NEC have just released the latest in the line-up of their professional PA series monitors. We have already fully tested the 24" PA241W back in April, and more recently the 27" PA271W at the end of August. These new screens are aimed at colour enthusiasts and the professional market and offer some excellent performance to meet the high demands of their users. The new PA231W is 23" in size, entering a sector which has seen some interesting developments over the last couple of years. While there are of course the usual TN Film panels available, there has been an influx in the higher end IPS based screens, owing largely to the launch of the so-called e-IPS technology. This has helped drive production costs down, making it affordable and sensible for display manufacturers to launch IPS panels into the relatively low cost 23" base. We've already looked at models such as the NEC EA231WMi, Dell U2311H and ViewSonic VP2365wb which are all very popular in this size.

NEC are trying something a little different here though, as they aren't trying to directly compete with these other IPS models. After all, they already have the EA231WMi available at the lower cost end. Instead the PA231W is made "for creative professionals, semi-medical, precision engineering and demanding corporate office applications." They have brought many of the advanced features from the 24" and 27" models into this sector, separating this as a much higher end model than the  EA231WMi (and relative Dell / ViewSonic products). Some of these features include a 14-bit 3D LUT, ColorComp uniformity compensation and hardware calibration. We will take a look at these features later on, but for now let's have a look at the specs:

 
Above and below: Front and back views of the PA231W. Click for slightly larger versions

The PA231W is much like the 24" and 27" models in design. The whole screen is a matt black finish, with a thin ~16mm bezel around the screen and a black stand and base. The screen is a little thinner than the 24" model, at around 70 mm but the overall design is the same. It's quite square in feel and everything is quite neat and tidy. There is a carry handle at the top on the back of the screen and although it's a little lighter than the 24" model, the PA231W is still pretty heavy at 10.2Kg. The panel features a normal Anti-glare (AG) coating as opposed to any glossy solution. It is a fairly grainy coating as is common for IPS panels and so some people might be bothered by the grainy or 'dirty' look, particularly on white. However, this AG coating is the popular choice for professional grade screens and is nothing new.

The screen offers a very good range of ergonomic adjustments as you would hope. There is a 150mm height adjustment which offers a very decent range and is smooth and easy to manoeuvre. The side to side swivel is also smooth and easy and allows you to angle the screen how you need without any fuss from -45 to +45°. The tilt range is again very good offering between -5 and +30° movement. This is smooth enough when tilting the screen backwards, but moving it downwards is quite stiff. There is a rotate feature as well to swap between landscape and portrait orientations. This is easy to operate and smooth and at this size is actually fairly useable. The stand was very sturdy and there was no major wobble from the screen which was pleasing. Materials were very good and the built quality felt excellent.

Above: the screen in portrait mode showing the interface options on the underside

The screen offers 2x DVI-I, 1x D-sub and 1x DisplayPort interfaces for connecting devices and computers. These are located on the underside of the back of the screen as shown above. These were the same interfaces offered on the PA241W and PA271W, although the 27" model did not feature D-sub as the analogue connection cannot support that screens ultra-high native resolution. It was good to see DisplayPort included as that is a popular option nowadays, but it might have been nice to see one or two HDMI connections as those are very widely used for games consoles, DVD / Blu-ray players etc. There are also 2x upstream USB ports on the back for connecting to different PC's if you wish. The  2x downstream ports are next to them, and are accompanied by a third port on the right hand edge of the screen for quick access. Sadly there is no memory card reader on this model though, which is something I find useful personally.

Above: OSD operational buttons

In the bottom right hand corner are the buttons for controlling the OSD menu, as shown above. There's the ambient light sensor as well (far left) which helps detect your working conditions and adjusts the brightness automatically if you have the feature enabled. The power LED glows a fairly bright blue colour but can be turned down (or up) in the advanced OSD menu, or even changed to green. In standby it glows orange. The OSD menu buttons give quick access to interface input (input button), brightness (left and right), the picture preset modes (up and down) and Picture In Picture on/off selection (PiP button).

The OSD menu is pretty thorough and easy to navigate. Pressing the 'menu' button on the controls brings up some guidelines in the bottom right hand corner of the screen as well, telling you what each of the buttons will do in the given menu section. There's all the usual options for brightness, contrast etc as you would hope. NEC have changed the brightness control from being a luminance figure (as on the 24" and 27") to a percentage on this model.

The image above shows the colour preset mode screen where you can select between a series of presets Being only a standard gamut screen (unlike the 24" and 27" models), there are different options available here. There are options for REC- bt709, sRGB, High Bright, Full and Programmable. Obviously there is no need for an AdobeRGB mode as the gamut is not wide enough to cover this space. More on those later. You can also control colour temperature (white point) and six axis adjustment of colour channels.

The colour settings menu also gives you access to the 'advanced menu' which looks like the above. Once you've entered into here you have even more control over settings, and there is now access to advanced features relating to panel uniformity and response time which we will look at later.

The menu also gives access to the Picture In Picture and Picture By Picture modes available. There's plenty of options here for displaying multiple inputs at once, and the configuration is also shown above.

