Acer XB273K

Interlace pattern artifacts

On some monitors, particularly but not exclusively those with high refresh rates, interlace patterns can be seen during certain transitions. We refer to these as ‘interlace pattern artifacts’ but some users refer to them as ‘inversion artifacts’ and others as ‘scan lines’. They may appear as an interference pattern or mesh or interlaced lines which break up a given shade into a darker and lighter version of what is intended. They often catch the eye due to their dynamic nature, on models where they manifest themselves in this way. Alternatively, static interlace patterns may be seen with some shades appearing as faint horizontal or vertical bands of a slightly lighter and slightly darker version of the intended shade. We did not observe any dynamic or static interlace pattern artifacts on this model, however.

Responsiveness

Input lag

A small utility called SMTT 2.0 was used alongside a sensitive camera to analyse the latency of the Acer XB273K, with over 30 repeat readings taken to maximise accuracy. Using this method, we calculated 4.77ms (a little over 2/3rds of a frame at 144Hz) of input lag. Note that this measurement reflects both the element of input lag you ‘see’ (pixel responsiveness) and the element you ‘feel’ (signal delay). It indicates quite a low signal delay which shouldn’t bother most users. Note that we do not have the means to accurately measure input lag in an HDR environment or with G-SYNC active in a variable refresh rate and frame rate environment.

Perceived blur (pursuit photography)

In our responsiveness article, we explore some of the key concepts related to the topic. One of these very important concepts is known as perceived blur. This is contributed to not only by the pixel responsiveness of the monitor, but also the movement of your eyes as you track movement on this screen. This second factor is the key cause of perceived blur on modern monitors, although pixel responses still play an important role. We also introduce a photography technique called ‘pursuit photography’, which uses a moving camera to capture motion on a monitor in a way that reflects both the pixel responsiveness and eye (camera) movement. This contrasts with static photographs or videos which only represent the pixel response element of perceived blur.

The images below are pursuit photographs taken using the UFO Motion Test for ghosting, with the test running at its default speed of 960 pixels per second. This is a good practical speed for capturing such photographs and highlights both elements of perceived blur nicely. The UFOs move across the screen from left to right at a frame rate matching the refresh rate of the display. The monitor was tested at 60Hz (directly below), 98Hz, 120Hz and 144Hz using all of the ‘Over Drive’ settings; ‘Off’, ‘Normal’ and ‘Extreme’. Additional listed refresh rates that can be selected by the user include 82Hz, 30Hz and 24Hz. All rows of the UFO Motion Test were used, highlighting a range of pixel transitions between various shades. The two final columns show two reference screens for comparison, where possible. The ASUS PG27UQ, which is one of the more expensive variants of this screen. And the ViewSonic XG240R, which shows how things look where pixel responses aren’t really a limiting factor. Both reference screens are using what we deem to be their optimal pixel overdrive (response time) setting.



At 60Hz, shown above, the UFOs appear relatively soft and unfocused with a lack of distinct detail. This indicates a moderate level of perceived blur attributed to eye (camera) movement. There are varying degrees of trailing behind the object due to some weaknesses in pixel responsiveness. These are clearest with ‘Over Drive’ set to ‘Off’, where you can see a moderate powdery trailing behind the object for all rows. The ‘Normal’ setting cuts this down significantly, so only a light powdery trail remains for the dark (top row) and medium (middle row) backgrounds. The light background appears very clean. Overall, this is similar to the ASUS PG27UQ reference. The ‘Extreme’ setting cuts out the conventional trailing completely and actually appears cleaner overall than the XG240R reference, particularly when considering the medium background. There is a bit of overshoot (inverse ghosting) behind the object for the bright background, although it is faint. In practice there are some more noticeable examples of overshoot for other transitions when using this setting. We’d therefore consider both ‘Normal’ and ‘Extreme’ to be good settings for 60Hz – with the appropriate setting depending on your preference for a little conventional trailing vs. a bit of overshoot. The image below shows how things look with the refresh rate raised to 98Hz.



