

Introduction

Every now and then, a new screen comes along which really excites us. Something new to test, or an interesting new technology or feature always keeps us interested when it comes to reviewing monitors. The Acer Predator XB270HU is one of those screens which really grabs our interest! It offers various World's first claims. It's the first 144Hz high refresh rate compatible IPS-type panel, offering something users have been wishing for. It is the first IPS panel to be paired with NVIDIA's G-sync dynamic refresh rate and ULMB (Ultra Low Motion Blur) technologies. This in itself represents the first time an IPS panel has been provided with a blur reduction mode. Early hype for this screen has been huge since it was announced in January 2015 for CES that it would be the first 144Hz IPS screen on the market. It's not expected to be widely available until mid-April, but we are fortunate to have the first available final sample of this screen with us for an exclusive first review. We know you're all dying to know if this is the ultimate gaming screen, as are we!

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Specifications and Features

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

Monitor Specifications Size 27"WS (69 cm) Panel Coating Light AG coating Aspect Ratio 16:9 Interfaces 1x DisplayPort (version 1.2) Resolution 2560 x 1440 Pixel Pitch 0.233 mm Design colour Glossy black bezel and stand, some red trim on base Response Time 4ms G2G Ergonomics Tilt, 150mm height, swivel and rotate Static Contrast Ratio 1000:1 Dynamic Contrast Ratio n/a VESA Compatible Yes 100mm Brightness 350 cd/m2 Accessories Power, DisplayPort, USB cables Viewing Angles 178 / 178 Panel Technology AU Optronics AHVA (IPS-type) Weight net: 7.0Kg Backlight Technology W-LED Physical Dimensions (WxHxD)

624 x 401 - 511 x 245mm Colour Depth 16.78m (8-bit) Refresh Rate 144Hz Special Features 4x USB 3.0 ports (1 with charging capability), ULMB, G-sync Colour Gamut Standard gamut

~sRGB, ~72% NTSC

The XB270HU offers a limited range of connectivity options with only DisplayPort provided. This is for good reason though as it is the only interface supported for the high bandwidth needed to drive the 2560 x 1440 resolution at up to 144Hz, and also allowing support for NVIDIA G-sync technology. The DisplayPort interface is HDCP certified for encrypted content and the video cable is also provided in the box.



Above: Acer XB270HU boxed up. Click for larger version

The screen has an internal power supply but comes packaged with the power cable you need. There are also 4x USB 3.0 ports, 2 located on the bottom edge of the back section next to the video and power connections and 2 on the left hand side of the screen. The top of the two on the side has charging capabilities as well. There are no additional extras such as integrated speakers, 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:

Feature Yes / No Feature Yes / No Tilt adjust DVI Height adjust HDMI Swivel adjust D-sub Rotate adjust DisplayPort VESA compliant Component USB 2.0 Ports Composite USB 3.0 Ports Audio connection Card Reader HDCP Support Ambient Light Sensor MHL Support Human Motion Sensor Integrated Speakers Touch Screen PiP / PbP Factory Calibration Blur Reduction Mode Hardware calibration G-Sync Uniformity correction FreeSync





Design and Ergonomics

Above: front views of the screen. Click for larger versions

Above: front views of the screen. Click for larger versions The XB270HU comes in an all black design with glossy plastics used for the bezel and base. There is an orangey-red trim at the bottom of the stand as you can see from the photos as well. This follows in the footsteps of the very successful and popular Asus ROG Swift PG278Q which has a light-up red ring around the base, and the overall design here is fairly similar. The bezel is thin and measures ~11mm around the sides and top, and ~18.5mm along the slightly thicker bottom edge. There is a matte silver coloured Acer logo in the middle of the bottom bezel and an "XB270HU" model designation in the top right hand corner.

Above: rear view of the screen. Click for larger version The back of the screen is finished in a matte black plastic as shown above. There is a useful cable tidy hole in the back of the stand. The stand is also easily detached via a button and the screen can be VESA mounted (100 x 100mm) if required. The base of the stand is circular in shape and is a glossy black plastic with red circular trim. It measures ~245mm width and provides a pretty sturdy base for the screen. There is a full range of ergonomic adjustments offered from the stand as well which is great to see.

Above: full range of tilt adjustment shown. Click for larger versions The tilt function is smooth but a little stiff to move, but it does offer a wide range of angles to choose from as shown above.

Above: full range of height adjustment shown. Click for larger versions Height adjustment is a easier to move and is smooth, offering a very good range of adjustment again. At the lowest height setting the bottom edge of the screen is approximately 30mm from the edge of the desk. At the maximum setting it is ~180mm, and so there is a 150 mm total adjustment range available here. Side to side swivel has a smooth movement but it is very stiff to operate.

Above: rotated view of the screen. Click for larger version The rotate function is a stiff but quite smooth to move if you want to switch into portrait mode. Overall when making adjustments to your viewing angle and position the screen has some low levels of wobble. It is fairly sturdy though during normal uses on the desk. A summary of the screens ergonomic adjustments is shown below: Function Range Smoothness Ease of Use Tilt Yes Smooth A little stiff Height 150mm Smooth Easy Swivel Yes Smooth Very stiff Rotate Yes Quite Smooth Stiff Overall Good range of adjustments and easy enough to use overall. Good tilt and height ranges. The materials were of a good standard and the build quality felt good as well. It felt more premium than some more basic Acer office range models we had seen in the past and we were pleased. There was no audible noise from the screen, even when conducting specific tests which can often identify buzzing issues. The whole screen remained very cool even during prolonged use as well which was pleasing.

Above: rear views of the screen showing connections. The back of the screen provides a connection for the power cable which is provided with the screen. There is then a single DisplayPort video connection, USB upstream and 2x USB 3.0 downstream on the back of the screen.

Above: side of the screen showing additional 2x USB 3.0 connection. Click for larger version Two additional easy-access USB port are available on the left hand side of the screen which is nice to see. The top of these two also has charging capabilities. You can also set in the OSD menu whether the charging port can function when the screen is off.





OSD Menu



Above: OSD control buttons on the bottom right hand edge

The OSD menu is accessed and controlled through a series of 5 pressable buttons located on the front bezel in the bottom right hand corner. They are pretty hard to see during normal screen use as they blend nicely into the bezel of the screen. A blue power LED is located next to them and to the right is an on/off power button. This also glows amber when the screen is on standby. The light from the power LED does spill out a little under the two buttons it is adjacent to, but nothing serious, just a minor build quality quibble.

Pressing any of the buttons brings up the above quick access menu. You have 4 quick access options available which we will show you next. The far right option brings up the main OSD menu.

The first quick access is to the eColor Management menu, basically a series of 5 preset modes which we will test later on as well.

The second button gives you quick access to the brightness control slider. One gripe is that this is very slow to move between settings, even when holding the button for up/down. This is the same for any slider, so anything with a lot of adjustments between 0 - 100 it is a bit cumbersome to use.

The third button gives you quick access to the overdrive (OD) option, with 3 settings available. We will again test those later on in the review.

The fourth button gives you access to the ULMB setting with options for on or off available from the quick access menu. A further setting is available for Pulse Width from within the main OSD menu.

Pressing the main OSD menu button brings up the display above. This is split in to 4 sections down the left hand side, with the options available in each shown on the right hand side. The software was quick to navigate and looked nice we thought. In the first 'picture' section of the menu there are options to access the eColor preset modes, change brightness, contrast, gamma and colour temp modes as well. Plenty to play around with for calibration.

The second section just allows you to control the OSD software itself.

The 'settings' section has a few more useful features. You can change the OD control again here if you want to, and the ULMB feature. You can also choose whether the charging USB port will charge devices when the screen is powered off.

The 'refresh rate bar' setting controls a thin red line shown in the bottom left hand corner of the screen as shown above. This can either be 4 or 8 pixels wide (or off) and shows your current refresh rate setting as varying heights of the line. It's designed to give you a visual indication of your refresh rate when using G-sync dynamic refresh rate control really. A nice idea, and at only a few pixels wide it's not obtrusive.

The final 'information' section just confirms your resolution, refresh rate and OD mode.

There is a factory menu available as well which confirms a few useful bits of information, including the panel being used here. You can also adjust the OD setting value and RGB levels for the warm, normal and cool preset modes. We won't mess around with those in this review but might have a look at them later on.

All in all we liked the design and layout of the OSD menu. There were a fair few options to play with as well which was good. Navigation was mostly pretty easy although sometimes it was a little confusing how far you'd drilled in to any given option. The speed of changing a setting (e.g. brightness between 0 - 100) can be cumbersome too.



Power Consumption

In terms of power consumption the manufacturer lists typical usage of 35.0W and 0.45W in standby. We carried out our normal tests to establish its power consumption ourselves.

