Introduction

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. 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 are models available in sizes of 20, 21.5, 24 and 27 inches. We have already reviewed in detail the 21.5" ZR2240w and 27" ZR2740w, and now we have with us the 24" model for a full test. This 24" model is called the ZR2440w. HP have stuck with IPS panel technology throughout the range and also now combined this with the currently popular W-LED backlighting.

The ZR2440w is marketed as follows on HP's website: "The completely redesigned HP ZR2440w 24� LED Backlit IPS Monitor is a 16:10 LED-based display with a breadth of new features and an LED backlight in a design that is ultra-modern and sleeker than ever to perfectly complement HP Z Workstations."

Specifications and Features

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

The ZR2440w offers a decent enough range of connections although in my opinion it is missing something. There are 1x DVI-D, 1x HDMI and 1x DisplayPort interfaces available. The digital connections are all HDCP certified and it's great to see DisplayPort and HDMI included for connection of popular external devices like games consoles and Blu-ray players. However, the screen is notably missing a D-sub VGA connection which I think is a shame.

The screen is packaged with cables for DVI and DisplayPort. It might have been nice to include an HDMI cable as well which would have been useful seeing as the screen offers an HDMI connection too. Presumably a cost saving exercise like on the smaller ZR2240w model.

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.

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

OSD Menu

The OSD menu is identical to that of the smaller ZR2240w model. The 27" ZR2740w does not feature any OSD at all, but thankfully the 24" ZR2440w does. I have used the photos of the OSD menu from the ZR2240w review here rather than replicate them again, so you will notice that the resolution listed is 1920 x 1080 in some of these photos. Of course this screen actually runs at a native resolution of 1920 x 1200, but the menu remains the same apart from that.

Above: view of logo and OSD operational buttons. Click for larger versions

The OSD menu is accessed quickly and easily using the left most control button. This brings you first of all to the main menu as shown below.

The main menu gives you access to 10 sub-sections. You can move up and down this list using the + (plus) and - (minus) buttons quite easily. Pressing 'ok' enters you into any of these sections where you can control the associated options. Some sections are very brief, like the brightness and contrast sections. Once inside, you can again highlight the relevant option and press ok to control it. This works well and is fairly intuitive.

There are more options available in other sections. The 'color' menu gives you access to the 3 preset colour temperature modes, as well as the customisable RGB mode. The image section gives you access to a few interesting features which we will look at throughout the course of this review. These include custom scaling, video overdrive and dynamic contrast ratio.

There are options to control the OSD menu itself and several options relating to power management in the associated sections.

The language section allows you to change the language of the menu and the information section gives you basic info about the screen and resolution. Note: the photo above of the information section has come from the ZR2440w screen as information does vary from the ZR2240w.

Finally the source control menu allows you to manually change between the different interface connections. You can also quickly switch between these using the 'source' button (which is also the +) on the front of the bezel. The photo above is from the ZR2440w menu since unlike the ZR2240w there is no D-sub / VGA option available here.

Overall I felt there was a good range of options available and the menu was easy enough to use. It might have been nice to see some more preset modes for different uses. The menu also sometimes seems a bit long-winded to exit if you have drilled into several layers.

You can access the monitors factory 'service' menu as well but be careful not to change anything without knowing what you've done or how to change it back. Use the menu at your own risk! To access the factory menu, hold the main 'menu' button down while powering the monitor on. Once on, press 'menu' again and there is an extra section available which has replaced the 'language' section. The colour of the menu font also turns green to indicate you are in this mode. Entering the service menu gives you some information about the screen including confirmation that it is using LG.Display's LM240WU8 e-IPS panel (the LM240WU8-SLA1 to be precise).

 

 

Power Consumption

In terms of power consumption the manufacturers spec states default power usage of 48W and 59W maximum. In standby the screen apparently uses <0.5W.

