ASUS VG28UQL1A

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, 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 either artifact type on this monitor.

Responsiveness

Input lag

A sensitive camera and a utility called SMTT 2.0 was used alongside a sensitive camera to analyse the latency of the ASUS VG28UQL1A. Over 30 repeat readings were taken to help maximise accuracy. Using this method, we calculated 2.82ms (under ½ a frame at 144Hz) of input lag and recorded similar values at 120Hz. At 60Hz we measured a significantly higher value of 23.46ms. These figures are influenced by both the element of input lag you ‘see’ (pixel responsiveness) and the main element you ‘feel’ (signal delay). They indicate a low signal delay at high refresh rates, which even sensitive users shouldn’t find bothersome. Note that we don’t have the means to accurately measure input lag with VRR technology active in a VRR environment or HDR active in an HDR environment.

Perceived blur (pursuit photography)

Our article on responsiveness explores the factors affecting monitor responsiveness. A key concept explored there is ‘perceived blur’, which is contributed to by both the pixel responses of the monitor and the movement of your eyes as you track motion on the screen. This second factor dominates on modern monitors, but both factors play an important role. A technique called ‘pursuit photography’ is also explored in the article, using a moving rather than stationary camera to capture motion in a way that reflects both aspects of perceived blur. Rather than just reflecting the pixel response element.

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 to take such photographs at and highlights both elements of perceived blur well. The UFOs move across the screen from left to right at a frame rate matching the refresh rate of the display. All three rows of the test are analysed to highlight a range of pixel transitions. The monitor was tested at 60Hz (directly below), 120Hz and 144Hz using various ‘Variable OD’ levels; ‘Level 0’, ‘Level 1’, ‘Level 3’ and ‘Level 5’. ‘Level 2’ and ‘Level 4’ just slot neatly between the tested levels in terms of what they show, so weren’t included in this analysis. The two final columns show reference screens, set to what we consider their optimal response time setting for a given refresh rate. The Acer XV282K KV which uses the same Innolux IPS-type panel as this model. And the ASUS PG27UQ, a tightly-tuned model with G-SYNC module and older AUO AHVA panel. This is natively slower than the Innolux panel but is quite strongly accelerated in the PG27UQ.

Note that wavy patterns surrounding some UFOs in the background are slight image retention. This was only observed during this test and is something we’ve seen on various monitors before. It soon disappeared when using monitor normally.

At 60Hz, above, the UFO appears soft and unfocused without clear internal detailing. This reflects a moderate amount of perceived blur due to eye movement. No conventional trailing is observed here from slower than optimal pixel response times, even with ‘Variable OD = Level 0’. There’s a moderate amount of overshoot visible in the form of ‘halo’ trailing that’s brighter than the background shade, however. Increasing the ‘Variable OD’ setting simply increases this further, so we consider ‘Level 0’ optimal here. Similar observations were made on the Acer XV282K KV used as a reference here, based on the same panel. In both cases the lowest response time setting still provided quite strong acceleration with a fair bit of overshoot. It was marginally lower on the ASUS, but not massively so. Others have noted this with the Gigabyte M28U, also based on the same panel. This panel may include an integrated OD (overdrive) circuit that can’t be disabled by manufacturers but can only be built upon with extra acceleration. The PG27UQ reference shows a touch of conventional trailing, which we’d classify as ‘light powdery’ trailing, but is essentially free from overshoot. Below you can see how things appear with refresh rate doubled to 120Hz.

At 120Hz, above, the UFO appears significantly narrower with clearer internal detail. This reflects a significant decrease in perceived blur due to eye movement. There’s no real conventional trailing to speak of, with just the faintest trace of ‘powdery’ trailing for the dark background (top row). The overshoot is reduced significantly compared to at 60Hz – some does still remain, but it’s really rather well-tuned here. Increasing the ‘Variable OD’ level brings no real advantage, it simply strengthens the overshoot. We again consider ‘Level 0’ optimal here, with the XV282K KV performing very similarly. The PG27UQ requires aggressive pixel overdrive to keep conventional trailing in check at 120Hz, with clearer overshoot visible. Plus some conventional trailing creating a fringe behind the yellow UFO cockpit for the dark background. Below you can see things running at a slightly higher 144Hz.

At 144Hz, above, the UFO appears very slightly narrower with slightly better definition. This reflects a slight reduction in perceived blur to eye movement, but it’s only an extra 24Hz so this difference is slight compared to the initial bump from 60Hz to 120Hz. The trailing is similar to at 144Hz, with the monitor providing a strong performance even with ‘Variable OD = Level 0’. There’s again no real conventional trailing to speak of, just a whiff for the dark background. Increasing the ‘Variable OD’ level really just serves to strengthen the overshoot. The bump up to ‘Level 1’ doesn’t provide extreme overshoot so may appeal to some. But even considering a broader range of transitions than analysed here, we find any decrease in the generally very low level of conventional trailing negligible and the increase in overshoot easier to notice. Beyond that the overshoot becomes particularly strong and eye-catching. We again consider ‘Level 0’ optimal here. Performance is similar to the XV282K KV reference here and again superior to the PG27UQ.

