Introduction

We have with us now the latest 27" sized screen from ViewSonic in their Professional range. The VP2768 is aimed at professional applications and colour critical work, while maintaining a competitive price point. Rather than go the route of offering a wide gamut backlight, at an additional cost, ViewSonic have stuck with a standard sRGB gamut screen, but packed it with other features suitable for these uses. The VP2768 features an IPS panel for stable and reliable colour quality, factory calibration with dE <2, 14-bit 3D LUT (Look Up Table), a uniformity correction feature and even hardware calibration support. The screen also offers a 4-side borderless design, and Daisy-chaining from a single DisplayPort cable making it a suitable option for multi-screen setups. It's not been officially released yet in Europe so we have a very early look at this display to put it through its paces.

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Specifications and Features

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

The VP2768 offers a decent range of connectivity options with 1x DisplayPort 1.2, 1x Mini DisplayPort and 2x HDMI 1.4 connections offered. There is also a DisplayPort out connection for daisy-chaining multiple displays if you need. The digital interfaces are HDCP certified for encrypted content and the video cables are provided in the box for DisplayPort to Mini DP only.

The screen has an internal power supply and comes packaged with the kettle-type power cable you need. There are also 4x USB 3.0 ports located on the back of the screen with the video connections. An audio out connection is also provided if you need it.

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

 

OSD Menu

Above: OSD control buttons on the back right hand side of the screen (viewed from front). Click for larger version

The OSD menu is controlled through a series of 5 pressable buttons located on the back right hand edge of the screen. There is also a power on/off button beneath these which feels a little different to the touch. We found that the buttons were sometimes a bit fiddly to use, as it's not always intuitive to know which button you're pressing, or which ones you are hovering over at the back. This can result in wrong presses, and sometimes even an accidental power off if you stray too low.

Pressing any of the OSD buttons pops up the above quick launch menu, along with some labels on the right hand edge of the display to help guide you to the appropriate button on the back.

The menu is split in to 6 sections shown across the top and you can scroll between them to reveal the relevant options available underneath. The input and audio menus are self explanatory. The above 'ViewMode' menu gives you access to the range of preset modes for different uses.

The 'Color Adjust' section allows you to change brightness, contrast, access the factory calibrated colour modes (e.g. the sRGB mode), the hardware calibrated modes and also the custom settings where you can adjust the RGB values yourself for manual calibration.

The 'Manual Image Adjust' section has some useful options as well, including the aspect ratio control, overdrive levels (Response Time setting) and the Low Input Lag settings. We will test all of these later on in the review.

Overall there was a very good range of options available and the software was responsive. It wasn't very intuitive though and felt a bit cumbersome sometimes trying to get to the option you wanted.
 

Power Consumption

In terms of power consumption the manufacturer lists typical usage of 32W, maximum of 35W and 0.3W in standby. We carried out our normal tests to establish its power consumption ourselves.

We tested this ourselves and found that out of the box the screen used 30.3W at the default 100% brightness setting. Once calibrated the screen reached 16.7W consumption, and in standby it used only 0.6W. We have plotted these results below compared with other screens we have tested. The consumption is comparable to the other 27" sized screens we have tested as you might expect, with some of the smaller screens drawing slightly less power (comparing the calibrated states). Those with wide gamut support like the ViewSonic VP2772 and NEC PA271W draw more power because of their backlight units, despite being the same size as this screen.

Panel and Backlighting

Panel Part and Colour Depth

The ViewSonic VP2768 features an LG.Display LM270WQ5-SSA1 IPS technology panel which is capable of producing 16.7 million colours. This is achieved through an 8-bit colour depth.

Screen Coating

The screen coating is a light anti-glare (AG). Thankfully it isn't a heavily grainy coating like some old IPS-type panels and is also lighter than TN Film coatings. 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. There are no visible cross-hatching patterns evident.

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. The W-LED unit offers a standard colour gamut which is approximately equal to the sRGB colour space. Anyone wanting to work with wider colour spaces would need to consider wide gamut backlight screens or those which feature technologies such as Quantum Dot for extending the colour space. 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

At 100% brightness a constant voltage is applied to the backlight. As you reduce the brightness setting to dim the backlight a Direct Current (DC) method is used, as opposed to any form of PWM. This applies to all brightness settings from 100% down to 0%. The screen is flicker free as a result as advertised, which is great news.

