Introduction

I'll repeat some of what I have said in our recent HP ZR2240w review here as an introduction, since it is a good background. It's been about 18 months since we saw some interesting new models from HP. They have of course been producing monitors and computers for many years, but it was back in September 2008 when they sparked our interest with the launch of their HP LP2475W monitor. This was an interesting model featuring an IPS panel and some pretty high end specs which at the time were quite unique in the 24" sector. There were hardly any IPS panels at this size available and the LP2475W became the first of a new wave of screens offering this technology to the masses. Around the same time HP released a 22" equivalent, again breaking from the market norm of TN Film panels, and offering a model based on S-PVA technology. Their LP2275W also became a bit of a trend setter and other manufacturers soon followed with IPS, MVA and PVA offerings in this kind of size range. In April 2010 they released their ZR range of monitors as well, including a new 24" offering and a new 21.5" model as well as the 30" ZR30W. The ZR24W was another IPS addition to the 24" market and was a very popular choice since it was again breaking market trends. It was not following the pattern of high gamut colour spaces which was becoming popular with manufacturers at the time, instead being a rare standard gamut IPS offering in the 24" space.

Now HP have released a collection of 4 new models in their ZR range of screens, again bound to attract a lot of attention. There will be models available in sizes of 20, 21.5, 24 and 27 inches. We have already tested and reviewed the 21.5" model which was their ZR2240w. Now we have the interesting 27" model with us which is the ZR2740w. This is a new screen size in their range, competing against offerings from the like of Dell, Hazro and NEC. HP have stuck with IPS panel technology throughout the range and also combined this with the currently popular W-LED backlighting. (Note: The 24" ZR2440w monitor will be reviewed in the near future as well but availability is running a little behind the 21.5 and 27" models).

The ZR2740w is marketed as follows on HP's website: "The HP ZR2740w 68,6 (27'') LED Backlit IPS Monitor delivers massive 2560 x 1440 resolution, a 16:9 aspect ratio, and 3.7 million pixels in an ultra-modern and sleek design that perfectly complements HP Z Workstations."
 

Specifications and Features

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

The ZR2740w offers a limited range of connections which is presumably a cost cutting exercise. There are 1x Dual-link DVI-D and 1x DisplayPort available. There are no D-sub or HDMI interfaces available although these may have been left off since they are unable to support the full native resolution of the display. However, it would still have been useful to include them I think for connecting external devices where the image could then be interpolated. The digital connections are HDCP certified for encrypted content. The screen is packaged with the cables for DL-DVI and DisplayPort at least.

HP have included a 4 port USB 2.0 hub which is useful, and something which has been available on the previous models as well. There are no further features here such as ambient light sensors, integrated speakers, card readers etc. I will also note at this stage that this model does not offer a dynamic contrast ratio feature although personally I don't really miss it.

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

OSD Menu

Above: view of OSD operational buttons

It should be noted here that the ZR2740w does not offer any OSD menu at all. There are only buttons on the front for source (switching between DVI and DisplayPort connection) and plus (+) and minus (-). These two control the level of the backlight, but no indication is given on the screen as to the setting you are obtaining or what you are currently running at. As a result it is very difficult to tell what brightness setting you are using. You are able to restore to the default brightness by pressing the plus (+) and minus (-) buttons simultaneously at least. These buttons do allow you to control the brightness of the screen though in a very wide range. When you reach the top or bottom end of the range, the power LED button flashes blue for each additional press to indicate you are already at the maximum/minimum level. We counted through the number of "steps" available from this adjustment and there appeared to be 256 available. Obviously you can hold down the buttons to change this brightness a lot faster as each step is quite a subtle change.

The lack of an OSD menu is a bit of a shame really and has presumably been done to help cut costs. Without it, there are no preset modes for different uses, no colour temperature presets like we saw on the ZR2240w model recently, and no control over the contrast setting or RGB channels. During a calibration the only hardware changes you are going to be able to make are to the brightness. We had been quite impressed by the wealth of options when testing the ZR2240w recently but we don't have anything like dynamic contrast ratio, overdrive control, aspect ratio control etc here. A shame it was all left off I think.

 

Power Consumption

In terms of power consumption the manufacturers spec states typical usage of 95W and 120W maximum. In standby the screen apparently uses <2W.