At 98Hz, above, the UFOs appear somewhat narrower and slightly more focused, indicating a significant decrease in perceived blur due to eye movement. There is again varying amounts of trailing behind the UFOs, with the nature of this trailing appearing quite different to at 60Hz. The ‘Off’ setting reveals a bold powdery trailing, revealing pixel responses that are simply too slow for effective performance at this refresh rate. They therefore add significantly to the overall perceived blur. The ‘Normal’ setting cuts this out very effectively indeed. There is the smallest hint of ‘powdery’ trailing behind the UFO body for the dark background and a small amount of overshoot (dark ‘shadowy’ trailing) elsewhere. But a very clean performance – slightly cleaner than the PG27UQ reference, even, particularly for the dark background. The ‘Extreme’ setting introduces colourful and very eye-catching overshoot, so is not attractive. ‘Normal’ is clearly optimal here and very well-tuned overall. The image below shows things increased to 120Hz.



At 120Hz, above, the UFOs appear slightly narrower again with some sharper detailing, indicating a further reduction in perceived blur due to eye movement. The trailing is quite similar to at 98Hz, really. The ‘Normal’ setting is again optimal and similar to the PG27UQ if not slightly cleaner. There is again just a hint of light powdery trailing for the dark background and some faint overshoot elsewhere, but nothing eye-catching. The ‘Extreme’ setting lives up to its name and gives extreme overshoot – not pleasant to look at, ‘Normal’ is clearly much better optimised. The final image, below shows the refresh rate increased to 144Hz. Using the ‘Over Clock’ feature in the ‘Gaming’ section of the OSD to include this as a listed refresh rate.



At 144Hz, above, the UFOs have a slight edge in detailing – with slightly more distinct segmentation. And they’re marginally narrower. This reflects a further decrease in perceived blur due to eye movement. The trailing behind the UFOs is very similar to at 120Hz. The ‘Normal’ setting is clearly optimal and nicely tuned here, with a very small amount of powdery trailing for the dark background and a little overshoot elsewhere. But this is not extreme and sticks quite tightly to the object rather than extending further back. It appears quite blended overall – certainly when compared to the obnoxious overshoot using the ‘Extreme’ setting’. The ‘Normal’ setting appears similar to the PG27UQ reference overall, with overshoot appearing slightly weaker (which is good). The segmentation is less clear on the PG27UQ shot, but that’s due to the camera picking it up slightly differently rather than an actual observable difference there. The XG240R reference is beautifully clean without any clear conventional trailing or overshoot – an absolute benchmark for excellent 144Hz sample and hold pixel response performance. Which the XB273K isn’t too far away from really.

Responsiveness in games and movies

On Battlefield V the monitor provided a solid 144Hz refresh rate, where the frame rate kept pace. With the monitor displaying up to 2.4 time as much information every second as a 60Hz monitor (at 60fps), the ‘connected feel’ was excellent. This describes the precision and fluidity that you feel when you interact with the game world and there’s a certain edge there at higher frame rates and refresh rates that can’t be matched by a 60Hz monitor, regardless of input lag. The relatively low latency of this model did help in this respect as well, however. The high frame rate and refresh rate combination also greatly reduced perceived blur due to eye movement, giving a significant competitive advantage. As we explore later, the pixel density also helped in that respect – a combination which really lent itself well to easy tracking and engagement of enemies. There were some slight weaknesses in pixel responsiveness in places. Where darker shades are involved in the transition, there were some instances of light ‘powdery’ trailing. This was quite faint and was only a relatively minor contributor to perceived blur – and most transitions were free from this sort of thing. There was also a bit of overshoot in places. Generally, this was a slight ‘shadowy’ trailing much as shown with Test UFO earlier. Sticking close to the object and quite well-blended. There were some instances of bright overshoot trailing in places as well, where some medium and very light shades combined. Even this was far from extreme and not particularly eye-catching, most users won’t find this bothersome. Overall we found the pixel responsiveness impressive, with good balance to the pixel overdrive and the monitor making excellent use of its 144Hz refresh rate.

