ViewSonic VX2475Smhl-4K

Responsiveness

Input lag

A sensitive camera and a utility called SMTT 2.0 was used to assess the input lag of the VX2475Smhl-4K. The monitor was compared to various monitors of known latency. Using this method, we calculated 5.23ms (under 1/3 of a frame) of input lag. This value is influenced both by the signal delay (element you ‘feel’) and pixel responsiveness (element you ‘see’) and indicates that the monitor has a very low signal delay that shouldn’t specifically bother even sensitive users.

Perceived blur (pursuit photography)

In this article we introduce the concepts of ‘pursuit photography’ and ‘perceived blur’. Unlike traditional static photographs, pursuit photography uses a moving camera to capture movement on a screen in a way that more accurately reflects what the eye actually sees. Not only is the pixel response behaviour captured (including trailing, inverse ghosting and any additional artifacts), the movement of the camera simulates the natural pursuit tracking movement of our eyes as we observe motion on the screen. These factors combine to produce what is known as ‘perceived blur’ – and eye movement generally contributes to this more significantly than pixel responsiveness.

The following images are pursuit photographs taken on the UFO Motion Test for ghosting, with the test running at 960 pixels per second. This is a practical speed for this sort of photography and highlights the key aspects of perceived blur nicely. The monitor was set to its three ‘Response Time’ settings; ‘Standard’, ‘Advanced’ and ‘Ultra Fast’, respectively. The medium cyan background (middle row of the test) was used in all cases, with an additional capture with the light cyan background (bottom row of the test) for the ‘Advanced’ setting. The final photograph shows a fast 60Hz reference – a Samsung S27A750D set to full brightness (to eliminate PWM) and 60Hz, using the ‘Faster’ response time setting.

Perceived blur with various settings

Using the ‘Standard’ setting there is a bit of trailing on top of the blur that is observed due to eye movement alone (i.e. the fast 60Hz reference). This trailing is caused by slower than optimal pixel responses for the transitions shown here, being boldest for the main red UFO body. The ‘Advanced’ setting cuts this down significantly, introducing just a hint of overshoot (inverse ghosting) with a little conventional trailing as well but coming closer to the fast 60Hz reference. With the light cyan background, the overshoot becomes quite a bit more pronounced. It actually looks less noticeable on the photograph than it does when you observe the UFO in motion first hand. The ‘Ultra Fast’ setting produces very obvious overshoot.

From this analysis you may be forgiven for thinking that ‘Advanced’ could be the setting to go for. However; the overshoot is rather obvious during certain transitions which aren’t necessarily explored here. These transitions crop up during game play and are painfully obvious, so will be quite bothersome to many users we feel. The higher contrast transitions tend to show this more clearly. In the example below you can see obvious overshoot as a window (Word Document) is moved at a moderate pace from left to right. This is a normal static photograph so doesn’t represent quite what the eye sees, but it does highlight the intensity of overshoot rather nicely.



We therefore preferred the ‘Standard’ setting, despite some transitions being a fair bit slower than optimal. Our analysis below shows how the additional trailing from these slower than optimal pixel responses manifests itself. Note that there will not be a section on ‘overclocking’ as the monitor could only be set to 66Hz before it went out of range. This was the case whether using DP 1.2 or HDMI 2.0 and it did not provide a noticeable benefit over 60Hz.

Responsiveness in games and movies

On Battlefield 4 there was a moderate degree of blur. This was mainly but not entirely caused by eye movement and linked to the 60Hz sample and hold nature of the display. There was a fair degree of trailing on top of this, in places. This was most readily observed where medium-dark shades moved against slightly lighter backgrounds. Dark grey painted jets or vehicles moving against an overcast sky, for example. Here you could see a fairly short-lived and reasonably faint (but still quite readily observable) trail behind the moving object. This extra trailing meant that moving rapidly in a vehicle, for example, created a bit more of a blurring of the environment than you might ideally expect from a 60Hz LCD. Not everyone will notice this and we’ve certainly seen worse cases of trailing (mainly from VA models and older IPS models), but it’s worth noting if you’re sensitive to that sort of thing. There was no observable overshoot, which is good.