We tested this ourselves and found that out of the box the screen used 86.6W of power while at its default brightness setting. At the maximum brightness level (step 256) the screen used a whopping 95.0W of power, and at the lowest setting this was measured at 27.1W. Once calibrated we had reached a power consumption of 40.7W which had been once the screen had been set to achieve a luminance of 120 cd/m². During standby the screen uses only 0.6W of power. I have plotted the results of these measurements on the graph below:

Panel and Backlighting

The HP ZR2740w utilises an LG.Display LM270WQ1-SDDA H-IPS panel which is capable on paper of producing 1.07 billion colours according to HP's specs. We have been unable to verify the panel spec sheet for this particular module, and it is not one which has been used anywhere else before. In fact it's very likely that this is a module designed and produced for HP exclusively, and their other new ZR models seem to also feature new unique panels (at least at this point in time). We have seen previous incarnations of the LM270WQ1 panel before. Both the SLA1 and SDA2 versions however feature a glossy panel coating and have been used in models such as the Apple 27" Cinema Display and Hazro's HZ27WC, HZ27WA and HZ27WD. This new SDDA module features a matt AG coating however and is clearly quite different to the other previous revisions.

Given that the SLA1 version offered a 1.07 billion colour palette as well, it's logical to think that this SDDA panel is of the same type. This would mean that the panels colour palette comes from an 8-bit native panel, with an additional AFRC control stage added. This simulates a "10-bit" panel and colour depth but it is not a true 10-bit panel. Given the relatively low cost (compared with high end professional displays with 10-bit support) of this model as well, it is reasonable to make this assumption since true 10-bit panels are rare and generally very expensive.

Having said all that, it's all very well saying a panel is capable of 10-bit colour depth (1.07 billion colour palette) as opposed to an 8-bit colour depth (16.7 million colours), but you need to take into account whether this is practically useable and whether you're ever going to truly use that colour depth. You must have a full 10-bit workflow end to end to be even able to take advantage of this "10-bit" support. There are requirements from your application, operating system, graphics card and software to consider as well and a true 10-bit workflow is actually very rare.

Regardless of whether you have a true 10-bit colour depth being displayed, a screen with 10-bit capabilities still has its potential advantages. The monitor should still be capable of scaling the colours well, even from 24-bit sources. A lot of these "10-bit" panels will also be coupled with extended internal processing which will help improve accuracy and these are better translated onto a 10-bit panel than they would be onto an 8-bit panel, giving less deviation and less chance of banding issues. The ZR2740w doesn't offer this however, so really there is very little benefit in having an 8-bit + AFRC panel present unless you are working with an end to end 10-bit workflow.

The ZR2740w uses White-LED (W-LED) backlighting. The colour space of this screen is approximately equal to the sRGB reference and is considered a 'standard gamut' backlight type. The screen covers 77% of the NTSC reference, 77.2% of the Adobe RGB reference and 99.9% of the sRGB space. A wide gamut screen would need to be considered by those wanting to work outside of the sRGB colour space of course.
 

PWM Flicker Tests (Updated 28 June 2012)

At the time of the original review we were not testing screens for their use of Pulse Width Modulation (PWM) unfortunately. However, I did want to mention the fact that according to tests carried out by Prad.de, they have identified that the ZR2740w does NOT use PWM to control backlight dimming. This is a very rare thing in the modern LCD market, and is worth mentioning. People need not be worried about backlight flicker on this model caused by PWM, even when using it at low brightness settings. See our PWM article for more information.

 

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.

I restored my graphics card to default settings and disabled any previously active ICC profiles and gamma corrections. The screen was tested at default factory settings using the DVI interface, and analysed using an X-rite i1 Pro spectrophotometer combined with LaCie's Blue Eye Pro software suite. An NEC branded and customised X-rite i1 Display 2 colorimeter was also used to verify the black point and contrast ratio since the i1 Pro 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.

Colour Accuracy, Black Depth and Contrast

Default settings of the screen were as follows:

HP ZR2740w - Default Factory Settings

 

 

You will notice that the default settings of the screen pretty much all show "n/a" above. As already discussed that is because there is no OSD menu available on the ZR2740w and so the only setting you can change is the brightness control. This was left at the default setting for this initial measurement.

