Introduction

Out of their pretty extensive range it has been Dell's UltraSharp monitors which has always attracted the most attention over the years, with a great selection of sizes available, featuring high end panel technologies, specs and features. We've seen a lot of excitement when a new U-series screen arrives, most recently with the release of the 27" U2713HM and the news that we expect to see a refreshed 24" U2413 and 30" U3013 model some time early next year. The rest of Dell's extensive monitor line-up is normally reserved for lower cost models, with trimmed down feature sets and normally lower cost TN Film panels. However, recently Dell have released their new S-series range (the "S" stands for "Studio" by the way), offering models of 21.5, 23, 24 and 27". Unlike their other lower cost models, these all feature higher end IPS (or AMVA in the case of the 24" model) panels and so are designed to be a mid-way solution, offering some higher end specs and technologies but while still maintaining a very low cost.

We have already completed a thorough review of the 24" S2440L model and now have the 27" S2740L screen with us for testing. This model features a 1920 x 1080 resolution AH-IPS panel and while it offers a very similar design to the S2440L, it does offer a few extra nice features which we will discuss throughout the course of the review. Like the 24" model it comes with a "frameless" edge-to-edge glossy glass front which some users have been shouting out for from more desktop monitors.

Dell's website says: "Get a front-row seat with the sophisticated S2740L 27" monitor, featuring ultra-wide viewing, edge-to-edge glass and our Image Enhance feature. Images come alive with color-boosting Image Enhance, ultra-wide viewing and Full HD resolution (1920 x 1080 max.) in a 16:9 widescreen format. Connect to a laptop or desktop with VGA and DVI-D (HDCP). Explore HD viewing options with HDMI. Connect to devices with two USB ports."

Specifications and Features

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

Manufacturers website link: Dell

The feature set of the S2740L is more limited than the popular UltraSharp models available. On the 24" model there was only 1x D-sub (VGA) and 1x HDMI connections available for video connectivity, but here a DVI-D is also available which is good news. There is however no DisplayPort connection which is becoming increasingly popular nowadays. There is an audio out connection on the back of the screen if you want to listen to the sound sent over HDMI (if using HDMI end to end), but there are no integrated speakers on this model. The digital interfaces support HDCP for encrypted content. There is also a 2 port USB 2.0 hub included on which is nice to see included, and something which was left off the 24" model. These are located on the back of the screen so not the easiest to access, but at least they are there and may be handy to some users.

The screen comes packaged with only a D-sub VGA cable, and there is no DVI or HDMI cable provided since costs are being kept at a minimum here. The USB cable is included though. The screen features an external power supply brick which comes packaged as well. There are no extra features here like card readers for instance which are featured on some older UltraSharp models from Dell.

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

OSD Menu

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

 

Power Consumption

In terms of power consumption the manufacturers spec states typical usage of 21W. In standby the screen apparently uses <0.5W.

We tested this ourselves and found that out of the box the screen used 22.8W of power while at its default brightness setting which was 75%. At the lowest brightness setting, power consumption was reduced to 10.7W and at maximum 100% brightness it reached 27.0W. After calibration the brightness setting had been adjusted to 43% and the power consumption was measured at 17.9W. In standby the screen used 0.7W of power. We have plotted these measurements on the graph below for comparison with other screens:

Panel and Backlighting

Panel and Colour Depth

The Dell S2740L utilises an LG.Display LM270WF5-SLB1 AH-IPS panel which is capable of producing 16.7 million colours. This is achieved through the use of a 6-bit panel with Advanced Frame Rate Control (AFRC). This is the latest generation of so-called AH-IPS panel from LG.Display although in reality it is unclear what really makes these AH-IPS generation panels any different to the older H-IPS (and e-IPS) variants. So far we have seen these new generation panels used in the Dell U2713HM, NEC P232W and AOC i2757Fm and have been pleased to find that the AG coating had been noticeably reduced. Of course here on the Dell S2740L there is no AG coating used at all, and the panel offers a glossy finish with an added glass layer on the front of the screen for protection. The panel is confirmed when dismantling the screen as shown below.

