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Introduction

After over 2 years of hype and waiting, it was back in August 2018 that we finally saw the release of the first wave of monitors offering a '4K' resolution (Ultra HD to be specific) at a high refresh rate of 144Hz. The Asus ROG Swift PG27UQ was the first we had chance to test and offered a very high end and premium spec. Other models followed, including some which cut back on the cost by taking away the complex and expensive Full Array Local Dimming (FALD) backlight used to support HDR content on those earliest models. Perhaps one of the biggest gripes that people had with these first 4K @ 144Hz displays is that you had to sacrifice colour performance if you wanted to reach the upper end of the supported refresh rates. This was due to bandwidth limitations of even the latest DisplayPort 1.4 connection. This was not actually a major issue in practice, but put some people off considering these early offerings. If you want to game at 4K and 144Hz you shouldn't have to sacrifice colours was the argument.

This limitation was down to the bandwidth capacity of even the latest DisplayPort video connection type used, that being v1.4. There just wasn't the room to push 4K resolution, 144Hz refresh rate and full RGB colours at 10-bit colour depth for HDR content. Newer video standards like HDMI 2.1 have yet to appear as well for graphics cards and so manufacturers were left with trying to find clever ways of getting around this limitation with what was currently available. Some later 4K @ 144Hz screens allowed you to connect two DisplayPort cables to offer you twice the bandwidth capacity. This worked well to avoid colour sacrifice, but unfortunately cannot work with variable refresh rates so had it's own limitations.

We have with us now the new Asus ROG Strix XG27UQ which is one of the first displays to be released that makes use of VESA's new Display Stream Compression (DSC) technology. This, according to VESA, offers "visually lossless" compression over a single DisplayPort connection, allowing you to run the screen at 4k, 144Hz and 10-bit full RGB colour as long as you have a DSC-compatible graphics card. The screen maintains the same 3840 x 2160 resolution along with a 144Hz native refresh rate of the earlier models. Adaptive-sync is also supported for variable refresh rates from both NVIDIA G-sync and AMD FreeSync systems. Asus have also added their ELMB motion blur reduction backlight mode and there's familiar ROG features like Aura Sync RGB lighting and a range of gaming settings and features to play with. This model doesn't have the FALD HDR backlight of the PG27UQ so there's no real HDR support to speak of, but it does mean that of course it's a more affordable option.

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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"

Panel Coating

Light AG coating

Aspect Ratio

16:9 flat

Interfaces

2x DisplayPort 1.4
2x HDMI 2.0
1x Headphone output
2x USB 3.0

Resolution

3840 x 2160
Ultra HD

Pixel Pitch

0.155mm

Design colour

Charcoal bezels, enclosure arm and foot with some maroon red trim on the stand

Response Time

4ms G2G
1ms MPRT

Ergonomics

Tilt, 120mm height, swivel, rotate

Static Contrast Ratio

1000:1

Dynamic Contrast Ratio

not listed

VESA Compatible

Yes 100 x 100 mm

Brightness

350 cd/m2 typical
400 cd/m2 peak

Accessories

Power cable and brick. DisplayPort, HDMI, USB cables

Viewing Angles

178/178

Panel Technology

AU Optronics AHVA (IPS-type)

Weight

with stand: 7.5Kg

Backlight Technology

LED

Physical Dimensions (WxHxD)

633.64 x (436.5-556.5) x 269.5 mm

Colour Depth

1.07b (8-bit + FRC)

Refresh Rate

144Hz
48 - 144Hz VRR range

Special Features

Adaptive-sync for VRR from AMD FreeSync and NVIDIA G-sync systems, ELMB blur reduction, Aura Sync lighting, light signature, factory calibration

Colour Gamut

Wide gamut 90% DCI-P3 and
125% sRGB quoted

The XG27UQ offers a good range of modern connectivity with 2x DisplayPort 1.4 and 2 x HDMI 2.0 offered for video connections. These are located on the back of the screen along with a headphone output and 2x USB downstream ports. For PC connectivity the DisplayPort is the most common option, with HDMI being available then for connecting external games consoles or Blu-ray players potentially. The screen has an external power supply and comes packaged with the power cable and small power brick that 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

USB type-C

Rotate adjust

DisplayPort

VESA compliant

Component

USB 2.0 Ports

Audio connection

USB 3.0 Ports

HDCP Support

Card Reader

Integrated Speakers

Ambient Light Sensor

PiP / PbP

Human Motion Sensor

Blur Reduction Mode

Touch Screen

NVIDIA G-Sync (native)

Factory calibration

AMD FreeSync

Hardware calibration

G-sync Compatible Certified

Uniformity correction

Meaningful HDR



Design and Ergonomics


Above: front view of the screen, click for larger versions

The XG27UQ comes in a mostly black design with matte plastics used for the bezel, rear enclosure and arm. The foot of the stand is a 3-pronged black aluminium. There is also a small maroon red plastic trim section at the bottom of the stand as you can see from the pictures. There is a traditional plastic bezel around all 4 sides on this screen. It measures 16mm along the sides, 19mm along the top and 21mm along the bottom edge. There is also a small 1mm black panel border before the image starts.

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

The back of the screen is encased in a matte black plastic and there are some textured and patterned sections on the right as you can see. The ROG logo lights up using the Asus AURA sync lighting system. The OSD control buttons and joystick are located on the left hand edge at the back (when viewed from behind). There is also a cable tidy hole in the bottom of the stand as shown.


Above: side view of the screen, click for larger version

The screen has a fairly deep profile, especially the fairly chunky stand. It actually has a small external power supply brick so that hasn't even been built in to the screen here. The stand does provide a very sturdy and stable support for the screen though.

The stand offers a full range of ergonomic adjustments. Tilt provides a decent range of adjustment and is smooth and reasonably easy to operate, perhaps a little stiff. Height is smooth and easy, and provides a wide adjustment range as well. At the lowest setting the bottom edge of the screen is 50mm from the desk. At maximum extension it's 170mm which provides a decent 120mm adjustment range for the height adjustment as advertised. Side to side swivel and even the rotation function are smooth and easy to position. The screen remains very stable when you are moving it around thanks to the solid and sturdy 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

Easy

Rotate

Yes

Smooth

Easy

Overall

Very good range of adjustments and all pretty easy and smooth to move. Screen remains very stable and the stand is strong and heavy.

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


Above: view of interface and connection options

The connections are available on the back of the screen and shown above. From left to right there are power input, headphone jack, 2x HDMI 2.0, 2x DisplayPort 1.4, 1x USB upstream and 2x USB 3.0 downstream.