 

The out of the box performance of the ZR2740w was reasonable in most areas. The CIE diagram on the left confirms that the monitors colour gamut (black triangle) closely matches the sRGB colour space (orange triangle). It extends a little past the sRGB space in greens and blues in this 2D view of gamut but is a little short in reds.

 

 

Default gamma was recorded at 2.1 average, leaving it 3% out from the target of 2.2. Gamma was actually closer to the target 2.2 in the darkest greys where it was recorded at 2.21. This deviated as low as 1.94 however in other lighter shades showing a discrepancy in the gamma curve. White point was a little out here at 6188k which was 5% out from the target. Note that we are using a Spectrophotometer to make these measurements which is not sensitive to the W-LED backlight as some colorimeter devices can be. When using a standard gamut colorimeter with a W-LED backlit screen there can be a typical deviance of 300 - 600k in the white point measurement which is why some sources may refer to a different white point in this test incorrectly.

 

Luminance was recorded at an incredibly high 456 cd/m² which is way too high for comfortable use. At this high 456 cd/m² luminance, the black depth was 0.46 cd/m². This gave us a static contrast ratio of 986:1 which is very good for an IPS panel and a pleasing result. However, given the variance in other areas like gamma, this will likely change once we have calibrated the screen to correct the other areas.

 

Colour accuracy was fairly good at default factory settings with an average DeltaE (dE) of 2.4, ranging up to a maximum of 4.4. The screen felt fairly even at least to the naked eye, although as with most screens out of the box it was overly bright. Some minor adjustments to the brightness control can hopefully help improve the default set up for casual users who don't have access to a hardware calibration device. To be fair though this kind of out of the box set up should be fine for most casual users anyway, and they can just adjust the brightness control to suit their working environment.

 

 

Calibration Results

 

I wanted to calibrate and profile the screen to determine what was possible with optimum settings and profiling. I used the X-rite i1 Pro spectrophotometer combined with the LaCie Blue Eye Pro software package to achieve these results and reports. An NEC branded and customised X-rite i1 Display 2 was used to validate the black depth and contrast ratios due to lower end limitations of the i1 Pro device.

HP ZR2740w - Calibrated Settings

Monitor OSD Option	Adjusted Setting
Brightness	Step 65
Contrast	n/a
Preset Mode	n/a
RGB Controls	n/a

	Calibrated Settings
luminance (cd/m2)	120
Black Point (cd/m2)	0.16
Contrast Ratio	751:1

 

Adjustments were made during the process to the brightness control only since there were no other hardware changes possible. For clarification we followed the guidelines of the software and ended up with a brightness setting which was 65 steps up from the minimum setting. After this I let the software carry out the LUT adjustments at a graphics card level and create an ICC profile. The screen does not feature a hardware LUT calibration option so other than the brightness alteration the rest of the process is carried out at a graphics card level in profiling the screen.

 

 

The calibration was a success. The gamma discrepancy that we saw before (3%) had been almost corrected now to leave us with 0% deviance and an average gamma of 2.2. There was still some slight discrepancy with the gamma curve with the darkest and lightest greys but it was much smaller than before. White point was also corrected to 6524k, bringing it <0.5% out from the target. Luminance had been reduced to a more comfortable 120 cd/m² thankfully after the adjustment of the OSD brightness control. Black depth was still fairly good at 0.16 cd/m² and this gave us a calibrated static contrast ratio of 751:1. This was a fair bit less than default settings (986:1) but corrections had been made to the gamma curve and greyscale which impact contrast ratio here. Colour accuracy was also improved nicely with dE average now only 0.3 and maximum only 1.4. LaCie would consider colour fidelity to be excellent overall.

 

Testing the screen with various colour gradients showed fairly smooth transitions with no obvious banding visible. There was some gradation noticeable particularly in the 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

 

 

I've provided a comparison above of the ZR2740w against some of the other screens we have tested in a similar size range. Out of the box average dE was 2.2 which was very good really. The default colour accuracy of the ZR2740w was the same on average as we'd seen from the 21.5" ZR2240w (2.2). This was also comparable to some of the W-LED + 23" IPS models we have tested including the Dell U2312HM (2.2), NEC EA232WMi (2.4) and Asus ML239H (2.3). It was also quite comparable to the default colour accuracy of the 24" HP ZR24W (2.5) which was a standard gamut CCFL unit.