 

Contrast Stability and Brightness

The brightness control gave us a good range of adjustment. At the top end the maximum luminance reached 333 cd/m² which was a little shy of the specified maximum brightness of 350 cd/m² from the manufacturer. There was a very good 288 cd/m² adjustment range in total, and so at the minimum setting you could reach down to a low luminance of 45 cd/m². This should be adequate for those wanting to work in darkened room conditions with low ambient light. A setting of 25 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, using a Direct Current (DC) method for all brightness settings between 100 and 0% and 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 good for an IPS panel at 1016:1. This was very stable across the brightness adjustment range on the most part, although there did seem to be a drop for the very low end of 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

Each VP2768 monitor is factory calibrated to deliver a Delta E < 2 and accurate gamma curve, and includes a detailed calibration report for sRGB, EBU, SMPTE-C, Rec. 709, and DICOM-SIM colour spaces. Whether you�re a photographer shooting in sRGB, or a video editor in need of REC 709/SMPT-C/EBU standards, the monitor is designed to deliver the accuracy you need to complete your best work. To access any of the factory calibrated modes you need to use the 'Standard Color' menu in the OSD to select the relevant preset option. We have provided a copy of the calibration report for our unit which comes in the box with the screen, for those interested:

By default the screen is actually set in the 'Custom' user mode which does not carry any specific factory calibration. We will test that out-of-the-box setup first of all here.

Default settings of the screen were as follows:

ViewSonic VP2768 - Default Settings (not factory calibrated)

   

Initially out of the box the screen was set with a high 100% brightness and so was overly bright and uncomfortable to use, so you will definitely need to turn that down. You could tell the screen was using a standard gamut backlight as well with the naked eye, and the colour balance and temperature felt pretty good and contrast was decent.

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) is fairly equal to the sRGB colour space. There is some minor over-coverage in most shades, with a little under-coverage in some greens but not by anything significant. Default gamma was recorded at 2.3 average, leaving it with a minor 4% deviance from the target which was pretty good. This was with the screen set in the default 2.2 gamma mode in the OSD. We also tested the other gamma modes which returned: off = 2.4 (8% out from our target), 1.8 mode = 1.9 measured, 2.0 mode = 2.1 measured, 2.4 mode = 2.5 measured, 2.6 mode = 2.7 measured. Probably best to stick with the 2.2 mode for optimal setup.

White point was measured at a slightly warm 6287k in the default setup where the colour temperature mode in the OSD was set to "native". This left the white point 3% out from the 6500k we'd ideally want for desktop use. We also tested the other preset colour temperature modes out of interest which returned the following results for a white point measurement: panel default mode = 6331k, bluish = 9162k, cool = 7430k, native = 6360k, warm = 4944k, user = 6335k. So looks like the 'user' mode returns a slightly more accurate white point by default, and will also then allow alterations to the RGB channels for the calibration process.

Luminance was recorded at a very bright 345 cd/m² which is too high for prolonged general use. The screen was set at a default 100% 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 0.34 cd/m² at this default brightness setting, giving us a good static contrast ratio for an IPS-type panel of 1012:1. Colour accuracy was good out of the box with an average dE of 1.7, although red and blue shades seem to show more deviance, up to a dE max of 5.0. Testing the screen with colour gradients showed smooth gradients with only minor gradation evident in darker tones. There was no sign of any colour banding which was good news.

We went ahead and measured the sRGB factory calibrated mode as well:

ViewSonic VP2768 - Default Settings (sRGB factory calibrated mode)

We changed to the Standard Color > sRGB mode which carries a factory calibration. In this mode first of all you are automatically changed to a fixed brightness/contrast level and those settings are no longer available to change. Everything else is preset as well, and if you try to go in to the 'custom' section of the color adjust menu it will revert you back to the custom mode, and away from the factory calibrated sRGB mode. In this sRGB mode the uniformity correction feature has been turned on, which is why the brightness setting is not available. As a result of that function being on, the luminance is crushed to a lower level through digital white level adjustments. This depends on what you set the brightness setting to first of all with uniformity off. For example, with uniformity off and brightness at 100% you get 325 cd/m², but as soon as you turn uniformity on it is crushed to around 132 cd/m². If you go back and change the brightness to something lower like 25% to achieve 120 cd/m² with uniformity off, once you turn it back on the luminance is crushed to around 55 cd/m²! If you want to use the uniformity function in this sRGB mode, we would recommend turning it off, changing the brightness setting to around 78% and then turning uniformity back on. That should result in a luminance output close to 120 cd/m². You should be aware also that with uniformity turn on the contrast ratio is crushed as a result to around 442:1. That is a fairly common occurrence for a uniformity correction feature and we will talk about that more later on in the review.

