

Introduction Has there ever been a bigger build up to any monitor release? Since the first prototype was shown off at Computex in June 2016 (yes, over 2 years ago) there has been a massive amount of hype, anticipation and excitement about the Asus ROG Swift PG27UQ display. There's been a bit of a dilemma for buyers in recent years. Do they prioritise UltraHD (aka "4K") resolution for the sharpest possible image and highest level of detail, or prioritise high refresh rates for the smoothest and fastest gaming experience. Until now, it's been one or the other but the reason for the excitement with the PG27UQ is because it will finally offer buyers the chance to have both. When the prototype was displayed all that time ago, it was the first screen to be announced with an Ultra HD 3840 x 2160 resolution and support for a high 144Hz refresh rate. Over the last 2 years more and more information has emerged about this screen which has only added to the excitement, and we now finally have one with us for testing! To summarise the key features of the PG27UQ is tricky, as it really offers a huge range of specs and options that to many people make up a dream monitor. The 27” sized Ultra HD resolution panel is IPS-type in technology, using an AU Optronics AHVA panel for great all round performance and all the benefits of IPS technology that are well established in the market. This is a gaming screen, but it's not limited in other areas like many TN Film gaming screens are. It offers support for refresh rates up to 144Hz for super-smooth game play, high frame rate support and improved motion clarity. To achieve this, it makes use of the latest DisplayPort 1.4 interface. We are going to refer to the resolution of this screen during this review as 4K in places. We know it's technically called 'Ultra HD' but the term 4K is so widely used and frankly, easier to keep referring to. Not only does it offer “4K” at 144Hz, it also features the latest NVIDIA G-sync HDR chip which supports the variable refresh rate we know and love, and that will be extremely important given the system demands of this resolution and refresh rate combination. This new chip also offers top-end LCD High Dynamic Range (HDR) capabilities thanks to a 384-zone Full Array Local Dimming (FALD) backlight system. This can offer superior HDR experience compared with more limited edge-lit local dimming, and allows for high-end specs like a 1000 cd/m2 peak brightness. A wide colour space for HDR is supported through an added Quantum Dot film coating, offering coverage for the DCI-P3 colour space along with 10-bit colour depth. Thanks to all these high end HDR features, the PG27UQ carries the VESA DisplayHDR 1000 and Ultra HD Premium certifications for HDR performance. Why the wait? 2 years is a long time to go from prototype to release, but this has been a very complicated and expensive screen to produce. There have been delays while DisplayPort 1.4 was finalised and became available from a graphics card point of view. That's only been a recent development and only the very top end modern cards have DP 1.4 available. That was needed to provide bandwidth to support the resolution and refresh rate, and is well beyond the capability of the older DP 1.2 interface. Then there was the FALD backlight which reportedly created all kinds of complications, especially when trying to operate it with variable refresh rate technology from G-sync. Early FALD backlights like that we saw and tested on the Dell UP2718Q were very slow as well, and not suited to fast changing content like gaming. That Dell screen was aimed at professional content creators and HDR multimedia, but isn't really suitable for gaming in HDR due to that slow FALD operation. A lot of work has gone in to making the FALD faster and better for these gaming screens. Getting the whole thing working correctly will no doubt have been a challenge, with BlurBusters.com reporting that they estimated 100x the amount of usual firmware-engineering hours went in to this screen. The PG27UQ has appeared in some regions to purchase now. A few websites globally have looked at the screen already, but our UK sample took a little longer to find its way to us. A recent firmware update from Asus also delayed it a couple of weeks in July but it's here now, and hopefully worth the wait! The screen retails for a very high price and so its target market is somewhat niche. We will put the PG27UQ through all our normal tests to see how it performs to help you consider whether it’s something you want to invest all that money in. 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Specifications and Features The following table gives detailed information about the specs of the screen as advertised: Monitor Specifications Size 27" (68.4cm) Panel Coating Light AG coating Aspect Ratio 16:9 format, flat Interfaces 1x DisplayPort 1.4

1x HDMI 2.0 Resolution 3840 x 2160 Pixel Pitch 0.155mm (163 PPI) Design colour Black bezel. 'Plasma copper' and 'Armor Titanium' stand Response Time 4ms G2G Ergonomics Tilt, 120mm height, swivel, rotate Static Contrast Ratio 1000:1 SDR

50,000:1 HDR mode Dynamic Contrast Ratio n/a VESA Compatible Yes 100mm Brightness 600 cd/m2 (typical)

1000 cd/m2 (peak HDR) Accessories DisplayPort, HDMI and USB cables. Power cable and brick Viewing Angles 178 / 178 Panel Technology AU Optronics AHVA (IPS-type) Weight with stand: 9.2 Kg Backlight Technology Direct LED with Quantum Dot Enhancement Film (QDEF)

384-zone Full Array Local Dimming (FALD) Physical Dimensions (WxHxD) with stand

634 x 437 - 557 x 268 mm Colour Depth 1.07b (8-bit+FRC) Refresh Rate 120Hz native maximum

144Hz overclocked

(60Hz over HDMI) Special Features 3.5mm Headphone jack, NVIDIA G-sync, 384-zone FALD for HDR, factory calibration report, Asus Aura Sync technology, ROG Light Signal, ROG Light Signature, Ambient Light Sensor Colour Gamut Extended gamut up to 97% DCI-P3,

99% Adobe RGB

~125% sRGB The PG27UQ offers a limited range of connectivity options given the use of an NVIDIA G-sync module. However, it does offer the latest generation of DisplayPort 1.4 which allows support for the very high bandwidth needed to power the screen at 3840 x 2160 @ 144Hz and with HDR. There is also an HDMI 2.0b port for connection of external devices like games consoles (60Hz maximum). Both ports support HDCP 2.2 and can handle HDR content, so you can use HDR from your PC as well as compatible games consoles and Ultra HD Blu-ray players. There is an additional 2 port USB 3.0 hub, with the ports located on the back of the screen and a headphone jack too. The screen has an external power supply and comes packaged with the power cable and brick you need. Below is a summary of the features and connections of the screen: Feature Yes / No Feature Yes / No Tilt adjust DVI Height adjust HDMI Swivel adjust D-sub Rotate adjust DisplayPort VESA compliant Component USB 2.0 Ports Audio connection USB 3.0 Ports HDCP Support Card Reader MHL Support Ambient Light Sensor Integrated Speakers Human Motion Sensor PiP / PbP Touch Screen Blur Reduction Mode Factory calibration G-Sync Hardware calibration FreeSync Uniformity correction Wireless charging



Design and Ergonomics

Above: front view of the screen. Click for larger version The PG27UQ comes in a mixture of black, "Armor Titanium" (dark grey) and "Plasma Copper" finishes. There is a modestly sized matte black plastic bezel around all 4 sides of the screen measuring 16mm along the sides, and 21mm along the top and bottom. There is a small shiny silver ROG logo in the middle of the bottom bezel, a subtle medium grey "NVIDIA G-Sync HDR" label in the bottom left hand corner and subtle medium grey OSD control labels on the right hand edge of the screen. A power LED is located on the bottom right hand edge of the screen and glows white during normal operation, and amber in standby. This is out of sight when using the screen from a typical viewing position.

Above: front side views of the screen. Click for larger versions The stand is predominantly a dark silver "Armor Titanium" colour including a strong and sturdy metal 3-pronged base. There are some "Plasma copper" coloured trim sections on the bottom of the stand as you can see from the photos. There is a cable tidy hole in the bottom part of the stand and the "ROG Light Signature" projects a red logo on to the bottom of your desk. That can be turned on or off via the 'Light in Motion' option in the OSD menu.

Above: rear side views of the screen. Click for larger versions The back of the screen is encased in a matte black plastic with some etched patterns on half of it. The OSD control joystick and buttons are located on the back right hand side (when viewed from the front). Also on the back of the screen is a larger ROG logo which glows different colours if you activate it via the OSD menu. You can either set it to a range of different colour modes, cycles or effects using the 'Aura RGB' section, or you can sync this with your other 'Aura Sync' devices like keyboards, mouse etc if you have them. When it's turned off, that logo actually looks like a shiny silver section which makes it look nice and eye-catching even with the lighting turned off.

Above: rear angled view of the screen. Click for larger version The stand attaches in to the middle of the screen but can be removed to reveal a VESA 100mm mounting option if you wish. All the lighting features are built in to the stand so you would lose those of course if you removed the provided stand. In the top of the stand is another smaller ROG logo which glows red if you have turned on the 'Light in Motion' ROG Light Signature which projects from the bottom of the stand. There is also a small red dot you can see on the top of the stand in the image above. This is the 'ROG Light Signal' which projects a red ROG logo on to the ceiling or wall behind the screen. You can change the angle of this projection using a small scroll wheel on the back of the stand. All these lighting features are quite fun, and we expect some users will want to have them turned on to enhance the appearance of their gaming setup and to grab attention. You can of course turn them off, but they do help to add a bit of a premium feel to the screen through some added gadgets we felt.

Above: rear view of the screen. Click for larger version

Above: side view of the screen. Click for larger version The side view of the screen is not as thin as some modern monitors and that is because of the extra size of the FALD backlight unit. The stand is also quite chunky, but it does provide a very sturdy and strong base for the screen which was pleasing. There is a good range of ergonomic adjustments offered by the stand. Tilt offers a wide range and is smooth to move, if a little stiff to operate. There is a 120mm height adjustment which smooth and easy to move. At the lowest setting the bottom edge of the screen is 60mm from the top of the desk, and 180mm when at maximum height extension. Side to side swivel is provided and is smooth and a little stiff to use. Rotation to portrait mode is also included and that is surprisingly smooth and easy to move. It can often be quite clunky and stiff on some monitor stands. There is pretty much no wobble at all from the screen when you re-position it, and the stand is providing a very sturdy and stable base. A summary of the ergonomic adjustments are shown below: Function Range Smoothness Ease of Use Tilt Yes Smooth A little stiff Height 120mm Smooth Easy Swivel Yes Smooth A little stiff Rotate Yes Smooth Easy Overall Very good set of adjustments and all easy to move. Screen remains stable with no wobble. The OSD control joystick and buttons are located on the back right hand side (when viewed from the front). There is quick access to the GamePlus extra options like the FPS counter and crosshair from one button, and access to the GameVisual preset mode menu from another. The joystick can then be used to control the rest of the menu quickly and easily. We found this worked very well and was fast and intuitive to navigate through the various options. We saw no issues with the quality of the joystick control on our sample, it was not flimsy and didn't get stuck at all which was good. There was a wide range of options available in the menu as well, including a good range of preset modes, colour controls, image boosting options and controls for all the extra lighting and added features.

