AOC G2590PX

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 G2590PX did not show obvious static interlace pattern artifacts, but we did observe quite strong dynamic interlace patterns. When movement was observed on the screen, the image sometimes appeared to break up into an interference pattern composed of vertical pinstripes. We found it quite noticeable, even from a viewing distance of well over 70cm. Although we noticed the effect and would much prefer it wasn’t there, we wouldn’t say it was too distracting when focusing on gameplay. At lower refresh rates this effect became more pronounced, being quite obtrusive at 60Hz to our eyes. It’s worth remembering that how obvious a user finds these patterns depends on the viewing distance, their eyesight and sensitivity to such things.

Responsiveness

Input lag

A sensitive camera and a small tool called SMTT 2.0 was used to assess the input lag of the G2590PX, comparing with a number of monitors of known latency. Over 30 repeat readings were taken to try to maximise accuracy. Using this method we calculated 3.48ms (~ ½ a frame at 144Hz) of input lag. This value takes 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, which even sensitive users shouldn’t have a problem with. Note that we have no way to accurately measure input lag when FreeSync is doing its thing. The measured values for input lag were similar with ‘Low Input Lag’ enabled and with FreeSync enabled on the GPU, which greys the setting out.

Perceived blur (pursuit photography)

Our responsiveness article explores the factors which affect responsiveness of a monitor. One of the most important factors explored is the notion 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. The second factor is generally the predominant contributor to perceived blur on modern monitors. The article also explores a photography method called ‘pursuit photography’, which motion on a monitor in a way that reflects both elements of perceived blur. A moving camera is used 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. All of the ‘Overdrive’ settings were tested under our ‘Test Settings’; ‘Off’, ‘Weak’, ‘Medium’ and ‘Strong’. We’ve also included some reference shots, including a Dell S2417DG (144Hz and 60Hz) and ViewSonic XG2401 (144Hz). The Dell performs its pixel responses very rapidly and indicates how things should look without pixel responses being a significant limiting factor. The ViewSonic is a useful reference as many users find its performance to be satisfactory, even though the pixel responsiveness is slightly weaker than optimal for the transitions shown.

Note: Rather strangely, the pixel overdrive worked more effectively with a ‘Game Mode’ active (as it was under our ‘Test Settings’). For that reason, we’ve included ‘Medium’ without any game mode active for comparison. The differences are not accounted for in differences in image setup and persisted even if the monitor was calibrated in the same way. The other response time settings also worked more effectively with a game mode active – ‘Strong’ provided a lot of overshoot regardless. Note that use of an Nvidia GPU or an AMD GPU with FreeSync enabled or disabled did not change this behaviour.

The images above were captured with the monitor set to 60Hz. The UFO appears broad and blurred without distinct details, indicating a moderate amount of perceived blur due to camera (eye) movement. Varying amounts of trailing can be seen behind the UFOs due to sub-optimal pixel responses. With ‘OD’ set to ‘Off’ the trailing is most significant, is quite bold and extends quite far behind the object. The ‘Weak’ setting cuts this down significantly, although a faint powdery trail remains. The ‘Medium’ setting removes all conventional trailing but replaces it with some overshoot (inverse ghosting) with the trailing appearing darker than the shades involved in the transition. Setting ‘OD’ to ‘Strong’ provides very strong overshoot, a with a veritable disco of bright and garish trailing appearing on the screen. With ‘OD’ set to ‘Medium’ and ‘Game Mode’ set to ‘Off’, the trailing appears more pronounced than with a game mode enabled at the same setting. There is actually some overshoot as well as conventional trailing that’s quite noticeable for the dark background. The medium background also shows this to a degree, although the light background is free from any obvious weaknesses. From this you could conclude that ‘Weak’ or ‘Medium’ (with a game mode active) is optimal at 60Hz, depending on preferences for a little bit of conventional trailing vs. some overshoot. The ideal result would really be some way between these.

With the refresh rate bumped up to 144Hz, as shown above, the perceived blur is significantly reduced. The UFO appears narrower and more detailed, indicating a significant reduction in perceived blur due to eye movement. There is also varying degrees of tailing behind this due to sub-optimal pixel responses. With ‘OD’ set to ‘Off’ the trailing is quite bold and appears like a sort of dark flare behind the object for the red UFO body. The ‘Weak’ setting cuts this down significantly, but some powdery trailing still remains. The ‘Medium’ setting yields further improvement, with a small amount of overshoot for the medium and light backgrounds in particular. The ‘Strong’ setting gives very obnoxious and painfully obvious overshoot, with distracting bright trailing behind the UFO. The ‘Medium’ setting with ‘Game Mode’ set to ‘Off’ has a fair bit of trailing. This is strongest for the dark background where it appears to actually extend the object due to its intensity – it’s short and sharp but very saturated. Overall, trailing there is more noticeable than the ‘Weak’ setting or arguably ‘Off’ with a game mode active. We deem ‘Medium’ (with a game mode active) to be the optimal setting at 144Hz and settled with that for our subjective testing. The cutting down of conventional trailing vs. ‘Weak’ with the introduction of only minor overshoot delivered the best experience in our view.

