ViewSonic XG2401

Responsiveness

Input lag

A sensitive camera and a utility called SMTT 2.0 was used to assess the input lag of the XG2401, by comparison with various monitors of known latency. Using this method, we calculated 3.38ms (under ½ a frame at 144Hz) of input lag. This was with the monitor set up as per our test settings, so note the ‘Low Input Lag’ mode and ‘Response Time’ settings used. This figure reflects both the element you ‘see’ (pixel responsiveness) and the element you ‘feel’ (signal delay). In terms of signal delay, which is the component of input lag most people are interested in, this monitor is clearly extremely snappy. Note that we do not have the means to accurate assess input lag with FreeSync in operation, but things felt just as snappy to us with it enabled when gaming.

Perceived blur (pursuit photography)

In our responsiveness article we explore the factors which affect the responsiveness of a monitor and how these factors interact. One of the key concepts explored is ‘perceived blur’, which is affected not only by the pixel responses of the monitor but also more significantly by the movement of your own eyes as you track motion on the screen. We also explore a method of photography called ‘pursuit photography’, which allows motion to be captured on a monitor in a way that not only reflects the pixel response behaviour of the monitor, but also accounts for eye (in this case camera) movement.

The images below are pursuit photographs taken using the UFO Motion Test for ghosting. The test is set to run at its default speed of 960 pixels per second, a practical speed for such photography and one which highlights the key components of perceived blur nicely. The middle row (medium cyan) background of the test was used for this analysis. The monitor was set to 60Hz (top row), 100Hz (middle row) and 144Hz (bottom row). It was also tested with its three different ‘Response Time’ settings as shown in different columns; ‘Standard’, ‘Advanced’ and ‘Ultra Fast’. The final column shows a reference screen which is able to perform at both 60Hz (top photo) and 120Hz (bottom photo) without significant additional trailing in these transitions. In other words, representing what things should look like where pixel responsiveness isn’t really a limiting factor. This is a Samsung S27A750D set to full brightness (eliminates PWM) and set to its optimal response time setting for each refresh rate. Note that any interlacing shown in these photos is moiré from the camera, not artifacts present on the monitor itself.

At 60Hz you can see that the object itself appears quite blurred (influence of eye movement). There is also a fair bit of trailing behind the object (influence of pixel responses) using the ‘Standard’ setting. With the ‘Advanced’ setting, the trailing is cut down significantly but replaced by a bit of overshoot (inverse ghosting) due to overly aggressive pixel overdrive. The ‘Ultra Fast’ setting introduces extreme overshoot, with an unmistakable bright inverted trail behind the object.

Moving up to 100Hz, the object in all cases appears less blurred (more sharply focused) which indicates perceived blur due to eye movement decreasing substantially. With the ‘Standard’ response time setting the trail is now a lot shorter than at 60Hz – it is also a lot less noticeable when observing movement on the monitor first hand. With the ‘Advanced’ setting there is again a bit of overshoot, although this is fairly tame for the transitions being shown here. The ‘Ultra Fast’ setting again shows extreme overshoot – and although the overshoot trail is shorter as you might expect given the increased refresh rate, it still unmistakable and very eye-catching.

At 144Hz the object is sharper and more detailed once again, with some of the details on the UFO becoming a bit more distinctive. This reflects another nice step up in motion clarity due to a significant decrease in perceived blur. With the ‘Standard’ setting the trailing is now just a faint whiff behind the UFO – behind the red body in particular, it’s barely there now and appears less bold. It is certainly a lot less noticeable to the eye when compared to 60Hz and a bit of a step up when compared to 100Hz as well. With the ‘Advanced’ setting the overshoot now appears a bit bolder, particularly behind the yellow cockpit. The ‘Ultra Fast’ setting shares the usual issues – extreme and very eye-catching overshoot.

If you observe the monitor under a broader range of pixel transitions, as we do in the subsequent section, there are some transitions which show different behaviour. The most critical difference is that there is more noticeable overshoot than demonstrated here using the ‘Advanced’ setting, for some transitions. This is particularly true at 144Hz and to some extent 100Hz, but less so at 60Hz. We found the ‘Standard’ setting to be our favourite at higher refresh rates. As we explore below the hints of extra trailing here were quite faint, depending on the transition. We found this generally less eye-catching than the overshoot using faster response time settings. And indeed far less noticeable that the overshoot that graces most 144Hz monitors once their pixel overdrive solution is active (BenQ’s AMA, for example). The ‘Standard’ setting still employs effective grey to grey acceleration, but is not more aggressive than it needs to be. The ‘Advanced’ setting provides only relatively minor overshoot at 60Hz, whereas the conventional trailing in ‘Standard’ is more noticeable here. So users who are forced to use 60Hz (games console users, perhaps) might consider using this mode for that, but for higher refresh rates the ‘Standard’ setting is preferable in our view.