Above: On the right, connection options on the back of the screen (when rotated on stand). Click for larger version The back of the screen features the connections. There is HDMI 2.0, DisplayPort 1.4, USB upstream and 2x USB 3.0 downstream and 1x headphone jack connections provided. Above: dismantled view of the internal cooling fan. Photo courtesy of PcPer.com who did a nice tear-down of the screen One thing we should mention is that there is a small internal fan in this screen which is needed to ensure it stays cool enough, especially during high refresh HDR gaming. It helps keep the G-sync module and FALD backlight cooler. We have seen small fans used in screens before, for instance the RGB backlit Samsung XL20 from 2007 needed one as well because of the advanced backlight unit. You can hear the fan on the PG27UQ if you listen closely for it, and if you have an otherwise silent PC setup you will notice it. It is quiet and certainly we found that it was not audible beyond our normal couple of PC fans which are fairly quiet. We would have course preferred it without the fan, and it's likely to bother silent PC enthusiasts but it wasn't a major issue we felt.



Power Consumption In terms of power consumption the manufacturer lists a typical usage of 180W with HDR on, but don't list any other specs. We carried out our normal tests to establish its power consumption ourselves in a few states. State and Brightness Setting Manufacturer Spec (W) Measured Power Usage (W) Default (60%) - 69.3 Calibrated (18%) - 45.1 Maximum Brightness (100%) - 90.5 Minimum Brightness (0%) - 35.5 Standby - 1.4 Out of the box the screen used 69.3W at the default 60% brightness setting. Once calibrated the screen reached 45.1W consumption, and in standby it used only 1.4W. We have plotted these results below compared with other screens we have tested. The consumption (comparing the calibrated states) is pretty similar to the other FALD display we've tested, the Dell UP2718Q which is probably to be expected. These FALD backlit displays use quite a lot more power than traditional W-LED backlight models, and so the PG27UQ uses a similar amount of power in fact to a much larger 34 - 35" screen.



Panel and Backlighting Panel Manufacturer AU Optronics Colour Palette 1.07 billion Panel Technology AHVA (IPS-type) Colour Depth 8-bit + FRC Panel Module M270QAN02.2 Colour space Extended gamut Backlighting Type Direct LED with Quantum Dot coating. 384-zone FALD for HDR Colour space coverage (%) Up to 97% DCI-P3 quoted

99% Adobe RGB

~125% sRGB Panel Part and Colour Depth The Asus ROG Swift PG27UQ features an AU Optronics M270QAN02.2 AHVA (IPS-type) technology panel which is capable of producing 1.07 billion colours. This is achieved through a 8-bit+FRC colour depth as detailed in the manufacturers specification. Some people may complain that the panel is not a native full 10-bit panel, but in reality you are going to be very hard pressed to see any real difference in practice between a good 8-bit+FRC panel and a true 10-bit panel. Even more so when you consider whether you're going to actually be able to use the 10-bit colour depth in real use. This screen is aimed at gaming of course, and NVIDIA gaming graphics card users. There is a bit of confusion online about whether these consumer grade graphics cards can truly support 10-bit or not so we will try and clear that up a bit here. NVIDIA Geforce graphics cards have been able to support 10-bit colour depth output actually since the 200 series GPU's as confirmed by NVIDIA themselves. The important thing to note though is that for Windows users this is for Direct X applications like games only, and does not apply for professional applications like Adobe Premiere Pro or Adobe Photoshop. So you can use an NVIDIA Geforce consumer-grade graphics card for 10-bit colour depth in gaming, as long as it is a game which support that colour depth. This is of course particularly relevant here for HDR gaming where a 10-bit colour depth is widely available.

Above: 10-bit colour depth selection in the NVIDIA control panel However, while the NVIDIA Geforce cards can support 10-bit for DirectX, this is not supported for the aforementioned professional applications like Photoshop. Those programs use OpenGL 10-bit colour buffers which are not supported from the NVIDIA Geforce cards. You would need an NVIDIA Quadro professional grade card for 10-bit support in those professional applications. Achieving 10-bit colour depth can be quite tricky, as it requires an end to end 10-bit workflow including software/game > relevant graphics card > supported drivers > supported operating system > supported display interface > supported display. The good news is that the PG27UQ will support 10-bit content and given this is firmly aimed at gamers, that will mean most will use that support from their NVIDIA Geforce card when it comes to HDR gaming, but not be able to make use of it for any professional applications. Just make sure you have all the relevant software and operating systems in place if you want to use it. The panel part is confirmed when dismantling the screen as shown above. Photo courtesy of PcPer.com who did a nice tear-down of the screen.

Screen Coating The screen coating is a light anti-glare (AG) offering. It isn't a semi-glossy coating, but it is light as seen on other modern IPS type panels. Thankfully it isn't a heavily grainy coating like some old IPS panels feature and is also lighter than modern TN Film panel coating. It retains its anti-glare properties to avoid too many unwanted reflections of a full glossy coating, but does not produce too grainy or dirty an image that some thicker AG coatings can. There are no visible cross hatching patterns on the panel coating.

Backlight Type and Colour Gamut The screen uses a Direct LED backlight unit with an added Quantum Dot Enhancement Film (QDEF) coating to extended the colour space and gamut. This allows for a high coverage of the DCI-P3 colour space which is the reference used for HDR content and displays and something you will see more commonly talked about with TV's and monitors in the future. This screen offers "up to 97% coverage" of the DCI-P3 colour space according to the specs, something that we will verify and test in a moment. This also allows for 99% coverage of the Adobe RGB colour space, and corresponds to around 125% of the commonly used sRGB reference. Basically the screen is capable of producing a wide range of colours than most monitors, which are normally based around providing coverage of the common sRGB colour space. With the Quantum Dot coating film, the PG27UQ can cover beyond that, producing more bright and vivid colours to enhance gaming, multimedia and HDR content. High coverage of the DCI-P3 colour space is a requirement if a display is to conform to common HDR standard such as the Ultra HD Premium certification (used in the TV market predominantly) and the new VESA DisplayHDR certifications. If you want to read more about colour spaces and gamut then please have a read of our detailed article.

Backlight Dimming and Flicker We tested the screen to establish the methods used to control backlight dimming. Our in depth article talks in more details about a previously very common method used for this which is called Pulse Width Modulation (PWM). This in itself gives cause for concern to some users who have experienced eye strain, headaches and other symptoms as a result of the flickering backlight caused by this technology. We use a photosensor + oscilloscope system to measure backlight dimming control with a high level of accuracy and ease. These tests allow us to establish 1) Whether PWM is being used to control the backlight

2) The frequency and other characteristics at which this operates, if it is used

3) Whether a flicker may be introduced or potentially noticeable at certain settings If PWM is used for backlight dimming, the higher the frequency, the less likely you are to see artefacts and flicker. The duty cycle (the time for which the backlight is on) is also important and the shorter the duty cycle, the more potential there is that you may see flicker. The other factor which can influence flicker is the amplitude of the PWM, measuring the difference in brightness output between the 'on' and 'off' states. Please remember that not every user would notice a flicker from a backlight using PWM, but it is something to be wary of. It is also a hard thing to quantify as it is very subjective when talking about whether a user may or may not experience the side effects.

100% 50% 0%



Above scale = 1 horizontal grid = 5ms At all brightness settings a constant Direct Current (DC) voltage is applied to the backlight, and the screen is free from the obvious off/on switching of any PWM dimming method. As a result, the screen is flicker free as advertised. Pulse Width Modulation Used No Cycling Frequency n/a Possible Flicker at 100% Brightness No 50% Brightness No 0% Brightness No

Brightness and Contrast We wanted to measure the luminance range available from the backlight as well as see how much variance there was in the screens contrast as we adjusted the monitor setting for brightness. In theory, brightness and contrast are two independent parameters, and good contrast is a requirement regardless of the brightness adjustment. Unfortunately, such is not always the case in practice. We recorded the screens luminance and black depth at various OSD brightness settings, and calculated the contrast ratio from there. Graphics card settings were left at default with no ICC profile or calibration active. Tests were made using an X-rite i1 Display Pro colorimeter. It should be noted that we used the BasICColor calibration software here to record these, and so luminance at default settings may vary a little from the LaCie Blue Eye Pro report. OSD Brightness Luminance

(cd/m2) Black Point (cd/m2) Contrast Ratio

( x:1) 100 532.29 0.49 1086 90 501.83 0.47 1068 80 446.69 0.41 1089 70 397.29 0.37 1074 60 346.94 0.33 1051 50 292.13 0.27 1082 40 236.34 0.22 1074 30 185.85 0.17 1093 20 129.76 0.12 1081 10 73.03 0.07 1043 0 24.01 0.02 1200 Total Luminance Adjustment Range (cd/m2) 508.28 Brightness OSD setting controls backlight? Total Black Point Adjustment Range (cd/m2) 0.47 Average Static Contrast Ratio 1086:1 PWM Free? Recommended OSD setting for 120 cd/m2 19 At the top end the maximum luminance reached a very high 532 cd/m2 which was extremely bright, although a little less than the specified maximum brightness of 600 cd/m2 from the manufacturer for SDR content. It is the FALD backlight that allows for this improved brightness range. There was an excellent 508 cd/m2 adjustment range in total, so at the minimum setting you could reach down to a very low luminance of 24 cd/m2. This should be more low enough for most people including those wanting to work in darkened room conditions with low ambient light. A setting of 19 in the OSD menu should return you a luminance of around 120 cd/m2 at default settings. It should be noted that the brightness regulation is controlled without the need for Pulse Width Modulation for all brightness settings so the screen is flicker free. 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. This is almost a linear relationship as you can see, with a slightly less steep adjustment curve between 100 and 90% brightness settings. We were impressed by the wide range offered here. The average contrast ratio of the screen was measured at 1086:1 which was good for an IPS-type panel. This remains pretty stable across the brightness adjustment range, with a small increase at the lowest settings between 10 and 0%.

