. Technically the contrast ratio you get for normal SDR content is infinite:1 as well (for maximum “dynamic range”), but in HDR mode these OLED screens are capable of offering increased peak brightness as well. Let’s compare it to the desktop monitor market though first.

Marketing image provided by LG to illustrate local dimming capabilities

Most desktop monitors, even those advertised with the very lapse and pointless VESA DisplayHDR 400 certification lack any form of local dimming for HDR. So by their nature cannot actually improve the dynamic range of the display! Sure, they can accept an HDR input source (usually just HDR10) and some may offer slightly brighter screens, maybe 10-bit colour depth, maybe a wider colour gamut but they don’t always and the HDR 400 spec doesn’t require any of that either! But without local dimming there’s no improvement to the dynamic range at all and you are basically limited by the LCD panel’s native contrast ratio. For a TN Film or IPS panel this would max out at around 1000 – 1300:1 and for a VA panel maybe around 3000 – 5000:1. Local dimming is a vital component of HDR.

Some screens might carry the higher HDR 500 or HDR 600 certifications though which do at least require some form of local dimming, making it at least viable for the dynamic range to be improved. Those specs also require a higher peak brightness of 500 or 600 cd/m², 10-bit colour depth and wide DCI-P3 gamut so you can at least expect a better HDR potential from HDR 500/600 screens. However, all of these screens feature only fairly simple edge-lit local dimming of the backlight in a very limited number of zones. This is normally something like 8 zones, maybe 16 or 32 if you’re lucky. In theory this can allow for improved dynamic range across the screen as a whole, with the backlight being capable of dimming darker areas while brightening others. In practice you don’t get much of an improvement in “local HDR contrast” between adjacent areas of light and dark, and it’s not capable of picking out smaller highlights or sample areas very well.

For the top-end HDR experience in the monitor market today you’d be looking currently at some of the niche and very expensive top-end models with a Full array Local Dimming (FALD) backlight. We’ve reviewed models like the Asus ROG Swift PG27UQ and PG35VQ in the past with 384-zone and 512-zone local dimming backlights for instance. These meet the upper tier HDR 1000 standard so can reach even higher peak brightness of 1000 cd/m², along with wide gamut colour space and 10-bit colour depth. These FALD options, and some newer “mini LED” options like the forthcoming Asus ROG Swift PG32UQX for instance (HDR 1400 with 1152 zones) with even more (and smaller) dimming zones represent the best available HDR options on desktop monitors today. The problem is these models are very expensive and top-end, and even with many hundred zones, it can still leave you with some issues for HDR content. Blooming and halos are still a problem when smaller highlights are needing to be brightened, and while the more zones the better, it will never be as optimal as per-pixel dimming like on OLED.

So the dimming capabilities of the OLED panel here easily surpass all desktop monitors when it comes to HDR, and the true black and infinite contrast make it ideal for improving the dynamic range. This particular LG CX OLED also has the necessary wide gamut and 10-bit colour depth support (with 12-bit processing) so it offers the boosted colours and appearance associated with HDR content too. Being a TV it is also more equipped than most LCD monitors, even those at the top end, at handling different HDR standards, being able to support HDR 10, Dolby Vision and HLG here.

We also measured the peak brightness of the screen with a range of white sample sizes which are recorded above. This was done in the ‘game’ preset mode, PC input option for the HDMI port and with the ‘peak brightness’ control set at ‘high’ in the OSD menu and the OLED Light setting also at the default 100 when HDR mode is activated.

The maximum peak brightness we measured was 772 cd/m² which was decent and a considerable way beyond the SDR maximum brightness. You get nice bright highlights and details in HDR content, combined with the true blacks when needed to create an impressive dynamic range and overall HDR experience. As the brighter areas become larger you do lose a lot of the peak brightness as the ABL feature kicks in and controls the maximum brightness of the screen fairly aggressively. As a side note you can get slightly higher peak brightness in other preset modes like ‘Cinema’ and for non-PC input settings.

• Further reading: our High Dynamic Range (HDR) article

Conclusion

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This was a very different screen for us to test given it is primarily a TV, and being a completely different technology to all desktop monitors. We hope we’ve captured all the relevant information and provided some good analysis in to how it could be used as a monitor throughout this review (let us know if you think we’ve missed anything!) There is no doubt that the OLED panel offers some incredible benefits compared with LCD screens, but also at the moment it can’t be considered a perfect desktop monitor we don’t think. The infinite contrast ratio, true blacks and per pixel dimming make it exceptional for HDR content and for high contrast images. This provides a brilliant image quality and makes movies and games a pleasure. This is clearly one of the key strengths of this CX OLED display. HDR looks amazing and there is per-pixel dimming, no blooming, a decent peak brightness capability, wide range of preset modes, good HDR format support and the requisite colour capabilities like DCI-P3 wide gamut too.

For gaming the near instant response times are excellent of course and very welcome, but don’t be fooled in to thinking that’s all you need for a great experience. Thankfully the screen supports a high 120Hz refresh rate which offers obvious and significant improvements in motion clarity for gaming and is a very welcome feature. The presence of G-sync and FreeSync support help make this is a viable option as a desktop monitor, supporting variable refresh rates nicely which will be vital given the huge system demands of running at 4K and 120Hz. Great to see these becoming more common in the TV space. Speaking of system demands you are really going to want to pair this screen with a latest generation NVIDIA RTX 30 series card to be able to take advantage of its full potential, and allow you to reach those upper refresh rates that are going to be vital for an optimal gaming experience. That’s going to add significantly to your spending keep in mind. Lag is low for a TV although not as super-low as many desktop monitors. The BFI mode works really well and provides very good blur reduction benefits too across the screen, even being usable at 60Hz.

As a desktop monitor the size is not going to be to everyone’s liking, and personally we felt it was still too large even as a 48″ option for most people. You need a lot of space to accommodate it, and sitting up close for a normal PC viewing distance is a bit too in-your-face. Text clarity was not perfect due to the pixel layout and the scaling of resolution becomes a challenge if you want to sit at a more sensible distant viewing position. The stand is limited and the glossy coating can be a bit of a pain depending on your room lighting. You also have the ever-present worry of image retention on OLED that sits in the back of your mind during use like this. Thankfully if you do want to do some more normal desktop monitor work it’s possible to get a reliable and accurate setup with a few simple OSD changes. The default profile is not very accurate but there’s loads of settings and modes to use. There’s support for wide DCI-P3 gamut as a decent sRGB emulation mode, also for 10-bit colour depth too from the panel. There’s even support for hardware calibration if you have a suitable device and the CalMAN software package.

As a screen for movie viewing, HDR content, console gaming and even PC gaming from a reasonable distance it is an excellent choice if you have the space and want a large format screen. The benefits of OLED really come in to play here. For day to day desktop, office and professional-type uses it is more difficult to use and probably not an ideal choice. It’s certainly a very interesting option to explore, and hopefully one day we will see affordable, decent sized desktop monitors based on OLED too.
 

Pros	Cons
Amazing contrast ratio, black depth and image quality from OLED panel	Too big really for many people as a desktop monitor
HDR is exceptional with per-pixel dimming, no blooming and decent peak brightness	Some challenges with the technology related to life-span and image retention could become more of an issue for monitor use
Fast response times, 120Hz, great BFI mod and G-sync/FreeSync support for gaming	You will probably need to spend more on a latest gen graphics card to really get the most out of the screen

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