Dell S2417DG

Responsiveness

A note on overclocking

As covered in the OSD video earlier, there is an ‘Overclock’ feature in the ‘Display’ section of the OSD. This overclocks the refresh rate of the panel, which is natively 144Hz, to 165Hz. You can alternatively select an overclocked refresh rate of 150Hz, 155Hz or 160Hz. Even at 165Hz we did not observe any issues on our unit with continuous running at this refresh rate, which is why we settled on this for most of our testing. Most users should find it works without issue on their system, but be aware that the DisplayPort cable you’re using could potentially cause issues – specifically a long or poor quality cable could cause signal dropouts. Although DP is a digital signal and there is no such thing as ‘revisions’ of a cable (DP 1.1, DP 1.2 etc.) it has proven itself to be a somewhat sensitive signal at elevated bandwidths (i.e. 2560 x 1440 @ 165Hz). We used both the DP cable included in the box and a ‘Cable Matters’ 6ft cable which we had to hand and had no issues with this feature with either cable.

Input lag

We used a small tool called SMTT 2.0 alongside a sensitive camera and a range of displays of known latency, to calculate the input lag of the S2417DG. Over 30 repeat readings were taken to help maximise accuracy. Using this method, we calculated 3.51ms (a little over half a frame at 165Hz) of input lag. This value reflects both the element of input lag you ‘see’ (pixel responsiveness) and that which you ‘feel’ (signal delay). It indicates a very low signal delay, which shouldn’t be bothersome even to sensitive users. We don’t have the means to accurately measure latency with G-SYNC doing its thing, but to us it felt very much light a low latency high refresh rate monitor should with this technology active.

Perceived blur (pursuit photography)

In this article we explore key factors which affect a monitor’s responsiveness. A concept called ‘perceived blur’ is introduced, which is contributed to not only by the pixel responsiveness of the monitor but also the movement of your eyes as you track motion on a screen. For modern monitors this second factor is actually the most significant. A special photography technique called ‘pursuit photography’ is also introduced, which uses a moving camera to capture the perceived blur on a monitor in a way that reflects both pixel responsiveness and eye (camera) movement.

The images below are pursuit photographs taken using the UFO Motion Test for ghosting, with the middle row (medium cyan background) used. The test was run at its default speed of 960 pixels per second, which is a good practical speed for such photographs and highlights both elements of perceived blur nicely. The UFO moves across the screen from left to right at a frame rate matching the refresh rate of the monitor. The monitor was set to a range of refresh rates – 60Hz, 100Hz, 144Hz and 165Hz. It was also set to 85Hz, 100Hz and 120Hz with its ULMB feature active and the ‘Pulse Width’ set to its default value of ‘100’. The ‘Fast’ response time setting is only shown at 144Hz as the nature of the trailing (or more specifically, overshoot) is the same regardless of refresh rate. The final column shows a ‘Reference Screen’ running at 60Hz and 144Hz plus all of the refresh rates tested with ULMB. This reference screen is a Dell S2716DG set to its optimal ‘Normal’ response time setting (where applicable), which provides a useful comparison as a highly responsive 144Hz monitor that this model will naturally be compared with. Note that any interlacing in these photographs is moiré from the camera and not observed on the monitor itself.

At 60Hz the UFO appears noticeably blurry, with a lack of fine detail. This is caused almost entirely by eye movement – there is very little trailing or overshoot (inverse ghosting) visible behind the UFO. It is largely comparable to the 60Hz reference (S2716DG) with a slightly ‘cleaner’ performance if anything due to a lack of dark trailing (overshoot) behind it. This is faint on the reference display, which is good, but absent on the S2417DG, which is better. At 100Hz the UFO becomes more sharply focused, indicating a significant decrease in perceived blur due to eye movement. There is no obvious trailing behind the object, either – just a very faint whiff of overshoot. At 144Hz the object becomes even more sharply focused, with some of the diner detail such as the segments of the UFO becoming more distinctive. There is a little bit of overshoot, but this is very faint – more so compared to the reference shot. This contrasts with the obvious inky trail of inverse ghosting (strong overshoot) behind the object using the ‘Fast’ setting. At 165Hz the fine details become even more distinctive and the object a little more sharply focused again. This signifies another improvement in perceived blur – and there is no obvious trailing or overshoot to speak of, either.