 

Compared to some of the other 27" models we have tested, the ZR2740w (2.2) was more accurate out of the box than the wide gamut Dell U2711 (3.7) and Hazro HZ27WB (5.1). The Hazro HZ27WC has a similar W-LED + IPS panel to the ZR2740w and offered a good factory calibration and a default dE average of only 1.5. We will ignore the result of the HZ27WA here since that model was not factory calibrated and was a pre-release sample. The TN Film based ViewSonic VX2739wm was also a little behind the HP with an average dE of 3.4. The professional grade 27" NEC PA271W and SpectraView Reference 271 were better still at 1.1 dE and 1.5 dE average respectively. A reasonable performance in terms of default colour accuracy from the ZR2740w and only a little behind some of the competition really. Some form of software profiling using a colorimeter would of course be beneficial to correct some of the colours especially since you can't make any corrections to the hardware without an OSD.
 

 

 

Once calibrated the dE average was reduced to 0.3. This would be classified as excellent colour fidelity by LaCie. It was not quite as low as some of the other screens here which reached down to 0.2 average, but in practice you would not notice any difference here. Some of the professional range models from NEC are even more accurate. Professional grade monitors like the NEC PA series and P241W also offer other high end features which separate them from some of these other models, including extended internal processing, 3D LUT's and hardware calibration. These comparisons are based on a small selection of tests, so it should be remembered that other factors do come into play when you start talking about professional use. For further information and tests of a high end professional grade screen with hardware LUT calibration, you may want to have a read of our NEC SpectraView Reference 271 review.

 

 

 

The calibrated black depth and contrast ratio of the ZR2740w were reasonable for an IPS panel. Calibrated black depth was 0.16 cd/m² which left us with a static contrast ratio of 751:1. This was pretty much on par with the Hazro HZ27WA/C which is the closest in terms of the panel and technology being used. They offered a calibrated contrast ratio of ~745:1. For an IPS panel, this result was reasonable but not brilliant. We had seen better things from the smaller 21.5" ZR2240w model which had reached a record calibrated contrast ratio of 1005:1 in our tests.

 

The BenQ EW2420 and Samsung F2380 with their AMVA and cPVA panels respectively offered some fantastic contrast ratios of ~3000:1 which IPS cannot compete with at the moment.

 

 

 

Contrast Stability

 

The luminance range of the screen was very wide with an overall adjustment range of 472.8 cd/m² which was massive. As already mentioned there is no OSD menu, but the brightness control buttons do give you a range of 256 steps it seems. At the top end, the maximum brightness control returned us a luminance of 501.6 cd/m² which was even higher by a considerable amount than the maximum specified figure for the screen of 380 cd/m². The OSD menu brightness control allowed you to adjust this all the way down to 28.8 cd/m² which was again a fair bit lower than the specified minimum 50 cd/m². This range was excellent and should allow almost any user to obtain a comfortable setting, even when working in darkened environments and low lighting conditions. A setting of around 65 - 80 steps up from the minimum should return you a luminance of ~ 120 cd/m² at default settings. I've taken other measurements at points in between based on the number of "steps" up from minimum. I've not done a lot as it's hard to tell which setting you are using, but this should at least give you an idea of the stability of the contrast ratio across the adjustment range.

Black point ranged from 0.52 to 0.03 cd/m² which was again very good for an IPS panel out of the box.

We have plotted the luminance trend on the graph above. The screen behaves as it should, with a reduction in the backlight intensity controlled by the reduction in the OSD brightness setting.

Static contrast ratio remained high and stable across the range, with an average figure of 973:1 which was very good. These contrast measurements were plotted on the graph shown above.

 

Viewing Angles

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

Viewing angles of the HP ZR2740w are very good, as you would expect from a screen based on an IPS panel. Horizontally there are very wide fields of view with a small contrast shift only really becoming noticeable from a fairly wide angle of about 45�. At more extreme angles the image goes a little darker and a slight pale tint is introduced. Vertically, the contrast shift was a little more pronounced but the fields of view were still good. The panel is free from any off-centre contrast shift which you see from VA matrices, and this is why IPS technology is so highly regarded in the colour enthusiast and professional space. It is also free of the very noticeable contrast and colour tone shifts you see from TN Film panels vertically.