As well as the Aura Sync lighting that is on the back of the screen, the XG27UQ features Asus' "Light in motion" signature light on the bottom of the stand. This projects a red light on to your desk and can be customised with different blanking plates (or turned off in the OSD menu).

The OSD is controlled primarily through a joystick located on the back right hand edge (if looking at the screen from the front). There are also 3 pressable buttons available. One gives you quick access to the 'GamePlus' menu with options for things like the crosshair and FPS counter available. Another gives you quick access to the 'GameVisual' preset mode menu. The main menu is available via the joystick and split in to 7 sections. Navigation is intuitive and easy, although slightly laggy. There's plenty of options to play around with and configure though.



Power Consumption

State and Brightness Setting

Manufacturer Spec (W)

Measured Power Usage (W)

Default (50%)

<90.0

43.1

Calibrated (11%)

-

27.5

Maximum Brightness (100%)

-

55.3

Minimum Brightness (0%)

-

23.4

Standby

<0.5

0.5

We have plotted these results below compared with other screens we have tested. The consumption (comparing the calibrated states) is comparable to most of the other 27" sized screens we've tested as you might expect. The larger screens tend to have additional power usage as does the 27" Asus ROG Swift PG27UQ with it's FALD backlight.



Panel and Backlighting

Panel

Backlight

Panel Manufacturer

AU Optronics

Backlighting Type

LED

Panel Technology

AHVA (IPS-type)

Colour space

Wide gamut

Panel Part

M270QAN02.3

sRGB coverage spec

125%

Screen Coating

Light anti-glare

DCI-P3 spec

90%

Colour Palette

1.07 billion

Adobe RGB coverage spec

not listed

Colour depth

8-bit + FRC

Flicker free verified


(with low amplitude oscillation at ~2350Hz)

Backlight dimming at setting of:

100                                                                         50                                                                         0

Above: backlight operation showing no PWM but a very low amplitude oscillation at ~2350Hz.

The backlight does not use any traditional PWM dimming method thankfully and instead uses a Direct Current (DC) technology. There is a very low amplitude (i.e. very minimal variation in brightness) oscillation for settings below 100% that we include above for completeness. This also operates at a very high frequency of ~2350Hz and so should not be visible at all or present any problems in practice.



Brightness and Contrast

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

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

OSD Brightness

Luminance
(cd/m2)

Black Point (cd/m2)

Contrast Ratio
( x:1)

100

491.20

0.43

1142

90

457.83

0.43

1065

80

427.69

0.37

1156

70

397.65

0.35

1136

60

367.37

0.32

1148

50

337.03

0.29

1162

40

280.20

0.24

1168

30

226.24

0.20

1131

20

172.35

0.15

1149

10

118.57

0.10

1186

0

64.48

0.06

1075

 

Total Luminance Adjustment Range (cd/m2)

426.72

Brightness OSD setting controls backlight

Total Black Point Adjustment Range (cd/m2)

0.37

Average Static Contrast Ratio

1138:1

PWM Free

Recommended OSD setting for 120 cd/m2

10

At the full brightness setting in the OSD the maximum luminance reached a very high 491 cd/m2 which was a lot higher even than the 400 cd/m2 max brightness spec from the manufacturer. There was a decent 427 cd/m2 adjustment range in total, so at the minimum setting you could reach down to a luminance of 64 cd/m2. This was decent enough at the lower end and affords you a low luminance option for working in darkened room conditions with low ambient light. A setting of 10 in the OSD menu is needed to return you a luminance as close to 120 cd/m2 as possible at default settings. Backlight dimming is controlled without the need for PWM as well which is excellent news.

       

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. There is a steeper adjustment curve for settings of 50 and below as you can see.

The average contrast ratio of the screen was measured at 1138:1 out of the box which was good for an IPS-type panel. It remained pretty stable across the brightness adjustment range as you can see above.

 


Testing Methodology

 

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

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

Targets for these tests are as follows:

  • CIE Diagram - confirms the colour space covered by the monitors backlighting in a 2D view, with the black triangle representing the displays gamut, and other reference colour spaces shown for comparison. Usually shown as a comparison against the common sRGB space

  • Colour space coverage volumes - we also measure using a piece of software called ChromaPure the colour space (gamut) volumes produced by the backlight in comparison to the sRGB, DCI-P3 and Rec.2020 colour spaces. sRGB is the most commonly used colour space so it is important to have a decent coverage from the screen here. If the colour space is >100% sRGB then the screen can produce a wider colour gamut, often reaching further in to the wider gamut DCI-P3 (commonly used for HDR) and Rec.2020 reference spaces.

  • Gamma - we aim for 2.2 which is the default for computer monitors

  • Colour temperature / white point - we aim for 6500k which is the temperature of daylight

  • Luminance - we aim for 120 cd/m2, which is the recommended luminance for LCD monitors in normal lighting conditions

  • Black depth - we aim for as low as possible to maximise shadow detail and to offer us the best contrast ratio

  • Contrast ratio (static) - we aim for as high as possible. Any dynamic contrast ratio controls are turned off here if present

  • dE average / maximum - we aim for as low as possible. If DeltaE >3, the color displayed is significantly different from the theoretical one, meaning that the difference will be perceptible to the viewer. If DeltaE <2, LaCie considers the calibration a success; there remains a slight difference, but it is barely undetectable. If DeltaE < 1, the color fidelity is excellent.



Default Performance and Setup

The screen does come with a factory calibration and a report is included in the box. A copy of the report from our sample is included below. It's not 100% clear for which mode this applies, as in one place it mentions it is for "SDR mode / Racing mode" which is one of the wide gamut modes, but then in another it states that the colour accuracy is relative to sRGB - which is a problem if you're working with wide colour gamut output. We believe this factory calibration is more likely to apply to the sRGB preset mode as per our measurements below, but either way we will measure both the default Racing mode, and the sRGB emulation mode:


 

Default settings of the screen were as follows:

Asus ROG Strix XG27UQ
Default Settings

 

 


Monitor OSD Settings

 

GameVisual preset mode

Racing Mode

Brightness

50

Contrast

80

Color Temp

User Mode

Gamma

2.2

RGB

100, 100, 100

Luminance Measurements

 

luminance (cd/m2)

343

Black Point (cd/m2)

0.30

Contrast Ratio

1162:1

Colour Space Measurements

 

sRGB coverage

128.8%

DCI-P3 coverage

95.0%

Rec.2020 coverage

68.1%


 

Initially out of the box the screen was set in the 'Racing mode' preset, as well as the 'user mode' colour temp mode and with RGB levels all at 100. The display was set with a 50% brightness which was actually very bright despite being a fairly modest setting, and uncomfortable to use for long periods. You will want to turn that down as with most screens. The colour temp felt a bit too warm out of the box but you could tell that the screen was using a wide gamut backlight, as the colours looks vivid and bright and more saturated than a normal sRGB screen. 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) extends a considerable way beyond the sRGB reference space (orange triangle) in most shades. We measured using ChromaPure software a 128.8% sRGB gamut volume coverage which corresponds to 95.0% of the DCI-P3 reference and 68.1% of the Rec.2020 reference. This was a little beyond the 90% DCI-P3 spec even. There is also an sRGB emulation mode available via the GameVisual preset mode menu which we will test in a moment.

