Introduction

Acer are perhaps more well known for their wide range of gaming monitors, primarily their extensive 'Predator' range. We have with us now the new 31.5"sized model in their other 'ProDesigner' range of displays. This model is aimed more at professional users and content creators and comes with a range of specs and features accordingly. There's no high refresh rate, super-fast response times or motion blur backlights on this model of course but instead it offers things like  an Ultra HD 3840 x 2160 resolution, wide colour gamut support (although oddly not really promoted much on Acer's website), a sleek 4-side borderless design, factory calibration and plenty of calibration settings and controls. Although it's not a gaming screen Acer have still included support for AMD FreeSync and talk about an "ultra low input lag technology" to hopefully minimise delays.

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Specifications and Features

The following table gives detailed information about the specs of the screen as advertised:

The PE320QK offers a good range of modern connectivity options with 1x DisplayPort 1.2, 2x HDMI 2.0 and 1x USB 3.1 type-C connections offered. The digital interfaces are HDCP certified for encrypted content and the video cables are provided in the box for all three which is great news.

The screen has an internal power supply and comes packaged with the power cable you need. There are also 4x USB 3.1 ports, 2 located on the back of the screen with the video connections and 2 for easy access on the left hand side of the screen (1 has fast charging support). An audio out connection is also provided if you need it along with integrated 2x 2W stereo speakers.

Below is a summary of the features and connections of the screen:

Power Consumption

In terms of power consumption the manufacturer lists typical usage of 41.0W, and 0.5W in standby. We carried out our normal tests to establish its power consumption ourselves.

Out of the box the screen used 45.9W at the default 80% brightness setting. Once calibrated the screen reached 26.5W consumption, and in standby it used only 1.1W. We have plotted these results below compared with other screens we have tested. The consumption (comparing the calibrated states) is a little higher than most 27" models due to the slightly bigger screen size (and therefore backlight), but less than the larger 34 - 38" models for the same reason.

Panel and Backlighting

Panel Part and Colour Depth

The Acer ProDesigner PE320QK features an LG.Display LM315WR1-SSB1 IPS technology panel which is capable of producing 1.07 billion colours. This is achieved through a native 8-bit colour depth and additional FRC stage (8-bit+FRC). Keep in mind whether this 10-bit support is practically useable for you and whether you're ever going to truly use that colour depth. You need to have a full 10-bit end to end workflow to take advantage of it which is still quite expensive to achieve and rare in the market, certainly for your average user. This includes relevant applications and graphics cards as well, so to some people this 10-bit support might be irrelevant. Given this is a higher end, professional screen the 10-bit support is useful and may well be required for some users.

The panel part is confirmed when dismantling the screen as shown below:

Screen Coating

The screen coating is a light anti-glare (AG) like other modern IPS panels. It retains its anti-glare properties to avoid too many unwanted reflections of a full glossy coating, but does not produce an too grainy or dirty an image that some thicker AG coatings can, including much older IPS panels. There are no visible cross-hatching patterns on the screen.

Backlight Type and Colour Gamut

The screen uses a White-LED (W-LED) backlight unit which is standard in today's market. This helps reduce power consumption compared with older CCFL backlight units and brings about some environmental benefits as well. We know that the screen shows a colour space beyond the typical sRGB coverage you get from W-LED. Acer inform us that it is some kind of wide gamut backlight being used here as opposed to Quantum Dot coating as we originally thought might be used.

Regardless of how it is achieved, this helps push the colour space of the screen up towards the now-popular DCI-P3 reference that is used for HDR displays in the market. This gives rise to the measured 131% sRGB coverage, showing that it extends 31% beyond the typical 100% coverage a common W-LED backlight monitor would offer. This equates to 96.6% DCI-P3 coverage according to our measurements in the following sections, helping deliver a wider colour gamut and also meet certain defined standards for HDR content. We will talk about that HDR support later on in the review. It might not offer quite the same wide gamut as some displays (e.g. the Dell UP2718Q with GB-r-LED backlight offers 146% sRGB) but it is a half-way house suited for wide gamut multimedia content.

If you want to read more about colour spaces and gamut then please have a read of our detailed article.

Backlight Dimming and Flicker

We tested the screen to establish the methods used to control backlight dimming. Our in depth article talks in more details about a previously very common method used for this which is called Pulse Width Modulation (PWM). This in itself gives cause for concern to some users who have experienced eye strain, headaches and other symptoms as a result of the flickering backlight caused by this technology. We use a photosensor + oscilloscope system to measure backlight dimming control with a high level of accuracy and ease. These tests allow us to establish

1) Whether PWM is being used to control the backlight
2) The frequency and other characteristics at which this operates, if it is used
3) Whether a flicker may be introduced or potentially noticeable at certain settings

If PWM is used for backlight dimming, the higher the frequency, the less likely you are to see artefacts and flicker. The duty cycle (the time for which the backlight is on) is also important and the shorter the duty cycle, the more potential there is that you may see flicker. The other factor which can influence flicker is the amplitude of the PWM, measuring the difference in brightness output between the 'on' and 'off' states. Please remember that not every user would notice a flicker from a backlight using PWM, but it is something to be wary of. It is also a hard thing to quantify as it is very subjective when talking about whether a user may or may not experience the side effects.

