Introduction

There's been a bit of a dilemma for buyers in recent years. Do you prioritise Ultra HD (3840 x 2160, 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. 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 a couple of new displays which would be the first in the market to combine 4K resolution with a high 144Hz refresh rate. In August this year we looked at one of the first models to emerge, the Asus ROG Swift PG27UQ. There was also an equivalent model released by Acer with the same features, specs and panel which is their Predator X27.

As well as offering 4K @ 144Hz, the 27” panel being talked about here 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. It's designed as 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 which can support the necessary bandwidth beyond what older DP 1.2 interfaces could manage.

The first wave of 4K @ 144Hz screens like the Asus ROG Swift PG27UQ and Acer Predator X27 featured the latest NVIDIA G-sync HDR chip which supports the variable refresh rate we know and love. Something that will be extremely important given the high system and graphics card 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 X27 and PG27UQ displays carry the VESA DisplayHDR 1000 and Ultra HD Premium certifications for HDR performance. 

Those initial screens may seem like dream specs for many users, but weren't without a major concern to many people - the retail price. At around £2000 / $2000 they are not cheap, and this has put them in a fairly small niche for those who are willing to fork out this much money for a display, or who want super-high end, cutting edge technology and are willing to pay for the privilege.

To combat this, Acer are now the first to offer an alternative for 4K @ 144Hz gaming, but at a significantly reduced price. Their new Nitro XV273K and Predator XB273K will offer the same 27" sized, 4K resolution, 144Hz IPS-type panel, but will cut back on some of the expensive and complicated FALD HDR features of the earlier Asus PG27UQ and Acer X27 models. This allows them to offer a more affordable monitor choice for those who don't necessarily want or need the HDR support, but want a high refresh, high resolution display still. The Nitro XV273K (reviewed here) is a model with AMD FreeSync support, and will actually be the first model to offer 4K @ 144Hz with FreeSync. The forthcoming XB273K will feature NVIDIA G-sync like the X27, but without the FALD HDR backlight. The expected retail prices are $899 and $1299 USD respectively according to the initial press releases. Certainly more affordable than the top-end HDR capable X27 display. The new XV273K isn't just aimed at gamers either, and there are a range of added extras like a factory calibration, shading hood and ambient light sensor which aren't typically included on gamer-orientated displays.

Note: 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.

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Specifications and Features

The following table gives detailed information about the specs of the screen as advertised:

The XV273K offers a good range of modern connectivity options. This includes two of the latest generation of DisplayPort 1.4 connection which allows support for the very high bandwidth needed to power the screen at 3840 x 2160 @ 144Hz and with HDR. Connection via a single DP 1.4 port can support the screen at 3840 x 2160 @ 120Hz, but you need to use both of them at the same time from compatible graphics cards to reach the full 144Hz refresh rate. We will talk a lot more about that later on. There are also 2x HDMI 2.0 for connection of external devices like games consoles (60Hz maximum). All the 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. In the box are 2x DisplayPort cables, but no HDMI cable. Some regions may ship with an HDMI cable included perhaps, but check if it's something you need.

There is an additional 4 port USB 3.0 hub, with two of the ports located on the back of the screen, and two of them on the left hand side for easy access. There is a headphone jack too and the screen includes 2x 4W stereo speakers. The screen has an external power supply and comes packaged with the power cable and brick you need.

There are a few extra features including a colourful ambient lighting system, light sensor for automatically adjusting the screens brightness, a bundled shading hood and an added motion blur reduction backlight. We will talk about these later on in the review.

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

Power Consumption

In terms of power consumption the manufacturer lists a typical usage of 55W and 0.5W in sleep mode. We carried out our normal tests to establish its power consumption ourselves in a few states.

Out of the box the screen used 50.4W at the default 80% brightness setting. Once calibrated the screen reached 28.3W consumption, and in standby it used only 0.5W. 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 27" models we've tested, and a little less than the Asus ROG Swift PG27UQ (45.1W) which has the added FALD HDR backlight.

Panel and Backlighting

Panel Part and Colour Depth

The Acer Nitro XV273K features an AU Optronics M270QAN02.3 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 AMD 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. AMD consumer grade gaming graphics cards users can use 10-bit, but 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 AMD consumer-grade graphics card for 10-bit colour depth in gaming, as long as it is a game which support that colour depth.