Responsiveness in games and movies

On Battlefield 4 the gameplay was extremely fluid where the frame rate kept up with the 144Hz refresh rate. There was an excellent ‘connected feel’ that is exactly what many gamers, competitive or otherwise, will appreciate. A seemingly instantaneous reaction and flow between user interaction translating to movement or actions carried out on the game itself. This came from the combination of negligible signal delay and the fact that the screen is pumping out up to 2.4 times as much information every second compared to a 60Hz model. The pixel responses were also clearly very snappy, with some faint trailing during some transitions such as those involving darker objects. There was no observable overshoot to get in the way of the experience. You were therefore left with a relatively low level of perceived blur that made zipping around in vehicles or running about on foot much less dizzying than at 60Hz. The level of detail maintained even during rapid movements was simply much better, making it easier to track an engage enemies and aiding that ‘connected feel’ which gamers crave.

We also fired up Dirt Rally. With this title, we didn’t find the exceptionally low latency to be as beneficial or potentially game-changing as on BF4. Although hardcore racing fans might argue that seemingly instantaneous response to controller input is fantastically helpful on such titles. We certainly appreciated the relatively low levels of perceived blur at high frame rates, though, and the overall visual fluidity that presented itself when racing around the beautiful courses on this game. Being able to appreciate little details in the environment and being able to remain quite focused on the tracks during rapid manoeuvres is certainly something to be appreciated. There was again no observable overshoot nor any disturbing trailing from slower than optimal pixel responses, which was pleasing.

Those familiar with our reviews will know what we’re going to say here as we round off our testing with the Blu-ray movie titles. The monitor certainly doesn’t have a chance to shine here as it did when gaming. The low input lag does it no favours as you don’t interact with such movies and they’re limited to around 24fps anyway. Even so, motion was handled here by the XG2401 as well as we’ve seen. The experience was not impeded by sluggish pixel responses or noticeable overshoot. Compared to running a monitor at 60Hz and watching such films, there was also less judder due to the ~24fps dividing nicely into 144Hz (6*24fps = 144Hz vs. 2.5*24fps = 60Hz).

Interlace pattern artifacts

Often when we review models using this panel and indeed high refresh rate models more generally (and sometimes 60-72Hz models for that matter) there are certain visual disturbances that can be observed during motion. We tend to refer to these as ‘interlace pattern artifacts’, which is quite descriptive. They’re generally quite faint and manifest themselves in different ways on different monitors. On the XG2401 these were present as a sort of faint woven appearance to some lighter textures during motion at certain speeds. This is shown in the image below. We didn’t find this distracting or eye-catching and some users wouldn’t even notice it at all, but sensitivity to this varies. This occurs regardless of response time setting, refresh rate, input lag settings or FreeSync status.

FreeSync – the technology and activating it

AMD FreeSync is a variable refresh rate technology that aims to eliminate the tearing and stuttering associated with frame rate and refresh rate mismatches. The technology is supported by certain AMD GPUs (including these and future models). It is similar in its operating principles to Nvidia G-SYNC, which uses a proprietary ‘G-SYNC board’ to allow the GPU to communicate to the monitor so that the refresh rate can be adjusted according to the frame rate of the content. Rather than using a special board inside the monitor, AMD FreeSync requires support of VESA Adaptive-Sync which is an optional extension of certain HDMI and DP standards. Specifically, Adaptive-Sync is a capability integrated into the DP 1.2a or HDMI 1.4a port controllers of certain monitors, including the DisplayPort input of the ViewSonic XG2401. To understand the benefits of the technology and why it’s important to match the refresh rate of the monitor with the frame rate of the content, we advise reading either the relevant section of our monitor responsiveness article. Alternatively, a good summary is provided in our G-SYNC article.
As noted above the XG2401 supports Adaptive-Sync and therefore AMD FreeSync via DP 1.2a. Our test system uses a Club3D Radeon R9 290 royalAce, a GPU that is compatible with FreeSync. AMD’s recent drivers include Radeon Software Crimson, which makes activation of the technology very straightforward. It should be automatically enabled by default, but you can check this by opening ‘AMD Radeon Settings’ and clicking ‘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 purely provided for reference.

