Introduction

The normal high amount of interest and excitement has surrounded the release of Dell's new 2013 line-up of UltraSharp screens, with the announcement late in 2012 that we would see a new 24" U2413 and a new 27" U2713H model released. These new displays are designed to replace some of their older models and we thought it would be useful to go into a little bit of detail about the evolution of the Dell UltraSharp range at this time. We covered this in our recent U2713H review as well, so if you've read that, you may want to skip some of this introduction. We will include it here again as it's a useful intro to the new screens. We now have the new 24" UltraSharp U2413 model with us for review.

Dell's UltraSharp naming scheme can be a little confusing to new users and there's now a few models with quite similar names, but with very different specs and features.

24" UltraSharp - The U2410 was released in 2009 and was the first of the 24" range to use the new "U" prefix and a move to the popular IPS panel technology. The screen was aimed primarily at higher end users and offered a range of features and specs which separated it from more mainstream models. It featured a wide colour gamut thanks to its WCG-CCFL backlight unit, 10-bit colour depth (8-bit + FRC producing 1.07 billion colours), factory calibration, a 12-bit LUT (not programmable unfortunately), touch-sensitive buttons, and a large range of connections, adjustments and extras. In 2011 Dell released the U2412M, with the M reportedly representing the use of a more standard colour depth (16.7m colours). In the case of the U2412M this was a 6-bit + FRC panel. It was aimed more at mainstream users with a lower retail cost and a more "friendly" standard gamut which is more suitable for the more casual user. It represented the move to the popular W-LED backlighting technology as well, bring about energy and environmental benefits. This U2412M was released to run along side the U2410, giving users the option to choose which was more suited to their requirements and budget. Now at the beginning of 2013 we are about to see the arrival of the U2413. Note the absence of the "M" at the end, as this is again a return to the higher end specs of the U2410 (8-bit + FRC panel = 1.07b colours). In fact the U2413 is designed to replace the U2410 and many of the specs and features are similar to that older screen. It too has a wide gamut, now thanks to the new generation of GB-LED backlighting instead of older CCFL units. It again features a 14-bit LUT, this time programmable by the user with the right hardware. Factory calibration has returned, as has the card reader and touch-sensitive buttons. A few other high end features have also been included this time including a uniformity compensation technology, USB 3.0 and a wider range of options for things like aspect ratio control. The U2413 represents a replacement for the U2410 with some fancy new upgrades, but Dell will continue to sell this new model alongside the existing U2412M which may still be more suitable (and accessible) for many mainstream users.

27" UltraSharp - in 2010 Dell also released their first U prefix UltraSharp screen, the U2711. The pattern is very similar to the 24" models. This original U2711 offered the high end specs and features for the more demanding professional users, including 10-bit colour support (8-bit + FRC = 1.07b colours), factory calibration, wide gamut CCFL backlighting etc. Later on in 2012 Dell released the U2713HM to run along side the existing U2711. Like with the 24" models, this represented a move to W-LED backlighting, a standard colour gamut and 8-bit colour depth (note the "M" again at the end signifying a normal 16.7m colour depth). Dell also dropped a few of the extras like the card reader, touch-sensitive buttons and extended internal LUT. You may also note the addition of an "H" at the end of the model number here, which is now used by Dell to signify 16:9 aspect ratio screens. Of course the U2711 was also 16:9 aspect ratio (both are 2560 x 1440 resolution) but at the time they did not use this H in their naming scheme. Now, right at the end of 2012, Dell have released a new model, the U2713H. This retains the H to signify the 16:9 aspect ratio again but there is no "M" this time, as Dell have moved back to the higher end specs of the original U2711. Like with the U2413 and U2410, this new model will replace the U2711. It features a 1.07b colour depth, wide gamut (GB-LED backlighting), 14-bit programmable LUT and a range of other new features to match those we've discussed with the U2413 above.

So to summarise, soon Dell will be stopping production of the U2410 and U2711 as they will now be replaced by the U2413 and U2713H respectively. These will be available along side the other recent models, the U2412M and U2713HM with the distinction being made based on specs and features. The U2413 / U2713H will be aimed more at professional users and more demanding requirements, while the U2412M and U2713HM will be more mainstream and probably more suited for an average user in most cases.

Specifications and Features

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

Manufacturers website link: Dell

The U2413 basically offers the exact same feature set as the larger U2713H model. It has a very good range of video connections which is great to see and something which Dell have always done a good job with on their UltraSharp models. There are HDMI, Dual-link DVI-D, DisplayPort and now Mini DisplayPort provided for video interfaces. The D-sub connection which was available on older screens including the U2412M has now been left off, presumably because it's less commonly used nowadays. It's nice to see HDMI provided for users who want to connect other devices, particularly external Blu-ray and DVD players. The digital interfaces are HDCP certified for encrypted content as well. There is also an audio out connection for connecting headphones / external speakers if you wish to take the sound from the HDMI or DisplayPort inputs. There are no integrated stereo speakers on this model although the screen is compatible with Dell's SoundBar if you wish.

The screen comes packaged with a dual-link DVI and DisplayPort >  Mini DisplayPort cables which is useful although there is no normal DisplayPort or HDMI cable provided with the screen unfortunately, presumably due to cost saving measures. The screen has an internal power supply and so you only need a standard kettle lead (provided) to power the screen. There is a 4-port USB 3.0 hub provided as well, with 2 ports on the back and 2 ports on the left hand side of the screen. The USB cable to connect back to your PC to power these ports is provided in the box. Like the older U2410 model there is a card reader on this model (9-in-1) which was something left off the U2412M but which personally I find useful. A nice extra. Again, the same pattern as we saw with the U2711 > U2713HM > U2713H.

As we've already discussed in the introduction the screen features a programmable 14-bit LUT to allow for hardware level calibration via the appropriate software/hardware (see hardware calibration section later on for details). The screen also has a uniformity correction technology which we will test later on as well.

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

The U2413 looks pretty much identical to the U2713H, but obviously in a smaller size. It's not that different from the design of the U2412M either. It comes in an all-black coloured design with matte plastics used for the bezel and stand. The bezel is a thin and attractive at ~17.5mm wide along all sides. It is a slightly different finish to the U2412M and looks almost like a brushed black aluminium in style, but is still plastic. The lower bezel features a shiny silver coloured Dell logo in the centre as you can see from the above images. There is no other writing on the bezel at all. The edges of the screen are a little rounded, more so than the rather straight lined U2410 in fact. I personally like the design and it looks very nice on the desk.

OSD Menu

Above: views of OSD operational buttons

Power Consumption

In terms of power consumption the manufacturers spec states typical usage of 60W and 130W maximum (with luminance max, USB connected and SoundBar connected). In standby the screen apparently uses <0.5W.