State and Brightness Setting Manufacturer Spec (W) Measured Power Usage (W) Default (100%) 35.0 44.3 Calibrated (24%) - 25.8 Maximum Brightness (100%) - 44.3 Minimum Brightness (0%) - 19.6 Standby 0.45 0.6

We tested this ourselves and found that out of the box the screen used 44.3W at the default 100% brightness setting. Once calibrated the screen reached 25.8W consumption, and in standby it used only 0.6W. We have plotted these results below compared with other screens we have tested. The consumption is comparable actually to the other W-LED backlit displays we have tested, with GB-r-LED backlit displays (e.g. Dell U2713H) using a bit more than most W-LED backlights.





Panel and Backlighting

Panel Manufacturer AU Optronics Colour Palette 16.7 million Panel Technology AHVA (IPS-type) Colour Depth 8-bit Panel Module M270DAN02.3 Colour space Standard gamut Backlighting Type W-LED Colour space coverage (%) ~sRGB, ~72% NTSC

Panel Part and Colour Depth

The Acer XB270HU features an AU Optronics M270DAN02.3 AHVA (IPS-type) panel which is capable of producing 16.78 million colours. The panel offers an 8-bit colour depth and the part is confirmed when accessing the factory OSD menu as shown below. 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 A M VA (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.

Screen Coating

The screen coating on the XB270HU 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, including that on the Asus ROG Swift PG278Q screen. 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 has become very popular 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 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 = 5ms

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.

Pulse Width Modulation Used No Cycling Frequency n/a Possible Flicker at 100% Brightness No 50% Brightness No 0% Brightness No

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



Contrast Stability and Brightness

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

OSD Brightness Luminance

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

( x:1) 100 326.60 0.31 1054 90 303.58 0.29 1047 80 282.15 0.27 1045 70 259.17 0.25 1037 60 235.26 0.23 1023 50 209.91 0.20 1050 40 182.29 0.18 1013 30 153.39 0.15 1023 20 121.96 0.12 1016 10 88.78 0.09 986 0 52.93 0.05 1059

Total Luminance Adjustment Range (cd/m2) 273.67 Brightness OSD setting controls backlight? Total Black Point Adjustment Range (cd/m2) 0.26 Average Static Contrast Ratio 1032:1 PWM Free? Recommended OSD setting for 120 cd/m2 20

The brightness control gave us a very good range of adjustment. At the top end the maximum luminance reached 326.6 cd/m2 which was high, although slightly lower than the specified maximum brightness of 350 cd/m2 from the manufacturer. There was a decent 273.67 cd/m2 adjustment range in total, and so at the minimum setting you could reach down to a low luminance of 52.93 cd/m2. This should be more than adequate for those wanting to work in darkened room conditions with low ambient light. A setting of 20 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 not quite a linear relationship as the brightness adjustments between settings of 50 and 0 controls a slightly steeper luminance range than settings between 100 and 50.

The average contrast ratio of the screen was excellent for an IPS-type panel with an average of 1032:1. This was nice and stable across the brightness adjustment range as shown above.





Testing Methodology

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

We restored our graphics card to default settings and disabled any previously active ICC profiles and gamma corrections. The screen was tested at default factory settings using the DisplayPort interface, and analysed using an X-rite i1 Pro Spectrophotometer (not to be confused with the i1 Display Pro colorimeter) 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 spectrophotometer is less reliable at the darker end.



Targets for these tests are as follows:

CIE Diagram - validates the colour space covered by the monitors backlighting in a 2D view, with the black triangle representing the displays gamut, and other reference colour spaces shown for comparison

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

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

Luminance - we aim for 120 cd/m 2 , which is the recommended luminance for LCD monitors in normal lighting conditions

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

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

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





Default Performance and Setup

Default settings of the screen were as follows:

Monitor OSD Option Default Settings Preset mode (eColor mode) Standard Brightness 100 Contrast 50 Gamma 2.2 Colour Temp Warm RGB m/a



Acer XB270HU - Default Settings









Default Settings luminance (cd/m2) 336 Black Point (cd/m2) 0.32 Contrast Ratio 1054:1

Initially out of the box the screen was set in the default 'standard' eColor preset mode. Gamma mode was set at 2.2, and colour temperature on warm. The screen was extremely bright as it was set at a default 100% brightness setting. Colour balance and temperature felt good although a little cool, and you could tell it was a standard gamut screen. We went ahead and measured the default state with the i1 Pro.

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 minor over-coverage in all shades but not by anything significant. Default gamma was recorded at 2.4 average, leaving it with a 9% deviance from the target which was a little off. White point was measured at 6883k being a bit too cool from the target of 6500k but with a fairly low 6% deviance.

Luminance was recorded at a very bright 336 cd/m2 which is too high for prolonged general use. The screen was set at a default 100% 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 0.32 cd/m2 at this default brightness setting, giving us an excellent (for an IPS-type panel) static contrast ratio of 1054:1. Colour accuracy was very good out of the box with a default dE average of 1.9, and a maximum of only 3.0. Testing the screen with various gradients showed smooth transitions with no sign of any banding thankfully. There was some gradation evident as you will see from most monitors in darker tones. Overall the default setup was reasonably good, although some corrections are needed to the gamma and white point. There are options for both in the OSD so we will see if it's possible to get a better default setup through some basic OSD changes.



eColor Management

We tested the eColor Management options as well which are a range of fairly basic preset modes. The default 'standard' mode was tested above in the previous section. Switching to the 'User' eColor mode made no changes to the OSD settings other than to alter the brightness control down from 100 to 77 by default. As a result, there was no change to the default setup other than a lower luminance of 284 cd/m2. In the 'User' mode you can alter the brightness and other settings to your liking.

Same thing with the 'ECO' eColor mode which just reduced the brightness setting to a locked 44. If you change this, you revert to the 'User' mode. At this 44 brightness setting the ECO mode gave a luminance of 199 cd/m2. Again, the rest of the setup remained unchanged.



Setup in Graphics eColor preset mode





When you switch to the 'Graphics' eColor mode the brightness is locked this time at 97, although the contrast setting has been moved away from it's default of 50, to 60. As a result the setup is impacted in several ways. The gamma has moved closer to the desired 2.2 level, now showing a lower 5% deviance from the target. Colour temperature was a little cooler than before (7% out), but the most obvious change came in the colour accuracy. dE average had now increased to 3.8, and a maximum of 13.6. For colour critical and graphics work you would be better settings up the 'User' mode to a more accurate level (see following sections).

Setup in Movie eColor preset mode





The 'Movie' eColor mode showed a better setup though. In this mode the brightness setting is locked at 77, and contrast has been altered to 56. Gamma at this setting was now very close to the target with only a 1% deviance. Colour temperature remained too cool as before, but dE had improved back down to 2.1 average. There was some fairly large error in some colours, where dE maximum was 6.7.

The eColor modes are basically a series of preset brightness and contrast modes where those two settings are locked in each mode. If you change either of them you just are automatically switched to the 'user' mode. Thankfully you can alter the gamma and colour temperature mode in each, so you could in theory set them up for different uses. It's a shame though that you can't define your own brightness setting for each, as really they are all too bright for comfortable prolonged use. The ECO mode (capped at 44 brightness and therefore 199 cd/m2) is perhaps useable in certain circumstances. Most people will probably just want to set up the 'User' mode to their liking we would think.



Gamma and Colour Temperature

The XB270HU features a range of 3 defined 'colour temp' modes along with a user configurable mode within the OSD menu as shown in the above screen shots (4 modes total). There are also 4 pre-defined gamma modes available to choose from. We measured the screen with the X-rite i1 Pro spectrophotometer in each of these modes to establish their colour temperature / white point. We also tested the average gamma in each mode, while colour temperature was left at the default 'warm' setting. All other settings were left at factory defaults and no ICC profile was active. The results are recorded below:

Gamma Setting

Gamma Mode Average Gamma Deviance from 2.2 Gamma 1.9 2.1 6% 2.2 2.4 9% 2.5 2.7 22% Gaming 3.0 35%

Colour Temp Setting

Color Temp Mode Measured White point (k) Normal 7823 Warm 6883 Cool 9688 User 6883

The default gamma mode of 2.2 delivered a gamma which was a bit too high, measured at an average of 2.4 and with 9% deviance. The 1.9 setting was a little closer (6%) deviance but now too low. The 2.5 and gaming modes pushed the gamma average even higher still. Certainly beyond anything we'd want to use for desktop or day to day use, but actually the gaming mode might be useful to some people who find themselves increasing the gamma in games.