SDR Contrast Ratio with FALD Active (updated 6/8/18) Note that the figures above are for the static contrast ratio without the 'variable backlight' (Full Array Local Dimming) turned on. That can operate in both SDR and HDR content and can significantly increase the active perceived contrast ratio of the screen. Dark areas are dimmed, and brighter areas are turned up. With a screen calibrated to around 120 cd/m2 and FALD active in SDR mode we measured a black depth of 0.02 cd/m2 and therefore an active contrast ratio of ~6000:1. This was for where a small white sample on the screen was compared with a measurement of a black part of the screen furthest away. Actually you can achieve the same black point of 0.02 cd/m2 even when you increase the brightness up to the maximum 100% setting (533 cd/m2 luminance peak), and therefore you can achieve active contrast ratios of around 26,650:1 even in SDR mode. The FALD is capable of producing some very strong active contrast ratios even in SDR content, and you are only really limited by the maximum luminance in terms of how high that contrast ratio will go. HDR contrast will be looked at later on in the review.



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 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 - validates 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

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/m 2 , 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 - we aim for as high as possible. Any dynamic contrast ratio controls are turned off here if present

dE average / maximum - 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 Setup and Factory Calibration The PG27UQ carries a factory calibration which is applicable in the default state of the monitor. This applies in the 'Racing mode' preset and is factory calibrated to achieve accurate grey-scale tracking and a a delta E of <3. It should be noted that the monitor is by default set to produce an sRGB colour space and is set to operate in normal SDR (Standard Dynamic Range) mode. Enabling wide gamut can be done via the OSD menu and we will look at those a bit more in a moment. The screen comes with a specific factory calibration report for the unit as shown by the example which came with ours:

Above: factory calibration report. Click for larger version

Default settings of the screen were as follows: Asus ROG Swift PG27UQ

Default Settings

(Factory Calibration)







Monitor OSD Default Settings GameVisual Racing mode Brightness 60 Contrast 50 Color Temp Normal Gamma 2.2 RGB n/a Luminance Measurements luminance (cd/m2) 355 Black Point (cd/m2) 0.34 Contrast Ratio 1051:1 Colour Space Measurements sRGB coverage 97.5% DCI-P3 coverage 71.9% Rec.2020 coverage 51.6% Before we started, we turned off the 'variable backlight' option within the OSD menu. That controls the FALD backlight and can be used in SDR and HDR modes to dim and brighten different areas of the screen depending on the content to enhance the contrast and dynamic range. We wanted to test the screen out of the box without this happening, particularly so we could accurately measure the luminance and static contrast ratio of the panel. Initially out of the box the screen was set with the GameVisual preset mode set to 'Racing mode' and the other default settings shown above. The screen felt very bright to the naked eye, even though the brightness control was set at a fairly modest 60% - a lot of screens come set at 100%. Colour balance felt very good and you could tell that out of the box the screen was operating with a standard sRGB colour space. 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 monitors colour gamut (black triangle) matches the sRGB colour space reference (orange triangle) closely. We measured using ChromaPure software a 97.5% sRGB gamut coverage which corresponds to 71.9% of the DCI-P3 reference and 51.6% of the Rec.2020 reference. This was pretty comparable to Asus' factory measurements recording in the calibration report of 98.5% sRGB. Remember, the screen is set to operate in an sRGB emulation mode out of the box while in SDR settings, and so you are not seeing the full range of colours possible from the backlight and Quantum Dot coating. It's very easy to switch up to the wide gamut mode in the OSD menu using the 'Display SDR input' option, switching that from sRGB to wide gamut.

Above: colour space coverage when switched to the 'wide gamut' mode in the OSD menu Colour Space Measurements in wide gamut mode (SDR) sRGB coverage 149.6% DCI-P3 coverage 110.3% Rec.2020 coverage 79.1% If you switch to this wide gamut mode you can see an immediate and noticeable difference to the colours. They look far more bright and vivid, as is typical for a screen based on a wide gamut backlight. The CIE diagrams above show that the monitors colour space now stretches a considerable way beyond the sRGB reference space, and quite closely matches the Adobe RGB reference. We measured a coverage of 149.6% sRGB, 110.3% DCI-P3, 79.1% Rec. 2020 in this wide gamut mode which was actually quite a bit wider than even the advertised spec. The gamma and white point performance remain the same regardless of whether you switch to sRGB or wide gamut mode. Default gamma of the screen was recorded at 2.2 average, with a very small 2% deviance from the target which was great news. The gamma looked to be a little off in the darker grey shades. White point was measured at a pretty accurate 6315k being only a small 3% out from our 6500k target. Luminance was recorded at a very bright 355 cd/m2 which is far too high for prolonged general use, you will need to turn that down. The screen was set at a default 60% brightness in the OSD menu but that is easy to change of course to reach a more comfortable setting without impacting any other aspect of the setup. The black depth was 0.34 cd/m2 at this default brightness setting, giving us a good static contrast ratio for an IPS-type panel of 1051:1. We have seen some IPS panels reach up to around 1200 - 1400:1 recently but somewhere around 1000:1 is still decent for this technology. Remember that the active contrast ratio will be significantly enhanced if you operate the 'variable backlight' FALD in both normal SDR mode and when using HDR mode and content. We will test that more later on. Colour accuracy was really excellent out of the box with an average dE of 0.4 and a maximum of 1.3 - to the point where we let out an audible "wow" when we first saw the results generated. Testing the screen with colour gradients showed smooth gradients with only very minor gradation evident in the darker tones. There was no sign of any colour banding which was good news. Overall this was a really good factory calibration with accurate gamma and white point, very good colour accuracy and reliable emulation of the sRGB colour space, with the ability to easily switch to the wide gamut mode if you want. We weren't sure how this was going to work before testing the screen in relation to the colour space and Quantum Dot film coating, but it was great to see the availability of an sRGB mode for those who want to use the screen for other things beyond gaming and multimedia. Sure, you might want the boosted, more vivid colours of the wide gamut capability for those uses, but unless you're specifically working with wide gamut content in a colour managed workflow, you will probably want to use the sRGB mode for photo, colour work and more general office uses.

Color Temp Setting Measurements Colour Temp OSD setting White point measurement Normal 6315k Warm 5201k Cool 6962k User 6315k We carried out a test of the various Color Temp modes as well out of interest and the results as shown above. The normal mode was closest to our 6500k target which was good news. The other modes behaved as they should, offer various options for a cooler or warmer setup. The User mode was the same as the normal mode by default, but gives you access to the RGB channels for customised calibration. Gamma Setting Measurements Gamma OSD setting Measured average gamma 1.8 1.8 2.0 2.0 2.2 2.2 2.4 2.4 2.6 2.6 We also carried out measurement of each of the gamma modes available via the OSD menu. Some of the GameVisual preset modes have different default settings for gamma as well keep in mind, and you can always customise some of the presets to your liking. All of the modes showed a really reliable average gamma in keeping with the desired target which was excellent. You can have faith in the setting to deliver the gamma curve it says it will.



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 colorimeter was used to validate the black depth and contrast ratios due to lower end limitations of the i1 Pro device. Asus ROG Swift PG27UQ

Calibrated Settings







Monitor OSD Default Settings GameVisual Racing mode Brightness 18 Contrast 50 Color Temp User Gamma 2.2 RGB 96, 98, 100 Luminance Measurements luminance (cd/m2) 119 Black Point (cd/m2) 0.11 Contrast Ratio 1071:1 Colour Space Measurements sRGB coverage 97.5% DCI-P3 coverage 71.9% Rec.2020 coverage 51.6% We changed here to the user mode in the colour temp menu which gives you access to the RGB channel adjustments. We stuck with the default 2.2 gamma mode which we knew to be very close to the target out of the box, thanks to the excellent factory calibration. 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. Average gamma was measured at 2.2 average (0% deviance) which fixed the very small 2% deviance we'd seen out of the box at default settings. The accurate white point of the default mode was maintained here, but we corrected the small 3% deviance and we now measured a colour temperature of 6498k, spot on with our target basically. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at a far more comfortable 119 cd/m2. This left us a black depth of 0.11 cd/m2 and a static contrast ratio of 1071:1 which was good for IPS panel technology. Colour accuracy of the resulting profile was excellent too, with dE average of 0.3 and maximum of 0.9. LaCie would consider colour fidelity to be excellent. Testing the screen with various colour gradients showed very smooth transitions with only some very minor gradation in darker tones. You can use our settings and try our calibrated ICC profile 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.