 
Above: dismantled screen. Click for larger versions
 

Panel Coating

The screen coating on the S2740L is a glossy solution as we had seen on the 24" version before. The panel surface itself is glossy which you can see if you dismantle the monitor as it has no protective coating applied to it. To the front of the screen an edge-to-edge glass layer is added which increases the overall glossy feel of the screen and provides protection for the panel. This is very reflective, more so than some other glossy coated screens we have seen before. Users need to be careful when selecting a screen like this as windows, lighting or lamps can become problematic depending on your working conditions. Smudges and finger prints may also prove troublesome.
 

Backlighting and Colour Gamut

The S2740L uses White-LED (W-LED) backlighting producing a colour space approximately equal to the sRGB reference. This means the screen is considered a 'standard gamut' backlight type. The gamut would cover approximately 72% of the NTSC reference space. A wide gamut screen would need to be considered by those wanting to work outside of the sRGB colour space of course.
 

PWM Flicker Tests at Various Backlight Brightness Settings

100%                                      50%                                         0%

We tested the screen to establish the methods used to control backlight dimming. Our recent article talks in more details about a common method used for this which is called Pulse Width Modulation (PWM). A series of photos was taken using the method outlined in the article. These were taken at 100%, 50% and 0% brightness settings. These tests allow us to establish 1) whether PWM is being used to control the backlight, 2) the approximate frequency at which this operates, and 3) whether a flicker may be introduced or potentially noticeable at certain settings.

A thin white line was shown on an all-black background and a photograph was taken at a slow shutter speed of 1/8 second (in this example) as the camera was scanned left to right in front of the screen. This produces a series of white lines which can be used to identify the frequency of the PWM and how quickly the backlight is cycled on and off. The higher this 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. Please remember that not every user would notice a flicker from the backlight 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. We are able to at least measure the frequency of the backlight using this method and tell you whether the duty cycle is sufficiently short at certain settings that it may introduce a flicker to those sensitive to it.

Interestingly the Dell S2740L does not use PWM at all for dimming of the backlight. Even at 0% brightness there was no sign of the usual splitting of the white line that you'd expect to see in these tests. We carried out the checks at an even slower shutter speed which returned the same result. This is great news for those who are affected by flickering backlights and suffer from eye fatigue and eye strain. It seems we have seen quite a few new monitors recently which don't use PWM for backlight dimming including the smaller 24" S2440L in fact. The HP ZR2740w, DGM IPS-2701WPH, ViewSonic VP2770-LED, Samsung S27B970D and Dell U2713HM also spring to mind as other models which do not use PWM which we have tested recently.

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 Performance and Setup

IMPORTANT NOTE: Before we get into this section we need to make an important note about use of the HDMI port if you choose to use that for connectivity. The screen features a couple of options you can use, including DVI, VGA and HDMI. You will probably want to use the DVI port for PC connectivity, but if you wanted to use HDMI instead you need to take note of the following. If you have an NVIDIA graphics card and want to use the HDMI at all, whether a straight HDMI > HDMI connection or a DVI > HDMI conversion, you need to make a change to your graphics card settings to display the optimum picture. This is because by default the output range over HDMI is limited by the graphics card, and it can greatly limit the picture quality and in particular the black range and contrast ratio.

When connected via HDMI on an NVIDIA graphics card the screen by default will not look right, and the black range in particular is poor. A change is needed via your graphics card to ensure a full 0 - 255 output when using HDMI, rather than it being limited to a smaller output range of 16 - 235. This applies to NVIDIA cards but is only necessary when connecting to the HDMI port on the screen and is not needed when using D-sub or DVI. A similar change might be required when using an AMD graphics card but the setting is built into their graphics card drivers we believe. For NVIDIA cards the simplest way to ensure a full output range is to use the handy toggle utility available here. If you run the program you can select a full 0- 255 range quickly and easily.

Anyway, default settings of the screen were as follows:

Dell S2740L - Default Factory Settings

    

The default set of the screen felt ok to the naked eye, perhaps a little cool, and as is normal for most screens it was too bright for comfortable use. Some grey shades felt a little green/blue in practice suggesting the balance was not quite right. Colours appeared to 'pop' somewhat because of the glossy screen coating and it felt different to models using AG coating.

In terms of measurements, the CIE diagram on the left confirms that the monitors colour gamut (black triangle) matches the sRGB colour space (orange triangle) very closely. It extends a little past the sRGB space in some green shades, but falls a slightly short in reds in this 2D view of gamut. Overall a good match to the sRGB colour space thankfully.