One last section I wanted to mention now was the 'AmbiBright' auto-brightness feature. You can select this in the advanced menu and it enables the ambient light sensor built into the screen. This automatically adjusts your backlight (brightness) setting depending on your working conditions. Tranisitions were smooth and effective and this is a nice feature in my opinion. I like to see this from modern screens, very handy for office work and changing lighting conditions in your room.

 

In terms of power consumption the spec states typical usage of 46W (reduced down to 37W in Eco Mode 2) and a mere 1W when in standby / sleep mode.

We tested this ourselves and found that out of the box the screen used 34.0W of power. This was reduced to 30.9W after calibration (see calibration section) which was recorded from the hardware calibrated SpectraView II profile. In standby, the screen used only 1.2W of power. The screen became slightly warm at the top on the back of the display, but nothing bad at all. There was a very slight buzzing detectable from the screen when up very close.

Colour Accuracy, Black Depth and Contrast

• Panel Technology - You may be familiar with the latest generation of so-called "Performance IPS" (p-IPS) panels which NEC have been using in their other PA series monitors. The panels featured in the 24" PA241W and 27" PA271W are 10-bit capable (8-bit +AFRC) giving rise to a 1.07 billion colour palette. These support 10-bit colour depth if you have the full 10-bit workflow and can take advantage of it through your hardware. The practical benefit of these new panels is debatable and there are very few circumstances at the moment where you could even take advantage of it. While the 24" and 27" models use these 10-bit p-IPS panels, the PA231W uses a more standard 8-bit panel, capable of producing 16.7 million colours. LG.Display do not manufacturer a 10-bit IPS panel in the 23" sector at present, so they have stuck with a normal IPS panel for this PA231W model.
   

• Colour Gamut - Unlike most modern displays, the screen does not use wide colour gamut W-CCFL backlighting and instead sticks to a standard sRGB colour space. This equates to a  coverage of approximately 72% of the NTSC colour space. It is important to consider what colour space you will want to work with, so make sure you understand the differences between standard and wide gamuts. I would thoroughly recommend a read of this article over at X-bit Labs, which covers the pros and cons well. Many people prefer to work with standard gamut displays, and like some of the other new IPS models in the 23" sector (Dell U2311H, NEC EA231WMi, ViewSonic VP2365wb for instance), this PA231W offers you that,
   

• Programmable LUT - Like the bigger models, the PA231W offers a programmable 14-bit 3D LUT to help offer smooth gradients and provide clarity in subtle detail. As well as being 14-bits per channel, the LUT is described here as being 3D. Whereas a typical 1D LUT adjusts colour on separate tables for each red, green, and blue, a 3D LUT accomplishes this on a single, mixed-colour cubic table. A 3D LUT improves the monitor's additive colour mixture (combination of RGB), a key factor in its ability to display neutral grey tones.

 

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 set it to its standard profile. The PA231W was tested at default factory settings using the DVI interface, and analysed using LaCie's Blue Eye Pro colorimeter and their accompanying software suite.

It should be noted that out of the box, the screen has ECO mode 1 activated, along with the auto brightness control. For the purposes of these tests, I turned these functions off as I did not want the backlight fluctuating during the measurements. ColorComp uniformity adjustment and Metamerism were also disabled by default.

Default settings of the screen were as follows:

NEC PA231W - Default Factory Settings, High Bright Preset

 

The results of the PA231W at factory settings were very good. On the left you can see the CIE digram demonstrating the colour space of the monitor (black triangle) against the reference sRGB space (orange). The screens colour gamut closely matches the sRGB reference, extending a little too far in red shades and not quite covering all green shades. This is confirmation as well that the backlighting unit is a standard gamut CCFL system.

 

Gamma was well set up out of the box with a reading of 2.2 average, being only 2% out across the readings from our target of 2.2 which is the default for computer monitors. Colour temperature was recorded at 6066k, a little way out (7%) from our target of 6500k, the temperature of daylight. Luminance was a bit too low at default which is quite rare, being at 108 cd/m², a bit off our target of 120 cd/m² which is the recommended luminance for LCD screens in normal lighting conditions. The default settings could do with being a bit brighter, but at least the screen was useable and not blindingly bright like some modern screens. Black depth was recorded at an excellent 0.11 cd/m², giving a very impressive static contrast ratio of 985:1. A fantastic result from an IPS panel here in this regard.

 

In terms of colours, the screen felt even and comfortable to the naked eye, with no obvious tendancy towards any shade. Testing with the colorimeter revealed the graph on the right hand side above, showing DeltaE (dE 94) values across 16 shades. As a reminder, the lower these bars down the Y-axis, the better, in terms of colour accuracy. For reference, LaCie describe the DeltaE readings as:

• 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.

 

The default settings offered a very good colour accuracy. dE average was 1.6 leaving a slight difference between the colours being requested and those being displayed. This ranged up to 4.9 in the worst cases in the blue shades. Not a bad performance at all and this should be adequate for most casual users who don't have access to a colorimeter for  profiling and calibration. The screen appears to have been well set up in the factory for gamma and colour accuracy.

