Introduction

It's not every day that a new panel technology is introduced to the market, and the desktop monitor sector has long been dominated by TN Film and more recently IPS and VA matrices. You can therefore imagine the interest from enthusiasts when a new technology is launched and the first screens using it start to become available. It was back in December 2010 that we first heard about Samsung's new panel technology, a step away from their long-standing Patterned Vertical Alignment (PVA) and an answer (they claim) to the success and popularity of LG.Display's In Plane Switching (IPS). Samsung's new "Plane to Line Switching" (PLS) technology was born, and the public waited patiently for the arrival of some new displays featuring it.

Pieces of information started to appear during 2011 and in February we heard the news about their planned first monitor to use this technology, the so-called 27" SA850 monitor. Following that in April we brought you details of two desktop monitor panels in sizes of 24" and 27" which provided us more insight into the module which would be used in the SA850 screen we'd already heard bits and pieces about. Later that month some photos emerged of the new screen before the first pre-production review was released by fcenter.ru (and later translated onto the English X-bit Labs.com site). We finally had some information about the new screen, known by its full name as the S27A850D, and the interesting PLS panel technology, even if it was only based on a pre-production sample and not a final version. We also found out in July 2011 that Samsung would be releasing a 24" model with PLS technology, the S24A850DW.

We now have the S27A850D screen with us for thorough testing and to investigate how this new PLS technology performs. As well as the interesting arrival of PLS, the S27A850D offers a large 27" screen size, 2560 x 1440 resolution and a good array of functions, features and connections. Samsung market the screen as a professional business grade screen, and it is designed to compete with 27" IPS offerings like the Dell U2711, HP ZR2740w and NEC PA271W for instance.

Samsung's website describes the S27A850D as follows: "The Samsung Business Monitor SA850 is the perfect choice for professional businesses that are looking to increase overall operational efficiencies while boosting the performance and productivity of employees. These high-performance monitors are specially designed for working under extremely demanding conditions while providing its users with ergonomic features that will reduce fatigue. The new line up is also a born multi-tasker and can run more efficiently with lower power consumption. So whether you�re in professional services, financial industry, or higher education, our new SA850 will transform the way you and your employees conduct business."

 

Specifications and Features

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

The S27A850D offers a fairly limited range of different connections which is presumably down to the native resolution of the screen and the support of this from different connection types. There are 2x Dual-link DVI and 1x DisplayPort available here which are all capable of carrying the full 2560 x 1440 resolution. There are no D-sub or HDMI interfaces available and these may have been left off since they are unable to support the full native resolution. However, it would still have been useful to include them I think for connecting external devices where the image could then be interpolated. Samsung do not list in their spec or manual whether the digital connections are HDCP certified for encrypted content. On checking in the NVIDIA graphics card control panel it confirms the display is HDCP ready though. The screen is packaged with the cables for DL-DVI but sadly there is no DisplayPort cable provided.

Samsung have included a 3 port USB 3.0 hub which is useful, and nice to see the use of the latest, fastest generation of USB here. There is also an ambient light sensor for automatic adjustment of the backlight, depending on working environment conditions. Samsung have also added an ECO motion sensor (human detector) as part of their ECO power saving options which can turn the screen on and off when it detects a user in front of it.

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

OSD Menu

Above: view of OSD operational buttons. Click for larger version

The OSD operational buttons are situated on the front of the screen in the middle of the lower bezel. Rather than fully defined individual buttons, they are like small "teeth" and operate quite nicely. There is quick access from these buttons to the ECO menu (more in a moment on that), brightness control, input selection and Picture by Picture (PbP) setup. To the right of these is the power on/off button and a small blue power LED. This flashes blue on and off when the screen is in standby.

Pressing the 'menu' button brings up the main OSD menu. This is divided into 5 main sections which are listed down the left hand side of the menu as shown above. To the right there is an indication of the options available if you were to enter each section.

The picture menu contains some standard controls for brightness, contrast and sharpness. There is also access to a further sub-section labelled "MAGIC", and a further option to control the 'Response time'. We will test that option later on in the review.

Within the 'MAGIC' sub-section there are options for MagicBright and MagicColor. The MagicBright section contains a series of preset modes for different use. You can also activate the dynamic contrast ratio preset mode in here. The MagicColor section is also available and according to the manual it "is a new picture-quality improvement technology developed independently by Samsung, which delivers vivid natural colors without picture quality degradation." There is an option for 'full' which is designed to obtain a vivid picture quality for all areas including the flesh colours in the picture. The 'intelligent' option improves the chroma for all areas except the flesh colours in the picture. A 'demo' mode splits the screen vertically so you can see the before and after image to compare what the feature is doing for your content.