100%                                                     50%                                                     0%
 
Above scale = 1 horizontal grid = 5ms

 

Contrast Stability and Brightness

The brightness control gave us a good range of adjustment. At the top end the maximum luminance reached 322 cd/m² which was a little lower than the specified maximum brightness of 350 cd/m² from the manufacturer. There was a good 246 cd/m² adjustment range in total, and so at the minimum setting you could reach down to a fairly low luminance of 76 cd/m². This should probably be adequate for most people wanting to work in darkened room conditions with low ambient light although it doesn't reach as low as some screens. A setting of 18 in the OSD menu should return you a luminance of around 120 cd/m² at default settings. It should be noted that the brightness regulation is controlled without the need for Pulse Width Modulation for all brightness settings so the screen is flicker free.

    

We have plotted the luminance trend on the graph above. The screen behaves as it should in this regard, with a reduction in the luminance output of the screen controlled by the reduction in the OSD brightness setting. This is a linear relationship as you can see.

The average contrast ratio of the screen was excellent for an IPS technology panel, measured at 1403:1. It remained mostly stable across the brightness adjustment range.

Testing Methodology

An important thing to consider for most users is how a screen will perform out of the box and with some basic manual adjustments. Since most users won't have access to hardware colorimeter tools, it is important to understand how the screen is going to perform in terms of colour accuracy for the average user.

We restored our graphics card to default settings and disabled any previously active ICC profiles and gamma corrections. The screen was tested at default factory settings using our new X-rite i1 Pro 2 Spectrophotometer combined with LaCie's Blue Eye Pro software suite. An X-rite i1 Display Pro colorimeter was also used to verify the black point and contrast ratio since the i1 Pro 2 spectrophotometer is less reliable at the darker end.

Targets for these tests are as follows:

• CIE Diagram - validates the colour space covered by the monitors backlighting in a 2D view, with the black triangle representing the displays gamut, and other reference colour spaces shown for comparison

• Gamma - we aim for 2.2 which is the default for computer monitors

• Colour temperature / white point - we aim for 6500k which is the temperature of daylight

• Luminance - we aim for 120 cd/m², which is the recommended luminance for LCD monitors in normal lighting conditions

• Black depth - we aim for as low as possible to maximise shadow detail and to offer us the best contrast ratio

• Contrast ratio - we aim for as high as possible. Any dynamic contrast ratio controls are turned off here if present

• dE average / maximum - as low as possible. If DeltaE >3, the color displayed is significantly different from the theoretical one, meaning that the difference will be perceptible to the viewer. If DeltaE <2, LaCie considers the calibration a success; there remains a slight difference, but it is barely undetectable. If DeltaE < 1, the color fidelity is excellent.

Default Performance and Setup

Default settings of the screen were as follows:

Initially out of the box the screen was set in the 'standard' preset mode, and with a high 80% brightness which was too bright and uncomfortable to use. You will definitely need to turn that down. The colours felt bright and vivid and you could tell the screen was offering a wide gamut beyond normal sRGB screens.

We went ahead and measured the default state with the i1 Pro 2. The CIE diagram on the left of the image confirms that the monitors colour gamut (black triangle) extends a considerable amount beyond the sRGB colour space (orange triangle). We measured using ChromaPure software a 131.0% sRGB gamut coverage which corresponds to 96.6% of the DCI-P3 reference and 69.3% of the Rec.2020 reference. Acer inform us that it is some kind of wide gamut backlight being used here as opposed to Quantum Dot coating as we originally thought might be used.

Colour space comparison vs. DCI-P3 reference

The above CIE diagram plots the monitors native gamut (black triangle) against the DCI-P3 reference space (white triangle) and you can see that the two are very closely aligned.

Default gamma was recorded at an accurate 2.2 average, with a very small 1% deviance from the target. White point was measured at an accurate 6407k which left it a very small 1% out from the 6500k we'd ideally want for desktop use. There are a range of other colour temp presets available in the menu along with a user configurable 'user' mode where you have access to the individual RGB channels for the calibration process.

Luminance was recorded at a bright 270 cd/m² which is too high for prolonged general use, you will need to turn that down. The screen was set at a default 80% brightness in the OSD menu but that is easy to change of course to reach a more comfortable setting without impacting any other aspect of the setup. The black depth was 0.20 cd/m² at this default brightness setting, giving us a very strong static contrast ratio for an IPS-type panel of 1353:1. Colour accuracy was moderate out of the box with an average dE of 2.8, but a max of 6.8. Testing the screen with colour gradients showed very smooth gradients with only very minor gradation evident in the darker tones. There was no sign of any colour banding which was good news.