Calibration Performance Comparisons The comparisons made in this section try to give you a better view of how each screen performs, particularly out of the box which is what is going to matter to most consumers. We have divided the table up by panel technology as well to make it easier to compare similar models. When comparing the default factory settings for each monitor it is important to take into account several measurement areas - gamma, white point and colour accuracy. There's no point having a low dE colour accuracy figure if the gamma curve is way off for instance. A good factory calibration requires all 3 to be well set up. We have deliberately not included luminance in this comparison since this is normally far too high by default on every screen. However, that is very easily controlled through the brightness setting (on most screens) and should not impact the other areas being measured anyway. It is easy enough to obtain a suitable luminance for your working conditions and individual preferences, but a reliable factory setup in gamma, white point and colour accuracy is important and some (gamma especially) are not as easy to change accurately without a calibration tool. From these comparisons we can also compare the calibrated colour accuracy, black depth and contrast ratio. After a calibration the gamma, white point and luminance should all be at their desired targets. The PG27UQ carries an excellent factory calibration that we were really impressed with, especially considering this is primarily a gaming screen and those are often set up for less "accurate" targets. We had a good gamma curve and white point with only a couple of % deviance from the targets, and an excellent dE of only 0.4 out of the box. No complaints about the default setup here. When it comes to black depth and contrast ratio the screen performed well for an IPS-type panel, with a calibrated contrast ratio of 1071:1. We have seen some modern IPS panels start to reach up to 1200 - 1400:1 or so as you can see above, but somewhere around 1000:1 is still respectable for this technology, with some others dipping under that down to the 800 - 900:1 range. You can see that IPS cannot compete with VA technology panels though which typically reach up to 2000:1 or more. Note that this is the static contrast ratio without the 'variable backlight' (Full Array Local Dimming) turned on. That can operate in both SDR and HDR content and can significantly increase the active contrast ratio of the screen. Dark areas are dimmed, and brighter areas are turned up. With a screen calibrated to around 120 cd/m2 and FALD active in SDR mode we measured a black depth of 0.02 cd/m2 and therefore an active contrast ratio of ~6000:1. This was for where a small white sample on the screen was compared with a measurement of a black part of the screen furthest away. Actually you can achieve the same black point of 0.02 cd/m2 even when you increase the brightness up to the maximum 100% setting (533 cd/m2 luminance), and therefore you can achieve active contrast ratios of around 26,650:1 even in SDR mode. HDR contrast will be looked at later on in the review. Check Pricing and Buy - Direct Links Amazon USA | Amazon UK | Overclockers UK | Amazon GER | Amazon CAN TFTCentral is a participant in the Amazon Services LLC Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com, Amazon.co.uk, Amazon.de, Amazon.ca and other Amazon stores worldwide. We also participate in a similar scheme for Overclockers.co.uk.



Viewing Angles

Above: Viewing angles shown from front and side, and from above and below. Click for larger image Viewing angles of the screen were very good as you would expect from an IPS-type panel. Horizontally there was very little colour tone shift until wide angles past about 45°. A slight darkening of the image occurred horizontally from wider angles as you can see above as the contrast shifted slighting. Contrast shifts were slightly more noticeable in the vertical field but overall they were very good. The screen offered the wide viewing angles of IPS technology and was free from the restrictive fields of view of TN Film panels, especially in the vertical plane. It was also free of the off-centre contrast shift you see from VA panels and a lot of the quite obvious gamma and colour tone shift you see from some of the modern VA panel type offerings.

Above: View of an all black screen in a dark room from the side. Click for larger version On a black image we were very pleased to learn that this was a low-glow panel, and did not show the usual pale/white/purple off-angle glow on dark content that most IPS panels can suffer from. Here, the black remained fairly stable, with only low amounts of glow visible. The image above was taken with the FALD variable backlight turned off. If you turn that on, it will operate even for SDR content and on an all-black screen and on darker content it makes a significant improvement again. Blacks become darker, and any low amount of IPS-glow is reduced as a result. You can compare the performance here to the AU Optronics IPS-type panel used in the earlier Asus ROG Swift PG279Q (144Hz IPS-type, 1440p resolution) which shows a far more noticeable white glow which is pretty standard for most IPS-type panels.



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 35 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

The PG27UQ had a fairly good uniformity overall. The upper portion of the screen was a little darker than the rest where it dropped down to 102 cd/m2 in the most extreme example (-17.65% deviance). Apart from this upper region, the rest of the screen was all within an acceptable 10% deviance from the centrally calibrated point which was good news. In total, 80% of the screen was within this deviance threshold.



Backlight Leakage



Above: All black screen in a darkened room. Click for larger version We also tested the screen with an all black image and in a darkened room. A camera was used to capture the result, here with the FALD variable backlight turned OFF at our calibrated settings. The camera showed there was no noticeable backlight bleed or clouding on this sample and uniformity was very good. With FALD turned on, the black becomes even darker still. Note: if you want to test your own screen for backlight bleed and uniformity problems at any point you need to ensure you have suitable testing conditions. Set the monitor to a sensible day to day brightness level, preferably as close to 120 cd/m2 as you can get it (our tests are once the screen is calibrated to this luminance). Don't just take a photo at the default brightness which is almost always far too high and not a realistic usage condition. You need to take the photo from about 1.5 - 2m back to avoid capturing viewing angle characteristics, especially on IPS-type panels where off-angle glow can come in to play easily. Photos should be taken in a darkened room at a shutter speed which captures what you see reliably and doesn't over-expose the image. A shutter speed of 1/8 second will probably be suitable for this.



General and Office Applications The PG27UQ feature a 3840 x 2160 Ultra HD resolution, all packed in to a 27" sized screen. The higher resolution is not about providing more screen real-estate here and we need to move away from thinking about LCD resolution in that manner. In fact it is arguable that the wide range of 2560 x 1440 resolution panels in the 27" sector are about as high a resolution as you want to go, without making fonts and icons too small natively. That provides a pretty comfortable option to work with day to day. Here, with the resolution being so much higher it is about providing a sharper and crisper image, while still operating with a similar desktop area and similar font size to the 1440p models. It is providing a higher pixel density (Pixels Per Inch, PPI) to improve the degree of definition to the image. You need to us operating system scaling to handle this properly. If you try and run the screen without any scaling at 3840 x 2160 the 0.156mm pixel pitch makes everything far too small and tiny. In our view you need a screen of about 39 - 40" in size (like the Philips BDM4065UC for example) to use an Ultra HD or 4K resolution effectively without OS scaling. On this 27" model, if you increase the scaling to 150%, you actually end up with the same workspace area as 2560 x 1440, but at a much higher PPI pixel density - and therefore a sharper image. Have a read of Eizo's very useful article for some more information on the whole matter. For those wanting a high pixel density for CAD, design, photo work etc, this is a really good option. The image was very sharp and crisp and text was very clear. It is a little debatable whether you will gain much benefit from the higher PPI on a screen this size compared with a 2560 x 1440 standard model, but some may notice picture quality and sharpness improvements. Keep in mind that not all Operating Systems and applications handle scaling the same. More recent versions of Windows (8.1 and 10) tend to handle it all better, and recent versions of Mac OS are pretty solid as well. Some applications and games don't handle scaling correctly and so you can end up with some things with very minute text and fonts and some things which don't scale completely in every place. Keep this in mind if you're selecting any super high resolution display as it could be an important factor. You need to ensure you have the necessary operating system and applications to handle scaling effectively for your needs. The light AG coating of the panel is welcome, and much better than the grainy and 'dirty' appearance of older IPS AG coatings. The wide viewing angles provided by this panel technology on both horizontal and vertical planes, helps minimize on-screen colour shift when viewed from different angles. The default setup of the screen was excellent as well, offering an accurate gamma curve, accurate white point, very low dE for great colour accuracy and decent contrast ratio for an IPS panel. This is thanks to the excellent factory calibration. There is support to run the screen in a normal sRGB gamut emulation (which is very reliable), or the full wider gamut produced by the backlight and Quantum Dot film. As a result, for those wanting to work with wide gamut content you can achieve good coverage of the Adobe RGB reference space and around 110% of the DCI-P3 colour space as well. The brightness range of the screen was also very good, with the ability to offer a luminance between 532 and 24 cd/m2. This should mean the screen is perfectly useable in a wide variety of ambient light conditions, including darkened rooms. A setting of 18 - 19 in the OSD brightness control should return you a luminance close to 120 cd/m2 out of the box. On another positive note, the brightness regulation is controlled without the need for the use of Pulse-Width Modulation (PWM), and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry. A range of blue light filter modes are provided to help reduce blue spectral output and make the screen easier on the eyes, especially for lots of text work or in darker room conditions. The screen offers 2x USB 3.0 ports which is very handy although they are located on the back of the screen with the video connections so aren't really easy access. There is also a headphone jack if you are sending sound to the screen via HDMI, although there's no integrated speakers offered here. There is a built in ambient light sensor which is located on the top edge of the screen and is accessible via the 'Auto SDR brightness' setting in the OSD. We found that this made the image darker than we might like by default compared with our calibrated state. You can change the brightness control though to set your normal brightness level in your normal working conditions, and then let the auto sensor adjust this up and down in line with any changes to your ambient light conditions throughout the day. There aren't any other extras like card readers provided here which are sometimes useful on office environments. The stand offers a wide range of adjustments which is great news, allowing you to obtain comfortable viewing positions easily.