We tested this ourselves and found that out of the box the screen used 44.6W of power while at its default brightness setting. At the maximum brightness level the screen used 53.9W of power, and at the lowest setting this was measured at 21.0W. Once calibrated we had reached a power consumption of 30.6W which had been once the screen had been set to achieve a luminance of 120 cd/m² (custom color mode). You may note that this is higher power consumption than the U2412M (W-LED based, calibrated to the same luminance), and it seems the GB-LED backlights do have a higher demand during use. This is also reflected in the measurements of the U2713H (GB-LED) and U2713HM (W-LED). During standby the screen uses 0.5W of power. We have plotted the results of these measurements on the graph below:

Panel and Backlighting

Panel and Colour Depth

The Dell U2413 utilises an LG.Display LM240WU9-SLA1 AH-IPS panel which is capable of producing 1.07 billion colours with an 8-bit colour depth and additional Frame Rate Control (FRC) stage (8-bit + FRC). Dell refer to the panel as being "AH-IPS" (Advanced High Performance IPS) in some of their marketing material, and it is a name which is starting to become more common in today's IPS market. We have started to see other screens emerge with these so-called AH-IPS panels in their specs, and indeed LG.Display themselves made the same distinction when discussing their forthcoming panels (including this one) earlier in the year. This new Q3 panel actually does represent a new generation of IPS in so much as it features a new type of backlighting which we will discuss in a moment.

The panel is confirmed when dismantling the screen as shown below.

Above: view of the panel used from dismantled screen.
 

Like the U2410 which it is replacing, the new U2413 offers support for 10-bit content through the use of its 8-bit + FRC panel. This gives a colour depth support for 1.07 billion colours. However,  you need to take into account 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. Given the U2413's position as a professional grade, high-end screen, it's pleasing to see the support included. The U2412M for reference offered an "8-bit" colour depth through the use of a 6-bit + FRC panel (16.7m colours).
 

Panel Coating

The screen coating on the U2413 is much like that featured on other recent Dell IPS screens like the U2713H and U2713HM, all of which has been a positive change. It is a normal anti-glare (AG) offering as opposed to any kind of glossy coating. However, this is contrary to a lot of other older IPS based screens which usually feature a grainy and aggressive solution. In fact the Dell U2410 featured such a coating and was often criticized for its grainy, dirty appearance, especially on light coloured backgrounds. When Dell released the 27" U2713HM users were impressed by the new lighter AG coating which is an almost semi-glossy type coating. This has been retained on the new U2713H and U2413 as well thankfully. Dell seem to have toned down the AG coating on recent models which is great news. It retains its anti-glare properties to avoid unwanted reflections, but does not produce an overly grainy or dirty image that some AG coatings can.

As a side note, some users reported a "cross hatching" appearance on the 27" U2713HM screen, where on very close inspection you could detect a small grid like effect as part of the coating. This didn't affect everyone of course but it was something some people complained about or became sensitive to. Having seen this so-called cross hatching on the U2713HM we're pleased to report that neither the U2713H or U2413 suffer from this and do not show any sign of it, even when looking very closely for it.
 

Backlighting and Colour Gamut

Like the U2713H, the U2413 uses a new form of backlighting which we haven't seen before. The old U2410 model featured a CCFL backlight unit which supported a wide colour gamut (WCG-CCFL). When Dell released the U2412M they moved to the very popular and widely used W-LED (White-LED) backlighting which offers environmental and energy benefits along with a thinner form factor. This delivered a normal sRGB colour space only, but was more suitable for most general users. With the new U2413 Dell wanted to be able to offer the benefits of LED backlighting but deliver a wide colour gamut support for colour critical work and the professional users. With the new LG.Display LM240WU9-SLA1 panel they have moved to a new GB-LED backlight system.

Above: GB-LED backlight spectrum, courtesy of PCmonitors.info

The common White-LED backlight systems, despite their name, do not actually use White LED's, but rather they emit a blue light which passes through a yellow phosphor to give a more neutral white and provide the red and green components of the image. With the new GB-LED backlights, rather than using this blue diode + yellow phosphor, the backlights combine green and blue diodes with a red phosphor (i.e. Green-Blue LED = GB-LED). PCMonitors.info has a useful article about The Evolution of LED Backlights which is well worth a read as well. With this new type of LED backlight the screen covers 103% of the NTSC reference, 99% of the Adobe RGB reference and 100% (and beyond) of the sRGB space. The screen is of course classified as a wide gamut display and the colour space coverage is actually ever so slightly more than the old U2410 with a WCG-CCFL unit (which has 102% NTSC and 98% Adobe RGB coverage). We expect to see this type of backlight adopted more widely during 2013.
 

PWM Flicker Tests at Various Backlight Brightness Settings - Updated 30 July 13

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). Previously we have used a camera based method as described in the article to capture results at brightness settings of 100, 50 and 0. We now have a more advanced photosensor +  oscilloscope system which will allow us to measure backlight cycling with more accuracy and ultimately more ease. These tests allow us to establish 1) whether PWM is being used to control the backlight, 2) the frequency at which this operates if used, and 3) whether a flicker may be introduced or potentially noticeable at certain settings. 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.

100%                                                                                 50%

20%

Above scale = 1 horizontal grid = 250 µs (250 microseconds, i.e 1/4 of 1ms)

The PWM tests with the oscilloscope revealed some interesting results. At a setting of 100, 50 and 20% brightness there was a steady voltage applied to the backlight and there was no PWM used. The brightness is continuous between 100 and 20% settings. The scale of the above images is very small with each horizontal grid line representing a quarter of a millisecond (250 µs / 250 microseconds).

  19%                                                                                     0%

Above scale = 1 horizontal grid = 250 µs (250 microseconds, i.e. 1/4 of 1ms)

At a setting of 19% however we started to see the oscillogram spike as you can see in the above image, suggesting there was some cycling of the backlight, although not like "normal" PWM we have seen. This oscillation appeared to be introduced at brightness settings of 19% and below. By altering the vertical scale on the oscilloscope software (on 0% image) we could see those peaks and troughs more clearly defined. From there it was possible to work out the frequency of this oscillation which was an incredibly high 8750 Hz. This is likely to be easily high enough that it should cause few issues with flicker visibly and the amplitude is also very small. If users are very worried about flicker or particularly susceptible to it, then you need to be aware of the use of some form of PWM for settings of 19% and below. Out of the box the screen gives a luminance of ~114 cd/m² at the 20% brightness setting (See our brightness and contrast stability tests) which should prove adequate as a lower level of adjustment for those who still want to avoid the use of PWM for lower brightness levels anyway.

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

Default settings of the screen were as follows:

Dell U2413 - Default Factory Settings, Standard Mode

 

The screen comes out of the box in the 'standard' preset mode, although there are additional preset modes which carry a factory calibration which we will test shortly. Default setup of the screen felt too bright which is pretty standard for modern screens but can be easily controlled of course via the brightness control. You could immediately spot the use of the wide gamut GB-LED backlight as well, with colours looking more saturated and vivid than a normal standard gamut screen. Reds and greens in particular looked more vivid and more exaggerated. This is common for wide gamut screens of course. Some people actually prefer the more saturated colours for things like gaming and movies, even if it's at the cost of accuracy. We will look at the sRGB emulation mode in a moment which is also provided to avoid complications outside of colour managed applications for those wanting to work specifically in the sRGB colour space and on a standard gamut screen.