Default gamma was measured at 2.3 average, leaving it 6% out from the target of 2.2. This was too high particularly in darker shades as shown in the more detailed table above. The white point was measured at 7011k, being 8% out from the target of 6500k which wasn't too bad, but a bit cool. Colour accuracy was reasonable with an average dE of 2.7 and maximum of 6.5. Colour gradients showed very smooth transitions in all shades, and at the darker end there was some slight gradation evident. Luminance was too high as we had suspected, being measured at 194 cd/m² by default while at the 75% brightness setting. We achieved a reasonable static contrast ratio of 813:1 by default which was a bit lower than we had perhaps hoped based on recent tests of IPS panels.

As a side note we also tested the default set up when reverting to the 'custom color' mode. This returned very similar results to the above, although the screen was a bit brighter at ~240 cd/m². The colour temperature was also a bit closer to the target, being measured at 6824k and being 5% out now. Perhaps a better starting point out of the box for that slightly better white point. You will want to turn down the brightness control no matter which preset you use we suspect.

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.

I reverted to the 'custom color' mode in the preset section of the OSD menu which would allow me access to the individual RGB channels. Adjustments were also made during the process to the brightness control, and to the RGB channels as shown in the table above. This allowed me to obtain an optimum hardware starting point and setup before software level changes would be made at the graphics card level which would help preserve tonal values. After this I let the software carry out the LUT adjustments 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.

Average gamma had been corrected to 2.2 with 0% deviance according to the initial test correcting the default 6% deviance we'd found in this preset. The 8% deviance in the white point from our target of 6500k had also been corrected here and the colour temperature was now pretty much spot on at 6511k. Luminance had also been corrected thanks to the adjustment to the brightness control, now being measured at 120 cd/m² as intended. This gave us a calibrated black depth of 0.17 cd/m², and a moderate calibrated static contrast ratio of 691:1. Colour accuracy had also been corrected nicely, with dE average of 0.4 and maximum of 0.9. LaCie would consider colour fidelity to be excellent now overall.

Testing the screen with various colour gradients showed smooth transitions. There was some slight gradation in darker tones but no visible banding thankfully. Unlike most other panels in the market, this screen does not feature anti-glare (AG) coating. Instead it uses a glossy screen coating and as a result the colours look clean and crisp, the image quality is sharp and whites in particular look a lot more pure than they do on heavy AG coated screens like some of the IPS alternatives available. This can also help the colours and blacks 'pop' to the user. Glossy coating isn't to everyone's taste though as it can introduce reflections which are annoying, particularly so on this glass fronted model. You should probably try and see a glossy and an AG coated panel in person if you are unsure what to buy.

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 S2740L was reasonable when it comes to gamma and white point. There was a small 6% deviance in gamma and a slightly higher 8% deviance in white point. This represented a pretty good factory setup, much like we'd seen from the Dell S2440L in fact, as well as some of the UltraSharp Dell range like the U2312HM and U2412M. Colour accuracy was reasonable as well with dE average of 2.7, but this was not quite as good as the S2440L (1.8) in this area. Not a bad default setup and it was good to see an accurate coverage of the sRGB colour space as well. It would have been nice if the gamma and white point were slightly better perhaps but it was nothing too significant which should bother an average user.
 

Default colour accuracy is compared again on the above graph, with the S2740L having a reasonably reliable default setup which is pleasing, especially given the low cost of this model.

Once calibrated the dE average was reduced to 0.4. 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 at all. The professional range models from NEC and Eizo are even more accurate than other models shown here. Professional grade monitors like those 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.

The calibrated black depth and contrast ratio of the S2740L were ok, but not great by some modern IPS standards. At a contrast ratio of 691:1 it was pretty close to the 23" Dell U2312HM (710:1) and the 27" U2711 (672:1). It was not quite as good as some of the other recent Dell models like the 24" U2412M (947:1) and the 27" U2713HM (869:1) which was a little disappointing. The contrast ratio should be adequate for most uses though, we had just hoped for a little more from a modern IPS panel. The 24" S2440L of course was much better in this regard thanks to its AMVA panel, reaching 2954:1 contrast ratio. That is something which IPS technology cannot compete with at the moment and a real benefit of AMVA panel technology.