We also observed Shadow of the Tomb Raider. Again, the monitor put in a strong 144Hz performance. The weaknesses in pixel responsiveness, be it light ‘powdery’ trailing or a bit of overshoot in places was really very minor and didn’t distract us from the gameplay. The majority of pixel transitions were performed fast enough for an excellent 144Hz performance. The monitor certainly benefited at high frame rates from a strong ‘connected feel’ and the sort of low level of perceived blur you’d hope for from a 144Hz monitor. As good as we’ve seen from a non-TN sample and hold LCD – and not too far behind a good high refresh rate TN model, either. The competitive edge of the frame rate isn’t really so important on titles like this, but the overall fluidity you both ‘see’ and ‘feel’ on this monitor was still welcome. We also observed a range of movie content, of various frame rates, including ~24 – 30fps content and 50 – 60fps content. There were no clear weaknesses from suboptimal pixel responses. There were faint traces of overshoot for a slim number of transitions, but nothing that really caught our eyes. The frame rate limited the fluidity here rather than any clear weakness from the monitor’s pixel responses.

As an Amazon Associate I earn from qualifying purchases made using the below link. Where possible, you’ll be redirected to your nearest store. Further information on supporting our work.

G-SYNC – the technology and activating it

Nvidia G-SYNC is a variable refresh rate technology that can be activated when a compatible Nvidia GPU is connected to a compatible monitor (such as the Acer XB273K). Our article on the technology explores the principles behind the technology and its benefits, so we won’t be repeating too much of that. Essentially the technology allows the monitor to dynamically adjust its refresh rate to match, where possible, the frame rate outputted by the GPU. When the two are in sync it gets rid of the tearing (VSync off) and stuttering (VSync on) that occurs when the two are unsynchronised. An additional benefit for those who hate tearing and usually like to use VSync is a reduction in latency compared to ‘VSync on’ in the variable frame rate environment. As noted in the responsiveness section, though, we don’t have a way to accurately measure this.

This monitor supports G-SYNC via DP 1.4 (DisplayPort), once connected to a compatible Nvidia GPU such as the GTX 1080 Ti used in our test system. Once connected up, G-SYNC should be automatically configured and ready to use. There’s usually even a little notification icon in the system tray telling you that a G-SYNC compatible display is detected. To check everything is configured correctly, open Nvidia Control Panel and navigate to ‘Display – Set Up G-SYNC’. Ensure that the checkbox for ‘Enable G-SYNC’ is checked, then select your preferred operating mode. As the image below shows, this technology works in both ‘Full Screen’ and ‘Window’ modes, provided the correct option is selected for this. If the G-SYNC options seem to be missing from Nvidia Control Panel, this may be remedied by reconnecting the GPU or possibly connecting the monitor to a different DP output if there’s one available. If the options are still missing, reinstalling the GPU driver or updating this is recommended.

Enable G-SYNC

Next you should navigate to ‘Manage 3D settings’. Here there are a few settings of interest, the first of which is ‘Monitor Technology’. This should be set to ‘G-SYNC’ as shown below. Assuming this is all set up correctly, you should see ‘NVIDIA G-SYNC’ listed as ‘Mode’ in the ‘Information’ section of the OSD menu (press top menu button when in main menu). The refresh rate listed there just corresponds to the static refresh rate you’ve selected in Windows or your game (‘Max Refresh Rate’ as stated). If you set the ‘Ambient Light’ to ‘MNT Status’ for ‘Lighting Style’, the lighting will be red to indicate G-SYNC is enabled vs. white for G-SYNC disabled. This just indicates the driver setting, not whether the technology is actively being used.