We tested this ourselves and found that out of the box the screen used 37.6W of power while at its default 90% brightness setting. After calibration, where we had adjusted the brightness control to 30% (custom mode) and therefore the backlight intensity, this was reduced to 24.4W. In standby the screen uses only 0.5W of power. We have plotted the results of these measurements on the graph below:

Colour Accuracy, Black Depth and Contrast

The Panel and Backlighting Unit

The HP ZR2440w utilises an LG.Display LM240WU8-SLA1 e-IPS panel which is capable of producing 16.7 million colours. The panel itself actually uses a 6-bit colour depth with Advanced frame rate control (A-FRC) to produce the 16.7m colours. This is different to regular 8-bit IPS matrices, but this is a measure taken to achieve a lower price point for these modern lower-cost displays.

The ZR2440w 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 71% of the NTSC reference, 74.3% of the Adobe RGB reference and 95.8% of the sRGB space. While a 95.8% coverage of the sRGB space is decent enough and in line with most W-LED backlit screens, some higher end uses may require a wider gamut with a full 100% sRGB coverage (and beyond) for graphics and colour work. A wide gamut screen is another option for those wanting to work outside of the sRGB colour space.

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.

Default settings of the screen were as follows:

HP ZR2440w - Default Factory Settings

  

 

The out of the box performance of the ZR2440w was reasonable. The CIE diagram on the left confirms that the monitors colour gamut (black triangle) very closely matches the sRGB colour space (orange triangle). It extends a little past the sRGB space in greens in this 2D view of gamut but is a little short in reds.

 

 

Default gamma was recorded at 2.1 average, leaving it 6% out from the target of 2.2. Gamma was actually closer to the target 2.2 in the darkest and medium greys where it was recorded at 2.20 and 2.19. This deviated as low as 1.9 in other lighter shades however. White point was a little out here at 6094k which was 6% 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 a very high 321 cd/m² which is too high for comfortable use. The OSD is set at 90% brightness and this is far too much. At this high 321 cd/m² luminance, the black depth was 0.31 cd/m². This gave us a static contrast ratio of 1044:1 which is excellent for an IPS panel and a pleasing result.

 

Colour accuracy was fairly good at default factory settings with an average DeltaE (dE) of 2.0, ranging up to a maximum of 5.4. The screen felt fairly even at least to the naked eye, although as with most screens out of the box it was overly bright. It was a little washed out as a result and felt uncomfortable to use. Some minor OSD adjustments to the brightness 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.

 

Overall this default performance was very comparable to that of the 21.5" ZR2240w and 27" ZR2740w really, with similar gamma, white point and colour set ups out of the box. All were too bright at their default setting as well, but it is easy enough to change that.

 

 

 

 

Testing Colour Temperatures

 

 

Like the 21.5" ZR2240w, the ZR2440w doesn't offer any defined preset modes for different uses and instead offers a set of 3 pre-configured colour temperature modes and a customisable mode with RGB controls. The 27" model didn't offer any OSD menu and so any kind of preset was missing there. Good to see they have been included here on the ZR2440w.

 

There are options in the 'color' menu for warm (5000k), standard (6500k) and cool (9300k). The standard mode is the default and is designed to be close to the 6500k target we aim for in our tests. We have already established that this is nearer to 6100k and is about 400k out from the specified colour temperature. As a reminder we are using an i1 Pro spectrophotometer device here which can accurately read the colour temperature of the W-LED backlighting.

 

We measured the colour temperature of the screen in each of the preset modes to establish how accurate the settings actually were. All other settings were left at factory defaults and no ICC profile was active. The results are recorded below:

 

 

As you can see, the warm setting was actually quite close to the desired colour temperature, being only -80k out. The standard mode was about -406k out which was a shame, and this would need correcting through profiling of the screen when we get into the calibration process. The cool setting was -347k out which was not far out and was recorded at 8953k. The 'custom' setting was measured at its default settings where RGB levels were all at maximum 255. This gave us a slightly cooler white point than the 'standard' mode, and was recorded at 6401k and this was closer still to the desired 6500k white point. This would be a good starting point for any calibration wishing to achieve a 6500k white point.

