ViewSonic XG2402

Interlace pattern artifacts

Some models exhibit what we refer to as ‘interlace pattern artifacts’, particularly but by no means exclusively those with high refresh rates. These artifacts can also be referred to as ‘inversion artifacts’ or ‘scan lines’. Sometimes static interlacing patterns are visible, whereby shades are broken up into thin (usually vertical) lines that alternate between a slightly lighter and slightly darker than intended variant of the shade. Dynamic interlacing patterns may also be observed, which take many forms and sometimes appear as a sort of mesh, grid or lines or ‘interference’ when you observe motion on the monitor.

The XG2402 did not exhibit any noticeable static interlace pattern artifacts, but did exhibit dynamic interlace patterns. If you observed movement on the screen at certain (slow to moderate) paces of action you could see the image appear to break up into a faint mesh pattern. This was a very faint and fine pattern that not everybody would notice and few would find distracting, but we thought we’d mention it for completeness. This occurs regardless of refresh rate, FreeSync or ‘Rampage Response’ setting. The image below is a pursuit photograph taken using the UFO Motion Test ‘Moving Photo’ page and highlights this pattern (see in particular the top left region). Again, note that it’s a very fine and faint pattern in reality.

Responsiveness

Input lag

A sensitive camera and a utility called SMTT 2.0 was used to assess the input lag of the XG2402. It was compared with a number of monitors of known latency, with over 30 repeat readings taken to try to maximise accuracy. Using this method we calculated 3.16ms (~ ½ a frame at 144Hz) of input lag. With the monitor running at 60Hz, we calculated 11.74ms of input lag. These values take into account both the element of input lag you ‘see’ (pixel responsiveness) and the element you ‘feel’ (signal delay). It indicates a very low signal delay at 144Hz, which even sensitive users should find absolutely fine. Note that we have no way to accurately measure input lag when FreeSync is doing its thing.

Perceived blur (pursuit photography)

Our responsiveness article explores the factors which affect responsiveness of a monitor. Chief amongst these is the concept of ‘perceived blur’, contributed to by both the pixel responsiveness of the monitor and the movement of your eyes as you track motion on the screen. This second factor is generally the dominant contributor to perceived blur on modern monitors. Both aspects of perceived blur can be accurately captured using a photography technique explored in the article; ‘pursuit photography’. This uses a moving camera rather than a static one to capture a snapshot of motion on the screen, giving a good idea of what the eye actually sees at that given moment in time when observing motion on the screen.

The images below are pursuit photographs taken using the UFO Motion Test for ghosting, with the test running at its default speed of 960 pixels per second. This is a good practical speed for taking such photographs at and demonstrates both elements of perceived blur nicely. The UFOs move across the screen from left to right at a frame rate matching the refresh rate of the display. The first set of photos shows the results with the monitor set at 60Hz and the second with the monitor set at 144Hz. All three rows of the test (dark, medium and light background) are used to showcase a range of different pixel transitions. The full range of ‘Rampage Response’ (pixel overdrive) settings are also tested – this can be selected in the ‘CUSTOM’ presets as noted earlier. For 60Hz and 144Hz a capture from a reference monitor is shown, namely the Dell S2417DG, giving an indication of what things look like without pixel responsiveness really being a limiting factor. We’ve also included the older ViewSonic XG2401 as a 144Hz reference, running with its optimal pixel response time setting.

The images above were captured with the monitor set to 60Hz. The UFO appears broad and quite blurry, indicating a moderate amount of perceived blur due to camera (eye) movement. Behind the UFOs you can see varying degrees of trailing, caused by suboptimal pixel responses. There is a bit of a powdery trail behind the object using the ‘Standard’ setting. This is reduced significantly using the ’Fast’ setting, which brings things in-line with the reference shot. The ‘Faster’ setting slightly reduces the trailing again, although this is marginal. It also introduces a small amount of overshoot (inverse ghosting), visible most clearly for the dark background (top row) as a slightly darker trail behind the UFO cockpit. It’s still very faint in this example. The ‘Ultra Fast’ setting makes the overshoot a bit more pronounced, but by no means extreme. It eliminates any conventional trailing behind the UFO with the dark background. The ‘Fastest’ setting, meanwhile, introduces far more obvious overshoot with brightly coloured trailing behind the object for the dark and medium backgrounds in particular. Given that ‘Fast’, ‘Faster’ and ‘Ultra Fast’ all perform well at 60Hz, it’s likely users will find any of these settings to be decent. The tolerance to a small amount of trailing vs. a small amount of overshoot may be the deciding factor. Note that the overshoot was a bit more obvious for some transitions not shown here, even with the ‘Faster’ setting.