To avoid this crushed contrast ratio for these measurements, we turned uniformity correction off.

Testing this mode revealed a few interesting things. The colour gamut has been slight reduced here to more closely fit the sRGB space. It's only minor, but you can see some slight differences in coverage if you compare the CIE diagram on the left, with that measured in the default custom mode of the screen here. When you've turned uniformity correction off the gamma curve basically the same in this factory calibrated sRGB mode, with the minor 4% deviance we'd seen out of the box still there. With the uniformity correction function turned on, which is the default option for the sRGB mode by the way and presumably what was used for the factory calibration, the gamma curve is closer at 2.2 average with 1% deviance measured. So the factory calibration has achieved a more accurate gamma curve, albeit only with uniformity correction turned on.

It's a little hard to tell from the provided calibrated report what the target was for white point, but it looks like it has been calibrated to closed to 6000k than the 6500k we normally aim for. We measured it at 6239k with uniformity off, and a bit warmer at 6036k when it was turned on. Brightness was still too high once you've turned the uniformity correction off and left yourself with the 100% default brightness setting. With uniformity correction turn on you get a more comfortable level of 132 cd/m², although with the setting locked in the OSD it was not possible to customise the brightness any further.

dE was a little more accurate in this sRGB mode than the out of the box settings, with an average of 1.4 / max of 2.5. The sRGB factory calibration offered a reasonable performance although you need to decide if you want uniformity correction turned on or off. At least that option is available in this mode, and we will test its effectiveness later on in the review. With it turned off, the performance was slightly better at least than the out of the box mode, with a more accurate dE. You will need to turn down the brightness to something comfortable which is easy enough (once uniformity correction is turned off).

 

Calibration (Software Profiling)

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.

Monitor OSD Option	Default Settings
View mode preset	Off
Color mode	Custom
Brightness	25
Contrast	70
Gamma	2.2
Color Temperature	User
RGB	98, 93, 100

ViewSonic VP2768 - Calibrated Settings (Software Profiling)

   

We changed to the 'user' color temperature mode which offered us access to the RGB controls from within the menu. 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.

Average gamma was now corrected to 2.2 average a 0% deviance, correcting the 4% deviance we'd seen out of the box. The white point had now been corrected to 6470k, which corrected the 3% deviance we'd seen out of the box where the screen was a little too warm. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at 120 cd/m². This left us a black depth of 0.12 cd/m² and maintained a strong IPS static contrast ratio of 994:1. Colour accuracy of the resulting profile was excellent, with dE average of 0.4 and maximum of 1.1. LaCie would consider colour fidelity to be very good. Testing the screen with various colour gradients showed mostly smooth transitions with only some very minor banding due to the adjustments to the graphics card LUT from the profiling of the screen. 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.

 

Hardware Calibration (updated)

The ViewSonic VP2768 supports hardware level calibration, allowing you to make adjustments to the internal Look Up Table (LUT) and to store settings and calibrations within the monitor hardware itself. This is very useful for professional users to ensure consistent accuracy, without needing to rely on software profiles at an application level. Because the calibration is saved in the monitor, it is active no matter what content or application you are working with.

To hardware calibrate the VP2768 ViewSonic provide a calibration package (the CS-XRI1 kit) consisting of a colorimeter (an X-rite i1 Display Pro which they have re-branded as the "ViewSonic Colorbration" device) and the relevant calibration software. This calibration package is not provided with the monitor, you have to purchase it separately and it is currently listed on their website at a retail price of $279.99. We have the kit with us to test as well. The software is available for free from the ViewSonic website and can be used with a normal X-rite i1 Display Pro or i1 Pro / i1 Pro 2 spectrophotometer instead if you have one already, you don't have to buy the full calibration package from ViewSonic.

The ViewSonic webpage says the following about the kit: "With the ViewSonic CS-Xri1 Colorbration Kit, you can quickly and easily calibrate your monitor to maintain superior colour accuracy over time. The ViewSonic� Colorbration Kit combines innovative colour emitter hardware and sophisticated profiling software that allows you to calibrate and profile your monitor, and measure ambient light conditions, while also giving you infinite control of white point, luminance, contrast ratio, gamma, and more. This unrivalled colour accuracy and consistency saves you the time, money, guesswork, and frustration that generally comes with monitor calibration. Now you can focus on your work, and have complete confidence that the colour displayed on your monitor is the vivid, lifelike colour that you demand."