 

 

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 ZR2440w - Calibrated Settings, Custom Mode

Monitor OSD Option	Adjusted Setting
Brightness	30
Contrast	80
Preset Mode	Custom (RGB)
RGB Controls	220, 208, 215

	Calibrated Settings, Custom Mode
luminance (cd/m2)	120
Black Point (cd/m2)	0.13
Contrast Ratio	935:1

 

I first of all reverted to the 'custom' mode in the OSD menu which would allow me access to the individual RGB channels. During the calibration process this would allow me to make more adjustments at the hardware level which would help preserve grey tones and gradients during the profiling. This allowed me to obtain an optimum hardware starting point and setup before software level changes would be made at the graphics card level. We had seen from our colour temp tests that the custom mode also returned a white point closest to the 6500k target of our tests, so this was a good setting to begin with.

 

Adjustments were made during the process to the brightness control and to the RGB channels as shown in the table above. 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 OSD alterations, 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 (6%) had been almost completely 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 as you can see from the table above, but it was much smaller than before. White point was also corrected to 6531k, bringing it almost spot on to the target. Luminance had been reduced to a more comfortable 120 cd/m² after the adjustment of the OSD brightness control to 30%. Black depth was still very good at 0.13 cd/m² and this gave us an impressive calibrated static contrast ratio of 935:1. Colour accuracy was also improved nicely with dE average now only 0.3 and maximum only 1.0. LaCie would consider colour fidelity to be excellent.

 

Testing the screen with various colour gradients showed fairly smooth transitions with some slight gradation in darker tones being evident. There was also some slight banding in darker tones as well but this was very minimal and only really visible with gradients and not in normal use. There was also some very slight temporal noise evident, particularly in darker tones if you look very closely. This is a result of the FRC algorithm used to produce the 16.7 million colour palette. It's not something you'd notice in practice, and you do have to look very closely to see it.

 

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.

 

 

 

HP ZR2440w - Calibrated Settings, Standard mode

 

I switched to the standard mode again to see what could be achieved through profiling in this mode. The only hardware changes that would be made here would be to the brightness control, as the individual RGB channels would not be adjusted.

 

 

Again the calibration was a great success. The targets for gamma, white point and luminance had all been met nicely again. Calibrated contrast ratio was an excellent 1028:1 and dE average was 0.4 / maximum 1.4 which was excellent.

 

Again, you can use our settings and try our calibrated ICC profile if you wish, which is 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 ZR2440w against some of the other screens we have tested in a similar size range. Out of the box average dE was 2.0 which was very good really. The default colour accuracy of the screen was comparable to some of the W-LED + 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 and a little better than the default colour accuracy of its predecessor, the 24" HP ZR24W (2.5) which was a standard gamut CCFL unit. The performance of the ZR2440w was very similar to the other new ZR models in terms of default dE colour accuracy, and also in gamma and white point set up.

 

The professional grade 23" NEC PA231W was better still at 1.6 dE average. A pretty good performance in terms of default colour accuracy from the ZR2440w 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.

 

 

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 black depth and contrast ratio of the ZR2440w were excellent for an IPS panel. Calibrated black depth was 0.13 cd/m² which left us with a calibrated static contrast ratio of 935:1. These figures were taken from the 'custom' calibrated mode since it had returned us the best performance and highest level of control over the hardware itself. This was only slightly behind the 21.5" ZR2240w (1005:1) as well and pretty much identical to the Dell U2412M which uses a very similar panel, that being the SLA2 revision of the same LM240WU8 module. A pleasing performance from the ZR2440w here. This also surpassed the rather mediocre black depth and contrast ratio of its predecessor, the ZR24W, which only managed 667:1 even with our OSD contract tweaks explained in the review. This new generation of IPS panel had obviously made some improvements in contrast ratio which was great.