 

Factory Calibration

The screen carries a factory calibration in the sRGB preset mode, designed to deliver low dE of <1, and a pre-tuned 6500k white point and 2.2 gamma curve. An individual report is provided in the box as shown with our example below:

The settings of the screen were as follows in this sRGB mode. Note that many settings are now locked including contrast, gamma, colour temp. You can still change the brightness control thankfully to reach a suitable luminance.

In the sRGB preset mode you can see first of all that the gamut is being nicely emulated to match the sRGB colour space. The CIE diagram on the left shows that the two triangles match pretty closely now, and certainly cut down on the large over-coverage we had seen with the native gamut in the 'standard' mode. Using ChromaPure software we measured a 97.0% sRGB coverage in this mode, so for those who want to work with standard sRGB content more accurately, this preset provides a suitable and reliable option.

Gamma was measured at an accurate 2.2 average, with only a small 2% deviance recorded. Despite the factory calibration seemingly aiming for 6500k white point, the measured white point in this mode was actually much nearer to 6000k, recorded here at 5943k. dE was 1.1 average which was excellent, although blue shades seem to show a larger error up to 5.7 max. Contrast ratio dipped slightly but remained very strong for an IPS panel at 1257:1. Again colour gradients were very smooth with only minor gradation in darker tones visible. Overall the factory calibration was very good. It might have been nice to see a factory calibration available from the native DCI-P3 oriented gamut as well..

Calibration

We used the X-rite i1 Pro 2 Spectrophotometer combined with the LaCie Blue Eye Pro software package to achieve these results and reports. An X-rite i1 Display Pro colorimeter was used to validate the black depth and contrast ratios due to lower end limitations of the i1 Pro device.

We first of all switched to the 'User' preset mode which gives you access to adjust the RGB channels individually but will leave the screen in the full native gamut for now. If you want to work with the sRGB colour space then the factory calibration is good and will suit most needs. You can always carry out a further profiling of the screen in the sRGB mode if you have a calibration device, although note that corrections will need to be made at the graphics card level primarily, because access to RGB channels are not available in that preset.

We adjusted the RGB channels and brightness setting as shown in the table above as part of the guided calibration process. These OSD changes allowed us to obtain an optimal hardware starting point and setup before software level changes would be made at the graphics card level. We left the  LaCie software to calibrate to "max" brightness which would just retain the luminance of whatever brightness we'd set the screen to, and would not in any way try and alter the luminance at the graphics card level, which can reduce contrast ratio. These adjustments before profiling the screen would help preserve tonal values and limit banding issues. After this we let the software carry out the LUT adjustments and create an ICC profile. Note that after making changes to the OSD controls you also need to access the "save settings to" section in the menu to save them over one of the existing preset modes (e.g. over the 'user' mode).

Average gamma was corrected now nicely to 2.2 average which fixed the minor 1% deviance we'd seen out of the box. The small 1% white point deviance had now been corrected bringing the measured white point to 6488k. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at a far more comfortable 120 cd/m². This left us a black depth of 0.08 cd/m² and a static contrast ratio of 1468:1 which was excellent for an IPS panel. Colour accuracy of the resulting profile was excellent too, with dE average of 0.4 and maximum of 1.2. LaCie would consider colour fidelity to be excellent. Testing the screen with various colour gradients showed mostly smooth transitions with only some minor gradation in darker tones. You can use our settings and try our calibrated ICC profile if you wish, which are available in our ICC profile database. Keep in mind that results will vary from one screen to another and from one computer / graphics card to another.

Calibration Performance Comparisons

The comparisons made in this section try to give you a better view of how each screen performs, particularly out of the box which is what is going to matter to most consumers. We have divided the table up by panel technology as well to make it easier to compare similar models. When comparing the default factory settings for each monitor it is important to take into account several measurement areas - gamma, white point and colour accuracy. There's no point having a low dE colour accuracy figure if the gamma curve is way off for instance. A good factory calibration requires all 3 to be well set up. We have deliberately not included luminance in this comparison since this is normally far too high by default on every screen. However, that is very easily controlled through the brightness setting (on most screens) and should not impact the other areas being measured anyway. It is easy enough to obtain a suitable luminance for your working conditions and individual preferences, but a reliable factory setup in gamma, white point and colour accuracy is important and some (gamma especially) are not as easy to change accurately without a calibration tool.

From these comparisons we can also compare the calibrated colour accuracy, black depth and contrast ratio. After a calibration the gamma, white point and luminance should all be at their desired targets.

Default setup of the screen out of the box was good, even in the non-factory calibrated standard mode. There was very minor 1% deviance in the gamma curve and white point, and a fairly low average dE of 2.8 measured. You need to keep in mind that in the standard mode there is an extended colour gamut (~131% sRGB coverage) and so this mode might not be suitable or desirable for everyone. If you are working with wider gamut content, or want the added boost in colour vividness that you get from a wider gamut then the mode is fine of course. If you want to work more accurately with sRGB content, there is also a nice factory calibrated sRGB preset mode which has a good setup and a reliable emulation of the smaller sRGB colour space.

