Asus ML239H
Simon Baker, 14 June 2011

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There's been a fairly steady influx of new IPS based screens into the market over the last year or two, and the 23" sector is one area that manufacturers have not left out. Originally there were very few options available when IPS began to inflitrate what was a sector dominated by TN Film panels. The NEC EA231WMi was first of its kind and in December 2009 we carried out a full test of the screen. Later came the Dell U2311H, ViewSonic VP2365wb and the more professional grade NEC PA231W. For a while, these were the only real options in the 23" sector if you wanted an IPS screen. They all offered varying features and benefits of course and all proved popular with consumers.

More recently this year we have seen a definite trend in the market towards LED backlighting; or to use its proper name in the majority of cases - white-LED (W-LED) backlighting. In Febraury 2011 we tested the first 23" screen to combine an IPS panel with W-LED backlighting, in the form of the NEC EA232WMi, an update to their sucessful EA231WMi. Now manufacturers are getting on board with this trend and we are starting to see other models emerge offering 23" IPS panels and LED backlighting technology. There are models from Viewsonic, Fujitsu and LG being released and we have one from another manufacturer with us today. Asus are entering this sector with their ML239H model.

The ML239H is marketed on their website based on its IPS panel, with wide viewing angles and full HD support. The LED backlighting is also a selling point allowing them to promote the ultra-high dynamic contrast ratio and energy / planet saving characteristics. We will look at these elements later on in the review.

Specifications and Features

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

Monitor Specifications Table


23"WS (58.4cm)

Colour Depth

16.7m (6-bit + AFRC)

Aspect Ratio


Colour Gamut

~72% NTSC colour gamut (~sRGB)


1920 x 1080

Panel Coating

Anti-glare (matte)

Pixel Pitch



1x HDMI (HDCP), 1x D-sub

Response Time

5ms G2G (14ms ISO)

Design colour

Glossy black bezel and stand

Static Contrast Ratio



Tilt (+20 ~ -5) and swivel (20 +/-)

Dynamic Contrast Ratio


Special Features

6x 'Splendid' video presets



VESA Compatible


Viewing Angles


Physical Dimensions


Panel Technology



Net Weight (Est.): 3.9kg
Gross Weight (Est.): 6.1kg

Backlight Technology



VGA cable, Power adapter and cord, HDMI-to-DVI cable

The ML239H offers a single HDMI interface and a single D-sub interface at the rear of the screen. There is no DVI connection available here although the screen is packaged with a DVI to HDMI cable to connect to your PC. This will allow you to use the HDMI input as a digital connection. Oddly Asus do not package the screen with an HDMI to HDMI cable though which is a little strange when the screen is designed with HDMI in mind. There are no further video connections available such as (the increasingly popular) DisplayPort or connections sometimes used used by external devices like component or composite. You could potentially use the D-sub connection to connect your PC and leave yourself with the HDMI for an external multimedia device. Apart from that there is limited support for devices other than your PC. The digital interface (HDMI) is HDCP supported for any encrypted content.

There are no integrated USB ports on this model which is a bit of a shame as I think those are useful when you want to connect external devices like cameras and printers. There is an audio port which allows you to connect headphones (or speakers) to take the audio which is passed through the monitor when using the HDMI connection. This is only if you are using HDMI out from your PC or other device of course. There are no additional extras like card readers or speakers here.

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


Yes / No


Yes / No

Tilt adjust


Height adjust


Swivel adjust


Rotate adjust


VESA compatible


USB Ports


Card Reader

Audio connection

Ambient Light Sensor

HDCP Support

Touch Screen

Integrated Speakers

Design and Ergonomics

The ML239H comes in an all black coloured design with glossy plastics used for the bezel and stand. The bezel is 23mm wide along the sides and top, but as the image above shows, it is much wider at the bottom at 84mm.

Above: bottom left hand corner Asus logo (left) and OSD menu buttons (right). Click for larger versions

The bottom left hand corner has a shiny silver Asus logo and the top right has  HDMI written in smaller, less noticeable text.