As noted above the XG2401 supports Adaptive-Sync and therefore AMD FreeSync via DP 1.2a. Our test system uses a Club3D Radeon R9 290 royalAce, a GPU that is compatible with FreeSync. AMD’s recent drivers include Radeon Software Crimson, which makes activation of the technology very straightforward. It should be automatically enabled by default, but you can check this by opening ‘AMD Radeon Settings’ and clicking ‘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 purely provided for reference.

There are is a setting on the monitor itself that must be enabled for FreeSync to work. You need to go to ‘Advanced Image Adjust’ and ensure the ‘AMD FreeSync’ checkbox is checked. If you go to ‘Setup Menu’ you’ll notice that there is a ‘DisplayPort 1.2’ checkbox that is not checked by default. If you enable FreeSync then this setting is bypassed – FreeSync requires the use of DP 1.2a and works regardless of whether the DP 1.2 option is checked or not.

The XG2401 supports a variable refresh rate range of 48 – 144Hz. Because the upper value is at least 2.5 times the lower value, LFC (Low Framerate Compensation) is also supported. This allows the monitor to use multiples of the frame rate for its refresh rate once the frame rate dips below 48fps (for example 20 fps = 60Hz). This helps keep tearing and stuttering in check even below the hardware floor of operation (48fps/48Hz). At frame rates beyond 144fps, the GPU respects your selection of ‘VSync on’ or ‘VSync off’ in the graphics driver. With ‘VSync on’ the frame rate will not be allowed go above 144fps, with VSync activating automatically at this point and imposing the usual latency penalty when it does so. With ‘VSync off’ the frame rate is unlocked and will rise above 144fps. Because this is above the 144Hz refresh rate ceiling of the monitor, FreeSync is deactivated and you get tearing and juddering which some users may find troublesome. Others will prefer this option for minimal latency.

VSync is configured in the ‘Gaming’ section of ‘Radeon Settings’, where it is referred to as ‘Wait for Vertical Refresh’. You can set this for each game individually, or alternatively set it as a global attribute under ‘Global Settings’. The default setting is is ‘Off, unless application specifies’ which means that VSync is only active if you enable it within the game itself. Most games have such an option, but it could be referred to as something along the lines of ‘sync every frame’ rather than simply ‘VSync’. Most users will probably want to enable VSync when using FreeSync to ensure that they don’t get any tearing. One of the final two options in the list, shown in the image below, would therefore be preferable.

There are a few final points to note. Firstly, for FreeSync to work, the application must be running full screen rather than in a window (borderless or otherwise). Secondly, this monitor offers no obvious indication that FreeSync is actually active. The power LED does not change colour and there are no on-screen notifications. However; if you go to the ‘Information’ section of the OSD, you will see the ‘V. Frequency’ rapidly changing in response to fluctuating frame rates if FreeSync is enabled. If it is disabled, this will remain static regardless of frame rate fluctuation.

FreeSync – the experience

The first title we tested with FreeSync was Star Wars Battlefront. Using the settings we like to use, with our Radeon 290, the frame rate on this title fluctuated quite considerably. It generally stayed above 100fps, but spent little time meeting the maximum supported by the monitor (i.e. 144fps). With FreeSync disabled, these fluctuations were quite disturbing to our eyes. Without VSync disabled, we found the tearing and associated juddering to be quite obvious – just like the stuttering with VSync enabled. With FreeSync, though, the flow of the game was not interrupted with such things. Although there was an increase in perceived blur and a somewhat weakened ‘connected feel’ at closer to 100fps than 144fps (which FreeSync can’t fix), the overall visual fluidity and responsive feel was still excellent. Sensitivity to stuttering, tearing and associated effects does vary and it is something that’s more obvious at lower frame rates (and refresh rates). But for sensitive users the difference that variable refresh rate technologies such as FreeSync make, even at these high frame rates, is quite a game-changer.