Responsiveness and Gaming Introduction and Testing Methodology Panel Manufacturer and Technology AU Optronics AHVA (IPS-type) Panel Part M270QAN02.2 Quoted G2G Response Time 4ms G2G (with OD) Quoted ISO Response Time n/a Overdrive Used Yes Overdrive Control Available Via OSD Setting OD Overdrive OSD Settings Off, Normal, Extreme Maximum Refresh Rate 60Hz (HDMI)

120Hz (native)

144Hz (with overclock) Variable Refresh Rate technology NVIDIA G-Sync Variable Refresh Rate Range 30 - 120/144Hz Blur Reduction Backlight n/a The PG27UQ is rated by Asus as having a 4ms G2G response time. The screen uses overdrive / response time compensation (RTC) technology to boost pixel transitions across grey to grey changes as with nearly all modern displays. There is a user control in the OSD menu for the overdrive under the 'OD' setting with 3 options available - Off, Normal and Extreme. The part being used is AU Optronics M270QAN02.2 AHVA (IPS-type) technology panel. 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 and System Considerations Check Pricing and Buy - Direct Links NVIDIA Geforce Graphics Cards:

Amazon USA | Amazon UK | Overclockers UK | Amazon GER | Amazon CAN TFTCentral is a participant in the Amazon Services LLC Associates Programme, an affiliate advertising programme designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com, Amazon.co.uk, Amazon.de, Amazon.ca and other Amazon stores worldwide. We also participate in a similar scheme for Overclockers.co.uk. Our thanks to Asus for also loaning us a ROG NVIDIA Geforce GTX 1080 graphics card to allow full testing of this screen. You will need to keep in mind that the PG27UQ is a very top-end display and to power it, you are going to need a powerful system for sure. Achieving 3840 x 2160 resolution at up to 144Hz refresh rate and for HDR gaming at high settings is going to be a challenge for even the best systems so to really make use of this display you are going to also need to invest in other expensive, powerful hardware. Note that it is important that your graphics card has a DisplayPort 1.4 interface as you are going to need that to achieve 4K at these high refresh rates. Asus provide a DP cable in the box so you don't need to worry about that thankfully. Is 4K too high a resolution for a 27" screen like this? That's another common question we see asked, and a lot of people would prefer it if the screen was a little bigger in size. AU Optronics who produce the panel used here are also now planning a 32" equivalent. Panel production was originally expected around Q3 2018 but our most recent information suggests this has slipped back to Q1 2019, presumably because of the delays and challenges with the 27" versions. It will not be until probably middle of 2019 at best before any monitors featuring those panels we expect right now. Given how many times the 27" panel slipped, we wouldn't be surprised to see the same with the larger 32" version. At 27" in size, the Ultra HD resolution can't really be used for desktop / general use without scaling in place, as the fonts and text are just too small. For gaming and multimedia you do get an improvement in the image sharpness and clarity thanks to the smaller pixel pitch and higher PPI. Depending on your viewing distance, eye sight and game settings you may or may not notice the difference in running at 4K resolution on a 27" screen compared with a more common 1440p display. However, there are plenty of people out there who do notice the difference and have invested in 4K resolution screens of various sizes, many in this kind of range, and love that extra level of detail and clarity they get.

Response Times 60Hz (Consoles)



We carried out some initial response time measurements in each of the overdrive settings, along with some visual tests in order to identify what the optimal setting was. These tests were initially carried out at 60Hz which is going to be your limit on this screen if you're connecting a games console over HDMI at 3840 x 2160 Ultra HD resolution. With the OD setting 'off' the average G2G response times were fairly slow at 12.9ms G2G which is quite typical for an IPS-type panel. Switching up to 'normal' mode brought about some noticeable improvements to motion clarity and reductions in the measured response times, and perceived blurring on moving images. Average G2G was now measured at 9.3ms, and there was thankfully no overshoot problems introduced. Pushing up to the 'extreme' setting helped reduce the response times a little more, down to 8.2ms G2G now. A small amount of overshoot was introduced, but it was minimal and not really noticeable in practice. Response times were more than adequate to keep up with the 60fps frame rate at 60Hz, and we would recommend opting for the 'Extreme' mode if you're gaming from a console or running at 60Hz.

High Refresh Rates and 120Hz 98Hz Refresh Rate 120Hz Refresh Rate

When connected to a PC using the DisplayPort 1.4 interface you have access to the high refresh rate of the panel. The maximum native refresh rate supported is 120Hz, which we will remind you is a big step up for panels of this 4K resolution. The overdrive behaviour of the screen does vary depending on the active refresh rate. We measured the response times with and without G-sync activated in the NVIDIA control panel incidentally, and it had no real impact to the measurements. We didn't bother testing the 'off' mode here, but the 'normal' mode showed a good improvement compared with at 60Hz, with average G2G response time improving from 9.3ms to 6.9ms when at 98Hz, and a little lower at 6.6ms at 120Hz. The reason for testing 98Hz will become clearer later on in the review but gives a good mid-way measurement as well between 60 and 120Hz. There was still no overshoot issues at all which was great news in the 'normal' OD mode. These improvements in response times helps ensure the screen can keep up with the increased frame rates. At 120Hz, a new frame is sent to the screen every 8.33ms (1000ms / 120 frames = 8.33ms) and so the pixel response times need to be consistently and reliably below that to ensure optimal experience. This also avoids any additional blurring and smearing which can commonly appear if the response times are not fast enough to keep up with the frame rate. Motion tests in practice showed smoother and clearer moving images, helped by the improvements to pixel response times but mainly because of the doubling of the refresh rate. Pushing the OD setting up to the maximum 'extreme' setting improved the response times slightly, but unfortunately a large amount of overshoot was introduced, and you could see dark trails and artefacts on moving content. We would recommend sticking with the 'normal' mode if you are using the screen for refresh rates above 60Hz. This also applies if you are going to be using NVIDIA G-sync where refresh rate range might fluctuate within the refresh rate range supported. The presence of NVIDIA G-sync is very important on this screen given the huge system demands of powering a screen at 4K resolution. This will dynamically control the refresh rate and remove tearing and stuttering without any of the added lag that older vsync technology causes. G-sync works by synchronizing the display’s refresh interval with the incoming frame rate, banishing lag and ensuring gameplay stays buttery-smooth even when there are large changes in system rendering times. Its presence helps eliminate jarring visual artifacts, and even allows a single, high-performance graphics card to leverage many of the PG27UQ’s benefits. One thing sadly missing from this screen is support for an ULMB (Ultra Low Motion Blur) strobing backlight. This was not possible to include with the FALD backlight sadly. Although G-sync is far more useful and valuable anyway given the high demands of the 4K resolution and high refresh rates. You can't use ULMB and G-sync at the same time, so even if it was available, it would not be as useful as the G-sync variable refresh rate support.

Overclocking and 144Hz The PG27UQ can also support an overclocked refresh rate of 144Hz if you really want to push the capabilities of the DisplayPort 1.4 connection and be at the bleeding edge of refresh rate and resolution support. There are a few things you need to do and be aware of to use 144Hz, some of which sound a bit complicated but actually aren't (if we can hopefully explain them clearly for you). First the simple part. You need to enable the overclocked refresh rate in the OSD menu as shown above. The screen reboots and it should then be an available option in the NVIDIA graphics card control panel. We would recommend using the provided DisplayPort cable, or a high quality cable to ensure support and stability for 144Hz. We had no issues enabling or using 144Hz from our test system using the provided cable. Once activated on the monitor you should see 144Hz listed as an available refresh rate in the NVIDIA control panel, including when running at the native 3840 x 2160 resolution. To have access to 144Hz refresh rate you need to change the 'output colour format' to YCbCr422 as shown above. We will explain what this is about in the next section. After enabling the 144Hz overclock via the OSD menu and making the necessary setting changes in the NVIDIA control panel we measured the response times again at the optimal 'normal' setting. We could tell from visual tests that the 'extreme' setting continued to show high levels of dark overshoot as it had done at 120Hz in our tests above. At 144Hz there was again a small improvement to response times, now lowering to 5.9ms G2G from 6.6ms we'd seen at 120Hz. Again this helped ensure pixel transitions were fast enough to keep up with the increased frame rate, as they need to be <6.94ms to keep up at 144Hz. This overclocking feature seemed to work well. You need to be aware of the colour compression that is needed to make 144Hz possible at this resolution which brings us on to....

Chroma Sub-sampling To achieve a "4K" (3840 x 2160, strictly Ultra HD) resolution and high refresh rates the bandwidth capabilities of the latest DisplayPort 1.4 interface are already being pushed to their limit. The interface is just not capable of supporting the really high end of the refresh rate without some sacrifices, and so to achieve the higher end refresh rates you will have to lower the colour support in one of a couple of ways. This might sound like a big sacrifice, but don't be too alarmed. We will try and explain. The easy part here is refresh rates up to 98Hz maximum. That is within the bandwidth capabilities of DP 1.4 without any colour compression being needed, and therefore you can run the screen just like you would any other display. It will support the full 3840 x 2160 resolution, up to 98Hz refresh rate and with 10-bit colour depth support as well if you have a game that can make use of it. As we explained earlier, 10-bit colour depth support is only applicable for gaming on this display given the limitations of Geforce gaming graphics cards, and not for professional applications like Photoshop. This is useful for HDR gaming where 10-bit colour depth is more commonly used and a lot of other games may not even support 10-bit anyway. No colour compression is needed for refresh rates up to 98Hz anyway so 10-bit is there if you need it. If you want to push the screen up to high refresh rates >98Hz then some kind of colour compression is required so that it can fit within the bandwidth capabilities of DP 1.4. There are two ways this can be achieved 1) Drop from 10-bit colour depth to 8-bit - this might not actually make any real difference for many games, especially if they are non-HDR games or just simply don't support 10-bit colour depth. In a game where 10-bit is supported, or in HDR gaming you may see some improvements in colour gradients when using 10-bit over 8-bit but then again in some cases you may not see much real difference. For 120Hz refresh rates you can drop the colour depth to 8-bit and then not worry about the chroma sub-sampling discussed below.

2) Use Chroma Sub-sampling - this is a method for compressing the colour information in a signal to save on bandwidth, without significantly impacting the picture quality in many cases. This avoids the need to reduce the luminance information (luma) in the signal which would have a more noticeable impact on picture quality, and this method can help reduce the file size by a significant amount. Chroma sub-sampling is represented by the YCbCr setting in the 'output colour format' section in the graphics card control panel we showed earlier (copied above again for ease of reference). It is listed in a format like 4:4:4, 4:2:2 or in some cases even 4:2:0. We will focus on 4:4:4 and 4:2:2 here as that's what is relevant to this display.