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

On a black image there is a characteristics IPS white glow, but in normal working conditions this shouldn't present much problem. The above image was taken in a darkened room to demonstrate the white wide angle glow when viewing a black screen. There is no A-TW polarizer on this panel which is rarely used now in the market but was implemented on some older screens to improve the off centre black viewing.

If you are viewing dark content from a close position to the screen you can sometimes see this pale glow on parts of the screen towards the sides and corners because of your proximity to the screen and your line of sight. The edges of the screen are at an angle from your line of sight which means you pick up this white glow to a smaller degree. This disappears as you move backwards away from the screen where the line of sight does not result in a wide angle view of parts of the screen and you can see the screen largely from head on. With such a large screen size this could have potentially caused a big problem but thankfully the glow is actually quite low I thought and it did seem better than the ZR2240w model in fact.

Panel Uniformity

Measurements of the screens luminance were taken at 35 points across the panel on a pure white background. The measurements were taken using BasICColor's calibration software package, combined with the NEC customised X-rite i1 Display 2 colorimeter. The above uniformity diagram shows the difference, as a percentage, between the luminance recorded at each point on the screen, as compared with the reference point of a calibrated 120 cd/m². This is the desired level of luminance for an LCD screen in normal lighting conditions, and  the below shows the variance in the luminance across the screen compared with this 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

The luminance uniformity of the ZR2740w was moderate. Around 65% of the screen showed very little deviation from the central point and was within 10% variation of the 120 cd/m². The bottom half of the screen was closer to this figure and showed a more stable luminance uniformity. There was a section in the top right and top left hand corners where luminance uniformity was not as good, and luminance dropped down to around 103 cd/m² (-16% deviance). This was not a several drop off though and overall 97% of the screen was within 15% deviance. Overall a reasonably good performance in this test.

Backlight Leakage

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

As usual we also tested the screen with an all black image and in a darkened room. A camera was used to capture the result. There was very little leakage from the backlight unit here which was pleasing. There was some slight variance from the four corners, with the most noticeable leakage coming from the top right hand corner. This was not too severe at all and not something you'd notice in practice and was very minimal. This was a very similar pattern to what we had seen from the ZR2240w in fact. A good result again from this display.

 

General and Office Applications

The HP ZR2740w features a massive 2560 x 1440 WQHD resolution which is only just a little bit less vertically than a 30" screen. The pixel pitch of 0.233mm is very 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 the tightest pixel pitch and therefore the smallest text as well. I found it quite a change coming from 21.5 - 24" sized screens, even those offering quite high resolutions and small pixel pitches.  Some users may find the small text a little too small to read comfortably, and I'd advise caution if you are coming from a 19" or 22" screen for instance where the pixel pitch and text are much larger. I found a 30" screen to be quite a change with text size when I first used one, and this is very similar and even a little bit smaller! I still personally prefer the slightly larger text of a 24" model myself, but I expect I could happily get used to the added resolution on these models given time. The extra screen size also takes some getting used to over a few days as there really is a lot of room to work with.

The massive resolution is really good for office and general use, giving you a really big screen area to work with. It is a noticeable upgrade from a 24" 1920 x 1200 resolution, and it's good to see HP have opted for the high res panel here rather than sticking with another 1920 x 1200 / 1920 x 1080 res panel as you may find in other older 27" models. 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.

There were no preset modes available from either screen as there was no OSD menu available. HP have cut a few corners here to keep costs down presumably, and so there are basically no setting you can change. Since there are no presets or different modes, you will have to change the backlight control each time if you want to have a different setting for movies or games than you do for day to day use. Out of the box the luminance was far too high and so you will want to turn this down significantly to obtain a setting comfortable to you in your lighting conditions. A setting of around 65 - 80 steps (in the absence of an on screen display!) should give you a luminance of around 120 cd/m².

The screen offers a 4 port USB 2.0 hub which is useful, especially with 2 ports located on the left hand edge for easy and quick access. There are no other extra features available such as ambient light sensors, card readers or integrated speakers. There was a good range of ergonomic adjustments available which were all pretty easy and smooth to use. The screen even offers a rotation function which is probably impractical at this size.

 
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. You will need a Dual-link DVI output or DisplayPort from your graphics card in order to handle that resolution. 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. At native resolution the text was very sharp as you can see from the top photograph. When you switch to a lower resolution the text is a lot more blurry. There was a high amount of overlap of the pixels but text was still readable if you had to. I would recommend native resolution wherever possible for maximum performance and picture quality.

