Introduction

Over the last year or so there's been a steady influx of new displays offering a super-high resolution. The new wave of "4k" displays sporting 3840 x 2160 resolutions, 4 times that of traditional 1920 x 1080 HD content has begun to flood the market, with various options available and most manufacturers now producing some kind of 4k offering. In January we tested our first 4k screen in the form of Dell's UP3214Q, a premium grade screen with a lot of high end features and a price tag to match. In fact a lot of the early 4k resolution displays came at a very high cost. A little later, 4k resolutions started to be introduced in smaller displays, and in many cases at very affordable prices. A new batch of 28" sized screens hit the market, sporting this 4k resolution and also offering some impressive specs to try and attract the gaming market. Expensive, high-end panels like that used in the Dell were dropped in favour of lower cost TN Film matrices, helping to make 4k more affordable to the masses.

We've got one of these 28" 4k models with us now for review. Samsung's U28D590D is one of the better spec'd offerings in this space, boasting a 1ms G2G response time and also the all-important support for 60Hz refresh rates when using the 3840 x 2160 resolution over DisplayPort. It is also detected as a single display, as opposed to being a Multi-Stream detection as we'd experienced with the UP3214Q (explained more in that review). Some other competing models are limited to 30Hz refresh rate due to the relatively new usage of such a high resolution. Fine for day to day uses, but certainly limiting when it comes to games and dynamic content. Thankfully the Samsung offering can run at the full 60Hz refresh rate.

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Specifications and Features

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

The U28D590D offers a somewhat limited range of connectivity options. There are only DisplayPort and 2x HDMI interfaces provided for video connections. There is no DVI or D-sub offered here. The DisplayPort 1.2 connection can support for the full 3840 x 2160 resolution at 60Hz refresh rate, while the HDMI 1.4 ports can only support the native res at 30Hz. It's nice to see HDMI provided for connection of external devices, consoles etc. Even if they don't support the 4k resolution the screen can upscale the image on the nice large 28" sized screen. Cables are provided in the box for both HDMI (x1) and DisplayPort which is good.

The screen has an external power supply so there is an external power brick supplied in the box. There are no extras really on this screen and it is lacking things like USB ports, speakers, ambient light sensors etc. It supports Picture in Picture (PiP) and Picture by Picture (PbP) modes when using multiple inputs.

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

OSD Menu

Above: joystick controller on the back of the screen. Click for larger version

The OSD menu is accessed and controlled through a single joystick controller located on the back right hand edge of the screen as you look at it from the front. This joystick is pressable as well and controls the whole menu.

Moving the joystick in any direction gives you quick access to a couple of features. When you move it, the menu above pops up. If you then press up/down on the joystick you get quick access to the brightness, and also from there quick access to contrast and sharpness. The menu changes to the following:

Pressing the joystick right/left brings up quick access to the volume control as shown below if you're using the audio out connection on the scren:

 

Pressing the button in brings up access to the main menu. You can go up to access the main OSD, left to choose the screen input, right for PiP/PbP options and down to power the screen off. There's no power on/off button as such, it's a function of the OSD menu.

If you go into the main OSD menu it is split into 5 sections down the left hand side. If you then move right on the joystick you can enter the section you are currently highlighted on and the menu options move over as shown below.

In the picture menu there are controls for brightness, contrast and sharpness. The "game mode" is a preset specifically designed for gaming. You can access the MagicBright preset modes here as well:

You can also adjust the color settings from this section which gives you control over the RGB levels as shown below:

There is also access to control the response time setting here:

The 'screen' section of the menu allows you to control the aspect ratio option (wide or auto) and also the PiP and PbP settings:

The options section is pretty self-explanatory:

In the 'settings' section there are a few more things to play with:

Finally, the 'information' section confirms your resolution and refresh rate:

All in all, navigation was pretty simple via the joystick controller, and there were a decent range of options to play with. Sometimes you had to drill through several layers of menu but all in all it was pretty good. The software was quite low res and looked big though, certainly compared with the sharpness and res of the panel.

 

Power Consumption

In terms of power consumption the manufacturer lists 32.0W usage in the "Energy Star test condition" and 0.3W in standby. We carried out our normal tests to establish its power consumption ourselves.

We tested this ourselves and found that out of the box the screen used 39.3W at the default 100% brightness setting. Once calibrated the screen reached 23.2W consumption, and in standby it used only 0.5W. We have plotted these results below compared with other screens we have tested. The consumption is very comparable to other W-LED backlit displays, with wide gamut GB-r-LED units like the ViewSonic VP2772 using slightly more (comparing calibrated states).

Panel and Backlighting

Panel Part and Colour Depth

The Samsung U28D590D utilises a Innolux (previously Chi Mei Optoelectronics / Chi Mei Innolux) M280DGJ-L30 TN Film panel which is capable of producing 1.07 billion colours. This is achieved apparently through a 10-bit grey scale and the detailed panel spec sheet does not mention the use of Frame Rate Control (FRC). Keep in mind whether this is practically useable and whether you're ever going to truly use that colour depth. You need to have a full 10-bit end to end workflow to take advantage of it which is still quite expensive to achieve and rare in the market, certainly for your average user. This includes relevant applications and graphics cards as well, so to many people this 10-bit support might be irrelevant.