Out of the box the performance of the screen was pretty reasonable in this standard mode, and we were hopeful of even better performance from the factory calibrated modes. The CIE diagram on the left of the image confirms that the monitors colour gamut (black triangle) extends considerably beyond the sRGB colour space (orange triangle), especially in green shades. This is representative of the screens wide gamut and 103% NTSC colour space coverage.

We have also provided a comparison of the screen against the wider Adobe RGB reference in this standard preset mode, where the full native gamut of the backlight is used. You can see that it extends beyond the Adobe RGB reference as well in some shades, particularly reds, but does fall slightly short in the green spectrum, giving rise to the quoted 99% Adobe RGB coverage. We will test if the Adobe RGB space can be more closely matched using the defined Adobe RGB mode in a moment as well.

Default gamma was recorded at 2.3 average, leaving it a little out with a 5% deviance from the target of 2.2 which wasn't too bad. In darker grey shades the gamma was closer to 2.2, but it deviated a little higher up to 2.31 in lighter grey shades. White point was quite close to the target which was good, being slightly too warm and recorded at 6392k (2% out). Note that we are using a spectrophotometer to make these measurements which is not sensitive to the LED backlight as some colorimeter devices can be. When using a standard gamut colorimeter not designed to work with modern backlighting units like W-LED, WCG-CCFL and GB-LED there can be a typical deviance of 300 - 600k in the white point measurement which is why some sources may refer to a different white point in this test incorrectly. We had seen a slightly better default set up here than we had with the U2713H which had a larger gamma deviance (2.5 average, 15% out) and a larger white point deviance (6091k, 6% out).

Luminance was recorded at a bright 266 cd/m² which is too high for prolonged general use. The screen was set at a default 50% brightness in the OSD menu but that is easy to change of course to reach a more comfortable setting. The black depth was a good 0.32 cd/m², giving us a decent static contrast ratio of 839:1. This was pretty much the same as we'd seen from the 27" U2713H (845:1) as well. This was good for an IPS panel really. Colour accuracy was poor in this measurement but this is a result of the monitors native gamut, being much wider than the reference sRGB. DeltaE was recorded at 3.7 average, with maximum of 8.8. Testing the screen with various gradients showed smooth transitions with no sign of any banding thankfully. The usual slight gradation was evident in darker tones as you will see from most monitors.

Dell U2413 - Default Settings, Custom Color Mode

   

We also tested the default performance in the 'custom color' preset. This mode allows you access to the individual RGB channels which will give you more control over the hardware when it comes to calibration. The performance in this mode was similar overall to the 'standard' preset. As you switched to this mode you did see a step up in the luminance of the display which was confirmed with a measurement of 287 cd/m² brightness. The contrast ratio was a little higher in this mode at 901:1 since the RGB channels were now all at 100% by default (in standard mode these are preset at defined, fixed lower levels to reach the white point of that mode).

The gamma remained at a similar 6% deviance with 2.3 average, but white point was now even closer to our target than before being 0% out and measured at 6471k which was great. This mode seemed slightly better in terms of white point than the standard mode, and would allow the user to tweak things themselves to help correct things during a calibration process. Colour accuracy remained poor because of the comparison of the monitors native gamut with the sRGB reference. DeltaE was 2.9 average / 7.3 dE maximum.

Factory Calibration

Like its predecessor (U2410), the Dell U2413 comes factory calibrated to some extent, and the box even includes a calibration report from Dell specific to the unit you have. It states that every unit is shipped incorporating pre-tuned sRGB and Adobe RGB modes which offers an average DeltaE of <2. This is better than on the old U2410 in fact which only featured a factory calibrated with dE < 5. In addition to this, they have tweaked gamma and grey-scale to help to ensure smooth gradients and an accurate initial setup. Looking at the factory report it seems that Dell have opted to set the screen up with a 6500k white point which is good news (as far as our test targets go). This is contrary to the U2713H though which had been set up to a target in the factory of 6000k for some reason.

As a new extra they have also apparently adjusted luminance and colour uniformity across the screen which is available from within the OSD as the uniformity compensation option which we will test later on. I've included a copy of the calibration report from the Dell factory below for you to review. Note that this report is only relevant to our specific test unit and they do state that results may vary with each setup and different test equipment.

I was interested to see if this factory calibration helped at all with default settings. Note that this is only relevant for the sRGB and Adobe RGB preset modes available through the OSD menu. You will need to change from the default 'Standard' profile to benefit from these factory calibrated settings.
 

Dell U2413 - Default Factory Calibration, Adobe RGB mode

   

The factory calibration of the Adobe RGB preset mode was pleasing. This mode actually offered a reliable emulation of the Adobe RGB colour space as well, helping to cut back the slight oversaturation of the screens native colour space and now closely matching the Adobe RGB reference. If you prefer this to the full native gamut of the screen it might be useful for colour critical work in this colour space.

Comparison of Adobe RGB colour space coverage in Standard preset mode (native gamut - left) and in Adobe RGB emulation mode (right)
 

The average gamma was similar overall to the default standard mode as it remained 4% out from the target at 2.3 average. White point was also now slightly closer to the 6500k target, and was measured at 6454k (1% out). Luminance was still too high and this was perhaps the main area which deviated from our target. A simple OSD brightness change can of course overcome this though so this is no big issue. Contrast ratio remained similar to the standard preset mode at 802:1, being just a little lower (839:1 in standard mode). Colour accuracy (as compared with sRGB) was still off in this measurement due to the wide gamut of the screen, with a dE average of 4.4 and maximum of 9.4. This mode did offer a good factory calibration in terms of white point and gamma and a reliable emulation of the Adobe RGB colour space as well. A good result from the Dell factory setup.

Dell U2413 - Default Factory Calibration, sRGB mode

   

The factory calibration of the sRGB preset mode was also pleasing. This mode offered a reliable emulation of the sRGB colour space, helping to cut back the large oversaturation of the screens native colour space and now very closely matching the sRGB reference. This might be useful for colour critical work in the sRGB colour space and also for those who want to avoid complications with wide gamut and colour management, not to mention with movies and games.

The gamma was still a little out from the target of 2.2, being measured at 2.3 average (4% deviance). The white point was again slightly better than the default mode, now being measured at 6485k and being pretty much spot on. Luminance was still too high, but easy enough to adjust through the OSD menu. The contrast ratio was very similar to before, but slightly lower at 786:1. Since we are now working with an sRGB colour space the colour accuracy tests are more useful since they are based on an sRGB reference. The dE average was 1.1 and maximum was only 2.5. This represented a very good accuracy from the factory calibration. We would have liked a slightly more accurate gamma setup in this mode, but the emulation of the smaller colour space and the accuracy of the colours was very pleasing.