With the refresh rate increased to 144Hz, as shown above, the perceived blur is massively reduced. The UFO appears narrower and more sharply focused, with crisper details. There is again some trailing behind the object in places due to suboptimal pixel responses, although this is generally very slight. With the ‘Standard’ setting you can see a faint powdery trail behind the object, particularly for the dark and medium backgrounds. This is similar to the XG2401 reference shot when using its ‘Standard’ response time setting which we consider optimal on that model. The ‘Fast’ setting reduces this trailing significantly, so it is as good as non-existent. There is just the faintest hint of it, for example behind the UFO body with the dark background. There is also a tiny amount of overshoot behind the UFO with the lightest background, appearing as a very faint (barely perceptible) shadow. The ‘Faster’ setting intensifies this overshoot slightly, most noticeably for the dark background. The very small hint of conventional trailing there is replaced with overshoot. The ‘Ultra Fast’ setting increases the overshoot without bringing any visible benefits, whilst the ‘Fastest’ setting brings with it rather intense overshoot. Obvious bright and colourful trails are present behind the object. From this analysis it would seem that ‘Fast’ is optimal, with ‘Faster’ also a decent bet. In practice we found both settings quite similar, although did notice the slightly increased overshoot in places for ‘Faster’ without noticing any benefits. We therefore settled for ‘Fast’ during our testing, which is very well optimised indeed and as good as we’ve seen from any 144Hz model really.

Note: The ‘Monitor Hertz Cap’ did not function correctly on either the AMD or Nvidia GPU we tested. It did not change the Windows (or graphics driver) setting and instead simply caused obvious frame skipping and a generally uncomfortable experience if set to something lower than what Windows was set to. This sort of setting would be useful if it actually changed the refresh rate properly, but that didn’t seem to be the case. You can leave this at ‘Native(144Hz)’ and select any refresh rate available in Windows, your graphics driver or in-game without issue.

Responsiveness in games and movies

On Battlefield 1 (BF1) responsiveness was excellent, where the frame rate kept up with the 144Hz refresh rate. With the monitor pumping out up to 2.4 times as much visual information every second as a 60Hz monitor, there was a definite precision and fluidity when interacting with the game. This is something we like to call ‘connected feel’, and it was further aided by the very low latency of this monitor. The refresh rate also significantly reduced perceived blur, which was complimented very well by extremely snappy pixel responses. As demonstrated in the pursuit photographs earlier, there was very little to speak of in the way of trailing or overshoot – it was a very ‘clean’ 144Hz performance. This was true across the broad range of transitions on this title, meaning that the level of perceived blur was about as low as you’ll see on a 144Hz sample and hold monitor, without any nasty distractions. There was the smallest trace of faint overshoot and powdery trailing here and there, but even when we were specifically looking out for it we didn’t find it obvious. This low level of perceived blur helped make tracking and engaging enemies that bit easier and made it much easier to focus on the game world during rapid movements than on 60Hz models. Some users would very much appreciate the competitive edge that this can bring, whilst others would simply find it a more enjoyable or even comfortable way of playing.

On Dirt Rally the consistently strong pixel responses were again demonstrated. The track and elements of the environment retained superior clarity during sharp cornering or even more gentle manoeuvring, making the experience more pleasant and less dizzying than on a 60Hz model. Whilst the low latency was ‘nice’, we didn’t find it as beneficial as on FPS titles such as BF1. That says more about the level we play this sort of game at – we’re keyboard and mouse rookies. If you’re really into racing games and have an appropriate controller, you’d find the snappy responses to user input and the excellent fluidity of the experience very enjoyable. We also tested our Blu-ray test titles and didn’t find any weaknesses in the monitor’s performance. The ~24fps at which the titles run severely limited their visual fluidity and also the required speed of pixel responses. Even so, no weaknesses such as obnoxious overshoot, trailing or after images were observed. The fact that this frame rate divides neatly into the refresh rate (144Hz) also helped. The monitor can also be set to run at various static refresh rates that might match some other content, including 25Hz, 30Hz and 50Hz.

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FreeSync – the technology and activating it

AMD FreeSync is a variable refresh rate technology, an AMD-specific alterative to Nvidia G-SYNC. With this technology, the monitor adjusts its refresh rate dynamically, where possible, to match the frame rate being outputted by the GPU. Both the responsiveness article and the G-SYNC article linked to previously explore the importance of these two elements being synchronised. Essentially, a mismatch between the frame rate and refresh rate can cause stuttering (VSync on) or tearing and juddering (VSync off). An additional benefit of FreeSync is reduced latency compared to running with VSync on, within the variable frame rate environment in which it operates.