The panel is confirmed when dismantling the screen as shown:

Screen Coating

The screen coating on the U28D590D is a a medium anti-glare (AG) offering. It isn't a semi-glossy coating, and isn't as light as some modern IPS type panels either. It's in keeping with other TN Film panels we've tested. Thankfully it isn't a heavily grainy coating like some old IPS panels feature, although there is some graininess noticeable sometimes. It retains its anti-glare properties to avoid too many unwanted reflections of a full glossy coating, but does not produce an too grainy or dirty an image that some thicker AG coatings can. There were no cross-hatching patterns visible on the coating

Backlight Type and Colour Gamut

The screen uses a White-LED (W-LED) backlight unit which has become very popular in today's market. This helps reduce power consumption compared with older CCFL backlight units and brings about some environmental benefits as well. The W-LED unit offers a standard colour gamut which is approximately equal to the sRGB colour space. Anyone wanting to work with wider colour spaces would need to consider wide gamut CCFL screens, or perhaps the newer range of GB-r-LED displays available now. If you want to read more about colour spaces and gamut then please have a read of our detailed article.

Backlight Dimming and Flicker

We tested the screen to establish the methods used to control backlight dimming. Our in depth article talks in more details about a common method used for this which is called Pulse Width Modulation (PWM). This in itself gives cause for concern to some users who have experienced eye strain, headaches and other symptoms as a result of the flickering backlight caused by this technology. We use a photosensor + oscilloscope system to measure backlight dimming control with a high level of accuracy and ease. These tests allow us to establish

1) Whether PWM is being used to control the backlight
2) The frequency and other characteristics at which this operates, if it is used
3) Whether a flicker may be introduced or potentially noticeable at certain settings

If PWM is used for backlight dimming, the higher the frequency, the less likely you are to see artefacts and flicker. The duty cycle (the time for which the backlight is on) is also important and the shorter the duty cycle, the more potential there is that you may see flicker. The other factor which can influence flicker is the amplitude of the PWM, measuring the difference in brightness output between the 'on' and 'off' states. Please remember that not every user would notice a flicker from a backlight using PWM, but it is something to be wary of. It is also a hard thing to quantify as it is very subjective when talking about whether a user may or may not experience the side effects.

100%                                                                            50%
 

31%                                                                            30%

20%                                                                            0%

Above scale = 1 horizontal grid = 1ms

At 100% brightness a constant voltage is applied to the backlight and there is no need for any kind of PWM regulation as normal for most screens. As you begin to lower the brightness setting a Direct Current (DC) method is used initially, as opposed to any kind of Pulse Width Modulation (PWM). As a result, there is no oscillation or PWM off/on backlight flickering. This applies for all settings between 100% and 31% brightness. From 30% and below a PWM technique is used for backlight dimming, where the duty cycle (on time) gets progressively shorter as you lower the brightness setting. This operates at a frequency of 240 Hz which is pretty low, and so may present problems to users sensitive to the use of PWM and flickering backlights. If you need to use the screen below 31% brightness setting (see our following section) this may be problematic to some.

For an up to date list of all flicker-free (PWM free) monitors please see our Flicker Free Monitor Database.

 

Contrast Stability and Brightness

The brightness control gave us a very good range of adjustment. At the top end the maximum luminance reached 362 cd/m² which was high, and only just shy of the specified maximum brightness of 370 cd/m² from the manufacturer. There was a large 348 cd/m² adjustment range in total, and so at the minimum setting you could reach down to a very low luminance of 14 cd/m². This should certainly be adequate for those wanting to work in darkened room conditions with low ambient light. A setting of 22 in the OSD menu should return you a luminance of around 120 cd/m² at default settings. It should be noted that the brightness regulation is controlled without the need of Pulse Width Modulation using a Direct Current (DC) method for settings between 100 and 31% and so the screen is flicker free at anything above 30%. Below that, a PWM method is used at a low frequency of 240Hz, which may present problems to those sensitive to its use. You can only get down to a luminance of only 158.4 cd/m² before you need to enter the PWM-zone so it's likely that this might present an issue for a lot of users, as they will likely want to have the screen darker than this and will therefore be within the PWM-zone.

We have plotted the luminance trend on the graph above. The screen behaves as it should in this regard, with a reduction in the luminance output of the screen controlled by the reduction in the OSD brightness setting. This is a linear relationship between a setting of 100 and 31, as you can see from the line but from 30 - 0%, where the PWM usage kicks in, there is a steeper curve where the brightness adjustments makes slightly more differences to the luminance.

The average contrast ratio of the screen was moderate for a TN Film panel with an average of 840:1. This was pretty stable across the brightness adjustment range as shown above.

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.

We restored our 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 i1 Display Pro colorimeter) combined with LaCie's Blue Eye Pro software suite. An X-rite i1 Display Pro colorimeter was also used to verify the black point and contrast ratio since the i1 Pro spectrophotometer 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 Performance and Setup

Default settings of the screen were as follows:

Samsung U28D590D - Default Factory Settings

  

 

Initially out of the box the screen was very bright and was set at the maximum 100% brightness setting. Colour balance felt good, and you could tell it was a standard gamut screen. The image felt a little washed out but only slightly. We went ahead and measured the default state with the i1 Pro.