 

 

NEC PA231W - Default Settings, Full Preset

 

For completeness I also tested the screen at factory settings in a couple of the other preset modes. Here I switched into the "full" mode. The white point changed to 6500k automatically in the OSD at this point from the default of 'native'.

 

The gamma, luminance and colour temperature were all pretty much as they were in the High Bright preset. The colour accuracy was however a bit worse with dE average of 2.9 and maximum of 7.0. The black depth was 0.12 and although contrast ratio had dropped a little to 912:1, it was still very good.

 

NEC PA231W - Default Settings, sRGB

 

There is an sRGB preset mode available for the screen as well. On the bigger models, this served as an emulation mode for the smaller colour space, helping to restrict the gamut of the otherwise wide-gamut panels. In this instance, the backlighting is already standard gamut, so this sRGB mode doesn't do the same thing. It does actually change the colour space a little though if you compare the above CIE  diagram with those from the high bright / full modes. The coverage in greens and along the green > red edge is reduced a little compared with the other modes.

 

The main noticeable difference to the naked eye is the big drop in luminance. The OSD brightness setting had changed from 50% to 21.4% when entering this preset. Our colorimeter measured luminance down at only 56 cd/m². With a black depth of 0.06 cd/m², this gave us a contrast ratio of 917:1. Again very good and only a little less than the high bright preset. Colour accuracy was fairly good on average as well with dE average of 2.5 and maximum of 6.2, although not as good as the high bright mode again.

 

 

Calibration Results

 

I wanted to calibrate the screen in each of the main preset modes to determine what was possible with optimum settings and profiling. I use the LaCie Blue Eye Pro colorimeter and software package to achieve these results and reports.

 

Please remember that these are all software based graphics card profiling "calibrations" as opposed to hardware level true calibration which we will come onto shortly. These are the normal calibration methods we use for our monitor reviews which creates a profile which is activated at a software level in the graphics card. This is more than adequate for most users and is all you really need for nearly all the mainstream monitors anyway. In fact, most don't even have the option for hardware level calibration, so you have to make do with software profiling only. For professional use and high end colour work these kind of profiles, although good, are not acceptable. You need full hardware calibration which can make adjustments at a hardware level and to the monitors extended LUT. This is what the high end professional market need and want from a screen. The PA231W offers the hardware capabilities to do this form of calibration as well, which we will come onto shortly.

NEC PA231W - Software Calibrated Settings - High Bright Preset

Monitor OSD Option	Adjusted Setting
Brightness	60
Contrast	n/a
Preset Mode	High Bright

	Calibrated Settings, High Bright
luminance (cd/m2)	119
Black Point (cd/m2)	0.13
Contrast Ratio	912:1

 

To carry out this initial software calibration I switched back to the high bright preset mode. I followed LaCie's calibration process through, adjusting the OSD settings in line with the recommendations made in the process, and then letting the software carry out the LUT adjustments at a graphics card level and create an ICC profile. The screen does offer a hardware LUT calibration option which I will look at shortly, but for now the majority of corrections would be carried out at a graphics card LUT level and through profiling.

 

The calibration was a success. While gamma was already very accurate out of the box as we had seen, it was corrected to 2.2 exactly now. The process had obviously done a good job at adjusting colour temperature and luminance as you can see above, both being pretty much spot on now compared with our target settings. Black depth was a still very low at 0.13 cd/m², and contrast ratio was a very impressive 912:1. This was an improvement over the black depth of the PA241W (0.17) and PA271W (0.20) which was excellent.

 

Colour accuracy was also corrected nicely as well, offering an even better result than the factory default. Average dE was now 0.2 with a maximum of only 0.5. LaCie would consider colour fidelity to be excellent now across the board.

 

Testing the screen with colour gradients revealed some very slight gradation in darker tones, but no banding or issues were present. These were very smooth gradients thanks to the extended 14-bit LUT and 16-bit processing. Excellent results here and an important aspect for colour critical work. You can use our settings and calibrated ICC profile on your PA231W as well if you want. See our ICC profile database for more information.

 

NEC PA231W - Software Calibrated Settings - Full Preset

Monitor OSD Option	Adjusted Setting
Brightness	65
Contrast	n/a
Preset Mode	Full

	Calibrated Settings, Full preset
luminance (cd/m2)	120
Black Point (cd/m2)	0.15
Contrast Ratio	800:1

 

I software calibrated the screen this time in the 'full' preset mode. Out of the box this returned poorer colour accuracy than the high bright mode, and a slightly lower contrast ratio. Again gamma, colour temperature and luminance were all corrected nicely. The black depth was not quite as good now which was a shame, but still a very decent 0.15, giving us a contrast ratio of 800:1. Colour accuracy was improved from the default of 2.9 / 7.0 to 0.3 / 0.8 which was excellent. Again ICC profile available if you want it.

 

NEC PA231W - Software Calibrated Settings - sRGB Preset

Monitor OSD Option	Adjusted Setting
Brightness	30
Contrast	n/a
Preset Mode	sRGB

	Calibrated Settings, sRGB preset
luminance (cd/m2)	121
Black Point (cd/m2)	0.15
Contrast Ratio	806:1

 

I also software calibrated the screen in the sRGB preset mode. This returned similar results to the 'full' preset. Gamma, colour temp and luminance were all well corrected, but black depth and contrast ratio were a bit behind the calibrated high bright mode. The colour accuracy was improved from the default 2.5 / 6.2 to 0.6 / 1.5, although it was not quite as accurate as the high bright and full modes. Again ICC profile available if you want it.