The colour temp modes were a little off. We would have liked to have seen the 'normal' mode close to 6500k, when in fact the 'warm' mode was closest at 6883k, being still a little too cool. The 'normal' mode was much cooler at 7823k, and 'cool' was even more so at 9688k. Thankfully there is a 'user' mode where you can alter the RGB levels yourself to achieve your desired white point. By default it is the same as the 'normal' mode incidentally.



Optimum OSD Adjustments

Having tested the various brightness, eColor, gamma and colour temp modes we thought it would be useful to summarise what we would consider to be the optimum OSD adjustments out of the box, before any calibration device is used to profile the screen. These are designed to help you reach a more comfortable and reliable setup without the need for a calibration tool. In the following section we will calibrate the screen properly and provide a calibrated ICC profile for those who would like to try it.

Monitor OSD Option Recommended Optimum Settings eColor mode User Brightness 24 Contrast 50 Gamma 2.2 Colour Temp User RGB 50, 45, 46



Acer XB270HU - Optimum OSD settings





Optimum OSD Settings luminance (cd/m2) 120 Black Point (cd/m2) 0.13 Contrast Ratio 936:1

We changed to the 'user' eColor mode which allowed us to make alterations to all of the OSD settings. Gamma we stuck with 2.2 as it looked better to the naked eye and made it easier to obtain a reliable white point through the adjustment of the RGB levels. For this we had to change to the 'user' color temp mode, which then gave us access to the RGB controls. Through those adjustments we managed to achieve a better white point at 6479k (0% deviance) basically spot on to the 6500k target. An adjustment to the brightness setting achieved a far more comfortable luminance and we still maintained a nice high contrast ratio of 936:1. The reason for the slight drop in contrast ratio is the adjustment to the RGB channels to correct the white point. The gamma curve was still a little off from the target, measured at 2.4 average (7% out) but the rest of the setup was pretty good. Colour accuracy remained decent with dE average of 2.7, although some higher errors where dE reached up to 7.2 were detected. These settings do represent a decent setup for your average user though and it's very easy to achieve these results through just some simple OSD changes as we've shown.

Calibration

We used the X-rite i1 Pro 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.

Monitor OSD Option Calibrated Settings eColor mode User Brightness 24 Contrast 50 Gamma 2.2 Colour Temp User RGB 50, 45, 46



Acer XB270HU - Calibrated Settings





Calibrated Settings luminance (cd/m2) 121 Black Point (cd/m2) 0.12 Contrast Ratio 1000:1

We stuck with the 'user' preset mode first of all which would give us access to the RGB channels, as well as the brightness and contrast settings which are available in all the modes. All these OSD changes 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. After this we let the software carry out the LUT adjustments and create an ICC profile.

Average gamma was now corrected to 2.2 average, correcting the 7 - 9% deviance we'd seen out of the box, depending on the OSD settings used. The white point had already been corrected nicely in the previous section through adjustments to the OSD RGB levels. It was maintained at an accurate level, measured at 6522k (0% deviance). Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at 121 cd/m2. This left us a black depth of 0.12 cd/m2 and maintained an excellent static contrast ratio (for an IPS-type panel) of 1000:1 - spot on to the spec in fact! Colour accuracy of the resulting profile was excellent, with dE average of 0.4 and maximum of 1.0. LaCie would consider colour fidelity to be very good overall. Testing the screen with various colour gradients showed mostly smooth transitions. There was some slight gradation in darker tones but no banding introduced due to the adjustments to the graphics card LUT from the profilation of the screen which was pleasing. 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 fairly good although there were a couple of issues. The gamma was a little high at 2.4 average (9% deviance), and white point was a bit too cool at 6883k (6% deviance). We were pleased though with the low dE (1.9 average) and strong contrast ratio (1054:1). Brightness of course needed to be turned down from the maximum 100, but doing so does not impact other aspects of the setup here so we won't worry about that. It is possible to improve things through some basic OSD changes as covered in the relevant section of this review. The Asus ROG Swift PG278Q had a more accurate default setup it should be noted (0% deviance in gamma and white point), although being TN Film technology it didn't offer the image quality and viewing angles that the XB270HU's IPS-type panel can deliver.

The display was strong when it came to black depth and contrast ratio for an IPS-type panel. With a calibrated contrast ratio of 1000:1 it was comparable to some of the better screens using this kind of panel technology. It was not quite as high as the recently tested Dell U2515H (1138:1) which holds the record for an IPS contrast ratio. It did out perform the Asus ROG Swift PG278Q with its TN Film panel only reaching 858:1. Of course it can't compete with VA panel types which can reach over 2000:1 easily, and commonly up to 3000:1, even close to 5000:1 in the case of the Eizo FG2421.

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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 XB270HU 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 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. All as expected really from a modern IPS panel. This is one of the key areas which separates the XB270HU from other gaming screens in the market which are nearly all TN Film based. TN Film has long been the panel choice for gaming screens thanks to its response times, but users have had to sacrifice in viewing angles and image stability as a result. That's no longer the case with the arrival of high refresh rate gaming IPS panels thankfully.



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 panels and can be distracting to some users. If you view dark content from a normal head-on viewing position, you can actually see this glow as your eyes look towards the edges of the screen if the screen is of a large size. This could be distracting if you work with a lot of dark content. The IPS glow was normal here for a modern IPS-type panel. While the general viewing angles of IPS technology are better than TN Film, this IPS glow is one area where they are not as well off.





Panel Uniformity

We wanted to test here how uniform the brightness and colour temperature was across the screen, as well as identify any leakage from the backlight in dark lighting conditions. Measurements of the luminance and colour temperature 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. Measurements for colour temperature (white point) were taken using BasICColor software and the i1 Pro spectrophotometer which can more accurately measure the white point of different backlighting technologies. 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 moderate. The top and left hand edges did seem to drop down in luminance somewhat, ranging down to 99 cd/m2 in the most extreme cases in the central upper area. The lower and central regions of the screen were a bit more uniform. Around 60% of the screen was within a 10% deviance from the centrally calibrated point which was ok.



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 in the right hand corners. It was not too bad though, not easy to pick out with the naked eye, and should not present any major problems in normal use.



General and Office Applications

The XB270HU feature a large 2560 x 1440 WQHD resolution which is only just a little bit less vertically than a 30" screen. The pixel pitch of 0.233 mm is quite small as a result, and by comparison a standard 16:10 format 24" model has a pixel pitch of 0.270mm and a 30" model has 0.250mm. These ultra-high resolution 27" models offer a tight pixel pitch and therefore small text as well. We found it quite a change originally coming from 21.5 - 24" sized screens back in the day, even those offering quite high resolutions and small pixel pitches. Although now we are very used to working with 27" 1440p screens all the time and find them very comfortable and a significant upgrade over 1080 / 1200p models. Some users may find the small text a little too small to read comfortably, and we'd advise caution if you are coming from a 19" or 22" screen for instance where the pixel pitch and text are much larger. The extra screen size takes some getting used to over a few days as there really is a lot of room to work with but once you do, it's excellent. For those wanting a high resolution for CAD, design, photo work etc, this is a really good option. The image was very sharp and crisp and text was very clear. With its WQHD display, you enjoy 77% more desktop space than a full HD screen to spread out your windows and palettes.

The thin bezel design mean that the XB270HU could be easily integrated into a multi-screen set up if you wanted. It doesn't have a 'frameless' design like some modern screens, but it's certainly not a thick bezel. The light AG coating of the modern AHVA (IPS-type) panel is certainly welcome, and much better than the older 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 pretty decent, offering a strong contrast ratio and low dE. Ideally you will want to calibrate the screen with a colorimeter to correct the gamma curve, but even without we thought the image looked decent enough for day to day office work. A few simple OSD changes can help you adjust the colour temperature as well to get a warmer setting, or something closer to 6500k at least.

The brightness range of the screen was also very good, with the ability to offer a luminance between 327 and 53 cd/m2. This should mean the screen is perfectly useable in a wide variety of ambient light conditions, including darkened rooms. A setting of ~20 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. One minor gripe is that the brightness control in the OSD menu is really slow to move, so if you are adjusting across a wide range it can take a while.

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 fairly cool even during prolonged use. There is no specific preset mode for office work or reading. The eColor preset modes are locked at certain brightness levels as well, so aren't really suitable for general office/text work. You'd be best off using the 'user' mode and adjusting the brightness control to suit your requirements and ambient light conditions. There is only 1x DisplayPort connection here so connectivity is limited for some older systems. It's designed primarily for gaming and G-sync limitations call for just the single DisplayPort connection at the moment. The screen offers 4x USB 3.0 ports which can be useful and it was nice to keep this up to date with the modern version. Here, 2 of them are on the underside back with the video connections, and 2 are on the left hand side of the screen for easy access. One of those on the left hand side can be used for charging as well which is handy.