Set Monitor Technology to G-SYNC

The second setting of interest is VSync, which can be set to one of the following; ‘On’, ‘Use the 3D application setting’, ‘Off’ or ‘Fast’ (GPU dependent). The Acer supports a variable refresh rate range of 30 – 144Hz, with the maximum value (ceiling) corresponding to the refresh rate you’ve selected for the monitor in Windows or your game. That means that if the game is running between 30fps and 144fps, the monitor will adjust its refresh rate to match. When the frame rate rises above 144fps, the monitor will stay at 144Hz and the GPU will respect your VSync setting in the graphics driver. If you select ‘On’, VSync activates if the frame rate exceeds the static refresh rate that you’ve selected (e.g. 144Hz / 144fps) and the usual VSync latency penalty applies. If you select ‘Off’ then the frame rate is free to rise in an unrestricted way, but the monitor will only go as high as 144Hz – tearing and juddering will ensue if the frame rate rises above this. The ‘Use the 3D application setting’ largely works as you’d expect, but the general recommendation is to set VSync in the graphics driver if you wish to use it as in-game implementations can interfere with the smooth operation of G-SYNC. Some users prefer to leave VSync disabled and use a frame rate limiter set several frames below the maximum supported (e.g. 140fps) instead, avoiding any VSync latency penalty at frame rates near the ceiling of operation or tearing from frame rates rising above the refresh rate.

The ‘Fast’ option is available on some newer GPUs, such as the GTX 1080 Ti used in our test system. This enables a technology called ‘Fast Sync’, which only applies above the refresh rate and frame rate ceiling (>144Hz / 144fps). Below this G-SYNC operates as normal, whereas above this a special version of VSync called ‘Fast Sync’ is activated. This is a GPU rather than monitor feature so isn’t something we will explain in detail, but it is designed to reduce tearing at frame rates well above the refresh rate of the monitor. If you’re interested in this technology, which may be the case if you play older or less graphically demanding games at very high frame rates, you should watch this section of a video by Tom Petersen.

Set VSync according to preferences

If the frame rate drops below the lowest refresh rate supported by the monitor (i.e. the G-SYNC floor of 30Hz / 30fps) then the monitor sets its refresh rate to a multiple of the frame rate. This occurs regardless of VSync setting. If for example the game ran at 21fps, the monitor would set itself to 42Hz. This keeps stuttering and tearing from non-even divisions of frame rate and refresh rate at bay. As we explore shortly, though, low frame rates are low frame rates regardless of the technology. So whilst it is always beneficial to have stuttering and tearing removed, it’s also beneficial to have an elevated frame rate where possible. It’s also worth remembering that G-SYNC can’t eliminate stuttering caused by other issues on the system or game environment such as insufficient RAM or network latency. Some game engines will also show stuttering (or ‘hitching’) for various other reasons which won’t be eliminated by the technology. Finally, note that G-SYNC can be used at the same time as HDR.

G-SYNC – the experience

We tested a variety of games using G-SYNC and found the experience much the same on all of them, with the technology working as it should. We’ll therefore simply focus on one title for this section; Battlefield V. This title provides the necessary graphical flexibility to allow testing of the full range of refresh rates supported by G-SYNC (30 – 144Hz / 30 – 144fps). Even with graphics settings at rather low values, it was rare to see the game stay at a consistent 144fps. There were frequently dips below this, generally sticking in the triple digits unless action was particularly intense in a large-scale multiplayer match. Without G-SYNC enabled, even the slightest dips below 144fps provided a jarring and noticeable (to sensitive users like ourselves) stuttering if VSync was enabled or tearing if VSync was disabled. It was very nice indeed not having to contend with such issues from framerate and refresh rate mismatches, improving the overall gameplay experience significantly. We still preferred the experience at the upper end of this (~144fps) vs. the lower end (~100fps), as perceived blur was noticeably lower and there was a nice edge in ‘connected feel’. Sensitivity to tearing, stuttering and frame rate does of course vary. But either way, G-SYNC was a very pleasant addition to the experience here.