With ULMB active you can see that the UFO is significantly sharper with the segments of the UFO body and the Alien’s face appearing more distinctive. The level of detail improves further at 100Hz and again at 120Hz – note the clarity of the white dots on the UFO body at 120Hz in particular. The perceived blur due to eye movement is extremely low, which accounts for the clarity of the object itself. ULMB does call for a strong overdrive impulse to be used, though, to prevent frame overlap. You can see the effect of that in the form of inverse ghosting behind the object. This is not as strong as using the ‘Fast’ response time setting with ULMB disabled – note again that the ‘Response Time’ setting can’t be adjusted with ULMB active. Performance here is extremely similar to the reference S2716DG, which is perhaps unsurprising given the overall similarities between the displays. Note that these images do not show the flickering which can be observed with ULMB active – this is mentioned earlier in the review and will be touched upon in the dedicated ULMB section as well.

It is quite clear from this analysis and indeed analysing the monitor more broadly that the ‘Normal’ setting is optimal. Even at 165Hz, the monitor is able to provide a very ‘clean’ performance that is finely optimised – free from obvious trailing or overshoot. This will become even clearer during the subjective analysis that follows. That is an improvement over the 27” model, which had some more noticeable overshoot in places. It was not particularly obnoxious in our view, as we noted in the review, but the performance here is superior in that respect. Another advantage of the 23.8” model is that we did not observe interlace pattern artifacts (some people may call these ‘inversion artifacts’) either during motion or when observing static content.

Responsiveness in games and movies

Where the frame rate kept pace with the 165Hz refresh rate (i.e. 165Hz) on BF1, the overall fluidity was excellent. The ‘connected feel’ as you interact with the game world was excellent, far superior to even the lowest latency 60Hz displays. The fact that the monitor was outputting 2.75 times as much visual information every second not only improved the ‘connected feeling’, but also greatly reduced perceived blur. This was obvious whether moving the mouse around and changing the character’s viewpoint, sprinting about or moving in a vehicle as the game world appeared more sharply focused. It was easier to track and engage ‘the bad guys’ as a result and for those sensitive to motion blur the experience was altogether less dizzying. With 165Hz/165fps, there was a slight advantage over even highly responsive 144Hz models (running at 144fps) such as the Dell S2716DG. This was true both in terms of the connected feel and level of perceived blur. The difference was only slight and much more subtle than moving from 60Hz up to 100Hz or from 100Hz up to 144Hz. And indeed sensitivity to this varies, so not everybody will appreciate this quite as much as others anyway. One thing we feel may be more broadly appreciated is the complete lack of obvious overshoot, even during the transitions that troubled this model’s 27” counterpart. There was nothing more than the faintest hint during a small number of transitions, nothing eye-catching at all. Despite this, there was no noticeable conventional trailing either.

We also enjoyed the high frame rate 165Hz experience on Dirt Rally. It was easier to admire the scenery whilst tearing through it in a fast car with the reduced level of perceived blur afforded by the 165Hz refresh rate. This was again a subtle difference coming from 144Hz, but more appreciable compared to LCDs with lower refresh rates. We also felt very much ‘at one’ with our car due to the superior ‘connected feel’; nice though this was, it would be more of an advantage to users who are actually experienced and competent in racing games. And probably more noticeable if a steering wheel were used rather than a keyboard as well. There was again no obvious overshoot and no noticeable trailing from slower than optimal pixel response times. Clearly an excellent balance had been struck with the grey to grey acceleration on this monitor, even at 165Hz.