 

The BenQ EW2420, Samsung F2380 and NEC EX231Wp with their AMVA and cPVA panels offered some fantastic contrast ratios of ~3000:1 which IPS cannot compete with at the moment however.
 

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.

 

 

Contrast Stability

 

The luminance range of the screen was very wide with an overall adjustment range of 309.5 cd/m² which was slightly more than the manufacturers spec had suggested even (300 adjustment range from the spec). At the top end, the 100% brightness control returned us a luminance of 345.4 cd/m² which was only just shy of the maximum specified figure for the screen of 350 cd/m². The OSD menu brightness control allowed you to adjust this all the way down to 35.9 cd/m² which was very good 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 25 - 30% should return you a luminance of ~ 120 cd/m² at default settings. Black point ranged from 0.34 to 0.03 cd/m² which was again excellent for an IPS panel.

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. Between 90 and 100% the brightness range controlled is actually slightly flatter it seems as the line is not quite linear.

Static contrast ratio remained high across the range, with an average figure of 1056:1 which was excellent. It was a little less stable at the lower end of the brightness range below a setting of ~20%. These contrast measurements were plotted on the graph shown above.

 

Dynamic Contrast

The HP ZR2440w features a dynamic contrast ratio (DCR) control, which boasts a spec of 2,000,000:1 (2 million:1). Dynamic contrast ratio involves controlling the backlight of the screen automatically, depending on the content shown on the screen. In bright images, the backlight is increased, and in darker images, it is decreased. For this test I would use the colorimeter to record the luminance and black depths at the two extremes. Max brightness would be recorded on an all white screen once the DCR has caught up. Black depth would be recorded on an all black screen.   The DCR feature is available in all of the preset colour temperature modes and is accessible through the 'image control' menu. There are options for on and off. The brightness control remains active in the OSD menu and is not greyed out as it is on some screens. However, if you change those setting manually it will change the brightness and the DCR function will be disabled immediately without warning.

The tests that we carry out to measure dynamic contrast ratio involve an almost completely white and almost completely black screen. In real use you are very unlikely to ever see a full black or full white screen, and even our tests are an extreme case to be honest. Carrying out the tests in this way does give you a good indication of the screens dynamic contrast ratio in real life situations however.

Unlike a lot of screens we have tested recently, this DCR did seem to function a bit which was good. You can see the transitions with the naked eye easily as you switch between dark and light content. Like the ZR2240w the changes are very fast however so there is no gradual change or subtle transition. This function seemed to control the luminance up to a maximum of about 327 cd/m² and a minimum black point of 0.16 cd/m². This gave us a useable dynamic contrast ratio of 2044:1 which was ok, but a long way off the specified 2 million:1 of course. We tested the screen with a completely all black screen but that didn't seem to turn the brightness level down any further as it does with some screens - where it actually turns the backlight off!

Even if we took the maximum luminance we measured in the previous section of 345.4 cd/m², and the lowest black point of 0.03 cd/m², this would still only give us a maximum theoretical DCR of 11,513:1. The screen would never live up to its 2 million:1 spec though as you would have to be turning the backlight off to reach a lower black point than 0.03 cd/m². In fact it would be then tending towards infinity:1 if you consider its black point is basically then 0 cd/m² but this doesn't happen anyway. At least the feature works a bit for those who like DCR. This was to a similar level to the smaller 21.5" ZR2240w model.

 

Viewing Angles

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

Viewing angles of the HP ZR2440w are very good, as you would expect from a screen based on an e-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 greenish 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. That is a little difficult to explain but hopefully makes sense. It is only really apparent on darker content and only really if you are working in darkened lighting conditions on this model. It was not too severe.

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 ZR2440w was pretty good. Around 77% of the screen showed very little deviation from the central point and was within 10% variation of the 120 cd/m². There was a section in the top left and top right hand corner where luminance uniformity was not as good, and luminance dropped down to around 100 cd/m² (-20% deviance) which was a shame. Still overall a pretty 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 some slight clouding evident. This was not too severe at all and not something you'd notice in practice. A good result here and very similar to that which we'd seen from the ZR2240w and ZR2740w.