The second title we tested was Tom Clancy’s The Division. This is fairly taxing, graphically, especially with the eye candy turned up a bit. Using the settings we liked to use, the frame rate fluctuated wildly. Typically it was between 70 – 130fps. At the lower end of this the experience was noticeably less fluid – the connected feel that you get at higher frame rates simply wasn’t there and perceived blur was increased significantly. This part didn’t change whether or not FreeSync was active; relatively low frame rates remain relatively low frame rates. With this technology enabled, though, the lack of stuttering and tearing made the gaming experience that bit more pleasant and ‘flowing’. We did notice that the pixel responses provided more noticeable trailing as the frame rate dropped into double digits. This was especially noticeable closer to 60fps. This extra trailing reflected what we observed on TestUFO. The monitor seems nicely optimised for higher refresh rates but less so for lower refresh rates. This is certainly a distinction we have seen in the past when comparing G-SYNC and FreeSync-compatible displays. G-SYNC displays adapt their pixel overdrive appropriately for lower frame rates and refresh rates, whereas FreeSync-compatible displays use a ‘one size fits all’ that’s usually designed with the upper end in mind. There was no noticeable overshoot regardless of frame rate, though, which is good and contrasts with what we’ve seen on the AOC G2460PF for example.

We also ramped up the detail on The Division to see what happened when the frame rate dropped below the 48fps hardware floor of operation (48Hz). LFC kicked in seamlessly and we noticed no stuttering or tearing as we’d see with the technology disabled. There was no abrupt change that we could perceive in either motion handling or responsive feeling above and below the LFC threshold, either. So this technology certainly seemed to work as advertised and increased the effective range of FreeSync. Nevertheless, we would again like to stress that low frame rates remain low frame rates. The overall fluidity and perceived blur is much better on this monitor at higher frame rates, ideally into triple digits.

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

The ViewSonic XG2401 uses a panel we’ve seen on dozens of monitors already. So we had a fair idea of what to expect. But there is more to a monitor than just a panel, with a lot also coming down to how everything is tuned by the monitor manufacturer. In that respect ViewSonic did an impressive job. Out of the box the image could certainly do with a bit of adjustment, particularly with respect to brightness, but gamma handling was actually pleasing. This gave the image quite a rich look overall, which was far beyond what most 24” 144Hz models produce without deeper and potentially problematic corrections (i.e. ICC profiles). The usual TN weaknesses related to viewing angle and gamma handling applied, with weakening saturation lower down the screen and stronger saturation higher up. Having everything balanced around a ~2.2-2.3 gamma helped the end result tremendously, however.

There were no surprises when it came to contrast. Static contrast was exactly as we’d expect, very close to the 1000:1 specified. The gamma handling meant that perceived detail levels in dark scenes changed depending on where on the screen you’re observing, but the absence of any ‘IPS glow’ or anything of that nature was certainly attractive. The screen surface also influenced the performance in this area, giving a bit of a grainy look to whites and other light shades. This was not heavy and smeary, but still more noticeable than on some smoother matte surfaces.

Where this monitor really shone was its responsiveness. This is an area where you can expect strong performance, but usually the rapid pixel responses come at the expense of potentially obvious overshoot (inverse ghosting). Instead, the XG2401 provided a very ‘clean’ performance with no observable overshoot and relatively faint conventional trailing. This was certainly the case at higher refresh rates, at least. The monitor supports AMD FreeSync and that worked exactly as you would hope – getting rid of the tearing, juddering and stuttering associated with the usual refresh rate and frame rate mismatches. There were some weaknesses in pixel responsiveness apparent at lower refresh rates, particularly closer to or below 60Hz. The screen remained free of overshoot, though, and the lack of stuttering or tearing here (with FreeSync enabled) was pleasant. It was also nice to see next to no input lag, with exceptionally low signal delay – the responsive feeling this gave, coupled with high refresh rates and frame rates, was excellent.

The design of the monitor won’t appeal to everyone, but is fairly ‘safe’ in our view. Nothing immensely bold – a bit of red here and there but a fairly subtle look compared to some of the more ostentatious gaming monitor designs we’ve seen. The full ergonomic flexibility and solid build quality was pleasing, too, but less so was the confusing button placement. ViewSonic really need to show some consistency between the physical order of their ‘1’ and ‘2’ buttons and what is shown on-screen in the menu system. This is surely a minor quibble, though, and we feel the important aspects of the monitor (performance, in particular) have been well thought-out. This is quite possibly the best use of the now ubiquitous 144Hz AUO panel that we’ve seen. FreeSync is certainly a nice bonus, if you have a compatible GPU, but even being a little more expensive than competing models we feel Nvidia users should seriously consider it too.

The bottom line; an exceptionally responsive gaming monitor with respectable image quality – putting the panel it uses to very good use.

 

Donations are also greatly appreciated.