Gigabyte M27U

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 to analyse the latency of the M27U. Over 30 repeat readings were taken to help maximise accuracy. Using this method, we calculated 3.80ms (above 1/2 a frame at 160Hz) of input lag and recorded similar values at lower refresh rates including 60Hz. This figure is influenced by both the element of input lag you ‘see’ (pixel responsiveness) and the main element you ‘feel’ (signal delay). It indicates a low signal delay which most users should find acceptable. 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 various factors affecting monitor responsiveness. A key concept explored is ‘perceived blur’, contributed to by both the pixel responses of the monitor and movement of your eyes as you observe motion on the screen. This second factor dominates on modern monitors, but both factors play an important role. A photography technique called ‘pursuit photography’ is also described, using a moving rather than stationary camera to capture motion on the screen in a way that reflects both parts of perceived blur. Rather than only 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 160Hz using various ‘Overdrive’ settings; ‘Off’, ‘Picture Quality’, ‘Balance’ and ‘Speed’. The final column shows the Acer XV282K KV for reference, where possible, which is quite fast and provides a competent performance at 120Hz+. Intermediate refresh rates (144Hz and 150Hz) were also tested on the M27U and they were some way between 120Hz and 160Hz as you might expect – with 150Hz rather similar to 160Hz. So if the 160Hz OC doesn’t work well with your system, you can expect a very similar experience to what is covered here at 160Hz.

An additional overdrive setting called ‘Smart OD’ is included which switches over to different overdrive settings depending on refresh rate. We found this stop to inappropriately high levels in most cases, for example ‘Speed’ at some higher refresh rates and ‘Balance’ at some lower refresh rates. It would’ve been much better if this stuck to ‘Picture Quality’ for most of the range and perhaps ‘Off’ for double digit refresh rates, or at least below 80Hz or so. 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. Trailing is observed in places behind the UFO, due to weaknesses in pixel response time or overshoot (inverse ghosting) from aggressive pixel overdrive. With overdrive ‘Off’ there’s a bit of ‘powdery’ trailing, visible mainly behind the red UFO body for the dark background (top row) and medium background (middle row). And to a lesser extent, for the light background (bottom row). The ‘Picture Quality’ setting eliminates this for the transitions shown here, replacing it with mild to moderate overshoot (inverse ghosting). Which stands out a bit due to being slightly brighter than the background shade (‘halo trailing’) – and with a somewhat inky quality behind the cockpit for the dark background (‘dirty trailing’). This overshoot is intensified significantly using ‘Balance’ and even more so using ‘Speed’. The reference screen appears some way between ‘Picture Quality’ and ‘Balance’ in terms of overshoot levels. We consider ‘OFF’ optimal for 60Hz, but depending on overshoot sensitivity ‘Picture Quality’ might be preferred. 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. To the eye the black lines which separate the segments of the UFO are less blended than they appear in the photos at 120Hz and above, so segmentation is more distinct. The pixel response requirements for a good performance here are significantly increased. With the ‘OFF’ setting the ‘powdery’ trailing behind the UFO is quite distinct, including a reasonably bold but not massively extended trail behind the red UFO body for the dark and medium backgrounds but also some trailing behind the UFO body there. The ‘Picture Quality’ setting cuts this down quite effectively, with a little remaining and a touch of overshoot introduced. Observing a broader range of transitions (as we do shortly) there were some transitions showing somewhat stronger overshoot than shown here, but nothing particularly eye-catching. The ‘Balance’ setting provides a further pixel response speed boost but intensifies overshoot – for some transitions not shown here it’s rather bright and eye-catching. The ‘Balance’ setting performs quite similarly here to the reference screen. The ‘Speed’ setting further intensifies the overshoot. We consider ‘Picture Quality’ optimal for 120Hz, though again personal preferences vary.