Contrast Stability and Brightness

The luminance range of the screen was good. At the top end the panel reached 231.23 cd/m² which was a little short of the specified maximum of 270 cd/m², but should be fine for most users as an upper limit. At the lower adjustment end it could reach down to a very low 40.27 cd/m² meaning the screen should be perfectly fine even in darkened room conditions, and for those who like to run at a lower luminance setting. A brightness setting of ~42% should return you a default luminance of around 120 cd/m² as well. Black point remained pretty low across the adjustment range, from 0.28 cd/m² down to below 0.05 cd/m².

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. This was a linear relationship overall.

Average contrast ratio measured was 808:1 which was ok for an IPS panel. It was pretty stable across the adjustment range with some small deviations, particularly at the lower end of the brightness scale.

Dynamic Contrast

We tested the DCR feature and you could immediately notice the screen getting much brighter when you first turn it on compared with the standard preset. You can observe the changes being made in the OSD by looking at the energy meter in the top right hand corner. Switching to this mode in normal office-type applications showed the energy bar fill up to maximum, indicating that the brightness was being turned up to a high setting. When switching between an almost all-white and an almost all-black screen there was hardly any change at all to the luminance of the screen. There was very little change detectable to the naked eye but you could see the energy bar go down by 3 bars in the OSD menu. This change took less than 1 second so was very quick. In these tests we didn't obtain a contrast ratio any higher than we'd seen from our static contrast ratio tests before, and in fact it was lower in practice at ~640:1. It was the same result in both the game and movie preset modes.

We tested the screen with a completely black screen as well and you could tell from the OSD energy meter that it was then able to control the backlight a lot more, down to the lowest 0% setting by the look of the energy bar. This change took around 3 seconds. This would in theory give you a better DCR of around 3700:1 but it should be noted that it would be extremely rare to ever see a 100% black image in real use and so this is more of a theoretical DCR than a realistic, practical DCR. Our tests of an almost all-black image are more realistic for actual use, and the DCR didn't offer us much there.

You'd have to be turning the backlight completely off on an all-black image to achieve anything higher than this though and to get anything near the crazy spec being quoted. Some screens do actually do that which allows for exaggerated laboratory testing and their resulting specs, but in the case of the S2740L it was not turning the backlight off. In normal use, the DCR is pretty much useless.

Viewing Angles

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

Viewing angles of the S2740L are very good and as you would probably expect from an IPS panel. Horizontally the fields of view were very wide and a gamma shift was only really introduced from a very wide angle where the image darkened. Vertically the gamma shift was a little more pronounced but overall the fields of view were very good. The panel was free from the off-centre contrast shift you would see from VA matrices and this is one of the reasons why IPS is so widely regarded as the panel technology of choice for colour critical displays. The panel of course offered far wider viewing angles than TN Film matrices which can be very restrictive, especially vertically.

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

On a black image, like many other IPS panels, there is a white glow when viewed from an angle. This is often referred to as "IPS Glow" and can often be mistaken for backlight bleed. In fact, it's a characteristic of IPS panels when viewed from an angle although remember this picture was taken in a darkened room and in normal working conditions this shouldn't present much problem. Given the large 27" screen size there is still the possibility some IPS glow noticeable from the corners as you look at the screen head on from a relatively close distance.

Panel Uniformity

We wanted to test here how uniform the brightness was across the screen as well as identify any leakage from the backlight in dark lighting conditions. First of all measurements of the 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 below 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 overall uniformity was very good here. There was a slight drop in luminance down to 104 cd/m² along the top right hand edge and the right hand side of the screen was a little darker than the left. Overall around 83% of the screen was within 10% deviance of the central 120 cd/m² measurement. A decent performance here really given the low cost of the screen.

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 some slight clouding of the backlight picked up in the top right hand corner of the screen, and a more pronounced section in the bottom left hand corner. To the naked eye, this wasn't really a problem and there were no significant issues.

