Dell Alienware AW2521HF

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 didn’t readily observe either artifact type at high or relatively high refresh rates (100Hz+). We observed some faint vertical dynamic interlace patterns at ~60Hz and below, but these were not particularly obtrusive in our view. Sensitivity to such things varies, however. The ‘Response Time’ setting or Adaptive-Sync status didn’t affect these observations.

Responsiveness

Input lag

A sensitive camera and a utility called SMTT 2.0 was used assess the latency of the Dell Alienware AW2521HF. Over 30 repeat readings were taken to help maximise accuracy. Using this method, we calculated 2.63ms (under 2/3rds of a frame at 240Hz) of input lag. At 60Hz we measured a slightly higher but still reasonable 6.47ms. This figure is influenced both by the element of input lag you ‘see’ (pixel responsiveness) and the element you ‘feel’ (signal delay). It indicates a very low signal delay at 240Hz which even sensitive users shouldn’t find bothersome. Note that we have no way to accurately measure input lag with Adaptive-Sync active in a variable refresh rate and frame rate environment.

Perceived blur (pursuit photography)

Our article on responsiveness analyses the key factors affecting monitor responsiveness. One of the most important concepts raised in that article is ‘perceived blur’, contributed to by the movement of your eyes as you track motion on the screen as well as pixel responsiveness. Whilst both elements are important, eye movement is usually the dominant factor on modern monitors. The article also covers a technique called ‘pursuit photography’, using a moving rather than stationary camera to capture motion in a way that reflects both elements of perceived blur. Rather than simply reflecting the pixel response elements.

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, highlighting 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. All three rows of the test are analysed (dark, medium and light background) to show a range of pixel transitions. The monitor was tested at 60Hz (directly below), 144Hz and 240Hz using all available ‘Response Time’ settings; ‘Fast’, ‘Super Fast’ and ‘Extreme’. Pixel response behaviour was similar under the ‘Fast’ setting whether Adaptive-Sync was active or not both in this test and more broadly. There were some significant differences when Adaptive-Sync was disabled using the ‘Super Fast’ and ‘Extreme’ settings – these are documented as ‘VRR off’ (Variable Refresh Rate off). The monitor can also be set to 120Hz – although not documented in this testing, results were very much comparable to 144Hz. The final column includes a reference screen, the Acer XN253Q X which is a very fast 240Hz TN model with well-tuned pixel overdrive.

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 without sharp focus or clear internal detailing. This reflects a moderate amount of perceived blur due to eye movement and is something shared with the reference screen. There is various degrees of trailing behind the UFOs due to pixel response time weaknesses. In this case, overshoot (inverse ghosting) including some colourful bright ‘halo’ trailing due to aggressive pixel overdrive. The ‘Fast’ setting only showed a relatively small amount of this, whilst the ‘Super Fast’ and ‘Extreme’ settings ramped this up. ‘Extreme’ in particular showed very strong and eye-catching overshoot. ‘VRR off’ did not significantly affect the pixel response behaviour at this refresh rate. The ‘Fast’ setting was quite close to the reference here, with slightly stronger but still by no means extreme overshoot. We therefore consider ‘Fast’ the optimal setting at 60Hz. The image below shows how things look with refresh rate bumped up to 144Hz.

At 144Hz, above, the UFO appears narrower and more sharply focused, with better internal detailing. This reflects a significant reduction in perceived blur due to eye movement. There are again varying levels of trailing behind the UFOs due to weaknesses in pixel responsiveness, but this takes a different form to at 60Hz. With the ‘Fast’ setting, there’s just a faint hint of ‘powdery’ trailing, sticking very close to the UFO and very light in appearance. The ‘Super Fast’ setting just slightly reduces this, replacing it with a very small amount of overshoot. A very slight ‘shadowy’ trail behind the UFO, but overall rather similar to the ‘Fast’ setting in appearance. The ‘Extreme’ setting increases the overshoot so it’s more noticeable, particularly for the medium background (middle row).

Disabling VRR now has a more pronounced effect on pixel response behaviour, with both the ‘Super Fast’ and ‘Extreme’ settings introducing very obvious bright and colourful overshoot. We consider either ‘Fast’ or ‘Super Fast’ optimal here, both being very well-tuned and difficult to distinguish from one another in practice. They also come surprisingly close to the reference screen, with just a hint of ‘powdery trailing’ for the dark background (top row) that isn’t there on the reference. But less of this behind the UFO cockpit for the medium background. We again consider ‘Fast’ or ‘Super Fast’ to be optimal – ‘Fast’ becomes the clear winner with ‘VRR off’, though. Below you can see how things appear with refresh rate ramped up to 240Hz.