The 'Color' section of the menu allows you access to the RGB channels where you can change each individually. There are also a series of colour tone presets available with options for cool, normal, warm and custom modes as shown. The Gamma option gives you access to 3 preset gamma modes which we will test a little later on.

The 'size & position' section allows you to control the Picture By Picture setup. There is also an option for 'image size' which controls the hardware level aspect ratio control. There are options here for 'auto' and 'wide'.

The 'setup & reset' section gives you access to the ECO sub-menu where you can set the ECO motion sensor and ECO light sensor on or off. Back in the main section you can control things such as language, source selection etc.

The 'information' section confirms the connection being used is digital, along with your resolution and refresh rate.

You can also access the screens factory menu if you want, although it doesn't really tell you anything particularly useful or allow you to control anything much further. If you are curious you can access the menu as follows. Use this section at your own risk!:

Access: Set brightness and contrast to 0. Press �Menu� button and then press �Source� button for 5 sec.
Return: Turn off and turn on power.
 

All in all the OSD menu was pretty easy and intuitive to use. The up / down arrows allow you to easily navigate between sections and you can go back and forth into each option without problem. There did seem to be a lot of sections within sections but overall a good range of options and adjustments available.

 

Power Consumption

The Samsung S27A850D offers a pretty decent range of options and features designed to help reduce monitor power consumption and save energy (and trees!). The use of W-LED is a start as it is a backlighting technology which can help reduce power usage compared with CCFL units.

An ambient light sensor is provided which can detect your lighting conditions and automatically adjust the backlight level accordingly. This is quite a nice useful function if your working environment has variable lighting. Samsung's website states: "Save electricity and hassle with Samsung�s Eco light sensor. By adjusting screen brightness to match your surrounding environment, the SA850�s Eco light sensor creates a brilliant visual display while also minimizing your energy consumption. You will benefit from a more comfortable viewing experience that is far better for the environment. Monitor brightness is adjusted to match your ambient light, which ensures that the screen is highly visible and appropriately set for your eyes. So, in a dark room the screen will reduce brightness, but when sitting in a room with plenty of light, it will increase brightness. The Eco light sensor is simply perfect for modern living - helping you conserve energy and keep comfortable."

There is a specific ECO menu provided within the OSD menu where several options are available including this Ambient light sensor.

The ECO menu has a little graphic of a tree with various levels of growth as shown above. This is designed to give you a quick graphical representation of the energy (and therefore trees) you have supposedly helped save using the various ECO features. Samsung's website says: "Take the guess work out of eco savings with Samsung�s new Energy Tree feature. For the first time, you can now know exactly how much energy you are saving through your eco modes such as the Eco light sensor and the Eco motion sensor. Through an intuitive energy saving status, which can be displayed either intuitively or graphically, you can keep tabs on your efforts to make the world a better place."

The menu also has an option titled 'ECO saving'. "Eco saving makes saving energy easy, it adjusts the brightness of your Samsung monitor based on how much energy you want to save. And with the choice of three energy saving modes (50%, 25% and Power Saving off), you can really tailor your monitor use to meet your own personal needs. Samsung�s commitment to saving energy is designed to help both you and the environment, and with up to 50% saving on consumption, you can really make a positive impact on your eco footprint. Take the effort out of saving energy and take control with Eco saving." The 25% saving option is actually labelled as "75%" in the menu, meaning it is designed to run at 75% brightness / power.

The ECO motion sensor is a feature designed to switch the screen off when it detects no movement in front of it for a specified period of time. This could be quite useful in an office environment particularly if you need to leave your desk frequently. You can also control whether the backlight is just dimmed, or completely turned off when no movement is detected.

In terms of power consumption the manufacturers spec states typical usage of 69W and 71W maximum. In standby the screen apparently uses <1W, around 0.4W according to some of their international sites.

We tested this ourselves and found that out of the box the screen used 52.7W of power while at its default brightness setting which was 100%. The additional power usage specified would be related to the draw on the USB ports if devices were connected. At the lowest brightness setting, power consumption was reduced to 24.5W and after calibration, where brightness was set to 17% we had measured a power consumption of 29.1W. In standby the screen used 1.0W of power.

I also tested the ECO saving settings to see if they did return a power saving as advertised. Compared with default settings they did perform as they should, in fact offering a slightly higher percentage saving in each mode.

I have plotted the results of these measurements on the graph below:

 

Colour Accuracy, Black Depth and Contrast

The Panel and Backlighting Unit

The Samsung S27A850D utilises a Samsung LTM270DL02 PLS panel which is capable of producing 16.7 million colours with a true 8-bit colour depth. The S27A850D uses White-LED (W-LED) backlighting. The colour space of this screen is approximately equal to the sRGB reference and is considered a 'standard gamut' backlight type. The screen covers 81% of the NTSC reference, 78.1% of the Adobe RGB reference and 99.5% of the sRGB space. A wide gamut screen would need to be considered by those wanting to work outside of the sRGB colour space of course.