Where the PE320QK really excels is in black depth and contrast ratio. Not compared with VA panels of course which as you can see reach up to around 2000 - 2500:1 or so as you can see from the models on the right hand side above. That's a strength of VA technology for sure. IPS panels have been limited to around 1000:1 maximum for many years though, with the odd screen exceeding slightly beyond that such as the Dell U2515H (1138:1). However, this is the first IPS-based screen we have tested which has really shown a big jump in static contrast ratio, with the PE320QK reaching 1468:1. We have seen contrast ratios of recent IPS panels from LG.Display with a 1400:1 specs on paper, but this is the first display we've tested where this has been genuinely achieved. Great to see that higher contrast ratio from an IPS screen. Long may it continue.

Viewing Angles

Above: Viewing angles shown from front and side, and  from above and below. Click for larger image

Viewing angles of the screen were very good as you would expect from an IPS panel. Horizontally there was very little colour tone shift until wide angles past about 45. A slight darkening of the image occurred horizontally from wider angles as you can see above as the contrast shifted slighting. Contrast shifts were slightly more noticeable in the vertical field but overall they were very good. The screen offered the wide viewing angles of IPS technology and was free from the restrictive fields of view of TN Film panels, especially in the vertical plane. It was also free of the off-centre contrast shift you see from VA panels and a lot of the quite obvious gamma and colour tone shift you see from some of the modern VA panel type offerings. All as expected really from a modern IPS panel.

Above: View of an all black screen from the side. Click for larger version

On a black image there is a characteristic white glow when viewed from an angle, commonly referred to as "IPS-glow". This is common on most modern IPS-type panels and can be distracting to some users. If you view dark content from a normal head-on viewing position, you can actually see this glow as your eyes look towards the edges of the screen. Because of the large size of this 31.5" panel, the glow towards the edges is more obvious than on small screens, where there isn't such a long distance from your central position to the edges. Some people may find this problematic if they are working with a lot of dark content or solid colour patterns. In normal day to day uses, office work, movies and games you couldn't really notice this unless you were viewing darker content. If you move your viewing position back, which is probably likely for movies and games, the effect reduces as you do not have such an extreme angle from your eye position to the screen edges.

Panel Uniformity

We wanted to test here how uniform the brightness was across the screen, as well as identify any leakage from the backlight in dark lighting conditions. Measurements of the luminance were taken at 35 points across the panel on a pure white background. The measurements for luminance were taken using BasICColor's calibration software package, combined with an X-rite i1 Display Pro colorimeter with a central point on the screen calibrated to 120 cd/m². The below uniformity diagram shows the difference, as a percentage, between the measurement recorded at each point on the screen, as compared with the central reference point.

It is worth noting that panel uniformity can vary from one screen to another, and can depend on manufacturing lines, screen transport and other local factors. This is only a guide of the uniformity of the sample screen we have for review.

Uniformity of Luminance

Uniformity of the screen was fairly poor on this sample. The sides and bottom part of the screen were a fair bit darker than the central and upper area, particularly down the left hand side where luminance dropped as low as 93 cd/m² in the most extreme example. Only 34% of the screen remained within a 10% threshold of the centrally calibrated point. Sadly there is no uniformity correction mode on this screen despite its target market.

Backlight Leakage

Above: All black screen in a darkened room. Click for larger version

We also tested the screen with an all black image and in a darkened room. A camera was used to capture the result. The camera showed there was no noticeable backlight bleed or clouding on this sample which was great news.

Note: if you want to test your own screen for backlight bleed and uniformity problems at any point you need to ensure you have suitable testing conditions. Set the monitor to a sensible day to day brightness level, preferably as close to 120 cd/m² as you can get it (our tests are once the screen is calibrated to this luminance). Don't just take a photo at the default brightness which is almost always far too high and not a realistic usage condition. You need to take the photo from about 1.5 - 2m back to avoid capturing viewing angle characteristics, especially on IPS-type panels where off-angle glow can come in to play easily. Photos should be taken in a darkened room at a shutter speed which captures what you see reliably and doesn't over-expose the image. A shutter speed of 1/8 second will probably be suitable for this.

General and Office Applications

The PE320QK feature a 3840 x 2160 Ultra HD resolution on a 31.5" sized screen. The higher resolution is not really about providing more screen real-estate here and we need to move away from thinking about LCD resolution in that manner. Some users may get away with using the full native resolution without any scaling to offer a much larger desktop area, as the 31.5" screen size makes it somewhat possible. We felt though that text is just too small even on this relatively large screen due to the 0.1816 mm pixel pitch. You probably need a screen around 40" in size we think to make an Ultra HD resolution comfortable without scaling being used.