There are no further extras like ambient light sensors or card readers which can be useful in office environments. Remember, this is aimed at gamers really. There was a great range of ergonomic adjustments available from the stand allowing you to obtain a comfortable position for a wide variety of angles. The VESA mounting support may also be useful to some people as well.



Above: photo of text at 2560 x 1440 (top) and 1920 x 1080 (bottom)

The screen is designed to run at its native resolution of 2560 x 1440 and at a 60Hz recommended refresh rate. However, if you want you are able to run the screen outside of this resolution. We tested the screen at a lower 1920 x 1080 resolution to see how the screen handles the interpolation of the resolution, while maintaining the same aspect ratio of 16:9. At native resolution the text was very sharp and clear. When running at a 1080p resolution the text is still reasonably clear, with moderate levels of blurring. You do lose some screen real-estate as well of course but the image seems to be interpolated quite well from 1080p sources.



Gaming Introduction

The Acer XB270HU is very exciting when it comes to gaming for various reasons. Firstly, this is the first IPS-type panel on the market to natively support refresh rates up to 144Hz. Some Korean model IPS screens have been "overclockable" up to 100 - 120Hz or so over the last couple of years, but results vary a lot and it's by no means a native support from a panel level. Furthermore, from what we've seen of Korean screens the response times never seem to be up to much and don't reach low enough levels that make the screen practical for the frame rate demands that the high refresh rate has. A lot of blurring and ghosting is common on those models as a result. We will test in the following sections how the pixel response times are, but the first thing to note is that this panel is designed to operate with the high refresh rate natively. Secondly, this is the first IPS-type panel to support NVIDIA's G-sync dynamic refresh rate technology. We already know that this is an extremely effective alternative to Vsync methods and adds a significant performance advantage when used in games with variable frame rates and on systems of differing capabilities. Thirdly, this is the first IPS-type panel to feature any kind of blur reduction mode at all. This comes in the form of the Ultra Low Motion Blur (ULMB) feature which is linked to the G-sync module. It should be noted that despite the high refresh rate support, the XB270HU does not support NVIDIA 3D Vision - we tested it just in case but it doesn't detect the display as a compatible screen.

IPS-type panel technology Native high refresh rate support G-sync support Ultra Low Motion Blur (ULMB) NVIDIA 3D Vision

To make the most of the Acer XB270HU you will want a suitable NVIDIA graphics card. The screen is designed in conjunction with NVIDIA and certain features including G-sync and the Ultra Low Motion Blur (ULMB) mode only work with NVIDIA GPU's. You will need a graphics card from their range which supports G-sync, from the list provided on NVIDIA's website. You will also need to ensure that the graphics card has a DisplayPort output since the screen only has a single DisplayPort input. A lot of NVIDIA's graphics cards seem to omit this connection type (as it's more of an AMD connection), but some versions of their compatible cards do offer it. You can't unfortunately use regular and widely available DVI to DisplayPort adapters as they don't work when taking DVI output from the graphics card to DP input in the monitor. There may be some "active" adapters which could overcome this, but that might be hit and miss. Ensuring you have a suitable NVIDIA card with DP out will make life much easier. If you have an older NVIDIA card with DP output which does not support G-sync, you can still run the screen as normal. You would be able to achieve the 144Hz refresh rate but you wouldn't be able to use G-sync or ULMB which are linked to one another and only available on the more modern G-sync supporting cards. On another note, you might find different DisplayPort cables give you different results. Some we had lying around our lab didn't seem to work very well, but you can just use the bundled cable anyway which should be fine.

It should be noted that the screen can also be used from AMD graphics cards, again as long as you have a DisplayPort output. We didn't have any issues with achieving the maximum refresh rate on one of our test machines (AMD 7800 series). We'd had problems reaching 120 / 144Hz when we tested the Asus ROG Swift PG278Q from the same graphics card, but no problems here on the Acer. Results may vary from one setup to another. Again, you'd probably have an NVIDIA card anyway if you were going to buy this screen since a lot of what you're paying for is the G-sync / ULMB features. Some users might still want to buy the screen to run on AMD systems, since after all it is still the World's first 144Hz compatible IPS-type panel. For optimum usage you want to be pairing it with an NVIDIA G-sync card though.

We expect if you're looking at such a high end gaming display that you will also have a pretty high end gaming PC to run it, so 2560 x 1440 at 144Hz would of course be preferable over anything else. You will see from our forthcoming response time tests that the increased refresh rate has a positive impact on response times as long as you stick to the 'normal' OD setting. What we are trying to say here is that we hope you have a system powerful enough to run this screen at its intended 2560 x 1440 resolution and 144Hz refresh rate, as really that's where you will get the optimum performance. You do need to consider the power of your graphics card though as there will be a big demand on your system for gaming at these kind of settings. Fortunately though there is also the new NVIDIA G-sync technology which will offer you smooth gaming even at lower frame rate outputs. Read on for more information.





Responsiveness and Gaming

Quoted G2G Response Time 4ms G2G Quoted ISO Response Time n/a Panel Manufacturer and Technology AU Optronics Panel Part M270DAN02.3 Overdrive Used Yes Overdrive Control Available to User 'OD' Overdrive Settings Off, Normal, Extreme

The XB270HU 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' (Overdrive) option. The part being used is the AU Optronics M270DAN02.3 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 XB270HU comes with a user control for the overdrive impulse available within the OSD menu in the 'settings' section as shown above (top), using the 'OD' option. You can also access it via one of the quick access menus (bottom). There are 3 options available here in the menu, for off, normal and extreme modes.

First of all we carried out a smaller sample set of measurements in all three of the OD response time settings. These, along with various motion tests allowed us to quickly identify which was the optimum overdrive setting for this screen. For completeness we tested the response times in each of these OD modes at various refresh rates, ranging from a normal 60Hz, up to the maximum 144Hz. This allowed us to establish if there were any differences in response time behaviour at each refresh rate as well.

OD (Overdrive) Setting = Off 60Hz 120Hz 144Hz

With OD set first of all to 'off' the response time behaviour was basically the same no matter what refresh rate was used. The average G2G response time was a modest ~11ms which actually put it only slightly behind some of the other IPS-type 27" models we have tested like the Dell U2715H (9.9ms) and BenQ GW2765HT (10.1ms), even when those were set to their optimum overdrive setting. Considering this was the lowest OD setting this seems to bode well for the response times of this panel. Rise times were slower than fall times, but neither showed any overshoot at all.

OD (Overdrive) Setting = Normal 60Hz 120Hz 144Hz

Moving the OD control up to 'Normal' we saw some obvious improvements to the response times. At 60Hz refresh rate the average G2G response time had reduced to 8.7ms, putting it on par with the best IPS-type panels we've seen to date where overshoot was not a problem (models like the Dell U2415 = 8.6ms). There was no overshoot at all detected either on this model so this was very pleasing.

It's when you switch the refresh rate up that the magic starts to happen! At 120Hz, the response times speed up quite significantly, with an average G2G now measured at 6.3ms. Bumping the refresh rate up to 144Hz pushes the response times even more, down now to 5.9ms G2G which is amazing for an IPS-type panel! It seems that the refresh rate has an impact on the overdrive impulse, pushing the response times down as you increase the refresh rate. This is more clear in the following section where we test the 'Extreme' OD setting, but you can see a very minor amount of overshoot starts to appear in the 'Normal' mode when you reach 144Hz. Nothing at all which you would see in practice, so we would consider OD Normal and 144Hz to be an excellent setting for response times. AU Optronics and Acer have obviously done a great job with the panel and monitor overdrive circuit.

With high refresh rates it it important that the response times can keep up with the demands of the frame rate. At 60Hz a new frame is sent to the screen every 16.6ms, at 120Hz every 8.33ms, and at 144Hz every 6.94ms. The response times need to be at least as fast as this to keep up, and thankfully they are on this screen. A truly impressive result for an IPS-type panel. If you're using G-sync then the refresh rate will be controlled dynamically depending on your gaming content and frame rate output from the graphics card. The overdrive impulse will be controlled dynamically at the same time, and pixel response times will range between 8.7 and 5.9ms G2G (60 - 144Hz) as a result, being more than capable of handling the frame rate at whatever refresh rate is running.