FreeSync requires a compatible AMD GPU such as the Club3D Radeon R9 290 royalAce used in our test system. There is a list of GPUs which support the technology here, with the expectation that future AMD GPUs will also support the feature. The monitor must support ‘VESA Adaptive-Sync’ for at least one of its display connectors, as this is the protocol that FreeSync uses. The XG2402 supports FreeSync via DP 1.2a (‘DP 1.2a+’) as well as HDMI on compatible GPUs. AMD’s recent drivers include Radeon Settings, which makes activation of the technology very simple. It should be automatically enabled once the monitor is connected and ‘AMD FreeSync’ is set to ‘On’ on the ‘Gaming Settings’ section of the OSD. You can check its status by opening ‘AMD Radeon Settings’ and clicking on ‘Display’. You should then ensure that the first slider, ‘AMD FreeSync’, is set to ‘On’. If you hover over this, it will also report the variable refresh rate display supported by the display. Note that the image below is for a different monitor and is just used as an example here.



The ViewSonic 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. This feature is used regardless of VSync setting, so it’s only above the ceiling of operation where the VSync setting makes a difference.

VSync is configured in the ‘Gaming’ section of ‘Radeon Settings’, where it is referred to as ‘Wait for Vertical Refresh’. You can either configure this globally under ‘Global Settings’ or for each game individually. 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. The fifth and final option, ‘Enhanced Sync’, 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 (e.g 200fps +) rather than just peaking slightly above it.



Note that this monitor does not provide any obvious ‘at a glance’ indication that FreeSync is active, such as a change of power LED colour. However; if you go to ‘Setup Menu’ – ‘Information’ in the OSD you can see if FreeSync is working correctly. If you see the ‘V. Frequency’ change alongside the frame rate, then it’s working properly. If it just stays at the static refresh rate that you set, then it’s because the technology isn’t active. This could be because you haven’t configured it properly in the driver or that the frame rate is simply beyond the ceiling for FreeSync operation (i.e. 144fps+). Finally, it’s worth remembering 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.

FreeSync – the experience

We ran various titles to test the FreeSync capabilities of this monitor, but found that it worked in much the same way on all of them. If any issues did happen to occur on one title but not another, it’s going to be an issue with the GPU or GPU driver (or perhaps the game itself) rather than the monitor. We will therefore be focusing on Battlefield 1 (BF1) for this section, which offers plenty of flexibility with its graphics options and therefore allows a broad spectrum of frame rates (and refresh rates) to be tested. Using decent but not extreme graphics settings allowed our Radeon R9 290 to pump out decent frame rates. There was a bit of fluctuation, particularly where the action intensified or for whatever reason the scene became graphically more complex. There were plenty of drops below 144fps, even if just slightly. Even these slight drops below 144fps caused stuttering (VSync on) or tearing and juddering (VSync off). Sensitivity to this varies and not everybody would find this as jarring as we did, particularly at what are still relatively high frame rates.

If we ramped up the graphics settings, the frame rate took a hit. With the ‘Ultra’ preset, for example, it would sit only a little above 100fps at times, but others would dip below this. We again found FreeSync beneficial in terms of removing tearing and stuttering from what would otherwise be frame rate and refresh rate mismatches. However; even with FreeSync active, we still ‘noticed’ these dips in frame rate due to a decrease in ‘connected feel’ and an increase in ‘perceived blur’. This became more extreme at even higher graphics settings, for example when the ‘Resolution Scale’ slider was increased, as the frame rate dropped further. As 100fps became a distant memory and the frame rate dipped as low as half of that, the ‘connected feel’ and perceived blur became noticeably worse. Without FreeSync, stuttering and tearing is (in our view) quite obvious at such low frame rates. So the technology was still nice to have, even if higher frame rates would have been preferred. At times the frame rate dropped below 48fps, which is below the 48fps (48Hz) floor of FreeSync operation on this model. LFC (Low Framerate Compensation) took over here, keeping the monitor at a refresh rate that’s a multiple of the frame rate. This kept stuttering and tearing from mismatches between the two at bay; although ‘connected feel’ was very poor and perceived blur rather high. There was also a juddering quality at particularly low frame rate, a symptom of the low frame rates themselves and nothing FreeSync can rectify.

On many FreeSync models we observe that overshoot (inverse ghosting) becomes more pronounced as frame rate reduces. This is only the case with the technology active and relates to a drop in refresh rate on the display rather than just frame rate of the content. G-SYNC models tend to have their pixel overdrive suitably tightened or slackened off to suit different refresh rates. Fortunately, we didn’t notice any troubling overshoot on the XG2402 even at these reduced refresh rates. We also tested FreeSync whilst watching some video content, with some benefits offered there as well. If viewing full screen using video software or certain web browsers, the monitor will set its refresh rate to either match or conform to a multiple of the frame rate of the content. This helps smooth out the juddering (stuttering) that results from the two not aligning in this way. You don’t need to keep manually adjusting your refresh rate depending on whether the content was 24fps, 30fps, 50fps or 60fps etc. to minimise juddering. We can confirm that this worked with Microsoft Edge and Google Chrome, but not on Mozilla Firefox. This could be dependent on the version of the web browsers used, however.