To wrap up, we tested out Blu-ray movie titles. There were no weaknesses caused by less than optimal or stronger than optimal pixel overdrive; no trailing or overshoot was evident from the monitor. There was plenty of perceived blur and an overall visual fluidity that was severely impacted by the 24fps or so at which the titles run, however. There was a slight advantage to running the monitor at a multiple of this 24fps, such as 120Hz or 144Hz rather than 165Hz (or 60Hz) for movie watching. This reduces juddering due to the fact the frame rate fits neatly into the refresh rate. The monitor also offers a 24Hz option for purists out there, and this seemed to work as intended without frame skipping or other issues.

G-SYNC – the technology and activating it

G-SYNC is a variable refresh rate technology, available when compatible Nvidia GPUs are connected to compatible monitors such as this one. In our article on the technology, we explore the mechanisms of this and look at the benefits it brings to the user. We don’t intend to repeat this but will just reiterate the basic concept. ‘G-SYNC’ monitors have a proprietary chip inside the monitor that replaces the traditional scaler and some of the assistive electronics of the monitor. The monitor and GPU are able to communicate with each other in a way that allows the monitor to dynamically adjust its refresh rate according to the frame rate of the content. This synchronisation eliminates the tearing and juddering (VSync off) or stuttering (VSync on) that occurs where refresh rate and frame rate are misaligned. In addition to this, latency is reduced compared to VSync on (although we don’t have to means to accurately measure this, as mentioned earlier).

The S2417DG supports Nvidia G-SYNC via DP 1.2a (the DisplayPort input of the monitor) when used alongside a compatible GPU with a variable refresh rate range of 30 – 165Hz. This automatically activated for us when the monitor was first connected, and this is usual behaviour. If G-SYNC is active you will see ‘G-SYNC Mode’ listed at the bottom of the OSD, next to the current resolution and refresh rate. To ensure things are set up correctly do the following. Open Nvidia Control Panel and navigate to ‘Display – Set Up G-SYNC’. Ensure that the checkbox for ‘Enable G-SYNC’ is checked and then select your preferred operating mode. As shown in the image below, the technology will work both in ‘Full Screen’ and ‘Window’ modes, depending on the selected option. If there doesn’t seem to be a G-SYNC section in your Nvidia Control Panel, try unplugging the monitor and plugging it into a different DP output on the GPU. Or failing that, reinstall the GPU driver.

Enable G-SYNC

The next step after enabling the technology is to navigate to ‘Manage 3D settings’, where you will see two settings of interest. The first of these is ‘Monitor Technology’, which should be set to ‘G-SYNC’ as shown below.

Set Monitor Technology to G-SYNC

The second setting of interest is VSync. This can be set to; ‘On’, ‘Use the 3D application setting’, ‘Off’ or ‘Fast’ (GPU dependent). If ‘On’ is selected, VSync activates once the frame rate reaches the frame rate ceiling of the monitor (i.e. up to 165Hz / 165fps). If ‘Off’ is selected, the frame rate will go as high as the system can manage – the frame rate may rise above 165fps and tearing and juddering may be visible. Nvidia initially advised that users select a definite VSync setting in the driver and disable any in-game implementation, in case that implementation interfered with the smooth running of G-SYNC. In our experience, it doesn’t make any difference whether it is enforced via the driver or the game.

Set VSync according to preferences

The ‘Fast’ setting is available on certain newer GPUs, including the GTX 1070 used in our test system. This enables ‘Fast Sync’ which comes into play where the frame rate exceeds the G-SYNC ceiling (up to 165Hz / 165fps). G-SYNC operates as usual below this whilst a special version of VSync called ‘Fast Sync’ comes into play above this. ‘Fast Sync’ is specifically designed at very high frame rates, ones that comfortably exceed the refresh rate ceiling of the monitor by quite some margin. The technique is supposed to combine the minimal latency of ‘VSync off’ without the level of tearing associated with that option. This is a GPU feature rather than a monitor feature, so isn’t something we’ll be exploring in depth. We’d advise referring to this section of a video by Tom Petersen if you’re interested in the technology and how it works alongside G-SYNC.