OD (Overdrive) Setting = Extreme 60Hz 120Hz 144Hz

Pushing the OD control up to the maximum 'Extreme' setting brought about some further changes in pixel response time behaviour. It also more clearly demonstrated what is happening to response times when you increase the refresh rate. At 60Hz the G2G average has been reduced from 8.7ms down to 7.0ms although some overshoot has now been introduced at pretty high levels. When you increase the refresh rate to 120Hz, and then to 144Hz you see a further drop in response times like we had seen in the 'Normal' OD mode. However, the overshoot becomes far more problematic and reaches ridiculous levels by the time you're running at 144Hz. For example the 0-50 transition has an overshoot of 21.2% at 60Hz, growing to 85% at 120Hz and then a whopping 111% at 144Hz. This demonstrates that the overdrive impulse is affected by the refresh rate of the screen, helping to speed up response times, but at the same time causing more overshoot in this mode. As a result of the high overshoot we wouldn't recommend using the 'Extreme' mode. Stick with 'Normal' where the response times are excellent for an IPS-type panel, and there's no overshoot at any refresh rate.



Overshoot Comparison at Different Refresh Rates (OD = Extreme)

If we compare the same 0-50-0 transition response time graph at each of the three refresh rate settings you can get a clearer view of what is happening. All 3 below are at the same scale, and the only thing changed each time was the Windows refresh rate.



Transition: 0-50-0 (scale = 20ms), refresh rate 60Hz

We have annotated this graph to help explain a little more clearly. At 60Hz refresh rate the upward curve is not as steep, showing it is a little slower to reach the desired luminance and which equates to the rise time measured of 8.6ms. There is a small overshoot where the brightness exceeds the target (21.2%) before dropping back down to the desired level, represented by the top flat line. The fall time is then measured at 5.9ms and that curve is steeper than the rise time as a result.



Transition: 0-50-0 (scale = 20ms), refresh rate 120Hz

When switching up to 120Hz there are a couple of obvious changes. The rise time is now quicker, measured at only 3.4ms now and represented by the steeper upward curve of the graph compared with before. However, the overshoot is significantly more, measured here at 85% and shown by the much higher peak.



Transition: 0-50-0 (scale = 20ms), refresh rate 144Hz

Again changing up to 144Hz maximum refresh rate brings about some changes. The upwards curve is steeper still, and we measured a 2.6ms rise time. The overshoot has grown again though, this time to 111.0% which is massive!



Click for larger version

If we take some test photos using the PixPerAn tool you can make some further visual comparisons between the overdrive settings and refresh rates. With OD set to off, there were consistent levels of blur to the moving image, regardless of the refresh rate setting. This matched up with what we'd measured with our oscilloscope as well. When you move to the 'normal' OD setting you see a marked improvement in response times, even at a basic 60Hz refresh rate. The blurring has been reduced nicely and the moving image appears sharper. This improves as you switch up to 120Hz and then 144Hz, with the image becoming clearer as the above photos capture. Not only are you getting a huge improvement in frame rate and smoothness brought about by the higher refresh rate, but you are getting improvements to the pixel response times as well. At the 'extreme' setting you can see some dark trailing in the 60Hz mode, but actually nothing too major. When you move up to 120Hz and then 144Hz, there is some pale trailing introduced as well and the overshoot is at very high levels. To reiterate, we would recommend sticking with normal OD setting.



More Detailed Measurements

OD = Normal and 144Hz refresh rate

Having established that the OD 'normal' mode offered the best response/overshoot balance we carried out our normal wider range of measurements as shown below. Tests were completed at the maximum 144Hz refresh rate.

The average G2G response time was more accurately measured at 5.5ms which was excellent overall, especially for an IPS-type panel. Rise times and fall times were very similar on average so so transitions were fairly consistent across the board. This was a very pleasing result and we were very impressed.

There was some very minor overshoot on some transitions but nothing at all to worry about. Considering how low the response times were driven on this IPS-type panel we were amazed that there was no overshoot to speak of as long as you stick to this 'normal' OD mode. The higher 'extreme' setting had far more noticeable overshoot, especially at the higher refresh rates.



Transition: 100-200-100 (scale = 20ms)

Above is a fairly typical response time curve example using the OD = normal mode and 144Hz. The rise time curve is very steep and measures at 4.9ms. The fall time is very similar and measures at 5.0ms. There is some very minor overshoot of 2% on the fall time.





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.

The response time performance of the XB270HU was very impressive indeed. It's the first 144Hz capable IPS-type panel on the market so it needed to be able to deliver when it comes to pixel response times. With an average G2G figure of 5.5ms measured, it was much faster than any other IPS panel we have seen to date, at best reaching down to 8.6ms without introducing a lot of overshoot (Dell U2415). It was pushing past some TN Film screens even like the Samsung U28D590D (7ms G2G average). It wasn't quite as fast as pure gaming TN Film models like the Asus ROG Swift PG278Q (2.9ms) and BenQ XL2720Z (3.8ms) although those models did show a moderate level of overshoot so it's debatable which is better. It was just really pleasing to see IPS response times reach this low and without any sign of overshoot problems as 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) @ 144Hz (OD = Normal)

In practice the Acer XB270HU performed best with the Overdrive setting on 'normal'. Motion blur was minimal and the moving image looked sharp and crisp. Motion felt very fast and fluid thanks to the 144Hz refresh rate, something which you can't really pick out with the camera. There was no overshoot detected at all which was equally as pleasing as the fast response times.



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



27" 4ms G2G AU Optronics AHVA (AMA Setting = High)



27" 12ms G2G Samsung PLS (Response Time = Advanced)



27 " 8ms G2G LG.Display AH-IPS (Response Time = Normal)



27" 8ms G2G LG.Display AH-IPS



Firstly it is interesting to compare the XB270HU to some of the other popular 27" models we have tested with 2560 x 1440 resolutions and IPS-type panels (IPS, PLS and AHVA). You can see first of all a comparison against the BenQ BL2710PT, ViewSonic VP2770-LED and Dell U2715Hwhich show a more noticeable blurred image. The Dell U2713HM is a little faster, but in practice cannot compete with the speed of the XB270HU still. The movement is clearer and smoother on the XB270HU, and you also have the massive benefit of the 144Hz refresh rate. Not to mention further gaming enhancements like G-sync and ULMB which we will cover in a moment.



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



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



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



23.5" 4ms G2G Sharp MVA + 120Hz

This is where the real comparisons are! We've also included a comparison above against 3 other very fast 120Hz+ compatible screens we have tested. The screens shown here are all aimed primarily at gamers and have various features and extras which make them more suitable overall for gaming, much like the XB270HU. Firstly there is a comparison against the very popular Asus ROG Swift PG278Q with its 144Hz refresh rate and fast response time TN Film panel. This showed very fast pixel response times and smooth movement thanks to its increased refresh rate. You are able to reduce the motion blur even more through the use of the ULMB strobed backlight as well if you need to. In other related areas this screen also supports NVIDIA's G-sync technology. There was some overshoot noticeable on the Asus but nothing major.

Then there is a comparison against the BenQ XL2720Z with another very fast TN Film panel and 144Hz refresh rate. This showed very low levels of motion blur, but some dark overshoot was introduced as a side-effect as you can see. This screen also includes a native Blur Reduction mode to help eliminate further perceived motion blur and works well.

Lastly there is the MVA based Eizo FG2421 screen with a fast response time (especially for the panel technology being used) and 120Hz refresh rate support. There is also an additional 'Turbo 240' motion blur reduction mode which really helps reduce the perceived motion blur in practice.

All things considered we felt that the Acer XB270HU performed the best in these specific tests. The response times were slightly slower than the Asus ROG Swift PG278Q and BenQ XL2720Z, but the benefit of that was that there was no overshoot on the Acer, whereas the others showed some moderate levels. The Acer also has a native blur reduction mode (ULMB) and G-sync support which we will look at shortly. One other thing to note here is that with the exception of the Asus ROG Swift PG278Q these other screens can only support a maximum 1920 x 1080 resolution, and so there's a huge jump in resolution and image quality when extending to a 2560 x 1440 panel in the XB270HU. You get the not-to-be-underestimated benefits of the IPS-type panel as well from the Acer, with wider viewing angles and a more stable image appearance compared with the TN Film models. Overall a very impressive performance from the XB270HU.





G-Sync

Obviously a huge part of the Acer XB270HU is the addition of NVIDIA's new G-sync technology. We covered this in our Asus ROG Swift PG278Q review as well, but we think it's worth repeating here. We thought it would be useful to give you some background on what G-sync is and what it offers. As an introduction, monitors typically operate at a fixed refresh rate, whether that is 60, 120 or 144Hz. When running graphically intense content like games, the frame rate can of course fluctuate somewhat and this poses a potential issue to the user. There are traditionally two main options available for how frames are passed from the graphics card to the monitor using a feature called VSYNC, whether Vsync is turned on or off.