Many people will prefer the wide gamut mode though for gaming and multimedia, which are clearly the target markets for this screen. The sRGB mode might be useful, despite being very restrictive, if you are doing any colour critical work and specifically want to work with the smaller colour space.

Key Quick Information Box

  • Default mode operates with full native gamut covering 95% DCI-P3

  • Decent gamma setup but colour temp is too warm

  • Decent contrast ratio for an IPS panel

  • sRGB emulation mode available and provides reliable setup, but is inflexible for user control unfortunately

Default gamma was recorded at 2.2 average with a minor 2% deviance from the target which was great news. In the default 'user mode' colour temp mode we measured a white point of 5846k which was 10% too warm. There are options to control the RGB channels which should help correct this easily enough.

Luminance at the default 50% brightness level was recorded at 343 cd/m2 which is a far too high for prolonged general use, you will need to turn that down. The black depth was 0.30 cd/m2 at this default brightness setting, giving us a 1162:1 contrast ratio which was decent for an IPS-type panel. Colour accuracy measurements should be ignored here really as they are comparing the produced wider gamut display colours against an sRGB reference which will always lead to errors. There was no sign of any colour banding when testing gradients which was good news and gradients looks smooth with only minor gradation visible.

 


sRGB Emulation

Asus ROG Strix XG27UQ
sRGB Emulation mode

 


Monitor OSD Settings

 

GameVisual preset mode

sRGB

Brightness

n/a

Contrast

n/a

Color Temp

n/a

Gamma

n/a

RGB

n/a

Luminance Measurements

 

luminance (cd/m2)

189

Black Point (cd/m2)

0.18

Contrast Ratio

1035:1

Colour Space Measurements

 

sRGB coverage

96.4%

DCI-P3 coverage

71.1%

Rec.2020 coverage

51.0%

Switching to this mode produced a noticeable change in the colour gamut of the screen, with the vividness and saturation of the colours reduced. The colour gamut was reduced now to a 96.4% sRGB coverage which was decent. We also maintained a very accurate gamma of 2.2 (0% deviance) and white point had also been improved nicely to 6350k, being only 2% too warm now. The colour accuracy was also very good with a dE average of 2.0. The only problem with this mode is that most of the OSD controls are now locked, including importantly the brightness control. That means that you are limited to only the factory set 189 cd/m2 which is fairly decent for day to day use but leaves you with no flexibility to adjust it to your ambient lighting or preference. We still really dislike sRGB emulation modes that restrict access to basic settings like the brightness control.



Optimal Settings Pre-Calibration

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

Asus ROG Strix XG27UQ
Optimal Settings Pre-Calibration

 


Monitor OSD Settings

 

GameVisual preset mode

User Mode

Brightness

11

Contrast

80

Color Temp

User Mode

Gamma

2.2

RGB

80, 98, 100

Luminance Measurements

 

luminance (cd/m2)

120

Black Point (cd/m2)

0.11

Contrast Ratio

1081:1

Colour Space Measurements

 

sRGB coverage

128.8%

DCI-P3 coverage

95.0%

Rec.2020 coverage

68.1%

For this section we switched to the 'User mode' GameVisual preset, and then also the 'user mode' colour temperature setting which would allow us access to the RGB controls and therefore the ability to correct the white point. We stuck with Gamma 2.2, while then adjusting the RGB channels as shown. This has helped correct the white point to 6500k which corrected the too warm looking image, and reduced the brightness to a much more comfortable level. Further calibration and profiling below will help improve things even further.

 


Calibration

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

Asus ROG Strix XG27UQ
Calibrated Settings

 


Monitor OSD Settings

 

GameVisual preset mode

User Mode

Brightness

11

Contrast

80

Color Temp

User Mode

Gamma

2.2

RGB

80, 98, 100

Luminance Measurements

 

luminance (cd/m2)

120

Black Point (cd/m2)

0.11

Contrast Ratio

1080:1

Colour Space Measurements

 

sRGB coverage

128.8%

DCI-P3 coverage

95.0%

Rec.2020 coverage

68.1%

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

The default gamma curve was already very good out of the box and only 2% out from a 2.2 average, and we improved this slightly further through the screen profiling, now leaving only a minor 1% deviance. The white point was also now improved to 6435k which was great news, having reduced the red channel and made the image a bit cooler than out of the box. The brightness control adjustment had reduced the luminance to a comfortable level now and the contrast ratio remained good for an IPS-type panel at 1080:1. Colour accuracy of the resulting profile was very good, with dE average of 0.6 and maximum of 1.1. LaCie would consider colour fidelity to be very good overall. Gradients remained mostly smooth with no banding introduced thankfully.

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.



Setup 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.


Default setup of the screen out of the box was reasonable with a good gamma curve and decent IPS contrast ratio. The white point was too warm, but that's easy enough to adjust through some basic OSD changes. The screen operates with a full 95% DCI-P3 gamut out of the box giving bright and vivid colours for multimedia and gaming. There is an sRGB emulation mode available but it's inflexible in terms of user adjustments unfortunately. Overall the setup was decent enough for a gaming screen although many other IPS panels showed a better white point setup out of the box, so this area could have been a bit better. Contrast ratio was strong for an IPS panel which was pleasing.
 

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Viewing Angles


Above: Viewing angles shown from front and side, and  from above and below. Click for larger version

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 from the sides. Click for larger version

On a black image there is a characteristic pale glow introduced to the image when viewed from a wide angle, commonly referred to as "IPS glow". This type of glow is common on most modern IPS-type panels and can be distracting to some users. If you view dark content from a normal head-on viewing position, you may see this glow as your eyes look towards the edges of the screen. The level of glow on this panel was more than on the PG27UQ which featured a rare "low-glow" IPS panel.