However, while the AMD 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 AMD consumer grade cards. You would need an AMD FirePro 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 XV273K will support 10-bit content and given this is firmly aimed at gamers, that will mean most will use that support from their AMD consumer cards 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 below:

 

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 an 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 90% coverage" of the DCI-P3 colour space according to the specs, something that we will verify and test in a moment. This 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 XV273K can cover beyond that, producing more bright and vivid colours to enhance gaming, multimedia and HDR content. 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

 

Brightness and Contrast

At the top end the maximum luminance reached a very  high 503 cd/m² which was extremely bright, and a lot higher also than the specified maximum brightness of 400 cd/m² from the manufacturer. The availability of a high brightness backlight will be very useful when it comes to using the strobing blur reduction backlight (VRB mode) which we will look at later, or to offer improved peak brightness points within HDR content - even if the screen is lacking any local dimming to actually improve the dynamic range.

There was a wide 399 cd/m² adjustment range in total, so at the minimum setting you could reach down to a moderate luminance of 105 cd/m². This should be low enough for a lot of people in normal conditions, although those wanting to work in darkened room conditions with low ambient light might find it a little limited, as it can't reach as low as some screens. A setting of 3 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 basically a linear relationship as you can see although the adjustment curve seems to be slightly steeper between 50 and 0% brightness levels.

The average contrast ratio of the screen was measured at 1070:1 which was good for an IPS-type panel. This remains stable across the brightness adjustment range.
 

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/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 - 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

Default settings of the screen were as follows:

Initially out of the box the screen was set with the standard preset mode which offered the full native gamut of the backlight. Colours appeared more vivid and saturated compared with a normal sRGB screen, making them appear more bright and colourful. There is an sRGB emulation mode preset as well which we will test in a moment, and that also carries the screen's factory calibration. 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 beyond the sRGB colour space reference (orange triangle) quite considerably in all shades. We measured using ChromaPure software a 132.3% sRGB gamut coverage which corresponds to 97.5% of the DCI-P3 reference and 70.0% of the Rec.2020 reference. This was actually a fair bit beyond Acer's spec of 90% DCI-P3 coverage. There are a range of other colour space modes available in the menu including sRGB, HDR (the same full native gamut), and DCI-P3 which actually offers around 90.8% DCi-P3 coverage and perhaps is where their spec has come from. Default gamma of the screen was recorded at 2.2 average, with a very small 1% deviance from the target which was great news, and showed a similar deviance across all grey shades.

Key Quick Information Box Default setup pretty good with a reliable gamma Colour temp a little too warm Default contrast ratio good at 1061:1 97.5% DCI-P3 coverage measured, beyond spec even sRGB emulation mode available with very good factory calibration

White point was measured at a slightly too warm 6107k being a small 6% out from our 6500k target. Luminance was recorded at a very bright 440 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 80% 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 0.41 cd/m² at this default brightness setting, giving us a good static contrast ratio for an IPS-type panel of 1061:1. 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.

Colour accuracy measurements show a  dE average of 2.4 but keep in mind that the screens wider gamut output is being compared here with an sRGB reference so will be skewed as a result.  Testing the screen with colour gradients showed smooth transitions with only minor gradation evident in the darker tones. There was no sign of any colour banding which was good news.
 

Factory Calibration

The XV273K carries a factory calibration which is applicable in the 'sRGB colour space' mode and is calibrated to achieve accurate grey-scale tracking and a delta E of <1. 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

You have to switch to this mode in the 'colour space' setting in the OSD menu, changing it to sRGB where the smaller colour space is emulated, and where the factory calibration has been applied.

Default settings of the screen in the sRGB mode were as follows:

When you switch to the sRGB mode a lot of the settings in the OSD are unavailable or disappear. This includes settings for contrast, low blue light modes, colour temperature and gamma. You can still alter the brightness control thankfully, which is sometimes locked on displays with an sRGB mode, and normally makes them practically useless. Thankfully you can customise the brightness here on the XV273K. The screen also has the 'Super Sharpness' setting turned on in this sRGB mode which accentuates the sharpness of the screen. You can turn that off if you don't like it.

You can see from the CIE diagram on the left that the colour space now more closely matches the sRGB reference space as intended. We measured using ChromaPure software a 96.4% sRGB gamut coverage which corresponds to 71.1% of the DCI-P3 reference and 51.0% of the Rec.2020 reference and represented a good emulation of this smaller colour space.