 

Responsiveness and Gaming

The ZR2740w is rated by HP as having a 12ms G2G response time which implies the use of overdrive / response time compensation (RTC) technology, used to boost pixel transitions across grey to grey changes. Unlike the ZR2240w model there was no 'Video Overdrive' mode available since that was a feature in the OSD menu of the smaller screen, which is lacking here. As such you don't have any control over the overdrive impulse applied to the panel, it is always in the same state. The panel being used is the LG.Display LM270WQ1-SDDA. Have a read about response time in our specs section if any of this is new to you.

The screen was tested again using the chase test in PixPerAn for the display comparisons. As a reminder, a series of pictures are taken on the highest shutter speed and compared, with the best case example shown on the left, and worst case example on the right. This should only be used as a rough guide to comparative responsiveness but is handy for a direct comparison of the impact of this setting:

27" 12ms G2G LG.Display H-IPS (W-LED)

27" 6ms G2G LG.Display H-IPS (WG-CCFL)

27" 6ms G2G LG.Display H-IPS (W-LED)

27" 6ms G2G LG.Display H-IPS (W-LED)

27" 6ms G2G LG.Display H-IPS (WG-CCFL)

I have provided a comparison of the ZR2740w first of all above against 4 other 27" screens we have tested which all use IPS panel technology. Some also use W-LED backlighting as featured on the HP model. The ZR2740w showed a reasonable result in this test. There was some motion blur evident but nothing too severe. There was no obvious ghosting and no artefacts caused by the RTC impulse which was pleasing.

As you can see, the responsiveness varies between all these models shown above. The Dell U2711 has less noticeable motion blur and a faster response time. However due to an overly aggressive RTC impulse there is a noticeable dark overshoot behind the moving car which is a shame. The Hazro HZ27WA and C both feature a very similar panel (different version of the LM270WQ1) to the ZR2740w but did show a better performance in these response time tests. There was less motion blur on both although the WC model was quite close to the HP. Again the WA model had introduced a small dark overshoot as a consequence of reducing the motion blur a little more. The Hazro HZ27WB showed a more noticeable motion blur despite its quoted 6ms G2G response time. This goes to show you can't always rely on quoted specs to tell you how a screen will perform in practice.

27" 12ms G2G LG.Display H-IPS (W-LED)

21.5" 8ms G2G LG.Display e-IPS (W-LED) - Video OverDrive = On

24" 5ms G2G LG.Display e-IPS (Overdrive Off - see review for why)

24" 6ms G2G LG.Display H-IPS

Above is a comparison of the ZR2740w against 3 other HP models we have tested, two 24" IPS models and the 21.5" IPS ZR2240w model we reviewed recently. The ZR2740w has a slightly more obvious motion blur in these test than the other 3 models and is perhaps an occasion where the quoted specs of 12ms vs. 5 - 6ms are a good indication of end-user performance. The ZR2240w and ZR24W were a little faster in practice.

27" 12ms G2G LG.Display H-IPS (W-LED)

27" 1ms G2G CMO TN Film (Response time mode = Advanced)

23.6" 2ms G2G CMO TN Film (120Hz)

22" 3ms G2G Samsung TN Film + 120Hz

I've also included a comparison above against 3 gamer-orientated screens, including the 27" TN Film based ViewSonic VX2739wm. This is a competing screen at the same size, but with different panel technology it is significantly different in performance in a lot of areas. That model is aimed primarily at gamers and even has a 1ms G2G quoted response time. It performs better than the ZR2740w as you might expect in these tests as a result. Keep in mind the ZR2740w isn't really designed as a gamers screen though.

The other two models here both featuring heavily overdriven TN Film panels, and are combined with 120Hz technology. The pixel responsiveness of both of these is ahead of the ZR2740w, and the 120Hz frequency allows for improved 120fps frame rates and the support of 3D content as well. The BenQ XL2410T does show some even more obvious RTC overshoot in the form of very dark trails behind the moving image (speech bubble and head) which is unfortunate, and a sign that the RTC impulse is too aggressive. The Samsung 2233RZ remains our champion in this test.