Vsync Overview At the most basic level ‘VSync OFF’ allows the GPU to send frames to the monitor as soon as they have been processed, irrespective of whether the monitor has finished its refresh and is ready to move onto the next frame. This allows you to run at higher frame rates than the refresh rate of your monitor but can lead to a lot of problems. When the frame rate of the game and refresh rate of the monitor are different, things become unsynchronised. This lack of synchronisation coupled with the nature of monitor refreshes (typically from top to bottom) causes the monitor to display a different frame towards the top of the screen vs. the bottom. This results in distinctive ‘tearing’ on the monitor that really bothers some users. Even on a 120Hz or 144Hz monitor, where some users incorrectly claim that there is no tearing, the tearing is still there. It is generally less noticeable but it is definitely still there. Tearing can become particularly noticeable during faster horizontal motion (e.g. turning, panning, strafing), especially at lower refresh rates. The solution to this tearing problem for many years has been the ‘VSync ON’ option which essentially forces the GPU to hold a frame until the monitor is ready to display it, as it has finished displaying the previous frame. It also locks the frame rate to a maximum equal to the monitor’s refresh rate. Whilst this eliminates tearing, it also increases lag as there is an inherent delay before frames are sent to the monitor. On a 120Hz monitor the lag penalty is half that of a 60Hz monitor and on a 144Hz monitor is even lower. It is still there, though, and some users feel it disconnects them from game play somewhat. When the frame rate drops below the refresh rate of the monitor this disconnected feeling increases to a level that will bother a large number of users. Some frames will be processed by the GPU more slowly than the monitor is able to display them. In other words the monitor is ready to move onto a new frame before the GPU is ready to send it. So instead of displaying a new frame the monitor displays the previous frame again, resulting in stutter . Stuttering can be a major problem when using the Vsync on option to reduce tearing. During Vsync ON operation, there can also sometimes be a sudden slow down in frame rates when the GPU has to work harder. This creates situations where the frame rate suddenly halves, such as 60 frames per second slowing down to 30 frames per second. During Vsync ON, if your graphics card is not running flat-out, these frame rate transitions can be very jarring. These sudden changes to frame rates creates sudden changes in lag, and this can disrupt game play, especially in first-person shooters. NVIDIA G-sync Variable refresh rate solution To overcome these limitations with Vsync, NVIDIA have just introduced a new technology they have dubbed G-sync. This technology can be integrated into monitors to allow them to adopt a variable refresh rate, dynamically altering the monitor depending on the graphics card output and frame rate. The frame rate of the monitor is still limited in much the same way it is without G-SYNC, but it adjusts dynamically to a refresh rate as low as 30Hz to match the frame rate of the game. By doing this the monitor refresh rate is perfectly synchronised with the GPU. You don’t get the screen tearing or visual latency of having Vsync disabled, nor do you get the stuttering or input lag associates with using Vsync. You can get the benefit of higher frame rates from Vsync off (within the G-sync range of 30Hz - 144Hz) but without the tearing, and without the lag and stuttering caused if you switch to Vsync On. We don't want to go into too much depth about game play, frame rates and the performance of G-sync here as we will end up moving away from characteristics of the monitor and into areas more associated with the operation of the graphics card and its output. G-sync is a combined graphics card and monitor technology, but from a monitor point of view all it is doing is supporting this feature to allow the graphics card to operate in a new way. There are plenty of reviews and tests of G-sync online which cover the operation of G-sync in more detail. Our friends over at http://www.blurbusters.com/ have done some G-sync testing in various games which is well worth a read. They've also carried out various lag tests which have confirmed that using G-sync doesn't seem to add any noticeable lag, compared with running with Vsync off.

Above: G-sync options in the NVIDIA control panel We did run some tests using Battlefield 4 to see how it worked ourselves. In Battlefield you will experience a lot of varying frame rates due to the changes in scenery and the complexity of your surroundings. Playing with G-sync enabled allowed the monitors refresh rate to synchronise with the graphics card frame rate, and this nicely removed the stutter we saw from using Vsync. It also meant there was no tearing like you'd see from having Vsync off which of course is a massive bonus. We were very impressed by the fluidity and smoothness of motion and the absence of artefacts which can be easily detected in similar conditions when using Vsync on or Vsync off. We'd encourage you to read some of the G-sync reviews online as they go into a lot more detail about graphics card rendering, frame rates etc as well. It should be noted that the real benefits of G-sync really come into play when viewing lower frame rate content, around 45 - 60fps typically delivers the best results compared with Vsync on/off. At consistently higher frame rates as you get nearer to 144 fps the benefits of G-sync are not as great, but still apparent. There will be a gradual transition period for each user where the benefits of using G-sync decrease, and it may instead be better to use the ULMB feature discussed in the following section which is not available when using G-sync. Higher end gaming machines might be able to push out higher frame rates more consistently and so you might find less benefit in using G-sync. The ULMB could then help in another very important area, helping to reduce the perceived motion blur caused by LCD displays. Keeping in mind that the XB270HU features a large 2560 x 1440 resolution, you'd need a pretty powerful system to achieve consistently high frame rates, so we'd encourage you to try G-sync of course to see how it affects your gaming usage. It's nice to have both G-sync and ULMB available to choose from certainly. Well done Acer!

For more information on G-sync from NVIDIA, please visit their website:

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Ultra Low Motion Blur (ULMB)

The Acer XB270HU also features an integrated Blur Reduction Backlight system, dubbed "Ultra Low Motion Blur" (ULMB). We have already seen a lot of positive improvements in perceived motion blur from such systems in the past. Our in depth article from June 2013 looked at this in a lot more detail, and tested some of the original LightBoost "hacks" to achieve a strobed backlight and blur reduction benefits. Since then we've seen a couple of monitors integrate a similar strobed backlight with simple user control from the menu. The Eizo Foris FG2421 and BenQ XL2720Z both had useful integrated blur reduction modes built in to the screen. We first saw the ULMB feature when we tested the Asus ROG Swift PG278Q last July. This will be the first IPS-type panel though to feature a blur reduction mode of any type so it's really interesting to see how this performs.

The ULMB feature is accessible from the 'setting' section of the OSD menu as shown above.

For quick switching on and off it is also available via the quick launch menu option. It is only available when running the screen at 85 and 100Hz modes (see update below). The lack of support at the high refresh rates is probably related to a couple of factors. Mark Rejhon at Blurbusters.com talks about it a little in his post here as well. Firstly, to have effective "clean" strobing at 120Hz you really need pixel response times to be able to reach ~1ms G2G ideally, something that this IPS-type panel cannot reach. Even the best TN Film panels struggle to reach that kind of response time, so the strobing provided at 120Hz is still not clean. By limiting the ULMB to 100Hz maximum it is more appropriate for the kind of response times made possible from this new panel - which are excellent it should be noted for an IPS variant.

Secondly when you are using the ULMB feature you cannot use G-sync. As a result you are restricted to the Vsync on/off situation which we discussed earlier in the review. Limiting the refresh rate to 100Hz maximum is less of a drain on graphics resources than 120HZ/144Hz. You'd still need a beefy graphics capability to be able to output 100 fps consistently at 2560 x 1440 resolution, so we don't feel that the upper restriction here is really a massive issue. You still get fast pixel response times, 100Hz refresh rate and the benefits of perceived blur reduction discussed below.

Update 2/9/15: later versions of the XB270HU now feature support for 120Hz ULMB as well

When you enable the ULMB feature a new option appears in the OSD menu if you drill in to the ULMB option. This new setting allows you to adjust the "Pulse Width". We will test that in a moment as well, but it allows you to control the strobe length, and therefore adjust the visible persistence somewhat. You can adjust this between 100 and 10, and as you lower the setting the screen also becomes progressively darker as you reduce the "on" period of the strobe. Nice to see this included as an option within the menu for those who like to play around with the setting, much like you could do by adjusting LightBoost levels on older models using the "hack" method. There is no control to adjust the timing of the strobe to impact the strobe cross-talk it can introduce, so we will have to hope that the default timing setup is suitable. It should be noted that the brightness control when using ULMB is independent to the brightness control you might be using in the normal modes. So if you're using 20 brightness in the normal user mode and then switch to ULMB it will be set at 100 until you change it to whatever you like. This is good as you don't need to worry about turning brightness back up every time you move over to ULMB mode which is naturally darker to start with because of the strobing of the backlight.



Operation @ 85Hz



ULMB backlight cycling, 85Hz (scale = 5ms)

pulse width setting= 100

We measured the screen using our oscilloscope when viewing a solid white image, with ULMB feature turned on and with refresh rate set at 85Hz. This is the lowest refresh rate at which you can operate the ULMB mode. As a reminder, it works at 85 and 100Hz only on this screen. We left the pulse width (strobe length) setting at 100 initially. Normally the oscillograph would show a flat straight line when measuring a static white image (as no PWM is being used for backlight dimming), but here the ULMB feature is cycling the backlight off and on rapidly.