 

 

 

SpectraView Calibration

 

To take full advantage of the screen for calibration and profiling, NEC have built in a hardware calibration feature which allows you to make corrections to the monitors 14-bit 3D LUT. This can provide even better colour accuracy and allows you to store your calibration in the screens hardware. Professional markets and those working with colour critical content require this kind of high end hardware calibration so this is one of the reasons this screen separates itself from the more mainstream models. NEC have their own specific software for this hardware calibration which is called SpectraView.

 

 

 

There are actually two versions of this software, both offering different capabilities in terms of the calibration possible:

1) SpectraView Profiler - A European piece of software provided by BasICColor. High end software with a lot of features and the possibility of some excellent results. In Europe, this is the software which NEC recommend with their PA series. However, to take full advantage of the hardware calibration you must have the specific SpectraView (SV) version of the screen. The regular PA model (like the one we have with us here) will only allow automated basic OSD adjustments and software level calibration. You cannot calibrate the monitors internal LUT unless you have the SV edition of the screen which is a higher cost.

 

2) SpectraView II - A piece of software provided by NEC in the USA instead of the Profiler software. It's less complicated and not quite as in depth but fully automated and easy to use. This will allow you to calibrate both the standard and SV versions of the screen, whichever country you are in at a hardware level which is good. This software will allow us to calibrate the PA231W at a hardware LUT level even in the UK.

 

There are other factors which come into play when talking about the SV version of the screen and the Euro and US versions of the SpectraView software. Please see the full detail in our PA271W review for further information.

 

 

 

SpectraView Profiler

 

I first calibrated the screen using the SpectraView Profiler software v 4.1.22. This only allowed me to carry out the combined hard- and software calibration since I was testing the regular PA231W as opposed to the SV version. This does automatically control the OSD settings for basic functions such as brightness and so the process is fully automated. Within the software we had defined our review targets (2.2 gamma, 6500k colour temperature and 120 cd/m² luminance). Once you start the calibration the screen enters the 'Programmable' preset mode and you cannot change the OSD controls manually without reverting to one of the other preset modes.

 

 

Once calibrated the SpectraView Profiler software presented us with the above summary screen. All targets had been met nicely, and this had returned a black depth and contrast ratio similar to that which we saw from the Full and sRGB preset mode calibrations.

 

Note: From what I could tell, the SV Profiler software does not allow you to change any of the monitor OSD settings from within it. If you carry out this calibration it will enter you into the Programmable preset mode. The default ColorComp (uniformity compensation) setting for this preset is "level 5" and within the Programmable preset mode, you cannot change this in the OSD, even from the advanced menu section. So what I'm saying is, if you calibrate using this software you will be stuck on ColorComp level 5 normally. This does improve uniformity (see further down) but does negatively impact contrast ratio. In fact when I first ran this test, the contrast ratio was only 625:1, not the 801:1 shown above. To overcome this, you need to enter into the SV II software which we will look at in a moment, which does allow you to change the monitor settings from within it. Here you can turn off the ColorComp within the Programmable preset mode. The results above and below are based on ColorComp having being turned off so as not to impact contrast ratio.

 

 

Performing a validation at the end gives you more detailed results of the calibration. Oddly this then recorded a contrast of 828:1 (slightly higher) but this was very close to what the summary had said anyway. This report did give us colour accuracy readings in which average dE was a very good 0.26, ranging up to 0.69 maximum. A great performance here and the screen has been well calibrated.

NEC PA231W - SpectraView Profiler, European Software

 

I performed a test and report with the LaCie software as well to validate the performance from their point of view. This confirmed a very accurate calibration with the SV Profiler software. Targets for gamma, colour temperature and luminance were all met well. As we had seen from the SV software, black depth was 0.15 now, giving us a contrast ratio of 800:1. A good result and on par with the kind of output we saw from the Full and sRGB modes. For maximum contrast ratio, you would need to use the High Bright preset and rely purely on software based calibration and profiling. Colour accuracy was recorded with an average dE of 0.6, maximum of 2.0. Please note that the minor differences are most probably related to the fact that we are combining two pieces of different software here.

 

 

 

SpectraView II

 

I also calibrated the screen with the US SpectraView II software. Even though I was only using the standard PA231W model, this software did allow me to carry out a fully automated hardware level calibration of the screen. Corrections would be made at a hardware LUT level, adjusting the screens 14-bit 3D LUT. The profile would be stored in the monitor itself bringing another level to performance accuracy for professional uses. Since the calibration is stored in the hardware the results are carried over between  different applications and workflows, including video and games where a software ICC profile is not usually retained. I allowed the SpectraView II software to carry out the calibration, which resulted in the screen switching into the 'programmable' preset again. This was renamed as 'SpectraView II' now in the OSD menu.

