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  There’s been a lot of talk about OLED computermonitors – the idea of better picture quality due to perfect blacks, and an instantaneousresponse time definitely sounds appealing. On top of that, OLEDs don’t have a backlightso don’t have any risk of the dreaded backlight bleed that plagues even the most expensiveLCD monitors. Do they really live up to the hype though,and what are the main drawbacks of using an OLED as a monitor? So, this year is the first time that an OLEDTV has been available in the smaller 48” size – typically they are only 55” andlarger. We bought the 48” LG CX OLED to put to the test on our Monitor test bench and see how it performs.  WE HELP PEOPLE FIND THE BEST PRODUCTS FOR THEIR NEEDS ! 


First we’ll look at the design of the LG CXand then move on to the picture quality. We’ll look at the motion handling, input lag,and overall gaming performance. If you’d like to skip straight to our testresults, then see the links in the description below. We bought the smaller 48” CX to test, butit is also available in larger sizes up to 77 inches. Of course, forty eight inches is already onthe large side for a monitor so most people probably aren’t interested in these largermodels to put on their desk. Now, what this 48” size and 4k resolutionmeans for you is a pixel density of about 92 pixels per inch. This sounds a bit low when you consider manypeople find the sweet spot to be about a 27 inch 1440p monitor that has 109 pixels perinch. Something to note though is that most peoplewill sit farther back from the larger 48” screen – you really don’t want to be movingyour head too much. As a result, in real usage the visible pixeldensity is very good, but we’ll talk about this more when we look at the text claritylater on in the review. Now, as far as the design goes there’s afew important considerations if you’re looking to use a TV as a monitor. Firstly, as typical for a screen of this sizethe ergonomic adjustments are limited! It’s not like a typical monitor that you caneasily rotate side to side or up and down. If you care about this, then a third partymount is probably the way to go. Something else to note is the inputs. For PC use, a displayport connection is generallypreferred.

 As typical of a TV, the CX doesn’t havea displayport connection so instead you need to connect via HDMI. This is fine – as we’ll talk about later becausethe ports are advertised to be HDMI 2.1 – capable of supporting very high bandwidth signals. A third significant difference is that asa TV it has some other features like a smart platform and a TV tuner. And lastly, while most monitors will justshut the screen off when your PC turns off or goes to sleep, this isn’t the case witha TV. As a result, you should keep the remote handy. Now despite the differences from most monitors,the style of the CX looks good. The low profile stand supports it well andis very stable. It does stick back a lot though, so if youuse the stand you can’t push it back against a wall to reclaim your desk space. You can also mount it on a wall or desk stand,but of course it is much larger than most monitors with a 300 by 200 VESA mount. If you do so though, then the total thicknessis about two inches. The borders are also thin and look good. So that’s it for the design, now we’ll moveon to the picture quality. If you want to see any of these tests in moredetail, see the review page on our website which is linked below. 

As we’re talking about an OLED, the firstthing to note is the contrast. OLED displays are classified as an emissivetechnology. Now, this is a simplification but traditionalLCD displays take a white backlight and filter away colors to produce the desired image. This filter isn’t 100% effective, so blacksaren’t completely pure. On the other hand, emissive technologies cancontrol the light emitted from each sub-pixel, and shut off dark areas completely. Basically, this results in much deeper blackswhich is noticeable in a dark room and one of the most significant aspects of picturequality. Another effect of this is that there’s nobacklight bleed or IPS glow. Overall if you care about the image in a darkroom, this will be an improvement. Now, while blacks are perfect – OLEDs havetypically had problems with near-black areas, like very dark grays. This tends to be visible as vertical or horizontalbanding. Now, this is somewhat hard to evaluate aswe’ve found it varies both between units and also over time. You might buy an OLED and notice verticalbanding, only for it to change over time to bother you less… or unfortunately more. As a result, while the model we bought seemsto handle dark scenes very well with very minor issues, we don’t know if this is areal improvement over previous models. Let us know if you buy this and how yours compares! Now for PC use, viewing angles tend to be very important. This is because the resolution of monitorstends to be high to maximize on-screen real estate, and so people sit relatively closeto read text and see details.