 

The CIE diagram on the left of the image confirms that the monitors colour gamut (black triangle) is roughly equal to the sRGB colour space. There is some over-coverage in some shades, with green and blue being a little wider than the sRGB space. Default gamma was recorded at 2.1 average, leaving it with a small 6% deviance from the target of 2.2 which was reasonable. In lighter grey shades the gamma was further away from the target as you can see from the table below, leading to some of the washed out appearance we noticed. White point was measured at 6635k being close to the target of 6500k which was good and with only a 2% deviance.

 

 

Luminance was recorded at a very bright 370 cd/m² which is far too high for prolonged general use. The screen was set at a default 100% brightness in the OSD menu but that is easy to change of course to reach a more comfortable setting. The black depth was 0.44 cd/m² at this default brightness setting, giving us a reasonable (for a TN Film panel) static contrast ratio of 842:1. Colour accuracy was fairly good out of the box with a default dE average of 2.6, and maximum of 5.9. Testing the screen with various gradients showed smooth transitions with no sign of any banding thankfully. There was some gradation evident as you will see from most monitors. Overall the default setup was decent enough, with the gamma and white point being reasonable. We would have perhaps hoped for a slightly higher contrast ratio nearer to 1000:1 which some TN Film panels can achieve.

 

We also switched to the 'standard' preset mode (MagicBright option) to test the default setup in that mode:

Samsung U28D590D - Default Factory Settings, Standard mode

 

When switching to the 'standard' MagicBright mode there was an immediate drop in the luminance of the screen. Looking at the OSD menu confirms the default brightness is now 51 instead of 100. This gave us a more comfortable luminance of 233 cd/m², although still too bright for ongoing use. Other aspects of the setup had also improved slightly with an improved gamma (now 3% out), and slightly improved colour accuracy (dE average of 2.4). This might make a better starting point for users not wishing to carry out more detailed calibration of the screen. You can revert to the standard mode and then just change the brightness to suit.

 

 

 

 

 

Calibration

 

We used the X-rite i1 Pro spectrophotometer combined with the LaCie Blue Eye Pro software package to achieve these results and reports. An X-rite i1 Display Pro colorimeter was used to validate the black depth and contrast ratios due to lower end limitations of the i1 Pro device.

 

Samsung U28D590D - Calibrated Settings

   

 

We changed to the 'custom' MagicBright preset mode which gives us full control over settings like the RGB levels. In changing the RGB channels this moves you into the 'custom' color tone mode as well, since you are moving away from any preset RGB values. We stuck with the default gamma mode 1 since we know this was about as close to the 2.2 gamma by default as possible. All these OSD changes allowed us to obtain an optimum hardware starting point and setup before software level changes would be made at the graphics card level. We left the  LaCie software to calibrate to "max" brightness which would just retain the luminance of whatever brightness we'd set the screen to, and would not in any way try and alter the luminance at the graphics card level, which can reduce contrast ratio. These adjustments before profiling the screen would help preserve tonal values and limit banding issues. After this we let the software carry out the LUT adjustments and create an ICC profile.

 

 

Average gamma was now corrected to 2.2 average, correcting most of the 6% deviance we'd seen out of the box and only leaving it with a minor 1% deviance now. The decent white point was retained at 6499k, correcting the minor 2% deviance out of the box. Luminance had been improved thanks to the adjustment to the brightness control and was now being measured at 121 cd/m². This left us a black depth of 0.15 cd/m² and maintained a reasonable static contrast ratio (for a TN Film panel) of 797:1. Colour accuracy of the resulting profile was very good, with dE average of 0.7 and maximum of 1.8. LaCie would consider colour fidelity to be very good overall. Testing the screen with various colour gradients showed mostly smooth transitions. There was some slight gradation in darker tones but no banding introduced due to the adjustments to the graphics card LUT from the profilation of the screen which was pleasing. 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

 

The comparisons made in this section try to give you a better view of how each screen performs, particularly out of the box which is what is going to matter to most consumers. When comparing the default factory settings for each monitor it is important to take into account several measurement areas - gamma, white point and colour accuracy. There's no point having a low dE colour accuracy figure if the gamma curve is way off for instance. A good factory calibration requires all 3 to be well set up. We have deliberately not included luminance in this comparison since this is normally far too high by default on every screen. However, that is very easily controlled through the brightness setting (on most screens) and should not impact the other areas being measured anyway. It is easy enough to obtain a suitable luminance for your working conditions and individual preferences, but a reliable factory setup in gamma, white point and colour accuracy is important and not as easy to change accurately without a calibration tool.

 

From these comparisons we can also compare the calibrated colour accuracy, black depth and contrast ratio. After a calibration the gamma, white point and luminance should all be at their desired targets.

 

 

Default setup of the screen out of the box was decent enough and gamma and white point were pretty close to their targets. It is too bright of course, but that's easy to turn down via the brightness setting.

 

 

 

The display was a little bit weak when it came to black depth and contrast ratio. We would have liked a contrast ratio a bit closer to 1000:1 for a modern TN Film panel although it was only slightly lower than a lot of other recent models we'd tested to be fair (e.g. Asus PG278Q 858:1).

