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Introduction

Acer leapt back in to the mainstream monitor market around this time last year with the release of some exciting new gaming screens. They haven't looked back since. Their Predator series has garnered a lot of attention with innovative technology developments for gamers. If we think back to Feb 2015 we tested the world's first 144Hz IPS panel in the Acer XB270HU. Since then we've also reviewed their ultra-wide 34" gaming screens, the FreeSync capable XR341CK and G-sync capable X34. Acer were the first to start pushing the refresh rate as well, with overclocking supported from the monitor itself, offering impressive performance from what are currently some modestly spec'ed panels. For instance, their X34 pushed a normal 60Hz IPS panel from LG.Display successfully up to 100Hz. They also pushed the boundaries of their 35" ultra-wide screen, the Z35, where it's native 144Hz VA panel could be overclocked to 200Hz!

We've got with us now one of Acer's other new gaming screens. The XB271HK (not to be confused with the recently released XB271HU) is a 27" sized screen with an Ultra HD 3840 x 2160 resolution ("4k") IPS-type panel for a high pixel density and super-sharp image. It's a 60Hz panel given current bandwidth limitations of DisplayPort connections but they have paired it with NVIDIA G-sync technology to help users run a high resolution screen for gaming. It carries the same zero-frame styling as some of their other new models as well. We hope to see Acer continue to push the boundaries for gaming displays and remain a solid player in this space for years to come. Let's see how the XB271HK performs in our tests.

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Specifications and Features

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

The XB271HK offers a limited range of connectivity options given the use of a G-sync module. However, these have improved since the early G-sync capable screens released which only featured a single DisplayPort interface. This model offers DP 1.2a and an additional HDMI 1.4 input as well which is useful. The digital interfaces are HDCP certified for encrypted content and the video cables are provided in the box for DisplayPort only, along with a USB cable.

The screen has an internal power supply with the power cable you need in the box. There are also 4x USB 3.0 ports, 2 located on the back of the screen next to the video and power connections and 2 easy-access ports on the left hand side. There are also 2x 2W stereo speakers and an audio out connection offered but no further extras like card readers, ambient light sensors or human motion sensors provided as those are more aimed at office uses, while this is primarily a gaming screen.

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

OSD Menu

   
Above: OSD control buttons on the bottom edge of the screen. Click for larger version

Power Consumption

In terms of power consumption the manufacturer lists a power on usage of 71.5W, and 0.42W in standby. We carried out our normal tests to establish its power consumption ourselves.

We tested this ourselves and found that out of the box the screen used 54.9W at the default 80% brightness setting. Once calibrated the screen reached 38.5W consumption, and in standby it used only 0.5W. We have plotted these results below compared with other screens we have tested.

Panel and Backlighting

Panel Part and Colour Depth

The Acer XB271HK features an AU Optronics M270QAN01.1 AHVA (IPS-type) panel which is capable of producing 1.07 billion colours. This is achieved with a true 10-bit colour depth as opposed to using any Frame Rate Control methods, according to the panel spec sheet. Keep in mind whether this is practically useable and whether you're ever going to truly use that colour depth. You need to have a full 10-bit end to end workflow to take advantage of it which is still quite expensive to achieve and rare in the market, certainly for your average user. This includes relevant applications and graphics cards as well, so to many people this 10-bit support might be irrelevant.

We want to try and ensure there's no confusion between AHVA and IPS as well at this juncture. AHVA (Advanced Hyper Viewing Angle) is a relatively new technology developed by AU Optronics, not to be confused with their more long-standing technology AMVA (Advanced Multi-Domain Vertical Alignment). It is AU Optronics' answer to LG.Display's very popular, and long-established IPS (In Plane Switching) technology. Testing of this technology has revealed that it is for all intents and purposes the same as IPS. Performance characteristics, features and specs are all pretty much identical. AUO weren't allowed to simply call their technology IPS due to trademark issues, which is why they adopted their own new name. Samsung are the same with their PLS (Plane to Line Switching) panel tech, which is another IPS-clone. You will see pretty much all monitor manufacturers now simply use the term IPS, since it is so well known in the market, but underneath they may be using an IPS version from LG.Display, AU Optronics or Samsung potentially. People should not get concerned with the semantics here, which is why we will continually refer to this as an "IPS-type" panel throughout the review.