Regardless of which VSync setting you select, the refresh rate of the monitor behaves in exactly the same way where the frame rate dips below the floor of operation (lowest refresh rate / frame rate supported which is 30Hz / 30fps). The monitor will stick to multiples of the frame rate with its refresh rate, essentially eliminating stuttering and tearing from situations where the frame rate and refresh rate are not perfectly matched or in neat multiples. If the game dropped to 26fps, for example, the monitor would run at 46Hz rather than simply staying at 30Hz or switching to a static 165Hz. Whilst this is effective in combating stuttering and tearing, low frame rates are still low frame rates regardless of G-SYNC and the experience is far from fluid. Also note that stuttering issues related that have nothing to do with the refresh rate and frame rate mismatch (latency, low RAM etc.) will not be rectified either.

G-SYNC – the experience

We tested G-SYNC on a range of titles including Tom Clancy’s The Division, Star Wars Battlefront and Dirt Rally. The technology worked flawlessly on titles we tested and did exactly what it set out to do. Instead of repeating observations over a range of titles, which would be similar, we will be focusing on Battlefield 1 (BF1). This offers a suitable range of graphics options to allow G-SYNC to be tested over its full range of frame rates and refresh rates. Using settings we are happy to use there was a fair bit of fluctuation in frame rate, but it generally kept to triple digits (between 100fps and 165fps). Without G-SYNC active and a static 165Hz refresh rate used, these fluctuations and departures from the refresh rate would cause obvious (to us) tearing and juddering with VSync off and obvious (to us) stuttering with VSync on. With G-SYNC active these interruptions were not present and the overall experience was significantly smoother and more enjoyable. There was still benefit where the framerate was at the upper end of the range, though, as this decreased perceived blur by a fair bit. It also improved the ‘connected feel’ and as far as framerate goes it was still a case of ‘the higher the better’ in that respect, regardless of G-SYNC.

If we increased the eye candy by enabling the ‘Ultra’ preset, the frame rate dropped to around 80fps, with fluctuations typically between around 60 – 100fps. Without G-SYNC this again caused tearing and juddering (VSync off) or stuttering (VSync on), both of which were somewhat more noticeable at these reduced frame rates and something we found quite jarring. The perceived blur and connected feel was again impacted by these reduced frame rates in a negative way, but playability was certainly improved compared to with G-SYNC disabled. By increasing ‘Resolution Scale’ beyond 100% the demand on the GPU was increased significantly and unsurprisingly framerate took a hit. As framerate fell away the ‘connected feel’ became more of a ‘disconnected feel’ and perceived blur increased to new levels, but the lack of stuttering and tearing was maintained regardless. This was even the case below the 30fps minimum that G-SYNC could handle by direct refresh rate matching (30Hz), with the monitor keeping tearing and stuttering in check by settings its refresh rate to multiples of the frame rate.

We certainly felt that G-SYNC was beneficial to the gaming experience. Low frame rates were low frame rates regardless and we preferred the frame rate to be as high as possible, but the slight mismatches that were pretty much inevitable on titles like BF1 were far more palatable with G-SYNC. It’s worth remembering that individual sensitivity to tearing and stuttering varies. Whilst some users are quite sensitive to it and therefore find it noticeable and bothersome, others don’t really mind it so much. In our experience most users do find a degree of benefit from G-SYNC, sometimes a significant one, and find it difficult to go back to gaming on monitors without such a variable refresh rate technology.

ULMB – the technology and activating it

ULMB (Ultra Low Motion Blur) is another proprietary Nvidia technology which can be enabled instead of G-SYNC on compatible models. This is a strobe backlight technology specifically designed to reduce motion blur using the mechanism described here. Essentially the backlight rapidly pulses on (‘on phase’) and off’ (‘on phase’), with the ‘on’ phases being much briefer than the ‘off’ phases. This strobing behaviour greatly reduces the amount of time that your eyes spend tracking motion on the screen. As it is eye movement that is the most significant contributor to perceived blur on a modern monitor, the perceived blur is greatly reduced. ULMB requires a compatible Nvidia GPU and we would again like to stress that this option can’t be activated at the same time as G-SYNC.