This type of glow is common on most modern IPS-type panels and can be distracting to some users. If you view dark content from a normal head-on viewing position, you may see this glow as your eyes look towards the edges of the screen depending on your viewing position. It will also be more noticeable in darker ambient light conditions and if you're viewing a lot of dark content. Some people may find this problematic if they are playing a lot of darker games or watching darker movies. In normal day to day uses you couldn't really notice this unless you were viewing darker content. If you move your viewing position back, which is probably likely for movies and games keep in mind, the effect reduces as you do not have such an extreme angle from your eye position to the screen edges.



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

Luminance uniformity of the screen was only moderate on our sample, with 57% of the screen within a 10% deviance of the centrally calibrated area. The sides were a bit darker with the left hand edge showing the most significant variation, dropping down by 24% in the most extreme example. 


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. The bottom corners of the screen seemed to show a bit more leakage and clouding than the upper areas. This was not really an issue in normal use though.

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 XG27UQ 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. It does make life a bit more complicated than if you just ran at a native resolution, which is where the more common 2560 x 1440 res fits in to the 27" display space.

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 reasonable as well, offering an accurate gamma curve and decent contrast ratio for an IPS panel. The white point is a bit too warm but that might actually be preferred for office uses to help reduce the blue light output a bit. If not, you can correct this easily enough through the OSD menu. There is support for both the native DCI-P3 colour space (default mode) and an emulated sRGB colour space if you need it. There is a pretty low dE for great colour accuracy in the sRGB mode thanks to the very good factory calibration although the brightness control is locked so although it's not too bright anyway, it's a bit inflexible. Those wanting to work with wide gamut content for multimedia and HDR can achieve good coverage of the DCI-P3 colour space as well.

The brightness range of the screen was wide with the ability to offer a luminance between 491 and 49 cd/m2. This should be dark enough for most people who want to use the screen in lower ambient light conditions, including darkened rooms. A setting of 10 in the OSD brightness control should return you a luminance close to 120 cd/m2 out of the box. 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.



Spectral distribution graph showing calibrated mode at 6500k


Spectral distribution graph showing Blue Light filter level 4

There are some blue light filter settings available in the OSD menu with settings from 1 - 4. Each one gets slightly warmer than the last, with the maximum setting of 4 delivering a warmer white point of around 5004k and reducing the blue spectral peak a bit as shown above.

There are 2x USB ports provided on this screen, located on the back so they aren't particularly easy access. There are no other extras like ambient light sensors, motion sensors or card readers on this screen which are sometimes useful for office-type uses. There is a decent range of ergonomic adjustments from the stand with tilt, height, swivel and rotate offered with easy adjustments and a stable and solid stand provided. There is also VESA 100mm mounting capabilities for those who want to mount the screen instead.


 
Responsiveness and Gaming

Panel Manufacturer and Technology

AU Optronics AHVA (IPS-type)

Panel Part

M270QAN02.3

Quoted G2G Response Time

4ms G2G

Quoted MPRT Response Time

1ms MPRT

Overdrive Used

Variable Overdrive supported

Overdrive Control Available Via OSD Setting

OD

Overdrive OSD Settings

0, 1, 2, 3, 4, 5

Maximum Refresh Rate

144Hz DisplayPort native
60Hz over HDMI at native resolution

Variable Refresh Rate technology

AMD FreeSync support via DisplayPort adaptive-sync

NVIDIA G-sync support

Certified G-sync Compatible
(but application in process)

HDMI-VRR for consoles

Variable Refresh Rate Range

48 - 144Hz (DisplayPort)
48 - 60Hz (HDMI 4K native res)
48 - 144Hz (HDMI 1080p)

Motion Blur Reduction Backlight

Available - ELMB Mode

Blur reduction available also when using
G-sync/FreeSync VRR

The screen uses overdrive technology to boost pixel transitions across grey to grey changes as with nearly all modern displays. The part being used is an AU Optronics M270QAN02.3 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


AMD GeForce Graphics Cards:
Amazon USA  | Amazon UK  |  Overclockers UK  |  Amazon GER  | Amazon CAN

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You will need to keep in mind that the XG27UQ is a very top-end display in terms of refresh rate and resolution, 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. It's also important that it features DSC support if you intend to make use of that display feature here, and that is only supported on the very latest generation of cards. 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. At 27" 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. You really need to use 150% scaling to make text comfortable which leaves you with the same desktop real-estate as a 2560 x 1440 panel, albeit with a higher pixel density and therefore a boost in sharpness.

This can be useful for highly detailed design, photo and CAD/CAM work to some people. 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 native 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. Keep in mind that a 4K screen has 225% the pixels that a 2560 x 1440 display has, so that is a massive extra drain on your graphics card and system resources. You might want to consider whether you would be better off with a lower 1440p and instead pushing your frame rate and game settings up higher.

 


Display Stream Compression

Unlike first generation 4K @ 144Hz screens, the XG27UQ is one of the first available to utilise VESA's 'Display Stream Compression' (DSC) technology. Early 4K @ 144Hz displays without DSC relied on two different methods to support the full resolution and refresh rate. Models like the Asus ROG Swift PG27UQ (one of the first to market) required a drop in colour capability to power the higher resolutions. Up to 98Hz you could run at full 10-bit colour depth and 4K resolution. Above that and up to 120Hz you had to drop to 8-bit colour depth, which to many looks no different in practice anyway - especially when you consider not every game even supports 10-bit in the first place. So in reality those early screens were perfectly fine up to 120Hz in most cases. To reach the full 144Hz refresh rate you did however have to use a colour compression option called 'chroma sub-sampling' which does negatively impact the image quality. It's not really very noticeable in games and multimedia, but certainly more noticeable in desktop use where fonts can look blurred and show colour fringing. This was seen as a  negative for those early 4K @ 144Hz displays and put some people off. You can read our review of the PG27UQ which talks a lot more about chroma sub-sampling and the colour sacrifices needed for the higher refresh rates on those first generation displays.

To get around this limitation and allow 4K @ 144Hz to be used without colour sacrifice another option was later introduced on other displays. Models like the Acer Nitro XV273K used a dual-DisplayPort method instead, allowing you to connect two cables from your graphics card to the screen and double the bandwidth capability. This allowed 4K @ 144Hz and with 10-bit colour depth (and no chroma sub-sampling needed) but unfortunately means that you could not use variable refresh rates (G-sync/FreeSync) which was again another problem.