The monitor also includes a setting called ‘ELMB/ELMB SYNC’ (Extreme Low Motion Blur), with the ‘SYNC’ indicating it can be used at the same time as VRR technology. This is a strobe backlight setting which forces the backlight to flicker in sync with the refresh rate of the monitor. 100Hz, 120Hz and 144Hz can be selected as a static refresh rate (ELMB) or as the ceiling of operation (ELMB Sync). The lowest refresh rate the monitor will strobe at for ELMB Sync is 77Hz, below which the technology deactivates. Sensitivity to this flickering of the backlight varies and some will find it bothersome whilst others may notice accelerated eye fatigue, even if the flickering isn’t actively bothersome to them. The pursuit photographs below were taken with the monitor set to 100Hz using ELMB and ELMB Sync, with the highest and lowest ‘Clarity Level’ tested for ELMB. Increasing the ‘Clarity Level’ reduces the pulse width, meaning the backlight spends longer in its ‘off’ phase than for lower clarity levels. This reduces brightness as we explored earlier but also offers a potential boost to clarity. With ELMB Sync this can’t be adjusted and is set to an intermediate level, similar to ‘Level 3’. The reference screens used for comparison are the AOC C24G1 using its ‘MBR’ setting and the Dell S2417DG using its ‘ULMB’ settings. These are both quite useable strobe backlight settings and make appropriate references.

‘Variable OD’ is locked off under ELMB and ELMB Sync. A ‘Clarity Position’ setting is available which adjusts the strobe behaviour to optimise clarity either higher up or lower down the screen. We set this to the top level during this test as it was our preferred setting – we explore this setting in more detail shortly. Note that the UFO segmentation is a bit more distinct to the eye than it appears in the photos as the intensity of red in the images bleaches out the thin black line which divides the segments.

With ‘ELMB/ELMB SYNC’ active at 100Hz, above, the main object is significantly narrower with clearer internal detailing compared to with the setting deactivated – even at a higher refresh rate. The white notches on the UFO body show particularly strong clarity using ‘Clarity Level 5’. This shows that the setting is achieving its main purpose of reducing perceived blur due to eye movement. Fairly strong overshoot is visible behind the UFO, stronger than either reference screen when observing the same row of the test used (middle row – medium background). Some trailing is also visible behind and to a greater extent in front of the object, as a distinct repetition of the object due to the strobe nature of the backlight. These repetitions are broadly termed ‘strobe crosstalk’ and can be seen quite distinctly on the C24G1 reference as well. The KSF phosphors of the backlight introduce a colourful (magenta to red) fringes to the crosstalk here, due to their relatively slow decay rate. This is not observed on the reference screens as they don’t use KSF phosphors. The images below show the monitor running with ‘ELMB/ELMB SYNC’ set to 144Hz.

Note we didn’t include results for 120Hz as that didn’t show any novel behaviour. It simply appeared some way between what is shown at 100Hz and 144Hz.

With ‘ELMB/ELMB SYNC’ active at 144Hz, above, the main object again shows excellent clarity. The segments and white notches were clearer than they appear in the photo, distinct using ‘ELMB Sync’ and very distinct using ELMB with ‘Clarity Level 5’. The trailing behaviour is a bit different now, with overshoot reduced quite a bit and the overshoot or strobe crosstalk fragments more compact due to the increased refresh rate. The overall strobe crosstalk and overshoot levels aren’t extreme here, comparable to the reference screens but showing a bit of both rather than one or the other. The magenta to red fringing is again visible and is the main visual distraction in practice, something not observed on the reference screens. Not all areas of the screen refresh simultaneously, so the strobe crosstalk can be stronger or weaker depending on how far up or down the screen the motion is observed.

The images below show pursuit photos running from the top to bottom of the screen at a refresh rate of 144Hz. A ‘Clarity Level’ of ‘Level 3’ was used for ELMB, although this did not affect strobe crosstalk position. The ‘- Middle -‘ marker denotes the central region of the screen. All available ‘Clarity Position’ settings are shown using both ELMB and ELMB Sync. These photos are only designed to highlight strobe crosstalk behaviour and don’t accurately reflect the clarity of the main object. For example, how defined the segments or notches are which is excellent in all cases unless there’s overlapping strobe crosstalk.

You can see varying levels of strobe crosstalk depending on how far up or down the screen you’re observing. Sometimes it is so strong that it melds into the main object, other times it appears as a fainter repetition of the object in front or behind. The strongest strobe crosstalk is displaced either further up or further down the screen, depending on the setting used. For the best central clarity we’d actually consider ‘Clarity Position = Top’ optimal, especially using ELMB Sync where the ‘Clarity Position = Middle’ setting provides quite a bit of strobe crosstalk centrally. The central bands of the screen are where your eyes are mainly going to be focusing on for the competitive titles this sort of setting is designed for. So optimising performance there is often desirable even if it comes at the expense of other regions. We explore the ELMB and ELMB Sync experience subjectively using in game examples shortly.

Responsiveness in games and movies

On Battlefield V, at a frame rate keeping up with the 144Hz refresh rate, the monitor provided an impressively fluid performance. Compared to a 60Hz monitor or this monitor running at 60Hz (or 60fps), over twice the visual information is outputted every second. This greatly enhances the ‘connected feel’, which describes the precision and fluidity felt when interacting with the game. Low input lag also helps in that respect, which is something this model delivered. The high frame and refresh rate combination also decreases perceived blur due to eye movement, as demonstrated earlier using Test UFO. This gives a nice competitive edge in games like Battlefield, making it easier to track and engage enemies. It also complements the high pixel density nicely, with the monitor preserving some of this detail better during motion compared to the 60Hz experience.