 

 

After the calibration is completed you are presented with the above report. Colour temperature was calibrated to 6582k, luminance to 119.1 cd/m², black depth of 0.14 cd/m² and gamma of 2.2. This method did return us a very good static contrast ratio of 876:1. very close to the LaCie calibrated results we obtained in the High Bright mode (912:1) and a bit better than the full, sRGB and SV Profiler presets.

 

 

The gamut tab of the report confirms the monitors colour space as compared with the sRGB standard.

 

 

The gamma curves are also shown, with the calibrated curves matching the targets very closely as you would hope.

 

 

The colour tracking tab confirms colour accuracy across the greyscale. dE average was 0.83, with maximum of 1.31. We will compare this with LaCie's report as well now.

 

NEC PA231W - Hardware Calibration, SpectraView II USA Software

Monitor OSD Option	Adjusted Setting
Brightness	automatic
Contrast	automatic
Preset Mode	SpectraView II

	Calibrated Settings, SpectraView II
luminance (cd/m2)	119
Black Point (cd/m2)	0.14
Contrast Ratio	851:1

The LaCie report confirms the results from the SV II software. All targets were met very nicely, with only a very minor difference (1%) which can be put down to differences between the two pieces of software. Contrast ratio was 851:1 which was a bit better than we'd seen from the SV Profiler software, and a very good result for an IPS panel. Colour accuracy was excellent as well, with dE average of 0.6 and maximum of 1.6. Again a very good calibration, now with the added advantages of hardware level correction.

 

 

Calibration Performance Comparisons

 

I thought it would be useful to summarise the results from each of these preset mode calibrations in one place. The results of the SpectraView calibrations are recorded using the LaCie reports in order to keep all of these uniform:

 

 

I tested the screen with colour gradients in each of these calibrated preset modes. The gradients were very smooth and showed no sign of banding. There was some very slight gradation in darker tones in my gradient tests which is common to 8-bit displays but this was less noticeable than on some other screens thanks to the 14-bit 3D LUT and extended 16-bit internal processing.

 

Overall, the screen could be very well calibrated in all preset modes and using both software based and hardware based methods (or a combination of the two). The screen had been calibrated in all 3 main preset modes at a software graphics card LUT level using the LaCie Blue Eye Pro package. All the results were very good, with the high bright preset holding the slight edge in terms of colour accuracy and contrast ratio. At a contrast ratio of 912:1 it was a fair bit better than the other modes which were around 800:1.

 

We also then calibrated the screen using NEC's SpectraView Profiler software from Europe (v4.1.22) which carried out corrections at a graphics card LUT level, along with some control of basic hardware controls like brightness and RGB channels. This produced similar results to the LaCie calibrations in the full and sRGB modes. The US version (v1.1.05) of the SpectraView II software allowed full correction at a hardware LUT level using a matrix profile, making use of the 14-bit 3D LUT and providing significant benefits beyond what we can really tell from these reports. It again produced similar results in the LaCie report as the software based calibration had, with only minor variations down to differences in the software more than anything else. Contrast ratio was a bit better than the SV Profiler calibration.

 

It should be noted that because the software was making adjustments to the hardware LUT, there are many more accute and detailed corrections being made which brings benefits when you come into high end graphics and professional uses. This is the type of calibration high end users would want to conduct and is the preferred option when you have a professional grade screen like this. One other thing to note is that the profile is activated and stored in the monitor itself and so is always active, no matter what workflow you are using. You don't have to worry about whether your graphics card profile is loaded in a certain application or during games / movies for instance and the benefits of a correct calibration can be carried over between each application. For even more accurate results the European SpectraView Profiler software should be combined with the SV edition of the monitor, combining tuned and tweaked screens with table based profiling at a hardware level.

 

I've plotted the results from the PA231W above as compared with some of the other 23" models and competing screens which we have tested. Out of the box, the PA231W offered some of the best colour accuracy we have seen (dE average 1.6). This was slightly behind the 27" PA271W (1.1), but ahead of the 24" PA241W (4.2) which was pleasing. It was also superior to the other three 23" models featuring the same panel (Dell U2311H, Viewsonic VP2365wb and NEC EA231WMi) which ranged between 2.4 and 2.7 average dE.

 

Once calibrated the PA231W offered the joint best results in this test that we have seen from all our reviews, with dE average of only 0.2 and maximum of 0.5. It tied the NEC 2490WUXi, NEC EA231WMi and Viewsonic VP2365wb for this honour. Interestingly two of those models use this same panel showing what is possible from a modern IPS matrix.

 

Again keep in mind there is more to this than just a validation of a colour profile and colour accuracy reports, which does separate this screen from the more mainstream models. This kind of area can get very complex and go into a lot more detail than we have here, but needless to say the other high end features of this screen (and the PA241W / PA271W) like 3D 14-bit LUT's, hardware calibration, ColorComp etc separate it from the lower cost mainstream models you see it compared against when it comes to high end professional uses.