At 160Hz, above, the UFO appears a bit narrower with somewhat improved definition. Remember the segmentation is more distinct than it appears in the photos to the eye – to the eye there are distinct black lines, but the white notches can’t be counted. This reflects a slight reduction in perceived blur to eye movement – not as significant as the initial boost from 60Hz to 120Hz as this is not a further doubling of refresh rate. There’s a bit of an increase in pixel response requirements coming from 120Hz, though relative performance of the overdrive settings is similar. We consider ‘Picture Quality’ optimal at 160Hz, though some may prefer ‘Balance’ depending on overshoot sensitivity as it slightly cuts down on ‘powdery’ trailing (though does not eliminate it) with increased overshoot levels.

The monitor includes a setting called ‘Aim Stabilizer Sync’, which can be used with VRR active as well if you wish (hence the ‘Sync’ part). This is a strobe backlight setting which forces the backlight to flicker in sync with the refresh rate of the monitor. 100Hz, 120Hz, 144Hz and 160Hz (or 150Hz if not using the OC) can be selected. This acts as the static refresh rate, or if using VRR as the ceiling of operation. Sensitivity to the 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, 120Hz and 160Hz using ‘Blur Reduction’. Intermediates (144Hz and 150Hz) were again assessed and performed some way between 120Hz and 160Hz as you might expect but overall quite close to what is shown at 160Hz. ‘Overdrive’ is locked and can’t be adjusted with ‘Aim Stabilizer’ in use.

We tested ‘Aim Stabilizer Sync’ with VRR enabled and disabled (including in the OSD and graphics driver) and didn’t observe any differences in this test. Including during careful side by side assessment of pursuit photos.

With ‘Aim Stabilizer Sync’ active, above, the main object appears significantly narrower with more detail apparent, particularly as refresh rate is increased. By 160Hz the white notches are particularly distinct and easy to count – by eye the segmentation is more distinct and the black lines are clearer than shown here at all refresh rates. But still sharpest at 160Hz. There are some repetitions of the object which can broadly be termed ‘strobe crosstalk’, clearest for the dark background. It appears in front at 100Hz and 120Hz, but only behind at 160Hz. It’s important to note that strobe crosstalk varies at different areas of the screen. Not all areas refresh simultaneously, so its appearance can differ depending on how high up or low down on the screen movement is being observed. This repetition of the object has a distinct magenta to red fringe, very clear for the dark background, somewhat visible for the medium background and fainter but still there for the light background. This is linked to the use of KSF phosphors, which is extremely common on wide gamut LCDs, and their relatively slow rate of decay. Additional trailing can be observed behind the UFO, mainly as conventional trailing at 160Hz and more as overshoot at lower refresh rates.

Considering the experience using ‘Aim Stabilizer Sync’ more broadly with VRR disabled, at a static 160Hz, we observed moderate strobe crosstalk in places. Quite bold repetitions of the object were visible for brighter shades against darker to medium backgrounds. This was strong for quite a few transitions just above centre, so within the central region of the screen you’ll mainly observe when playing FPS games for example. It was even stronger towards the top and bottom of the screen. There was also moderate overshoot in places, stronger for some transitions than observed using Test UFO with quite bright ‘halo’ trailing observed. This became more prominent at reduced refresh rates. Brighter objects with straight edges against a contrasting background and small bright objects, including in-game text, invited obvious fringing and colourful flashes. This included magenta to red and sometimes other shades such as cyan creating a distinct fringe and flashes when observing movement. These colourful flashes were observed more broadly when simply moving the eyes across the screen when brighter content was present, not just for brighter objects with straight edges against a contrasting background or smaller bright objects. The colourful fringes and flashes are linked to the use of KSF phosphors on the backlight.

We didn’t find ‘Aim Stabilizer Sync’ worked reliably, with VRR enabled. VRR would sometimes deactivate completely, particularly if the frame rate dipped even briefly into the double digits – even if it returned to a good sustained high number. We observed tearing when this occurred. Outside of this, we observed intense flickering at times, beyond that just from the strobe nature of the backlight. And even if it happened to work ‘correctly’, reduced refresh rates were met with significant increases in overshoot, more obvious colourful flashes (related to KSF phosphors – explored shortly) and associated artifacts as well as some stronger strobe crosstalk. More noticeable than what we’d observe at a similar refresh rate using ‘Aim Stabilizer’ and no VRR. We certainly feel the technology worked better without VRR, but even then we found the weaknesses both distracting and uncomfortable, with the locked moderate brightness adding insult to injury. This is an inflexible setting that doesn’t really perform as well as it should in our view, so even for those who usually like such a setting this might not appeal. For those reasons we won’t be performing further assessment of this setting such as visual strobe crosstalk analysis at different points of the screen.