 

General and Office Applications

The ZR2440w offers a good solution for general office and internet applications. The 1920 x 1200 resolution and 24" screen size offer a good screen real estate to work with, and side by side splitting of the screen is perfectly useable. The slightly increased vertical resolution (1200 pixels) compared with a 16:9 format screen (1080 pixels vertically) means you do gain a bit of height which is good. I personally prefer a 1920 x 1200 screen for office work so this was a welcome break for the common 16:9 aspect ratio screens in the market.

The 0.2700mm pixel pitch offers a comfortable text size for day to day use, a little bigger than some of the modern ultra-high resolution models like the 2560 x 1440 res 27" models for instance. Default luminance of the screen was recorded at 321 cd/m² which is far too high for prolonged office use. You will want to turn the screen down to about 25 - 30% brightness to achieve a luminance of around 120 cd/m². In doing so you also reduce the power consumption of the screen which is a positive thing, especially in an office environment with multiple screens set up. The brightness control also affords you a very wide range of adjustments including a minimum luminance of around 36 cd/m² which should be fine even in darkened working conditions.

There is no D-sub connection available from this model and so you are limited to using one of the three digital interfaces. The DVI interface provided a sharp and clear image.

The ergonomics of the screen offered a great range of adjustments. It was good to see a full range of height, tilt, pivot and swivel available although they were a little stiff to use in most cases. At least you should be able to position the screen at a comfortable setting for your individual preferences. It was also good to see some USB ports available although there are no further extra features like ambient light sensors and card readers which are often useful in office environments.

 
Above: photo of text at 1920 x 1200 (top) and 1680 x 1050 (bottom)

The screen is designed to run at its native resolution of 1920 x 1200 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 1680 x 1050 resolution while maintaining the same aspect ratio (16:10) 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 more blurry. There was fairly low levels of overlap of the pixels and text was still reasonably readable. Native resolution is recommended where possible.

 

Responsiveness and Gaming

Response Time Control

Before we get in to the get into the side by side screen comparisons I want to quickly talk about the overdrive control available through the screens OSD menu. It is available within the 'image control' section under the 'Video OverDrive' option as shown above. This allows you to manually control the overdrive / RTC impulse being applied to the pixels, with a setting of on and off available. Overdrive is designed to help improve pixel responsiveness and reduce motion blur and ghosting in practice by speeding up the transitions the pixels make to change from one colour to another. You may wish to read our specs section for some further information about overdrive / response time compensation.

The screen was tested using the chase test in PixPerAn, a good bit of software for trying to quantify differences in real terms responsiveness between monitors. As a reminder, a series of pictures are taken on the highest shutter speed and compared. The images above are the best case examples from the screen with the 'Video OverDrive' function off and then on. When disabled there was a more noticeable blur to the moving image although it was not too severe. When enabled you could spot the improved response times with the naked eye, and the image became smoother and sharper and there was less noticeable blurring. If you looked very closely you could pick out some very slight overshoot of the RTC impulse where a dark trail was produced. This can be fairly common on screens using overdrive technologies where the impulse is too aggressive or poorly controlled. Fortunately here the overshoot was minimal and you can just pick out the dark halo behind the yellow head and a slight pale halo behind the car. For optimum performance in games and with fast moving images I would recommend 'Video OverDrive' is turned on.

Display Comparisons

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:

24" 6ms G2G LG.Display e-IPS (Video OverDrive = On)

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

24" 6ms G2G LG.Display H-IPS

24" 8ms G2G LG.Display e-IPS

The ZR2440w is rated by HP as having a 6ms G2G response time which implies the use of overdrive / response time compensation (RTC) technology, used to boost pixel transitions across grey to grey changes. We know this to be true as we have already looked at the OverDrive function available in the OSD menu. The panel being used is an LG.Display LM240WU8-SLA1. Have a read about response time in our specs section if any of this is new to you.