Loading up the software you are presented with the above home screen. Once a valid device is plugged in, it is verified on the right with the green ticks. You can move to the "advanced" mode if you want more options and things to change.

If you press 'display profiling' from the left, you enter in to the calibration process. You can see that the display is automatically detected. You need to have connected the screen to your PC using the provided USB cable for the hardware calibration to function by the way. You can define targets for colour space and luminance level here.

Pressing next takes you the above screen where the device is confirmed. If the software has correctly detected the screen you should see the calibration modes listed in a drop down, allowing you to select which mode you want to hardware calibrate. If not, you would see options relating to normal software profiling of the screen. There are three CAL modes available on the VP2768 giving you some flexibility to calibrate to different requirements and targets. When we first installed the software from the ViewSonic website (v1.1.0) this hardware calibration detection didn't seem to work, and we were only able to software profile the screen. After working with ViewSonic to resolve the problem we were given a new v1.2.0 software which worked fine. You can 'start measurement' from here to begin the calibration process.

The whole process is then entirely automated and the screen runs through various tests and corrections. The whole calibration process takes a long time, around 9 min 15 sec with the ViewSonic Colorbration device (an X-rite i1 Display Pro), but you can leave it alone to complete as no user interaction is needed.

 At the end you are only asked to confirm completion and are not presented with any validation options. You need to go back to the home screen, change to the 'advanced' option and the use the 'Quality' option from the left which has now appeared.

Within the 'Quality' section you can run some validation steps which are useful. The ColorChecker classic for instance will run through a series of colour patches and give you deltaE readings.

 

At the end of the validation process you are presented with a results page like above. Giving you a dE score for all the measured patches. Different patch samples and methods are available for validation if you want. Some visual graphs, as well as measurements for white point, luminance, gamma and contrast would have been useful but don't seem to be available in the softawre.

We plugged in our i1 Pro 2 spectrophotometer to validate the results using the familiar LaCie Blue Eye Pro software:

ViewSonic VP2768 - Hardware Calibration
ViewSonic Colorbration device and software

   

The above validation step confirms some very good results from the hardware calibration process. Keep in mind there is likely to be some variance in the two instruments used as the screen was calibrated using the ViewSonic i1 Display Pro colorimeter and validated here with the i1 Pro spectrophotometer. Nevertheless it confirms a solid result from the hardware calibration with only minor deviance in gamma and white point. Luminance was spot on and contrast ratio remained at similar levels to our software calibrated state at 901:1. The low dE was confirmed here as well.

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. 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 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, with a small 4% deviance in gamma and 3% in white point. The dE was 1.7 average as well and we had a strong 1012:1 contrast ratio. This was actually in a non-factory calibrated mode as well, and the performance improved a little as we switched to the factory calibrated sRGB mode. That mode also gives you access to the uniformity correction feature which is very good (see later in the review). This was a little better default set up overall than some of the other 27" IPS models listed here, including the popular Dell U2715H and Dell U2717D for instance.

The display was good when it came to static contrast ratio for an IPS panel at 994:1. Anything around 1000:1 is decent for this panel technology and it was on par with some other IPS screens shown here. Some modern IPS panels can reach up closer to 1200:1, and VA panels (not shown here) can of course reach higher up to over 3000:1.

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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.

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. The level of glow here is the same as other recent IPS panels we've seen and is pretty typical of a modern IPS-type panel. If you view dark content from a normal head-on viewing position, you can actually see this glow slightly as your eyes look towards the edges of the screen. 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 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.

The VP2768 features a uniformity correction feature which is sometimes available on professional grade screens. On this model it is available within the following colour space modes: sRGB, EBU, SMPTE-C, Rec. 709 and is accessible from the 'Manual Image Adjust' section of the OSD. Above shows the uniformity correction option at the bottom of this menu, available in certain colour modes only.

Uniformity of Luminance - Correction OFF

First of all we changed to the sRGB factory calibrated mode and tested the screen with the uniformity correction feature turned OFF. We had to manually change the brightness to achieve a centrally calibrated measurement of 120 cd/m². With uniformity correction off we saw the above results. A large portion of the screen remained within a small 5 - 10% deviance from the centrally calibrated point, but the luminance did drop down to lower levels along the left hand edge and bottom right hand area. In the worst cases it dropped by 22% to around 94 cd/m². Around 80% of the screen was within a 10% deviance though which was good.