Testing Colour Temperatures

The U2413 features a range of colour temperature presets within the OSD 'color settings' menu as shown above. You have to choose the specific 'color temp' preset mode first but you are then asked to define your target colour temp from the 6 presets available. We measured the screen with the X-rite i1 Pro spectrophotometer in each of the preset modes to establish their colour temperature / white point. All other settings were left at factory defaults and no ICC profile was active. The results are recorded below:

The colour temperature modes offered reasonable levels of accuracy overall with a maximum deviance from the target of only 7.3%. Each mode was a little too warm compared with its desired white point, but only by a small amount. The 6500k mode was actually the closest to the target, being measured with a 1.6% deviance at 6396k which was pleasing. Overall the preset colour temp modes were reasonable really although not as accurate as you might see on some other high end pro grade screens from the likes of Samsung, NEC and Eizo.

Software Calibration Results

The U2413 may well have a decent factory setup in some modes but given the market for this screen I expect many users will want to calibrate the screen personally to obtain even higher levels of accuracy and allow profiling and matching between different devices.  Remember, you need to ensure you have a device capable of measuring and reading the spectra from the GB-LED backlight unit properly. Many older colorimeter devices are designed to work with standard gamut CCFL units only and so they can often have difficulty reading LED (and wide gamut CCFL) units properly. A spectrophotometer does not have this problem and there are also some decent modern colorimeters like the X-rite i1 Display Pro which should be able to read LED without issue. While you can use other devices and various software packages to complete software profiling of the screen, you may come across issues if the device is not designed to work with an LED backlight unit.

The U2413 also offers hardware calibration which can give you very high levels of accuracy and control over the monitors 14-bit LUT itself. We will look at that in a moment, but we also wanted to carry out the usual software level "calibrations" (profiling) at a graphics card level. We 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.

Dell U2413 - Calibrated Settings, Custom Color Mode

   

I first of all reverted to the 'custom color' mode in the preset section of the OSD menu. This retains the monitors full native gamut and would allow me access to the individual RGB channels. There is actually a very wide range of controls here if you need them for gain, offset, hue and saturation, allowing the user to make finite adjustments where necessary. Adjustments were 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.

Average gamma had been corrected to 2.2 according to the initial test ,correcting the default 6% deviance we'd found in this preset. The white point remained pretty much spot on at 6474k which had been pretty accurate out of the box anyway (6471k, 0% deviance). Luminance had also been corrected thanks to the adjustment to the brightness control, now being measured at 120 cd/m². This also gave us a calibrated black depth of 0.17 cd/m², and a static contrast ratio of 692:1 which was moderate for an IPS panel. 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.

Testing the screen with various colour gradients showed mostly very smooth transitions. There was some slight gradation in darker tones and some very slight banding introduced due to the adjustments to the graphics card LUT from the profilation of the screen. Nothing major at all though. It's worth also commenting on the screen coating in this section of the review. Unlike many other IPS panels, this screen does not feature the usual heavy and aggressive Anti-glare (AG) coating which can sometimes lead to grainy and dirty looking images. Instead it uses a light AG screen coating and as a result the colours look more clean and crisp, the image quality is sharp and whites in particular look more pure than they do on heavy AG coated screens. It isn't a full glossy solution which adds another level of clarity and changes the overall feel of the screen, but it is an improvement over the heavy AG coating of some other IPS screens, including the previous Dell U2410. A positive change and hopefully something we will start to see more of with future IPS screens.

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.

I also carried out the calibration in the monitors 'sRGB' emulation mode. Here you do not have access to the RGB channels at all, and so the only hardware changes being made are to the brightness control. The other corrections would be carried out at a graphics card LUT level through the profiling process. However this would of course allow you to work with the smaller sRGB colour space which we'd already established was being well emulated in this preset.

The results were again very pleasing. The target for gamma had all been met pretty nicely, correcting most of the 4% deviance we'd seen out of the box. The white point had been accurate before so did not need addressing here. The luminance had been corrected to the desired level with the change in the brightness control, and the static contrast ratio was a moderate 723:1 after calibration. Colour accuracy had been corrected from the already very good dE 1.1 average we had seen out of the box thanks to the factory calibration, now down to 0.4 dE average. Testing the screen with various colour gradients showed smooth transitions on the whole, with some slight gradation and some very slight banding in some darker shades due to the graphics card corrections made. You can use our settings and try our calibrated ICC profile if you wish, which are available in our ICC profile database.

I also carried out the same process in the Adobe RGB preset mode. This too was factory calibrated out of the box and had offered a pretty reliable setup, along with an accurate emulation of the slightly smaller (compared with the backlights native gamut) Adobe RGB colour space. The calibration helped correct most of the 4% deviance we'd seen by default in the gamma. We also corrected the small 1% white point deviance from the factory setting. Contrast ratio was now being measured at 711:1 after profiling which was moderate for an IPS panel. Colour accuracy had been corrected, now with a 0.4 dE average and maximum 1.4 measured when validating the produced profile. Testing the screen with various colour gradients showed smooth transitions on the whole, with some slight gradation and some slight banding in some darker shades due to the graphics card corrections made. This banding was a little more apparent than in the calibrated sRGB mode. You can use our settings and try our calibrated ICC profile if you wish, which are available in our ICC profile database.
 

Hardware Calibration

Updated 29 October 2014

One thing which separates this screen from many mainstream monitors, including the previous Dell 24" offerings, is the support for hardware calibration. Users can program the monitors 14-bit Look Up Table (LUT) if they have the appropriate software and hardware to achieve higher levels of accuracy, something which professional users require and one of the reasons why pro-grade screens from NEC and Eizo have always been popular in such markets. The software part of is easy, Dell provide their own free "Color Calibration Solution" software which is available to download from Dell.com. This is a piece of software made for Dell by X-rite and allows the user to access the hardware LUT to calibrate the screen in two available modes. Currently the latest version is v 1.5.3 for Windows operating systems (Win 7, 8, 8.1). There is also now a Mac OS version available here. These versions should work with all the hardware calibration supporting UltraSharp models, despite the download page only listing the UP2414Q and UP3214Q.

Important: The second part is not so easy however as you require a compatible calibration tool to work with this software and allow hardware calibration. Dell, or rather the software provider X-rite, have locked this so that you can ONLY use the X-rite i1 Display Pro colorimeter, or i1 Pro / i1 Pro 2 spectrophotometers. Other devices are NOT compatible at all, including the i1 Display 2, ColorMunki, Spyder series or any other colorimeter. The software was co-designed between Dell and X-rite and X-rite have recommended the use of the i1 Display Pro or i1 Pro devices with the wide gamut backlighting.

Users who already have another type of colorimeter will be disappointed as although they will be able to software calibrate their screen (profiling) as we have done in the previous sections as normal, they will not be able to use it for the all-important hardware calibration. I'm sure consumers will argue they should not need to buy a new colorimeter to use with this screen and that other devices should be compatible. We would be inclined to agree, but unfortunately the reality is that you can only take advantage of the hardware calibration of the U2413 (or 27" U2713H / 30" U3014) if you have a compatible X-rite device. If you don't own any device yet, these are obviously the ones to get for these displays.