At 240Hz, above, the UFOs again appear more sharply focused again with clearer internal detailing. The segments are now quite distinct. This reflects another significant reduction in perceived blur due to eye movement. There are again varying degrees of trailing behind the object due to pixel response weaknesses. The ‘Fast’, ‘Super Fast’ and ‘Extreme’ settings are all rather similar here. There is a little ‘light powdery’ trailing behind the UFOs, particularly for the dark and medium backgrounds. The pixel response requirements for optimal performance have increased significantly due to the significant bump up in refresh rate. Things aren’t quite up to the level of the TN reference, but there are no particularly pronounced weaknesses either. This reference screen shows no noticeable ‘powdery’ trailing but a little overshoot instead.

With ‘VRR off’ the ‘Super Fast’ and moreover ‘Extreme’ settings show strong overshoot in the form of bright ‘halo’ trailing. And additional overdrive artifacts with parts of the UFO appearing displaced or ‘over-aliased’. Considering a broader range of pixel transitions, all ‘Response Time’ settings were fairly similar at 240Hz with Adaptive-Sync in use (VRR on). A slight reduction in powdery trailing at the expense of a bit of overshoot being introduced was the trade-off when stepping up the level, but the differences were not too profound. The optimal setting here depends on your own preferences in this respect. The stronger overdrive settings are certainly worth exploring if you can consistently maintain a very high frame rate but still use Adaptive-Sync. The ‘Fast’ setting shows a clear lack of overshoot at 240Hz and relatively low overshoot at much lower refresh rates, though, whilst still providing rapid pixel responses overall. For users who wish to disable Adaptive-Sync they can just stick with ‘Fast’ without worrying about strong overshoot, too. We stuck with the ‘Fast’ setting for the subjective testing below.

Responsiveness in games and movies

On Battlefield V the monitor provided a very fluid experience, where the frame rate kept pace with the 240Hz refresh rate. Compared to at 60Hz, or indeed a 60Hz monitor, you’re getting up to 4 times as much visual information pumped out every second. And twice as much when compared to 120Hz or 1.67 times as much compared to 144Hz. This gives an excellent ‘connected feel’, which describes the precision and fluidity felt when interacting with your character and the game world. The very low signal delay of this model also aided the ‘connected feel’, but the very high frame and refresh rate combination also helped. The perceived blur due to eye movement was also greatly reduced, much as demonstrated with the pursuit photos earlier on. The improvement in ‘connected feel’ and reduction in perceived blur was still noticeable to us and would be to sensitive users going up from 144Hz to 240Hz. Although not nearly as pronounced or obvious as stepping up from 60Hz to 144Hz (or even 120Hz).

For the lowest levels of perceived blur it’s also important that the monitor performs its pixel responses rapidly. And this monitor put in a very respectable performance in that respect. Most pixel transitions were performed fast enough for a solid 240Hz experience, with either no additional trailing or just a little ‘light powdery’ trailing in places. The perceived blur was therefore dominated by eye movement and the monitor put its 240Hz refresh rate to good use. There were some slightly more pronounced weaknesses for a minority of pixel transitions, for example when observing white or very light objects such as in-game text against a dark and shadowy background. This resulted in a more noticeable ‘powdery’ trailing with a greater effect on perceived blur. Not ‘smeary’ in appearance, but it extended out a bit more and had a greater effect on perceived blur compared to the ‘light powdery trailing’ described earlier. In the example of white text against a shaded backdrop, this only occurred at certain grey levels for the background, so not all dark shades would trigger it. This could be reduced by turning up the ‘Response Time’ setting, but as explored earlier with Test UFO you’d need Adaptive-Sync enabled and suitably high frame rates to avoid strong overshoot if doing that.

This more pronounced ‘powdery’ trailing was still less pronounced than some of the weaknesses we’ve observed observe for similar transitions on many 240Hz TN models, including the predecessor to this model (AW2518H/HF), ViewSonic XG2530 and AOC AG251FG. The new generation TN panels such as the Acer XN253Q X don’t show any noticeable weaknesses in terms of ‘powdery’ trailing and offer impressively rapid pixel responses across the board. However; that also comes with a bit of overshoot, whereas the AW2521HF is entirely free from any noticeable overshoot at 240Hz and very high refresh rates. Overall it put in a respectable performance for the panel type and will keep a broad spectrum of gamers happy, from casual to competitive.