 When viewed from up-close, the sides of thescreen are at a large angle – both horizontally and vertically. As a result, for LCD displays IPS models withwide viewing angles tend to be favored over TN models that look bad from an angle. What does this mean for an OLED like thisone? Well the good news is that the image looksvery accurate at an angle. It does behave differently to an IPS monitorthough – while the brightness and gamma are consistent, colors do shift a bit. So now for the brightness. A bright monitor is important if you’re ina brighter room – to overcome glare. Something to note for this is that OLEDs tendto vary their screen brightness depending on the brightness of the image – this is calledthe ABL or Automatic Brightness Limiter. By that I mean, if you have a dark backgroundand open a small white window, the window will remain bright, but if you expand thatwindow full-screen you might notice the brightness dropping. In some cases ABL can be a good thing – itcan allow prioritizing power to boost highlights in many scenes. For use as a monitor though it is almost universallya bad thing. The good news is LG is well aware of thisissue, and introduced a setting called ‘Peak Brightness’ so you can adjust the amount ofABL you want to see. In PC mode this setting is locked to the lowestvalue. The brightness is about two hundred and fiftynits which should be fine for most people, and these brightness changes probably aren’tnoticeable in most cases which is good. 

Having said that, if you want to enable thepeak brightness setting, for example to produce bright HDR highlights, then you can eek outa much more impactful image. In this case for HDR, we measured a peak ofabout seven hundred and thirty nits which is great. The problem is that it can’t be sustainedover a large screen area so you might notice the overall screen brightness drop in certainsituations. So now we’ll talk about the reflection handling. Unlike most monitors, the CX is glossy. This might sound like a bad thing, but itreally depends on your use and preferences. Remember that glossiness is independent ofreflectivity – that is, you can have a matte screen that reflects a lot or a little, andthe same applies for a glossy one. In the case of the CX, the antireflectivecoating is very effective, and it cuts out much of the light incident on the screen. This is great for a room with some lights,although any resulting reflections do remain defined. If you’re planning to use this as a monitor,then clarity of text is very important. A quick note – you should be on PC modefor the clearest text, which allows the screen to correctly display a 4:4:4 or RGB signal,without any chroma subsampling. Now in terms of text clarity there’s a fewthings going for this monitor and a few against it. Let’s start with the positive. The glossy finish means that each pixel andsub-pixel is clearly defined. There’s none of the hazyness you might seeon matte finishes, which is great. The TV also has a very high resolution, soif you want to apply scaling to increase the text size, then the high pixel density canresult in clearer text. And now for the flip-side. This TV and other OLEDs have an atypical pixelarrangement. Instead of the usual red, green, blue sub-pixelstructure, there’s an additional fourth white sub-pixel. Only a maximum of three sub-pixels are everin use at one time for each pixel. This means that on any pure color, if youlook close there’s always dark regions. On top of that, only about 50% of the verticalspace is filled with pixels. If you’re far enough back, this all blendsinto a single color and isn’t a problem.

 From close up though when looking at text,you can see in our image that the text becomes a bit harder to read. On top of that, many operating systems applyfancy algorithms to display text on the higher-resolution sub-pixel layer – this is known as sub-pixelrendering. This tends to assume a standard sub-pixellayout, so the OLED alternative layout actually looks worse. Even tuning windows cleartype, the resultsweren’t as good as with the setting disabled. Overall though, while the text clarity isfine, it definitely isn’t on the same level as a nice LCD display. And now a note on the color gamut. A wide color gamut is important if you wantto display vivid colors – such as when playing HDR games. The CX has a very good wide color gamut, andis capable of displaying almost all of the DCI P3 color space making it a good choicefor HDR. Now, a discussion of OLED picture qualitywouldn’t be complete without a mention of burn-in. In the case of an OLED or organic LED, thisis where the image degrades over time as a result of the limited lifetime of the organiccompound. We’ve tested this on our TVs to simulatenormal TV use and don’t expect it to be a problem for most people. Monitor use is different though, and theretends to be more static regions like taskbars and icons. As a result, we really don’t know how muchof a risk this is. If this is something you’re concerned about,you should note that most warranties won’t cover it, so you might need to look for onethat specifically does, or avoid an OLED entirely.