Default gamma of the screen was recorded at 2.2 average, with a small 2% deviance from the target which was great news. White point was measured at a slightly too warm 6272k being only a small 4% out from our 6500k target now. Luminance was recorded at a still-too-bright 237 cd/m² which is too high for prolonged general use, you will need to turn that down still even from the 30% setting. The black depth was 0.22 cd/m² at this brightness setting, maintaining a good static contrast ratio for an IPS-type panel of 1083:1. Colour accuracy was excellent with an average dE of 0.9, which was in line than the target of <1 from the factory calibration. Again there was smooth gradients with no banding evident in this mode. Overall it represented a very good factory calibration which was pleasing.

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.

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. 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 after calibration (0% deviance) which fixed the very small 1% deviance we'd seen out of the box at default settings. The white point had also now been corrected to 6485k, sorting out the 6% deviance we had by default. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at a far more comfortable 124 cd/m². This left us a black depth of 0.12 cd/m² and a static contrast ratio of 1019:1 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 1.0. 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 and some very slight banding in places. 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 XV273K comes out of the box set at its native full DCI-P3 colour space, offering more vivid and brighter colours for gaming and multimedia. It has a decent setup in terms of gamma and has a good IPS contrast ratio as well. The white point is a little too warm out of the box, but easy enough to correct through the OSD controls. The screen also carries an excellent factory calibration in the SRGB emulation mode that we were really impressed with, especially considering this is primarily a gaming screen and those are often set up for less "accurate" targets. In that factory calibrated mode we had a reliable sRGB gamut emulation, a good gamma curve, white point with only a couple of % deviance from the targets, and an excellent dE of only 0.9. No complaints about the default setup here and plenty of settings available in the menu too.

When it comes to black depth and contrast ratio the screen performed well for an IPS-type panel, with a calibrated contrast ratio of 10191:1. 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 although they do tend to be slightly better than TN Film panels.

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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 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 was fairly typical for an IPS-type panel, although we had been impressed by the Asus ROG Swift PG27UQ's low glow panel in this area. It looks like the slightly different panel revision here, despite being 4K @ 144Hz, returns to a more standard IPS-glow level than on those top-end FALD HDR models.

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 uniformity of our XV273K sample was not very good unfortunately, although this will of course vary from sample to sample. The main problem was that the left third of the screen was much darker than the central and right hand areas. This wasn't really noticeable in normal usage at all we should point out, but if you were wanting to do any colour critical work, or photo editing for instance you might spot some variation in the luminance of the screen which could cause problems. The left hand side of the screen dropped down to a low of 81 cd/m² which was -48% deviance from the centrally calibrated area. The uniformity was better in the central and right hand areas thankfully with an average deviance of around 2%, although there was a slightly larger variation along the bottom edge as well with a 13% average deviance. Overall, 60% of the screen was within a 10% variance from the centrally calibrated point.

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 with a camera used to capture the result. The camera showed there was no noticeable backlight bleed or clouding on this sample and uniformity was very good. The right hand corners were slightly brighter than the rest of the screen but you couldn't see this in normal use at all.

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 XV273K 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 very good as well, offering an accurate gamma curve, white point and decent contrast ratio for an IPS panel. 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 very low dE for great colour accuracy in the sRGB mode thanks to the very good factory calibration. 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, although a little limited at the lower adjustment range. There is the ability to offer a luminance between 503 and 104 cd/m². This may not be quite dark enough for some people who want to use the screen in lower ambient light conditions, including darkened rooms. A setting of 3 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. 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 4x USB 3.0 ports which is very handy, with 2x located on the back of the screen with the video connections, but 2x provided on the left hand edge which are easy access. There is also a headphone jack if you are sending sound to the screen along with 2x 4W integrated speakers which are probably ok for the occasional YouTube video or mp3. There is a built in ambient light sensor which is located on the top edge of the screen and has 3 levels in the OSD settings which will adjust your screen's brightness depending on your working conditions and other light sources. 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

The XV273K is rated by Acer 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. They also promote a "1ms MPRT" spec which is related to the strobing blur reduction backlight available using the VRB mode.