Above: front views of the screen, click for larger versions

The OSD operational buttons and power on/off are located in the bottom right hand corner and are situated on the front of the screen as shown. The screen looks pretty attractive on the desk although the glossy bezel can pick up finger prints from time to time. The panel coating is a standard matte anti-glare (AG) coating. Some users complain about modern IPS panels having an overly aggressive coating. Personally I do not find the coating on this screen to be too bad but it can of course be subjective.

The back of the screen is almost completely enclosed in an attractive black glossy casing with a large Asus Logo in the middle. The back is pretty flat and helps to give the screen its very thin profile.

Above: rear and front views of the dual-ring stand. click for larger versions

There is a section where you can attach the stand which comes disconnected in the box. This is screwed simply into place without the need for a screwdriver.

Above: rear view showing the interface connections. Click for larger versions

In the bottom right hand corner (if looking at the screen from the back), there are the interface connections for HDMI and D-sub. There is a small connection to the left of these for the power cable. The screen features an external power brick so you need to use the packaged power supply and you cannot use a standard kettle lead power cable on this model. There is also an audio port for connecting headphones etc which will play back any sound being passed through the screen via the HDMI interface. This HDMI interface also supports HDCP.

From the side the ML239H has a very thin profile and it looks very sleek as a result. This ultra-thin profile is a result of the use of W-LED backlighting and the fact that they have made the power supply an external brick.

Above: side views showing maximum tilt range. Click for larger versions

The stand is packaged separately in two parts which screw easily together. This then screws into the back of the screen. The stand is formed of two glossy black plastic rings which Asus call their "Ring Stand with Ergo-Fit II Technology". When viewing the screen head on you can only see a semi-circle of the base sticking out in front of the screen and it looks pretty nice. However, this stand is a little limited in terms of ergonomic functionality unfortunately. There is a tilt function available and although it is smooth to operate, its range is not huge. It tilts a little towards you and a reasonable amount backwards. I found the range sufficient to obtain a comfortable working angle. The side to side swivel is smooth and easy to use.

The one main draw back though from this stand is that there is no height adjustment. I can live without rotation functions to switch between landscaping and portrait modes, but I think it's a shame when a screen is missing a height adjustable stand. As it is, the screen sits low to the desk with a gap of ~35mm from the desk to the bottom of the bezel when the screen is up-right.

A summary of the screens ergonomic adjustments is shown below:




Ease of Use


(+20 ~ -5)








20 +/-








Smooth operation but lacking height and rotate adjustments

Overall the screen actually won a 'Good Design' award for its ultra-slim profile and aesthetics. The build quality feels good and the plastics are of a decent quality. The screen itself is quite light due to its thin profile but it remains sturdy on the desk. There is a bit of a wobble as you make adjustments to the viewing position but again only because it is thin and light. There is a very faint high pitch noise from the screen if you listen very closely. You wouldn't notice this in normal use and you'd have to press your ear up to the top of the screen to really pick it up.


OSD Menu

Above: OSD operational buttons during normal use, not lit up

The OSD operational buttons for the screen are located in the bottom right hand corner. They are all touch sensitive buttons and so during normal operation they are only marked by a small white circle as shown above. Even the power button is touch sensitive and has a fairly subtle white glow when in operation. This pulsates when the screen is in standby mode.

Above: OSD operational buttons when in use, with labels lit up

If you press any of the circles the labels for the buttons light up as shown above. Of course in pressing a button to make them light up you also carry out that buttons operation which can be a little annoying, especially if you press the input switch button to bring up the labels and the screen then switches between VGA and HDMI. It's a shame these aren't sensitive to when you hover over them like on the Dell U2410 for instance. Having said that the touch sensitive nature is a nice feature and they are clearly labelled once the lights are activated. The buttons provide quick access to the preset modes (S/A button), contrast, brightness and input selection. The middle button allows you to access the main OSD menu. These buttons were easy enough to use although sometimes not as responsive to the touch as you might like.