Here, like most smaller screens with 4K-type resolution it is about providing a sharper and crisper image, while still operating with a similar desktop area and similar font size to a 1440p resolution. It is providing a higher pixel density (Pixels Per Inch, PPI = 140) to improve the degree of definition to the image. You need to us operating system scaling to handle this properly. On this 31.5" model, if you increase the scaling to 150%, you actually end up with the same workspace area as 2560 x 1440, but at a much higher PPI pixel density - and therefore a sharper image. Have a read of Eizo's very useful article for some more information on the whole matter. For those wanting a high pixel density for CAD, design, photo work etc, this is a really good option. The image was very sharp and crisp and text was very clear.

Keep in mind that not all Operating Systems and applications handle scaling the same. More recent versions of Windows (8.1 and 10) tend to handle it all better, and recent versions of Mac OS are pretty solid as well. Some applications and games don't handle scaling correctly and so you can end up with some things with very minute text and fonts and some things which don't scale completely in every place. Keep this in mind if you're selecting any super high resolution display as it could be an important factor. You need to ensure you have the necessary operating system and applications to handle scaling effectively for your needs.

The light AG coating of the panel is welcome, and much better than the grainy and 'dirty' appearance of older IPS AG coatings from years gone by. The wide viewing angles provided by this panel technology on both horizontal and vertical planes, helps minimize on-screen colour shift when viewed from different angles. The default setup of the screen was decent as well, offering an accurate gamma curve, accurate white point, decent contrast ratio and low dE. There is an sRGB emulation mode as well if you don't want to work with the full native gamut of the screen which is closely linked to the DCI-P3 colour space. The brightness range of the screen was also very good, with the ability to offer a luminance between 322 and 76 cd/m². This should mean the screen is useable in a wide variety of ambient light conditions, including darkened rooms. A setting of ~18 in the OSD brightness control should return you a luminance close to 120 cd/m² out of the box. On another positive note, the brightness regulation is controlled without the need for the use of Pulse-Width Modulation (PWM), and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry. There was no audible noise or buzzing from the screen, even when specifically looking for it using test images with a large amount of text at once. The screen also remains cool even during prolonged use.

The screen offers 4x USB 3.0 ports (1 with charging capabilities also) which is very handy. 2 are on the left hand edge of the screen for easy access. There are also 2x 2W integrated stereo speakers which are probably ok for the odd mp3, sound clip or YouTube video. There's also a bundled shading hood for those who might want to do more colour critical work and want the added light deflection on the sides (as pictured above). There aren't any other extras like card readers or ambient light sensors offered though which can sometimes be useful in office environments. The stand offers a wide range of adjustments which is great news, allowing you to obtain comfortable viewing positions although they are quite stiff to operate so you might not want to move it around too often.

 

 
Responsiveness and Gaming

The PE320QK is rated by Acer as having a 4ms G2G response time. The screen uses overdrive / response time compensation (RTC) technology to boost pixel transitions across grey to grey changes as with nearly all modern displays. There is a user control in the OSD menu for the overdrive under the 'Over Drive' setting with 3 options available - Off, Normal and Extreme. The part being used is the LG.Display LM315WR1-SSB1 IPS technology panel.  Have a read about response time in our specs section if you need additional information about this measurement.

We use an ETC M526 oscilloscope for these measurements along with a custom photosensor device. Have a read of our response time measurement article for a full explanation of the testing methodology and reported data.

We carried out some visual tests first of all in each of the 3 Over Drive modes to try and establish which was the optimal setting for motion content. There was a small improvement in motion blur when you switch up from the 'Off' setting, to the 'Normal' setting. It wasn't a major improvement but you could see a slight sharpening of the moving image and reduction in blur. Switching up to the highest 'Extreme' setting resulted in some very obvious dark and pale halos behind the moving object. This was caused by an overly aggressive overdrive impulse and was causing a lot of overshoot. The 'Normal' mode seemed to be the best option.

We carried out our response time measurements using the oscilloscope then in the 'Normal' Over Drive mode as shown above. Overall the response times were quite  slow, with an average of only 13.3ms G2G measured. Some transitions were as slow as 20 - 22ms, and some were a bit faster down to around 9 - 10ms. It seemed that only a very modest overdrive impulse was being applied here in the 'Normal' mode and so pixel transitions were not really being sped up much. On the plus side it did mean there was no overshoot at all, but we would have liked a more adventurous application of overdrive here. The 'Extreme' mode is too aggressive though and the overshoot is very obvious and problematic. Something in between would have been nice. Remember this is not a gaming screen and at 60Hz maximum refresh rate the response times were still adequate to keep up with the frame rates.

   

The screen supports AMD FreeSync as well for dynamic refresh rates. This controls a refresh range between 30 and 60Hz. We would recommend sticking with the 'Normal' response time mode as we've said above. The addition of FreeSync is useful on a screen with this high 3840 x 2160 resolution as it helps compensate for graphics cards which cannot power the resolution reliably at 60fps. The screen is ok for some moderate gaming, but probably isn't suitable for any very fast FPS-type games given the fairly slow response times.

The PE320QK was slower than the other IPS-based screens we have compared it against here. For a 60Hz IPS panel a response time of around 8.5ms G2G seems to be about as good as you can get at the moment, with higher refresh rate screens pushing that down to around 5ms G2G.