There is a user control in the OSD menu for the overdrive under the 'Overdrive' setting with 3 options available - Off, Normal and Extreme. The part being used is 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

You will need to keep in mind that these new range of 4K 144Hz displays like the XV273K are very top-end displays, and to power them you are going to need a powerful system for sure. Achieving 3840 x 2160 resolution at up to 144Hz refresh rate 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. It is important that your graphics card has a DisplayPort 1.4 interface(s) as you are going to need that to achieve 4K at these high refresh rates. For this particular screen it will need dual DisplayPort outputs if you want to run at the maximum 144Hz refresh rate at 4K. We will talk about that a bit more shortly. Acer provide two DP cables in the box so you don't need to worry about that thankfully.

You can use the screen with either AMD or NVIDIA graphics cards, but you are going to need a very top of the range card to reach the screen's potential for resolution and refresh rate. AMD cards will be able to support AMD FreeSync as well of course for variable refresh rates, but may be more limited in their power compared to the top end NVIDIA cards. Of course things will improve in the future as well to allow more people to make the most of these kind of resolutions and refresh rates.

Update 8/2/19: The XV273K was one of the first batch of 12 screens certified by NVIDIA as "G-sync Compatible", meaning that through a driver update in January 2019 compatible graphics cards will be able to use G-sync variable refresh rates (VRR) from this display, even though it's not a traditional G-sync screen. So if you're an NVIDIA user, you will be able to enjoy the VRR support as well, and give you more flexibility for higher end graphics card choices. We didn't have chance to test G-sync performance on this screen when we had it with us (before the announcement and update from NVIDIA) but given it is a proper certified "G-sync Compatible" display it means it has passed NVIDIA's quality and performance tests and should work fine. Third party reports of the screen since also confirm it works well.
 

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 at 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 Overdrive setting 'off' the average G2G response times were fairly slow at 12.2ms 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 8.1ms, although some low to moderate levels of overshoot started to creep in on some measurements. This was not very noticeable in practice or motion tests though thankfully. Pushing up to the 'extreme' setting helped reduce the response times a little more, down to 6.1ms G2G now. However a very large amount of overshoot was introduced, which was very noticeable in practice. There were lots of pale halos behind moving objects and it was not really useable. Response times were more than adequate to keep up with the 60fps frame rate at 60Hz, and we would recommend opting for the 'Normal' overdrive mode if you're gaming from a console or running at 60Hz.

 

High Refresh Rates and 120Hz

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 when you first connect the screen is 120Hz, which we will remind you is a big step up for panels of this 4K resolution. We will explain how you reach the maximum 144Hz refresh rate in a moment.

The overdrive and response time behaviour of the screen does vary depending on the active refresh rate. We didn't bother testing the 'off' mode here. The 'normal' mode showed a change in the response time behaviour compared with running the screen at 60Hz. The response times actually increased a little bit here, from 8.1ms G2G at 60Hz, to 9.1ms G2G here at 120Hz. This seems a little odd, as you would want the pixel transitions to improve in speed as the refresh rate increased, in order to keep up with the higher frame rate demands. At 60Hz you need response times to be consistently under 16.6ms to avoid additional motion blur caused by the frame rate, but at 120Hz they need to really be under 8.3ms to keep up. Here on the XV273K in the 'normal' overdrive mode they were not quite keeping up with the frame rates at 120Hz. Some of the transitions, particularly those from black to lighter shades were a little too slow and it introduced a bit of dark smearing on moving content. It was not a major issue to be fair, and quite slight but we would have liked the response times to be a bit faster really if possible. The good news about this 'normal' overdrive mode at 120Hz is that because the response times are not quite as fast as they were at 60Hz, it has at least removed all signs of overshoot that we had before. It had been at low/moderate levels at 60Hz but was gone by the time you reached these higher refresh rates.

Pushing the OD setting up to the maximum 'extreme' setting improved the response times quite a lot, but unfortunately introduced a moderate amount of overshoot on a few transitions. In visual tests there was some very slight pale trails behind moving objects but to be honest they were minimal and probably unlikely to cause any real problems in gaming. With the response times now consistently under 8.3ms, they were more than fast enough to keep up with the 120Hz frame rate. In motion tests the image looked sharper and clearer, with less of the smearing you can detect in the 'normal' mode.

One other thing of note was that the screen was perfectly happy allowing a lower resolution at a high refresh rate like 120Hz. You could switch down to 2560 x 1440 at 120Hz or 144Hz for instance without issue, if you want to reduce your resolution for any reason, or to create less of a drain on your system.

 

Chroma Sub-sampling (n/a for maximum 144Hz)

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 (except 144Hz which we will cover in a moment) 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.