The menu itself is reasonable although not as intuitive to navigate as some other screens we have used. For instance it might have been easier to have the up and down arrows next to one another perhaps? There are five sections listed along the left hand side and the sub-sections are listed along the right hand side. You can use the up/down arrow buttons to navigate through this of course. The first section lists all the 'Splendid' preset modes available from the screen as shown above. There are 6 options available which are all independently configurable.

The color menu allows you to change the contrast, brightness and colour settings. The colour temp > user mode also then allows you to change the individual RGB levels from within it which is useful for calibration.

The image section gives you access to a few other features. The 'Trace Free' option allows you to control the level of overdrive applied to the crystals to boost response times. We will test this function later on. There is also a section for aspect ratio control and the dynamic contrast ratio.

The input select section allows you to switch between VGA and HDMI. You can also do this more quickly using the right end quick launch OSD button.

The system setup menu allows you to control things like the language and also you can turn the 'ECO mode' on and off here.

You can access the screens factory menu by holding the 'menu' button down while you turn the screen on, and then pressing 'menu' again. This confirms, amongst other details, the screen is using a panel from LG.Display. This is their LM230WF3 panel which is also used in the other 23" IPS + W-LED screens we discussed earlier, including the NEC EA232WMi


Power Consumption

In terms of power consumption the manufacturers spec states usage of less than 40W in normal operation and <0.5W in standby / off mode. There is also an 'ECO mode' function available in the OSD menu whcih reportedly allows you to "further reduce energy consumption to 55% for a greener life style".


Power Usage (W)

Factory Default




ECO Mode On




We tested this ourselves and found that out of the box the screen used a slightly lower 37.1W of power. After calibration, where we had adjusted the brightness control and therefore the backlight intensity, this was reduced to 25.9W. In standby the screen uses only 1.3W of power. We tested the ECO mode which seemed to actually increase the power consumption back to the standard consumption. It reverted our manual 30% brightness setting back to a brighter setting, although the option was now greyed out in the OSD. This ECO mode doesn't appear to offer much or is perhaps set up wrongly? A calibrated state with manual adjustment of the brightness control would be most appropriate. There will always be a compromise between luminance and power consumption anyway.

As well as the power saving of W-LED backlighting Asus are also promoting its environmentally friendly components. This includes a mercury-free LED-backlit panel, corrugated cardboard packaging with at least 80% recycled content and slim-flat packaging which allows more cartons to be fitted per cargo, reducing transportation costs and CO2 emission.

Colour Accuracy, Black Depth and Contrast

The Panel and Backlighting Unit

The Asus ML239H utilises an LG.Display LM230WF3-SLB1 e-IPS panel which is capable of producing 16.7 million colours. The panel itself actually uses a 6-bit colour depth with frame rate control (A-FRC) to produce the 16.7m colours. This is different to regular 8-bit IPS matrices, but this is likely a measure taken to achieve a lower price point for these modern lower-cost displays. Studying detailed information from LG.Display's datasheet confirms the panel is indeed 6-bit+AFRC.

The ML239H uses White-LED (W-LED) backlighting. The colour space of this screen is approximately equal to the sRGB reference (and around 72% NTSC) and the screen is therefore classifed as a standard gamut model.

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 with the black triangle representing the display

  • 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:

Monitor OSD Option

Default Settings





Color Temp

User Mode

RGB Controls

100, 100, 100

Splendid Preset

Standard Mode

Asus ML239H - Default Factory Settings


Default Settings

luminance (cd/m2)


Black Point (cd/m2)


Contrast Ratio



The out of the box performance of the ML239H was fairly good. 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 blues and greens and is a little short in red shades, but not by much at all. Default gamma was recorded at 2.1 average, leaving it 6% out from the target of 2.2. White point was very close to the target though at 6375k (2% deviance) which shows a good factory set up in this area.


Luminance was recorded at a high 223 cd/m2 which is perhaps not surprising given that the screen is set at 100% brightness by default. This should be easy enough to adjust later during our calibration. Even at this high 223 cd/m2 luminance, the black depth was a very good 0.28 cd/m2. This gave us a static contrast ratio of 803:1 which is good for an IPS panel.