The XG27UQ provides another answer to the problem in the form of DSC (Display Stream Compression). This is a VESA standard that allows compression of the image in a reported "visually lossless" way. This negates the need for colour compression from reduced chroma or any other means, and has been added to the display's DisplayPort 1.4 connection. VESA have a whitepaper on DSC if you want to know a bit more about it.



Important note: Graphics Card Support for DSC

You need to keep in mind that only very modern graphics cards support DSC. Asus' website states: "To enable 4K resolution at 144 Hz with DSC, an NVIDIA GeForce RTX 20 series, AMD Radeon™ RX 5700 or higher graphics card is required. For additional information about enabling DSC, contact your graphics card manufacturer." If you have an older graphics card then you can of course still use the screen, but you will need to use colour compression of some sort as explained above, and in the same way as the PG27UQ. i.e. drop to 8-bit colour for up to 120Hz, and use chroma sub-sampling (4:2:2) for the full 144Hz. See our section on chroma sub-sampling in the PG27UQ review for more detailed information about the real-World impact of this method, it isn't as bad as some would have you believe.

 

up to 98Hz

120Hz

144Hz

Graphics card supporting DSC

10-bit with full RGB. No need to use DSC

10-bit with full RGB with DSC being used

Non-DSC card

10-bit with full RGB supported

Drop to 8-bit colour depth, but stick with full RGB

Need to drop to 4:2:2 chroma sub-sampling

 

Update 24/4/20 - we have now managed to complete our testing using a modern NVIDIA RTX 2070 Super graphics card, that supports DSC. There was nothing specific to enable from the drivers or software, we were now just able to select 3840 x 2160 resolution and run at 144Hz, 10-bit colour depth and full RGB straight away. We were pleased that there was no visual loss to our eyes and in our range of tests which was excellent. You can certainly see chroma sub-sampling when you use that old method especially in desktop applications, but that was not necessary now that DSC was being used. We saw now additional lag either when using this and no noticeable side-effects. This seemed to work very nicely to allow you to squeeze more out of the bandwidth of DisplayPort 1.4,

 


Response Times and Refresh Rate

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

  1. Performance at 60Hz - this is important if you want to use an external games console (or other device like a Blu-ray player etc) which typically run at 60Hz. Response time performance may well be different than at the higher refresh rates supported, and you may need a different overdrive setting for optimal experience.
     

  2. Performance during VRR (Variable Refresh Rate) - bearing in mind that the refresh rate will fluctuate anywhere from 1Hz up to the maximum supported by the screen (e.g. 1 - 144Hz on a 144Hz display). It's important to understand if the response times and overshoot will vary as the refresh rate changes. There may be a need to switch between different overdrive settings in some cases, depending on your usually attained refresh rate output and graphics card capability. This can sometimes become fiddly if your refresh rates fluctuate a lot, especially between different games, so it's always easier if you can leave a display on a single overdrive setting which is suited to the whole range. Some screens also feature "variable overdrive" which helps control the response times and overshoot depending on the active refresh rate. This is particularly apparent with traditional G-sync module screens.
     

  3. Performance at fixed refresh rates including maximum - this is important for those who have a powerful enough system to consistently output a frame rate to meet the max refresh rate capability of the screen. They may want to run at max refresh rate without VRR active, or even is VRR is active they may know they will be consistently at the upper end of the range. Many gaming screens show their optimal response time performance at the maximum refresh rate. Knowing the performance at high fixed refresh rates may also be applicable if you want to use any added blur reduction backlight which typically operate at a fixed refresh rate.
     

  4. Whether the response times can keep up with the frame rate - you will also want to consider whether the response times of the panel can consistently keep up with the frame rate. For instance a 144Hz screen sends a new frame to the display every 6.94ms, so the pixel response times need to ideally be consistently and reliably under this threshold. If they are too slow, it can lead to added blurring in practice and sometimes make the higher refresh rates unusable in real life. We consider this in our analysis.
     

We carried out some initial response time measurements and visual tests in each of the overdrive settings, and at a range of refresh rates. The overdrive control is available in the OSD menu via the 'OD' option. There are 6 levels available - 0 (off), 1, 2, 3, 4 and 5.

Key Quick Information Box

  • Good overall motion clarity thanks to 144Hz refresh rate

  • 4 @ 144Hz supported without colour sacrifice (i.e. full RGB and 10-bit) as long as you have a DSC-capable graphics card

  • Like most adaptive-sync screens there is no variable overdrive

  • OD setting needs to be considered relative to your active refresh rate

  • Response times not quite fast enough at the top end to keep up with frame rates


60Hz Refresh Rate



We are going to start with 60Hz and work our way up in the refresh rates. It was fairly easy to see in motion tests how these modes performed. We've just included the measurements from the modes in the middle where we are trying to find the best response times, but without too much overshoot. As you increased from mode 2 (where there was no overshoot at all), to mode 3 there was a minor improvement in motion clarity but it was very slight. Response times improved a little from 9.1ms average to 8.6ms. There were some moderate levels of overshoot starting to creep in, although in practice there was nothing too distracting. If you push beyond that to level 4, the overshoot becomes a lot more noticeable and you get some obvious pale halos and artefacts around moving objects. We would suggest sticking with level 3 for 60Hz inputs. This was adequate for 60Hz in terms of response times, nothing special but decent enough.

Increasing Refresh Rate

We increased first of all to 98Hz which is the maximum refresh rate you can run at with a traditional older graphics card (without DSC capabilities) while still maintaining 10-bit colour depth and full RGB chroma. You can see in this mode that level 3 OD showed less overshoot now than at 60Hz, eliminating it all at this increased refresh rate. The reason for this though was that like most adaptive-sync screens we've tested in the past, the overdrive impulse is turned down as the refresh rate increases. This is counter-intuitive really as you would normally expect the overdrive to be turned up to help accommodate the increasing frame rates. Here, it's being turned down and so response times at level 3 drop from 8.6ms at 60Hz, down to 9.4ms at 98Hz. This does eliminate the overshoot at least. At this higher 98Hz refresh rate you are better bumping the OD setting up to level 4 though, and response times are then reduced nicely down to 7.4ms along with a noticeable improvement in motion clarity in practical tests. There is a small level of overshoot starting to appear again but nothing that's really noticeable in practice.