 

 

Calibrated black depth was also the best we have seen from these similar models. At 0.13 it was ever so slightly ahead of the three models using the same IPS panel (Dell = 0.14, Viewsonic = 0.17, NEC EA = 0.15). It was a fair way ahead of the PA241W (0.17) and PA271W (0.20) as well. The smaller modern IPS matrices seem to have a better ability to render a deep black at the moment. Contrast ratio was therefore the best as well at 912:1 once calibrated. This was a significant improvement over the 24" and 27" models again.

 

 

 

Advanced Colour Options

 

I'll give brief mention to some of the more advanced options available with the PA231W for colour adjustment. These are also present on the 24" and 27" models..

 

 

Contrast Stability

 

 

The brightness control of the screen allows you to control a very wide range of luminance values, from 194 cd/m² at the high end, all the way down to only 14 cd/m² at the low end. The 100% brightness setting offers you a maximum luminance of 194 cd/m², which is more than adequate for most users I'm sure, but is shy of the advertised 270 maximum brightness. Black depth is an excellent 0.19 cd/m² at this setting however, and this gives us an excellent 1022:1 static contrast ratio. This was a very impressive performance from an IPS matrix. The backlighting can control the screen down to a very low 44 cd/m² when you reach the lower end of the controls (14.3% - see next section as well). Black depth at this setting is 0.04 cd/m². You will probably want a brightness setitng of around 50 - 60% to achieve a comfortable luminance of around 120 cd/m².

 

The contrast ratio was reasonably stable across the 100 - 14.3% adjustment range. Average contrast ratio was 1053:1 but you will see from the graph below that it did fluctuate a bit. To calculate the average contrast ratio I've ignored the contrast ratio readings below 14.3% setting for reasons below.

You will notice in the table above two readings which are highlighted in red font. The control of the backlight intensity stops when you reach the OSD setting of 14.3%, and for all intents and purposes you are at the lowest setting here. However, the PA231W (like the 24" PA241W and 27" PA271W) does allow you to reduce the luminance of the screen even further down to a setting of "0%" as it's labelled in the OSD. As you go below the 14.3% setting, the OSD shows the value in pink, and indicates that you are no longer making backlight adjustments, but you are making digital alterations at the controller board level. This has the effect of lowering the luminance of the screen even more, but since this is a digital white level adjustment only, it does affect contrast of the screen. Black depth cannot go any lower since you are not able to reduce the backlight intensity any more, and so even though white level is changing with the digital alterations, black depth remains at ~0.04 cd/m². Therefore the contrast ratio drops from ~1098:1 to as low as 358:1 at the lowest setting.

 

Compared with most other monitors you would only normally have access to the backlight intensity control so the PA231W's performance from the 100 - 14.3% setting is in keeping with other models we have tested. All NEC have done is add an additional digital control should you wish to reduce luminance even further. If you don't want to use this digital adjustment, but need a lower luminance than the 44 cd/m² we achieved at 14.3% OSD setting, remember you can achieve lower results through calibration procedures and adjustments at a graphics card LUT level.

 

Viewing Angles

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

Viewing angles of the PA231W were generally very good and indistinguishable from the other 23" models we've been discussing which use the same panel. Being IPS based, you can expect wide fields of view in all directions, also being free from the VA off-centre contrast shift and the obvious limitations of TN Film matrices. Horizontally there was a contrast shift detectable from angles of >45°. Vertically the contrast shift was more pronounced, with a rather obvious change from above, and a slightly less obvious change from below. Nothing too serious, but I did feel it a was a little more restrictive than some other IPS panels. On dark / black images there was a pretty obvious white glow from an angle which is inherent to modern H-IPS panel structures.

 

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 LaCie Blue Eye Pro 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 - ColorComp Off

I ran this uniformity test first of all with the ColorComp feature disabled. This is a technology which helps improve panel luminance uniformity and worked very efficiently when we tested the PA241W and PA271W. We will test this technology on the PA231W in a moment. The results of this initial test were mediocre. The panel's luminance was not as uniform as we had seen on the 24" and 27" models, and there was a significant drop along the left hand side of the screen as you can see. Luminance ranged down to 93 cd/m² in the worst cases (29% deviance). 71% of the screen was within 10% variation from the target which was ok, but not great.

The PA231W uses the same LM230WF2 LG.Display e-IPS panel as used in other models we have already tested. We saw a similar story with the Dell U2311H, NEC EA231WMi and Viewsonic VP2365wb in the uniformity tests with a noticeable difference between the left and right hand sides in this test. To be fair it was more of an issue on these other lower cost screens than it is here on the PA231W. Presumably given the cost of the screen and the professional target audience, NEC have probably hand-picked higher end panels for this screen to ensure fewer issues than on the other models.

 

Uniformity Mode - ColorComp

 

   

 

This function electronically compensates for the slight variations in the white uniformity level as well as for deviations in colour that may occur throughout the display area of the screen. These variations are characteristic of LCD panel technology. This function improves the colour and evens out the luminance uniformity of the display. Note that using the 'Uniformity' feature does reduce the overall peak luminance of the display. If greater luminance is desired over the uniform performance of the display, then this option should be turned off. A higher number produces a better effect, but may also reduce contrast ratio.