Uniformity of Luminance - Correction ON

We adjusted the brightness setting to 78% in the OSD and then turned the uniformity correction feature ON. This locks the brightness control once it's turned on and this feature makes digital white level adjustments to the screen in order to try and improve the uniformity across the panel. In doing so, the luminance output of the screen is artificially reduced, and we found that by setting the brightness to 78% first, this turned out as ~120 cd/m² once uniformity correction was back on. We measured the luminance across the panel again with the correction function ON.

The luminance uniformity of the screen was significantly improved and there was now a maximum of 4.76% deviance between any two points on the screen. This was an excellent result and showed that the uniformity correction worked really well. You do need to contend with the loss of the brightness control once it's turned on, so make sure you find a comfortable setting by switching it off and changing brightness first of all. You may need to experiment to find the brightness setting which works for you once uniformity is back on. The main drawback of this, and other similar uniformity correction features from other manufacturers is that it does crush the contrast ratio when you use it. We measured a static contrast ratio of around 420 - 440:1 with uniformity enabled.

 

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 some clouding evident in the four corners, particularly in the bottom two corners. If you are in a very dark room working with dark content you may notice this a little, although in day to day use you would be hard pressed to see any issue.

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

This screen feature a large 2560 x 1440 WQHD resolution, a significant step up from the wide range of 1920 x 1080 screens on the market. The pixel pitch of 0.233 mm is quite small as a result, and by comparison a standard 16:10 format 24" model has a pixel pitch of 0.270mm and a 30" model has 0.250mm. These ultra-high resolution 27" models offer a tight pixel pitch and therefore small text as well. We found it quite a change originally coming from 21.5 - 24" sized screens back in the day, even those offering quite high resolutions and small pixel pitches. Although now we are very used to working with 27" 1440p screens all the time and find them very comfortable and a significant upgrade over 1080 / 1200p models. Some users may find the small text a little too small to read comfortably, and we'd advise caution if you are coming from a 19" or 22" screen for instance where the pixel pitch and text are much larger. The extra screen size takes some getting used to over a few days as there really is a lot of room to work with but once you do, it's excellent. For those wanting a high resolution for CAD, design, photo work etc, this is a really good option. The image was very sharp and crisp and text was very clear. With its WQHD display, you enjoy 77% more desktop space than a full HD screen to spread out your windows and palettes.

The ultra thin bezel/border design around all 4 edges mean that the screen could be easily integrated into a multi-screen set up if you wanted. The light AG coating of the IPS technology panel is certainly welcome, and much better than the older grainy and 'dirty' appearance of older IPS AG coatings. 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 good, especially once you switched to the factory calibrated sRGB preset, offering a decent gamma curve, accurate white point, strong contrast ratio and low dE. The added uniformity correction does an excellent job of improving the luminance stability across the screen, although you do need to contend with a crushed contrast ratio if you use it.

The brightness range of the screen was excellent, with the ability to offer a luminance between 333 and 45 cd/m² (uniformity correction off). This should mean the screen is useable in a wide variety of ambient light conditions, including darkened rooms. A setting of ~25 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 Pulse-Width Modulation (PWM), and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry.

There are a couple of extras provided here as well including a 4 port USB 3.0 hub with all ports on the underside of the screen. It might have been nice to have a couple of these on the side of the screen for easy access. There is also an audio output for speaker connection. There were no further extras such as ambient light sensors or card readers on this model which can be useful in office environments. There was a good range of ergonomic adjustments available from the stand allowing you to obtain a comfortable position for a wide variety of angles. The VESA mounting support may also be useful to some people as well.

Above: photo of text at 2560 x 1440 (top) and 1920 x 1080 (bottom)

The screen is designed to run at its native resolution of 2560 x 1440 and at a 60Hz recommended refresh rate. However, if you want you are able to run the screen outside of this resolution. We tested the screen at a lower 1920 x 1080 resolution to see how the screen handles the interpolation of the resolution, while maintaining the same aspect ratio of 16:9. At native resolution the text was sharp and clear. When running at a the lower  resolution the text is still reasonably clear, with fairly low levels of blurring. You do lose a lot of screen real-estate as well of course.