The part is confirmed when dismantling the screen:

Screen Coating

The screen coating is a light anti-glare (AG) offering. It isn't a semi-glossy coating, but it is light as seen on other modern IPS type panels. Thankfully it isn't a heavily grainy coating like some old IPS panels feature and is also lighter than modern TN Film panel coating. It retains its anti-glare properties to avoid too many unwanted reflections of a full glossy coating, but does not produce an too grainy or dirty an image that some thicker AG coatings can. There were some very slight cross-hatching patterns visible on the coating if you looked very closely, but nothing to the extent of what some people find problematic on the U2713HM model.

Backlight Type and Colour Gamut

The screen uses a White-LED (W-LED) backlight unit which is standard in today's market. This helps reduce power consumption compared with older CCFL backlight units and brings about some environmental benefits as well. The W-LED unit offers a standard colour gamut which is approximately equal to the sRGB colour space. Anyone wanting to work with wider colour spaces would need to consider wide gamut CCFL screens or the newer range of GB-r-LED type (and similar) displays available now. 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 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 = 1ms

At 100% brightness a constant voltage is applied to the backlight. As you reduce the brightness setting to dim the backlight a Direct Current (DC) method is used, as opposed to any form of PWM. This applies to all brightness settings from 100% down to 0%. The screen is flicker free as a result, as advertised.

For an up to date list of all flicker-free (PWM free) monitors please see our Flicker Free Monitor Database.

Contrast Stability and Brightness

The brightness control gave us a very good range of adjustment. At the top end the maximum luminance reached 264 cd/m² which was a little shy of the specified maximum brightness of 300 cd/m² from the manufacturer. There was a decent 231 cd/m² adjustment range in total, and so at the minimum setting you could reach down to a low luminance of 33 cd/m². This should be adequate for most people wanting to work in darkened room conditions with low ambient light. A setting of 33 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, using a Direct Current (DC) method for all brightness settings between 100 and 0% and so the screen is flicker free as advertised.

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 pretty much a linear relationship as you can see.

The average contrast ratio of the screen was very good for an IPS-type panel with an average of 1016:1. This was mostly stable across the brightness adjustment range as shown above although it did seem to go a bit higher at 20% brightness and less.

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 Performance and Setup

Default settings of the screen were as follows:

Acer XB271HK - Default Settings

  

Initially out of the box the screen was set in the default 'standard' eColor preset mode. You could tell the screen was using a standard gamut backlight and the image looked good to the naked eye, but too bright for comfortable use with the default brightness set at 80%. Colour balance felt pretty good as well, if perhaps slightly too warm. 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) is roughly equal to the sRGB colour space. There is some over-coverage in some shades, particularly in blues and greens where it extends a little beyond the sRGB reference. Default gamma was very good with a 2.2 average measured, and only a small 2% deviance. White point was a little off from the target, being measured at 6125k (a little too warm) and so a little off the 6500k target, but still with a low 6% deviance. The screen was set in the default 'standard' colour temp mode incidentally with RGB not available to tweak unless you enter the 'user' mode which we will do later for calibration.

Luminance was recorded at a very bright 237 cd/m² which is too high for prolonged general use. 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 0.23 cd/m² at this default brightness setting, giving us a very good static contrast ratio (for an IPS-type panel) of 1014:1. Colour accuracy was excellent with an average dE of only 1.2 and maximum of 2.7. Testing the screen with colour gradients revealed smooth gradients with only some very minor gradation evident in darker tones. Overall default setup was very good and you only really need to carry out some minor adjustment to the brightness and colour temperature which is easy enough through some basic adjustments as shown in the next section.

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.

Acer XB271HK - Calibrated Settings

   

If you make any changes to the OSD you are automatically moved in to the 'user' eColor mode. To get access to the RGB channels you need to change the colour temp setting to 'user', and then you can drill in to that section further to change those settings directly. All the OSD changes listed in the table above allowed us to obtain an optimum 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 as much as possible. After this we let the software carry out the LUT adjustments and create an ICC profile.

The minor 2% deviance in gamma out of the box had been corrected here through the profiling process. The white point was now corrected nicely thanks to the RGB adjustments, being measured at 6500k spot on (0% deviance) and correcting the small 6% deviance we had out of the box. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at 120 cd/m². This left us a black depth of 0.13 cd/m² and maintained a good static contrast ratio (for an IPS-type panel) of 943:1. Colour accuracy of the resulting profile was very good, with dE average of 0.4 now. Testing the screen with colour gradients revealed smooth gradients with only some minor gradation evident in darker tones as you see from most screens. There was no banding evident 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.