By default the refresh rate options available on the XV273K in the graphics card control panel are 30, 60 and 120Hz. At 60Hz it 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 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 AMD consumer 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 60Hz anyway so 10-bit is there if you need it.

If you want to push the screen up to high refresh rate of 120Hz 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. You can stay at 10-bit colour depth but sacrifice the chroma if you want.

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 XB273K. 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 at 120Hz and maintain the 10-bit colour depth output, then you will need to use this 4:2:2 chroma sub-sampling setting in the graphics card 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. We will talk about the 144Hz refresh rate in a moment as that operates in a different way on the XV273K.

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.

(left) No colour reduction or chroma sub-sampling (i.e. 4:4:4) vs. 4:2:2 sub-sampling (right)
with size 16 font at 3840 x 2160 resolution
 

 
(left) No colour reduction or chroma sub-sampling (i.e. 4:4:4) vs. 4:2:2 sub-sampling (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 far 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 and 10-bit colour depth you are probably not going to worry about any minor drops in colour fidelity we don't think. If the sub-sampling bothers you then you can easily drop to 8-bit colour depth and stick to a full 4:4:4 sampling. Or alternatively you can also use the 144Hz mode...

144Hz Mode

The XV273K can also support a refresh rate of 144Hz if you really want to push the capabilities of your system and be at the bleeding edge of refresh rate and resolution support in the monitor market. On the first wave of 27" 4K 144Hz screens like the Asus ROG Swift PG27UQ that we tested, and Acer's equivalent Predator X27 screen there were some limitations to how 144Hz was used. On those G-sync enabled screens the 144Hz mode was actually achieved through an overclock setting in the OSD menu. You had to enable that before you could select 4K @ 144Hz in your graphics card control panel. Then, because of the bandwidth limitations of the DisplayPort 1.4 connection, you had to make some sacrifice to the colours if you wanted to reach the resolution and refresh rate of 4K @144Hz that we've talked about above. You always had to drop to 4:2:2 chroma sub-sampling to use 144Hz on those displays. On the XV273K that is not necessary, and you can game at 4K @ 144Hz with 10-bit colour and full RGB range (no chroma sub-sampling)!

This is achieved by connecting two DisplayPort cables between your graphics card and the screen. The screen has dual input for DP 1.4 and so you will of course need dual DP 1.4 output from your graphics card to support this feature. You connect both up to the screen, and can even use the two provided DP cables in the box. After this you need to enable the "4K-144Hz" mode in the OSD menu as shown above. Acer refer to this as an overclock in their documentation, although it's not really overclocking anything, it's just bonding dual DP 1.4 connections together. The screen quickly goes blank and then comes back on and it should then be an available option in the 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.

By using dual DP connections the screen can support enough bandwidth to run at these maximum settings without having to make any colour sacrifices at all. The screen is still detected in Windows and your graphics card as a single screen as you can see below. This method of using dual DP connections was not possible on the first wave of 4K 144Hz displays as they only had a single DP connection due to the G-sync module limitations. We expect there to be similar limitations with the forthcoming Acer Predator XB273K which is basically the G-sync version of this display. That is almost certainly going to be limited to a single DP connection because of the G-sync module, and so to reach 144Hz you are likely to need to use chroma sub-sampling like on the Asus PG27UQ and Acer X27 models. Anyway, on the XV273K you can use the dual DP connections and not have to sacrifice anything to reach 144Hz at 4K resolution.

It should be noted that you cannot reach 144Hz using only a single DP connection on this screen, even if you attempt to drop the colour depth or use chroma sub-sampling. Also on another note, when you enable the 4K-144Hz mode in the menu, it seems to restrict you from then selecting anything above 120Hz for non-native resolutions like 2560 x 1440.

Update 8/2/19: for clarity as well, if you run at this 4K-144Hz mode you cannot use FreeSync / G-sync as the variable refresh rate tech won't work from a dual display output. Also the HDR mode (which doesn't do much to be honest anyway) isn't available in this mode.

Once the 4K-144Hz mode is activated on the monitor and you've connected both DP cables you should see 144Hz listed as an available refresh rate in the graphics card control panel, including when running at the native 3840 x 2160 resolution. You can see that 10-bit colour and full RGB range without chroma sub-sampling is selectable here too as shown above.