I have provided a comparison of the ZR2440w first of all above against the previous HP 24" IPS models released. The ZR2440w seems to be a good balance between the old LP2475W and ZR24W models. On the one hand it shows slightly less motion blur than the ZR24W which we found offered the best performance in practice with its overdrive feature disabled. There is a less obvious trail image on the ZR2440w although to be fair this was hardly a big issue on the ZR24W. The older HP LP2475w showed smooth moving images with very little motion blur, and at a similar level to the ZR2440w. However the RTC overshoot was more obvious on that model, and the dark trail was more pronounced.

We have also provided a comparison against the Dell U2412M which is perhaps the ZR2440w's most logical competitor. It uses a very similar panel (LM240WU8-SLA2) to the ZR2440w and is another IPS + W-LED offering in the 24" sector. Responsiveness was again good on that model although the dark overshoot artefact was again a little more noticeable than on the ZR2440w. Out of the 4 displays compared above I would say the ZR2440w has the edge.

 

24" 6ms G2G LG.Display e-IPS (Video OverDrive = On)

23" 8ms G2G LG.Display e-IPS (W-LED)

23" 5ms G2G LG.Display e-IPS (W-LED) - Trace Free setting 40

23" 14ms LG.Display e-IPS (W-LED)

Above is a comparison against 3  other screens we have tested which use IPS panel technology and W-LED backlighting, all in the 23" sector this time. The ZR2440w shows less motion blur in moving images than the NEC EA232WMi which has a 14ms response time and does not use RTC technology. It shows a similar low level of motion blur to the Dell U2312HM and has a less noticeable dark overshoot which was pleasing. The Asus ML239H is free from any overshoot artefacts but was perhaps not quite as fast as the ZR2440w. Again a great performance from the ZR2440w here.

24" 6ms G2G LG.Display e-IPS (Video OverDrive = On)

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

27" 12ms G2G LG.Display H-IPS

I have provided a comparison of the ZR4240w against the other new ZR models in the range, namely the 21.5" ZR2240w and the 27" ZR2740w. The 24" model shows some small improvements in responsiveness compared to the 21.5" model with a slightly reduced motion blur. It was quite a bit faster than the 12ms G2G rated 27" model which did not feature an additional OverDrive option to control and showed a more obvious blur of the moving image.

24" 6ms G2G LG.Display e-IPS - Video OverDrive = On

22" 3ms G2G Samsung TN Film + 120Hz

I've also included a comparison above against a gamer-orientated screen featuring a heavily overdriven TN Film panel, and 120Hz technology. The pixel responsiveness of both of this model is ahead of the ZR2440w, and the 120Hz frequency allows for improved 120fps frame rates and the support of 3D content as well. The Samsung 2233RZ remains our champion in this test.

The responsiveness of the ZR2440w should be perfectly fine for gaming, even at quite high levels. For an IPS panel it is a very good performer and at a similar level, and even a little better, than some of the faster models we have tested which was pleasing. The overdrive control should be enabled for optimum performance and although a slight dark overshoot was introduced, it was very slight and should not prove a significant problem.

Additional Gaming Features

Aspect Ratio Control - The ZR2440w supports aspect ratio control options through the OSD 'image control' menu as shown above. There are options for 'fill to screen', 'fill to aspect ratio' and 'one to one' here at least. Good to see a defined 1:1 pixel mapping option available and a mode to automatically detect and interpolate the source aspect ratio.

Preset Modes - There are no specific preset modes available for gaming, so you will either have to use your standard mode, or perhaps use one of the other colour temperature modes. The dynamic contrast ratio is available in all of these modes and works to a small degree at least.

 

Input Lag (Improved)

We have recently written an in depth article about input lag and the various measurement techniques which are used to evaluate this aspect of a display. We have also improved our method by adopting the SMTT 2.0 tool which is used to generate the results below. Please see our full input lag testing article for all the details.