Colour accuracy was moderate at default factory settings with an average dE of 2.3, ranging up to a maximum of 4.8. The screen felt quite even to the naked eye although overly bright at these default settings. This factory set up will probably be fine for casual users as long as you turn the brightness control down to around 30% to reach a more comfortable luminance.



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.

Asus ML239H - Calibrated Settings

Monitor OSD Option

Adjusted Setting





Color Temp

User Mode

RGB Controls

100, 92, 99

Splendid Preset

Standard Mode


Calibrated Settings

luminance (cd/m2)


Black Point (cd/m2)


Contrast Ratio



I remained in the standard mode preset for this process and this meant that I could adjust the RGB controls from within the OSD menu. 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 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. Gamma had been corrected now to the target of 2.2 and white point was basically spot on at 6513k. 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 good at 0.16 cd/m2 and this gave us a reasonable calibrated static contrast ratio of 749:1 Colour accuracy was also improved nicely with dE average now 0.3 and maximum only 0.8. LaCie would consider colour fidelity to be excellent.


Testing the screen with various colour gradients showed very smooth transitions with no sign of any colour banding. There was some slight gradation evident in darker tones but overall no issues. There was also some 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 to be honest, 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 is available in our ICC profile database.



Calibration Performance Comparisons



I've provided a comparison above of the ML239H against some of the other screens we have tested in a similar size range. Out of the box average dE was 2.3 on the ML239H which was mediocre. It was better than the BenQ EW2420. That model used one of AU Optronics' newest AMVA panels with W-LED backlighting. Default colour accuracy of the EW2420 was worse at 4.8. The default colour accuracy of the ML239H was comparable to some of the other 23" IPS models we have tested, including the Dell U2311H (2.4), NEC EA231WMi (2.7) and Viewsonic VP2365wb (2.5) which was pleasing. The other 23" IPS + W-LED screen we have tested is the NEC EA232WMi and it is using the same panel as the ML239H. It was very close as well at 2.4 dE average. The professional grade 23" NEC PA231W was better still at 1.3 dE average. A reasonable performance in terms of default colour accuracy from the Asus ML239H and in keeping with the competition.



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 real difference here. Some of the professional range models from NEC are even more accurate. Professional grade monitors like the NEC PA series 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 ML239H were reasonable for an IPS panel. Calibrated black depth was 0.16 which was very close to the other 23" IPS screens we have tested (ranging between 0.13 and 0.17). The NEC EA232WMi is the closest rival to the Asus ML239H and had a slight better calibrated black depth of 0.13. Contrast ratio was a decent enough 749:1 but it was a little behind the others in this regard. The NEC EA232WMi again was better with a 933:1 static contrast ratio thanks to its lower black point. The BenQ EW2420 and Samsung F2380 with their AMVA and cPVA panels offered some fantastic contrast ratios of ~3000:1 which IPS cannot compete with at the moment.




Contrast Stability

I wanted to see how much variance there was in the screens contrast as we adjusted the monitor setting for brightness. In theory, brightness and contrast are two independent parameters, and good contrast is a requirement regardless of the brightness adjustment. Unfortunately, such is not always the case in practice. We recorded the screens luminance and black depth at various OSD brightness settings, and calculated the contrast ratio from there. Graphics card settings were left at default with no ICC profile or calibration active. Tests were made using an NEC branded and customised X-rite i1 Display 2 colorimeter. It should be noted that we used the BasICColor calibration software here to record these, and so luminance at default settings may vary a little from the LaCie Blue Eye Pro report.