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. 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 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 very good really. There was a decent gamma curve, low dE and strong contrast ratio for an IPS-type panel. The only thing which really needed correcting (other than the normal brightness adjustment to suit) was the white point, which thankfully is nice and easy to correct through basic OSD adjustments and was only slightly out to start with anyway. The IPS-type panel delivers stable and reliable images without obvious contrast and colour tone shift that you see from other gaming screens based on TN Film panels.

The display was good for an IPS-type panel when it came to black depth and contrast ratio. With a calibrated contrast ratio of 943:1 it was comparable to some of the other gaming IPS-type screens we've tested, like the Acer XB270HU (1000:1) and Asus ROG Swift PG279Q (989:1). It was not quite as high as some modern IPS-type panels like the Dell U2515H (1138:1) for instance. Of course none of these IPS screens can compete with VA panel types which can reach over 2000:1 easily, and even close to 5000:1 in the case of the 24" Eizo FG2421 shown here.

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 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. There was some slight pink tone introduced from wide vertical angles. 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. All as expected really from a modern IPS panel.

This is one of the big positives of using IPS panel technology as opposed to the common TN Film matrices which are generally adopted in gaming displays. If you compare the viewing angles to the TN Film based Asus ROG Swift PG278Q for example you can see the obvious differences, especially vertically. Some people argue it won't matter if you're just viewing the screen head on anyway and that's true to a point. However, even if you are viewing it head on, as you glance to the sides, or particularly as you glance up or down vertically, there are subtle colour tone and contrast shifts caused by the pixel alignment on the TN Film panel. This isn't really a problem for general uses and gaming, but if you were doing any colour critical work or photo editing it is not ideal. The IPS panel of the XB271HK shows a far more stable image thanks to the differing panel technology, and does not suffer from these viewing angle issues. This is also important should you want to use the screen for gaming from a distance, where your viewing position may vary more, or where you may have additional players who can't view the screen as head on as you. Likewise for movie viewing the changing angles of view can be problematic on a TN Film panel. Those issues are not as much of a problem on the IPS panel of the XB271HK.

Above: View of an all black screen from the side. Click for larger version

On a black image there is a characteristic white glow when viewed from an angle, commonly referred to as "IPS-glow". This is common on most modern IPS-type panels and can be distracting to some users. The level of glow here is the same as other recent gaming IPS panels we've seen like the Acer XB270HU and Asus MG279Q and is pretty typical of a modern IPS-type panel. If you view dark content from a normal head-on viewing position, you can actually see this glow slightly as your eyes look towards the edges of the screen. Some people may find this problematic if they are working with a lot of dark content or solid colour patterns. In normal day to day uses, office work, movies and games 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, the effect reduces as you do not have such an angle from your eye position to the screen edges.

This is one area where the TN Film panel of some other gaming displays is better, as there is far less pale glow (Asus ROG Swift PG278Q example again) from an angle on dark content. For dark room conditions, and a lot of dark content some people might prefer to live with the more restrictive viewing angles and less glow of the TN Film panel. Others might want to use the screen for more all-round uses and prefer the IPS panel. It's down to preference really and your individual uses.

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 luminance uniformity of the screen was reasonably good although showed some variance around the edges, particularly on the right and left hand sides. Luminance dropped to 98 cd/m² in the most extreme case (-22.45% deviance, bottom left hand area) but most of the edges were around 10 - 15% deviance from the centrally calibrated point of 120 cd/m². Overall, about half of the screen was within a 10% variance from this reference point.

Backlight Leakage

Above: All black screen in a darkened room. Click for larger version

As usual we also tested the screen with an all black image and in a darkened room. A camera was used to capture the result. The camera showed there was some clouding detected from the four corners, although it was not too severe.

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 XB271HK feature a massive 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) 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.

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.

You do need to keep in mind the need for a compatible graphics card with a suitable output which can handle this resolution, and preferably at 60Hz refresh rate. DisplayPort and HDMI 2.0 are the only options to run the screen at its native 3840 x 2160 res at 60Hz, so in the absence of HDMI v2.0 here you will need to use DisplayPort. When running at native resolution this model is recognised as a single display which makes life easier than some of the early MultiStream (MST) models. It's also good to see support for 60Hz refresh rate as some 4k models only offer 30Hz support which is very limiting, even in day to day uses (certainly for gaming!).