The experience was similar on Dirt Rally. Even during gentle cornering there was a moderate degree of blur, intensifying even more as the pace was picked up. The overall level of blur was a bit greater than you would ideally see on a 60Hz LCD, so was not entirely attributable to eye movement. There was certainly an extra degree of trailing in places, but this wasn’t as noticeable as the additional overshoot using the ‘Advanced’ setting. In the ‘Standard’ setting, which we used, there was no observable overshoot. We don’t really feel the playability of the game was affected by the slight extra trailing and hence somewhat higher level of perceived blur than on faster 60Hz LCDs, but sensitivity to this varies and it’s worth bearing in mind nonetheless.

We also tested our Blu-ray movie test titles and didn’t find the pixel responsiveness impeded the performance here. Things were much as you’d see on any fast to moderately fast 60Hz LCD, with the ~24fps at which the frames run being a key limitation to their fluidity. There was no observable overshoot, either.

The ‘4K’ UHD experience

As we explore in this article, the ‘4K’ UHD resolution (3840 x 2160) can bring with it significant benefits for both work and play. But as far as having to rely on scaling goes, things aren’t always plain sailing depending on the applications you use. In our review of the Dell P2415Q, in this same section, we take a look at how things work out with the UHD resolution on a 23.8” screen. As this screen is 23.6”, the experience is as good as identical in that regard – so we won’t be repeating a lot of that here. The pixel density of this one is 186.69 PPI (Pixels Per Inch), which is very high indeed. Again, we found 150% scaling in Windows provided a good balance between readability and real-estate. Running the monitor at its native 100% setting (i.e. no scaling) made text, icons, buttons and other elements completely tiny. On applications with independent zoom control (Microsoft Word, web browsers etc.) this could be overcome for the main body of text but really we found scaling something of a necessity on such a small screen. The photos below show the desktop without scaling (top photo) and with our preferred 150% setting (bottom photo, taken from earlier in the review).

As noted in the relevant section on the P2415Q review, the 150% setting still gives you a good amount of useful desktop real-estate. And indeed when gaming, where scaling settings like this don’t apply, the excellent pixel density has the potential to bring a great amount of detail and clarity. To reiterate, we don’t actually find the extra pixel density compared to 27”, 28” or even 31.5” – 32” UHD screens to be beneficial when gaming. Things really look rather similar in terms of detail and clarity, but just smaller. So the advantage in that respect isn’t really there, it’s more that some people prefer slightly smaller (~24”) screens or don’t have the budget or desk space for anything larger. We’ll round off this section with a few photos taken with the monitor ‘in action’ on a few game titles. This in no way represents what you actually see first-hand when using the monitor, it’s purely for illustrative purposes.

Interpolation and upscaling

The native UHD resolution of 3840 x 2160 brings with it excellent clarity on this screen. It is also very demanding to run for certain graphically demanding applications such as some modern game titles. Some systems (games consoles, for example) also simply don’t support this resolution. It may therefore be tempting or indeed necessary to reduce the resolution to 1920 x 1080 (Full HD), or perhaps 2560 x 1440 (WQHD) as a PC user. When you do this, the monitor uses an interpolation (scaling) process to map the lower resolution content onto its greater number of pixels to ensure that the whole screen is used. This is best handled by the monitor itself rather than the GPU. AMD GPU users needn’t worry about this as it’s automatically handled by the monitor when gaming, by default. Nvidia users should open their Nvidia Control Panel and navigate to ‘Display – Adjust desktop size and position’. They should ensure that ‘No Scaling’ is selected and ‘Perform scaling on:’ is set to ‘Display’ as shown below.