OSD Brightness


Black Point (cd/m2)

Contrast Ratio
( x:1)














































Luminance Adjustment Range =  127 cd/m2

Black Point Adjustment Range =  0.16 cd/m2

Average Contrast Ratio = 791:1

The luminance range of the screen was moderate at the top end although not as high as some modern screens. At 100% brightness control, the screen was able to offer a maximum luminance of 217 cd/m2 which is a little way off the advertised 250 cd/m2. You have a decent enough range to work with at the lower end as you can adjust the backlight down to achieve a low luminance of around 90 cd/m2. A setting of around 25 - 30% at default settings should return a luminance of around 120 cd/m2 for comfortable day to day use in normal lighting conditions. If you carry out further calibration or adjustments of contrast or the individual RGB channels this of course may vary. The range of adjustments was not as great as on some other screens with a fairly high minimum brightness setting. However, this should be fine for most users anyway. We have plotted the luminance trend on the graph below. The screen behaves as it should, with a reduction in the backlight intensity controlled by the reduction in the OSD brightness setting.

Black depth was reasonable across the whole range, being between 0.27 and 0.11 cd/m2. This was reasonable for an IPS panel but a little behind some other competing (IPS based) models. This could also not compete with the modern AMVA and cPVA panels that we have seen. Contrast remained stable across the range with an average static figure of 791:1 recorded based on a default uncalibrated state. These contrast measurements were plotted on the graph shown below:


Dynamic Contrast

The Asus ML239H features a dynamic contrast ratio (DCR) control, which boasts a spec of 50,000,000:1 (50 million:1). Asus refer to this technology as ASCR which stands for 'Asus Smart Contrast Ratio'.

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 descreased. 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 only available in certain preset modes from the 'Splendid' menu. It is available when using the theater, game, night view and scenery modes. The option is greyed out in the other preset modes. If you enable ASCR when in any of these presets, the brightness control becomes greyed out.


ASCR Dynamic Contrast

Available in Presets

Theater, game, night view, scenery


On / Off

Max luminance (cd/m2)


Min Black Point (cd/m2)


Max Dynamic Contrast Ratio


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. Carrying out the tests in this way does give you a good indication of the screens dynamic contrast ratio in real life situations however. Carrying out this test didn't seem to make use of the DCR much at all. There was a perhaps a very slight change in the screens brightness as you switched between the extremes of an almost completely black screen and an almost completely white screen. However, it was very minimal. In fact our colorimeter recorded maximum luminance as 199 cd/m2 and minimum black depth as 0.25 cd/m2. This only gave us a static contrast ratio of 794:1 which was no better than our uncalibrated default measurements of the screen. It seemed like this function made little to no difference in practice. Again testing this feature during several movie and video clips showed no real variation in the backlight during changes in the scenes.

However, the feature can work, but only in the most unrealistic and extreme circumstances. If you display an all black screen (completely black) then the feature "works". You can watch this by bringing up the OSD menu when viewing an all black screen and in fact the screen goes so dark that it seems to turn the backlight off completely after a couple of seconds. You can see the fading of the OSD menu is smooth but after an initial delay of about a second the transition is very fast and the OSD then disappears completely! Switching back to a background which is not 100% black brings it back up instantly. So the technology appears to be switching the backlight off completely which would account for the ridiculously high DCR of 50 million:1. In the right lab settings you can achieve this DCR (in fact its tending towards infinity:1 if you consider its black point is basically the backlight turned off = 0 cd/m2.). However, in practice you are never going to be able to see a DCR range like that. In fact in normal use the DCR doesn't seem to operate at all. Another marketing gimmick.


Viewing Angles

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

Viewing angles of the Asus ML239H 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. Vertically, the contrast shift was a little more pronounced but the fields of view were still very 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.

On a black image there is a fairly noticeable purple hue when viewed from an angle but there is no obvious white glow that you can see from some modern IPS panels. There is no A-TW polarizer on this panel which is rarely used now in the market.

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 ML239H sample was pretty good overall. The maximum deviations from the central measurement of 120 cd/m2 were as low as 109 cd/m2 along the left hand edge and up to the highest measurement of 129 cd/m2 along the middle top area. Overall the whole screen was within 10% deviance from the target however which was good and 54% of it was measured within 5% deviance. The upeer part of the screen was a little brighter than the bottom half but you couldn't spot this in normal use.