Responsiveness in games and movies

On various Battlefield titles, with the frame rate keeping up with the 160Hz refresh rate, the monitor offered a fluid experience. With the monitor outputting up to 2.67 times as much visual information as a 60Hz monitor (or this monitor running at 60Hz or 60fps), there was a definite improvement to ‘connected feel’. This describes the precision and fluidity that’s felt when interacting with the game world, which is also aided by the low input lag of the screen. The combination of relatively high frame and refresh rate also greatly decreases the perceived blur due to eye movement, as demonstrated with pursuit photos earlier. This provides a nice competitive edge when gaming, making it easier to keep track of enemies for example. And some will simply find the experience more comfortable when gaming or just using the monitor more broadly. It also complements the excellent pixel density nicely, with a better preservation of detail during motion than at 60Hz.

Pixel responsiveness is also an important factor when it comes to perceived blur, with minor weaknesses highlighted earlier using pursuit photography. This is echoed by a broader range of transitions. Some of the weakest pixel transitions performed by this monitor include bright or highly saturated shades against darker backgrounds and to a lesser extent dark shades against medium-bright backgrounds. We observed ‘powdery trailing’ for such transitions, though this wasn’t extensive or particularly bold. Even these ‘slow’ pixel transitions were performed at reasonable speed, certainly compared to typical VA transitions for similar shades. And faster than some IPS models, too. There was a lighter ‘powdery’ trailing in places for other transitions against more closely matching shades, but this just added a small mask of additional perceived blur. Overall, the monitor provided a competent 160Hz performance – and it was one of low overshoot using our preferred ‘Picture Quality’ setting. The ‘Balance’ setting was a bit more in-line with what we saw on the 28” models, with increased overshoot but reduced ‘powdery’ trailing. This ‘powdery’ trailing was not eliminated, though, and for some transitions we found the overshoot to be a bit eye-catching, so preferred the ‘Picture Quality’ setting.

We made similar observations on Shadow of the Tomb Raider. Here there are lots of darker shades with interspersed bright shades, so the weakest pixel transitions performed by the monitor were observed. The weaknesses were quite minor and there was very little to complain of in the way of overshoot, just slight traces of it here and there. We also observed video content at a range of refresh rates, including ~24 – 30fps content on platforms such as Netflix, Disney Plus and Amazon Prime Video as well as 60fps content on YouTube. There were no real weaknesses from the pixel responses of the monitor, with the main barrier to fluidity being the frame rate of the content itself.

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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 and 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 M27U supports FreeSync Premium Pro 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 ‘AMD FreeSync Premium Pro’ is enabled in the ‘Gaming’ section of the OSD. You should also ensure the GPU driver is setup correctly to use FreeSync – so open ‘AMD Software’, click ‘Gaming’ and click on ‘Display’. You should then ensure that the first slider is set to ‘Enabled’ as shown in the below, which is an example from another monitor. The exact wording used for the toggle in the graphics driver may vary depending on the graphics driver version and input, with references including ‘AMD FreeSync’, ‘Adaptive Sync Compatible’ or ‘VRR’.

If running the monitor at 160Hz and you notice screen blanking, try disabling ‘FreeSync’ in the graphics driver and re-enabling it (or vice-versa if you wish to disable VRR). If this doesn’t work, try doing the same with the ‘AMD FreeSync Premium Pro’ setting in the OSD.