General and Office Applications

Like the 24" model, the S2740L offers a variable performance when it comes to office work. Firstly the 1920 x 1080 resolution and 27" screen size give a nice decent area in which to work although the vertical resolution is a little less than 16:10 aspect ratio models (1920 x 1200). I think you notice this if you come from a 16:10 format screen. Also consider the fact that high resolution 27" 2560 x 1440 models are becoming increasingly available and so the difference in desktop size is certainly noticeable coming from a 27" screen like that to a lower resolution like the S2740L. Nevertheless, the 27" 1920 x 1080 resolution should be adequate for many users and a compromise many will make for the lower retail cost. It may of course also be more suited to some graphics cards and for those looking for a more multimedia orientated screen where their source inputs are lower resolutions anyway. The screen offered a 0.311mm pixel pitch which delivered easy to read text at least, although in my opinion does look a bit big on a 27" screen size. The The resolution is certainly big enough for side by side split screen working though which is good. If you have ever used a high resolution 2560 x 1440 model, the difference is quite pronounced in office applications and for desktop real-estate. It's not for everyone though and the screen was still perfectly useable here. Don't forget that the same 1920 x 1080 resolution is also featured on many smaller screens from sizes of 21.5" - 24". The 27" size of the S2740L may still be preferred by some for office work to give them a bigger font size which is a bit easier on the eye.

One area which raises questions here though is the glossy screen coating and glass front. While the screen might look attractive sat on the desk, it can become a little tricky to use in certain conditions. The glossy coating does help with the 'feel' of the images and colours and blacks can 'pop' when it is used by display manufacturers. However, reflections become quite a problem, and on the S2740L, like on the S2440L as well, the glossy-ness seemed to be quite severe. You need to be very careful about the position of your screen with your surrounding light sources, otherwise reflections become a pain. This might not be a problem for many users, and it's the same issue you'd face with any glossy screen really. For office work personally I found it a bit difficult. The other issue with the glass coating and the glossy plastics used elsewhere is with finger prints, dust and smudges.

The edge to edge design and flat front make the S2740L quite an interesting option for multi-screen set ups though as shown above. It's thin profile and VESA 100mm compatibility also allow for an attractive wall or arm mounting solution.

Default luminance of the screen is a too high at around 194 cd/m² at the default 75% brightness setting. You will probably want to turn this down to around 42% for a comfortable luminance around 120 cd/m². Those wanting to use the screen in low lighting conditions shouldn't have any issue here as the brightness control offers an excellent adjustment range, down to ~40 cd/m² in fact. The default colour, white point and gamma setup are pretty good thankfully so even without a colorimeter device you should be able to achieve decent performance from the screen easily. Another thing to note while we are talking about the brightness control is that the screen does not use Pulse-Width modulation (PWM) to control backlight dimming and so those who suffer from eye fatigue or headaches associated with flickering backlights need not worry here.

There is a specific preset mode for 'text' in the OSD menu which accentuates the sharpness of the image. This seems to enable the 'image enhance' feature (which is then greyed out) which in my opinion makes the text and image look too sharp and a bit unrealistic. The normal standard or custom color preset modes would be better, with image enhance left off. The default sharpness setting of 50 in the OSD also seemed optimal.

We tested the screen with both DVI and D-sub interfaces, and the DVI digital signal was a little sharper than VGA. You will want to use DVI (or HDMI) for the sharpest text and image where possible (making sure to adjust your graphics card settings if using an NVIDIA card and HDMI). A nice extra feature here is the 2x USB 2.0 port hub featured on this model. These were left off the 24" equivalent, but even though Dell are trying to keep costs down, they are a nice extra here. They can be pretty handy for connecting external devices, although these are located on the back of the screen and are perhaps not as easy-access as if they were on the side. The stand is very basic, offering only a tilt adjustment. While this is easy to use and offered a good range, the height, swivel and even rotate adjustments are missed I think for office uses and the screen is perhaps a little too low as a result.

 
Above: photo of text at 1920 x 1080 (top) and 1600 x 900 (bottom)

The screen is designed to run at its native resolution of 1920 x 1080 and at 60Hz refresh rate. If you want to you can run it outside of this and let the image be scaled to fill the screen. At the native resolution text was sharp and clear, albeit quite large on the 27" screen size. We ran the screen at 1600 x 900 which was the next step down, while still maintaining the screens 16:9 aspect ratio. Text was more blurred and you do take a hit in terms of resolution of course. To give you more desktop real estate and maximum picture quality, the native resolution is of course recommended where possible.