Backlight Leakage

Above: All black screen in a darkened room

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 we had seen promising things from the luminance uniformity of the screen there was unfortunately some rather obvious backlight bleed from the panel, mostly along the bottom edge. This was easy to see with the naked eye and could pose a problem for people who want to use the screen in dimly lit conditions. Since the W-LED unit is positioned along the bottom edge of the panel, this is where the leakage is most apparent. In normal day to day use you can't see this leakage but if you were planning to use the screen with dark images in dark conditions, then this could present a problem.


General and Office Applications

The 23" screen size and high 1920 x 1080 resolution were very pleasant for office working, and although you do lose a bit of height vertically compared with a 1920 x 1200 screen, it was nothing too bad. Image quality was very crisp and sharp using the DVI interface, and although D-sub (VGA) was also very good, it was not quite as sharp on text I didn't think. The 0.265 mm pixel pitch was slightly smaller than a 23.6" 1920 x 1080 screen of course (0.2715 mm) and 24" 1920 x 1080 screen (0.276 mm), and so text size felt about right for every day use.

Default luminance of the screen was too high for prolonged office use, although even at 100% brightness control it did not reach anything too blinding with a maximum luminance of 217 cd/m2 being recorded. For comfortable use in normal lighting conditions a setting of around 25 - 30% should return you a luminance of ~120 cd/m2. Although there was a decent range of preset modes, there were none specifically aimed at office, text or internet use. You will probably want to set up your standard preset for normal office work and at least there are others available for gaming and multimedia.

The ergonomics of the screen were a little limited sadly. The special ring stand did offer a reasonable range of tilt and a decent swivel adjustment. However there was no height adjustment available and so the screen does sit quite low to the desk. There is also no option to rotate the screen into portrait mode which some people might like for office document viewing. It was also a bit of a shame not to see some USB ports available and there are no extra features like ambient light sensors, integrated speakers and card readers which are often useful in office environments. These have been left off to keep production and retail costs down.


Above: photo of text at 1920 x 1080 (top) and 1680 x 1050 (bottom)

The screen is designed to run at its native resolution of 1920 x 1080 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 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 noticeably more blurry although not unusable. There is some overlapping of the text across sub-pixels as you can see in the photo which results in this blurring. Native resolution is recommended where possible.


Responsiveness and Gaming

Response Time Control

Above: OSD menu showing the response time 'Trace Free' option in the 'image' menu

Before we get into the side by side screen comparisons I wanted to talk about the response time settings available from the ML239H. This function allows you to control the responsiveness of the panel in games and fast moving images. Being rated with a 5ms G2G response time, the e-IPS panel uses response time compensation (RTC) technology to boost pixel response times and improve responsiveness in practice. The panel itself (LG.Display LM230WF3) has a 14ms ISO response time (black > white > black) on paper but with an overdrive circuit applied the grey to grey transitions are improved. This RTC impulse is applied to speed up the pixel transitions which can help reduce motion blur and ghosting. Asus have allowed you to control the level of RTC impulse applied to the panel through their OSD, and through the 'Trace Free' option. We saw this same feature when we tested the Asus MS246H before and it proved useful. The Trace Free options are available in steps of 20, from 0 to 100. The higher the setting, the higher the level of RTC being applied to the liquid crystals. In theory this should boost response times, but let's see how it impacts real life performance.

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 below show the best case example from each of the 6 trace free settings. 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:

Above: side by side comparison of pixel responsiveness in all 'Trace Free' modes

As you can see, there was certainly a variation in responsiveness as you changed the trace free setting. You could observe this easily with the naked eye as you switched between the different levels. The blurring and ghosting of the moving car improved as you increased the setting from 0 up to 40. At a setting of 40 there was very little ghosting evident at all and although there was still some motion blur it was not too bad. Unfortunately as you increased the trace free setting further above 40, the performance was adversely affected. At a setting of 60, a more pronounced blur was introduced as compared with 40. This was at a similar level to the 20 setting. When you reached 80 the blurring was improved again a little, but there was a slight RTC overshoot introduced. The RTC error was too high at this level and it resulted in a pale shadow behind the moving car. At a setting of 100 this RTC overshoot was exagerated even more producing a rather obvious and distracting pale and dark trail behind the moving car.