The other aspect of perceived blur is pixel responsiveness, where this monitor again put in a strong 144Hz performance. Much as highlighted earlier using Test UFO, but now considering a broader range of transitions, there were no real complaints when it came to conventional trailing or related weaknesses. Most pixel responses were performed impressively quickly, with just a few small traces of faint ‘powdery’ trailing for some transitions. For example, very bright shades such as white in-game text against somewhat darker backgrounds. Even this weakness was minor and not at all eye-catching in our view or something most would notice at all. There was some overshoot in places, a bit of ‘halo’ trailing that was slightly brighter than the background shade. But this wasn’t particularly strong – sensitivity to overshoot varies, but this is unlikely to bother most users at high refresh rates.

Shadow of the Tomb Raider provided a similarly strong 144Hz performance. Some IPS-type panels will struggle with some of the ‘high contrast’ transitions that are common on this title, with plenty of dark shades involved. And VA models will typically perform poorly here. In this case there was very little to complain about in terms of conventional trailing and just a touch of overshoot in places. Whilst this sort of strong performance isn’t as important from a competitive perspective – as this is a slower paced single player title – it’s still a nice bonus. Sensitivity to refresh rate and response performance varies so not everyone would notice this difference so readily, but for us it certainly enhanced the experience. We also observed video content at a range of refresh rates, including ~24 – 30fps content on platforms such as Netflix and 60fps YouTube content. There were no real weaknesses from the monitor when it came to pixel responses. Small traces of overshoot here and there, but nothing we found eye-catching. For both the ~60fps and ~24 – 30fps content the main barrier to fluidity was really the frame rate of the content itself, not any weakness from the monitor.

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ELMB (Extreme Low Motion Blur) and ELMB Sync

Earlier in the review ELMB Sync was covered, including its principles of operation and how it performs using specific tests. When using a strobe backlight feature, your frame rate must match the refresh rate precisely. Otherwise you’re left with extremely obvious stuttering or juddering. Standing out in such a clear way due to there being very little perceived blur due to eye movement to mask it. With ELMB Sync the ability to use VRR technology such as Adaptive-Sync or HDMI 2.1 VRR at the same time alleviates this issue. You’re also limited to certain brightness levels as covered earlier and you can’t use the technology under HDR or with ‘Dynamic Dimming’ enabled. We tested ELMB Sync using a range of game titles, but to keep things simple we’ll just use Battlefield V for this section. Using ELMB without the Sync element unlocked the ‘Clarity’ levels option, but this didn’t significantly impact the main observations made here. The brightness level was really the most pronounced change there. There was little clarity benefit to be had beyond ‘Level 3’, which is our preferred level and similar to the level ‘ELMB Sync’ is locked to.

At a solid 144Hz (144fps), the technology did its thing to significantly reduce perceived blur due to eye movement. The clarity of the main objects and textures during motion was excellent, even during rapid turns of the character or when zipping about in a vehicle. This can be beneficial at a competitive level as it makes it easier to track and potentially engage enemies. We observed a moderate amount of strobe crosstalk in some regions of the screen, but with ‘Clarity Position’ set appropriately (centre or top worked well), this wasn’t particularly for central bands of the screen. Where your eyes mainly focus when playing games like this. There were issues we found more noticeable, such as a distinct red or magenta fringe in places due to the KSF backlight phosphors and their slow decay. This was particularly noticeable where brighter shades were involved in the transition. Colourful flashes were also observed when moving our eyes, especially with lighter coloured objects displayed. The flashes were typically green, cyan or magenta but sometimes other colours could be perceived. Some colourful ‘halo’ trailing (overshoot) was also present. And there was of course flickering due to the backlight strobing – sensitivity to this varies and it’s required for this sort of setting to do its thing.

If frame rate reduced at all below this and you’re running ELMB on its own, you’re presented with clear stuttering. There’s very little perceived blur due to eye movement to mask this. If VRR is enabled, it’s instead ELMB Sync you’re using. This provided a similar experience at 144Hz, although as explored earlier we found setting ‘Clarity Position’ to the top worked best to minimise central strobe crosstalk. ELMB Sync also allowed the refresh rate to reduce in accordance with the frame rate. This worked exactly as it should to remove this stuttering (or any tearing, if VSync is disabled) and provided a good boost in clarity compared to non-ELMB operation. As refresh rate reduces the flickering becomes more intense and you lose something in the way of ‘connected feel’ whilst also losing out a bit on clarity. Some inescapable side-effects of the reduction in frame rate. We also observed strobe crosstalk becoming a bit more intense in some cases, particularly for double digit refresh rates. And also observed an increased level of overshoot. Including some quite distinct ‘shadowy’ or ‘dirty’ trailing that was darker than the background colour and stood out for that reason. On top of some rather distinct and bright ‘halo’ trailing.

Below 77Hz (77fps) the ELMB technology deactivated and things reverted to normal VRR operation without the strobe element. By this point the flickering is already quite intense and below this that would simply worsen. The sudden switch between strobing and non-strobing that occurs here is certainly an abrupt change, so if you’re frequently passing this point it would certainly be bothersome. Although we still consider the overall strobe backlight experience to be suboptimal due to various visual disturbances, the ‘Sync’ element did work and was a nice flexibility to have. Some people will certainly see benefit from this technology, including those generally avoiding such technologies due to it being tricky to maintain a suitably high frame rate all the time.