Responsiveness in games and movies

On Battlefield 1 (BF1) the monitor provided strong responsiveness, with a fluid experience at frame rates keeping up with the 144Hz refresh rate. The monitor displays up to 2.4 times as much visual data every second as a 60Hz monitor, which notably improves the gaming experience in two ways. Firstly, it improves the ‘connected feel’ – as you interact with the character and your game world, you feel a certain precision and responsiveness with the mouse in particular that is lacking at lower refresh rates. This is also aided by the low input lag of the AOC. Secondly, the high frame rate and refresh rate combination significantly reduces perceived blur as demonstrated earlier with the pursuit photographs. When running about, quickly turning the character or driving about in a vehicle, the game world remains more sharply focused and it’s easier to track and engage enemies. The ‘connected feel’ then helps your precision when you aim – overall, a winning combination.

As explained earlier, pixel responsiveness also influences perceived blur. On this model most pixel responses were very rapid and it certainly felt and looked like a highly responsive 144Hz TN model should, overall. There were some minor weaknesses, which our trained eyes could spot but that most users wouldn’t notice or find bothersome. Firstly, there were some slightly slower than optimal pixel transitions. There were no pixel transitions that were obnoxiously slow, but some that were slow enough to give just a little hint of trailing in places. This was always faint and short-lived, even where the monitor was performing its slowest transitions. Where dark objects such as gun emplacements were set against medium shades (a grey-blue sky, for example) you could see a little bit of trailing behind the object. There was also a little bit of overshoot in places, but this was again faint and, in our view, entirely undistracting. There were no bright ‘halo’ trails, obvious dark trails or anything we found eye-catching. Just some semi-transparent (‘snail slime’) or slightly darker than intended trailing in places. The overall performance remained very good even with these weaknesses in mind. By way of comparison, the ViewSonic XG2401 which many users find perfectly responsive and that we used as a reference earlier has more extensive trailing. And the infamous BenQ XL series models have significantly stronger overshoot using their optimal response time (AMA – Advanced Motion Acceleration) setting.

Dirt Rally provided a similar experience. The perceived blur was greatly reduced by the increased frame rate and refresh rate supported by the G2590PX. This gave the environments and objects within a sharper look whilst racing on the tracks and is provided an experience which some users would find more comfortable (especially if they suffer from motion sickness). The ‘connected feel’ also enhanced the interactions with the game world. This factor was less beneficial to us compared to on FPS titles like BF1, although more serious racing fans with proper gaming controllers (a steering wheel rather than keyboard, perhaps) would certainly appreciate this. There were again some weaknesses in terms of a small amount of trailing and a little overshoot here and there, but nothing that caught our eyes – even when were specifically aware of what we were looking for. Finally, we tested our Blu-ray test titles. The monitor exhibited no weaknesses in terms of pixel responsiveness and these titles looked very much as they should in terms of motion performance. Their pace and fluidity was limited by the low frame rate (~24fps) at which they run. The fact that this frame rate divides neatly into the refresh rate (144Hz) helped reduce juddering compared to running such titles at 60Hz, too.

FreeSync – the technology and activating it

AMD FreeSync is a variable refresh rate technology, an AMD-specific alternative 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 G2590PX 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, but 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 AOC supports a variable refresh rate range of 30 – 144Hz via DP (ceiling varies via HDMI, depending on GPU, and may be limited to 120Hz). That means that if the game is running between 30fps and 144fps, the monitor will adjust its refresh rate to match. When the frame rate rises above 144fps, the monitor will stay at 144Hz and the GPU will respect your 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 30Hz (30fps) floor of operation for FreeSync. If a game ran at 22fps, for example, the refresh rate would be 44Hz 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 rising slightly above it.



If the monitor is connected to a compatible GPU and the driver is configured correctly, you will see ‘FreeSync’ listed as the ‘V.Frequency’ in the ‘Extra’ section of the OSD. This will not indicate whether or not FreeSync is actively being used, simply that your system supports it. 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 a number of game titles on the monitor to test its FreeSync capabilities. Given that the experience was similar on all of them, we’ll instead focus on a single title for this section; Battlefield 1 (BF1). The flexible graphics options on this title also allowed the full range of refresh rates to be tested. Using settings that provided a good balance of performance and image quality, our Radeon 290 was able to put in a decent performance and output fairly high frame rates overall. Despite this, it was rare that the frame rate would consistently stay as high as 144fps. Without FreeSync active, even slight dips below this would cause tearing and juddering (VSync off) or stuttering (VSync on). Although these imperfections aren’t as jarring as at lower frame rates and refresh rates, they are certainly still noticeable to sensitive users. Increasing the graphics settings, for example using the ‘Ultra’ preset, would cause more significant drops in frame rate. Frequently into the double-digits, occasionally close to 100fps. There was an increase in perceived blur and decrease in ‘connected feel’, unavoidable with a decrease in frame rate, regardless of FreeSync being active. But things remained decent in that respect and the reduction in tearing and stuttering was a very nice bonus for sensitive users such as ourselves.