So it seems that the optimum trace free setting on the ML239H is 40, where there is minimal motion blur and ghosting, and no noticeable RTC overshoot. Anything above this and the RTC impulse is applied too aggressively and it results in an unfortunate overshoot due to its poor control.


Display Comparisons

The screen was tested again using PixePerAn and this time compared with the results we had obtained from other competing screens. 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" 5ms G2G LG.Display e-IPS (W-LED) - Trace Free setting 40

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

23" 14ms LG.Display e-IPS

23" 14ms LG.Display e-IPS

I have first provided a comparison of the Asus ML239H against three other competing 23" e-IPS models. From the test images above you will see that the ML239H performs better than the NEC EA232WMi, NEC EA231WMi and Viewsonic VP2365wb models. Those screens are all e-IPS based as well, but with a quoted 14ms ISO response time figure. They do not use response time compensation technologies to boost pixel responsiveness and so show a fair degree of motion blur even in the best case images. The Asus ML239H uses the same LG.Display LM230WF3 panel as the NEC EA232WMi tested here, but unlike any of these other 3 models, the Asus uses a RTC circuit to improve response times and reduce the quoted figure to 5ms G2G. In practice this has a marked benefit with a reduced motion blur and improved performance.

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

23" 8ms G2G LG.Display e-IPS

The Dell U2311H is e-IPS based as well but uses a slightly different panel (LM230WF2) to the Asus. Like the Asus, it also uses RTC technology to boost pixel transitions and is quoted with an 8ms G2G response time figure. It also shows much less motion blur than the non-overdriven models and a comparable performance to the ML239H. There is a very slight RTC overshoot evident on the U2311H in the form of a slightly pale halo behind the car, but this is nothing too severe. In practice there is perhaps a slight improvement in motion on the Dell but it is minute, and at the cost of a very slight overshoot of the RTC impulse. The Asus is a good alternative in the 23" IPS sector for gamers.


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

23" 8ms G2G Samsung cPVA (Response Time setting = Fastest)

24" 8ms G2G AU Optronics AMVA (W-LED)

24" 6ms G2G LG.Display H-IPS

24" 5ms G2G LG.Display e-IPS

I've also provided some comparisons of the ML239H against some of the popular and recent 24" models in the market we have tested. As you can see, the ML239H is a lot faster than the AMVA based BenQ EW2420, which to be quite honest, did not perform very well in this test. It is also faster than the cPVA based Samsung F2380 we tested recently. The Dell U2410 and HP ZR24W both use RTC and so their performance was better and much more like the performance of the Asus ML239H.

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

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

22" 3ms G2G Samsung TN Film + 120Hz

I've also included a comparison above against two gamer-orientated screens, both featuring heavily overdriven TN Film panels, and 120Hz technology. The pixel responsiveness of both of these is a little ahead of the ML239H, and the 120Hz frequency allows for improved 120fps frame rates and the support of 3D content as well. The BenQ XL2410T does show some rather noticeable RTC overshoot in the form of dark trails behind the moving image (speech bubble and head) which is unfortunate, and a sign that the RTC impulse is too aggressive. The Samsung 2233RZ remains our champion in this test.

The Asus ML239H was pleasing in these tests overall. The trace free option allows a good range of control over the level of RTC applied to the panel, although a setting of 40 does seem optimum in our tests. The performance was very comparable to the other IPS screens which have been impressive in these tests, namely models like the Dell U2311H and Dell U2410. The Asus also holds the edge over the non-overdriven IPS models in the 23" market so provides a good option for those wanting an IPS screen which is capable of a decent level of gaming.

Additonal Gamng Features

Apsect Ratio Control - The ML239H supports aspect ratio control options through the OSD 'image' menu. There are options for full, 4:3 and overscan (only available when using HDMI). Complete 1:1 pixel mapping is lacking here.