4:4:4 format is just the normal standard, uncompressed colour output where sub-sampling is NOT needed and means that for a sample of 4 (the first digit), there are 4 horizontal samples (second digital) and 4 vertical samples (third digit). That's the norm and usually in the graphics card settings you would see this listed as YCbCr444, or if it's just selected on 'RGB' then that implies no chroma sub-sampling is needed either.

Image courtesy of Rtings.com 4:2:2 is the colour compression option we are interested in here for the PG27UQ. The two chroma components are sampled at half the sample rate of luma. The horizontal chroma resolution is halved. This reduces the bandwidth of an uncompressed video signal by one-third. On this display if you want to run above 98Hz and maintain the 10-bit colour depth output, then you will need to use this 4:2:2 chroma sub-sampling setting in the NVIDIA control panel to allow support.



At 120Hz you can keep a full 4:4:4 chroma (no sub-sampling) and instead drop to 8-bit colour depth and that will also work fine. A lot of games and SDR content aren't even going to support 10-bit anyway. If you want to use the overclocked 144Hz refresh rate you will have to drop to 4:2:2 chroma sub-sampling but it can then support 8-bit and 10-bit colour depth. Here's a summary to try and make it clear: Refresh Rate Colour output Notes Up to 98Hz 10-bit colour depth and 4:4:4 chroma supported 98Hz likely to be more than enough for many users and systems anyway (see comments below) 120Hz Choice to drop either to 8-bit colour depth, or to 4:2:2 chroma sub-sampling If your game doesn't support 10-bit anyway or you see no real difference in practice, probably best to drop to 8-bit and keep the full 4:4:4 chroma sampling 144Hz Must drop to 4:2:2 chroma sub-sampling but will support 10-bit colour depth No choice here but to use 4:2:2 chroma sub-sampling. See below for comments on the impact of that Does Chroma sub-sampling make a difference? You will see that when you switch to YCbCr422 mode (4:2:2 chroma sub-sampling) that the 'output dynamic range' setting in the NVIDIA control panel also switches to 'limited'. We know from some previous screens that often when the graphics card gets accidentally set in limited range, it has a huge impact on the black depth and contrast ratio of the display. That is because a limited RGB range (16 - 235 instead of the normal 0 - 255) clips some dark shades and some bright shades. We were initially concerned about this on the PG27UQ but we need not have worried. When running at 4:2:2 chroma mode there was no noticeable impact to the setup of the screen. Running a test with our i1 Pro 2 showed the same gamma curve, white point and low dE that we'd seen out of the box by default. We measured a static contrast ratio of >1000:1 as well, and carrying out visual tests of the darkest black/grey and brightest grey/white shade samples which showed no noticeable difference between 4:4:4 mode and 4:2:2 mode. There was no limiting of the contrast ratio here which was great news and it appears not to be operating in any limited dynamic range. This applied to SDR content as well as HDR. Where there is an observable difference is when viewing text. For normal day to day PC use like office documents etc, fonts sometimes look more blurred and a little broken in places in 4:2:2 mode, particularly with text on solid coloured backgrounds. This is more noticeable the smaller the fonts get. The compressed colour data makes reading text a problem sometimes if running at 4:2:2 mode although to be honest it's quite slight, and only in certain conditions that you'd really see it. A lot of the time you'd have to go specifically looking for it. This text blurring and clarity issue, where visible, is a commonly observed and known side-effect of the lower chroma sub-sampling on displays.

Chroma sub-sampling 4:4:4 (left) vs. 4:2:2 (right) with size 16 font at 3840 x 2160 resolution



Chroma sub-sampling 4:4:4 (left) vs. 4:2:2 (right) with size 11 font at 3840 x 2160 resolution

Above are some photos taken in 4:4:4 mode and 4:2:2 mode to give you an idea of the impact the latter has on text clarity. You can see it mainly impacts text on a coloured background, and where text is smaller in size. In some samples it's very hard to see any difference to be honest. For other uses like movies and games the difference is less noticeable. Movies, Blu-rays, external games consoles and external Blu-ray players are all going to operate at lower refresh rates, so there is no need to reduce the chroma to 4:2:2 anyway. You might as well run at 4:4:4 although in many cases it actually has no noticeable benefit over lower sampling. That's irrelevant here anyway. For gaming, if it's a game with lots of text you may see some similar problems with text clarity as you would in desktop use, and as shown above. Otherwise it is hard to notice a difference in many cases and the advice it to not really worry about it. With the 4K resolution, high refresh rate, 10-bit colour depth and HDR experience you are probably not going to worry about any minor drops in colour fidelity we don't think.

Does this even matter? Can you reach >98Hz? One key thing to keep in mind amongst all this talk of colour compression is the frame rate you're realistically going to be able to achieve with your system and graphics card when trying to power the screen at 4K resolution. Modern HDR capable games are really going to push your system to its limits at this resolution and with high games settings, and so actually achieving high refresh rates above 98Hz might not be easy to achieve, or may even be impossible to many people. So depending on your other hardware this whole section may be somewhat irrelevant, and to many people they can just run the screen at 98Hz maximum refresh rate and have a full 10-bit colour depth and 4:4:4 chroma sampling (uncompressed).

Detailed Response Times

144Hz Refresh Rate, OD = Normal Having settled on the 'normal' OD response time mode in our earlier measurements and visual tests we carried out a more thorough set of measurements across a wider range of pixel transitions while at the maximum 144Hz refresh rate. The average G2G figure was measured at 5.3ms now which was excellent for an IPS-type panel. This was with very low levels of overshoot that were basically unnoticeable in practice. This screen is more than capable of handling fast paced gaming thanks to its low response times, high refresh rate support and NVIDIA G-sync technology.

Gaming Comparisons We have provided a comparison of the PG27UQ against many other screens that we have tested. The overall responsiveness of the PG27UQ (5.3ms) was very good, and on par with the other top end high refresh rate IPS panels we've tested, like the Asus ROG Swift PG279Q (5.0ms) and Acer Predator XB270HU (5.5ms) for instance. This was all with very low levels of overshoot as well which was great news. These 144Hz compatible IPS screens offer slightly faster response times than 100 - 120Hz capable IPS screens like the Dell Alienware AW3418DW (6.9ms) and Asus ROG Swift PG348Q (7.8ms) for instance. The TN Film panels here like the Asus ROG Swift PG278Q (2.9ms) and certainly the PG258Q (3.4ms) could reach a little faster, although sometimes this is at the expense of some additional moderate levels of overshoot.



Additional Gaming Features Aspect Ratio Control - the screen has 3 options for hardware level aspect ratio control options, with settings for full, aspect and 1:1 pixel mapping offered. The aspect mode is really useful as it will maintain the source device aspect ratio while filling as much of the screen as possible. If you want to directly map pixels you can use the 1:1 mode as well. Preset Modes - There are a quite a few modes available in the 'GameVisual' preset mode menu. Accessed via one of the quick access OSD control buttons there are modes for various different uses as shown above. Plenty of different modes to set up and customise for your different uses. GameVisual offers six display presets, each optimized for a specific usage scenario. These include: FPS Mode: Enhanced visibility in First Person Shooter gameplay.

RTS/RPG Mode : Enhanced color and sharpness in Real-Time Strategy / Role-Playing Games.

sRGB Mode: Optimized for photos and graphics on your PC.

Racing Mode: Created for real-time racing and fast gaming experience.

Cinema Mode : Contrast and color saturation for livelier and vivid visuals during movies.

Scenery Mode: Increased brightness, contrast gradation plus color saturation tweaks for viewing photographic scenes. Note: GameVisual options are only available when using SDR mode. GamePlus - offers additional overlays to aid and enhance the games you play. As they are built into the display OSD, they can be applied to any game. A countdown timer and aiming crosshair, with options of styles and placements, are available. There’s also an overlay with alignment arrows to aid precise calibration of multi-monitor setups. ROG Light Signature - ROG Light Signature is integrated at the base of the monitor stand and features a downward firing light that casts the ROG logo onto the desktop surface. The plastic inserts can be customized to illuminate clan emblems or other personalized designs. It includes two ROG logo covers and three blank covers that you can use to create customised light projections that show your unique gaming style. ROG Light Signal - ROG Light Signal resides at the top of the stand, projecting the ROG logo onto the ceiling above. Both Light Signal and Light Signature are controlled from the OSD, with Light Signature offering three levels of illumination intensity. You can also control the angle of the projection using a small slider control on the back of the stand. ASUS Aura Sync - this technology creates immersive ambient lighting and supports synchronization with Aura-enabled components and peripherals. To achieve perfect synchronisation, simply connect ROG Swift PG27UQ to other peripherals by installing the Aura Sync software on your laptop or desktop. Enjoy the coolest and most stylish backdrop for any gaming setup, and have all lights pulsing to the beat of your favourite music or game sound effects. With an eco-system that spans over 100 devices, there’s scope to create a cohesive visual theme from the PC all the way to the desktop and beyond.

Rear ROG logo lighting - a large ROG logo on the rear of the monitor can be controlled using either the monitor OSD (with several styles of RGB color cycling) or by AURA Sync software via a USB connection to the PC. This allows colors and effects to be synchronized with a range of Aura Sync-compatible hardware.