The Gigabyte supports a variable refresh rate range of 48 – 160Hz (48 – 150Hz via HDMI). That means that if the game is running between 48fps and 160fps, the monitor will adjust its refresh rate to match. When the frame rate rises above 160fps, the monitor will stay at 160Hz 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 160fps, 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 >160fps). 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 33fps, for example, the refresh rate would be 66Hz to help keep tearing and stuttering at bay. 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 Software’. Click ‘Gaming’ 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. 157fps) 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 go to ‘Game Assist’ and activate the ‘Refresh Rate’ feature, the monitor will display the refresh rate. This will coincide with the frame rate of the content if the monitor is within the main VRR window. Finally, it’s worth noting 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.

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 or later 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’. Some models are validated as G-SYNC compatible, which means they have been specifically tested by Nvidia and pass certain quality checks. With the M27U 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 ‘FreeSync Premium Pro’ is set to ‘Enable’ in the ‘Gaming’ section of the OSD to use the technology via DP (this enables Adaptive-Sync). 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.

If running the monitor at 160Hz and you notice screen blanking, try disabling ‘G-SYNC Compatible’ in the graphics driver and re-enabling it (or vice-versa if you wish to disable VRR). If this doesn’t work, try doing the same with the ‘AMD FreeSync Premium Pro’ setting in the OSD.



You will also see in the image above that it states: “Selected Display is not validated as G-SYNC Compatible.” This is an example from another monitor, but it’s also the case with the Gigabyte. This means Nvidia hasn’t specifically tested and validated the display, not that it won’t work. And indeed the technology did work as we’d expect it to on our RTX 3090, as explored shortly. Our suggestions regarding use of VSync apply in much the same way as they did with AMD FreeSync, but you’re using Nvidia Control Panel rather than AMD 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 use the ‘Refresh Rate’ feature in the ‘Game Assist’ section of the OSD to display the current refresh rate of the monitor. This will reflect the frame rate if it’s within the main variable refresh rate window. And as with AMD FreeSync, HDR can be used at the same time as ‘G-SYNC Compatible’.

G-SYNC Compatible – the experience

As usual we tested various game titles using ‘G-SYNC Compatible’ and found the experience very similar in all cases. Issues affecting one title but not others would suggest a problem with the game or GPU driver rather than the monitor. For simplicity we’ll just focus on Battlefield titles here. They offer a good range of graphics settings, allowing the full VRR range to be analysed on our GeForce RTX 3090. This is quite a powerful GPU, but the ‘4K’ UHD resolution is demanding and depending on settings it’s common to see dips below 160fps. Without the technology active tearing (VSync off) or stuttering (VSync on) were observed due to a lack of synchronisation between frame and refresh rate. ‘G-SYNC Compatible’ removed such issues by ensuring the two were synchronised, where possible, which is certainly beneficial if you’re sensitive to tearing or stuttering. Regardless of a VRR technology like this being used, reduced frame rates are still seen and felt due to the increase in perceived blur and decrease in ‘connected feel’.

The monitor doesn’t use tightly tuned variable overdrive which would carefully re-tune the pixel overdrive and significantly slacken off acceleration levels as refresh rate drops to avoid increased overshoot. Using the ‘Picture Quality’ setting we prefer to higher refresh rates, there was a distinct increase in overshoot as refresh rate dropped. Particularly as it dropped well into the double digits, for example 50 – 80Hz (50 – 80fps content). Even then, the overshoot levels weren’t extreme – so some will be happy to use the ‘Picture Quality’ setting. But we did find it moderately strong in places with some noticeable ‘halo’ trailing that was quite a bit brighter than the background, so if you’re sensitive to overshoot and frequently running double digit frame rates the ‘Off’ overdrive setting may be preferred. The monitor still offers reasonable pixel responsiveness for such refresh rates using this setting, too. This essentially overshoot-free experience is not something offered by the M28U and similar models we’ve looked at such as the XV282K KV and VG28UQL1A.