We have already looked at the Color Calibration software in some detail in our Dell U2713H review (v1.0.0.0 at time of writing that review), so please see the relevant section there if you want more information and screen shots.

When calibrating at the hardware level you can choose whether you are going to calibrate either CAL1 or CAL2 modes, and once you've done so you can quickly and easily switch between them from within the monitors OSD in the preset section. This allows you to set up a couple of custom modes, perhaps working with different colour spaces (sRGB vs. Adobe RGB for instance) or with different target white points, gamma curves or luminance levels. The options to select these pre-defined colour spaces are shown above, and you can also specify your target luminance. The whole process from there is automated and completely controls the screen for you without the need for you to manually change anything. The Dell software itself lacks any kind of reporting or validation stage and so it can be tricky to verify what you have ended up with. You would need a third party piece of software in order to carry out further validation tests, and something like BasICColor Display (with a free 14-day trial) would be a good option.

Update 14/1/14 - As we have learnt from our more recent review of the Dell UP3214Q, Dell and X-rite have now updated their calibration software package to include some validation and reporting elements which brings the software more in line with their i1 Profiler package. See our UP3214Q review for more information.

First of all we hardware calibrated the screen using the X-rite i1 Display Pro and selecting the 'native' colour space mode, and a target luminance of 120 cd/m². Once calibrated we tested the screen again using the test and report functionality from within LaCie's Blue Eye Pro software and used our i1 Pro spectrophotometer to see how well setup the hardware calibration seemed to be.

The screen has been kept at its native gamut, with the colour space stretching beyond the Adobe RGB space and not being cut back at all to any smaller emulated space. We can see that the gamma curve has been corrected to some extent now, helping to address the 5% deviance we'd seen in the monitors 'standard' preset mode (which is based on the full native gamut of the backlight). This was now 2.2 on average with a small 2% deviance. The white point was measured at 6355k and so was close to our target of 6500k with a 2% deviance. We know from the factory calibration report that the target white point there seemed to be 6500k, but it's a little unclear what the Dell software sees as its target.

The luminance had been corrected pretty nicely here which was good, and the resulting contrast ratio of 783:1 was moderate still for an IPS panel, but better than we'd achieved in the software calibration tests using the monitors native gamut (692:1 when calibrating in the 'custom color' mode). Colour accuracy was also very good with dE average of 0.6. The hardware calibration was a success and had worked very well. Colour gradients showed smooth transitions with no visible banding. Unlike a software calibration where some tonal values are lost and some slight banding is introduced, this hardware adjustment to the monitors LUT can help produce very smooth gradients thankfully.

We performed the same process again, but this time choosing the 'Adobe RGB' setting within the software. This is designed to emulate the slightly smaller Adobe RGB space, much like the specific Adobe RGB preset mode in the OSD menu. We had already tested the OSD preset mode based on its factory calibration and determined it had emulated that colour space well, been very close to our target white point (6454k, 1% out) but left us with some gamma discrepancies (2.3 average, 4% out).

Through the hardware calibration in this mode we can see that the monitors native colour space has been reduced a little, and actually now more closely matches the Adobe RGB reference than the factory calibrated Adobe RGB preset it seemed. Presumably the colour coordinates defined in the software are even closer to the Adobe RGB space than those used for the factory OSD preset. Gamma had been improved again to 2.2 average was a small 1% deviance. White point was now 6143k so actually a bit further from our target (5%) now. Perhaps this preset mode is aiming for a 6000k white point? Or perhaps there are some discrepancies with the measurement of the white point when using the i1 Display Pro with a GB-LED backlight system? Luminance had again been corrected pretty nicely, with the small deviance likely down to the differences between the calibration tools. Contrast ratio was 692:1 which is pretty much what we'd seen from our software calibration as well. Again there was no visible banding from gradients thanks to the finite adjustments to the hardware LUT.

Lastly we used the sRGB option to calibrate to this smaller colour space. This was emulated well but was actually slightly different to that seen in the OSD sRGB mode. There was a slightly improved coverage now in green shades, but a little over-coverage in blues and reds. Gamma was not improved sadly and still remained with a 6% deviance at 2.3 average. The white point was 6168k so again a little out from the target (5%) and moving us further away from the factory calibrated 6485k. Contrast ratio was 682:1 and only a little lower than we'd achieved through our software calibration. Again there was no visible banding from gradients thanks to the finite adjustments to the hardware LUT.

Overall the process was pretty simple to use although it did take a while for each calibration. The software is lacking any kind of reporting feature which is a shame so you just have to trust that the targets have been achieved, or find some other software which will allow you to validate the results. The native and Adobe RGB modes in the software produced the required colour spaces very well, in fact even making an improvement over the defined Adobe RGB OSD preset mode and more closely matching the reference space once hardware calibrated. The sRGB option produced a slightly different colour space coverage as well than the OSD sRGB mode, but was pretty close.

Gamma was corrected pretty well to ~2.2 in the native and Adobe RGB modes which was good, but was left with a 6% deviance in the sRGB mode sadly. The white point seemed to be 200 - 300k out and actually moved the colour temperature further away from our 6500k target in the Adobe RGB and sRGB modes compared with their factory calibrated states. Perhaps this is a result of the factory calibration being targeted at 6500k (according to the calibration report sheet), and maybe the software is targeted at 6000k instead? Or it could be down to white point measurement inaccuracies when using the i1 Display Pro with a GB-LED backlight?

While the Adobe RGB and sRGB options had resulted in a contrast ratio just slightly lower than what we'd seen through software calibrations,  the 'native' mode had resulted in a slightly higher contrast ratio of 783:1 which was good, although still not particularly great for an IPS panel in the modern market. This seemed to be the optimum contrast ratio post-calibration we could achieve, through either  software or hardware methods.

As a side note, the uniformity compensation feature is not available when using the CAL1 and CAL2 modes. We will look at that feature later in the review but without meaning to spoil that section, it's not really practical to use in reality anyway. It is a little odd however that Dell have not made the two available together. Had the feature worked properly without its current restrictions (as it did on the Dell U2913WM we've also tested), it would have been nice to be able to combine it with the hardware calibration modes.

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 U2413 in the non-factory calibrated "standard" mode was reasonable really. There was a small 5% deviance in gamma, and a smaller 2% deviance in white point which was pleasing. This mode operated in the full native colour space of the backlight of course, but there are factory calibrated Adobe RGB and sRGB modes available too if needed, with a reliable emulation of the smaller colour spaces.