Lag We have written an in depth article about input lag and the various measurement techniques which are used to evaluate this aspect of a display. It's important to first of all understand the different methods available and also what this lag means to you as an end-user. Input Lag vs. Display Lag vs. Signal Processing To avoid confusion with different terminology we will refer to this section of our reviews as just "lag" from now on, as there are a few different aspects to consider, and different interpretations of the term "input lag". We will consider the following points here as much as possible. The overall "display lag" is the first, that being the delay between the image being shown on the TFT display and that being shown on a CRT. This is what many people will know as input lag and originally was the measure made to explain why the image is a little behind when using a CRT. The older stopwatch based methods were the common way to measure this in the past, but through advanced studies have been shown to be quite inaccurate. As a result, more advanced tools like SMTT provide a method to measure that delay between a TFT and CRT while removing the inaccuracies of older stopwatch methods. In reality that lag / delay is caused by a combination of two things - the signal processing delay caused by the TFT electronics / scaler, and the response time of the pixels themselves. Most "input lag" measurements over the years have always been based on the overall display lag (signal processing + response time) and indeed the SMTT tool is based on this visual difference between a CRT and TFT and so measures the overall display lag. In practice the signal processing is the element which gives the feel of lag to the user, and the response time of course can impact blurring, and overall image quality in moving scenes. As people become more aware of lag as a possible issue, we are of course keen to try and understand the split between the two as much as possible to give a complete picture. The signal processing element within that is quite hard to identify without extremely high end equipment and very complicated methods. In fact the studies by Thomas Thiemann which really kicked this whole thing off were based on equipment worth >100,1000 Euro, requiring extremely high bandwidths and very complicated methods to trigger the correct behaviour and accurately measure the signal processing on its own. Other techniques which are being used since are not conducted by Thomas (he is a freelance writer) or based on this equipment or technique, and may also be subject to other errors or inaccuracies based on our conversations with him since. It's very hard as a result to produce a technique which will measure just the signal processing on its own unfortunately. Many measurement techniques are also not explained and so it is important to try and get a picture from various sources if possible to make an informed judgement about a display overall. For our tests we will continue to use the SMTT tool to measure the overall "display lag". From there we can use our oscilloscope system to measure the response time across a wide range of grey to grey (G2G) transitions as recorded in our response time tests. Since SMTT will not include the full response time within its measurements, after speaking with Thomas further about the situation we will subtract half of the average G2G response time from the total display lag. This should allow us to give a good estimation of how much of the overall lag is attributable to the signal processing element on its own. Lag Classification

To help in this section we will also introduce a broader classification system for these results to help categorise each screen as one of the following levels: Class 1) Less than 6.94ns / 1 frame lag at 144Hz - should be fine for gamers, even at high levels

Class 2) A lag of 6.94 - 13.88ms / One to two frames at 144Hz - moderate lag but should be fine for many gamers. Caution advised for serious gaming

Class 3) A lag of more than 13.88ms / more than 2 frames at 144Hz - Some noticeable lag in daily usage, not suitable for high end gaming

For the full reviews of the models compared here and the dates they were written (and when screens were approximately released to the market), please see our full reviews index. (Measurements in ms) Total Display Lag (SMTT 2) 8.14 Pixel Response Time Element 3.45 Estimated Signal Processing Lag 4.69 Lag Classification 1

Class 1 We have provided a comparison above against other models we have tested to give an indication between screens. The screens tested are split into two measurements which are based on our overall display lag tests (using SMTT) and half the average G2G response time, as measured by the oscilloscope. The response time 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. We measured the total display lag of 8.14ms. With approximately 3.45ms of that accounted for by pixel response times (based on 98Hz refresh rate as a middle ground) we had an estimated signal processing of just 4.69ms, which was next to nothing and in keeping with other G-sync screens we've tested in the past. This shouldn't represent any problem for fast paced or competitive gaming.



Movies and Video The following summarises the screens performance for videos and movie viewing: Category Display Specs / Measurements Comments Size 27" widescreen Fairly standard for desktop display today, much smaller than a TV Aspect Ratio 16:9 Well suited to most common 16:9 aspect content and input devices Resolution 3840 x 2160 Can support native 1080p content and Ultra HD content natively HDCP Yes v2.2 Suitable for encrypted content across both ports Connectivity DisplayPort 1.4

HDMI 2.0 Useful additional HDMI input for external Blu-ray players or games consoles. Capable of supporting the high resolution as well Cables DisplayPort and HDMI Both provided in the box which is good news Ergonomics Tilt, height, swivel, rotate Good range of adjustments which are smooth and easy to use. You should be able to position the screen for multiple viewing positions. Coating Light Anti-glare Provides clear, non-grainy image and avoids unwanted reflections of full glossy solutions Brightness range 24 - 532 cd/m2 (SDR)



up to 1237 cd/m2 peak brightness in HDR mode Very good adjustment range offered. Flicker free backlight operation with no PWM. In HDR mode the FALD is capable of producing very high peak brightness >1000 cd/m2 and strong HDR contrast ratios Contrast 1071:1 SDR



up to 26,650:1 SDR with FALD



up to 61,850:1 in HDR mode Strong contrast ratio for an IPS panel, helping provide good clarity in shadow detail and darker content. Improved even further if you enable the FALD, even in SDR content. The active contrast ratio will depend on how bright you make the screen overall. HDR contrast is very strong thanks to local dimming and FALD backlight along with high peak brightness capability. Preset modes Cinema Seems to be set up the same as the default Racing Mode, but might be useful to customise to a different setup for movies Response times 5.3ms G2G at 144Hz, low overshoot

8.6ms G2G at 60Hz Very good overall and more than fine for movie viewing certainly. Stick with the 'Normal' response time setting if running above 60Hz. For external devices you might want to push up to the 'Extreme' OD mode Viewing angles Very good Thanks to the IPS panel technology, suitable for viewing from a wide range of positions. Low glow panel means dark content does not show the usual pale/white glow that you get from many IPS panels which is great news Backlight bleed Very good No backlight bleed on our sample (may vary) which is good, as that can be particularly problematic on movies with black borders. Local dimming helps reduce blacks on darker content nicely Audio Headphone jack No integrated speakers, but a headphone jack available Aspect Ratio Controls 1:1, Aspect, Full Good options to account for non-native format inputs if needed PiP / PbP Not available n/a HDR support Yes, certified with: VESA DisplayHDR 1000

Ultra HD Premium See our HDR section for more information

High Dynamic Range (HDR) HDR stands for High Dynamic Range and is a technology just starting to make its way in to the desktop monitor market. It's been around in the TV market for a couple of years and is used primarily to provide a better dynamic range and contrast to the image for multimedia, movies and games - that being the difference between light and dark parts of an image. This improvement to the dynamic range is usually paired with other specific features under the banner term of "HDR" including a wider colour gamut for richer, more vivid colours and specs like a 10-bit colour depth support and a high Ultra HD resolution. Overall, an HDR Capable screen is designed to offer a more life-like images, with better contrast ratios between light and dark areas and more vivid, bright colours. You only need to go in to a high street store to observe the difference that HDR makes on TV sets, so we would encourage you to do that if you want to see first hand the improvements it makes to the image quality. HDR Standards Conformity Ultra HD Premium Spec Guidelines

Yes/no

Display Spec

At least Ultra HD Resolution 3840 x 2160 3840 x 2160 supported 10-bit colour depth processing 8-bit + FRC panel DCI-P3 colour space coverage 110.3% DCI-P3 measured Suitable HDR connectivity DisplayPort 1.4 and HDMI 2.0 at least 1000 cd/m2 peak luminance 1236 peak cd/m2 measured at least 20,000:1 active contrast ratio 61,800:1 maximum measured Backlight dimming system

(not defined in Ultra HD Premium requirements) 384-zone Full Array Local Dimming (FALD) The PG27UQ is heavily promoted for its HDR capabilities, and unlike many screens in the market this one does actually live up to the billing. It even carries official certification under the new VESA DisplayHDR 1000 standards, and the established TV Ultra HD Premium certification as well making it a "true" HDR screen. Local dimming is achieved through a 384-zone (24 x 16) Full Array Local Dimming (FALD) backlight for the best HDR dimming performance you can currently get from an LCD panel. OLED screens in the TV market can offer superior local dimming, but for LCD screens FALD is the preferred method, and the more zones, the better. This means small areas of the screen can be brightened while others are dimmed, and it gives a far better level of control compared with typical edge-lit local dimming options which have far few zones. Read our HDR article for more information about these methods to achieve local dimming necessary for HDR. Even with 384 zones you will see some blooming around small bright objects on a dark background, and that's unavoidable. Mouse cursors on dark backgrounds are an unrealistic real-world test and you can spot the blooming around them quite easily. But in real HDR content and multimedia, there were low levels of blooming apparent and it operated very well. This FALD allows the screen to offer the necessary 1000 cd/m2 peak brightness spec required for the certifications and to provide a great dynamic range contrast in practice. The Quantum Dot coating boosts the colour gamut so that there is a high DCI-P3 coverage, and the 8-bit+FRC panel supports 10-bit colour depth too. You need to enable the 'variable backlight' option in the OSD menu to operate the FALD for local dimming benefits. We will test the settings and performance of the FALD in a moment. HDR Contrast and Peak Brightness We measured the luminance and contrast performance of the screen in HDR mode in a variety of scenarios. A white box is displayed on the screen which covers 1% of the overall screen size initially. This is designed to show at several target luminance levels, starting at 100 and then changing to 400 and 1000 cd/m2 (and beyond if needed). We measure the actual luminance of that white box to see how close to the target luminance the screen actually performs at each step. When the screen reaches the maximum peak luminance possible, we also measure the black depth of the screen at a point furthest away from the white area. This can then allow us to calculate the HDR active contrast ratio, the difference between the bright white area on screen, and the dark black areas elsewhere. This 1% white screen coverage is designed to give a rough representation of how a small highlight area in HDR content might appear and work in normal multimedia. The box then increases to a larger size, covering 4, 9, 25, 49 and finally 100% of the screen area. This represents different sized areas of bright content in HDR multimedia. Again those progressively larger boxes are shown at the different luminance targets, and we measure the actual screen luminance achieved for each. Updated Measurements 6/8/18 When you enable are inputting an HDR signal either from Windows or an external device, the monitor automatically detects this and switches to HDR mode. Some options like 'brightness' are no longer available. You can however adjust the 'reference white (nits)' control yourself, and this has an impact on the brightness levels achieved by the screen. It's default is 80. PC Input, DisplayPort, Windows 10