‘G-SYNC Compatible’ worked down to the floor of operation of a claimed 48Hz (48fps), below which LFC (Low Framerate Compensation) kicked in. Or at least Nvidia’s version of that, which works in the same way to keep tearing and stuttering at bay be ensuring the refresh rate sticks to a multiple of the frame rate. In our testing LFC sometimes kicked in as high as 55Hz, depending on the frame rate fluctuations occurring. We’ve observed this on quite a few models under VRR and it makes little difference to the experience in practice compared to a strict 48Hz LFC boundary. There was a subtle momentary stuttering when LFC activated or deactivated, something we always observe and not specific to this model. It was much less noticeable than traditional stuttering from frame and refresh rate mismatches, but if you’re sensitive to it and frequently passing the boundary it could be annoying.

HDR (High Dynamic Range)

HDR (High Dynamic Range) on an ideal monitor involves very deep dark shades and brilliantly bright light shades being simultaneously displayed. As well as a broad range of shades between these extremes, including muted pastel shades alongside very vibrant saturated shades. Ideally, per-pixel illumination would be provided (e.g. self-emissive displays such as OLED), or for LCDs a very large number of precisely controlled dimming zones used. A solution such as FALD (Full Array Local Dimming) with a generous number of dimming zones, for example. Such a solution would allow some areas of the screen to remain very dim whilst others show brilliantly high brightness. Colour reproduction is also an important part of HDR, with the ultimate goal being 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. HDR10 is the most widely supported standard used in HDR games and movies and what is supported here.

For games and other full screen applications that support HDR, the Gigabyte M27U automatically switches to its HDR operating mode if an HDR signal is provided. Some game titles will activate HDR correctly when the appropriate in-game setting is selected. Others that support HDR will only run in HDR if ‘Use HDR’ is turned on in Windows, too. Related Windows HDR settings are found in the ‘Windows HD Color settings’ (Windows 10) or ‘HDR’ (Windows 11) section of ‘Display settings’ (right click the desktop). If you want to view HDR movie content, ensure ‘Stream HDR Video’ (Windows 10) or ‘Play streaming HDR video’ (Windows 11) is active. Also note that there’s an ‘HDR/SDR brightness balance’ (Windows 10) or ‘SDR content brightness’ (Windows 11) 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 that only makes changes for SDR content, and you lose contrast by adjusting it. The settings in the OSD are greatly restricted under HDR and the gamma and general balance to the image is off when viewing SDR content, so we’d only recommend activating HDR in Windows if you’re about to use an HDR application that specifically requires it.

For simplicity we’ll mainly be focusing on Shadow of the Tomb Raider here. This is a title we’ve tested on many monitors under HDR and we know it has a good HDR implementation which highlights the strengths and weaknesses of a screen’s HDR capability well. Although our testing focuses on HDR PC gaming with an RTX 3090 connected using DP, similar observations were made 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 also made similar observations using HDMI, which would be used when viewing HDR content on an HDR compatible games console for example. The monitor includes three ‘Picture’ presets under HDR; ‘HDR’, ‘HDR Game’ and ‘HDR Movie’. These perform identically, but you can customise the available settings differently for each of these presets. The usual settings you’d see under SDR such as brightness, gamma and contrast can’t be adjusted. Colour channels are also locked. You can adjust ‘Overdrive’ as usual. There are some unique adjustments available under HDR instead; ‘Dark Enhance’, ‘Color Enhance’, ‘Light Enhance’ and ‘Local Dimming’. We explore these settings in the OSD video and ‘Best Settings’ video (taken from the full OSD video). Our preference is to use the defaults under the ‘HDR’ preset with ‘Local Dimming’ set to ‘High’. The M27U is VESA DisplayHDR 600 certified, which means it gives a slightly enhanced HDR experience compared to many models – though that isn’t saying much. In terms of colour gamut, 90% DCI-P3 coverage is the minimum required for this HDR certification level. The monitor slightly exceeded this, with a measured 91% DCI-P3. This is shown in the representation below, where the red triangle shows the monitor’s colour gamut, the blue triangle DCI-P3 and green triangle sRGB. This gamut allows for a respectable vibrancy level under HDR, with elements such as fires, red lava, brightly painted artifacts and rich forest vegetation looking quite lively. More generous Rec. 2020 coverage (more extension beyond DCI-P3) and superior dimming precision would help add extra depth and saturation, however. Because game developers have extended colour spaces beyond sRGB (namely DCI-P3 and Rec. 2020) in mind, you don’t observe the same oversaturation that you do when using the native gamut of the monitor under SDR. Skin tones, overdone reddish browns, overly bright greens and other elements that were oversaturated under SDR are toned down under HDR.