Responsiveness and Gaming

The S2740L is rated by Dell as having a 7ms G2G response time which implies the use of overdrive / response time compensation (RTC) technology. This is used to boost pixel transitions across grey to grey changes and improve responsiveness in practice, and reduce ghosting and blurring. The panel being used is an LG.Display AH-IPS LM270WF5-SLB1 module. It should be noted that unlike some other Dell screens, you cannot turn the overdrive control on and off from within the factory OSD and so we are reliant on Dell's setup here.

Display Comparisons

The screen was 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.

24" 7ms G2G LG.Display AH-IPS

In practice the Dell S2740L showed low levels of motion blur and no obvious ghosting. However, as a result of an aggressive overdrive impulse, there was a noticeable dark overshoot behind the moving object, which you can see in the photos above. There was also a slight pale halo produced but it was the dark overshoot which was most distracting. We have seen this from quite a few other Dell screens, including the 24" version. We are all in favour of improved responsiveness, but we'd like to see Dell sort out these artefacts from their overdrive circuitry really. We don't have the option on this model to turn the overdrive off in the factory OSD either.

24" 7ms G2G LG.Display AH-IPS

24" 6ms G2G AU Optronics AMVA

24" 8ms G2G LG.Display e-IPS

27" 8ms G2G LG.Display AH-IPS

We have provided first of all a comparison of the S2740L against 3 other Dell screens. We had seen some similar dark trailing on the 24" equivalent which is the S2440L, and also on the 24" U2412M which you can see from the above images. It is perhaps a little more obvious on the S-series screens but all three of these models seem to suffer from a poorly controlled overdrive impulse. You can eliminate that on the U2412M by turning the overdrive control off in the factory OSD, but at the cost of overall responsiveness. The 27" high resolution U2713HM showed a much better controlled overdrive impulse and in practice showed very little overshoot. It was certainly free from the obvious dark trails we see on the S-series models.
 

24" 7ms G2G LG.Display AH-IPS

27" 5ms G2G LG.Display AH-IPS (overdrive = medium)

27" 4ms G2G AU Optronics AMVA (AMA = Premium)

If we compare the S2740L against a couple of its more direct competitors we get the above results. The AOC i2757Fm is the closest screen we have tested to this Dell, being based on a similar version of the same LM270WF5 LG.Display AH-IPS panel. The AOC is actually rated with a 5ms G2G response time on paper, compared with the 7ms G2G of the Dell. In practice it showed a little more motion blur, but was free from any obvious overshoot of the RTC impulse, and free from any obvious dark trailing like that on the S2740L. The BenQ GW2750HM is a little different as it is based on a 1920 x 1080 resolution AMVA panel. It was not quite as fast as the S2740L overall, and also showed some dark trailing, but not quite as noticeable as on the Dell.

24" 7ms G2G LG.Display AH-IPS

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

27" 12ms G2G LG.Display H-IPS

27" 6ms G2G LG.Display H-IPS

If we then compare the S2740L with some other 27" screens featuring IPS, or the very similar PLS panels, we see the above results. These other 3 models feature 2560 x 1440 high resolution panels so are a bit different to the S2740L. The Asus PB278Q we tested recently had been impressive in these tests with very good pixel response times and only minor overshoot when the optimum overdrive ("trace free") option was selected from the OSD menu. The HP ZR2740w was free of any overshoot as well, but showed higher levels of blurring in practice. You will see that the older Dell U2711 also suffered from these dark overshoot problems, and it seems to have been an issue affecting many Dell screens in recent years.
 

24" 7ms G2G LG.Display AH-IPS

24" 2ms G2G AU Optronics TN Film + 120Hz (AMA = On)

27" 1ms G2G Chi Mei Innolux TN Film + 120Hz (Over Drive = 0)

22" 3ms G2G Samsung TN Film + 120Hz

We've also included a comparison above against three very fast 120Hz compatible screens we have tested. In all cases these other screens are using TN Film panels and are aimed primarily at gamers. Firstly there is a comparison against the BenQ XL2420T. This showed very low levels of motion blur, but some dark overshoot was introduced as a side-effect. The Iiyama G2773HS was very responsive and even has a quoted 1ms G2G response time. This showed very low levels of blur and had minimal issue with overshoot. The Samsung SM2233RZ performed very well in these tests and showed very low levels of motion blur also. When 120Hz mode was enabled the overdrive artefacts evident in 60Hz mode were almost completely eliminated, which is something we have seen with the BenQ XL2420T as well.