ULMB can be enabled by first setting the monitor to 85Hz, 100Hz or 120Hz via Windows or the Nvidia Control Panel. The next step is to navigate to ‘Manage 3D settings’ in the Nvidia Control Panel and select ‘ULMB’ for ‘Monitor Technology’ as below. There is also a ‘ULMB’ setting in the ‘Display’ section of the OSD of the monitor, which should be set to ‘Enable’. An additional setting called ‘Pulse Width’ can be configured in the OSD, which adjusts the length of the ‘on phase’. A lower setting reduces the length of the ‘on phase’, resulting in a dimmer image but potentially offering further improvement in motion clarity. Most users will find the clarity to be excellent even with the default setting of ‘100’, however.

Set Monitor Technology to ULMB

The first sign that ULMB has activated successfully is that the screen will begin to flicker at a frequency matching the refresh rate, much like an old CRT. The image may appear dimmer as explained earlier in the review. If you open up the main OSD menu of the monitor you will also see ‘ULMB Mode’ at the bottom rather than ‘Normal Mode’ or ‘G-SYNC Mode’, next to the current resolution and refresh rate.

ULMB – the experience

Upon activating ULMB you will notice the aforementioned flickering, which is very obvious at 85Hz but still something we noticed quite easily at 100Hz or 120Hz. The image also appeared a bit dimmer (less so at 85Hz). Individual preferences for brightness and sensitivity to flickering does vary, so some users will not mind either the reduced potential brightness or the flickering. The motion clarity is excellent with ULMB active, even at 85Hz, as demonstrated with the UFO Motion Test pursuit photographs earlier. The testing below focuses on experience at 120Hz, as this was best in terms of ‘connected feel’ and having the least amount of flicker.

We tested a broad number of titles with this mode and found it brought much the same advantages regardless. We will be focusing on BF1 for this section. Provided that the frame rate matched the refresh rate perfectly (in this case, 120Hz), the level of perceived blur was extremely low and hence the overall motion clarity was excellent. Whether diving and engaging enemies in an aircraft or zipping around on foot, the sharpness and focus retained in the game world even during rapid movement was exceptional. This was a significant improvement over 165Hz with the technology disabled. For this to work, though, the frame rate absolutely needs to match the refresh rate exactly. That is because there is very little motion blur to mask stuttering (VSync on) or tearing and juddering (VSync off) and such imperfections stick out like a sore thumb. Things simply look wrong where the frame rate and refresh rate doesn’t match, with ULMB active.

Another issue associated with ULMB is the use of strong pixel overdrive, bringing with it inverse ghosting as shown earlier. This wasn’t really as obvious in-game as it is when staring at static photographs specifically highlighting it, though. It generally appears as a faint partially transparent or slightly shadowy trail behind some objects. Because the backlight is strobing, it appears quite distinct from the object – like a faint repetition of the object rather than a smooth trail behind it. All monitors using ULMB have this to either a similar or more extreme degree and we don’t feel it really detracts from the overall benefits of the technology. For most users, though, we feel G-SYNC will be preferred – note again that you can’t use both technologies at the same time. The flexibility it provides with frame rate, level of 165Hz ‘connected feel’ (which is better than the 120Hz maximum of ULMB) and lack of flicker will see a mass appeal that ULMB doesn’t. But it’s definitely a useful tool for some users, particularly those who are used to gaming on CRTs or play titles where consistently high frame rates and extreme paces of action are the norm.

3D Vision 2

This monitor supports Nvidia 3D Vision (1 and 2). An emitter is not integrated into the monitor, but the technology will work provided you have the full kit (emitter + glasses). You can set this up once the emitter is plugged in by opening Nvidia Control Panel and navigating to ‘Stereoscopic 3D – Set up stereoscopic 3D’. You then select the ‘Enable stereoscopic 3D’ checkbox and run through the setup procedure. The image below shows this section of the Nvidia Control Panel.

Activate 3D Vision