Colour gamut 'Test Settings'

The monitor also supports 10-bit colour, which can be used efficiently for HDR10 content like this to facilitate the enhanced luminance and shade mapping precision expected under HDR. It helps the monitor put its wide gamut to good use and also enhances the nuanced shade variety. When observing dark shades, for example, there’s a natural uplift in detail that’s very different to the unnatural uplift you can get with an SDR gamma enhancement. When observing brighter shades there are smoother transitions and more natural shade progressions, aiding elements such as smoke, weather effects and various gradients in the game. This enhanced nuanced shade variety really requires strong dimming precision to be properly accentuated, though, and that’s not offered here. The image below shows one of the scenes we particularly like from Shadow of the Tomb Raider under HDR. Remember that the photo is purely for illustrative purposes and in no way represents how the monitor appeared running HDR in person.

This scene helps highlight the aforementioned advantages of the 10-bit precision nicely, with a good mixture of shade depths and good variety. The VESA DisplayHDR 600 level requires local dimming and as covered earlier in the contrast and brightness section, that’s provided here with 8 dimming zones running as vertical bands from the left to right side of the screen. Not to beat around the bush, this is a small number of dimming zones. Tiny when compared to the ~8.3 million pixels of the screen (as a ‘4K’ OLED would have) and very small compared to FALD (Full Array Local Dimming) solutions with typically 336 – 2048 dimming zones. The dimming precision is therefore very limited and the monitor simply can’t handle the intricate mixtures of light and dark shade that are common under HDR. Or add proper definition to closely matching dark and bright shades and really accentuate that nuanced shade variety, either. It still provides a situational boost in contrast to some scenes and is ‘better’ than having universal control of the backlight as one unit. Disabling the setting and having the entire backlight stay at a high level revealed that this setting is certainly useful in many scenes, including the one above. As covered earlier there are a few different levels for the ‘Local Dimming’ setting, with ‘High’ being the most reactive – we set ‘Local Dimming’ to ‘High’ for our subjective testing here. The solution was generally reactive and willing to brighten up or dim down as the overall brightness of content covering the zone changed significantly. If a lot of bright content covered a zone and it suddenly became very dark, the transition was a bit more leisurely. In practice we didn’t find the local dimming here ‘distracting’ in most scenes, but that is certainly dependent on content and sensitivity to the lighting changes.

The peak luminance we recorded (605 cd/m²) was decent by HDR standards and sufficient for the VESA DisplayHDR 600 level, but far from exceptional. For the glint of light on the water surface in the scene above, we measured 245 cd/m² (460 cd/m² with local dimming disabled) with the dimming algorithm holding back due to the shades surrounding the glint. In practice there would’ve been a distinct lack of depth for some of these shades if the monitor brightened up that zone completely. This element shouldn’t be at the absolute maximum a monitor can output as that’s not what the game calls for here, but it certainly highlights the limitation of a small number of dimming zones. Considering the areas to the left including shaded areas of vegetation and rocks, with lots of darker and medium shades, the limited precision was also apparent. The dimming zones did indeed dim here by a reasonable amount and there was less of a ‘flooded’ appearance than with local dimming disabled. But it was still a compromise, with the darker shades given insufficient depth as the zones covering both those and the medium or somewhat brighter content can’t just dim to super low levels. The section of video review below runs through the HDR experience using various scenes from Shadow of the Tomb Raider plus a scene from Battlefield V, for a bit of variety. That’s another game we’ve used extensively on monitors under HDR and know has a good HDR implementation.