After enabling the 4K-144Hz mode via the OSD menu and making the necessary setting changes in the graphics card control panel we measured the response times again at the optimal 'extreme' setting for high refresh rates. At 144Hz there was a small drop in response times compared with 120Hz, now measured to 6.4ms G2G, from 6.2ms we'd seen at 120Hz. At these levels it still ensured 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. Although the response times had dropped by 0.2ms on average, the overshoot had also dropped which was very pleasing. There was no real sign of any overshoot artefacts in practice at 144Hz in the extreme mode.

If you can achieve high refresh rates of 120 - 144Hz on this screen then the 'extreme' overdrive mode will provide the best experience, with the fastest response times, lowest levels of motion blur and very little noticeable overshoot. If your refresh rates are going to drop lower than this, you might start to see overshoot becoming too districting, with pale halos behind moving objects. This gets worse the lower the refresh rate goes. At <120Hz we felt the 'normal' mode was optimal on this display.

 

AMD FreeSync

    

The presence of AMD FreeSync 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. FreeSync works by synchronizing the display’s refresh interval with the incoming frame rate, banishing lag and ensuring gameplay stays 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 display's benefits.

Update 8/2/19: The XV273K was one of the first batch of 12 screens certified by NVIDIA as "G-sync Compatible", meaning that through a driver update in January 2019 compatible graphics cards will be able to use G-sync variable refresh rates (VRR) from this display, even though it's not a traditional G-sync screen. So if you're an NVIDIA user, you will be able to enjoy the VRR support as well, and give you more flexibility for higher end graphics card choices. We didn't have chance to test G-sync performance on this screen when we had it with us (before the announcement and update from NVIDIA) but given it is a proper certified "G-sync Compatible" display it means it has passed NVIDIA's quality and performance tests and should work fine. Third party reports of the screen since also confirm it works well.

The VRR range supported by the screen is 48 - 120/144Hz but will depend on your resolution. The "overclocked" (as Acer like to refer to it as) 4K-144Hz mode will not support FreeSync/VRR, as confirmed by the user manual. It looks like this is a limitation of using a dual DP connection, with FreeSync only working when powering the screen from a single interface. So if you're running at 4K resolution you will only be able to use FreeSync between 48 - 120Hz. If you have dropped to a lower resolution, like 2560 x 1440 for instance, you can run at a refresh rate of up to 144Hz easily, without needing to use dual DP connections or making any OSD changes. So if you're running at a lower resolution than the native 4K, the FreeSync range will be 48 - 144Hz.

You need to enable FreeSync from within the OSD menu to use it, at which point the AMD graphics card control centre detects the screen as a FS display and allows you to turn it on. Once enabled as a setting in the OSD menu, the overdrive control actually becomes locked to the 'normal' mode, so it is not possible to use the 'extreme' mode if you wanted to. Given that the screen is going to vary the refresh rate between 48Hz and 120/144Hz, and we know that massive amounts of overshoot are introduced at the lower refresh rates when using the 'extreme' mode, this is not really a problem anyway. The 'normal' mode is optimal here and it's good that it hasn't completely disabled the overdrive. Even if you disable FreeSync at your graphics card level, the OSD overdrive control still remains locked to 'normal' unless you disable FreeSync in the monitor OSD menu as well.

(144Hz measurements for FreeSync only applicable at resolutions below the native 4K)

As you can see, the response time behaviour when using FreeSync is perhaps opposite to how you might expect. The level of overdrive applied to the panel is reduced as you increase the refresh rate. We've seen this behaviour on other FreeSync screens in the past as well, but you would have thought it would work the other way around. As refresh rate increases, so too does the frame rate, and so you need to drive the pixels faster to keep up. On the XV273K it is working in reverse, so response times get a bit slower as the refresh rate goes up. Not by a massive amount, but they are getting a little slower with each step. On the flip side this does mean that the overshoot artefacts are reduced and entirely eliminated by the time you reach higher refresh rates which is good news.

The net result is that at the top end of the FreeSync range the response times are a little too slow to properly keep up with the frame rate demands. You do get a bit of added motion blur and a little dark smearing in practice on moving content, particularly where content is changing from black to grey. It was not a major issue and thanks to the high refresh rate the motion clarity is still very good. It is also not as bad as you would see on many VA technology panels which have much slower black > grey transitions in most cases. There is still less black smearing than you'd see from a typical VA panel. We would have just liked to see slightly faster response times in this 'normal' overdrive mode to keep up properly with the high refresh rates of >100Hz. It would have been nice if the overdrive could have been pushed up to the 'extreme' setting automatically when refresh rates got up to that top end, but that's obviously not practical. Limiting the overdrive mode to the 'normal' setting when FreeSync is used is a sensible step and overall the performance was still a pleasant experience.
 