Video review

The video below summarises some of the key points raised in this written review and shows the monitor in action. The video review is designed to complement the written piece and is not nearly as comprehensive.

Conclusion

We’ve tested many 144Hz monitors, including several which use the now ubiquitous AUO TN panel found in the ViewSonic XG2402. We therefore had a fair idea of what to expect, although there’s more to a monitor than just the panel used. Before even turning the monitor on, we were greeted by a new but somehow familiar design. There were some gentle ‘gaming’ elements (red colouration) but nothing too ‘in your face’. There was that moderately thick single-stage bezel that as good as completely covers the panel border. And there was the robust ergonomically flexible stand that users have come to expect from these sorts of models. The OSD (On Screen Display) controls were particularly tactile on this model, with different buttons shapes corresponding to different functions. We generally prefer joysticks for intuitive navigation through the depths of a monitor OSD, but we found this system worked OK. Of greater importance, of course, was the OSD itself – which is very extensive on this model and offers great flexibility when it comes to tweaking the monitor.

That flexibility came in useful when setting up the monitor. Out of the box colours looked noticeably washed out, with an obnoxiously bright and flooded look. On some models, lowering brightness is about all you can do. On this model, though, the flexibility it gives you in the OSD to tweak gamma helps considerably. You don’t need to resort to properly calibrating the monitor and applying ICC profiles to rectify the ‘out of the box’ gamma handling issues. This flexibility is particularly important to have given the panel used, which has demonstrated awful inter-unit variation in terms of average gamma. The slightly grainy screen surface, ~sRGB colour space and usual TN gamma handling caveats didn’t allow this monitor to pump out overly vibrant or consistent shades. But it was certainly better than what we’ve seen on some models that use the same panel, with a fairly rich look overall.

When it came to contrast, though, there were some pronounced weaknesses which we weren’t expecting from our previous experiences with the panel. The static contrast sat at 550:1 following the corrections made under our ‘Test Settings’. This was not something that any amount of tweaking in the OSD or calibration could rectify, and indeed the contrast never rose satisfyingly above this. Nor did it come close to the specified 1000:1, which we know this panel is capable of. User feedback, including multiple confirmed contrast ratio readings of ~1000:1 (using an X-Rite i1DisplayPro), suggest this was an issue with our particular unit rather than a universal problem. Regardless of this, the monitor was prone to the same contrast weaknesses that affect all TN models. Specifically, that the perceived gamma is lower further down the screen which makes dark shades lighter than intended – making things look a bit flooded and revealing extra detail. And is higher further up the screen, darkening the image and hiding detail too much towards the top of the screen. There was no ‘IPS glow’ to contend with, at least, at that’s something that some users really appreciate.

With all of this said, this monitor was never designed for stellar image quality. It was always about the responsiveness. In in that area, it truly excelled. There was very little 144Hz input lag to speak of, whilst the monitor made excellent use of its high refresh rate. Pixel responses were very snappy indeed and the pixel overdrive both highly flexible and well-tuned. The monitor’s ability to keep the experience free from noticeable conventional trailing or bothersome overshoot was admirable. This is really as good as we’ve seen from this panel in terms of responsiveness and as good as we’ve seen on any 144Hz model really. Another bonus came in the form of AMD FreeSync, which worked as intended on our AMD GPU to rid the experience of tearing or stuttering from frame and refresh rate mismatches. We’re also happy to report that we didn’t notice troublesome inverse ghosting at lower frame rates (and hence refresh rates) with FreeSync active, and that’s something that’s far from guaranteed.

Overall, we found the monitor lived up to our expectations. The build quality and overall design was quite agreeable and there was nothing particularly annoying about the monitor externally. Except perhaps the flimsy cable-tidy loop, but once that’s in position and out of the way it doesn’t really cause much hassle. The flexibility afforded to users in the OSD was also commendable, and quite useful given some of the shortfalls in ‘out of the box’ setup. Following appropriate tweaking things were largely as good as we’d expect in terms of colour reproduction. But the screen we tested did fall short of out expectations in terms of contrast. It seems from extensive user feedback, including from several users who have provided accurate contrast measurements with colorimeters, that this was an isolated issue with our early/pre-production sample and not something that affects retail units. The monitor also gained a lot of brownie points when it came to its responsiveness, as there was really very little to complain about and plenty to praise in that area.

The bottom line; a monitor with excellent OSD flexibility and praiseworthy responsiveness, but some contrast issues on our unit that weren’t expected.

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