The ‘4K’ UHD experience

Our article on the ‘4K’ UHD resolution explores the experience on the desktop, watching video content and gaming. The Gigabyte M27U is a similar size to the screen in the article, featuring a 27” rather than 28” panel with UHD resolution yielding a pixel density of 163.18 PPI (Pixels Per Inch). This is a tight pixel density so without scaling various elements on the desktop including text and UI elements will appear very small. We were happy to use the monitor without scaling and enjoyed that experience from our usual viewing distance of ~70cm, with an excellent level of ‘desktop real estate’ provided. But it certainly took some getting used to and this simply won’t be practical or enjoyable for some people. It’s likely that at least some degree of scaling will be desirable – we found 125% scaling offered a good balance as well, maintaining superior desktop real estate to a 27” 2560 x 1440 (QHD or 1440p) model. Everybody will have their own preferences for scaling level, but for elements that scale cleanly (most content now does) applying scaling or using application-specific zoom doesn’t negatively affect the clarity or crispness provided by the tight 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. Any banding and patchiness on solid backgrounds are artifacts in the image, not observed in person.

This excellent pixel density delivered a pleasing level of detail and clarity to suitably high resolution image content, ‘4K’ UHD video content and certainly games. Even older games or games where graphics settings are turned right down benefit from the resolution in terms of the edge clarity and overall defined look, maintained well as you look into the distance on the game. More graphically rewarding games or where graphics options are turned up, you can benefit from a very crisp and detailed look to high resolution textures, particle effects and lighting for example. We found the difference between this experience and a monitor with significantly lower pixel density (such as 27” QHD) easy to notice, though the initial boost from 27” Full HD to 27” QHD is even more significant. The refresh rate also ensured these benefits were maintained to a better degree during motion than a 60Hz monitor (or this monitor running at 60fps). Some will consider the distinctiveness of enemies from the backgrounds and in particular the maintenance of this distinctiveness even in the distance to be a competitive advantage. 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 and not all systems can run it, so it may be desirable or necessary to run at a lower resolution. The monitor is able to use interpolation (scaling) to display lower resolutions such as 1920 x 1080 (‘1080p’ or Full HD) using all 3840 x 2160 pixels of the display, at various refresh rates including 120Hz and 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 includes various ‘Display Mode’ settings in the ‘Gaming’ section of the OSD, as explored in this section of the OSD video. These are only accessible if ‘AMD FreeSync Premium Pro’ is disabled in the OSD and therefore VRR isn’t used (the option is also greyed out when using HDMI 2.1 VRR). The default ‘Full’ setting uses interpolation to map the source resolution onto all 3840 x 2160 of the display – this is the setting used under VRR. There’s also ‘Aspect’, which will use as much screen space as possible without changing the aspect ratio, avoiding any stretching or distortion for non-16:9 resolutions. There’s ‘1:1’ which is a pixel mapping feature that will only use the pixels called for in the source resolution and fill out the remaining pixels as black space around the image. And finally, a range of settings which will squish the image up and simulate different screen sizes and aspect ratios (22” 16:10 plus 23”, 23.6” and 24” 16:9).

When running the monitor at either 1920 x 1080 (Full HD or 1080p) or 2560 x 1440 (QHD or 1440p), the interpolation process of the monitor provided moderate softening. This was quite pronounced for the Full HD resolution, less so for the QHD resolution. It’s possible to counteract this to an extent by increasing ‘Super Resolution’ in the ‘Gaming’ section of the OSD. However; we found even setting this to ‘1’ gave an unnatural look to the image with obvious over-sharpening and a rough appearance to some aspects. We instead preferred increasing ‘Sharpness’ in the ‘Picture’ section of the OSD to ‘7’ – preferences will vary and some may prefer a different value, such as ‘6’ or ‘8’. This didn’t make things look like a 27” screen running the resolution natively, but it was well balanced and very usable in our view for these non-native resolutions.