We increased up to 120Hz for the next tests. With a DSC capable graphics card you can run this without needing to drop to 8-bit colour depth which is a welcome update compared to the earlier PG27UQ display. If your graphics card doesn't support DSC you should drop to 8-bit colour depth here, but you can still stick with full RGB chroma. Level 4 OD still provides a marked improvement over level 3 and response times remain on average the same as they were at 98Hz. There is a drop in the overshoot level again which is good news.

This same pattern is seen at the maximum 144Hz where the response times are again the same at 7.4ms, but overshoot has now been completely eliminated. This is only a small sample of measurements here so it looks like the overdrive impulse is being turned down slightly as the refresh rate increases. There's no improvement to response times to help accommodate the higher refresh rates but overshoot is at least eliminated.

 


Variable Refresh Rates (VRR)

Maximum Refresh Rate

144Hz DisplayPort native
60Hz over HDMI at native resolution

Variable Refresh Rate technology

AMD FreeSync support via DisplayPort adaptive-sync

NVIDIA G-sync support

Certified G-sync Compatible
(but application in process)

HDMI-VRR for consoles

Variable Refresh Rate Range

48 - 144Hz (DisplayPort)
48 - 60Hz (HDMI 4K native res)
48 - 144Hz (HDMI 1080p)

  

The screen supports VESA Adaptive-sync and so can support variable refresh rates from both AMD FreeSync and NVIDIA G-sync systems. The VRR range supported is between 48 and 144Hz.

We'd like to include mention here of something we didn't like within the Asus marketing for this screen - and something that we've seen from other manufacturers too of late that we'd rather was stopped. You can see above the section from the XG27UQ spec page which says that the screen is "NVIDIA G-sync Compatible Ready". Read further on and you will see that this is pending certification and is currently going through the "application process". The 'G-sync Compatible' branding is reserved for screens that have passed a series of NVIDIA tests and checks for VRR and been formally certified. It's a better level of VRR experience and capability that just the baseline G-sync support that all adaptive-sync screens will now offer. This screen has not yet been awarded that certification, and regardless of whether or not Asus are going through the application at the moment, or whether or not it might get the certification soon, we don't like this branding being used in this way personally until it has. By all means talk about the screen supporting NVIDIA G-sync, which it does, but don't mislead consumers by suggesting that it has been certified as 'G-sync Compatible' when it hasn't yet, or start inventing new terms like calling it "ready" for G-Sync Compatible certification please. The OSD menu even lists "G-sync Compatible" in the section for adaptive-sync, so what happens if Asus don't get that certification after all?


The screen also supports HDMI-VRR which will allow support for variable refresh rates from compatible games consoles. If you connect a PC via HDMI then at the native 4K resolution the VRR range supported is reported as 48 - 60Hz only. This is increased to 48 - 144Hz if you drop down to a 1080p input.

The support for G-sync and FreeSync will be very useful given the significant system demands of running a screen at such a high 3840 x 2160 resolution and up to 144Hz refresh rate. It was of course very good to see it included here. You might also want to read our newly updated article about Variable Refresh Rates here for more information.

 


Detailed Response Times

To achieve the optimal performance from the XG27UQ you do need to take in to account your active refresh rate and adjust your OD control accordingly. This is the same as most adaptive-sync screens where 'variable overdrive' is not featured and response times and overshoot levels do not always behave as you might want with changing refresh rates. Variable overdrive is a feature of a hardware G-sync module, and one of the reasons why many Native G-sync screens offer superior response time behaviour and simpler configuration. Read more about that in our article here.

You need to consider your active refresh rate in game to select the optimal OD setting. You can't just stick with a single mode like some other gaming screens (particularly Native G-sync models). If you are playing at the lower refresh rate end of around 60 - 85Hz commonly, then level 3 OD will be optimal, avoiding the high levels of overshoot you get if you go up to level 4 OD. For higher refresh rates of 85Hz+ you can move up to the level 4 OD where overshoot is low enough to not be a problem, and reduces further as the refresh rate goes higher. Level 5 OD is never usable at any refresh rate as the overshoot is too high and pale halos in practice are far too noticeable.

The higher refresh rates supported by the screen really do help improve motion clarity and reduce perceived  blur, making the screen far better for gaming than 60Hz-only models. There is a noticeable improvement in motion clarity as you go from 60Hz > 144Hz which was great, as a result of both the improved response times but mostly because of the additional refresh rate/frame rate.

Recommended Settings

Optimal Refresh Rate 

144Hz

Optimal Overdrive Setting (for above) 

Level 4

Optimal Overdrive Setting for 60Hz 

Level 3

Optimal Overdrive Setting for VRR 

Level 3 (lower range 60 - 85Hz)
Level 4 (upper range 85Hz +)


     Detailed Measurements at 144Hz, Overdrive = Level 4

We carried out some further response time measurements at 144Hz which is the maximum refresh rate of the screen. We measured an average 6.8ms G2G response time in this mode which was good although not as fast as we might have expected from a modern IPS gaming panel to be honest. We had seen the PG27UQ reach down to 5.3ms G2G at 144Hz with more consistent performance, although that screen does feature a Native hardware G-sync module as we've discussed earlier. Some transitions reached down as low as 3.4ms which was great, but the problem was that some other transitions were much slower up to 11.1ms in the worst case. At this max refresh rate the overshoot is at a low level and doesn't cause any issues in practice which was great news.

 


Refresh Rate Compliance

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

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

For the XG27UQ you can see that the measured response times remain fairly flat across all the refresh rates, but you do need to change the OD setting to achieve this and get the optimal performance as we've already discussed. By the time you reach the upper end of the supported refresh rates you can see that the average G2G response times are starting to converge on the refresh rate threshold line. In fact if you look at our detailed response time measurements at 144Hz you can see that in reality only 56.7% of measured transitions fall within the threshold, or 70% if we allow a small 1ms leeway wiggle room.

Before you get too worried about this though, in practice the performance was still very good. There was a little bit of added smearing on moving content because the response times weren't fast enough to always keep up with the frame rate, but with a high 144Hz refresh rate the motion clarity was still very good. Had the response times been a bit faster and more consistent (without overshoot still), then the motion clarity could have been improved slightly further but it was still decent here. The PG27UQ for instance which has variable overdrive thanks to the Native hardware G-sync module and achieves response tiems which are more within the threshold, so looks slightly sharper in practice as a result.

    


Motion Blur Reduction (ELMB mode)

The strobing blur reduction backlight option is available via the 'ELMB' (Extreme Low Motion Blur ) setting which is available only once you've turned adaptive-sync off in the OSD. You would only want to enable ELMB mode for gaming as it introduces a deliberate strobing flicker to the screen which is not what you want for day to day office-type uses. For gaming these blur reduction backlights can normally help improve the perceived motion clarity and make gaming even better, although you will see from our testing that this option on the XG27UQ is not useable at all sadly.