Reference White (nits) = change to 52 White window size 100 cd/m2 target 400 cd/m2 target 1000 cd/m2 target 2000 cd/m2 target 4000 cd/m2 target Peak luminance

(cd/m2) Min black depth

(cd/m2) HDR contrast (x:1) 1% 103 435 998 1014 1014 1014 0.02 50,700 4% 101 428 1026 1236 1236 1237 0.02 61,850 9% 99 422 1005 1189 1189 1189 0.03 39,633 25% 98 417 859 853 853 853 0.05 17,060 49% 98 417 711 711 711 711 0.12 5,925 100% 98 417 654 654 654 654 n/a n/a We carried out these measurements first of all with the default 80 'white reference' setting but found that the content targets were being exceeded by quite a lot and the screen was basically too bright. Content mastered at 400 cd/m2 was being shown at around 650 cd/m2. You will probably want to lower the white reference setting to 52 in the OSD menu, and that then produced the results shown above which were nice and accurate. At all sample sizes from 1% to 100% white coverage, the targets for 100 cd/m2 and 400 cd/m2 where reached pretty accurately which was good news. Content mastered at 1000 cd/m2 was also met nicely where it was covering small areas of the screen which is great for small highlights and small bright areas on a screen. You don't really want larger areas of the screen to be too bright as it can be harsh on the eyes. When the white area reached 25% screen coverage the peak luminance was a little lower at around 859 cd/m2. This peak luminance lowered a bit more as the white area increased in size which is what you'd probably want, to avoid it being overly bright and harmful to the eyes. Actually we did observe that for about 3 seconds the screen would jump up to the full peak luminance of ~1000 cd/m2 but would then drop down and stabilise at the figures shown above. So it will temporarily show the full 1000 cd/m2 content brightness but won't stay at that level for too long. The absolute peak luminance of the screen measured was around 1236 cd/m2 which represents the upper limit of the backlight capabilities and is actually a fair amount beyond the manufacturer spec of 1000 cd/m2. This was achieved when the screen tried to show content mastered at 2000 and 4000 cd/m2 levels. With a peak luminance of around 1237 cd/m2 possible, we measured a black point on the same screen of 0.02 cd/m2. This gives rise to a maximum HDR contrast ratio of 61,850:1 which was excellent and a long way beyond the normal static contrast ratio of around 1071:1. The FALD is capable of brightening the light areas of the screen very well, particularly if the content input is designed to be 1000 cd/m2 or more, and at the same time is able to dim the dark areas to a very low black point. The results above were based on a PC connection over DisplayPort and so this is of most interest here given the PG27UQ is primarily a PC gaming screen. Your HDR games should show reliable brightness performance along with very strong HDR contrast ratios in practice. HDMI External Input

Reference White (nits) = default 80 White window size 100 cd/m2 target 400 cd/m2 target 1000 cd/m2 target 2000 cd/m2 target 4000 cd/m2 target Peak luminance

(cd/m2) Min black depth

(cd/m2) HDR contrast (x:1) 1% 110 405 659 914 1107 1107 0.02 55,350 4% 106 392 635 926 1237 1237 0.02 61,850 9% 105 388 632 918 1200 1200 0.03 40,000 25% 104 377 597 906 846 846 0.05 16,920 49% 104 385 622 540 691 691 0.12 5,758 100% 105 376 597 668 668 668 n/a n/a The above results came from our original tests published in this review before the update above. We have left them in for completeness, but these results were obtained when connecting an external device capable of HDR content over the HDMI interface. This is a simpler setup, removing all the complications with Windows, software, graphics cards etc and will give you a representation of the screens behaviour when connecting an external device like a Blu-ray player or Games Console in theory. At all sample sizes from 1% to 100% white coverage, the targets for 100 cd/m2 and 400 cd/m2 where reached quite accurately which was good news. When it comes to 1000 cd/m2 target content, the screen didn't reach the desired luminance at any of the sample sizes. For some reason the screen behaves a bit differently, perhaps because of the HDMI interface being used here. You can alter the 'reference white (nits)' setting in the OSD if you want, and by increasing that from the default 80 level up to around 168, an approximate 1000 cd/m2 figure was achieved. The backlight is certainly capable of it. That has the knock on effect though of making the 100 cd/m2 and 400 cd/m2 content brighter than it should be. It is probably best to leave the setting at the default 80, as you don't want all the darker 100 - 600 cd/m2 range content being brighter than it should be, especially if you're using the screen from up close. Content designed for 2000 cd/m2 actually produced a luminance closer to the 1000 cd/m2 peak brightness spec of the screen, where the white sample size was 1 - 25% of the screen area. So any content designed to be really bright will push the backlight capabilities to their limits. When the white sample size becomes larger at 49% of the screen or more, the luminance is lowered to around 540 - 668 cd/m2 so as not to blind you with a really large white area at a mega-high luminance. That is a good thing, as you really only want small screen areas to reach the upper peak brightness levels possible so as not to hurt your eyes. Content mastered at 4000 cd/m2 actually pushed the screen to reach it's upper limit of brightness possible from the FALD backlight. We reached 1237 cd/m2 in the best example (4% screen coverage of a white sample), which was beyond the peak brightness spec from Asus by quite a long way in fact. With a peak luminance of around 1237 cd/m2 possible we measured a black point on the same screen of 0.02 cd/m2. This gives rise to a maximum HDR contrast ratio of 61,850:1 which was excellent and a long way beyond the normal static contrast ratio of around 1071:1. FALD Speed The challenge with local dimming backlights is getting them to operate fast enough so that they can keep up with the changing screen content, particularly for PC gaming where you are viewing the screen from close up. You need a backlight that can respond nice and quickly to changes in brightness and darkness to produce an optimal HDR experience. This helps avoid trails and haloing behind moving objects and reduces the blooming affect as a result. Asus and NVIDIA have worked very hard to get the FALD backlight operating at high refresh rates and with G-sync, and have invested a lot of development time in getting the FALD to respond quickly. Three settings are available in the OSD menu to control the speed of the 'variable backlight', and this works in SDR and HDR content. There are settings for gradual, medium and fast available. We looked at the speed of the FALD backlight when we tested the Dell UP2718Q back in December 2017, which was the first desktop monitor of its kind with this kind of backlight. By using the a simple moving white circle test pattern we measured how quickly the FALD backlight brightens and then dims the backlight. We measure the change in screen luminance as the white moving circle passes in front of our photosensor.



Example graph annotated to explain what is being measured. Taken from the Dell UP2718Q Above is a measurement of the Dell UP2718Q's FALD backlight purely to explain what we are measuring and what the graph means. We have annotated the graph to make it easier to understand. We can establish how long it takes the screen to reach the peak luminance, and how long it takes the screen to return to darkness after the white circle has moved on. There is an element of pixel response times in here, but what we're interested in is the overall time it takes for the screen to reach the desired bright peak, and then drop back down to the dark point again. We tested this using an HDMI input source at 60Hz and with the OD setting at normal. Gradual Setting FALD total delay time Total Rise Time 34ms Total Fall Time 6ms It takes 34ms for the FALD backlight to carry out the change from showing dark content to the peak luminance output it will reach. It then takes the FALD backlight only 6ms to switch back to darkness after the white circle has moved away. The FALD is very quick at switching back to an 'off' state and returning from bright content back to darkness. It is a little slower reaching the peak brightness but a lot faster than we'd seen on the Dell UP2718Q which was 624ms rise time! The fast fall time back to black helps avoid pale halos and trails behind moving objects which is very important. Medium Setting FALD total delay time Total Rise Time 17.5ms Total Fall Time 6ms It takes 17.5ms for the FALD backlight to carry out the change from showing dark content to the peak luminance output it will reach. It then takes the FALD backlight only 6ms to switch back to darkness after the white circle has moved away. The FALD is now faster at changing from dark to bright on the rise time, helping to optimise the appearance of HDR content. Fast Setting FALD total delay time Total Rise Time 10.5ms Total Fall Time 6ms It takes only 10.5ms for the FALD backlight to carry out the change from showing dark content to the peak luminance output it will reach now. It then takes the FALD backlight only 6ms to switch back to darkness after the white circle has moved away. The FALD is even faster now, operating very quickly and not really adding much lag on top of the pixel response times. We expect the 'fast' setting to be preferred for fast paced gaming and it responds very quickly to content changes. If you experience any flashes or the changes are too abrupt for your content, you can drop back to one of the other settings if you wish. Using HDR Complexities

We will repeat what we said in some of our previous reviews here as it's an important consideration you need to make. We should touch on the complexities of using HDR at this stage though, especially from a PC. It's actually quite complicated to achieve an HDR output at the moment from a PC and something you should be aware of before jumping straight in to a modern HDR screen. You will need to ensure you have a compatible Operating System for a start. The latest Windows 10 versions for instance will support HDR, but from many systems you will see some odd behaviour from your monitor when it is connected. The image looks dull and washed out as a result of the OS forcing HDR on for everything. HDR content should work fine (if you can achieve it - more in a moment!) and provide a lovely experience with the high dynamic range and rich colours as intended. However on some Windows 10 versions, normal every day use looks wrong with the HDR option turned on. Windows imposes a brightness limit of 100 cd/m2 on the screen so that bright content like a Word Document or Excel file doesn't blind you with the full 1000 cd/m2 capability of the backlight. That has a direct impact on how the eye perceives the colours, reducing how vivid and rich they would normally look. It also attempts to map the common sRGB content to the wider gamut colour space of the screen causing some further issues. Sadly Windows isn't capable at the moment of turning HDR on/off when it detects HDR content, so for now it's probably a case of needing to toggle the option in the settings section (settings > display > HDR and Advanced Color > off/on). Windows does seem to behave better when using HDMI connectivity so you may have more luck connecting over that video interface, where it seems to switch correctly between SDR and HDR content and hopefully negate the need to switch HDR on and off in the Windows setting when you want to use different content. This is not any fault of the 