Above: PLS pixel structure. Image courtesy of X-bitlabs.com

I wanted to briefly look at the pixel structure of the new PLS panel technology being used here. PLS is a new panel type being produced and manufactured by Samsung. It is a move away from their long-standing PVA technology and is designed as a direct competition to LG.Display's increasingly popular and successful IPS technology. Indeed the new "Plane to Line Switching" (PLS) name is very close to the "In Plane Switching" (IPS) name which has been around for a long time now. The above image is a macro photograph taken of the pixel structure (image courtesy of X-bitlabs.com). This structure is quite similar to modern e-IPS panels. The sub-pixels have the same rectangular shape with a barely visible black line in the middle as e-IPS panels. It is a little hard to discern the details because of the monitor�s antiglare (AG) coating which, coupled with the small pixel pitch (0.233 mm), made photographing difficult. The sub-pixels of this PLS matrix keep on glowing as a single whole at reduced brightness levels. We will look in to the performance characteristics of the PLS matrix throughout this review.

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 (not to be confused with the new i1 Display Pro colorimeter) combined with LaCie's Blue Eye Pro software suite. An NEC branded and customised X-rite i1 Display 2 colorimeter was also used to verify the black point and contrast ratio since the i1 Pro is less reliable at the darker end.

Targets for these tests are as follows:

• CIE Diagram - validates the colour space covered by the monitors backlighting in a 2D view, with the black triangle representing the displays gamut, and other reference colour spaces shown for comparison

• Gamma - we aim for 2.2 which is the default for computer monitors

• Colour temperature / white point - we aim for 6500k which is the temperature of daylight

• Luminance - we aim for 120 cd/m², which is the recommended luminance for LCD monitors in normal lighting conditions

• Black depth - we aim for as low as possible to maximise shadow detail and to offer us the best contrast ratio

• Contrast ratio - we aim for as high as possible. Any dynamic contrast ratio controls are turned off here if present

• dE average / maximum - as low as possible. If DeltaE >3, the color displayed is significantly different from the theoretical one, meaning that the difference will be perceptible to the viewer. If DeltaE <2, LaCie considers the calibration a success; there remains a slight difference, but it is barely undetectable. If DeltaE < 1, the color fidelity is excellent.

Default settings of the screen were as follows:

Samsung S27A850D - Default Factory Settings

 

 

The out of the box performance of the S27A850D was not great unfortunately. You could of course immediately notice the extremely high brightness of the display and it was uncomfortable to use. Just another manufacturer who decided it was sensible to ship the screen set at 100% brightness by default! The colours did feel quite even and balanced although some darker shades didn't look right, and appeared to have an incorrect gamma.

 

The CIE diagram on the left confirms that the monitors colour gamut (black triangle) closely matches the sRGB colour space (orange triangle). It extends a little past the sRGB space in greens, blues and reds in this 2D view of gamut. This diagram shows that it pretty much completely covers the sRGB reference which matches out accurate calculations based on the panel spec sheet, which reveal a 99.5% coverage of the sRGB colours.

 

 

Default gamma was recorded at 2.4 average, leaving it 11% out from the target of 2.2. Gamma was too high in darker tones, ranging up to 2.61 in some grey shades. In the lighter grey shades it was then too low, so the gamma curve was poorly set up here. White point was much closer to the desired level thankfully, being measured at 6725k which was 3% out from the target and only a little too cool. Note that we are using a Spectrophotometer to make these measurements which is not sensitive to the W-LED backlight as some colorimeter devices can be. When using a standard gamut colorimeter not designed to work with modern backlighting units like W-LED, there can be a typical deviance of 300 - 600k in the white point measurement which is why some sources may refer to a different white point in this test incorrectly.

 

The screen offers 3 preset gamma modes via the OSD menu, so we tested the other two as well in case either were more accurate than the default Mode1. In gamma mode 2, average gamma was measured at 2.6 (18% out), which was now further away from the 2.2 target. The rest of the measurements and results remained basically the same as above. Gamma mode 3 was unfortunately even further out at 2.8 (27%). It also had a negative impact on colour accuracy with dE at 5.2 average and 9.9 max. Switching to Mode2 and then Mode3 also introduced more banding in colour gradients which of course you want to avoid. I would recommend sticking with Mode1 for the most accurate starting point for this screen. Calibration with a hardware device would be preferred to correct the gamma curves.