While these pixel response tests show the S2740L to have pretty fast transitions and low levels of motion blur (albeit with some overshoot), there is something else going on as well here which can't be picked out by the camera. All of these other TN Film models are running at 120Hz refresh rates, which allows for improved 120fps frame rates and 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. From a pixel response point of view the S2740L performed well, but there are some other areas you still need to think about when it comes to high end gaming. It couldn't keep up with the very fast TN Film models with 120Hz support.
 

The responsiveness of the S2740L was pretty good overall. The blurring was at a low level but unfortunately Dell's overdrive controlled seemed to be a little variable. A dark overshoot artefact was fairly pronounced, a little more than the recent U2412M and U2312HM in fact which had suffered in the same way. It was quite similar to what we'd seen from the 24" S2440L as well, and Dell could do with sorting this out a bit on future monitors. Overall it should still be fine for most normal users in practice. Being a 1920 x 1080 resolution screen this is also less demanding on graphics cards than trying to contend with the ultra high resolution 2560 x 1440 models. Some users may prefer this native 1080 support for their games, without the need for the screen to scale and interpolate the image from a lower input resolution. Although this 1080 resolution is also featured on smaller screens in sizes from 21.5" - 24", the extra screen size here provides increased immersion in games and is also more suited when viewing from a greater distance.

Additional Gaming Features

Aspect Ratio Control - The screen offers three options within the OSD menu for hardware level aspect ratio control. There are options to maintain the aspect ratio at 16:9, 4:3 or 5:4 ratios which should be adequate for most users and for the connection of most external devices. It would have perhaps been useful to see an "auto" mode, capable of detecting and maintaining the source aspect ratio automatically, and perhaps a 1:1 pixel mapping mode for those who didn't want the source image stretched at all. Each of the modes provided would stretch the source image to fill as much of the screen as possible, but will maintain the selected aspect ratio. In addition even if the input source is not one of the specific aspects listed, it will be forced to that aspect if you select it. For instance if you input the native 1920 x 1080 resolution, but select 4:3 aspect, it will squash the screen sideways to meet a 4:3 aspect, but the image will just be squashed accordingly. It can be a little annoying having to manually change the aspect ratio each time if you input different aspect sources.

Preset Modes - There is a 'game' preset mode available from within the preset mode menu. This seems to have a bit of a green tint to it, compared with the standard preset mode. We've already established that the DCR doesn't offer anything in real use sadly. The game preset mode also seems to accentuate the sharpness setting. This mode might be useful if you want to set up a specific mode to be different to your day to day normal use profile as well.

Input Lag

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. We have only included screens which were tested using this new method to allow for a fair and realistic comparison, and have removed any models tested using the old method.

The Dell S2740L shows a very low level of input lag. This was measured at 3.2ms average. Note that this is the overall display lag, and so accounts for the signal processing time + an element of the pixel response time. The lag of this screen has been categorised as CLASS 1 as detailed above. It should be perfectly fine for gaming as a result, even for fast paced FPS. We had seen a similar very low lag from the 24" S2440L as well (5ms average). The actual signal processing lag should be about the same, but the slight difference is probably down to slight pixel response time differences between the IPS and AMVA panels.

Movies and Video

 The following summarises the screens performance in video applications:

• 27" screen size makes it a reasonable option  for an all-in-one multimedia screen, but being quite a bit smaller than modern LCD TV's of course. As far as desktop monitors go it is at the large end.

• 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.

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

• The native screen resolution of 1920 x 1080 is perhaps more suited to movies and external DVD/ Blu-ray players which operate at 1080 HD resolutions commonly. There is no need for the screen to scale the image as it would if you were using a higher resolution model, such as a 2560 x 1440 res 27" display.

• Digital DVI and HDMI interfaces supports HDCP for any encrypted and protected content

• Good to see that both DVI and HDMI are provided on this model, allowing you to connect your PC over DVI, and leave the HDMI free for an external device potentially. It might have been nice to see DisplayPort included as that is becoming increasingly popular, but has been understandably left off to help keep production costs low.