Preset Modes - There is a 'game' preset mode available in the Splendid preset section for those who want to set up a preset based on their requirements. This boosted the brightness setting to 80% and made the colours a little more vivid. You can change the brightness and other settings within the preset and so save a different setup for each preset if you want which is good. The dynamic contrast ratio is also available in this preset although we have already seen that this does little to nothing in real use.


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 ML239H showed a reasonably low level of input lag with an average lag of 15 ms, and a maximum of 20 ms. This was a little higher than some of the other 23" IPS models like the NEC EA232WMi (8.1 ms) and Dell U2311H (10.6 ms) for instance. It was similar to the ViewSonic VP2365wb at 16.3ms though. Overall this was a sufficiently low input lag and should not represent any real problems in practice.


Movies and Video

 The following summarises the screens performance in video applications:

  • 23" 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

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

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

  • Digital interface (HDMI) supports HDCP for any encrypted and protected content

  • Limited interface options available with 1x D-sub and 1x HDMI only. Would have been useful to feature a separate DVI for PC connection or DisplayPort for connecting external devices. Good to see HDMI available however.

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

  • Dynamic contrast ratio is available but does little to nothing in practice unfortunately.

  • 'Theater' preset mode is available from the Splendid preset menu. This boosted the colours and made them more vivid and cartoony. Might be useful if you want to set up a separate preset how you want for movie viewing and keep the 'standard' preset available and set up for normal PC use.

  • Good pixel responsiveness which should be able to handle fast moving scenes in movies without issue. I would recommend using the 40 setting in the trace free section of the OSD menu.

  • 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.

  • Limited ergonomic adjustments available sadly from the stand. Tilt and swivel are at least present and offer a decent enough range of adjustments. Height adjustment would have been handy.

  • Some noticeable backlight leakage along the bottom edge of the panel which was unfortunate. This type of leakage has the potential to become distracting when watching movies, especially where black borders are present.

  • No intergrated stereo speakers on this model. There is a headphone audio jack on the back of the screen for audio passed through when using the HDMI connection end to end.



It's always interesting to take a look at a new IPS screen entering the market and Asus have done a good job here I think with the ML239H. Asus aren't traditionally a big player in the monitor market but are starting to release a few new models with interesting features and specs, and using the ever-popular IPS panel technology. The ML239H offers a good spec and a reasonable range of features and options for the price.

Performance wise the screen was impressive in most cases. Colour accuracy and default set up were pretty good and should be adequate for most casual users out of the box. The black depth and contrast ratio are good for an IPS panel although not quite as good as a couple of other similar screens. Once calibrated the screen offered very reliable performance as you would hope. Viewing angles were wide thanks to the IPS panel and its use for office applications was pleasing. One area which might separate this model from its competitors is its pixel responsiveness. Thanks to the addition of an overdrive impulse the responsiveness is very good at the right settings and is comparable to the popular Dell U2311H. These two are a step apart from the other non-overdriven IPS panels we have discussed here so this screen would probably be a good choice for someone wanting to game on their new screen. This is combined with a low input lag as well which is pleasing.

There are a couple of areas of disappointment however. The dynamic contrast is useless it seems in real life situations but to be honest, it's rare to find a DCR which works well or is practically useful. There was also a bit of backlight leakage which was a shame and quite noticeable, although this can of course vary depending on stock, manufacturing lines and other factors. It's good to see HDMI included but it would have been nice to offer DVI as well. Height adjustment is notable by its absence, but the rest of the ergonomic adjustments are decent and smooth and easy to use.

The ML239H is priced at around 180 GBP (inc VAT) which makes it very competitively priced compared with popular 23" IPS models like the Dell U2311H (230) and NEC EA232WMi (250) for instance. If you don't need a couple of the extra features of those models then this is certainly a good alternative and should offer some very good all round performance for a reduced price.



Good pixel responsiveness and low input lag

Useless dynamic contrast ratio in practice

Decent colour accuracy, white point, black depth and contrast even out of the box

Some backlight leakage (may vary)

Competitive price point in 23" IPS market

Missing height adjustment stand and DVI input


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Further reading: TestFreaks



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