 

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Viewing Angles

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

Viewing angles of the U28D590D were as you might expect from a TN Film panel. Unfortunately this panel technology is inherently poor in this field, and so viewing angles are more restrictive than other competing technologies like IPS, PLS and VA. Although the manufacturer will quote a viewing angle of 170 / 160 (a classic indication that a TN Film panel is being used by the way if in doubt), in practice there are some obvious contrast and colour tone shifts horizontally, and especially vertically.

As you move your head from side to side in a horizontal plane, there is a contrast shift and the image becomes lighter and more washed out, and introduces a slight yellow hue. As you move to a wider angle the image can become more washed out as well. Vertically the fields of view are more restrictive still. From above the image becomes pale and washed out, while from below there is a characteristic TN Film darkening of the image. Unfortunately vertically the viewing angles will introduce noticeable shifts in the contrast and colour tone of the image which mean that for any colour critical work it is not really very well suited. TN Film panels have long suffered from these restrictive viewing angles due to the nature of their pixel structure. They are still fine for a single user for general use and certainly the TN Film panels offer their advantages when it comes to pixel response times and refresh rate for gaming. If however, you were hoping to do any colour critical or photography work you may find these shifts in the appearance of the image difficult. An IPS panel would probably be a wiser choice if you were looking for a screen with much wider viewing angles. However, the use of a TN Film panel here is really how manufacturers like Samsung have kept the cost of these 28" 4k resolution screens down. You have to make some sacrifices if you want a lower cost 4k screen at the moment.

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

On a black image there is a pale grey tint introduced to the image when viewed from a wide angle. This appears a little yellow at the furthest points. This isn't too severe and shouldn't present any real problems in practice. Certainly not the obvious white glow you get from most modern IPS panels in similar situations and fairly standard for a TN Film panel.

Panel Uniformity

We wanted to test here how uniform the brightness and colour temperature was across the screen, as well as identify any leakage from the backlight in dark lighting conditions. Measurements of the luminance and colour temperature were taken at 35 points across the panel on a pure white background. The measurements for luminance were taken using BasICColor's calibration software package, combined with an X-rite i1 Display Pro colorimeter with a central point on the screen calibrated to 120 cd/m². Measurements for colour temperature (white point) were taken using BasICColor software and the i1 Pro spectrophotometer which can more accurately measure the white point of different backlighting technologies. The below uniformity diagram shows the difference, as a percentage, between the measurement recorded at each point on the screen, as compared with the central reference 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 screen was moderate. The upper and lower parts of the screen showed a fairly marked drop in luminance, down to a minimum of 94 cd/m² (-27% deviance) which was significant. It was only the bottom most edge where the maximum deviance was shown. The central areas of the screen were more uniform compared with a centrally calibrated 120 cd/m². For colour critical work or viewing content with a lot of solid colour, this variation across the panel would be problematic, but for normal uses and things like gaming it didn't really cause any 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 was no obvious backlight bleeding detectable to the naked eye at all. Some slight clouding was evident along the left and right hand areas, but it was very slight and hard to pick out in the photo above as well. No real issues here with backlight bleed.

 

General and Office Applications

The U28D590 is an interesting way to offer a massive 3840 x 2160 4k resolution while maintaining a reasonable cost for the user. A lot of 4k res screens have been very expensive, but these new TN Film panel models are more affordable, and making many people consider 4k as a logical step in monitor evolution. You do need to keep in mind the need for a compatible graphics card with a suitable output which can handle this resolution, and preferably at 60Hz refresh rate. DisplayPort is the only option to run the screen at its native 3840 x 2160 res at 60Hz, so is certainly recommended.  When running at native resolution this model is recognised as a single display which makes life easier than some of the early MultiStream (MST) 4k models. It's also good to see support for 60Hz refresh rate as some competing models only offer 30Hz support which is very limiting, even in day to day uses (certainly for gaming!).

So how is this 4k resolution for office work? We found the text size and pixel pitch a little too small when we tested the 31.5" sized Dell UP3214Q and so on this 28" sized screen it is even more of an issue. Honestly we just found the text size far too small for any kind of office work. Text is absolutely tiny with only a 0.16mm pixel pitch. Users need to be aware of this we think, in an age of "retina displays" and the likes, bigger resolution does not necessarily equal a better viewing experience. If you run the screen at native resolution without any alterations to the picture settings, be prepared for very tiny fonts and text! Obviously there are ways around this like increasing the DPI setting in Windows. This serves to make fonts and texts bigger, and then the added resolution of the panel provides crisp and sharp images. However, not everything scales properly, and we found it a bit troublesome with a lot of applications and formatting on websites. The other option is to run the screen at a lower 2560 x 1440 resolution but then the image has to be scaled and you lose a lot of the clarity and sharpness. It doesn't look then as good as a native 2560 x 1440 panel. We remain unconvinced by the practical usage of such high resolutions on desktop monitors for normal office type uses. Cramming that same resolution into a 24" screen like the Dell UP2414Q is surely going to be even more problematic?!

As a side note, we can of course see there is a benefit in having a 4k resolution for some other uses. 4k video content, picture viewing, and any work with particularly high resolution content will of course benefit from the sharpness and resolution this panel can provide. Any games which can support super high resolutions will also look excellent and with an additional layer of detail offered by such a tight pixel pitch. In this section though we are focusing on every day type uses and office work, and we just feel users need to be aware of how a screen like this will look in real life.