By further increasing graphics settings, for example increasing the ‘Resolution Scale’ setting, more dramatic losses in frame rate were observed. As things dropped further, at times well below 60fps even, it was certainly nice to have tearing and stuttering kept in check by FreeSync. Indeed, such imperfections are very noticeable to us at such low frame rates. We also found the lack of ‘connected feel’ and increase in perceived blur to be very unattractive at these relatively low frame rates. The experience was certainly very different to at much higher frame rates, a stark contrast to 144fps. Below 30fps, LFC kicked in as expected and kept tearing and stuttering at bay. Such low frame rates give a very uncomfortable gaming experience, though, and there is a perceived juddering due to the very low frame rate. Regardless of the lack of tearing and stuttering, things are far from fluid and not at all what this monitor is all about. A waste of potential, to put it mildly.

There were a few other observations worth making in relation to decreased frame rates and hence refresh rates with FreeSync active. Firstly, there was a slight increase in overshoot. We still found it to be minor and far less noticeable than on most FreeSync models, including AOC’s G2460PF. As noted earlier, there were some quite noticeable interlace pattern artifacts at a static 60Hz refresh rate. These occurred where FreeSync was active and the frame rate dropped to ~60fps or below. They didn’t suddenly kick in or anything like that, they just gradually became more noticeable as refresh rate dropped and were at their most pronounced by ~60fps.

Finally, we tested FreeSync whilst watching some video content. 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. Given our observations regarding interlace patterns becoming more noticeable at these lower refresh rates, you’d have to decide whether you find these too noticeable to offset any potential benefit from reduced juddering.

Conclusion

~24” 144Hz monitors nearly always use the same AUO TN panel and have done for several years now. The AOC G2590PX offered a refreshing change, using a newer 24.5” AUO TN panel with thinner bezels. Aesthetically speaking the monitor was quite pleasant and more modern-looking than many of its thicker-bezelled counterparts using the older panel. But we were more interested in the image performance. Out of the box the monitor offered a very bright but overall well-balanced image. Unlike the majority of competing models, it didn’t look ‘washed out’ by completely out of whack average gamma. And even compared to models without the average gamma problem, the image appeared slightly richer. The colour gamut was a touch wider, bringing a bit of extra saturation. And the colour consistency was a bit better, limiting the perceived gamma and saturation shifts. These were certainly still there, though, and to our eyes there was no mistaking this was a TN panel. Expecting any dramatic differences in that respect would be a setup for disappointment – but seeing slight improvement was still nice.

Static contrast was quite in-line with our expectations given the specifications of the panel. But that isn’t always something you can take for granted, as the ViewSonic XG2402 we reviewed just prior to this demonstrated. Whilst we don’t like to put too much weight on uniformity, as it can vary between individual units of the same model, we were quite happy with the dark uniformity of our unit. Clouding in particular was more subdued that we usually see from competing models. The screen surface was very similar to that used on the older panel. It would have been nice for a lighter/smoother matte surface to have been employed as seen on some higher resolution panels. But there was not an obtrusive layer of obvious graininess, even if light shades could have looked smoother.

For monitors like this, much of their appeal comes from their responsiveness. In that respect the monitor performed quite well, but not perfectly. There was very little input lag to speak of and, overall, pixel responses were very snappy. It had the sort of look and feel we’d expect from a highly responsive 144Hz TN model. There were some weaknesses in pixel responsiveness, but they were pretty minor. A little but of overshoot and trailing in places – but we stress the little, it’s not something we feel most users would notice. AMD FreeSync also worked well on this model, with a full range of 30 – 144Hz (plus LFC) supported. As usual low frame rates remained low frame rates regardless of the technology, but the lack of tearing and stuttering from frame rate and refresh rate mismatches was something we always welcomed. One element we were less welcoming of was the ‘interlace pattern artifacts’. We found these quite obvious at 144Hz and increasingly obvious at lower refresh rates, particularly around or below 60Hz. This is significant when using FreeSync, because reduced frame rates drag down the refresh rate as well and introduce these more noticeable interlace patterns. We should stress that individual sensitivity to these varies and they are common, in some form, on most high refresh rate monitors and some 60Hz monitors as well. Still, we would have much preferred that they weren’t there in the first place and found this manifestation of them quite obvious.

Another interesting (but potentially annoying) quirk with this monitor is that the pixel response behaviour is slightly better with a ‘Game Mode’ active. We were able to set the monitor up in a perfectly satisfactory way by using one of the custom game mode settings. But you have to remember that individual units vary and this level of tweaking can put some users off. Furthermore, the fact that you never have access to the colour channels with a ‘Game Mode’ active could prove problematic on some units or according to some user preferences. You need to rely on ‘LowBlue Mode’ settings if you wish to adjust the white point, but the steps there are quite dramatic and you have no control over the green channel. Overall, then, the monitor delivers an experience with a few bonuses compared to the sea of models using the older AUO panel. But there are a few niggles as well, which users will have to weigh up for themselves. If they are deemed only minor annoyances or not at all problematic, then this model is worth careful consideration.

The bottom line; a highly responsive monitor with respectable image quality, a step above models using ‘the older panel’ in some respects. But some minor niggles to go with it – because no monitor is perfect.