Additional Gaming Features

• Aspect Ratio Control - the screen has 3 options for hardware level aspect ratio control options, with settings for full, aspect and 1:1 pixel mapping offered. Useful to see an auto-aspect ratio mode available to account for other formats than the native 16:9.

• Preset Modes - There are no specific preset modes set up for gaming, although you can probably change one of the other modes to your liking if you want to. Each mode can be saved within the OSD menu with customised settings which is handy.
   

• Refresh Rate num - There is a setting in the OSD to display your active refresh rate in the top right hand corner of the screen. Maybe useful to some who are tracking their refresh rate performance while gaming, and while using FreeSync.

Lag

We have written an in depth article about input lag and the various measurement techniques which are used to evaluate this aspect of a display. It's important to first of all understand the different methods available and also what this lag means to you as an end-user.

Input Lag vs. Display Lag vs. Signal Processing

To avoid confusion with different terminology we will refer to this section of our reviews as just "lag" from now on, as there are a few different aspects to consider, and different interpretations of the term "input lag". We will consider the following points here as much as possible. The overall "display lag" is the first, that being the delay between the image being shown on the TFT display and that being shown on a CRT. This is what many people will know as input lag and originally was the measure made to explain why the image is a little behind when using a CRT. The older stopwatch based methods were the common way to measure this in the past, but through advanced studies have been shown to be quite inaccurate. As a result, more advanced tools like SMTT provide a method to measure that delay between a TFT and CRT while removing the inaccuracies of older stopwatch methods.

In reality that lag / delay is caused by a combination of two things - the signal processing delay caused by the TFT electronics / scaler, and the response time of the pixels themselves. Most "input lag" measurements over the years have always been based on the overall display lag (signal processing + response time) and indeed the SMTT tool is based on this visual difference between a CRT and TFT and so measures the overall display lag. In practice the signal processing is the element which gives the feel of lag to the user, and the response time of course can impact blurring, and overall image quality in moving scenes. As people become more aware of lag as a possible issue, we are of course keen to try and understand the split between the two as much as possible to give a complete picture.

The signal processing element within that is quite hard to identify without extremely high end equipment and very complicated methods. In fact the studies by Thomas Thiemann which really kicked this whole thing off were based on equipment worth >100,1000 Euro, requiring extremely high bandwidths and very complicated methods to trigger the correct behaviour and accurately measure the signal processing on its own. Other techniques which are being used since are not conducted by Thomas (he is a freelance writer) or based on this equipment or technique, and may also be subject to other errors or inaccuracies based on our conversations with him since. It's very hard as a result to produce a technique which will measure just the signal processing on its own unfortunately. Many measurement techniques are also not explained and so it is important to try and get a picture from various sources if possible to make an informed judgement about a display overall.

For our tests we will continue to use the SMTT tool to measure the overall "display lag". From there we can use our oscilloscope system to measure the response time across a wide range of grey to grey (G2G) transitions as recorded in our response time tests. Since SMTT will not include the full response time within its measurements, after speaking with Thomas further about the situation we will subtract half of the average G2G response time from the total display lag. This should allow us to give a good estimation of how much of the overall lag is attributable to the signal processing element on its own.

Lag Classification

To help in this section we will also introduce a broader classification system for these results to help categorise each screen as one of the following levels:

• Class 1) Less than 10ms / 1 frame lag at 100Hz - should be fine for gamers, even at high levels

• Class 2) A lag of 10 - 20ms / One to two frames at 100Hz - moderate lag but should be fine for many gamers. Caution advised for serious gaming

• Class 3) A lag of more than 20ms / more than 2 frames at 100Hz - Some noticeable lag in daily usage, not suitable for high end gaming

For the full reviews of the models compared here and the dates they were written (and when screens were approximately released to the market), please see our full reviews index.

We have provided a comparison above against other models we have tested to give an indication between screens. The screens tested are split into two measurements which are based on our overall display lag tests (using SMTT) and half the average G2G response time, as measured by the oscilloscope. The response time is split from the overall display lag and shown on the graph as the green bar. From there, the signal processing (red bar) can be provided as a good estimation.

We measured a total display lag of only 7.10ms. With approximately 6.65ms of that accounted for by pixel response times we had an estimated signal processing of only 0.45ms - basically nothing. This was an excellent performance making the screen fully suitable for fast gaming needs from a lag point of view. Looks like Acer's "ultra low input lag technology" has done the trick here. This was a really pleasing result as often screens with FreeSync and an additional scaler can have more moderate levels of lag. The Philips 349X7FJEW and LG 38UC99 for instance have 17.25ms and 19.40ms of signal processing lag.

Movies and Video

The following summarises the screens performance in video applications:

• 31.5" screen size makes it a reasonable option for an all-in-one multimedia screen, but being quite a bit smaller than most modern LCD TV's of course even at this size.

• 16:9 aspect ratio is more well suited to videos than a 16:10 format screen, leaving smaller borders on DVD's and wide screen content at the top and bottom.