 

 

Luminance was recorded at a very high 344 cd/m² which is way too high for comfortable use. At this high 344 cd/m² luminance, the black depth was 0.43 cd/m². This gave us a static contrast ratio of 802:1. This was our first test of a PLS screen and it was reasonably good. Some modern IPS panels can offer a contrast ratio of ~1000:1 so this falls behind a little sadly. It is more in keeping with some other more widespread IPS panels at the moment which typically have a contrast ratio of around 700 - 850:1.

 

Colour accuracy was fairly poor at default factory settings with an average DeltaE (dE) of 3.6, ranging up to a maximum of 7.8. Some adjustments to the brightness control can hopefully help improve the default set up for casual users who don't have access to a hardware calibration device but anyone wishing to use the screen for more demanding uses where colour accuracy is important will want to use a calibration device really. Given this is a "professional range" screen, I was perhaps hoping for a bit more out of the box.

 

 

 

Testing Colour Temperatures

 

 

The S27850D features a range of 'Color tone' presets within the OSD menu which offer you various colour temperature modes. We measured the screen with the X-rite i1 Pro spectrophotometer in each of the preset modes to establish their colour temperature / white point. All other settings were left at factory defaults and no ICC profile was active. The results are recorded below:

 

 

The colour temperature modes worked as they should. With the normal and custom modes returning a default temperature of 6725k (custom will change if you alter the RGB levels), the cool and warm settings behaved as they should. The cool options altered the white point up to 8780k in mode 2, and the warm settings altered the white point down to 3972k in mode 2. These might be useful to some users.

 

 

 

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.

Samsung S27A850D - Calibrated Settings

Monitor OSD Option	Default Settings
Brightness	17
Contrast	75
RGB Channels	43, 48, 45
Color Tone	Custom
Gamma	Mode1
MagicBright	Custom
MagicColor	Off

	Calibrated Settings
luminance (cd/m2)	120
Black Point (cd/m2)	0.16
Contrast Ratio	761:1

 

I first of all reverted to the 'custom' mode in the OSD menu which would allow me access to the individual RGB channels. During the calibration process this would allow me to make more adjustments at the hardware level which would help preserve grey tones and gradients during the profiling. This allowed me to obtain an optimum hardware starting point and setup before software level changes would be made at the graphics card level. Adjustments were also made during the process to the brightness control and to the RGB channels as shown in the table above. I remained in gamma Mode1 since that had returned the closest gamma curve by default, albeit not that close to our target. After this I let the software carry out the LUT adjustments at a graphics card level and create an ICC profile. The screen does not feature a hardware LUT calibration option so other than the OSD alterations, the rest of the process is carried out at a graphics card level in profiling the screen.

 

 

The calibration was a success. The gamma discrepancy that we saw before (11%) had been almost corrected now to leave us with 0% deviance and an average gamma of 2.2. There was still some slight discrepancy with the gamma curve with some grey shades but it was much smaller than before and they were closer to 2.2. White point was also corrected to 6540k, bringing it 1% out from the target. Luminance had been reduced to a much more comfortable 120 cd/m² thankfully after the adjustment of the OSD brightness control. Black depth was still fairly good at 0.16 cd/m² and this gave us a calibrated static contrast ratio of 761:1. Colour accuracy was also improved nicely with dE average now only 0.3 and maximum only 1.0. LaCie would consider colour fidelity to be excellent overall.

 

Testing the screen with various colour gradients showed fairly smooth transitions. Gradation was noticeable across many shades, even in light greys and you could see some "steps" across the range of colours. There was some slight banding as well in darker and medium tones after calibration but nothing too severe. The gradation was more apparent to be honest that many other screens we've tested. Not a problem for a normal average user but if you're working with a lot of gradients type content it's something to be aware of.

 

You can use our settings and try our calibrated ICC profile if you wish, which are available in our ICC profile database. Keep in mind that results will vary from one screen to another and from one computer / graphics card to another.

 

 

Calibration Performance Comparisons

 

 

I've provided a comparison above of the S27A850D against some of the other screens we have tested. Out of the box average dE was 3.6 which was not very good really. Compared to some of the other 27" models we have tested, the S27A850D (3.6) had a similar level of accuracy out of the box to the wide gamut IPS Dell U2711 (3.7) and a bit better than the IPS Hazro HZ27WB (5.1).

 

The 27" Hazro HZ27WC and HP ZR2740w have W-LED backlighting and IPS panels, and offered a good factory calibration with a default dE average of only 1.5 and 2.4 respectively. The professional grade 27" NEC PA271W and SpectraView Reference 271 were better still at 1.1 dE and 1.5 dE average respectively. We will ignore the result of the HZ27WA here since that model was not factory calibrated and was a pre-release sample. The TN Film based ViewSonic VX2739wm was quite comparable to the Samsung in terms of default colour accuracy with an average dE of 3.4.