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 decent as well, offering an accurate gamma curve, decent contrast ratio and low dE. The brightness range of the screen was also very good, with the ability to offer a luminance between 264 and 33 cd/m². This should mean the screen is perfectly useable in a wide variety of ambient light conditions, including darkened rooms. A setting of ~33 in the OSD brightness control should return you a luminance close to 120 cd/m² out of the box. On another positive note, the brightness regulation is controlled without the need for the use of the now infamous Pulse-Width Modulation (PWM), and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry. There was no audible noise or buzzing from the screen, even when specifically looking for it using test images with a large amount of text at once. The screen also remains cool even during prolonged use.

The screen offers 4x USB 3.0 ports (with charging capabilities also) which is very handy. 2 are on the left hand edge of the screen for easy access. There aren't any other extras like card readers or ambient light sensors offered though. The stand offers a wide range of adjustments which is great news, allowing you to obtain comfortable viewing positions easily.

Responsiveness and Gaming

The XB271HK is rated by Acer as having a 4ms G2G response time, which indicates the panel uses overdrive / response time compensation (RTC) technology to boost pixel transitions across grey to grey changes. There is user control over the overdrive impulse within the OSD menu using the 'OD' option. The part being used is the AU Optronics M270QAN01.1 AHVA (IPS-type) panel. Have a read about response time in our specs section if you need additional information about this measurement.

We will first test the screen using our thorough response time testing method. This uses an oscilloscope and photosensor to measure the pixel response times across a series of different transitions, in the full range from 0 (black) to 255 (white). This will give us a realistic view of how the monitor performs in real life, as opposed to being reliant only on a manufacturers spec. We can work out the response times for changing between many different shades, calculate the maximum, minimum and average grey to grey (G2G) response times, and provide an evaluation of any overshoot present on the monitor.

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.

Response Time Setting Comparison

The XB271HK comes with a user control for the overdrive impulse available within the OSD menu in the 'setting' section as well as via one of the quick launch menu buttons. There are 3 options available here under the 'OD' setting (OD = Overdrive). First of all we carried out a fairly small set of measurements and motion tests in both settings for the purposes of identifying which was the optimum response time setting, over DisplayPort and at the maximum 60Hz refresh rate.

Firstly we tested the response times with the setting off. Response times were pretty slow, particularly on grey to grey transitions. An average of 11ms G2G was measured here which was moderate for an IPS panel to be fair. Given there was no overdrive being applied, there was no overshoot at all in this mode.

With OD turned up to the middle 'normal' setting, we saw an improvement in response times. Average response times were now a decent 7.7ms G2G and with the very low levels of overshoot, this made it one of the fastest IPS-type panels we've tested actually at 60Hz. There were improvements in perceived motion clarity as well with a less pronounced blurring to moving images. Overshoot remained at a low level which was not evident in practice.

Perhaps predictably the highest 'extreme' setting was too aggressive. The response times had been improved down to 6.1ms G2G average, but the overshoot was now significant. You could see dark and pale trails in moving objects although to be honest they weren't overly distracting in most cases. The overshoot wasn't at some of the crazy levels we've seen from other aggressive overdrive controls on other screens. We still preferred the overshoot-free 'normal' mode though and would recommend sticking with that.

More Detailed Measurements
Response Time setting = Normal

Having established that the normal OD setting offered the best response/overshoot balance we carried out our normal wider range of measurements as shown below.

The average G2G response time was more accurately measured at 7.6ms which was excellent for an IPS-type panel at 60Hz. Transitions were pretty stable across all the changes, whether they were changes from dark to light (rise times) or from light to dark (fall times). Some transitions did reach down to close to the specified 4ms G2G although a few were a bit slower at up to around 11ms.

There was some moderate levels of overshoot at this setting on a few transitions, but not any huge amounts. Most transitions showed little to no overshoot at all which was very pleasing, especially given the response times had clearly been pushed down to a low level for a 60Hz IPS-type panel. A decent result here.
 

Display Comparisons

The above comparison table and graph shows you the lowest, average and highest G2G response time measurement for each screen we have tested with our oscilloscope system. There is also a colour coded mark next to each screen in the table to indicate the RTC overshoot error, as the response time figure alone doesn't tell the whole story.

Overall the responsiveness of the XB271HK was very good for an IPS-type panel. It can't offer the fluidity and frame rates of a high refresh rate panel of course, but for a 60Hz IPS panel it was excellent. With a 7.6ms G2G average, and pretty low levels of overshoot it represented about as good as you could hope for from a 60Hz panel of this technology. Around 8.5ms G2G is the best we've seen with zero overshoot, so Acer had pushed this a little further. A small amount of overshoot had been introduced as a side effect but we felt it was at a low enough level that it didn't become distracting or noticeable in practice. The high refresh rate IPS panels like the Acer XB270HU, XB271HU and Asus ROG Swift PG279Q for instance can offer a step up though in terms of gaming experience. Their response times are pushed even lower at the higher refresh rates up to 144Hz, and combined with the higher refresh rate provide a smoother and more fluid gaming experience. You get the benefits of higher frame rates in FPS games on those high refresh rate models.