We also appreciated the technology at lower frame rates. If we ramped up the graphics settings to modest levels, those triple digits became a rare sight. There were frequent dips to around 60fps and sometimes a bit below. The perceived blur significantly increased and ‘connected feel’ was much worse due to the lower frame rates. But it was still very nice to have the experience free from stuttering and tearing from the frame rate and refresh rate departing from one another. As usual for a G-SYNC monitor, the monitor compensated well for changes in refresh rate by adjusting its pixel overdrive strength. This so-called variable overdrive avoided the sorts of issues you typically see on FreeSync models at reduced frame rate, such as significantly increased overshoot levels. The technology worked at lower frame rates as well. Increasing graphics settings sufficiently or at times when the action was really intense, there could be drops to 30fps or lower. Below this, tearing and stuttering was kept at bay due to the monitor sticking to a multiple of the frame rate with its refresh rate. For example, 20fps was matched by 40Hz as the monitor can’t go as low as 20Hz. This worked well and didn’t present any specific issues during activation or deactivation. If there were any (such as momentary stuttering), they were very well masked by the low frame rate anyway.

SDR Variable Backlight

As explored in the contrast section, the monitor includes a local dimming solution. This is used automatically under SDR and can be either enabled or disabled under SDR using the ‘SDR Variable Backlight’ setting in the ‘Picture’ section of the OSD. With this setting disabled, the backlight is controlled as a single unit. With the setting enabled, the backlight is split into multiple dimming zones – but only a few, according to our testing. The effect here is rather subtle. In some ways that’s good, because you don’t get the sort of extreme brightness changes that you’d get on a more complex local dimming solution. Such as the 384-zone FALD (Full Array Local Dimming) backlight used on the more expensive variants, which can give ‘halos’ around bright content surrounded very dark shades. But it only has a slight effect on the contrast and it’s quite situational. Even with very dark content covering one dimming zone and very bright content covering another, the increase in contrast is relatively minor – as we demonstrated earlier. In reality there is a complex mixture of dark and light shades covering all dimming zones. Although the overall mixture of that light and dark may vary in each dimming zone, so it can still give a nice little edge in contrast.

You also maintain control of the brightness or ‘Peak white (nits)’ used as a base for adjustments. Even for very bright scenes, the monitor will not exceed the brightness you’ve set here significantly. Provided your base level is set well above 100 cd/m² (‘nits’ as they’re referred to in the OSD). The variable backlight doesn’t seem to like going much below that level when displaying brighter content, so if you’re sensitive to brightness you might want to disable the feature. For very dark scenes with little to no light content, the dimming effect can be quite pronounced (not a bad thing) but usually it’s just a subtle change. This is really more of an enhanced Dynamic Contrast setting than a true local dimming solution. But it’s something that most users should find well-implemented and undistracting. So although the effect is subtle, it has a slight positive effect overall and most users will just want to leave this enabled (that is the default state) and forget about it. There is an associated setting ‘Backlight Response’ which can be set to various response speeds; ‘Gaming’ (default and fastest setting), ‘Hybrid’ (medium) and ‘Desktop’ (slowest). We’d advise leaving this on ‘Gaming’ and see no reason to use a lower setting.

HDR (High Dynamic Range)

HDR (High Dynamic Range) on a monitor describes the ability to distinctly display very deep dark shades and very bright light shades simultaneously. The display of a large range of shades between these, from very muted to highly saturated is also important. Ideally the monitor would be able to control the illumination of each pixel individually, a capability reserved for backlightless technologies such as OLED. For LCDs, it’s desirable for the monitor to use a complex backlight solution with hundreds if not more dimming zones – referred to as FALD (Full Array Local Dimming). By controlling illumination with high precision, the monitor can correctly display intricate mixtures of dark and light content. Some parts of the screen can be illuminated to high brightness levels so that bright shades have good ‘pop’ and stand out nicely, whilst other sections of the screen displaying darker shades would be illuminated to much lower levels. Keeping the black depth nice and low and the deeper shades appearing suitably ‘inky’. But HDR isn’t just about contrast on a monitor, it’s also about being able to display a huge range of colours. The ultimate goal with this in mind is coverage of a massive colour gamut known as Rec. 2020. A more achievable near-term aim is for a monitor to offer 90% DCI-P3 (a Digital Cinema Initiatives standard colour space). Finally, HDR makes use of 10-bit+ precision per channel, so it’s desirable for the monitor to support (at least) 10-bits per subpixel.