 

 
Responsiveness and Gaming

The VP2768 is rated by ViewSonic as having a 14ms G2G response time. This is a little odd as that would imply that the screen maybe does not use overdrive / response time compensation (RTC) technology to boost pixel transitions across grey to grey changes, as a figure of 14ms is not very aggressive in today's market. However, we know that the OSD menu offers various options for Response Time control, so overdrive must be used on this model. We will test the actual response times in a moment, but we suspect ViewSonic could have been more aggressive with their response time spec here if they wanted to. Given this is not really aimed at gaming, and is a professional range screen, we suppose it's perhaps not something they were concerned with. The part being used is the LG.Display LM270WQ5-SSA1 IPS technology panel. Have a read about response time in our specs section if you need additional information about this measurement.

We will first test the screen using our thorough response time testing method. This uses an oscilloscope and photosensor to measure the pixel response times across a series of different transitions, in the full range from 0 (black) to 255 (white). This will give us a realistic view of how the monitor performs in real life, as opposed to being reliant only on a manufacturers spec. We can work out the response times for changing between many different shades, calculate the maximum, minimum and average grey to grey (G2G) response times, and provide an evaluation of any overshoot present on the monitor.

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.
 

Response Time Setting

The 'Response Time' setting is available via the 'Manual Image Adjust' section of the OSD menu as shown above. We will test the modes to see which is optimal first of all.

In the 'standard' Response Time setting we recorded an average figure of 13.6ms G2G, basically meeting the advertised spec for the screen of 14ms G2G. Transitions from dark to light shades (rise times) were particularly slow up to around 20ms. In this setting there was no overshoot at all but the slow response times lead to noticeable blurring of moving images.

If you switch up to the 'Advanced' setting the results are better and you can see an obvious improvement in motion clarity with the naked eye. Average G2G response time had now been dropped down to 8.6ms G2G which is a much better performance and showed improvements in the levels of blurring in practice. A small amount of overshoot started to creep in but you shouldn't notice this in practice. The highest 'Ultra Fast' mode was too aggressive with the overdrive impulse, driving response times down a bit to 7.1ms G2G, but at the cost of some high levels of overshoot which became apparent in practice. To be fair the dark halos were not majorly obvious, but you can still see them (see our PixPerAn images below for example). Stick with the 'Advanced' setting for optimal response time behaviour on this screen which is on par with the better 60Hz IPS panels around.

The above images give you an indication of the blurring and overshoot levels in each of the Response Time overdrive modes, using the PixPerAn test tool. Responsiveness improves as you change from standard > advanced mode with less blurring and a sharper, clearer moving image. The Ultra Fast mode starts to introduce some dark halos behind the moving object and the overdrive impulse is probably a bit too aggressive in that mode.

Display Comparisons

The above comparison table and graph shows you the lowest, average and highest G2G response time measurement for each screen we have tested with our oscilloscope system. There is also a colour coded mark next to each screen in the table to indicate the RTC overshoot error, as the response time figure alone doesn't tell the whole story.

As a reminder, these measurements were in the optimal 'Advanced' Response Time overdrive mode. With an average of 8.6ms G2G and low levels of overshoot the VP2768 performed well for an IPS panel, and in line with some of the better 60Hz IPS models we have tested to date. Response times of around this 8.6ms seem to be about the best manufacturers can achieve with a native 60Hz refresh rate, from this panel technology, and so it was pleasing that the VP2768 had performed well here. The high refresh rate IPS models like the Asus ROG Swift PG279Q (5.0ms G2G) and MG279Q (6.5ms G2G) for instance had performed better, and TN Film models like the Asus ROG Swift PG278Q (2.9ms G2G) could of course reach faster speeds and are specifically designed for gaming audiences. Considering the VP2768 is not aimed at gamers really, it performed admirably for a 60Hz IPS panel and should be able to handle general gaming fine.

Additional Gaming Features

Aspect Ratio Control - the screen offers 3 options for aspect ratio control, available through the OSD menu in the 'manual image adjust' section as shown. There are options for 1:1 pixel mapping, 4:3 mode and 'full screen'. This should suit most people's needs, especially since most graphics cards can handle scaling for you as well when connected to a PC. It might have been good to also include an 'aspect' option, to maintain the input aspect ratio but scale it to fill as much of the screen as possible, instead of just 1:1 pixel mapping it.