The responsiveness of the ZR2740w should be fine for most gaming, even at quite high levels. For an IPS panel it is a good performer and although it was a little slower than some of the other models tested (and some of the smaller IPS screens) it was pretty decent. The presence of an overdrive impulse had helped offer some pretty low levels of motion blur and it was good to see that this hadn't introduced any adverse affects such as overshoot.

Additional Gaming Features

Aspect Ratio Control - The ZR2740w does not offer any form of aspect ratio control options since there is no OSD menu available. All inputs will be interpolated to fill the screen unless you have a way to control the aspect ratio via the graphics card or specific input device. For gaming it would have been good to feature hardware level aspect ratio control certainly and it is missed.

Preset Modes - There are no specific preset modes available at all from this model and so you will have to either use your normal setup mode or change the brightness each time if you want a different luminance for gaming than day to day use.

 

Input Lag

We've had some reader enquiries recently about input lag and so thought we would give a bit more information here before we discuss the results obtained for this display:

What is Input Lag?

Input lag is described as the lag between the output from a graphics card and the image which is displayed on the screen you are using. This should not be confused with pixel response time which describes the speed at which a pixel can change from one orientation to another. Pixel response times impact aspects such as motion blur and ghosting, whereas input lag is a delay between what is sent to the monitor, and what you actually see. Of course both do contribute to the overall performance and experience of the display when used for gaming.

 

Input Lag Measurement Techniques - The Stopwatch Program

Traditionally input lag has been widely measured by hooking up a CRT screen to the same graphics card and PC as the TFT display. By cloning the output, the user could provide a comparative test of the output of the CRT vs. the output of a TFT. A CRT would show no lag on top of the output from the graphics card which is vital for those wanting to play fast games, where reaction times are key. This is what many users are used to, having come from older CRT displays. Many high end gamers still use CRT's as well for high refresh rates and frame rates and so the move to a TFT can be worrying, especially when you start throwing in a conversation about lag of the output image.

By running the screens side by side in this way in clone mode, you can often see that the TFT lags behind the CRT. This is sometimes noticeable in practice even, but stopwatch programs have been used for many years to give a way to record and synchronise the output so that the difference could be recorded. High shutter speed photographs can then be taken to show just how much the TFT lags compared with the CRT. The level of lag really depends on the TFT display, and is controlled by many signal processing factors including, but not limited to the internal electronics and scaling chips. Some manufacturers even take measures to help reduce this, providing modes which bypass scaler chips and options which reduce the input lag. These are often reserved for gamer-orientated screens but the results are often quite noticeable.

This stopwatch method has been used for many years by many review websites and end users. It's easy to set up, doesn't cost anything and allows a reasonable comparative view of a CRT output vs. a TFT output. It can also be useful for providing a comparison between different models over time.

The method is admittedly not 100% accurate however. There are areas of inaccuracy inherent to this method. Some stopwatch programs are based on flash which can introduce issues with frame rate support, especially when viewed from an internet source and browser. The programs can introduce a degree of error if vsync is active and due to 2D native refresh rate settings of 60Hz. There's never been a defined standard for measuring input lag and so this has been used for a long time and widely accepted as a decent enough representation of what a user may experience.

 

More Advanced Measurement Techniques

Some websites take this whole area one step further and even use an oscilloscope and photosensor to measure the input lag of a display. This is of course an even more precise measurement and can help you show the true image lag along with the typical response times of a pixel transition. This is then used to give you both the overall experienced 'lag' of the image and the lag specifically between the electronics and the pixel change instruction (the pure signal processing time). We do not have access to such a method at this time and of course it would not come cheap.

We are investigating alternative means to measure input lag in the future for our reviews in an effort to help provide even more accurate results. We did not want to completely remove this section since I know it is useful to many readers and it would be missed. While it might have varying degrees of accuracy, I will say that this method has been used for many years by many sources and although there is likely a varying degree of error introduced in this method, it can still allow you to give a reasonable comparison between displays. Classification of the lag into low, medium and high for instance is possible and the method can help give you an idea of the relative output of a TFT compared with a CRT. It's an indication though as opposed to a precise measurement.

If you are particularly bothered about input lag then I would encourage you to compare results between sources and refer to other review sites as well where methods like this are used. In many cases the figures are actually quite comparable but by all means if you need absolute measurements refer to other sources as well to help with your decision.