The benefit of the XB271HK though to some users will be the higher UltraHD resolution (3840 x 2160), pushing beyond the 2560 x 1440 res of those high refresh rate offerings. It provides a sharp and detailed image and many users love the "4k" gaming experience. Images look sharp and crisp even up close. One big consideration you need to make is that the 3840 x 2160 @ 60Hz resolution is likely to be a major drag on even high end graphics cards and PC systems when it comes to gaming. You really need to think about the type of game you want to play, the settings you want to use, and whether your system can handle outputting such a high resolution effectively. Thankfully the addition of NVIDIA G-sync allows for dynamic control over the refresh rate up to 60Hz, helping to eliminate tearing and stuttering and avoiding the need to use the lag-inducing V-sync option. So even those systems that can't manage the 3840 x 2160 @ 60Hz reliably should be better on a screen like this with variable refresh rate.

Your graphics card will also need to support DisplayPort 1.2 and preferably be an NVIDIA G-sync capable card given that's a big part of this screen (and cost). Other interfaces including the HDMI 1.4 inputs are limited to 30Hz at 3840 x 2160. Don't forget that many gaming titles don't support this 4k resolution either, so that could be another issue. Some games don't handle scaling very well and so when it comes to the user interface a lack of scaling results in tiny text or hard to read maps etc. Be wary of that as well as the game needs to handle scaling properly on a screen this size. One option of course is to run the game at a lower resolution and let the screen scale it. That's probably the most sensible option in most cases. It does kind of defeat the point of having a 4k resolution in the first place though. If you have games which can natively support this resolution properly, they would look fantastic given the very high resolution and high pixel density. External games consoles running at 1080p will still look ok, and the image is interpolated quite well.
 

The screen was also tested using the chase test in PixPerAn for the following display comparisons. As a reminder, a series of pictures are taken on the highest shutter speed and compared, with the best case example shown on the left, and worst case example on the right. This should only be used as a rough guide to comparative responsiveness but is handy for a comparison between different screens and technologies as well as a means to compare those screens we tested before the introduction of our oscilloscope method.

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 60Hz (OD = Normal)

In practice the Acer XB271HK performed best with the OD response time setting at normal. There were low levels of blurring evident, the image looked sharp and there was no noticeable overshoot detected. The screen lacked the fluidity and smoothness of a high refresh rate panel, but for a 60Hz IPS screen it was impressive. The additional G-sync support for NVIDIA users will also be of real benefit especially considering the system demands of the high Ultra HD resolution.

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 60Hz (OD = Normal)

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 144Hz (OD = Normal)

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 144Hz (OD = Normal)

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 144Hz (Trace Free = 80)

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 144Hz (overdrive = enhanced)

The above images compare the XB271HK then with the four high refresh rate IPS-type panels we've tested. In practice the high refresh rate IPS models show smooth and fluid movement and are also free of any noticeable overshoot as well which is pleasing. We know that those other screens have a slightly faster response time on the most part, but it's the higher refresh rate which really brings about the main benefits in gaming and perceived motion clarity, making them more suited to gaming than the XB271HK. That's not to say that the XB271HK is bad, it's not, it's just that it can't keep up with the high refresh rate panels which is logical anyway.

27" 4ms G2G AU Optronics AHVA (IPS-type) @ 60Hz (OD = Normal)

27" 1ms G2G AU Optronics TN Film @ 144Hz (Response Time = Normal)


27" 1ms G2G AU Optronics TN Film @ 144Hz (OD = Normal)

27" 1ms G2G AU Optronics TN Film @ 144Hz (AMA = High)

The above then compares the XB271HK with a few popular TN Film based gaming models, all with 2560 x 1440 resolution and 144Hz refresh rate. The TN Film models shown here are faster in terms of measured response times, and again their high refresh rate brings about obvious improvements in motion performance. There are moderate levels of overshoot on each of them though as a result of the aggressive overdrive impulse, with some dark trailing becoming noticeable in certain cases. TN Film panels also have a different "feel" than the IPS models in terms of snappiness and speed. Obviously these TN Film gaming screens offer a better overall gaming experience for various reasons than the XB271HK, but you are of course sacrificing in some of the all-round performance benefits of the XB271HK's IPS panel. You also miss out on the Ultra HD high resolution on those other panels, which after all is one of the key selling points of this Acer screen.