The moderate AG coating of the TN Film panel is not a big issue and doesn't produce any major graininess to the image like some aggressive AG solutions can. It is however not semi-glossy or "light" so there is some graininess evident on white backgrounds in office applications. The limited viewing angles of the TN Film panel technology are perhaps the screens main weakness from a panel technology point of view, meaning that you will notice colour and contrast shifts if you deviate from a head on view of the screen. This may be problematic if you are doing any colour work, or trying to view content from different positions. The default setup was decent enough with a reliable white point and pretty good gamma setup.

The brightness range of the screen was also very good, with the ability to offer a luminance between a very high 362 and a nice and low 14 cd/m². This should mean the screen is perfectly useable in a wide variety of ambient light conditions, including darkened rooms. A setting of ~22 in the OSD brightness control should return you a luminance close to 120 cd/m². The backlight regulation is controlled without the need for PWM for settings between 100 and 31%. However, this doesn't allow you to get down to a low enough setting for comfortable 120 cd/m² usage. Once you drop below 31% brightness a 240Hz PWM frequency is introduced which may be problematic to some users. It's a shame the brightness control didn't reach lower before you had to enter the PWM-zone. There was no audible buzzing from the screen, even when specifically looking for it using test images with a large amount of text at once. The screen remains cool even during prolonged use. There are no specific preset modes offered by this screen for office use so you will have to adjust the standard or custom mode to your liking.

There are no real extras offered by the screen like USB ports, ambient light sensors, human motion sensors, card readers or integrated speakers. The stand is also very limited with only a basic (and stiff) tilt adjustment provided.

 
Above: photo of text at 3840 x 2160 (top) and 2560 x 1440 (bottom)

The screen is designed to run at its native resolution of 3840 x 2160 (4k) 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 2560 x 1440 resolution to see how the screen handles the interpolation of the resolution, while maintaining the same aspect ratio of 16:9. At native resolution the text was very sharp and small as we've already discussed. Looking at the macro photos there seemed to be some slight overlap of the text across pixels but the image is so small that you couldn't notice any sharpness problems with the naked eye at all. When running at a 2560 x 1440 resolution the font size is far more comfortable but you do lose a lot of the sharpness and the fonts look blurry.

Responsiveness and Gaming

The U28D590D is rated by Samsung as having a 1ms G2G response time which indicates the panel uses overdrive / response time compensation (RTC) technology to boost pixel transitions across grey to grey changes. There is user control over the overdrive impulse within the OSD menu using the 'overdrive' option. The part being used is the Innolux M280DGJ-L30 TN Film panel. Have a read about response time in our specs section if you need additional information about this measurement.

We will first test the screen using our thorough response time testing method. This uses an oscilloscope and photosensor to measure the pixel response times across a series of different transitions, in the full range from 0 (black) to 255 (white). This will give us a realistic view of how the monitor performs in real life, as opposed to being reliant only on a manufacturers spec. We can work out the response times for changing between many different shades, calculate the maximum, minimum and average grey to grey (G2G) response times, and provide an evaluation of any overshoot present on the monitor.

We use an ETC M526 oscilloscope for these measurements along with a custom photosensor device. Have a read of our response time measurement article for a full explanation of the testing methodology and reported data.
 

Overdrive Setting Comparison

First of all we carried out a smaller sample set of measurements in each of the three 'Response Time' settings. These, along with various motion tests allowed us to quickly identify which was the optimum overdrive setting for this screen.

First we tested the screen with the overdrive option set to 'standard'. Response times were slow with an average of 14.1ms G2G being measured. There was no overshoot at all as overdrive was not being used, but response times were too slow and it resulted in a lot of noticeable blurring in practice. Rise times were particularly problematic with 18.6ms on average.

Transition: 0-50-0 (scale = 20ms) @ 60Hz

If we take a closer look at an example transition from 0-50 we can see why the rise times were particularly slow. The measured 19.3ms response time here (0-50) is because there seems to be a step in the brightness curve as it tries to reach the desired brightness level (50). As a reminder, the lower flat line represents the darker shade of the transitions (0), and the upper flat(ish) line represents the lighter shade of the transition (50). It seems that the brightness only reaches part of the way towards the required level, and has a defined "step" before it then changes brightness again to reach the desired level. If you look at that time it takes for the step to complete, before the brightness starts to increase again up towards the desired level, it is 16.667ms, which equates to 1 frame at 60Hz refresh rate. This is the cause for the slow rise times here. On the other hand, the fall time from 50-0 is very fast indeed, measuring only 1.1ms. There is no apparent 'stepping' of the brightness curve in this example. We've seen this same behaviour on other modern TN Film panels like the BenQ XL2720Z and Asus ROG Swift PG278Q.
 

With overdrive now switched up to the 'Faster' mode, response times had improved quite nicely, with an average now of 7.2ms G2G measured. There was still no overshoot at all, so there seemed to be no side-effects to using this mode. Some of the slower rise times had been sped up now, although some changes to the brighter shades were still quite slow. Rise times on average were slower (10.8ms) than fall times (3.6ms). This was definitely a marked improvement in response times though over the 'standard' mode, confirmed also with subjective observations as well.