• 3840 x 2160 Ultra HD resolution can support full 1080 HD resolution content and Ultra HD content as well.

• Digital interfaces support HDCP for any encrypted and protected content

• Good range of connectivity options provided with 1x DisplayPort, 2x HDMI 2.0 and 1x USB type-C offered

• Cables provided in the box for DisplayPort, HDMI and USB type-C.

• Light AG coating providing clean and clear images, without the unwanted reflections of a glossy solution.

• Wide brightness range adjustment possible from the display, including a maximum luminance of ~322 cd/m² and a fairly decent minimum luminance of 76 cd/m². This should afford you good control for different lighting conditions. Brightness regulation is controlled without the need for PWM and so is flicker free for all brightness settings.

• Black depth and contrast ratio are excellent thanks considering this is an IPS panel, measured at 1468:1 after calibration. Detail in darker scenes should not be lost as a result.

• There is a specific preset modes for 'movie; on this model which which might be useful to set up and save your settings for specific movie viewing.

• Fairly slow but decent enough pixel responsiveness which should be able to handle fast moving scenes in movies without too much issue. There is no overshoot at all, but you may start to see some blurring in very fast content in some cases.

• Wide viewing angles thanks to IPS-type panel technology meaning several people could view the screen at once comfortable and from a whole host of different angles. When viewing darker content you may find the characteristic IPS-glow a little annoying on this panel technology.

• No backlight leakage, and none from the edges which is good. This type of leakage may prove an issue when watching movies where black borders are present but it is not a problem here.

• Good and generally fairly easy to use tilt, height and swivel ergonomic adjustments available from the stand making it pretty easy to re-position the screen for movie viewing from a distance, or with other people. They are a little stiff to operate.

• 2x 2W integrated stereo speakers on this model and an audio output connection if needed. Speakers might be ok for the odd video clip from YouTube but not for any real movie viewing.

• Decent hardware aspect ratio options with full, aspect and 1:1 modes offered. Being a native 16:9 aspect ratio screen many external devices are the same and so probably don't need scaling. The 'aspect' control will help for any unusual input ratios nicely.

• Picture in picture (PiP) and Picture By Picture (PbP) are also available.

• HDR is listed in the specs for this display but doesn't really offer any benefits due to the lack of an extended peak brightness and any kind of local dimming backlight. See the following section for more information.

 

HDR (High Dynamic Range)

 

HDR stands for High Dynamic Range and is a technology just starting to make its way in to the desktop monitor market. It's been around in the TV market for a couple of years and is used primarily to provide a better dynamic range and contrast to the image for multimedia, movies and games - that being the difference between light and dark parts of an image. This improvement to the dynamic range is usually paired with other specific features under the banner term of "HDR" including a wider colour gamut for richer, more vivid colours and specs like a 10-bit colour depth support and a high Ultra HD resolution. Overall, an HDR Capable screen is designed to offer a more life-like images, with better contrast ratios between light and dark areas and more vivid, bright colours. You only need to go in to a high street store to observe the difference that HDR makes on TV sets, so we would encourage you to do that if you want to see first hand the improvements it makes to the image quality.

 

HDR Standards Conformity

 

Ultra HD Premium Spec Guidelines	Yes/no	Display Spec
At least Ultra HD Resolution 3840 x 2160		3840 x 2160 native
10-bit colour depth processing		8-bit + FRC panel
DCI-P3 colour space coverage		96.6% DCI-P3 measured in standard mode
Suitable HDR connectivity		HDMI 2.0
at least 1000 cd/m2 peak luminance		331 peak cd/m2 measured
at least 20,000:1 active contrast ratio		1737:1 maximum measured
Backlight dimming system (not defined in Ultra HD Premium requirements)	Global (full screen) dimming only

 

The PE320QK is advertised as being an HDR capable display, but you need only look at the specs to realise that it cannot achieve some of the key requirements to deliver a true HDR experience unfortunately. On the plus side, the screen has the necessary high Ultra HD resolution, extended DCI-P3 colour space and 10-bit colour depth support. So it is capable of offering support for the high resolution of HDR content commonly mastered in Ultra HD and also give a nice boost in colour vividness. However it is not capable of achieving any real high dynamic range when it comes to improving contrast. The screen only supports global dimming as a starter, i.e. where the whole backlight has to be dimmed and brightened at once. It is not even divided up in to a small number of zones like some screens are with edge-lit local dimming (e.g. 8 zones on the Samsung C320HG70). Because of this, it's not possible to dim small areas of the screen to produce the HDR affect. Without local dimming we don't think a screen should be labelled as HDR to be honest.

 

The other area where the PE320QK misses out when it comes to HDR is in offering a higher peak luminance. There is no peak brightness spec provided and the screen is only capable of reaching its normal maximum brightness of up to 350 cd/m² maximum (according to the Acer spec). So it is not capable of boosting brightness for HDR content highlights either.