VRR (Variable Refresh Rate) technology

FreeSync – the technology and activating it

AMD FreeSync is a variable refresh rate technology, an AMD-specific alternative to Nvidia G-SYNC. Where possible, the monitor dynamically adjusts its refresh rate so that it matches the frame rate being outputted by the GPU. Both our responsiveness article and the G-SYNC article linked to explore the importance of these two elements being synchronised. At a basic level, a mismatch between the frame rate and refresh rate can cause stuttering (VSync on) or tearing and juddering (VSync off). FreeSync also boasts reduced latency compared to running with VSync enabled, in the variable frame rate environment in which it operates.

FreeSync requires a compatible AMD GPU such as the Radeon RX 580 used in our test system. The monitor itself must support ‘VESA Adaptive-Sync’ for at least one of its display connectors, as this is the protocol that FreeSync uses. The VG28UQL1A supports FreeSync via DP and HDMI on compatible GPUs and systems. Note that HDR can be activated at the same time as FreeSync. You need to make sure ‘Adaptive-Sync’ (DP) or ‘Freesync Premium Pro’ (HDMI) is enabled in the ‘Gaming’ section of the OSD. Regardless of how the setting it reported in the OSD, it’s AMD FreeSync Premium that’s supported in both cases. On the GPU driver side recent AMD drivers make activation of the technology very simple. You should ensure the GPU driver is setup correctly to use FreeSync, so open ‘AMD Radeon Software’, click ‘Settings’ (cog icon towards top right) and click on ‘Display’. You should then ensure that the first slider is set to ‘Enabled’ as shown below. The top image shows the monitor connected by DP and the bottom image by HDMI. The setting is referred to as ‘AMD FreeSync Premium’ in both cases, although the exact wording may depend on the driver version you’re using.

The ASUS supports a variable refresh rate range of 48 – 144Hz. That means that if the game is running between 48fps 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 selection of ‘VSync on’ or ‘VSync off’ in the graphics driver. With ‘VSync on’ the frame rate will not be allowed to rise above 144fps, at which point VSync activates and imposes the usual associated latency penalty. With ‘VSync off’ the frame rate is free to climb as high as the GPU will output (potentially >144fps). AMD LFC (Low Framerate Compensation) is also supported by this model, which means that the refresh rate will stick to multiples of the frame rate where it falls below the 48Hz (48fps) floor of operation for FreeSync. If a game ran at 36fps, for example, the refresh rate would be 72Hz to help keep tearing and stuttering at bay. LFC sometimes seemed to activate at slightly higher refresh rates, closer to 52Hz (52fps), but this makes little difference in practice. This feature is used regardless of VSync setting, so it’s only above the ceiling of operation where the VSync setting makes a difference.

To configure VSync, open ‘AMD Radeon Software’. Click ‘Settings’ (cog icon towards top right) and click ‘Graphics’. The setting is listed as ‘Wait for Vertical Refresh’. This configures it globally, but if you wish to configure it for individual games click ‘Game Graphics’ towards the top right. The default is ‘Off, unless application specifies’ which means that VSync will only be active if you enable it within the game itself, if there is such an option. Such an option does usually exist – it may be called ‘sync every frame’ or something along those lines rather than simply ‘VSync’. Most users will probably wish to enable VSync when using FreeSync to ensure that they don’t get any tearing. You’d therefore select either the third or fourth option in the list, shown in the image below. Above this dropdown list there’s a toggle for ‘Radeon Enhanced Sync’. This is an alternative to VSync which allows the frame rate to rise above the refresh rate (no VSync latency penalty) whilst potentially keeping the experience free from tearing or juddering. This requires that the frame rate comfortably exceeds the refresh rate, not just peaks slightly above it. We won’t be going into this in detail as it’s a GPU feature rather than a monitor feature.



Some users prefer to leave VSync enabled but use a frame rate limiter set a few frames below the maximum supported (e.g. 141fps) instead, avoiding any VSync latency penalty at frame rates near the ceiling of operation or tearing from frame rates rising above the refresh rate. If you activate the ‘FPS Counter’ feature in the ‘GamePlus’ section of the OSD, the refresh rate will be displayed on the screen. This will reflect the frame rate if it’s within the VRR range and the monitor is running with a VRR technology such as FreeSync. The final point to note is that FreeSync only removes stuttering or juddering related to mismatches between frame rate and refresh rate. It can’t compensate for other interruptions to smooth game play, for example network latency or insufficient system memory. Some game engines will also show stuttering (or ‘hitching’) for various other reasons which won’t be eliminated by the technology.

FreeSync – the experience

We tested a range of game titles using AMD FreeSync and as usual found the experience similar in all cases. Any issues affecting one title points towards a game or GPU driver issue rather than a monitor issue. To keep things simple, we’ll just use Battlefield V as our example in this section. The graphics options offer good flexibility and allow the entire VRR range to be tested with our Radeon RX 580. Some dips below 144fps were very common, even with quite extreme adjustments. Without the technology active you get tearing (VSync off) or stuttering (VSync on) due to frame and refresh rate mismatches, so having those interruptions removed was nice. Particularly welcome if you’re sensitive to tearing and stuttering. Drops in frame rate could still be noticed due to their negative effect on ‘connected feel’ and an increase in perceived blur.