The calibrated black depth and contrast ratio of the U2413 were moderate for an IPS panel no matter how we calibrated the screen, in different preset modes and colour spaces. We achieved 783:1 through the hardware calibration at the native screen gamut which seemed to be the optimum we could achieve. When emulating smaller colour spaces like Adobe RGB and sRGB the contrast ratio was reduced somewhat (692:1 and 682:1 respectively). This 783:1 contrast ratio was also a bit higher than we'd achieved through our software calibration which at best had returned 692:1 in the 'custom color' mode. The contrast ratio offered by the U2413 should be more adequate for most users still although it was not as high as we would have liked to see from a modern IPS panel really. Those needing a higher CR may want to consider other technologies like AMVA.

Contrast Stability and Brightness

The luminance range of the screen was excellent. At the top end the panel reached a high 342.14 cd/m² which was only a little short of the specified maximum luminance of 350 cd/m², and should be more than most users would ever need as an upper limit. At the lower adjustment end it could reach down to a very low 33.15 cd/m² which was even a bit lower than the specified 50 cd/m² minimum. This meant 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 ~21% should return you a default luminance of around 120 cd/m² as well. Black point ranged from 0.41 cd/m² down to 0.04 cd/m² with the backlight adjustments.

We have plotted the luminance trend on the graph above. The screen behaves as it should, with a reduction in the backlight intensity controlled by the reduction in the OSD brightness setting. This was not a linear relationship though. As you can see from the graph the settings between 100 and 50% actually controlled a pretty small adjustment range between 342 cd/m², and 269 cd/m². The changes in the OSD to the brightness control were only bringing about a small change in the observed luminance of the display. From 50% downwards the luminance changed more dramatically as shown by the steeper line on the graph. This range from 50 to 0% allowed you to adjust the luminance from 269 all the way down to 33 cd/m², giving the user a more significant control over the actual luminance of the display. As we discussed earlier on in the review, the dimming of the backlight from a setting of 100% all the way down to 20% is achieved without the use of Pulse Width Modulation (PWM) which is positive news. From 20% downwards PWM is used but at a very high frequency which is unlikely to produce visible flicker to most users.

Average contrast ratio in the standard default preset mode was measured was 834:1 which was good for an IPS panel really. In fact this was measured in the 'standard' preset mode and you could improve on this by using the 'custom color' preset mode if needed. It was pretty stable across the adjustment range with some small deviations at the lower end of the brightness scale.

Dynamic Contrast

We tested the DCR feature in both the movie and game preset modes while at default settings (50% default brightness). On these Dell screens 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 no initial change to the energy bar and the screen seemed to remains at a luminance similar to the default 50%. 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 1 bar in the OSD menu. This change took about 1 second to complete.

Oddly in the movie preset mode the contrast ratio was pretty poor at 643:1 even with this very slight dynamic adjustment going on. We measured a static contrast ratio in this mode with DCR turned off at a very close 615:1 anyway so it seemed this mode did not offer the best contrast ratio anyway. In the game preset mode again the DCR seemed to hardly work at all in these tests with only a 1 bar adjustment in the OSD being visible. We obtained a DCR of 815:1 which was not really any better than the static contrast ratio we'd seen in the default 'standard' preset modes. When comparing a mostly white and mostly black image the DCR seemed to be doing very little at all.

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 bit more, down to energy bar level 3. When switching back to brighter content you could see the screen increasing in small steps every ~9 seconds so transitions back up the brightness scale were slow. This would in theory give you a better DCR in practice 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 U2413 it was not turning the backlight off. In normal use, the DCR is pretty much useless. This is a very similar story to what we'd seen from the U2713H sadly.

Viewing Angles

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

Viewing angles of the U2413 were very good as you would expect from an IPS based panel. Horizontally there was very little colour tone shift until wide angles past about 45°. Contrast shifts were slightly more noticeable in the vertical field but overall they were very good. The screen offered the wide viewing angles of IPS technology and was free from the very restrictive fields of view of TN Film panels, especially in the vertical plane. It was also free of the off-centre contrast shift you see from VA panels and a lot of the quite obvious gamma and colour tone shift you see from some of the modern AMVA and PVA offerings. All as expected really from a modern IPS panel.

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

On a black image there is a characteristics IPS white glow, but in normal working conditions this shouldn't present much problem. The above image was taken in a darkened room to demonstrate the white wide angle glow when viewing a black screen. There is no A-TW polarizer on this panel which is rarely used now in the market but was implemented on some older screens to improve the off centre black viewing.

If you are viewing dark content from a close position to the screen you can sometimes see this pale glow on parts of the screen towards the sides and corners because of your proximity to the screen and your line of sight. The edges of the screen are at an angle from your line of sight which means you pick up this white glow to a smaller degree. This is often referred to as "IPS glow". This disappears as you move backwards away from the screen where the line of sight does not result in a wide angle view of parts of the screen and you can see the screen largely from head on. This glow should not be mistaken for backlight bleeding which would not disappear as you changed your line of sight or angle of viewing.

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. First of all measurements of the luminance 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 the NEC customised X-rite i1 Display 2 colorimeter. Measurements for colour temperature (white point) were taken using BasICColor software and the i1 Pro spectrophotometer which can more accurately measure white points of different backlighting technologies.

The below uniformity diagram shows the difference, as a percentage, between the luminance recorded at each point on the screen, as compared with the central 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. For colour temperature uniformity we leave all settings at default in the OSD menu and ensure no ICC profile is active. Again the uniformity is expressed as a percentage deviation from the central measurement of the screen.

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. The U2413 features a uniformity compensation feature which we will test here as well, but first of all we left this setting off.

Luminance Uniformity

Uniformity of Luminance
Uniformity Compensation = Off

The luminance uniformity of the U2413 was pretty good really, with only some minor deviations towards the top right and left hand corners. Here it dropped by ~16% maximum, down to ~103 cd/m². Approximately 75% of the screen was within a 10% deviance from the target which was good. A pleasing result here from the U2413.

Uniformity Compensation Feature

Like the 27" U2713H, the U2413 features a uniformity compensation feature within the OSD menu as shown above. This isn't something Dell have made much fuss of oddly, but it's a feature again normally reserved for pro-grade screens. We've seen similar technologies used on NEC and Eizo screens in the past with some positive results. The Dell manual states: "Uniformity Compensation adjusts different areas of the screen with respect to the centre to achieve uniform brightness and colour over the entire screen. For optimal screen performance, Brightness and Contrast for some preset modes (Standard, Color Temp) will be disabled when Uniformity Compensation is turned On. When Uniformity Compensation is turned On, Energy Smart cannot be activated. NOTE: Screen Uniformity performance is optimized at default out of factory luminance setting."

There are options available for "calibrated" and "user" as well as an off setting. The calibrated option is supposed to represent a factory setup and as per the manual this is apparently optimised when in the screens default setup and at the default 50% luminance. According to the manual the user mode is "reserved for Dell approved user calibration software settings" although we have since confirmed with Dell engineers that the 'user' feature was abandoned late in development on these new UltraSharp screens and is not available, with no plans to make it available. It should be removed really from the manuals and OSD menu which Dell are looking at for future revisions.
 