Additional Gaming Features

Lag

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) 4.00 Pixel Response Time Element 3.80 Estimated Signal Processing Lag 0.20 Lag Classification 1

Class 1

We have provided a comparison above against other models we have tested to give an indication between screens. The screens tested are split into two measurements which are based on our overall display lag tests (using SMTT) and half the average G2G response time, as measured by the oscilloscope. The response time is split from the overall display lag and shown on the graph as the green bar. From there, the signal processing (red bar) can be provided as a good estimation.

The screen showed a total lag of only 4.00ms. Approximately 3.80ms of that can be accounted for by pixel response times, leaving an estimated signal processing lag of only 0.20ms. This is basically nothing and means the screen should be fine for all levels of gaming. Other G-sync screens to date have shown similar very low levels of lag which is pleasing.

Movies and Video

The following summarises the screens performance in video applications:

• 27" screen size makes it a reasonable option for an all-in-one multimedia screen, much smaller than LCD TV's and many larger format desktop monitors which are now emerging.

• 16:9 aspect ratio is well suited to videos and movies, leaving you with smaller/no borders on DVD's and wide screen content at the top and bottom than on a 16:10 aspect display.

• 3840 x 2160 resolution can support full 1080 HD resolution content and also Ultra HD "4k" content natively.

• Digital DisplayPort interfaces support HDCP for any encrypted and protected content

• DisplayPort and HDMI connections available which is an improvement over older G-sync screens. The addition of HDMI is certainly welcome for connecting external devices and Blu-ray players.

• Cable provided in the box for DisplayPort only.

• Light AG coating provides clear images with no major graininess, and without the unwanted reflections of a glossy solution.

• Wide brightness range adjustment possible from the display, including high maximum luminance of ~264 cd/m² and a good minimum luminance of 33 cd/m². This should afford you very good control for different lighting conditions. Contrast ratio remains stable across the adjustment range as well and is good for a TN Film panel. Brightness regulation is controlled without the need for PWM and so is flicker free at all settings which is pleasing.

• Black depth and contrast ratio are good for an TN Film panel at 943:1 after calibration. Detail in darker scenes should not be lost as a result.

• There is a specific 'movie' preset mode available in the eColor menu although really it's just a preset brightness/contrast level. It was a little cooler than our calibrated user setup though.

• Very good pixel responsiveness which can handle fast moving scenes in movies without issue. Low overshoot when sticking to the 'normal' response time mode which is good.

• Wide viewing angles from IPS panel technology meaning several people could view the screen at once comfortable and from a whole host of different angles. Pale glow from an angle on black content may be problematic to some users and is common for IPS panel technology.

• No major backlight leakage on our sample which is good.

• Wide range of ergonomic adjustments available from the stand, allowing you to adjust the screen to suit varying viewing positions. All smooth and very easy to move which was pleasing.

• Basic 2x 2W integrated stereo speakers offered on this model for some basic sound support. Probably ok for the odd Youtube clip but not really for movie viewing. There is also a headphone port on the back.

• Hardware aspect ratio control provided with options for full, aspect and 1:1 pixel mapping which are very useful for connecting external devices.

• Picture By Picture (PbP) or Picture In Picture (PiP) are not available on this model.
  
   

Conclusion

The Acer XB271HK delivered a strong all round performance thanks to its IPS-type panel. One of the key selling points is the Ultra HD resolution of this panel, and that really helped deliver a sharp and crisp image thanks to its high PPI. The addition of NVIDIA G-sync meant that powering this resolution for games was less of a strain on your system and was a welcome feature for sure. The screen is aimed at gamers primarily as part of the Predator range and this was an area it did well in. It lacks the high refresh rate support of some modern screens, but you've (knowingly) traded that here for the high resolution. Response times were very good and input lag was non-existent which was excellent news for gamers. The screen is missing an ULMB blur reduction mode which is often paired with G-sync support since it does not have a high refresh rate.

In other areas the default setup was strong and we appreciated the flicker free backlight as well. The stand was versatile and offered smooth and easy adjustments, and although connectivity was limited because of the use of G-sync it was at least a v2 module with HDMI available. As ever you need to consider whether you want an Ultra HD resolution and have the necessary operating system and software to handle it well. If you do, then this is a strong all-rounder and good "4k" gaming option.

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