Given the extensive analysis above, we don’t much to add from Shadow of the Tomb Raider. The competitive advantage of the 240Hz refresh rate was irrelevant on this title, although we still noticed an edge in ‘connected feel’ and perceived blur on the rare occasions frame rate got up high enough. The monitor delivered a very competent 240Hz performance, with only minor weaknesses as described earlier. Even on this title where there are lots of ‘high contrast’ transitions, with bright objects against much darker backgrounds, there was nothing that really caught the eye as a clear weakness. Some isolated weaknesses such as bright markers or strongly illuminated objects against some shaded backgrounds leaving a ‘powdery’ trail – but as with our observations in BFV this wasn’t really a major weakness. We also tested movie content, which was much more limited in frame rate (generally 24fps, 30fps or 60fps). The pixel response requirements are slacker at such frame rates and the visual fluidity is greatly limited by the frame rate itself. Perhaps unsurprisingly, the monitor provided an excellent performance in all cases, with no noticeable weaknesses. The 240Hz refresh rate also allows even division of 24fps, 30fps and 60fps which reduces juddering for such content – the lack of overshoot at 240Hz worked nicely as well.

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FreeSync – the technology and activating it

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

FreeSync requires a compatible AMD GPU such as the Radeon RX 580 used in our test system. There is a list of GPUs which support the technology here, with the expectation that future AMD GPUs will support the feature too. 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 AW2521HF supports FreeSync Premium via DP 1.2a and HDMI 2.0 on compatible GPUs and systems. You need to make sure ‘FreeSync’ is set to ‘On’ in the ‘Game’ section of the OSD. On the GPU driver side recent AMD drivers make activation of the technology very simple and something that usually occurs automatically. You should ensure the GPU driver is setup correctly to use FreeSync, so open ‘AMD Radeon Software’, click ‘Settings’ (cog icon towards top right) and click on ‘Display’. You should then ensure that the first slider, ‘Radeon FreeSync’ is set to ‘Enabled’ as shown below. The screenshot below is for a different model, but the settings and layout of the page are the same.



The Dell Alienware supports a variable refresh rate range of 48 – 240Hz. That means that if the game is running between 48fps and 240fps, the monitor will adjust its refresh rate to match. When the frame rate rises above 240fps, the monitor will stay at 240Hz 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 240fps, 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 >240fps). 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 34fps, for example, the refresh rate would be 68Hz 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 Radeon Software’. Click ‘Settings’ (cog icon towards top right) and click ‘Graphics’. The setting is listed as ‘Wait for Vertical Refresh’. This configures it globally, but if you wish to configure it for individual games click ‘Game Graphics’ towards the top right. The default is ‘Off, unless application specifies’ which means that VSync will only be active if you enable it within the game itself, if there is such an option. Such an option does usually exist – it may be called ‘sync every frame’ or something along those lines rather than simply ‘VSync’. Most users will probably wish to enable VSync when using FreeSync to ensure that they don’t get any tearing. You’d therefore select either the third or fourth option in the list, shown in the image below. Above this dropdown list there’s a toggle for ‘Radeon Enhanced Sync’. This is an alternative to VSync which allows the frame rate to rise above the refresh rate (no VSync latency penalty) whilst potentially keeping the experience free from tearing or juddering. This requires that the frame rate comfortably exceeds the refresh rate, not just peaks slightly above it. We won’t be going into this in detail as it’s a GPU feature rather than a monitor feature.



Some users prefer to leave VSync enabled but use a frame rate limiter set a few frames below the maximum supported (e.g. 237fps) instead, avoiding any VSync latency penalty at frame rates near the ceiling of operation or tearing from frame rates rising above the refresh rate. If you activate the ‘Frame Rate’ feature under ‘Game’ – ‘Game Enhance Mode’ in the OSD, this will display the refresh rate of the display and therefore indicate the frame rate if ‘FreeSync’ is active and the frame rate is within the variable refresh rate range of the display. The final point to note is that FreeSync only removes stuttering or juddering related to mismatches between frame rate and refresh rate. It can’t compensate for other interruptions to smooth game play, for example network latency or insufficient system memory. Some game engines will also show stuttering (or ‘hitching’) for various other reasons which won’t be eliminated by the technology.