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.

On to our tests then in their new format using SMTT 2.0. We have provided a comparison above against other models we have tested to give an indication between screens. However, please note that the other screens tested here were using older stopwatch methods and not the SMTT 2.0 tool.

The HP ZR2440w showed an average display input lag of 20ms during this test, ranging up to 22ms maximum. This is the overall lag of the image compared with a CRT, taking into account signal processing delay and pixel response times. This was pretty much on par with some of the other HP models we have tested (LP2475W, ZR2240w and LP2275W) which all showed an average lag of 25ms. The HP ZR24W was a little faster at 10ms than its newer counterpart. The similarly spec'd Dell U2412M was also low at 9.4ms average.

The lag of this screen has been categorised as CLASS 2 as detailed above. This should be fine for most moderate gaming still but for those wanting to play fast FPS it might prove an issue in some cases.
 

Movies and Video

 The following summarises the screens performance in video applications:

• 24" screen size makes it a reasonable option for an all-in-one multimedia screen, although quite a bit smaller than modern LCD TV's of course

• 16:10 aspect ratio is not quite as well suited to videos as a 16:9 format screen, leaving larger borders on DVD's and wide screen content.

• 1920 x 1200 resolution can support true 1080 HD resolution content

• Digital interfaces including DVI support HDCP for any encrypted and protected content

• Additional DisplayPort and HDMI interfaces are available which are very useful for external Blu-ray / DVD player connectivity.

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

• Dynamic contrast ratio is available but has very fast transitions and only works to a small degree. It should allow a DCR up to about 2044:1 however for those who like this technology.

• No 'Movie' preset mode available at all so you would need to use one of the other defined colour temperature modes or your user calibrated custom mode.

• Very 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.

• No obvious 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.

 

HP ZR24W Comparison

I know many people are going to be asking the question: "which is better, the old ZR24W or the new ZR2440w?" Since the ZR2440w is a direct replacement of the ZR24W it is likely that the older model will not be available for long. What has changed and have things improved with the new model? We will try and answer these questions for you now:

 

 

HP ZR24W vs. ZR2440w Comparison

 

 

 

Backlighting

 

The major change since the ZR24W model has been HP's move towards W-LED backlighting from CCFL. Both screens offer a standard gamut colour space, but W-LED is certainly the popular choice of manufacturers at the moment. This has environmental and energy saving implications which are of course attractive given the focus on carbon footprints and the like. The LED panels are arsenic and mercury-free for example. We had unfortunately not measured the power consumption of the ZR24W when we tested it, but as an indication FlatpanelsHD had measured a consumption of 49.0W after calibration, where brightness had been adjusted to 0%. This had achieved a luminance of 132 cd/m² in their tests (and ours in fact). From our ZR2440w tests we have measured a calibrated power consumption of 24.4W, and a minimum (at 0%) of 17.0W. The move to W-LED has certainly helped lower power consumption which is good.

 

It should be noted that W-LED backlighting does not necessarily offer you any advantages in terms of colour reproduction, contrast ratios, black depth, or uniformity. These are often incorrectly assumed to be impacted by the change, when in fact those are features of the panel itself rather than the backlighting unit employed. The use of W-LED does allow for a much thinner profile of the screen with the ZR2440w measuring 61.0 mm depth, while the ZR24W was 86.5 mm.

 

Above: Side views showing the profile of the ZR24W (left) and ZR2440w (right). Click for larger versions

 

Features and Specs

 

Both models are very similar here and offer a very wide range of ergonomic adjustments from the stand which was great to see. They both offer 4x USB 2.0 ports which are useful. The main difference is with the video interfaces where the D-sub VGA connection from the older ZR24W model has been dropped and replaced by a digital HDMI. Nowadays HDMI is very popular for connection of external devices so overall I would say this was a positive thing. I would personally have liked them to include a D-sub as well and it was a shame to see it left off really.