If your system is powerful enough to run the screen at high refresh rates of 120Hz and above (perhaps when running at lower resolutions), and you don't want to use VRR, or you want to use the VRB motion blur reduction mode instead, then you can probably switch up to the 'extreme' overdrive setting for improved performance. You will need to turn 'FreeSync' off in the OSD menu to achieve that.

 

Detailed Response Times
144Hz Refresh Rate, Overdrive = Extreme

 

There were lots of different considerations for gaming depending on your resolution, achievable refresh rate, whether you want to use FreeSync or not etc. To keep consistent with our other reviews, we took some further measurements at the settings where response times of the panel, and the motion clarity in moving content were optimal. This was at the maximum 144Hz refresh rate and with the overdrive setting on 'extreme' (FreeSync turned off).

The average G2G figure was measured at 6.7ms now which was excellent for an IPS-type panel. This was with very low levels of overshoot that were basically unnoticeable in practice. The highest level of overshoot was seen on the transition from white to light grey (255 - 200) which was also the fastest measured response time of 3.3ms, below the 4ms spec even. This screen is more than capable of handling fast paced gaming thanks to its low response times, high refresh rate and low levels of overshoot. Our earlier sections talk about variations at 60Hz, with different resolutions and with FreeSync in use.

 

Visual Response Boost (VRB) Blur Reduction Mode

Normal VRB mode at 144Hz operation. Horizontal scale = 5ms


Extreme VRB mode at 144Hz operation. Horizontal scale = 5ms

The strobing in the VRB mode depends on the active refresh rate. The mode is available at either 120Hz or 144Hz refresh rates, regardless of resolution and whether you need to use the 4K-144Hz mode to reach the maximum resolution at 144Hz. At 144Hz (shown above) the strobing is in sync with the refresh rate, every 6.94ms. The difference between the normal and extreme modes relates to the "on" period of the strobe, with the extreme setting having less "on" time and therefore a darker appearance to the screen. This is designed to help improve motion clarity even more which we will look at in a moment. At 120Hz the strobing works but is slightly out of sync with the refresh rate, strobing every 8.25ms instead of the required 8.33ms.

Brightness Range

We also wanted to test the brightness limit available when using VRB (at 144Hz in the table above). You can achieve a higher brightness by running the VRB mode at a lower 120Hz refresh rate but it won't impact it much. There is no control over the brightness level when using the VRB setting, other than changing between the normal and extreme modes as we said before. It was good to be able to reach high brightness levels of close to 200 cd/m2 here, giving users an option if they want brighter gaming with a blur reduction backlight.
 

Maximum Blur Reduction Brightness - Display Comparison

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 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.

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 with VRB

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. We were pleased with the results we'd seen from LightBoost backlights when we tested them, and also from the natively supported blur reduction feature on other displays including the other popular gaming models we've tested.

VRB enabled, upper, middle and lower screen areas of the screen showing cross-talk

We used the BlurBusters full-screen TestUFO online motion test to put the feature through its paces. There is a bit of an issue here which was related to strobe cross talk. The strobe cross talk is caused by the timing of the strobe in relation to the refresh rate, and can result in a ghost image behind the moving object. The above results show the clearest image in the upper areas of the screen. Here, the moving UFO object did become sharper and easier to track, and motion clarity was improved quite nicely compared with standard VRB-off motion blur tests. However, as you moved down the screen the cross talk and ghosting became more noticeable. It was moderate in the middle area of the screen which is perhaps the most important given your focus there in gaming and multimedia. At the bottom of the screen it was a bit worse still.

You can't eliminate strobe cross talk completely, but this could have perhaps been tweaked better by Acer to provide a more central area of the screen with the minimal ghosting, and cut down on some of the more severe examples resulting at the bottom area of the screen. The 'extreme' mode did help reduce a bit of the ghosting and cross-talk in practice, but only by a small amount. If you don't mind the darker image (or prefer it perhaps depending on your ambient light conditions) then that extreme VRB mode does provide slightly better motion clarity performance. The ability to use it at lower refresh rates below 120Hz (even at the risk of visible flickering) may have been useful to some people but is sadly not possible here.