FreeSync – the experience

As usual we tested a broad range of game titles using FreeSync and found the experience similar across the board. Any issues identified with FreeSync that were isolated to a specific title would indicate an issue with the game or GPU driver rather than the monitor as well. We’ll therefore just focus Battlefield V for this section. This title offered suitable graphics options to test the full gamut of refresh rates supported by the monitor. Our RX 580 is far from a powerhouse of a graphics card, so maintaining 240fps was very tricky. It requires huge visual sacrifices and very specific content to be shown on the screen. Dips below this were common. Even if such dips were very slight, without FreeSync active and VSync enabled they’d cause obvious stuttering. Without FreeSync active and VSync disabled, you’d get obvious tearing from the lack of synchronisation between frame and refresh rate. When we say obvious, it’s very subjective – sensitive users can certainly notice such things and it can be very nice indeed having them gone. But some users don’t find such issues as noticeable and won’t benefit as much from FreeSync.

As frame rate dropped further, well below 200fps, the ‘connected feel’ and perceived blur was noticeably impacted. But far from poor. And the lack of tearing and stuttering was very nice indeed, if you’re sensitive to such things. With respectable graphics settings and more intense action it wasn’t uncommon to see dips below 100fps, perhaps closer to 60fps on average. The ‘connected feel’ and perceived blur took a real hit here, but the technology did its thing to get rid of tearing and stuttering all the same. As the frame rate dropped we noticed an increase in overshoot. It started to creep in a little bit even at the high double digit to very low triple digit frame rates. With some more noticeable ‘halo’ trailing by about 80fps (80Hz). This was by no means extreme and not everyone will notice it – many Adaptive-Sync models have much stronger overshoot than this following such refresh rate drops, in fact. Nonetheless it is still there as the overdrive is tuned for strong 240Hz performance rather than strong <100Hz performance. In contrast to models with G-SYNC modules, which feature variable overdrive that re-tunes things dynamically to a wide range of different refresh rates.

As things dipped even further, below the 48fps (48Hz) floor of operation for FreeSync, the monitor employed LFC (Low Framerate Compensation). This worked exactly as it’s designed to, removing tearing and stuttering by ensuring the refresh rate stuck to a multiple of the frame rate. The slight caveat to LFC is that there’s a very brief stutter when it activates or deactivates. This isn’t a strong stuttering and isn’t something you’ll generally notice or find bothersome unless you’re frequently passing the boundary.

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

As noted earlier, AMD FreeSync makes use of Adaptive-Sync technology on a compatible monitor. As of driver version 417.71, users with Nvidia GPUs (GTX 10 series and newer) and Windows 10 can also make use of this Variable Refresh Rate (VRR) technology. When a monitor is used in this way, it is something which Nvidia refers to as ‘G-SYNC Compatible’. Some models are specifically validated as G-SYNC compatible, which means they have been specifically tested by Nvidia and pass specific quality checks. With the AW2521HF, you need to connect the monitor up via DisplayPort and enable ‘FreeSync’ in the ‘Game’ section of the OSD. When you open up Nvidia Control Panel, you should then see ‘Set up G-SYNC’ listed in the ‘Display’ section. Ensure the ‘Enable G-SYNC, G-SYNC Compatible’ checkbox and ‘Enable settings for the selected display model’ is checked as shown below. Press OK, then turn the monitor off then on again so that it re-establishes connection – the technology should now be active.



In the image above you can see that the monitor is validated as ‘G-SYNC Compatible’ (or you could, if Nvidia Control Panel displayed the entire text instead of cutting it off). This indicates that the monitor has been specifically tested by Nvidia and passes specific quality checks. The monitor is also listed as such on Nvidia’s website. The technology worked well and offered a very similar experience to AMD FreeSync. A slight difference was that the floor of operation was 80Hz (80fps) on our Nvidia GPU. Nvidia’s website lists a 48 – 240Hz VRR, which would match AMD FreeSync. It’s possible newer Nvidia GPUs, including their RTX series, support this expanded range or it may have just been misreported on the website. Either way, where the frame rate drops below the floor of operation a frame to refresh multiplication technology (what AMD refers to as LFC) kicked in to keep tearing and stuttering at bay. As with AMD FreeSync this technology worked very well, although there was a momentary stutter when it activated or deactivated. Unless you’re frequently passing this boundary it’s not something you’re likely to notice or care about, though.