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
Colour reproduction
HDR (High Dynamic Range)
Responsiveness (General)
Responsiveness (VRR)

Conclusion

27” ‘4K’ UHD models are very diverse, providing an excellent pixel density and ‘desktop real estate’ potential in a size many are comfortable with and can accommodate on their desk. The detail and clarity benefits of the resolution can be appreciated for both work and play. The monitor offers the usual unassuming look of the series, with lots of matte black plastic plus a few glossy elements – then ‘angular’ stand design is perhaps the most adventurous stylistic element, but it’s still quite compact. Ergonomic adjustment is good but not great, with tilt and height satisfying most people’s needs but lacking swivel or pivot. Though 100 x 100mm VESA mounting is facilitated as an alternative. The OSD is comprehensive and includes the usual adjustments plus a few extras, whilst HDMI 2.1 support and USB-C with well-integrated KVM functionality (albeit with limited power delivery) are also attractive additions.

Colour consistency was strong as expected from the IPS-type panel, combined with quite a generous colour gamut for a good but not extreme dose of extra vibrancy. The gamut didn’t quite reach the advertised spec for DCI-P3 and fell short of what would be required for colour-accurate wide gamut work, however. Gamma tracking wasn’t quite on point, regardless of any reasonable OSD adjustments made, but was certainly ‘good enough’ for general purpose and entertainment usage. An sRGB emulation mode provided closer sRGB gamut tracking but was rather inflexible, including the overdrive mode being locked into ‘OFF’ for no apparent reason. Contrast fell in-line with expectation, with static contrast sitting close to the specified 1000:1 and the expected if not slightly lower than expected ‘IPS glow’. The monitor provided a good brightness adjustment range and boosted itself ‘above average’ for HDR, in-line with the DisplayHDR 600 level it’s certified for. This plus rudimentary local dimming provided a situational contrast enhancement but wasn’t sufficient for a ‘true’ HDR experience. The colour gamut is also somewhat limited by HDR standards, but still sufficient for the HDR tier and beyond what some models with the most basic HDR performance provide.

The monitor proved capable in terms of responsiveness, with low input lag and fairly rapid pixel responses. 160Hz is supported, but this relies on a factory OC which can be flaky with some GPUs and systems and cause signal dropouts – though 150Hz is supported as a good fallback and that offers a similar experience anyway. Unlike for 28” alternatives such as the Acer XV282K KV, ASUS VG28UQL1A and Gigabyte M28U, the monitor provides a low overshoot experience with the right settings. VRR support worked as we’d hope on the Adaptive-Sync side (‘G-SYNC Compatible’ via DP) and using HDMI 2.1 VRR. A strobe backlight setting (‘Aim Stabilizer Sync’) also featured, but the implementation was buggy with VRR active and even without VRR active where performance was more consistent, there were some definite limitations. Overall we feel the M27U is a competent performer that’s priced very well – and with the slight boost to HDR capability and lower overshoot experience compared to many of its 28” counterparts, it’s worth careful consideration.

Positives	Negatives
Good vibrancy and strong colour consistency from the IPS-type panel with fairly generous gamut	Gamma a bit off ‘2.2’ target, imprecise colour channel adjustment, no true wide gamut support and sRGB emulation mode rather restrictive
Reasonable static contrast in-line with expectation with a light to very light matte screen surface preserving clarity and vibrancy relatively well, decent but not exceptional HDR brightness	Moderate ‘IPS glow’ (perhaps slightly lower than average), 8-zone local dimming offers limited HDR contrast enhancement
A well-rounded response experience for up to 160Hz with low input lag, pretty snappy pixel responses without strong overshoot and good plus flexible VRR support	Some slightly slower than optimal pixel transitions, not a true ‘single overdrive mode experience’ (though it might work as such for some), middling strobe backlight implementation
Excellent pixel density for strong detail and clarity plus good ‘desktop real estate’ potential, HDMI 2.1 and USB-C with KVM functionality – and priced very competitively	Construction rather ‘plasticky’ (we prefer a bit of coated metal for the stand, at least), stand lacks pivot and swivel adjustment

The bottom line; a very competitively priced 160Hz-capable ‘4K’ UHD monitor offering strong all-round performance – with a slightly enhanced HDR experience and ‘low overshoot experience’ separating it from competitors.PC Monitors

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