We also observed an increase in overshoot as refresh rate dipped – which follows a reduction in frame rate in a VRR environment. As we explored earlier with static refresh rates, the monitor advertises variable overdrive and even refers to the response time setting as ‘Variable OD’. But for whatever reason it isn’t as well-optimised as it could be, likely as the panel itself has some innate acceleration that can’t be disabled. The overshoot became quite strong to our eyes with frame rates in the double digits in particular, although sensitivity to overshoot varies. We felt the ‘halo’ trailing (brighter than the background) was quite bright and fairly eye-catching, particularly as refresh rate dropped closer to 60Hz than 100Hz. We wouldn’t describe the overshoot as ‘extreme’, but unfortunately the monitor doesn’t provide a means to remove this in a VRR environment. As we made these observations using the lowest level of ‘Variable OD’ (pixel overdrive) on the monitor. For those sensitive to overshoot but not so sensitive to tearing and stuttering, disabling VRR where the refresh rate dips significantly and sticking to a static 144Hz or 120Hz might be the best option.

The technology worked down to the floor of operation of 48Hz (48fps), below which LFC (Low Framerate Compensation) came into play. Keeping the refresh rate at a multiple of the frame rate to keep tearing and stuttering at bay. There was a brief stuttering when passing this boundary in either direction, potentially annoying if you’re frequently doing so but not something you’d generally find bothersome otherwise. This is something we universally observe with LFC and not specific to this model.

Nvidia Adaptive-Sync (‘G-SYNC Compatible’)

As noted earlier, AMD FreeSync makes use of Adaptive-Sync technology on a compatible monitor. As of driver version 417.71, users with Nvidia GPUs (GTX 10 series and newer) and Windows 10 can also make use of this Variable Refresh Rate (VRR) technology. When a monitor is used in this way, it is something which Nvidia refers to as ‘G-SYNC Compatible’. The ASUS is amongst models which are specifically validated as G-SYNC compatible, which means it has been tested by Nvidia and passes specific quality checks. With the VG28UQL1A you can connect the monitor up via either DisplayPort 1.4 or HDMI 2.1 to use ‘G-SYNC Compatible Mode’, with the latter technically making use of HDMI 2.1’s integrated VRR functionality rather than Adaptive-Sync. You need to make sure ‘Adaptive-Sync’ (DP) or ‘FreeSync Premium Pro’ (HDMI) is set to ‘On’ in the ‘Gaming’ section of the OSD. When you open up Nvidia Control Panel, you should then see ‘Set up G-SYNC’ listed in the ‘Display’ section. Ensure the ‘Enable G-SYNC, G-SYNC Compatible’ checkbox and ‘Enable settings for the selected display model’ is checked as shown below and press ‘OK’. If you’ve enabled ‘G-SYNC Compatible’ and it was previously disabled, the monitor should re-establish its connection with the system and the technology should now be active.



As noted previously and as highlighted in Nvidia Control Panel, this model has been specifically tested and validated as ‘G-SYNC Compatible’ by Nvidia. The experience using ‘G-Sync Compatible Mode’ on our RTX 3090 was very similar to the experience we described earlier using AMD FreeSync on this model. With the technology getting rid of tearing and stuttering from what would otherwise be frame and refresh rate mismatches, within the VRR range of 48 – 144Hz (48 – 144Hz fps). An LFC-like frame to refresh multiplication technology was employed below that to keep tearing and stuttering from frame and refresh rate mismatches at bay. There was again a momentary stuttering as the boundary was crossed, as we observed with our AMD GPU as well. Our suggestions regarding use of VSync also apply, but you’re using Nvidia Control Panel rather than AMD Radeon Software to control this. The setting is found in ‘Manage 3D settings’ under ‘Vertical sync’, where the final option (‘Fast’) is equivalent to AMD’s ‘Enhanced Sync’ setting. You’ll also notice ‘G-SYNC Compatible’ listed under ‘Monitor Technology’ in this section, as shown below. Make sure this is selected (it should be if you’ve set everything up correctly in ‘Set up G-SYNC’).



Note again that you can activate the ‘FPS Counter’ feature in the ‘GamePlus’ section of the OSD. This will display the refresh rate of the display and therefore indicates the frame rate if that is within the VRR window (48 – 144Hz). This is a useful indication that the technology is active. And as with AMD FreeSync Premium, HDR can be used at the same time as ‘G-SYNC Compatible Mode’.

HDMI 2.1 VRR

HDMI 2.1 includes Variable Refresh Rate (VRR) support as part of the specification. This is an integrated technology, which unlike FreeSync does not rely on VESA Adaptive-Sync to function. As such it can potentially be used by devices such as the PS5 that don’t support Adaptive-Sync. It can also be leveraged via ‘G-SYNC Compatible Mode’ on compatible Nvidia GPUs. Based on our testing of ‘G-SYNC Compatible Mode’ using HDMI 2.1 VRR, the experience was very similar to the Adaptive-Sync experience under SDR and HDR. ELMB Sync is also available to use with HDMI 2.1 VRR, if you wish.