We had actually seen from the U2713H testing that this uniformity compensation mode seemed to do nothing in reality to change the actual performance of the screen. When switching to the "calibrated" mode you could see a visible change in the brightness of the screen but when verifying the variations across the screen with a colorimeter, no improvements had been made. This was a disappointment certainly, especially when we then later tested the Dell U2913WM which had the same feature which seemed to work pretty well.

The uniformity correction option is only available in certain preset modes as well, those being standard, custom color and colour temperatures. It is not available in the colour space modes so you cannot even select this as an option if you want to work with the Adobe RGB or sRGB emulations, or with any hardware calibrated mode. That in itself seems a very odd choice really considering the type of screen this is.

Regardless, we tested the feature in the standard mode first of all. Unlike on either the U2713H or U2913WM screens when we turned the uniformity compensation feature to "calibrated", the brightness of the screen jumped up significantly. In fact it appeared to revert to standard settings (50% brightness). When we then tried to alter the brightness setting manually we were presented with the above warning message. On the U2413 you cannot even change the brightness setting if you want uniformity compensation turned on! If you switch to the 'custom color' mode, the brightness control can be changed in the OSD, but it makes no difference to the actual visible luminance of the display. This was another odd choice from Dell. Not only can you not enable this feature in the main factory calibrated or hardware calibrated modes, but if you do enable it in the other supporting presets, you're locked at a very high luminance without the ability to change it! Who would even want to operate the screen at such a high luminance anyway? We persevered with the tests anyway.

Uniformity of Luminance
Uniformity Compensation = Calibrated, Standard mode, locked 50% brightness

Interestingly this mode did seem to offer an improvement in the overall luminance of the screen when it was enabled. We now had smaller deviations of only 8.5% maximum in the top corners, now actually being a little brighter than the centre of the screen. 100% of the screen was now within 10% deviance of the central point. However, because the brightness was now locked and could not be changed, the screen was far too bright with an average luminance of 239.4 cd/m² across the screen. Unlike on the U2713H, this does seem to work, but is pretty much pointless given the locking of the screens brightness and the inability to use it in the main user modes (Adobe RGB, sRGB, CAL1 and CAL2).

Colour Temperature / White Point Uniformity

We also carried out our tests in this area to establish how uniform the colour was across the screen. We measured the white point (colour temperature) deviance compared with a central measurement point at default settings. First of all we carried out this test with the uniformity compensation feature turned "off".

Uniformity of White Point / Colour Temperature
Uniformity Compensation = Off

As you can see, the colour temperature was very uniform across the panel with only small deviations across the screen. There was a maximum of 2.6% deviance in the bottom right hand corner, but the rest of the screen was within 2% of the central measurement point. This was all with the uniformity compensation feature turned off, indicating that even without it, the colour temperature was stable.

Uniformity of White Point / Colour Temperature
Uniformity Compensation = Calibrated, Standard mode, locked 50% brightness

We then turned the uniformity feature back on to 'calibrated' and ran the same tests. As you can see the results are pretty similar, with maybe some minor improvements made in the left and lower portions of the screen. In the case of white point, that's probably a good thing since the default performance with the setting off was very good anyway. As we've already said, the uniformity compensation mode is pretty useless anyway because of the limitations you then have in preset mode selection and brightness control.

We fail to see the point in this feature at all on the U2413, and really hope Dell sort this feature out for future screens (maybe future revisions of the U2413?) Considering it worked well on the U2913WM, without any of these limitations about locked brightness levels we are sure it must be possible for Dell to get it working. Really you'd have hoped it would be a workable feature on the U2713H and U2413 as opposed to on the U2913WM given they are supposed to be the higher grade professional range screens. As it is, on the U2413 it isn't available at all in the main preset modes you'd probably want to use, and then when you do find a preset where it's available, you're then stuck with a locked brightness which is far too high for any prolonged use. A shame really as it does seem to work reasonably well on this screen in those pretty tight guidelines.

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 at all to the naked eye and the uniformity looked very good, even in a darkened room. The camera captured some slight clouding from the right hand corners, but this was very slight and not something which you should notice in practice. A pleasing result here.

General and Office Applications

The 1920 x 1200 resolution and 24" screen size give a nice decent area in which to work and the vertical resolution is a little more than the wide range of 16:9 aspect 24" models (1920 x 1080) out there in the market. A lot of people prefer this extra vertical area and it is useful for office applications we think. You may want to 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. Nevertheless, the 24" 1920 x 1200 resolution should be adequate for many users. The screen offered a comfortable 0.27mm pixel pitch which delivered easy to read text at a nice size, in my opinion. The resolution is certainly big enough for side by side split screen working as well in many cases.

The light AG coating is a very positive move when it comes to these kind of uses and we had been pleased when Dell made this switch before with the U2713HM. It's great to see this has carried over onto the new models as well including the U2713H, U2913WM and now the U2413. The new lighter coating ensures that white backgrounds of office documents looked good, and did not suffer from the overly grainy and dirty feel of some competing IPS panels featuring heavy, aggressive AG coating - including the old U2410 and U2412M. It also remained free from the reflections you might experience from a full glossy solution (e.g. Dell S2440L) so seems to be a good half-way between the two.

The wide viewing angles provided by the IPS panel technology on both horizontal and vertical planes, helps minimize on-screen colour shift when viewed from different angles. The default setup of the screen was pretty good even in the standard mode, and the factory calibrated Adobe RGB and sRGB modes were even better, providing a more reliable gamma and white point setup which should produce a decent image for office work. They also allowed you to choose between a wide gamut or standard gamut colour space which was very useful, and many users may prefer to use sRGB to avoid complications with colour management and oversaturation of colours. If you follow our basic OSD adjustments from our calibration process (and maybe also try our calibrated ICC profiles) you should be able to get a better setup, even without a colorimeter of your own. Of course given this is a high end screen aimed at professional users it is logical to expect many people who purchase the screen will already have a calibration tool of their own, or at least plan to buy one soon. With a calibrator you can of course obtain even more accurate setups which is great news, although you do need to be wary of the limitations of the hardware calibration feature which we talked about earlier. If you've not got a device yet and plan to buy one, make sure you buy an X-rite i1 Display Pro if you want to use the hardware calibration. That would also be a good device for use with other displays as well.

There is a specific 'paper' preset mode available within the OSD menu which makes the image darker and more yellow. This might be useful to some for certain reading conditions, but with the wide range of adjustments and modes available it should be easy enough to get an optimum setup for your uses.  Out of the box the luminance was too high and so you will want to turn this down a fair amount to obtain a setting comfortable to you in your lighting conditions. A setting of around 21% brightness should give you a luminance of around 120 cd/m² out of the box. The brightness control affords you a good range of adjustments as well, allowing you to go up to ~342 cd/m² and down as low as ~33 cd/m². Even those wanting to use the screen in low light conditions should find the adjustment range more than adequate. 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 from the brightness adjustment range of 100 to 20%. So those who suffer from eye fatigue or headaches associated with flickering backlights need not worry here. This range allows you to control the luminance down to ~114 cd/m² as well which should mean most can use the screen comfortably without PWM being introduced. At a brightness setting of 19% or below, PWM is used for backlight dimming but at a very high frequency which is unlikely to cause too many problems one would hope. The screen is also free from the so-called "cross-hatching" issue which some users noticed on the 27" U2713HM. There was no sign of the buzzing noise either that we'd heard from the U2713HM and U2713H when displaying certain images on the screen, usually with full screen text documents. Thankfully that didn't appear to be an issue with the U2413.