The final 'Fastest' overdrive setting boosted the response times quite a lot further. We now had a very impressive G2G response time average of only 2.4ms. Some transitions reached down to the advertised 1ms G2G even which means the screen is capable of living up to its spec. However, some significant overshoot was introduced on most transitions which was very noticeable in practice. This level of overshoot is far too much and makes this mode unusable. Stick with the 'faster' mode for the optimum balance.

Transition: 0-50-0 (scale = 20ms) @ 60Hz

An example of the overshoot is shown above (79.3%).

If we take some test photos using the PixPerAn tool you can make some further visual comparisons between the overdrive settings. With overdrive off the slow response times lead to a pronounced blur to the moving image in practice which you can easily see. Turning the setting up to Standard brings some improvement in visual appearance. The blur is reduced noticeably and the moving image becomes sharper. The response times aren't as fast as we have seen from some TN Film panels so blurring is a little more apparent, but there is no overshoot evident at all so no trade-off is needed when using this mode. The 'fastest' mode shows a very obvious dark and pale trail because of the overshoot of the response times and should be avoided.

 

More Detailed Measurements - Overdrive = Faster

Having established that the Response Time 'Faster' mode seemed to offer the best response/overshoot balance we carried out our normal wider range of measurements as shown below:

The average G2G response time was more accurately measured at 7.0ms which was pretty good overall. Some transitions were as fast as 1.1ms, pretty much meaning it lives up to its spec. However, it is the average G2G figures which you need to consider here. Rise times were notably slower than fall times with a 10.1ms average. A few particularly troublesome transitions were to blame for some of this, where response time was slow (e.g. 0-200 = 18.8ms).

There was pretty much no overshoot as well in this overdrive mode, with only a couple of transitions showing anything at all, and even then, very low. The overdrive impulse was being applied well and in a controlled fashion which was pleasing.

Display Comparisons

The above comparison table and graph shows you the lowest, average and highest G2G response time measurement for each screen we have tested with our oscilloscope system. There is also a colour coded mark next to each screen in the table to indicate the RTC overshoot error, as the response time figure alone doesn't tell the whole story.

The response time performance of the U28D590D was decent overall, but a little slow really for a modern TN Film panel. With an average G2G response time of 7.0ms, it fell behind gaming models like the Asus ROG Swift PG278Q (2.9ms) and BenQ XL2720Z (3.8ms) by a fair amount. The slower rise times on the Samsung were to blame here, as fall times were very fast.  There was basically no overshoot on the Samsung though, whereas some minor issues were introduced on the BenQ and Asus models where the overdrive impulse is more aggressive to squeeze more out of the response times.

Despite not being as fast as some higher end gaming displays, the response times were still a bit faster than the best IPS models. Screens like the Dell U2414H and P2414H (both 8.9ms G2G average) represent about as fast as you can get from a modern IPS-type panel, without introducing lots of nasty overshoot. The Samsung felt faster in practice as well and TN Film technology is generally a better choice for gaming.

 

The screen was also tested using the chase test in PixPerAn for the following 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 comparison between different screens and technologies as well as a means to compare those screens we tested before the introduction of our oscilloscope method.

28" 1ms G2G Innolux TN Film (Overdrive = Faster)

In practice the Samsung U28D590D performed best with the Overdrive setting on 'Faster'. There was still some low levels of blurring to the moving image but nothing too noticeable. Thankfully there was very no overshoot introduced in this mode which was excellent.

28" 1ms G2G Innolux TN Film (Overdrive = Faster)

27" 4ms G2G AU Optronics AHVA (AMA Setting = High)

27" 8ms G2G LG.Display AH-IPS

27" 5ms G2G Samsung PLS (Trace Free = 40)

27" 12ms G2G Samsung PLS (Response Time = Advanced)

Firstly it is interesting to compare the U28D590D to some of the popular 27" models we have tested with 2560 x 1440 resolutions and IPS-type panels (IPS, PLS and AHVA). You can see first of all a comparison against the BenQ BL2710PT which shows a quite comparable performance to the Samsung in these tests, with slightly higher levels of blur and no overshoot issues. The Dell U2713HM was a bit faster than the BenQ and eliminated a lot of the visible blurring, but also remained free from overshoot which was a bonus. It was very close really to the Samsung in responsiveness. The Asus PB278Q was again similar, and although it showed a little dark overshoot it was very slight. The ViewSonic VP2770-LED was more comparable to the Samsung in visible blurring as well.

 

28" 1ms G2G Innolux TN Film (Overdrive = Faster)

27" 1ms G2G AU Optronics TN Film @ 144Hz (OD = Normal)

27" 1ms G2G AU Optronics TN Film + 144Hz (AMA = High)

23.5" 4ms G2G Sharp MVA + 120Hz

We've also included a comparison above against 3 very fast 120Hz+ compatible screens we have tested. The other screens shown here are all aimed primarily at gamers and have various features and extras which make them more suitable overall for gaming. Firstly there is a comparison against the Asus ROG Swift PG278Q with its 144Hz refresh rate and fast response time TN Film panel. This showed very fast pixel response times and smooth movement thanks to its increased refresh rate. You are able to reduce the motion blur even more through the use of the ULMB strobed backlight as well if you need to. In other related areas this screen also supports NVIDIA's G-sync technology. There was some slight overshoot noticeable on the Asus but nothing major.