Input Lag Classification

To help in this section we will also introduce a broader classification system for these results to help account for some of the remaining error in the method and classify each screen as one of the following levels:

• Class 1) Less than 16ms / 1 frame lag - should be fine for gamers, even at high levels

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

• Class 3) A lag of more than 32ms / more than 2 frames - Some noticeable lag in daily usage, not suitable for high end gaming

On to our tests then in their current form. The HP ZR2740w showed an average input lag of 10ms during this test, ranging up to 20ms maximum. This was on par with the older HP ZR24W in fact which showed the same average lag. The HP ZR2240w was a little higher at 25ms average, which will be related to its additional scalers which have been left off the ZR2740w. This was also a comparable figure to the Hazro HZ27WC (8.8ms) which again did not have any scalers. The ViewSonic VX2739wm performed quite similarly as well at 9.4ms average input lag.

The lag of this screen has been categorised as CLASS 1 as detailed above. This should be fine for gaming at even quite high levels.

 

Movies and Video

 The following summarises the screens performance in video applications:

• 27" screen size makes it a pretty good option for an all-in-one multimedia screen and comparable to smaller LCD TV's in size.

• 16:9 aspect ratio is more suited to videos than a 16:10 format screen, as it leaves smaller borders on DVD's and wide screen content.

• Massive 2560 x 1440 resolution can support true 1080 HD resolution content

• Digital interfaces DL-DVI and DisplayPort supports HDCP for any encrypted and protected content

• Additional DisplayPort present and good to see as it is popular nowadays and very useful for external Blu-ray / DVD player connectivity.

• Black depth and contrast ratio are pretty good for an IPS panel. Detail in darker scenes and shadow detail should not be lost due to these measurements.

• Dynamic contrast ratio is not available at all.

• No 'Movie' preset mode available at all so you would need to use your user calibrated normal mode.

• Good pixel responsiveness which should be able to handle fast moving scenes in movies without issue.

• Wide viewing angles thanks to e-IPS panel technology meaning several people could view the screen at once comfortable and from a whole host of different angles.

• Very good ergonomic adjustments available from the stand allowing you to obtain a comfortable position for movie viewing. Movements are smooth and mostly easy to use thankfully.

• No significant backlight leakage from the panel which was pleasing. Thankfully no leakage along any of the edges which has the potential to become distracting when watching movies, especially where black borders are present.

• No integrated stereo speakers on this model

• No picture in picture (PiP) or picture by picture (PbP) modes available on this model.

 

Conclusion

 

The ZR2740W had some good areas but some which left us a little disappointed. From a positive point of view, the default colour setup was pretty good apart from the overly high brightness which is easy to adjust. Viewing angles were as you would expect from an IPS panel and luminance and backlight uniformity seemed good. Pixel response times were pretty good and input lag was low. There was a very good range of easy to use ergonomic adjustments and the presence of DisplayPort was welcome along with the DL-DVI. The support of 10-bit content through the 8-bit + AFRC panel may also be welcome to some users with the appropriate workflow.

Perhaps the biggest disappointment in my opinion was the lack of an OSD menu. This meant you had very limited control over the hardware for calibration. It also meant there were no preset modes (even colour temperature modes like on the ZR2240w), no aspect ratio control, no dynamic contrast ratio, no overdrive control. All in all I think this was a shame and it did make the screen feel a little bit more limited than others. Having said that, the brightness control was very good and offered a huge range of adjustments at least. The black depth and contrast ratio were also a bit lower than we had maybe hoped for given our tests of the ZR2240w which had impressed in this area.

The screen is available at a recommended retail price of �658 GBP (inc VAT). This makes it quite comparable to the popular Dell U2711 which would be its most immediate rival I would think (~�635). It could be argued that the Dell has some higher end features for your money. It has a wide colour gamut for instance and a few additional extras like a comprehensive OSD menu, scalers for aspect ratio control, an 8-in-1 card reader and some additional interface options. The HP does however make a good alternative if you can live without those extras, and if you would prefer a standard gamut display. The ZR2740w is quite a lot more money than the Hazro HZ27WC (�350) and HZ27WD (�500) as well which are quite similar in some performance areas, but are missing some of the adjustments and functions of the HP's stand.

Overall I think the screen fits a niche reasonably well as a standard gamut 27" IPS display with a matte panel coating. It fits somewhere in between the Dell and Hazro models in terms of functions and features as well so its worth considering if you are looking for a new 27" monitor.