The time for each complete cycle is 11.76ms which shows that in this case the backlight is being cycled at the same frequency as the refresh rate, 85 times per second. The strobe is in time with the refresh rate of 85Hz.



ULMB backlight cycling, 85Hz (scale = 5ms)

pulse width setting = 50



ULMB backlight cycling, 85Hz (scale = 5ms)

pulse width setting = 10

As you reduce the pulse width setting the strobe 'on' time gets progressively shorter as you can see from the above 2 graphs, the first at a setting of 50 and the second at a setting of 10 (the minimum setting available). This impacts the perceived blur somewhat, with the shorter 'on' times resulting in a clearer image. At the same time though the brightness of the image is affected and it becomes very dark, the lower you go with the setting. More on that in a moment. There will be a point where the user does not see any further benefit to their eyes of reducing the strobe length further, but you can have a play around with the setting to find your personal preference to balance perceived motion blur and brightness of the image.

Pulse Width Setting - Strobe Behaviour @ 85Hz

We measured the strobe length at a variety of the Pulse Width settings, while running at 85Hz refresh rate mode. You can adjust the setting in steps of 1 incidentally. Oddly in the OSD the down arrow moves the slider up towards 100, and the up arrow moves it down towards 0. Each complete strobe lasts a total of 11.76ms here a (85 strobes per second):

Pulse Width Setting On period (ms) Off Period

(ms) 100 3.625 8.135 75 2.750 9.010 50 1.875 9.885 25 0.875 10.885 10 (min) 0.375 11.385

Pulse Width Setting - Brightness Range @ 85Hz

Pulse Width Setting Luminance

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

( x:1) 100 129.05 0.16 816 75 97.65 0.13 751 50 65.64 0.08 820 25 33.11 0.04 828 10 (min) 13.38 <0.02 -

We tested the brightness output of the screen when ULMB was turned on at various pulse width settings. You can independently control the brightness setting as well if you want, but we left it at the default 100 and just changed the pulse width strobe length setting to establish the brightness range when using this option. With the pulse width setting at 100 the maximum achievable luminance of the screen was a moderate 129 cd/m2. This should be enough for a lot of uses, but you cannot get a brighter display when using ULMB if you wanted to. This is a typical performance from a strobe backlight anyway and represented a decent enough luminance level. As you reduce the pulse width setting the luminance drops significantly, at the lowest setting probably being far too dark for any practical use. At least you can control a reasonably wide range here, so you can find a level which suits your needs. We suspect a setting of 100 will probably be adequate for most normal users anyway, as the ULMB mode certainly brings about positive improvements to the perceived motion blur.

Brightness Range @ 85Hz (Pulse Width at 100)

85Hz Refresh rate Brightness Setting Luminance

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

( x:1) 100 129.05 0.16 816 75 110.36 0.14 788 50 86.32 0.11 785 25 55.33 0.07 790 0 13.13 <0.02 -

We also wanted to test the brightness range when leaving the Pulse Width setting at its default 100, and changing the brightness control of the screen instead. The table above confirms the range available through that control. At 85Hz refresh rate the maximum luminance you could achieve was 129 cd/m2. Some users might find this too dark for some types of gaming and it's a shame you can't use the ULMB at a higher luminance. The strobing of the backlight is the reason for the reduced luminance compared with the normal mode of course. You would need an even brighter backlight system to allow for brighter ULMB operation. The 350 cd/m2 maximum rating of the W-LED unit used here is pretty standard for modern desktop monitors.





Operation @ 100Hz



ULMB backlight cycling, 100Hz (scale = 5ms)

pulse width setting = 100

When running the screen at a 100Hz refresh rate (max supported for ULMB) the behaviour is exactly the same. The only difference is that the strobe is now synced with the new refresh rate, with a new strobe every 10ms (100 times per second). The strobing was less noticeable to the naked eye at 100Hz, as there was a fairly noticeable visible flicker when running at 85Hz before, and it was less obvious now.

Pulse Width Setting - Strobe Behaviour @ 100Hz

We again measured the strobe length at a variety of the Pulse Width settings, while running at the maximum 100Hz refresh rate mode supported on this model. Each complete strobe lasts a total of 10ms (100 strobes per second):

Pulse Width Setting On period (ms) Off Period

(ms) 100 2.500 7.500 75 1.875 8.125 50 1.250 8.750 25 0.625 9.375 10 (min) 0.250 9.750

Pulse Width Setting - Brightness Range @ 100Hz

Pulse Width Setting Luminance

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

( x:1) 100 110.54 0.14 790 75 82.78 0.10 828 50 55.51 0.07 793 25 27.99 0.04 700 10 (min) 11.38 <0.02 -

We tested the brightness output of the screen when ULMB was turned on at various pulse width settings, again leaving the brightness at the maximum 100 setting.



Brightness Range @ 100Hz (Pulse Width at 100)

100 Hz Refresh rate Brightness Setting Luminance

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

( x:1) 100 110.54 0.14 790 75 94.42 0.12 787 50 74.25 0.09 825 25 47.52 0.06 792 0 10.74 <0.02 -

We also tested the brightness range of the screen at a refresh rate of 100Hz, leaving the Pulse Width setting at the maximum of 100. The luminance was lowered slightly compared with the 85Hz mode since the strobing was more frequent at 100Hz, resulting in a slightly darker image.





Colour and Other Setup Characteristics

We wanted to test the impact on the setup of the screen when enabling the ULMB feature to see whether it has a knock-on effect to white point, gamma or colour accuracy. You can see straight away that it impacts the luminance of the screen, which we've already looked at above.



Acer XB270HU - Calibrated Settings, ULMB Off





Calibrated Settings luminance (cd/m2) 121 Black Point (cd/m2) 0.12 Contrast Ratio 1000:1

Above is our calibrated state from earlier on in the review, with the ULMB feature turned off.



Acer XB270HU - Calibrated Settings, ULMB On





Calibrated Settings

ULMB On luminance (cd/m2) 129 Black Point (cd/m2) 0.16 Contrast Ratio 816:1

We turned the ULMB mode on, but left the Pulse Width option at 100 here, and with the default maximum 100 brightness as well. We left our calibrated ICC profile active from our initial calibration to see what immediate impact the ULMB setting had on the colour performance. The gamma and white point were skewed slightly here, with gamma now a little lower at 2.1 average (3% deviance), and white point being a little cooler at 6602k (2% out). The contrast ratio was reduced somewhat down to 816:1, still pretty respectable for an IPS-type panel though. The colour accuracy was also a little off with average dE of 0.9 now, maximum of 2.2. No major impact really to the appearance of the screen of the colour rendering other than the reduction in achievable luminance of course. This was pleasing as we know from testing older LightBoost strobed backlight systems that they can really impact the colours and white point of a screen when enabled. For what it's worth, the skewing of gamma, white point and dE was slightly less than when we tested the feature on the Asus ROG Swift PG278Q.

Blur Reduction Tests

Of course the main thing we want to test is what improvements the Blur Reduction mode offers when it comes to motion clarity and gaming. 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. So we were keen to understand if Acer had achieved something similar here with the World's first IPS-type panel with a blur reduction mode. Results are hard to capture with a standard camera, and most of the improvement is down to perceived motion blur levels to the user and the human eye . Our new pursuit camera tests in the following section give you a good indication of perceived motion blur with and without ULMB enabled.

We were very pleased with the results though here with a marked improvement in perceived motion blur experienced. Tracking of moving objects became much easier and the image looked sharper and clearer. We used the BlurBusters TestUFO online motion test (various ULMB supported refresh rates) as well to put the feature through its paces and were pleased with the results. The upper half of the screen was clearer than the bottom, being clearest at the very top. By the middle of the screen some minor strobe cross-talk is evident, but at quite low levels. At the bottom of the screen this gets worse. It is impossible to eliminate strobe cross-talk completely due to the way they operate, but the important thing is whereabouts on the screen this manifests itself and to what level. The central region is probably the most important since that's where a lot of your gaming focus will be, where crosshairs and the likes are. We were pleased that there was low levels of cross-talk here in the central region and the image looked good. Having the ability to alter the strobe length through the pulse width setting was also very useful, and you could tweak it to your preference to reduce even more of the persistence if you wanted, as long as you didn't mind sacrificing some brightness. The lack of a control over the 'phase' which would allow to to change where on the screen the cross-talk manifests itself is a minor point and won't bother most uses. We're sure a few enthusiasts would like to have that feature, but it wasn't provided on the Asus ROG Swift PG278Q either.

A very good implementation of a strobe backlight system here, we were impressed. We suppose the only minor quibble is the inability to operate the feature at 120Hz or 144Hz although the practicality of running at those kind of refresh rates with Vsync on/off and this resolution are questionable. In an ideal World, it would be great if you could use ULMB at the same time as using G-sync of course but that's not currently possible.