HDR (High Dynamic Range)

The ideal HDR (High Dynamic Range) monitor can simultaneously display very deep dark shades and very bright light shades, with an excellent range of shades between these extremes. From very muted shades to eye-catching vibrant shades. Per-pixel illumination would ideally be used (backlightless technology such as OLED, for example). Failing that, a backlight solution such as FALD (Full Array Local Dimming) with a great number of dimming zones is desirable. This allows some areas of the screen to display very bright and brilliant lighter shades, whilst others display very deep and dark content. Colour reproduction is also an important part of HDR. The long-term goal is support for a huge colour gamut, Rec. 2020. A more achievable near-term goal is support for at least 90% DCI-P3 (Digital Cinema Initiatives standard colour space) coverage. Finally, HDR makes use of at least 10-bit precision per colour channel, so its desirable that the monitor supports at least 10-bits per subpixel.

The most widely supported HDR standard for games and movies is HDR10, and that’s what’s supported here. For most games and other full screen applications that support HDR, the ASUS automatically switches into its HDR operating mode when an HDR signal is detected. 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 and monitor 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. This is really just a digital brightness slider, so you lose contrast by adjusting it. The balance of the image was decent when displaying SDR content with HDR enabled – but you lose adjustment or brightness, colour channels gamma and various other settings in the OSD. 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.

To keep things simple we’ll just focus on our two main test titles for this section; Battlefield V and Shadow of the Tomb Raider. We’ve tested these titles on a broad range of HDR monitors and know they’re good for highlighting strengths and weaknesses. The experience described here is really limited by the screen itself and its HDR implementation. Our testing is focused on HDR PC gaming using DisplayPort on an Nvidia RTX 3090, but we made similar observations when viewing HDR video content on the Netflix app. There are some additional points to bear in mind if you wish to view such content. We made similar observations using HDMI on our Nvidia GPU as well. With our AMD GPU, the experience was similar on the contrast side – but saturation levels were pushed up. Some elements appeared oversaturated, particularly for red-biased shades and some green shades. The overall colour representation was closer to how it appeared under SDR using the native gamut, without the appropriate muted look and shade variety that’s intended under HDR. This oversaturated representation would also be provided for HDR content on an HDR compatible games console (which uses AMD graphics hardware). It’s a look some will like, but it deviates from how things are supposed to look under HDR.

As usual under HDR, many settings are inaccessible. You can’t change presets or adjust things like brightness, colour channels or gamma. The monitor offers three distinct HDR settings; ‘ASUS Cinema HDR’, ‘ASUS Gaming HDR’ and ‘Console Mode’. Using our Nvidia GPU, these settings did not affect the output – at least on our early sample of the monitor. Usually they’d have an effect on the image, particularly the ‘Cinema HDR’ setting that tends to deepen things up at the expense of subtle detail levels. We usually find ‘Gaming HDR’ is the best balanced and closest to the expected HDR output. The monitor doesn’t apply a sharpness filter under HDR like some models do, with the high native pixel density instead providing a good sharpness level without an artificially oversharpened look. On our AMD GPU (or if you connect run the monitor under HDR on a compatible games console) it locks itself into ‘Console Mode’ with the more strongly saturated appearance we described in the previous paragraph.

The ASUS VG28UQL1A is VESA DisplayHDR 400 certified. This is the lowest level of VESA DisplayHDR certification, so only a basic HDR experience is offered. One area that the VESA DisplayHDR 400 requirement isn’t very strict about is colour gamut, compared to higher tiers which require at least 90% DCI-P3 coverage. For this screen we measured 87% DCI-P3, shown in the gamut representation below. The red triangle shows the monitor’s colour gamut, the blue triangle DCI-P3 and green triangle sRGB. With reasonable DCI-P3 coverage plus strong consistency, the monitor was able to provide decent vibrancy where the developers wanted it to be. Roaring and rich orange and yellow flames and some fairly lush-looking deep forest greens where evident on both titles. And some of Lara Croft’s dresses on Shadow of the Tomb Raider showcased some quite eye-catching green and blue shades, too. Some of these shades were well beyond the sRGB colour space. Even greater DCI-P3 coverage or even some extension beyond, encroaching more on Rec. 2020, would have invited further depth and vibrancy to such elements. As would greater dimming precision for the backlight. More muted shades such as certain skin tones, dusty browns and light green vegetation appeared appropriately muted. We didn’t observe the yellow push for some yellowish greens or reddish push to certain skin tones, woody or earthy browns that we observed under SDR. Things were better balanced and more neutral in that respect, because it’s no longer the smaller sRGB colour space the developers are targeting.

Colour gamut 'Test Settings'

The HDR10 pipeline makes use of 10-bits per colour channel, which this monitor supports via 8-bit + FRC. This enhanced precision not only helps the monitor put its generous gamut to appropriate use, it also aids the nuanced shade variety at the low and high end. At the low end (dark shades) there’s a natural uplift of detail, with a superior variety of closely matching shades. Very different to the ‘flooded’ look you’d get if you were to lift out such detail without this increase in shade variety – such as a low-end gamma enhancement under SDR. At the high end (bright shades) there were smoother progressions of shades, with finer gradients used for smoke and weather effects for example. The image below is taken from one of our favourite scenes to test HDR on Shadow of the Tomb Raider. Remember that the photo is purely for illustrative purposes and in no way represents how the monitor appeared running HDR in person.