 So now on to the motion, and this is wherethings get really interesting! We’ll start by talking about the refreshrate. So first up, this has a maximum refresh rateof 120Hz. This comes with some caveats though – thefirst is that for high bandwidth signals, this requires HDMI 2.1. There’s no HDMI 2.1 graphics cards availableyet, but they are rumoured to come out later this year. As a result, we haven’t been able to testthe capabilities of this display that require more than HDMI 2.0 bandwidth. Now, this is about to get a bit technical. For most people it doesn’t really matterthough, so feel free to skip ahead! What this means, is that we’re able to test4k at 60Hz with a full chroma signal for clear text. 4k @ 120Hz with a 10 bit RGB signal shouldbe supported when a compatible graphics card is released, but we haven’t tested it. The maximum bandwidth of this TV is expectedto be 40 Gbps, less than the full 48 Gbps available in the HDMI 2.1 specification. For most people this probably doesn’t mattermuch, but it does mean 4k @ 120Hz with a 12 bit RGB signal is expected to be outside ofthe HDMI capabilities of this TV. Now onto the response time. You can learn more about response time inour motion video series, which is linked below. A fast response time is crucial for gaming,as it is the time it takes for a display to change pixels from one color to the next. A slow response time can result in a blurrytrail behind fast moving objects. So it’s quite important for gaming monitorsto a have a fast response time, in order to reduce motion blur. OLED displays like the CX have an almost instantaneousresponse time – with a small catch. Dark transitions can result in some overshoot. This is visible as slightly brighter smearingbehind dark moving objects. It is still an excellent result though, andfaster than any other monitor we’ve tested. It results in fairly clear motion withoutghosting. Note though that in this image there is novisible flicker, so there’s still persistence blur. Now if you want the clearest motion, thenit helps to flicker the image to clear up this type of persistence blur. One the CX, this can be done with the ‘OLEDMotion’ setting. This can be applied for sixty hertz or onehundred and twenty hertz signals, and definitely works well as you can see in our moving logophoto. It’s not for everyone though, as it doesadd visible flicker. Now let’s look at the input lag. A low input lag is important to feel responsive. Especially when playing fast paced games. 


The lower the input lag, the lower the delaybetween an action in-game and when you see it on the screen. At about ten milliseconds, it definitely feelsresponsive and shouldn’t be a problem for most people. It is a bit higher than some other gamingmonitors, but is unlikely to be noticeable unless you’re a really competitive gamer. And lastly, for the variable refresh ratesupport. This TV supports FreeSync variable refreshrates, with a range from 40Hz up to 120Hz. This is a fairly wide range and should begood for most people. The TV is also certified to be compatiblewith NVidia G-Sync Graphics cards, and we were able to verify this on our RTX 2070. Overall, it’s a great result and means youcan expect an almost tear-free gaming experience. So overall, the LG CX is definitely an interestingTV to use as a monitor! The use of an OLED panel results in a fewdistinct advantages over most traditional LCD displays. Most notable are the excellent picture qualityincluding wide viewing angles, and instantaneous response time. On top of that, this display has a relativelyhigh refresh rate of 120Hz, and supports FreeSync with G-Sync compatibility. There are definitely some drawbacks though. The text clarity is a bit worse when viewedfrom close-up, and we don’t know how much of a risk burn-in might be. So that’s it! What do you think of the LG CX? Are you going to buy it? Let us know what you think below. 

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