 

Gaming Comparisons

We have provided a comparison of the XV273K against many other screens that we have tested. The overall responsiveness of the XV273K (6.7ms) was good, and similar to many of the other top end high refresh rate IPS panels we've tested. The Asus ROG Swift PG27UQ (4K @ 144Hz, but with FALD HDR backlight and G-sync) was a bit faster at 5.3ms G2G, as were some of the other 27" high refresh rate IPS screens with G-sync like the Asus ROG Swift PG279Q (5.0ms) and Acer Predator XB270HU (5.5ms) for instance. However, the XV273K was a little faster than some of the 100 - 144Hz IPS panels like the Acer Predator X34 (7.9ms) and LG 34GK950F (8.2ms) for instance. This was all with very low levels of overshoot as well which was great news. The TN Film panels here like the Asus ROG Swift PG278Q (144Hz, 2.9ms) and certainly the PG258Q (240Hz, 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 4 options for hardware level aspect ratio control options, with settings for full, aspect, 1:1 pixel mapping and even a 21:9 mode 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 three saveable preset modes for gaming in the OSD menu, for action, racing and sports. You can customise your screen settings as you wish and then save them to one of the 3 modes. This seemed to save most settings, although the blur reduction (VRB) backlight didn't seem to be saveable as a setting, it was a universal on or off in the menu.

• Extra Settings - within the OSD menu there are also options for a Refresh rate counter display, and an "aim point" target

 

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.

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 6.40ms. With approximately 3.35ms of that accounted for by pixel response times we had an estimated signal processing of just 3.05ms, which was next to nothing and in keeping with other high-end gaming screens we've tested in the past. It was faster than some other models we've seen in the past with FreeSync as well. 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:

Conclusion

We spend a massive amount of time producing these detailed reviews, and this one seems to be even bigger than normal! Loads to test and plenty of exciting and interesting things to look at. If you appreciate and enjoy our reviews, and would like to help support TFTCentral we really appreciate it.

It is really great to see new options emerging for 4K @ 144Hz gaming displays, considering that the first wave were extremely expensive. Sure, the high end FALD HDR backlights have been dropped to make that possible, but it does open up the market for those who aren't as bothered about HDR right now, and just want to enjoy the high refresh rate and high resolution combination. The 4K panel provides a very high level of detail here, even at a relatively small 27" screen size. You're going to need a very powerful system to run this display, but the high refresh rates bring smooth and fluid gaming, with improved motion clarity compared with the previous range of 60Hz-only screens. It's useful to see AMD FreeSync included here and even the new NVIDIA G-sync Compatible certification, and it's actually the first 4K @ 144Hz display to offer FreeSync instead of only G-sync which is bound to be of interest to AMD users. That technology will help your system cope with the demands of this screen nicely. The response times were very good from the panel as well, although they could have been slightly faster at the very top end when using the 'normal' response time mode, which you are restricted to if you're using FreeSync as well. Still, they were good enough to offer a god motion performance across the range. Acer have introduced a clever way of supporting 4K @ 144Hz without the need for any colour sacrifices, although it is a bit of a shame that you can't reach 144Hz when using FreeSync/G-sync. Achieving high refresh rates around 144Hz without VRR does afford you the chance to push the overdrive setting and offer the absolute optimal experience but might be a challenge for many systems right now.

In other gaming considerations the screen had a very low lag which was excellent news, and not always the case for FreeSync displays. The added motion blur reduction backlight (VRB) option will be of interest to some people for sure. You get a nice boost in colours from the wider colour space, and there's also a fair few extras and OSD options available to enhance the experience.

Away from gaming we were impressed with the screen in other areas too. The IPS-panel offers strong all round performance with wide viewing angles and a stable image. The default setup was good and the factory calibrated sRGB mode was even better. It was nice to see options to run the screen either with the full native DCI-P3 gamut or sRGB if you wanted here. The screen was a little limited when it came to minimum brightness adjustments so if you use your PC in dark conditions a lot it might be a little too bright for some. The OSD was annoying and slow to use, but that's our only significant gripe really with the XV273K.

If you are keen to enter the world of 4k @ 144Hz but don't want to fork out for the top of the range HDR-capable models like the Predator X27, then the arrival of the XV273K (and soon XB273K with G-sync) will be music to your ears. The performance and features was impressive and the new lower pricing makes them an attractive option.