Pursuit Camera Tests (New)

We've already tested above the actual pixel response times and other aspects of the screen's gaming performance. We wanted to carry out some pursuit camera tests as well to give an even more complete idea of the performance of this screen, and the improvements made to motion blur when using the ULMB feature also.

Pursuit cameras are used to capture motion blur as a user might experience it on a display. They are simply cameras which follow the on-screen motion and are extremely accurate at measuring motion blur, ghosting and overdrive artefacts of moving images. Since they simulate the eye tracking motion of moving eyes, they can be useful in giving an idea of how a moving image appears to the end user. It is the blurring caused by eye tracking on continuously-displayed refreshes (sample-and-hold) that we are keen to analyse with this new approach. This is not pixel persistence caused by response times; but a different cause of display motion blur which cannot be captured using static camera tests. Low response times do have a positive impact on motion blur, and higher refresh rates also help reduce blurring to a degree. It does not matter how low response times are, or how high refresh rates are, you will still see motion blur from LCD displays under normal operation to some extent and that is what this section is designed to measure. Further technologies specifically designed to reduce perceived motion blur are required to eliminate the blur seen on these type of sample-and-hold displays which we will also look at.

We used the Blurbusters.com Ghosting Motion Test which is designed to be used with pursuit camera setups. The pursuit camera method is explained at Blurbusters as well as covered in this research paper . We carried out the tests at various refresh rates, with and without ULMB enabled. These UFO objects were moving horizontally at 960 pixels per second, at a frame rate matching refresh rate of the monitor.



Note: ULMB disabled

We carried out pursuit camera tests under each of the three OD (overdrive) settings, and at 3 different refresh rates between 60Hz and 144Hz. These tests can give you a good idea of actual perceived motion blur in practice on the monitor. For now we left the ULMB mode turned off.

With OD turned off there is a significant amount of motion blur perceived by the user when tracking moving objects across the screen. The pixel response times come in to play here as well as the refresh rate. With OD off the response times were pretty slow with an ~11ms G2G average recorded with our oscilloscope. This remained the same regardless of the refresh rate when OD was turned off. This slow response time manifests itself with a significant motion blur in practice. Switching from 60Hz up to 100Hz and then 144Hz brings about some changes in blurring, where it is reduced at higher refresh rates as a direct result of the improved frame rate. With response times remaining consistent with OD turned off, the reduction in motion blur perceived is down to the refresh rate entirely. The moving image becomes clearer and easier to track with the eyes as you increase screen refresh rate.

Switching the OD setting up to the optimal 'normal' mode, there are noticeable improvements in response times (measured earlier) and in resulting motion blur. In fact with OD at normal, the response times improve as you increase the refresh rate, from 8.7ms down to 5.9ms as you progress from 60Hz up to 144Hz refresh rate. We have seen from our earlier tests that the refresh rate seems to impact the level of overdrive applied to the liquid crystals, and so a higher refresh rate results in lower response times. You are getting a double whammy here when it comes to motion blur, with both the improved response times and higher frame rates having a positive influence on the blurring that you see. At all refresh rates there is a marked improvement in blur compared with OD off, as you would expect. It is not eliminated entirely due to the nature of the sample-and-hold LCD display and the tracking of your eyes. No matter how fast the refresh rate and pixel response times are, you cannot eliminate the perceived motion blur without other methods (which is where ULMB comes in).



Blurring test, OD normal, 60Hz

It is interesting to note that with OD set to normal at 60Hz we measured an 8.7ms G2G response time with no overshoot on the XB270HU. This would be considered a good result for an IPS-type panel at 60Hz and on par with some of the best IPS models we've seen in recent times (e.g. Dell U2415, 8.6ms G2G). Given response times are comparable, the results obtained at 60Hz here are a decent representation of the perceived motion blur you can expect from a normal 60Hz only IPS panel with good response times around the 8.7ms G2G mark and with no overshoot. This is the first IPS screen which can then offer higher refresh rates above 60Hz and the added bonus of improved response times (without overshoot problems) as well.

With OD set to the maximum 'extreme' setting there is again an improvement in blurring as you increase the refresh rate. We had measured response times to range from 7.0 to 4.8ms G2G average as you increase refresh rate up, but at the same time we know that the overshoot introduced becomes progressively worse. At 60Hz refresh rate there are some signs of pale trailing compared with the OD normal mode. By the time you reach up to the maximum 144Hz refresh rate the overshoot has become very noticeable and extremely high. Remember also that these UFO tests are only testing a few sample colour transitions, but we had measured some further very significant overshoot across many different G2G changes with OD set to extreme. We will reiterate that OD normal is optimum on this screen.



85Hz 100Hz



ULMB Enabled (PW = 100)

We left the strobe pulse width length at maximum setting here as it has an impact on brightness if you lower it, in an attempt to reduce motion blur even further. We felt the results were very good without needing to reduce the strobe length anyway here. With ULMB enabled the backlight is strobed briefly, once per refresh, for low persistence. The brief backlight flash prevents tracking-based motion blur and the moving object is far easier to see when tracking it across the screen with your eyes (or by the pursuit camera). There is extremely little leftover ghosting caused by pixel transitions (virtually invisible to the human eye), since nearly all (>99%+) pixel transitions, including overdrive artefacts, are now kept unseen by the human eye, while the backlight is turned off between refreshes.

The clarity of the moving image is improved significantly and tracking across the screen with your eye is much easier and clearer. You will note there is some cross talk evident here in the form of the trailing image, and a result of the strobe timing. These images were taken at the centre of the screen vertically, so it gives you a good indication also of the strobe cross-talk levels on this display, in the central region. In the middle region of the screen it is at low/moderate levels but is not too bothersome in practice. The cross-talk is reduced as you increase the refresh rate as well which is pleasing. These tests give you a good visual indication of the improvements which ULMB can bring in perceived motion blur.



Acer XB270HU vs. Asus ROG Swift PG278Q Pursuit Camera Comparisons

To make this really interesting, we brought the excellent Asus ROG Swift PG278Q back in to our lab as a reference point to make some direct comparisons in these new tests. We have also updated that review with full pursuit camera tests in this relevant section. We know from our review that if we leave the screen at the optimum OD normal mode it maintains a very low response time across all transitions (2.9ms G2G average), and that this is not controlled or impacted by the refresh rate of the screen. So from 60Hz to 144Hz you are getting consistently low response times of ~2.9ms G2G on the Asus screen. It will be interesting to compare this further with the Acer XB270HU, which at the same optimum OD normal setting has response times varying between 8.7 and 5.9ms G2G depending on the refresh rate (60 - 144Hz).

All tests were conducted at the optimum 'Normal' Overdrive setting on both screens. See the PG278Q review for further tests at other settings.



At 60Hz each refresh is displayed continuously for a full 1/60 second (16.7ms). There is a significant amount of motion blur perceived by the user when tracking moving objects across the screen on both monitors. The clarity of the moving image on the Asus was a bit better here at 60Hz as the pursuit camera images reveal. This can be attributed to the larger difference in response times between the two panels when running at 60Hz refresh rate (2.9ms Asus vs. 8.7ms Acer). You can also compare the blur with the Asus VG278H at 60Hz (2ms G2G quoted response time) in the tests carried out by BlurBusters.

At 100Hz refresh rate each refresh is displayed continuously for a full 1/100 second (10ms). This creates less motion blur compared with 60Hz to the user because of the increased refresh rate, but it it still there. There are improvements compared with 60Hz which right away shows why a higher refresh rate has a positive impact on real-life blurring in dynamic content. Until now, IPS-type panels have not been able to offer this natively.

Again the blurring is a little less noticeable on the Asus here behind the red moving UFO, but you will notice a more apparent bright trail behind the yellow portion of the image. On the Asus this is where some of the overshoot becomes apparent, to a small degree, on certain colour transitions. The Acer is free of overshoot artefacts completely using the OD normal setting.





At 144Hz refresh rate each refresh is displayed continuously for a full 1/144 second (6.94ms). This creates less motion blur still compared with before, but it is not eliminated entirely due to the sample and hold operation of LCD displays and the tracking of your eyes. No matter how fast the refresh rate and pixel response times are, you cannot eliminate the perceived motion blur without other methods (which is where ULMB comes in). The response times of the Acer have improved thanks to the increased refresh rate (5.9ms Acer vs. 2.9ms Asus). Again you will spot a little more blur on the Acer behind the red part of the image, but a brighter trail behind the yellow part on the Asus due to the overshoot which sometimes manifests itself.

With ULMB enabled the backlight is strobed briefly, once per refresh, for low persistence. The brief backlight flash 