Example strobing at 144Hz, horizontal scale = 5ms

This ELMB mode is only available at fixed refresh rates of 100, 120 and 144Hz (not at 60Hz). Like nearly all other blur reduction modes except a few Asus 'ELMB-sync' models such as the Asus TUF Gaming VG279QM tested recently, this feature cannot be used at the same time as FreeSync/G-sync variable refresh rates, it's one or the other. The strobing is in sync with the refresh rate of the display, so at 144Hz the screens backlight is turned on/off again every 6.94ms. With ELMB enabled there are a couple of important settings that are unfortunately locked in the OSD. Firstly brightness is locked which means you can't customise the brightness of the display, you are locked at a luminance around 196 cd/m2 (measured). Secondly, and most important of all the OD (overdrive) control is locked and not accessible. This seems to have been set at the maximum level 5 OD as well, which means horrible amounts of overshoot in practice which you cannot get rid of, particularly if you are running at the lower supported refresh rates. More on that in a moment, but this alone makes ELMB mode unusable on this display.


Maximum Blur Reduction Brightness - Display Comparison

We include this section here only for completeness. For ease of reference we have also provided a comparison table below of all the blur reduction enabled displays we've tested, showing their maximum luminance before blur reduction is turned on (normal mode) and their maximum luminance with the feature enabled. This will give you an idea of the maximum brightness you can expect from each model when using their blur reduction feature, if that is important to you. A lot of people want a brighter display for gaming and sometimes the relatively low maximum luminance from blur reduction modes is a limitation.

These comparisons are with the refresh rate as high as is available for the blur reduction feature to function. For most this is at 100 - 144Hz. You can often achieve a slightly brighter display if you use the feature at compatible lower refresh rates since the strobes are less frequent, but it's not a significant amount. That can also introduce more visible flicker in some situations.

Model

Refresh Rate

Max Normal Luminance
Blur Reduction Off
(cd/m2)

Max Luminance Blur Reduction On
(cd/m2)

Acer Nitro XF252Q

240Hz

413

226

Acer Nitro XV273K

144Hz

503

195

Acer Nitro XV273 X

240Hz

462

210

Acer Predator XB270HU*

100Hz*

327

111

Acer Predator Z35

120Hz

359

111

AOC AGON AG273QZ

240Hz

435

431

Asus ROG Strix XG27UQ

144z

491

196

Asus ROG Strix XG35VQ

100Hz

376

164

Asus ROG Swift PG258Q

144Hz

488

275

Asus ROG Swift PG278Q

120Hz

385

123

Asus ROG Swift PG279Q

120Hz

331

101

Asus TUF Gaming VG279QM

280Hz

378

184

Asus TUF Gaming VG27AQ

165Hz

318

199

BenQ XL2720Z

144Hz

282

119

BenQ XL2730Z

120Hz

309

191

Dell S2716DG

120Hz

328

118

Eizo FG2421

120Hz

386

257

Eizo FS2735

144Hz

331

180

Gigabyte Aorus AD27QD

144Hz

471

129

LG 27GK750F

240Hz

452

199

LG 34GK950F

144Hz

390

235

LG 34UC79G

144Hz

267

141

LG 38UC99

75Hz

308

213

ViewSonic Elite XG270QG

120Hz

434

203

Note: Pulse Width setting at max where applicable.
*Note 2: The Acer XB270HU was later updated to include a 120Hz mode, which will produce a slightly darker maximum luminance
 

Blur Reduction Tests

Of course the main thing we want to test is what improvements the Blur Reduction mode offers when it comes to motion clarity and gaming. The following pursuit camera photos give you an indication of observed motion clarity as the human eye would see it at the top, middle and bottom areas of the screen.


Pursuit camera photos capturing perceived motion clarity in the central region at 100Hz and 144Hz refresh rates

There is an obvious and unfortunate problem with the ELMB mode on the XG27UQ. The locked OD control means that you are stuck at what seems to be the maximum overdrive level. In practice this results in very obvious and distracting overshoot in the form of dark and pale halos as you can see above. This gets worse as the refresh rate lowers, but even at 144Hz it makes ELMB mode unusable. We don't know how this was really missed by Asus of allowed to pass internal testing, but if you're going to lock the OD control in this mode, at least make sure it's locked at a sensible level that doesn't look horrible in practice. Unfortunately this makes ELMB unusable on this display. Perhaps a future firmware update from Asus could allow user control for the OD setting to overcome this, but there's no known plans for that at the moment.

 


Gaming Comparisons

We have provided a comparison of the display against many other gaming screens we have reviewed in a similar size range and across a range of panel technologies. This table is now split by panel technology to make life a bit easier and for quicker comparison.

The XG27UQ is not the fastest IPS-type panel we've tested, with some models reaching down to around 4 - 5ms G2G in the best cases. Here it only reaches 6.8ms G2G although that is at least without any overshoot issues while at the optimal settings. TN Film panels can usually reach faster speeds but keep in mind that is often at the cost of modern levels of overshoot.



Additional Gaming Features

  • Aspect Ratio Control - the screen offers a limited range of aspect ratio controls from the menu with only full and 4:3 modes supported. The default 16:9 aspect ratio of the screen should be common anyway, and your graphics card can always handle other aspect ratios if needed from a PC.

  • Preset Modes - There are quite a few gamer-oriented modes available in the 'GameVisual' preset mode menu including Racing, RTS/RPG mode, FPS mode and MOBA mode.
     

  • Additional features - there are a couple of added features in the OSD which are a Shadow Boost setting, to help boost gamma in darker content and bring out details. There is also several features in the 'GamePlus' menu including crosshair graphic, a timer and FPS counter.