Then there is a comparison against the BenQ XL2720Z with another very fast TN Film panel and 144Hz refresh rate. This showed very low levels of motion blur, but some dark overshoot was introduced as a side-effect as you can see. This screen even includes a native Blur Reduction mode to help eliminate further perceived motion blur.

Lastly there is the MVA based Eizo FG2421 screen with a fast response time (especially for the panel technology being used) and 120Hz refresh rate support. There is also an additional 'Turbo 240' motion blur reduction mode which really helps reduce the perceived motion blur in practice.

While these pixel response tests from PixPerAn give one view of the performance of the panel, there is something else going on as well here which can't be picked out by the camera. All of these other gaming models are running at 120Hz (or higher) refresh rates, which allows for improved 120fps+ frame rates and in some cases the support of 3D stereoscopic content as well. This can really help improve smoothness and the overall gaming experience so these screens still have the edge when it comes to fast gaming. Any additional extras to reduce perceived motion blur can also have a real benefit in practical terms, and again not easy to pick out with this camera method.

The overall gaming performance of the Samsung U28D590D was decent enough overall. Response times were not as fast as some gaming TN Film panels but they were certainly more than adequate, and freedom from any overshoot issues was a big bonus. The screen can support 60Hz refresh rate over DisplayPort which is excellent, as some screens are limited to 30Hz which could really be a problem in games.

Important 4k Consideration - one big consideration you need to make is that the 3840 x 2160 resolution is likely to be a major drag on even high end graphics cards and PC systems when it comes to gaming. You really need to think about the type of game you want to play, the settings you want to use, and whether your system can handle outputting such a high resolution effectively. Don't forget that many gaming titles don't support this resolution either, so that could be another issue. Those that do can present further problems as well when it comes to the user interface as lack of scaling results in tiny text or hard to read maps etc. One option of course is to run the game at a lower resolution and let the screen scale it. That's probably the most sensible option in most cases but kind of defeats the point of having a 4k resolution in the first place. If you have games which can natively support this resolution properly, they would look fantastic given the very high resolution and small pixels.

If gaming is really your priority you may want to consider some of the more gamer orientated 120Hz+, TN Film based compatible displays out there, or perhaps something like the Eizo FG2421. Even better still would be models equipped with LightBoost systems or other motion blur reduction backlights for optimum motion blur elimination.
 

Additional Gaming Features

Aspect Ratio Control - The U28D590D has two options for aspect ratio control through the OSD 'screen' menu, using the 'image size' option. There are options for 'auto' and 'wide'. Auto will maintain the aspect ratio of the source, although it doesn't do 1:1 pixel mapping and instead stretches the image to fill as much of the screen as possible. The wide option will stretch the source content to fill the screen in a 16:9 format no matter what its native aspect is.

Preset Modes - There is a specific 'game mode' available in the OSD which just seems to over-saturate and over-sharpen the image.

Lag

We have written an in depth article about input lag and the various measurement techniques which are used to evaluate this aspect of a display. It's important to first of all understand the different methods available and also what this lag means to you as an end-user.

Input Lag vs. Display Lag vs. Signal Processing

To avoid confusion with different terminology we will refer to this section of our reviews as just "lag" from now on, as there are a few different aspects to consider, and different interpretations of the term "input lag". We will consider the following points here as much as possible. The overall "display lag" is the first, that being the delay between the image being shown on the TFT display and that being shown on a CRT. This is what many people will know as input lag and originally was the measure made to explain why the image is a little behind when using a CRT. The older stopwatch based methods were the common way to measure this in the past, but through advanced studies have been shown to be quite inaccurate. As a result, more advanced tools like SMTT provide a method to measure that delay between a TFT and CRT while removing the inaccuracies of older stopwatch methods.

In reality that lag / delay is caused by a combination of two things - the signal processing delay caused by the TFT electronics / scaler, and the response time of the pixels themselves. Most "input lag" measurements over the years have always been based on the overall display lag (signal processing + response time) and indeed the SMTT tool is based on this visual difference between a CRT and TFT and so measures the overall display lag. In practice the signal processing is the element which gives the feel of lag to the user, and the response time of course can impact blurring, and overall image quality in moving scenes. As people become more aware of lag as a possible issue, we are of course keen to try and understand the split between the two as much as possible to give a complete picture.

The signal processing element within that is quite hard to identify without extremely high end equipment and very complicated methods. In fact the studies by Thomas Thiemann which really kicked this whole thing off were based on equipment worth >100,1000 Euro, requiring extremely high bandwidths and very complicated methods to trigger the correct behaviour and accurately measure the signal processing on its own. Other techniques which are being used since are not conducted by Thomas (he is a freelance writer) or based on this equipment or technique, and may also be subject to other errors or inaccuracies based on our conversations with him since. It's very hard as a result to produce a technique which will measure just the signal processing on its own unfortunately. Many measurement techniques are also not explained and so it is important to try and get a picture from various sources if possible to make an informed judgement about a display overall.