Preset Modes - There are 4 gaming preset modes available in the 'ViewMode' menu. There are options for FPS1, FPS2, RTC and MOBA and each can be customised to your liking and saved which is handy.

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 16ms / 1 frame lag at 60Hz - should be fine for gamers, even at high levels

• Class 2) A lag of 16 - 32ms / One to two frames at 60Hz - moderate lag but should be fine for many gamers. Caution advised for serious gaming

• Class 3) A lag of more than 32ms / more than 2 frames at 60Hz - 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.

The screen has three modes for 'low input lag' in the OSD menu as shown above. We tested the lag in each setting. The 'off' and 'advanced' modes seemed to be identical, showing a total display lag of 24.50ms. With a 4.3ms G2G response time element considered, the signal processing lag in those two models was around 20.2ms. When you switch up to the 'UltraFast' input lag mode you get some improvements thankfully. Total display lag dropped to 13.20ms, giving us a signal processing estimate of ~8.9ms. This was just over half a frame at 60Hz and represented a decent lag. Especially considering this is not a gaming screen per se.

Movies and Video

The following summarises the screens performance in video applications:

• 27" screen size makes it a reasonable option for an all-in-one multimedia screen, much smaller than LCD TV's and many larger format desktop monitors which are now emerging.

• 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.

• 2560 x 1440 resolution can support full 1080 HD resolution content.

• Digital interfaces support HDCP for any encrypted and protected content

• Good range of connectivity options provided with DisplayPort, Mini DisplayPort and 2x HDMI offered.

• Cables provided in the box for DisplayPort to Mini DP only.

• 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 ~333 cd/m² and a decent minimum luminance of 45 cd/m². This should afford you good control for different lighting conditions. Contrast ratio remains stable across that adjustment range as well and is good for an IPS-type panel. Brightness regulation is controlled without the need for PWM and so is flicker free for all brightness settings.

• Black depth and contrast ratio are good for an IPS-type panel at 994:1 after calibration. Detail in darker scenes should not be lost as a result.

• There is a specific 'movie' preset mode available for movies or video if you want but it is cooler than our calibrated custom mode. May be useful to some though.

• Good pixel responsiveness which should still be able to handle fast moving scenes in movies without issue. Stick with the 'advanced' response time setting for optimal performance.

• 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.

• IPS glow is at a normal level meaning you might experience some annoying white glows on darker content from an angle.

• Very good and easy to use range of ergonomic adjustments available from the stand, so should be easy to obtain a comfortable position for multiple users or if you want to sit further away from the screen for movie viewing.

• No particularly major 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.

• No integrated stereo speakers on this model but there is an audio put connection if you want.

• Decent range of hardware aspect ratio options with 1:1 pixel mapping, full screen and 4:3 modes available which should be fine for most uses.

• Picture in picture (PiP) and Picture By Picture (PbP) are not available.
   

Conclusion

The VP2768 was overall a very good display. While it is aimed at professional users specifically we felt that it fit a more all-round user market as well.For professional users ViewSonic have opted to leave off some common high end features like wide gamut and 10-bit colour depth support in favour of keeping the retail costs down, and instead focused on producing a quality screen for standard sRGB colour space uses. Wide gamut and 10-bit are still fairly niche and not everyone will want to pay the extra for those features when they are just looking for a quality, accurate screen for their more standard applications. The VP2768 does a nice job providing in that area with a reliable factory calibration, wide range of preset modes and options and support for hardware calibration. The uniformity correction feature is also reserved for professional screens, and on the VP2768 it works really well which was great news. For the intended audience, the VP2768 performs very well.

We were actually also quite impressed with the performance in other areas which is why we felt it helped make the VP2768 a very good all-round choice. Clearly ViewSonic are not aiming this screen at gamers, even advertising a high 14ms G2G response time in their spec. In fact we were impressed by the unexpectedly good performance for gaming, with response times matching the better 60Hz IPS models around and input lag also being pretty low. Of course the screen lacks additional gaming enhancements like a high refresh rate or motion blur reduction backlight, but it's still decent enough for general gaming and multimedia.

The appearance of the screen was very nice and we like the 4-side thin border design. The stand offers a good range of adjustments and there's plenty of connectivity options. The OSD menu was a bit fiddly to use and the control buttons didn't feel very intuitive, but there was at least a wide range of options to play with. All in all it was a very good all round performer, with some advanced features for professional audiences which help to separate it from the competition.

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