It is specifically the HDR10 pipeline which is used on monitors at the moment and the common standard supported most widely in games and other applications. For most games and other full screen applications that support HDR, the Acer XB273K will automatically switch into its HDR operating mode. As of the latest Windows 10 update, relevant HDR settings in Windows are found in ‘Windows HD Color settings’ which can be accessed via ‘Display settings’ (right click the desktop). Most game titles will activate HDR correctly when the appropriate in-game setting is selected. A minority of game titles that support HDR will only run in HDR if the setting is active in Windows as well. Specifically, the toggle which says ‘Play HDR games and apps’. If you want to view HDR movies on a compatible web browser, for example, you’d also need to activate the ‘Stream HDR Video’ setting. These settings are shown below. Also note that there’s a slider that allows you to adjust the overall balance of SDR content if HDR is active in Windows. In this case it simply acts as a digital brightness slider, so you lose but never gain contrast by adjusting it. Most users will find the image too bright for normal viewing when leaving this at the neutral position (‘50’), which also offers optimal contrast. The colours and overall image did at least look better balanced than many screens when you activate HDR and view SDR content. It appeared some way between SDR using the native gamut and with ‘SDR Colors sRGB’ active. Due to the brightness restrictions and inability to adjust that without loss of contrast, this won’t be a setting that you’ll want to use routinely when viewing SDR content. We’d recommend only activating HDR in Windows if you’re about to specifically use an HDR application that requires it, and have it deactivated when viewing normal SDR content on the monitor.

The Acer XB273K is VESA DisplayHDR 400 certified. This is the most basic level of certification that VESA will give to an HDR capable display. The HDR experience is therefore more limited than on the more expensive models such as the ASUS PG27UQ, which are VESA DisplayHDR 1000 certified. But there are certainly still some important boxes ticked for a decent HDR experience on this model, however. The specified colour gamut on this model is 90% DCI-P3, which exceeds the VESA DisplayHDR 400 standard and is (when considered in isolation) sufficient for any current specification level. We have no reason to doubt this claim for the measurements made earlier. With DCI-P3 being the near-term standard HDR game developers and movie directors aim for with their HDR content, it’s important to have good coverage of this colour space.

Although our testing is focused on HDR PC gaming, our observations also apply to HDR movie content and running HDR on a compatible games console. The experience is dictated and, in many respects limited, by the capabilities of the screen itself. We tested various game titles but will simply be focusing our attention in this section on two; Battlefield V and Shadow of the Tomb Raider. Both titles have good HDR implementations and we’ve seen various HDR monitors in action on these and similar titles (such as BF1), so have a good range of references to compare with. The monitor’s colour gamut was put to good use under HDR on both titles. Vegetation was more natural-looking, with some of the greens appearing slightly too bright under SDR. These were now appropriately muted. Some earthy brown shades and rich wooden tones appeared more neutral, too, compared to the slightly excessive red hue under SDR. The same applied to skin tones, such as that of the infamous Lara Croft, which appeared appropriately saturated. There were still plenty of deep shades, such as good dark military green and rich red paints and an excellent palette of vibrant yellows and oranges for fires and explosions. As a reminder, the colour gamut of the monitor (below) offers good extension beyond sRGB and reaches reasonably close to the DCI-P3 colour space targeted by game developers for HDR content.

Colour gamut 'Test Settings'