 

Uniformity of Luminance - ColorComp Level 5

 

After switching to ColorComp level 5 there was a significant improvement in the uniformity of the display. This was a much better result, and some of the best we have seen. The technology worked very well here as it had on the 24" and 27" models. Uniformity ranged down to only 114 cd/m² in the worst cases, being only 5.26% out from the target. 100% of the screen was within 5.5% of the target which was excellent.

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. Although the image above does emphasise the issue a little, there was some noticeable backlight bleeding coming from the four corners of the screen. This is a similar story to what we saw with the EA231WMi. In the case of the PA231W, luminance uniformity was good, and excellent in fact with ColorComp enabled. However, backlight bleed from the corners is a small issue even on this high end model.

 

General and Office Applications

The PA231W is obviously aimed primarily at the professional market, so it's sensible to assume office applications could well form part of that day to day work. The 1920 x 1080 resolution and 23" screen size give a nice decent area in which to work although the vertical resolution is a little less than 16:10 aspect 24" models (1920 x 1200). I think you notice this if you come from a 16:10 format screen.

 

The screen offered a comfortable 0.265mm pixel pitch which delivered easy to read text at a nice size, in my opinion. The resolution is certainly big enough for side by side split screen working as well. No complaints here at all really. If you need a bigger resolution, you will need to look at bigger screens in the 27 - 30" range.

 

Default luminance of the screen is a little too low actually which is rare and so is comfortable for prolonged use. You may want to increase the brightness control a little up to around 60% for a luminance of ~120. There's no specific preset mode for 'text' or 'internet' so you will need to either calibrate one of the existing modes to a comfortable level, or perhaps set one of the programmable preset modes up how you like. The screen's auto-brightness (AmbiBright) control is useful I think for office work, allowing you to automatically control the brightness of the screen with changing ambient lighting conditions. A useful feature.

 

I tested the screen with both DVI and D-sub interfaces, and the DVI signal was a little sharper than VGA. You will want to use DVI for the sharpest text and image. The USB ports are handy for connecting external devices, although it would have maybe been handy to see more than 1 on the side of the screen for easy access. A card reader is featured on some other similar sized models, but not here. There is at least a very good range of easy-to-use ergonomic adjustments for obtaining the optimum viewing position as well.

 

Responsiveness and Gaming

The NEC PA231W 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 below show the best case example on the left hand side, and the worst case example on the right hand side. This should only be used as a rough guide to comparative responsiveness but is handy as a way of keeping a constant test of each screen.

23" 14ms ISO LG.Display e-IPS (note about G2G response time below)

23" 14ms LG.Display e-IPS

23" 14ms LG.Display e-IPS


23" 8ms G2G LG.Display e-IPS

 

You might note from the above that I've listed the PA231W as having a 14ms ISO response time as opposed to the 8ms G2G which is quoted in the manufacturers spec. This is because by default, the response time compensation (RTC) technology is turned down for this screen. If you enter into the advanced OSD menu there is an option for 'response improve', and I wanted to test it first of all when set to 'off'. It's not specified whether this option turns the RTC off altogether, but does seem to tone it down a fair amount. I would suspect that it does toggle the RTC on and off completely though from the performance seen.

With this set to 'off', the screen shows a fair degree of motion blur but actually not as bad as some non-overdriven models we have tested. While there is a noticeable blur, there is  not really any ghost image behind the moving car which is good. The PA231W is pretty comparable to the Viewsonic VP2365wb and NEC EA231WMi in this test, which use the same LG.Display e-IPS panel, but without any overdrive applied or available to select. This does indicate that with the response improve set to 'off', the RTC is not active.

The Dell U2311H is also included here. Again, this uses the same panel but has RTC enabled by default. This gives it a smoother image during motion and an obvious advantage with reduced motion blur. There is a slight pale trail behind the moving car as you can see in the Dell U2311H images, which relates to a slight overshoot of the RTC impulse.
 

  

For those who do want to game a bit more on the screen, NEC have allowed you to boost the RTC control via the advanced OSD menu. As shown above, there is an option for 'Response Improve', and you can simply turn it on and off. Let's see how it affects responsiveness in practice:

23" 14ms ISO LG.Display e-IPS (response improve = off)

23" 8ms G2G LG.Display e-IPS (response improve = on)

There are some significant and fairly noticeable improvements when this feature is enabled. The blurring is reduced quite a lot on the moving car which is good, and brings the screen in line with the Dell U2311H. NEC have done a good job applying the RTC impulse as there is no obvious overshoot and no dark or pale artefacts visible in this test. For gaming and any applications with fast moving images, I'd definitely recommend having this option enabled. To be honest, I can't see a reason not to have this enabled all the time.

 

 

23" 8ms G2G LG.Display e-IPS (response improve = on)


24" 8ms G2G LG.Display p-IPS (response improve = on)


27" 7ms G2G LG.Display p-IPS (response improve = on)

 

I thought it useful to compare the three NEC PA screens as well directly here, all with response improve activated. The technology seems to work the best on the 23" model, although it did help improve response times in practice on all three models. You can read our reviews of the  24" and 27" models for further analysis about the performance on those models.