For our tests we will continue to use the SMTT tool to measure the overall "display lag". From there we can use our oscilloscope system to measure the response time across a wide range of grey to grey (G2G) transitions as recorded in our response time tests. Since SMTT will not include the full response time within its measurements, after speaking with Thomas further about the situation we will subtract half of the average G2G response time from the total display lag. This should allow us to give a good estimation of how much of the overall lag is attributable to the signal processing element on its own.

 

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.

We have provided a comparison above against other models we have tested to give an indication between screens. The screens tested are split into two measurements which are based on our overall display lag tests (using SMTT) and half the average G2G response time, as measured by the oscilloscope. The response time is split from the overall display lag and shown on the graph as the green bar. From there, the signal processing (red bar) can be provided as a good estimation.

The screen showed a total average display lag of 39.0 ms as measured with SMTT 2. Taking into account half the average G2G response time at 3.5ms, we can estimate that there is ~35.5 ms of signal processing lag on this screen. This is high and could present problems for anyone sensitive to lag, or playing fast FPS games.

 

Movies and Video

The following summarises the screens performance in video applications:

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

• 16:9 aspect ratio is more well suited to videos than a 16:10 format screen, leaving smaller borders on DVD's and wide screen content at the top and bottom.

• 3840 x 2160 resolution can support full 1080 HD resolution content. It can also support 4k content.

• Digital interface support HDCP for any encrypted and protected content

• 2x HDMI and DisplayPort connections available. Nice to see 2x HDMI connectivity included for modern DVD players, Blu-ray, consoles etc.

• Cables provided in the box for (x1) HDMI and DisplayPort.

• Moderate AG coating provides reasonably clear images with no major graininess, and without the unwanted reflections of a glossy solution. Some graininess apparent as with other TN Film panels, but shouldn't present a problem in movies.

• Wide brightness range adjustment possible from the display, including high maximum luminance of ~362 cd/m² and an excellent minimum luminance of 14 cd/m². This should afford you very good control for different lighting conditions. Contrast ratio remains stable across that adjustment range as well and is reasonable for a TN Film panel. Brightness regulation is controlled without the need for PWM and so is flicker free between settings of 100 and 31% brightness, allowing you to reach down to ~158 cd/m² before you need to enter the PWM-zone. For very low lighting conditions the use of a low frequency 240Hz PWM below 30% brightness may present some problems.

• Black depth and contrast ratio are reasonable for a TN Film panel at 797:1 after calibration. Detail in darker scenes should not be lost as a result.

• There is no specific 'movie' preset mode available for movies or video.

• Good pixel responsiveness which can handle fast moving scenes in movies without issue. No real overshoot issues which is good news.

• Viewing angles are limited due to the use of TN Film panel technology. May cause issues with gamma and contrast shift if you change your line of sight or have several people trying to see the screen at once. Not really an ideal technology for movies as a result of this viewing angle limitation.

• No noticeable backlight leakage which is good, even in darkened room conditions.

• Very limited range of ergonomic adjustments available from the stand, with only a basic and stiff tilt adjustment offered. May present problems when viewing the screen from different positions.

• No integrated stereo speakers on this model, but there is an audio out jack if sending sound to the screen over HDMI.

• Decent enough range of hardware aspect ratio options available which is very useful for external devices.

• Picture in picture (PiP) and Picture By Picture (PbP) are available on this model.
  
   

Conclusion

The Samsung U28D590D was an interesting first test for us of one of the new 28" 4k screens on the market. It's clear to see why these relatively affordable screens are attracting a lot of interest as the jump in resolution and support for 4k content is a big selling point and a significant evolution in the monitor market. The U28D590D is a good option compared with a lot of its competition since it has an attractive design, decent input options, is detected as a single screen (not using MST) and supports 60Hz refresh rate which in our view is vital. The screen offered a decent enough default setup, reasonable contrast ratio and pretty fast response times which were pleasing. Of course, the screen is limited in some areas by its TN Film panel technology, a measure required at the moment to allow retail costs to be as low as they are. Viewing angles remain a noticeable weakness of the technology of course. We were disappointed by the high lag of this screen as well, as although response times were pretty decent, this could be a bit of an issue for  competitive gaming.

Samsung could have done better with the stand we felt, as it was very limited, stiff and the screen was wobbly. VESA support would have been nice too. The screen does feel a bit no-frills as well, as there's no extra USB ports or anything. There are at least some decent connectivity options, the design is nice, and the joystick control for the OSD is a nice touch. The PWM-free backlight between 100 and 31% brightness was pleasing, but it was a shame that you could not reach low enough luminance without needing to enter the PWM-zone below that. It might have been better to have a completely PWM-free backlight for all adjustments.

We were left unconvinced by the 4k resolution though if we're honest. That kind of resolution is just too high by default on many systems on a screen this size for day to day work. If you've got an actual requirement for 4k support for video, imaging or high resolution work (CAD/CAM) then it is of course very impressive. The detail and sharpness provided is excellent. If you're wanting to use it for normal day to day uses though the pixel pitch is tiny and really fonts become too hard to see. Make sure you understand the limitations of 4k as opposed to assuming that bigger is better, but if you do decide you want a well-priced 4k display, this is a decent choice on the most part.

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