Contrary to popular belief, the fact that 1920 x 1080 could theoretically be displayed ‘perfectly’ without a loss of clarity compared to a native Full HD display doesn’t mean that it actually is in practice. Indeed the same sort of interpolation process is used whether you’re trying to display 1920 x 1080 or a resolution without such a neat division, like 2560 x 1440. It isn’t all bad news, though. The interpolation process used by the ViewSonic VX2475Smhl-4K is one of the better ones we’ve come across. There is a loss of sharpness when compared to running the resolution (1920 x 1080 or 2560 x 1440) on a screen of similar size. Things look somewhat softer and less clearly defined. This softening is not severe, though, and is far more subtle than we’ve seen on quite a few other monitors (including several ‘4K’ ones). We therefore feel that, whilst not ideal for the task, the monitor is certainly quite useable and does a pretty decent job at running such non-native resolutions.

Note that if you’re running 1920 x 1080 (Full HD) content using movie software or a web browser on the PC and have the monitor running at its native 3840 x 2160 resolution, the GPU or software handles the upscaling. The monitor itself has no influence over this – there is a slight degree of softening that’s quite comparable to the monitors own interpolation when running 1920 x 1080. Another interesting point to note is that the monitor can be set to the ‘4096 x 2160’ (‘True 4K’ or DCI 4K) resolution. It doesn’t magically sprout extra pixels and instead uses an interpolation process of sorts. The end result is an image with roughly similar clarity to the native resolution, but slightly compressed horizontally. It’s designed to simulate a DCI 4K environment for editing purposes.

Conclusion

The ViewSonic VX2475Smhl-4K is designed as a relatively inexpensive entrance into the world of ‘4K’ UHD computing. The low price is reflected by the less than stellar build quality and lack of ergonomic flexibility with the included stand. And although low price is no excuse for this, the OSD controls were some of the worst we’ve come across on a monitor. However; the low price is not reflected by the image performance, which was quite impressive overall. Static contrast was much as you’d expect given the panel type, but the overall experience was enhanced by the somewhat reduced level of ‘PLS glow’. The screen surface also helped invite more vibrancy and clarity compared to some matte surfaces, although the surface texture was still slightly grainy rather than completely smooth looking. It wasn’t too obtrusive, even if we would have preferred to see a smoother texture used.

The colour quality was pleasing, with strong gamma tracking straight from the box. The white point did require some rebalancing, necessitating switching the ‘User Color’ which had slightly slacker gamma tracking but slightly stronger contrast. The gamma tracking was still more than adequate for general use. The subpixel layout of the monitor also introduced some faint interlacing where the red subpixel was dominant, but we could not see this from a normal viewing distance and don’t suspect most users will even notice it. The monitor fully covered the sRGB colour space and extended a bit beyond. Not troublingly so and certainly not into wide gamut territory, but just enough to invite a bit of extra vibrancy which most users will welcome. The 3840 x 2160 resolution is, of course, a headline feature. And the real-estate, clarity and detail benefits that this brings for both work and play were certainly appreciated.

When it came to responsiveness things were a bit mixed really. The ‘Standard’ setting was free from observable overshoot and did quite a decent job within the confines of the 60Hz refresh rate, but there were some underlying weaknesses in pixel responsiveness here and there. The ‘Advanced’ setting sped up some of these slightly slower pixel transitions, but brought with it a level of overshoot that we found quite obvious in places and less tolerable than the slightly higher trailing in ‘Standard’ mode. The input lag was very good on this model, too, with no real signal delay to speak of. Overall then, this monitor put in a pretty strong performance and hits a good sweet spot between price and performance. As with any model it does have its weaknesses and for some users the greater ergonomic flexibility and pixel responsiveness of the Dell P2415Q could prove more attractive.

The bottom line; a keenly priced monitor with a no-frills appearance and lack of ergonomic flexibility, but strong image performance overall.

 

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