 

A fairly poor out of the box performance from the S27A850D to be honest with a high dE average and also some noticeable deviance in gamma to contend with. Some form of software profiling using a colorimeter would of course be beneficial to correct these issues wherever possible.
 

 

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

 

 

 

The calibrated black depth and contrast ratio of the S27A850D were reasonable but perhaps we had hoped for more from Samsung's new PLS technology. At the end of the day it was quite comparable with a good (but not great) IPS panel. Calibrated black depth was 0.16 cd/m² which left us with a static contrast ratio of 761:1. This was pretty much on par with the IPS based HP ZR2740w (751:1) and Hazro HZ27WA/C (~744:1). We had seen some better contrast ratios from other IPS panels though reaching up to around 950:1 in some cases (e.g. Dell U2412M at 947:1).The BenQ EW2420 and Samsung F2380 with their AMVA and cPVA panels respectively offered some fantastic contrast ratios of ~3000:1 which other technologies cannot compete with at the moment. If you want a very high static contrast ratio from Samsung, you'd be better looking at one of their modern cPVA based screens. Hopefully over time the PLS technology will also improve and offer higher contrast ratios but we will have to wait and see.

 

 

 

 

Contrast Stability

 

The luminance range of the screen was reasonable with a total adjustment range of 270 cd/m² available through alterations to the brightness setting. At the top end, the luminance was a very high 345 cd/m² which was actually a little more than the specified maximum brightness of 300 cd/m². At the lowest setting you can control the luminance down to 75 cd/m² which should be adequate for most users, even in low lighting conditions. Black point ranges from 0.43 to 0.09  cd/m² with these adjustments.

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

Static contrast ratio remained reasonably high and stable across the range, with an average figure of 808:1 which was ok. Being the first PLS panel we have tested, it was hard to know what to expect in this regard but it performs comparably to a good IPS panel in terms of contrast ratio. These contrast measurements were plotted on the graph shown above.

 

Dynamic Contrast

The Samsung S27A850D features a dynamic contrast ratio (DCR) control within the OSD menu. The spec for the screen doesn't seem to mention a DCR figure, only that it has 'MEGA DCR'. Some Samsung sites actually list the screen as having a static contrast ratio of 3000:1 which is of course wrong given our measurements and based on the spec of the PLS panel itself which lists it as 1000:1. Maybe we can assume that is a typo and that the DCR should be ~3000:1? We will test it ourselves to see what kind of performance is achieved. Dynamic contrast ratio involves controlling the backlight of the screen automatically, depending on the content shown on the screen. In bright images, the backlight is increased, and in darker images, it is decreased. For this test I would use the colorimeter to record the luminance and black depths at the two extremes. Max brightness would be recorded on an almost all white screen once the DCR has caught up. Black depth would be recorded on an almost all black screen. In real use you are very unlikely to ever see a full black or full white screen, and even our tests are an extreme case to be honest. Carrying out the tests in this way does give you a good indication of the screens dynamic contrast ratio in real life situations however.

During this test you could see that if you switched from a black to white screen, the DCR changed the brightness of the screen very quickly (less than a second). The maximum luminance measured was 331.5 cd/m² and the minimum black depth was 0.09 cd/m². This gave us a useable dynamic contrast ratio of 3683:1 which was pretty good. It might not be as high as the crazy specs you will see advertised on modern screens, but at least it worked in real life applications unlike many other displays. The DCR was pretty much controlling the full range of the backlight adjustment here, only offering a slightly lower max luminance than the 344.9 cd/m² we had measured in the contrast stability tests (at 100% brightness). That would only have extended the DCR to about 3800:1 anyway so it was very close in real use. Not a bad performance from the S27A850D here although transitions were super-quick.

 

 

Viewing Angles

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

Viewing angles of the Samsung S27A850D are very good and very similar really to an IPS panel. Horizontally there are very wide fields of view with a small contrast shift only really becoming noticeable from a fairly wide angle of about 45�. Vertically, the contrast shift was a little more pronounced but the fields of view were still good. From a wide angle there is a slight pink-ish colour tone introduced and the image darkens. Of interest is the change in the pixel structure from Samsung's traditional PVA technology to their new PLS technology. As a result of this change the panel is free from the off-centre contrast shift which you see from VA matrices. This was one of the reasons why IPS technology is so highly regarded in the colour enthusiast and professional space since it can offer very wide viewing angles and freedom from this contrast shift. With PLS offering the same freedom it could well become a popular choice for colour critical work as well where wide viewing angles are important. The PLS panel is also free of the very noticeable contrast and colour tone shifts you see from TN Film panels vertically.