 

 

23" 8ms G2G LG.Display e-IPS (response improve = on)

 

3ms G2G Samsung TN Film + 120Hz

I've provided a comparison above of the PA231W vs. our reference screen when it comes to this test, the Samsung 2233RZ. The SM2233RZ is a TN Film based 22" model with aggressive overdrive application, and with its 120Hz technology it is extremely fast and also shows very few RTC artefacts when in 120Hz mode. This also gives you a higher frame rate and smoother movement to the human eye.

The PA231W offers hardware level aspect ratio control. The options are available through the 'expansion' menu and there are options for 'full', 'aspect', 'off' and 'custom' available.

 

Input Lag

As usual I tested the screen in clone mode with a CRT to determine the level of input lag. This is something which can put off some gamers and is a delay between graphics card and monitor output. By hooking up a CRT you can show that  the LCD lags behind somewhat, which can affect users in some situations where they rely on the screen image being as fast as their inputs (e.g. fast FPS shooting games). Often, input lag is very low and probably wouldn't represent too much of a problem in real terms.

The input lag of the PA231W was very similar to that of the 24" and 27" models. Average lag was 28.1ms, with a maximum of 30ms recorded. In comparison, the PA241W had shown average lag of 26.9ms, and the PA271W 32.5ms. All 3 models are most likely using the same scalers and so this similar performance can be expected. The PA231W was behind the other three IPS based 23" models in this test - Dell U2311H (10.6ms), Viewsonic VP2365wb (16.3ms) and NEC EA231WMi (8.8ms). This PA screen is obviously not intended for gamers, but the professional market. Nevertheless we saw some good performance in our responsiveness tests, and an input lag of 28.1ms is not too severe. It should be fine for most casual gamers, but those wanting to play fast FPS or professional level games might find it too much.

 

Movies and Video

The following summarises the NEC PA231W's performance in video applications:

• 23" screen size makes it a reasonable option for an all-in-one multimedia screen, although larger screens are becoming more common place now and LCD TV sizes continue to grow

• 16:9 aspect ratio format is better suited to movies than a 16:10 screen. Black borders are smaller due to aspect ratio

• 1920 x 1080 resolution can support true 1080 HD resolution content (1920 x 1080)

• Digital interfaces support HDCP for any encrypted and protected content

• Fairly decent interface options available with 2x DVI (you can use HDMI > DVI if need be for digital video connection) and 1x D-sub. Also good to see DisplayPort available. Would have been good to see some dedicated HDMI ports though

• Excellent black depth and contrast ratio helping to ensure detail in darker scenes is not lost

• No multimedia or movie preset modes specifically although you can always use one of the programmable options to set up a profile you find suitable for movies (usually a little brighter and more vivid colours are preferred)

• No dynamic contrast ratio option available. Some people like that technology for movies and multimedia

• There is a Picture In Picture (PiP) and Picture By Picture (PbP) mode available via the OSD if you want to use it for displaying two devices at the same time alongside one another

• Good response time and input lag make it more than adequate for viewing fast moving images without obvious ghosting or severe blurring. I'd recommend having "response improve" activated certainly

• Panel luminance uniformity was excellent once ColorComp was enabled. However there was some noticeable backlight leakage from the four corners which could be distracting in darker movie scenes or where black borders are present. This may vary from one sample to another

• Wide viewing angles thanks to IPS panel technology making it suitable for viewing from different positions and for multiple viewers without issue

• Good range of ergonomic adjustments available making it easy to obtain a comfortable viewing position

 

Conclusion

The NEC PA231W lived up to our expectations really based on the reviews we had already carried out of the 24" and 27" models. Like its bigger brothers, colour critical applications and professional use is where this screen really comes into its own; and at the moment there is very little direct competition for it in the 23" sector when you consider these applications. The screen is very well set up out of the box, offering excellent gamma and colour accuracy along with some of the best blacks and contrast ratios we have seen. Once calibrated the screen performs even better, and with it's 3D 14-bit programmable LUT it really offers some professional advantages over some of the more mainstream models. The hardware calibration provides an extra level of performance, and we have tested the screen with both European and US versions of the SpectraView software, both returning very good results.

In other areas, responsiveness was actually very good thanks to the RTC application via the 'response improve' technology. Luminance uniformity was excellent once ColorComp was enabled, again showing this technology really works very well in the PA series. Unfortunately there was some backlight leakage evident from the corners in dark images / black backgrounds and so overall uniformity was not as good as it perhaps could have been. The 24" and 27" models definitely had the edge here.

Feature wise there is about everything you could need from a modern screen with good ergonomic adjustments, some nice extra features (AmbiBright, ColorComp) and a fairly decent choice of connections. This is perhaps missing a couple of HDMI interfaces I think though. The PA231W isn't readily available yet to buy in the UK, but those who do supply it seem to have it priced at around £575 GBP. In contrast the Dell U2311H is more like ~£250, the NEC EA231WMi is ~£300 and the ViewSonic VP2365wb is ~£200. There is an obvious price difference here, but then the same could be said for the 24" and 27" models within their respective sectors. It's a big price difference, but then this is a professional grade screen with the performance to match.
 

For full reviews of the NEC PA241W and NEC PA271W, please see here