This scene showcased the nuanced shade variety and the advantages well there for darker shades, with a good mixture of shade depths. VESA DisplayHDR 400 doesn’t require local dimming for the backlight. But as explored earlier, the ASUS includes a ‘Dynamic Dimming’ setting which is enabled by default under HDR. This enables 8 edge-lit dimming zones on the backlight. These zones are arranged as vertical bands, from left to right. As with SDR, this didn’t perform miracles with its very limited number of dimming zones. With the setting disabled the backlight stays at close to its maximum level regardless of the content displayed, giving a flooded look to darker shades. With the setting enabled, there was a definite situational boost to contrast, which worked well for some scenes. It certainly provided good depth where a dimming zone was covered by dark to medium content. As with SDR, the dimming zones were very reactive even with modest changes in average shade brightness for content covering that zone. Additional digital compensation was used (‘pseudo zones’) as part of a rather ‘dynamic’ experience – and perhaps to try to smooth out some of the abrupt and frequent zonal brightness changes. But this was certainly no substitute for more physical dimming zones and was at times rather distracting. You were made quite aware of the dimming zones and the fluctuations in brightness in some scenes, particularly less complex scenes with large areas of uniform shade or texture.

The peak luminance we recorded (422 cd/m²) was rather limited by HDR standards, so bright elements such as the light streaming in from above and the glint on the water surface were far from as brilliant or eye-catching as they could be. Superior local dimming precision can also help the array of closely matching bright shades appear more natural and life-like. The 10-bit colour processing aids this to some extent, but matching this with appropriate luminance control is also helpful. And as we noted, we observed some crushing together of shades at the high end. The overall depth of medium to darker shades simply wasn’t as strong as it could be, either. Although it was certainly improved for some scenes by a bit of local dimming. The section of video review below runs through the HDR experience using various scenes in Shadow of the Tomb Raider.

The ‘4K’ UHD experience

Our article on the ‘4K’ UHD resolution explores the experience on the desktop, watching video content and playing games. As with the screen used when the article was written, the VG28UQL1A features a 28” screen with UHD resolution – yielding a pixel density of 157.35 PPI (Pixels Per Inch). This is a high pixel density, so many users will want to use some degree of scaling when they’re on the desktop. We were actually very happy to use the monitor without scaling and enjoyed the experience, from our usual viewing distance of ~70cm. This yielded an excellent amount of ‘desktop real estate’. But text and various other elements were very small indeed, which took some getting used to. We found 125% scaling offered a good balance as well, providing a good level of ‘desktop real estate’ – more than you’d get on a 27” 2560 x 1440 (WQHD or 1440p) model. Everybody will have their own preferences for scaling level, but for elements that scale cleanly (most content now does) applying scaling doesn’t affect the clarity or crispness imparted by the high pixel density. The following images show the screen on the desktop natively (100%, no scaling) and a small amount of scaling applied (125%). The article linked to earlier includes further analysis using a broader range of scaling settings.

Note that these images are just for illustrative purposes and don’t accurately reflect how the monitor appears in person. Banding and patchiness on solid backgrounds are artifacts in the image, not observed in person.

This excellent pixel density provides a good detailed and clear appearance to suitably high resolution image content, ‘4K’ UHD video content and games. Even older game titles or with detail levels turned down, you still benefit from a definite clarity and definition to objects and their edges. This is particularly noticeable when they’re viewed in the distance on the game. Having more eye-candy turned on is the icing on the cake, with impressively crisp and detailed-looking lighting and particle effects and high resolution textures benefiting from the high pixel density. The difference between this and a model with significantly lower pixel density, such as 27” WQHD, was very clear to us. The benefits are easier to appreciate in motion due to the high refresh rate (at suitably high frame rates), too. A combination we very much enjoy and found to be a competitive advantage, with enemies appearing more distinct from the background and easier to spot in the distance. The images below show the monitor in action on various game titles. Again, the images are just for illustrative purposes and don’t accurately reflect how the monitor appears first hand.

Interpolation and upscaling

The 3840 x 2160 (‘4K’ UHD) resolution is graphically demanding, so it may be desirable to switch to a lower resolution for some games or graphically intensive work. This may also be necessary due to the system you’re using, such as a games console that may not run at the ‘4K’ UHD resolution. The monitor can use an interpolation (scaling) process to map lower resolutions such as 1920 x 1080 (‘1080p’ Full HD) onto all 3840 x 2160 pixels at refresh rates including 60Hz and 120Hz. For the 2560 x 1440 (WQHD or 1440p) resolution, interpolation is also supported at 144Hz. To ensure the monitor rather than GPU is handling the scaling process, as a PC user, you need to ensure the GPU driver is correctly configured so that the GPU doesn’t take over the scaling process. For AMD GPU users the monitor will handle the scaling by default, when gaming at non-native resolutions. Nvidia users should open the Nvidia Control Panel and navigate to ‘Display – Adjust desktop size and position’. They should ensure that ‘No Scaling’ is selected and ‘Perform scaling on:’ is set to ‘Display’ as shown below.