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

On a black image, like many IPS panels, there is a white glow when viewed from an angle. This picture was taken in a darkened room though and in normal working conditions this shouldn't present much problem. There is no A-TW polarizer or equivalent film on this panel which is something rarely used now in the IPS market, but was implemented on some older IPS screens to improve the off centre black viewing.

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 S27A850D was reasonable. Around 70% of the screen showed very little deviation from the central point and was within 10% variation of the 120 cd/m². The lower half of the screen seemed to be a little darker than the upper half, especially towards the two lower corners. Luminance ranged down to ~105 cd/m² in these corners. The lowest measured luminance was along the centre of the right hand edge where it dropped down to 102 cd/m². All in all though the uniformity was pretty good and there was no severe issue.

Backlight Leakage

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

As usual we also tested the screen with an all black image and in a darkened room. A camera was used to capture the result. There were a couple of areas of backlight leakage from our sample unfortunately. This was most noticeable in two patches along the bottom edge which you can spot in the above image quite clearly. There was also some more slight clouding from the top corners of the screen. Sadly there seem to be varying reports about the backlight on this model across the internet from users and reviewers. Some samples of the screen are fine, but others have varying levels of leakage. From our sample, there appeared to be an issue along the lower edge which was a shame. I would advise some caution about possible backlight irregularity with this model based on user reports and our review, but don't be put off the screen solely because of it. Results will vary depending on supply lines, stocks, regions etc and so it's a very hard thing to predict before purchase. If you do have any serious issues you can always return the screen under Distance Selling Regulations (if bought online) or perhaps even agree an RMA with Samsung for a replacement.

 

General and Office Applications

The Samsung S27A850D features a massive 2560 x 1440 WQHD resolution which is only just a little bit less vertically than a 30" screen. The pixel pitch of 0.233mm is very small as a result, and by comparison a standard 16:10 format 24" model has a pixel pitch of 0.270mm and a 30" model has 0.250mm. These ultra-high resolution 27" models offer the tightest pixel pitch and therefore the smallest text as well. I found it quite a change coming from 21.5 - 24" sized screens, even those offering quite high resolutions and small pixel pitches.  Some users may find the small text a little too small to read comfortably, and I'd advise caution if you are coming from a 19" or 22" screen for instance where the pixel pitch and text are much larger. I found a 30" screen to be quite a change with text size when I first used one, and this is very similar and even a little bit smaller! I still personally prefer the slightly larger text of a 24" model myself, but I expect I could happily get used to the added resolution on these models given time. The extra screen size also takes some getting used to over a few days as there really is a lot of room to work with.

The massive resolution is really good for office and general use, giving you a really big screen area to work with. It is a noticeable upgrade from a 24" 1920 x 1200 resolution, and it's good to see Samsung have opted for a high res panel here rather than reverting to a 1920 x 1200 / 1920 x 1080 res panel as you may find in other older 27" models. For those wanting a high resolution for CAD, design, photo work etc, this is a really good option. The image was very sharp and crisp and text was very clear over the digital interfaces. There is no analogue input offered here to compare with because of the high native resolution of the panel.

There were a series of 'MagicBright' preset modes provided on this screen but there weren't any specifically designed for 'text', 'internet' or anything like that sadly. You will probably want to set up the custom mode to your liking, and preferably with a calibration device to obtain a decent configuration. The default brightness of the screen is far too high while set at 100%, and you will probably want to reduce this to around 15 - 20% to obtain a comfortable luminance at around 120 cd/m². The colour tone presets may be useful to some users if they want to have a cooler or warmer image.

The screen offers a 3 port USB 3.0 hub which is useful for connecting external devices, and it was good to see v3.0 offered here. The ports are located on the back of the screen on the side of the central section so they aren't the easiest to reach for quick connecting and disconnecting of devices. Fine for leaving things connected and tucked nicely out of the way, but I would have liked to have seen a couple of ports on the side of the bezel for easier access. There was a good range of ergonomic adjustments available from the screen although the tilt and pivot adjustments were very stiff to use sadly. Height adjustment was smooth and nice to see included. The screen even offers a rotation function, although this is probably impractical at this size. Some of the energy saving features are also great to see included, and should be useful in an office environment as well where multiple screens are set up. The ambient light sensor can be handy for altering the backlight intensity with changing lighting conditions, and the human motion sensor is a nice extra feature. The only other thing left off which I would have perhaps liked to have seen, but which is rarely offered, is a card reader of some sort.
 

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

The screen is designed to run at its native resolution of 2560 x 1440 and at a 60Hz recommended refresh rate. However, if you want you are able to run the screen outside of this resolution. We tested the screen at a lower 1920 x 1080 resolution while maintaining the same aspect ratio (16:9) to see how the screen handles the interpolation of the resolution. At native resolution the text was very sharp as you can see from the top photograph. When you switch to a lower resolution the text is more blurry. There was fairly high levels of overlap of the pixels but text was still reasonably readable. Native resolution is recommended where possible of course for optimum picture quality.