• Only a VGA cable was supplied in the box, so you would need to purchase an HDMI or DVI cable separately if you want to make use of the digital interfaces.

• Glossy AG coating and glass front may cause issues with reflections depending on ambient lighting conditions. This could prove annoying in darkened rooms depending on the position of your light sources.

• Wide brightness range adjustment possible from the display, including reasonable maximum luminance of ~231 cd/m² and a good minimum luminance of ~40 cd/m² (default standard preset mode). This should afford you very good control for different lighting conditions.

• Black depth and contrast ratio are reasonable for an IPS panel at 691:1 after calibration. Perhaps not quite as good as we had hoped from a modern panel to be honest. Shadow detail in darker scenes should not be lost though as it's adequate.

• Dynamic contrast ratio doesn't really work at all on this model, in case there's those who like the feature.

• 'Movie' preset mode available which exaggerates the sharpness and colours, making them look more vivid. Might be preferable to some users compared with a normal PC setup mode.

• Good pixel responsiveness which should be able to handle fast moving scenes in movies without issue. Perhaps some issues apparent with overshoot in certain transitions.

• Good hardware level aspect ratio control options which may be useful for connection of external devices, DVD players etc. Options for 16:9, 4:3 and 5:4 should satisfy most uses. A 1:1 pixel mapping mode or an "auto" aspect ratio retention might have been useful.

• Wide viewing angles thanks to IPS panel technology meaning several people could view the screen at once comfortable and from a whole host of different angles. On darker content the IPS white glow may present a bit of a problem if viewed from wider angles

• Limited range of ergonomic adjustments available from the stand with only tilt available. Might be difficult to obtain a comfortable position for multiple users or if you want to sit further away from the screen for movie viewing.

• No significantly noticeable backlight leakage, and none from the edges which is good. This type of leakage may prove an issue when watching movies where black borders are present but it is not a problem here.

• No integrated stereo speakers on this model but an audio output is provided to take sound from the HDMI if it's being used.

• Make sure you adjust your graphics card settings if using HDMI from an NVIDIA card to get the full range and proper contrast ratio.

• Picture in picture (PiP) or Picture By Picture (PbP) is not available on this model.

• For PAL sources, we have tested the screen and confirmed it will support the full native resolution of 1920 x 1080 at 50Hz refresh rate.

Conclusion

If we look at the performance of the Dell S2740L first of all we were left mostly with pretty positive feelings. The default setup was pretty good overall, especially when you consider the low cost of his model. It was also nice to see an accurate coverage of the sRGB colour space from the backlight without any oversaturation problems. Black depth and contrast ratio were reasonable but we were a little disappointed that CR didn't reach a bit higher really. It was pleasing to see that PWM was not being used for backlight dimming, and the brightness control afforded you a very good range of adjustments. Pixel responsiveness was good, although some dark overshoot may present a problem to some users and was a shame to see. The input lag was very low though which was great. In other areas the screen offered some of the very good all-round performance you would expect from a modern IPS panel, with wide viewing angles and a stable image quality. Even the luminance uniformity was good here which was pleasing given the low cost.

We were pleased to find that the S2740L was not as "trimmed down" as the 24" S2440L as well. It offered a couple of USB ports, an added DVI input and VESA mounting support which was great to see. The glossy screen coating is very reflective as we'd seen on the 24" model, but that is down to personal taste really and does change the feel of the screen in practice which some people prefer. The large screen size and 1920 x 1080 resolution make this a decent option for gaming and multimedia uses as well, without the pressure on a graphics card to reach ultra-high resolutions or the need for the screen to scale the resolution for you. The added size certainly make it an attractive option for these kind of uses compared with a smaller screen, even though the resolution remains the same.

The Dell S2740L retails for ~£294 GBP (inc VAT) which make it a very affordable 27" offering. This is of course a lot less than the high res models like the Dell U2713HM (£522) and U2711 (£510 for example). It is a little more expensive than some other similar IPS models like the AOC i2757Fm (~£230) and also some  AMVA offerings of a similar feature-set, such as the BenQ GW2750HM (~£210). However, given the Dell brand, reputation, support and warranty we are sure this will attract plenty of attention. If you want a large glossy screen with a pretty decent set of features and some nice overall performance then this is a good option.