The monitor has an ‘Aspect Control’ setting in the ‘Image’ section of the OSD (explored in this section of the OSD video). This offers a few options but can only be adjusted if VRR is disabled and if the monitor is running at a resolution and refresh rate combination that supports interpolation. The default setting is ‘Full’ which will use an interpolation process to use all pixels on the display, regardless of the source resolution. The monitor uses this ‘Full’ setting if VRR is enabled, even though the control is locked so other options are unavailable. There’s a ‘4:3’ setting which will enforce a 4:3 aspect ratio for supported resolutions and a ‘16:9 (24”W)’ setting which will emulate a 24” 16:9 experience. When running the monitor at either 1920 x 1080 (Full HD or 1080p) or 2560 x 1440 (WQHD or 1440p), the interpolation process provided a moderate but not extreme softening to the image. A lack of sharpness compared to viewing a screen of this size with the same resolution natively, but without the ‘soft focus’ look of some models using interpolation. For the WQHD resolution this softening was somewhat less noticeable than with the Full HD resolution. Depending on preset used, a ‘VividPixel’ option is available which can be increased to add a sharpness filter. We found the look with this set one level up from the default of ‘50’ to ‘60’ provided a somewhat over-sharpened or ‘processed’ look. Some may prefer this look, but this setting isn’t available in the best-balanced ‘Racing Mode’ preset anyway. We would’ve preferred more flexibility in ‘Racing Mode’ and also finer control of sharpness than offered with ‘VividPixel’. But the native interpolation performance was still reasonable, at least.

As usual, if you’re running the monitor at 3840 x 2160 and viewing 1920 x 1080 content (for example a video over the internet or a Blu-ray, using movie software) then it is the GPU and software that handles the upscaling. That’s got nothing to do with the monitor itself – there is a very small amount of softening to the image compared to viewing such content on a native Full HD monitor, but it’s slight and shouldn’t bother most users.

Video review

The video below shows the monitor in action. The camera, processing done and your own screen all affect the output – so it doesn’t accurately represent what you’d see when viewing the monitor in person. It still provides useful visual demonstrations and explanations which help reinforce some of the key points raised in the written piece.

Timestamps:
Features & Aesthetics
Contrast
SDR Dynamic Dimming (Desktop)
SDR Dynamic Dimming (In-game)
Colour reproduction
HDR (High Dynamic Range)
Responsiveness (General)
Responsiveness (VRR)

Conclusion

The 3840 x 2160 (‘4K’) UHD resolution and 28” screen size of the ASUS VG28UQL1A provided a very strong pixel density, useful for work and desirable for play. The monitor has a rugged appearance with plenty of robust matte black plastics. This provided quite a solid feel to the overall screen, whilst full ergonomic flexibility was also provided. The OSD was also feature-rich, well laid out and responsive with plenty of gaming-focused additions. Including a very clear refresh rate indicator, a range of crosshairs and a well-implemented ‘Dark Boost’ gamma enhancement feature.

The IPS-type panel delivered strong colour consistency. There was a fair amount of extension beyond the sRGB colour space but nothing extreme. This delivered quite a vibrant look to things without strong oversaturation, whilst an sRGB emulation setting with adjustable brightness provided a toned-down look to things. The contrast was in-line with our expectations for the panel type – static contrast a touch below or above the specified 1000:1 depending on settings used and moderate ‘IPS glow’. A ‘Dynamic Dimming’ feature was included for use in SDR as well as HDR. This provided aggressive brightening and dimming of the 8-zone local dimming solution, with additional ‘pseudo zones’ to try to perhaps try and make the progressions seem gentler. In some scenes this worked well, in others it was quite distracting. Outside of that the luminance was quite limited by HDR standards and colour gamut not terribly generous. But enough to give a different look to things and provide nice variety.

The high refresh rate response performance was impressive, with rapid pixel responses achieved without excessive overshoot. And good low input lag to go with it. Things were less well tuned for lower refresh rates such as 60Hz, though. As despite the inclusion of some degree of variable overdrive, overshoot levels increased to moderately high levels even using the lowest response time setting. This was the case with a static refresh rate or in a VRR environment. The VRR support itself was very flexible, though with FreeSync Premium, ‘G-SYNC Compatible Mode’ and HDMI 2.1 VRR. The technologies worked as expected without unwanted interruptions such as unexpected stuttering, tearing or flickering. ELMB Sync also allowed this VRR experience to be carried over into a strobe backlight setting – not a perfectly implemented one, but still a combination some will enjoy. Overall, we felt this monitor offered a strong performance and a good feature set. Much like the Acer XV282K KV and others sharing the panel like the Gigabyte M28U, our main criticism is the inability to provide low-overshoot output at reduced refresh rates. There are a few relative strengths and weaknesses of the Acer and ASUS as covered in this thread on our forum, but the overarching experience is the same and one some users will very much enjoy.

Positives	Negatives
Strong colour consistency, fairly vibrant output due to gamut and an sRGB emulation mode with adjustable brightness	DCI-P3 and Adobe RGB coverage insufficient for work within those colour spaces, some gamma kinks on our unit and lower than ideal sRGB coverage with emulation mode
Fairly direct light emission with little layering from screen surface and reactive local dimming providing a good situational boost to contrast	Moderate ‘IPS glow’. Aggressive 8-zone local dimming potentially annoying. Peak luminance and gamut quite limited for HDR, with different output different for AMD vs. Nvidia
Impressively fluid 144Hz (and 120Hz) experience, low input lag and flexible VRR support without unexpected issues	Overshoot becomes noticeably stronger at reduced refresh rates, higher 60Hz input lag
Tight pixel density can deliver excellent detail, clarity and ‘on-screen real estate’. Good ergonomic flexibility with a fairly robust feel	Chunky plastics won’t be to everyone’s taste, availability very limited at time of review

The bottom line; a responsive and feature-rich ‘4K’ model with consistent and fairly vibrant colour output – performance at lower refresh rates affected by increased overshoot.PC Monitors

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