 

Responsiveness and Gaming

The S27A850D is rated by Samsung as having a 5ms G2G response time which implies the use of overdrive / response time compensation (RTC) technology, used to boost pixel transitions across grey to grey changes. The Samsung LTM270DL02 PLS panel being used is rated by Samsung with a 12ms ISO response time (black > white > black) as well to give you an indication.

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

The screen was tested using the chase test in PixPerAn, a good bit of software for trying to quantify differences in real terms responsiveness between monitors. As a reminder, a series of pictures are taken on the highest shutter speed and compared. The images above are the best case examples from the screen with the 'response time' setting at each level. In the 'normal' mode the responsiveness of the panel is actually still pretty good. There is no obvious ghosting to the naked eye although a reasonable degree of motion blur is detectable. When switching to the 'faster' mode, this blur is reduced a fair bit and the moving image looks sharper and clearer. This setting is turning the overdrive impulse up of course and so pixel transitions are being sped up. This translates into a real life difference in perceived response times.

The 'fastest' setting turns the overdrive impulse up again another notch. However, in this mode it is turned up too high and is poorly controlled. As a result a noticeable white halo is introduced behind the moving car. Here the overdrive is causing the pixels to overshoot their required state and unfortunately introduce this distracting artefact. I wouldn't recommend using this setting unfortunately as the overshoot is quite pronounced and distracting during use. The 'faster' setting seems to offer the optimum performance in terms of fast pixel response times, and also freedom from any obvious overshoot, and I would recommend using that option.

Display Comparisons

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

27" 5ms G2G Samsung PLS (response time = faster)

27" 12ms G2G LG.Display H-IPS

27" 6ms G2G LG.Display H-IPS

27" 6ms G2G LG.Display H-IPS

I have provided a comparison of the S27A850D first of all above against 3 other 27" screens we have tested which all use IPS panel technology. The S27A850D performed very well actually in these tests. In the 'faster' response time setting it had returned optimal response times and no obvious RTC overshoot. It showed a lower level of motion blur than the HP ZR2740w and Hazro HZ27WC which was pleasing. The Dell U2711 had performed well in terms of motion blur, but as you can see from the above photos, there was a dark overshoot introduced unfortunately.

27" 5ms G2G Samsung PLS (response time = faster)

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

24" 8ms G2G LG.Display e-IPS

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

Above is a comparison of the S27A850D against some popular models in smaller sizes. Again these other 3 models are IPS based. The HP ZR2440w had performed very well in these tests and showed a similar low level of motion blur to the Samsung S27A850D. There was a very slight dark and pale halo trail evident in those tests which does not appear to affect the S27A850D much. The Dell U2412M and U2312HM again offered low levels of motion blur but a more obvious dark overshoot trail was introduced. It seems that the faster IPS panels we have compared the S27A850D with here can achieve some very low levels of motion blur and fast pixel response times. In many cases though it is at the expense of some overdrive artefacts, and dark and pale halos and trails are quite common. The S27A850D seemed to be free of these issues, at least in its 'faster' setting which was very good.

27" 5ms G2G Samsung PLS (response time = faster)

23" 25ms Samsung cPVA

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

As a comparison against Samsung's long-standing PVA technology I have provided the results of two of Samsung's more recent cPVA panels in the NEC EX231WP and Samsung F2380. These PVA panels are quite slow in practice unfortunately and show a pretty high level of motion blur and ghosting of the moving car. Even when overdrive is applied aggressively, as in the case with the F2380, the response time cannot match modern fast IPS and TN Film panels. It seems that Samsung's new PLS technology is also inherently responsive which is good news.

27" 5ms G2G Samsung PLS (response time = faster)

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

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

22" 3ms G2G Samsung TN Film + 120Hz

I've also included a comparison above against 3 gamer-orientated screens, including the 27" TN Film based ViewSonic VX2739wm. This is a competing screen at the same size, but with different panel technology it is significantly different in performance in a lot of areas. That model is aimed primarily at gamers and even has a 1ms G2G quoted response time. It performs marginally better than the S27A850D in these tests as a result but overall the motion blur is at a fairly similar level. Keep in mind the S27A850D isn't really designed as a gamers screen as well which is quite impressive.

The other two models here both featuring heavily overdriven TN Film panels, and are combined with 120Hz technology. The pixel responsiveness of both of these is little ahead of the S27A850D, but more importantly the 120Hz frequency allows for improved 120fps frame rates and the support of 3D content as well. The BenQ XL2410T does show some even more obvious RTC overshoot in the form of very dark trails behind the moving image (speech bubble and head) which is unfortunate, and a sign that the RTC impulse is too aggressive. The Samsung 2233RZ remains our champion in this test.