 


Lag

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

Lag Classification

  • Class 1) Less than 8.33ms - the equivalent to 1 frame lag of a display at 120Hz refresh rate - should be fine for gamers, even at high levels

  • Class 2) A lag of 8.33 - 16.66ms - the equivalent of one to two frames at a 120Hz refresh rate - moderate lag but should be fine for many gamers. Caution advised for serious gaming

  • Class 3) A lag of more than 16.66ms - the equivalent of more than 2 frames at a refresh rate of 120Hz - Some noticeable lag in daily usage, not suitable for high end gaming

For the 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)

3.70

Pixel Response Time Element

3.40

Estimated Signal Processing Lag

0.30

Lag Classification

1


 Class 1

The total lag measured was a very impressive 3.70 ms total. The pixel response times should account for pretty much all of that display lag at around 3.40ms, and so we can say that there appears to be almost no added signal processing lag on this screen at around 0.30ms. An impressive result from this display and making it suitable for fast and 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 typical for a desktop monitor nowadays and smaller than TV's by a lot

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 (4K) content natively

HDCP

Yes v2.2

Suitable for encrypted content

Connectivity

2x DisplayPort 1.4 and 2x HDMI 2.0

Useful additional 2x HDMI input for external Blu-ray players or games consoles

Cables

DisplayPort and HDMI

Both cables provided in the box

Ergonomics

Tilt, height. swivel and rotate

Good range of adjustments suitable to positioning the screen in a variety of angles for different viewing positions. All pretty easy to move around.

Coating

Light Anti-glare

Provides clear, non-grainy image and avoids unwanted reflections of full glossy solutions

Brightness range

64 - 491 cd/m2

Good adjustment range offered including a high peak brightness beyond even the manufacturer spec, and also a good lower adjustment range. Flicker free backlight operation

Contrast

1080:1 after calibration

Strong contrast ratio for an IPS panel, helping provide good clarity in shadow detail and darker content. Buying an alternative VA technology panel would provide you a higher contrast ratio if you watch a lot of dark content and miss some shadow detail

Preset modes

Cinema

There is a mode available but by default is is much cooler and brighter than our calibrated mode. May be useful to set up to your liking though

Response times

6.8ms G2G, no overshoot at 144Hz

8.6ms G2G at 60Hz with moderate level of overshoot

Response times are very good overall at upper refresh rates, with no noticeable overshoot when using the optimal response time settings.

At 60Hz the response times are quite a lot slower, so it is not as well suited to 60Hz inputs. The optimal level 3 OD mode also produces some moderate overshoot but nothing too major in practice

Viewing angles

Very good

Thanks to the IPS panel technology, suitable for viewing from a wide range of positions. IPS glow on dark content could present a problem from some wider angles especially in darker room conditions

Backlight bleed

Some bleed

Some bleed on our sample from the lower corners, but will vary from sample to sample and was not too bad

Audio

Headphone output

A headphone jack is provided but there are no integrated speakers

Aspect Ratio Controls

Limited, full and 4L3

The default 16:9 aspect ratio is likely to serve most needs here anyway

PiP / PbP

Neither supported

n/a

HDR support

Nothing meaningful

It can accept an HDR input source, but is only certified to the rather meaningless HDR 400 standard which does not require any form of local dimming and so cannot offer improved dynamic range/contrast. There is some improvements on the colour side of things for HDR content with the wide colour gamut (95% DCI-P3) and 10-bit colour depth

 


Conclusion

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Since it was announced we've had a lot of people asking us for a review of this display, and it's an interesting and significantly more affordable option in the 4K @ 144Hz gaming space. From a gaming point of view the XG27UQ performed mostly well, although there were a few issues. The high refresh rate was of course excellent and offered good motion clarity - 144Hz should really be your baseline requirement nowadays for a gaming display. Adaptive-sync VRR support for both AMD and NVIDIA systems was welcome as ever, input lag was non-existent and there were the usual range of potentially useful ROG gaming extras, settings and features available from the screen. The response times were good, although as with many FreeSync screens it was a bit more fiddly to get the best settings in VRR situations, and the response times weren't quite fast enough at the top end to keep up with the frame rate. There were no major issues and motion performance was still very good, just slightly behind some other 4K @ 144Hz options like the (far more expensive) PG27UQ for instance. Probably the main issue with gaming was the unusable ELMB mode which was a disappointment. There was just far too much overshoot and the mode was too locked down. The arrival of DSC should present an attractive option for those who didn't want to sacrifice colour rendering to reach the higher refresh rates and that worked very well with no visual loss of quality.

Away from gaming the XG27UQ is also an interesting choice if you want something you can work on as well as play. The IPS panel provides the usual solid all round performance with great image quality, good colours and wide viewing angles. The benefits of 4K resolution on a screen this size are somewhat debatable. Certainly you can get a nice boost in image clarity and sharpness that some may find very welcome for general uses as well as for gaming. It does make life a bit more complicated when you have to account for Operating System and application scaling support, but if you already use a 4K screen or have your heart set on one, this is one of the more affordable 4K options that still offers a solid gaming experience. There's wide colour gamut support and a pretty decent factory setup. sRGB emulation is included and is somewhat useable, providing a good setup but unfortunately being a bit restrictive in allowing user control and configuration. Contrast ratio was thankfully decent for an IPS panel - something that has been a bit lacking on other recently tested IPS panels.

Overall the XG27UQ did feel like a trimmed down version of the PG27UQ which is reasonable to expect of course given they are both produced  by Asus but with the move from the ROG Swift premium brand to the lower ROG Strix segment - and of course the significant difference in price. At the time of writing, the XG27UQ retails for £799.99 on special offer from Overclockers in the UK, while the PG27UQ is £1,100 more expensive at £1,879.99! You can check latest pricing in different regions using our direct links below too. That's a huge difference in cost to think about. Asus have cut back on some expensive features and some of the performance is a bit lower as a result. The most obvious difference is that the PG27UQ had a Native hardware G-sync module and a FALD HDR backlight. Those are missing here and the lack of any meaningful HDR experience on the XG27UQ is a shame. There was better response times and overdrive performance overall on the PG27UQ too, along with a more flexible and usable sRGB mode and even a low glow IPS panel. Asus did try to add a few new features to the XG27UQ though with it being newer to try and compensate. DSC is the main one and we expect that to work well and avoid the colour sacrifice concerns that the PG27UQ presented. That's a fairly big improvement to many people but do keep in mind you need a graphics card that supports it too. They even tried to add an ELMB blue reduction mode but that doesn't work well at all sadly. We felt that overall the XG27UQ was a good screen. It has a few issues but it is certainly an attractive and far more affordable option if you are looking for a 4K gaming display.

 

Pros

Cons

4K at 144Hz provides high end gaming experience

ELMB mode is not usable due to locked OD level

Non-existent input lag and VRR support for both NVIDIA and AMD systems

sRGB emulation mode is present and works well, but is a bit restrictive in user control

DSC provides support for max res and refresh rate without having to sacrifice colours

Missing the HDR support and FALD backlight of models like the PG27UQ.

 

Check Pricing and Buy - Direct Links

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