Our suggestions regarding use of VSync also apply, but you’re using Nvidia Control Panel rather than AMD Radeon Software to control this. The setting is found in ‘Manage 3D settings’ under ‘Vertical sync’, where the final option (‘Fast’) is equivalent to AMD’s ‘Enhanced Sync’ setting. You’ll also notice ‘G-SYNC Compatible’ listed under ‘Monitor Technology’ in this section, as shown below. Make sure this is selected (it should be if you’ve set everything up correctly in ‘Set up G-SYNC’).



Finally, note again that you can go to ‘Game Enhance Mode’ in the ‘Game’ section of the OSD to activate the ‘Frame Rate’ feature. This displays the current refresh rate of the monitor and will reflect the frame rate if it’s within the main variable refresh rate window (e.g. 80 – 240fps).

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
Responsiveness (General)
Responsiveness (Adaptive-Sync)

Conclusion

For those who play a variety of games, some competitive and some casual, having a screen that offers a 240Hz refresh rate and good colour quality can be very attractive. This is exactly what the Dell Alienware AW2521HF delivered. Whilst its 24.5” screen with Full HD resolution doesn’t deliver a staggering pixel density or the same useful ‘desktop real-estate’ as some models, it’s a relatively easy resolution to drive at high frame rates. The design of the monitor is in keeping with the ‘Alienware’ aesthetics of other recent additions to the series and indeed their other peripherals and systems. A futuristic ‘sci-fi prop’ look which some will find quite endearing. The ‘AlienFX’ lighting system allowed some degree of customisation and some elements are visible from the front, but it was our wall who got the most enjoyment out of the light show. We prefer stronger RGB LEDs at the rear, producing a strong glow around the monitor that can help enhance perceived contrast. But being able to change the power LED colour to suit your mood is a nice little touch. The monitor didn’t put form over function, either, and was solidly built with good ergonomic flexibility and VESA mounting options.

The contrast performance was much as we were expecting. Around 1000:1 even following adjustments to our ‘Test Settings’. So better than some IPS-type models, weaker than others but very much as specified. ‘IPS glow’ also came with the territory. Together, the monitor certainly didn’t provide a deep and atmospheric look to dark scenes and is more suited to viewing in a well-lit room. The screen surface was a touch on the grainy side when viewing lighter content, although this wasn’t a strong ‘layered’ graininess or excessively sandy appearance thankfully. It’s something we’re sensitive to, as long-time readers of our website will be well aware. The IPS-type panel of the Dell Alienware certainly provided a key contrast advantage over VA and TN models, though. And that was its excellent gamma consistency. It was free from the sort of shifts in perceived gamma that can significantly mask dark detail in some regions of the screen whilst revealing too much detail elsewhere. Competing TN models certainly have something of a vertical detail gradient going on for dark content vertically, whilst VA models have ‘black crush’ centrally and a bit of extra detail peripherally.

The colour reproduction was a relative strength of this monitor and a good step up from competing models with other panel types. The colour gamut provided just a bit of extension beyond sRGB, injecting some extra vibrancy without the strong saturation of a much more generous colour gamut. We’d describe the image as ‘rich and natural’, with a richness maintained throughout the screen thanks to the strong colour-consistency. No saturation losses towards the bottom or edges as you’d see from other panel types. The responsiveness of the monitor was also quite impressive – which is a good thing given that it’s a key focus of 240Hz models like this. The refresh rate was put to very good use overall; fairly strong pixel responsiveness, low input lag and no noticeable overshoot. There were slight weaknesses for some transitions, though these were fairly minor and aren’t something everyone would find bothersome. Adaptive-Sync also worked well on both our AMD and Nvidia GPU to get rid of tearing and stuttering. Using VRR improved pixel response behaviour for very high refresh rates, too, allowing the ‘Extreme’ overdrive setting to be used without strong overshoot. There’s no strobe backlight mode on this model, but they come with their own compromises that not everyone is willing to make. Given the pleasing responsiveness and colour performance, nice overall build and (subjectively speaking) styling we feel this is an excellent 240Hz Full HD model overall. In our view the price is also very reasonable and highly competitive given what’s on offer.

The bottom line; strong responsiveness and colour performance from a stylish and well-priced monitor.

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