The responsiveness of the S27A850D should be fine for most gaming, even at quite high levels. Make sure you choose the 'faster' response time setting from within the OSD and you should then experience good responsiveness, with low levels of motion blur and freedom of any obvious overshoot artefacts which appear in the 'fastest' setting. 

Additional Gaming Features

Aspect Ratio Control - The screen offers a couple of options for hardware level aspect ratio control. There are settings for 'auto' (maintaining the source aspect ratio automatically) and 'wide' (displaying the image in full screen regardless of the source aspect ratio). Oddly the manual for the S27A850D suggests there are also options for 4:3 aspect and 'screen fit' (display with original aspect ratio without cutting off), but these did not seem to be available. Maybe they were left off the final version of the screens software?

Preset Modes - There is a 'game' preset mode available from within the MagicBright menu if you want a mode with boosted brightness and a more unnatural feel. The dynamic contrast option is not available within this mode however, and you would need to revert to the defined dynamic contrast preset if you want to use that feature.

 

Input Lag

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

Input Lag Classification

To help in this section we will also introduce a broader classification system for these results to help categorise each screen as one of the following levels:

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

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

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

For the full reviews of the models compared here and the dates they were written (and when screens were approximately released to the market), please see our full reviews index.

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

The Samsung S27A850D showed an average display input lag of 28ms during this test, ranging up to 32ms maximum. This is the overall lag of the image compared with a CRT, taking into account signal processing delay and pixel response times. This was a little slower than some other screens but with an average lag of just under 2 frames it is not too severe. The lag of this screen has been categorised as CLASS 2 as detailed above. This should be adequate for most moderate gaming still but for those wanting to play fast FPS it might prove an issue in some cases.
 

 

Movies and Video

 The following summarises the screens performance in video applications:

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

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

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

• Digital interfaces 2x DL-DVI and DisplayPort supports HDCP for any encrypted and protected content

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

• Missing HDMI though which is widely used for external devices, DVD players etc.

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

• Dynamic contrast ratio is available as a MagicBright preset and works quite well, allowing for a DCR up to around 3700:1

• 'Cinema' preset mode available if you want a different set up to your normal mode

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

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

• Good ergonomic adjustment range available from the stand allowing you to obtain a comfortable position for movie viewing. Movements are smooth but some are quite stiff to operate

• Some noticeable backlight leakage, particularly along the bottom edge. This type of leakage may prove an issue when watching movies where black borders are present unfortunately.

• No integrated stereo speakers on this model

• No picture in picture (PiP) available, but picture by picture (PbP) is present for those who might want to use it

• For PAL sources, we have tested the screen and confirmed it will support the full native resolution of 2560 x 1440 at 50Hz refresh rate.

 

Conclusion

 

The Samsung S27A850D was a very interesting model to test, not only because of its decent range of options and features, but because of the arrival of Samsung's new PLS technology. Overall I felt that the screen was a good first offering in the PLS market to be honest. Performance wise the screen could be closely compared with a modern e-IPS panel. It offered similar wide viewing angles, very good pixel responsiveness and pretty good black depth / contrast ratio. The contrast ratio was perhaps not quite as high as we'd have hoped, but it was still decent enough and comparable to a good (but not great) IPS matrix. It is a promising first appearance for PLS and hopefully we will see more of it in the future.

Unfortunately there were a few issues with this screen as well. The out of the box performance was pretty poor, with an inaccurate gamma curve, high luminance and bad colour accuracy. If you are buying this screen you would ideally want access to a colorimeter or some sort, and certainly want some form of calibration to help correct some of these issues. Once calibrated it performed well however which is pleasing. Backlight bleed seems to be a bit of a variable issue with this screen as well. Our sample had some bleed along the bottom edge which was unfortunate. It does seem that samples will vary a lot, but if you end up with a bad unit you should be able to return it under Distance Selling Regulations or a manufacturer return I would hope.

On the plus side Samsung have avoided one of the big niggles some people have with modern IPS panels, that being the aggressive, grainy AG coating on the panel. Here the coating is much more like PVA matrices and is smoother than some of the dirty looking IPS offerings in the market. The wide range of ECO modes and power saving features are useful and we also have a rare working dynamic contrast ratio option for those who like it.

All in all this is quite an interesting alternative in the 27" market. It currently retails for ~�565 GBP in the UK which is a similar price to the popular Dell U2711. It would be worth a consideration if you want a comparable alternative to IPS technology, while still giving you a good all round set of features, options, functions and performance.