 

Performance

 

I've included a table summarising these screens side by side based on the testing we have carried out and on my opinions. The screens are colour marked as green (winner) or red (loser) in each category which should be self-explanatory. Where I was not able to separate the two they are shown in grey. I will justify each result below:

 

 

• Features - There's not really anything to separate the two here, both have a good range of adjustments and a 4 port USB 2.0 hub.

• Interfaces - I've given the slight edge to the ZR2440w since it has an HDMI input instead of the D-sub of the ZR24W. This is probably more useful to people nowadays.

• Calibrated power consumption - The power consumption of the ZR24W even at its lowest brightness setting was 49.0W, whereas the ZR2440w offers a much lower consumption of 24.4W when calibrated and at 30% brightness / 17.0W at 0%.

• Panel Uniformity - I have marked these two screens as level in this test as there's nothing really to separate them from the samples we have reviewed.

• Office and Windows - There's very little to separate them all here so I've marked them as level. Same features, pixel pitch and resolution.

• Viewing angles - There's very little to separate them all here so I've marked them as level. Both are e-IPS based so offer good fields of view.

• Movies Overall - The new ZR2440w wins here as it has a much better black depth and static contrast ratio, it has a higher dynamic contrast ratio available and it has an HDMI interface that was not available on the older model.

• Responsiveness - They are all very close really but the new model does show some reduced motion blur in practice.

• Input lag - The ZR24W had a 10ms lag when we measured it while the ZR2440w is 20ms average. Neither are particularly high but the older model is a little better here.

• Minimum luminance - The ZR24W was quite limited here, only being able to reach 132 cd/m² even at 0% brightness. The ZR2440w has a much wider range available and can reach as low as 35.9 cd/m².

• Colour accuracy Default - Out of the box, the ZR2440w was slightly better with an average dE of 2.0 compared with 2.5 on the older model.

• Black depth - The new model wins comfortably here with a much lower calibrated black depth of 0.13 cd/m², compared with 0.18 cd/m² of the ZR24W. A nice improvement made with this newer model.

• Static Contrast Ratio - as a static number of 935:1, the ZR2440w is the best in this test. The ZR24W only managed 667:1 which is fairly low and that was after the adjustments and tweaks we had made in the review.

• Dynamic Contrast Ratio - Both work a little bit, but the ZR2440w offers a higher available DCR, largely down to its better static CR figure.

 

Overall I felt that the ZR2440w was a very good improvement and upgrade over the older ZR24W model. HP have managed to improve the screen in nearly every area to some degree. Some aspects such as black depth, contrast ratio and luminance range were improved quite significantly. If you have a ZR24W already then I'm not sure it would be worth upgrading and spending a lot of money for a new screen when overall performance characteristics are quite similar. If you are buying new, then I would recommend the ZR2440w as the better choice between the two certainly.

 

Conclusion

The ZR2440w impressed us both as a decent 24" screen and as an update to the popular and successful ZR24W. Feature wise there was about everything you would really need from this screen with a decent range of ergonomic adjustments from the stand, and a decent set of video connections. There was a USB hub available too and although we did miss a D-sub connection it was positive to see HP add an HDMI in its place.

It was also pleasing to see HP have stuck with IPS panel technology here offering some very good all round performance. It's combination with W-LED backlighting helped from an environmental point of view and gave the screen a thinner, more attractive profile at the same time. Some areas were improved significantly over its predecessor with a much better black depth and contrast ratio being perhaps the most notable. Response times were very good and input lag was pretty low too. As we have said in the previous section, this was a good update to the ZR24W in pretty much every area which was great.

The ZR2440w has a RRP of �378 GBP (inc VAT) and can be found for ~�345 in the UK. This does put it a little more expensive than the popular Dell U2412M (�270) which is bound to draw comparisons, and is at the end of the day fairly similar in most areas. If you want an alternative to the Dell though, with some very good all round performance then this would be an excellent choice in the 24" sector.