 

Because of the limited peak brightness the screen cannot be awarded any of the new VESA DisplayHDR badges unfortunately, not even the entry level DisplayHDR 400.

 

Native colour space comparison vs. DCI-P3 reference

 

Above is the screens native colour gamut in the 'standard' preset mode (black triangle), plotted against the DCI-P3 reference. In this native colour gamut there is a 96.6% DCI-P3 coverage. The screen also offers a couple of other modes which might be used for HDR content. There is a specific 'DCI' mode in the preset menu which produces a slightly different colour space. That trimmed the 131% sRGB coverage of the standard mode back to 125.6%, resulting in a slightly smaller 92.6% DCI-P3 colour space (66.4% of Rec.2020). Odd that the DCI mode seemed to offer less coverage of DCI-P3 than the standard mode.

 

There is also a specific HDR option in the OSD menu which once selected, disables some of the OSD controls. Brightness and contrast controls become locked for instance. That mode offered a colour gamut basically the same as the native full gamut of the screen, with 130.7% sRGB, 96.4% DCI-P3 and 69.1% Rec.2020 measured using ChromaPure. Users will probably want to switch to this HDR mode for HDR content which activates the limited global dimming function, but it's good to know that DCI-P3 coverage is high so you do at least get the benefit of the boosted colours for HDR content.

 

 

HDR Contrast and Peak Brightness

 

We measured the luminance and contrast performance of the screen in HDR mode in a variety of scenarios. A white box is displayed on the screen which covers 1% of the overall screen size initially. This is designed to show at several target luminance levels, starting at 100 and then changing to 400 and 1000 cd/m² (and beyond if needed). We measure the actual luminance of that white box to see how close to the target luminance the screen actually performs at each step. When the screen reaches the maximum peak luminance possible, we also measure the black depth of the screen at a point furthest away from the white area. This can then allow us to calculate the HDR active contrast ratio, the difference between the bright white area on screen, and the dark black areas elsewhere.

 

This 1% white screen coverage is designed to give a rough representation of how a small highlight area in HDR content might appear and work in normal multimedia. The box then increases to a larger size, covering 4, 9, 25, 49 and finally 100% of the screen area. This represents different sized areas of bright content in HDR multimedia. Again those progressively larger boxes are shown at the different luminance targets, and we measure the actual screen luminance achieved for each.

 

White window size	100 cd/m2 target	400 cd/m2 target	1000 cd/m2 target		Peak luminance (cd/m2)	Min black depth (cd/m2)	HDR contrast (x:1)
1%	107	300	329		329	0.2	1,645
4%	107	300	330		330	0.21	1,571
9%	107	301	330		330	0.19	1,737
25%	107	300	329		329	0.2	1,645
49%	107	301	331		331	0.2	1,655
100%	107	299	328		328	n/a	n/a

 

With the smallest 1% screen area white point as a starting point you can see that the luminance output of the screen was very close to the target at 100 for each of the white window sizes. When the screen tries to show a 400 cd/m² white box, we capture the luminance of the screen at around 300 cd/m² only. When it tries to display a 1000 cd/m² white box we capture the peak luminance here, since it is only capable of going up to around 331 cd/m² which is slightly higher than we'd measured in the 'standard' default preset mode (322 cd/m²) but certainly well short of the desired content luminance. This display is not really offering any boost in luminance in HDR mode compared with the normal maximum luminance of the backlight in SDR content and day to day use.

 

With a peak luminance of around 330 cd/m² we measured a black point on the same screen of only 0.19 cd/m². This gives rise to a contrast ratio of 1737:1 which was slightly beyond the normal static contrast ratio of around 1400:1. There is a slightly improved contrast but again nowhere near the Ultra HD Premium HDR standards where 20,000:1 is desired for an LCD display.

Conclusion

The Acer ProDesigner PE320QK offered some decent all round performance for semi professional design and colour work. There was a wide range of colour modes available including wide gamut support for those who need it, particularly oriented at delivering a DCI-P3 colour space. A reliable factory calibrated sRGB mode was also nice to see, offering good support if you want to work with more common sRGB content as well. There are a wide range of colour and calibration controls in the OSD as well to get the screen set up for your needs, although perhaps we would have liked to have seen hardware calibration supported as well on a screen like this.

The screen looked on paper like it might also be able to meet some light gaming needs as well, but we found the response times to be unfortunately quite slow. They should be ok for some moderate gaming but no FPS-style games. There is at least no lag on this model thanks to Acer's low input lag technology, and FreeSync is available to help handle the higher resolution demands on your graphics card. HDR is advertised for this model, but not really supported as there's no local dimming and no improved peak brightness which are too vital areas for a true HDR experience.

One area where this screen excelled though was in contrast ratio, offering a calibrated figure of 1468:1 which is a considerable way beyond any IPS panel we've previously tested and something we hope to see more of from future IPS screens. Image quality was excellent thanks to the Ultra HD resolution, with the IPS panel providing all the benefits we've come to expect like a stable image quality and wide viewing angles.

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