The screen offers a 4 port USB 3.0 hub which is useful, especially with 2 ports located on the left hand edge for easy and quick access. There is also a 9-in-1 card reader which is good news and something personally I've found useful on previous Dell models. Nice to see it returning here for the U2413. There was a good range of ergonomic adjustments available which were all easy and smooth to use. The screen offers a rotation function which is probably ok to use at this size. The VESA mounting support may also be useful to some people. There is no D-sub interface for us to check here, but the picture quality fro the digital DVI interface was very good.

 
Above: photo of text at 1920 x 1200 (top) and 1680 x 1050 (bottom)

The screen is designed to run at its native resolution of 1920 x 1200 and at a 60Hz recommended refresh rate. However, if you want you are able to run the screen outside of this resolution. We tested the screen at a lower 1680 x 1050 resolution to see how the screen handles the interpolation of the resolution, while maintaining the same aspect ratio of 16:10. At native resolution the text was very sharp as you can see from the top photograph. When you switch to a lower resolution the text is larger of course but actually still retains a lot of its sharpness. There is of course some blurring of the text but it's not too severe. A decent performance really if you did need to run outside of native resolution for whatever reason. We would recommend native resolution wherever possible for maximum picture quality and screen real-estate of course.

Responsiveness and Gaming

The U2413 is rated by Dell as having a 6ms G2G response time which implies the use of overdrive / response time compensation (RTC) technology, used to boost pixel transitions across grey to grey changes. There is no user control over the overdrive impulse within the OSD menu and so we are reliant once again on Dell's factory setup. The part being used is the LG.Display LM240WU9-SLA1 AH-IPS 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 new response time testing method. This uses an oscilloscope and photosensor to measure the pixel response times across a series of 20 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.

On the whole the pixel transitions were pretty fast. The average G2G response time was measured at 7.9ms which was just a little slower than the specified 6ms G2G from the manufacturer, but still very respectable. Some black to grey changes (0-50, 0-150) were a little slower at ~10 - 12ms. There was only minimal difference between the average G2G rise time (changes from dark to light shades) and the average G2G fall time (changes from light to dark shades). Interestingly the changes to a full white shade (255) were the fastest where it seems the overdrive impulse was being applied the most aggressively.

Unfortunately if we evaluate the Response Time Compensation (RTC) overshoot then the results are not as pleasing. There is some significant overshoot evident with transitions from dark to light shades, particularly when changing to white (255). We had already noted that the response time for these transitions was very low and it seems that the overdrive impulse is being applied very aggressively here. While it may be speeding up the pixel transitions it is causing a large degree of overshoot. For the changes to 200 and 255 the average RTC overshoot was a high 16.8% which was not very good at all. In practice this results in an obvious trailing image on certain transitions which could prove distracting.

Transition: 50 - 255 - 50

The above oscillogram is a classic example of what we saw. This is from the transition from 50 - 255 - 50. There was a fast rise time from dark to light shade (5.3ms) but an obvious overshoot was introduced (15.7%) shown by the peak exceeding the upper flat line. The fall time was a little slower (9.1ms) but there was no overshoot from that transition from light to dark. This was fairly typical of the overshoot characteristics of the U2413. Transitions from light to dark are not affected by as much overshoot but there are still some errors with the transitions which are close together (e.g. 255 - 200 and 200 - 150). In fact there was a huge error of 51.2% with the change from 255 - 200 which was very severe.

We can conclude that the response times of the U2413 are pretty good, but the RTC overshoot may prove problematic to some users. This will be particularly noticeable in transitions from dark to light shades in practice and it seems Dell have been too aggressive with their overdrive impulse in trying to cut back pixel rise times and this has resulted in some quite problematic overshoot. For reference this was a very similar picture to what we saw with the 27" U2713H which shows similar pixel response times, and high levels of overshoot in transitions from dark to light shades.

Display Comparisons

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.

24" 6ms G2G LG.Display AH-IPS

In practice the Dell U2413 showed fairly low levels of motion blur although some was detectable to the naked eye and picked up in these tests. There was nothing severe and no obvious ghosting which was good. In these tests we did not see any obvious overshoot problems which was interesting but this is likely to be down to the colour transitions being made in this program. The transitions are from light to dark shades with the movement of the car and we know from our oscilloscope tests that there was minimal overshoot in those circumstances. Thankfully our oscilloscope method allows us to measure a wider range of transitions and provide a more complete picture. Further tests with other moving images of different colours shows that the RTC overshoot is quite varied and can manifest itself more severely in the dark > light pixel changes.

24" 6ms G2G LG.Display AH-IPS

24" 8ms G2G LG.Display e-IPS

24" 6ms G2G LG.Display H-IPS

24" 6ms G2G AU Optronics AMVA

We have provided a comparison of the U2413 here against the 3 other 24" Dell screens we have tested. As you can see there is slightly less motion blur noticeable on the U2412M although it does exhibit a more obvious dark overshoot in these tests. The older U2410 was at a similar level to the U2413 in terms of responsiveness though and it looks like it performs quite similarly really. The AMVA based S2440L again showed pretty obvious dark trails behind the moving car due to an aggressive overdrive impulse.
 

24" 6ms G2G LG.Display AH-IPS

27" 6ms G2G LG.Display AH-IPS

27" 8ms G2G LG.Display AH-IPS

29" 8ms G2G LG.Display AH-IPS

We have also provided a comparison of the U2413 above against three other recent Dell screens we have tested which also use IPS panel technology. The U2413 was quite comparable in practice to the U2713H, and our accurate response time measurements with the oscilloscope system showed similar G2G response times and a similar story when it came to the RTC overshoot issues with dark to light colour changes. The U2713HM was a little faster with slightly less motion blur and freedom from any overshoot problems. We have also verified the results for the U2713HM with the oscilloscope. The 29" U2913WM had also shown some decent responsiveness and was a little faster than the U2413 and U2713H.

24" 6ms G2G LG.Display AH-IPS

24" 8ms G2G LG.Display e-IPS (Response Improve = On)

24" 8ms G2G LG.Display p-IPS (Response Improve = On)

23" 8ms G2G LG.Display AH-IPS (Response Improve = On)

We have also provided a comparison of the U2413 against 3 competing professional grade monitors. Given the price point and market position of the U2413 it is likely that some buyers will want to compare with the high end NEC models in the market which we have tested. The NEC P241W (standard gamut model) was perhaps a little faster in practice than the Dell, but the PA241W (wide gamut model) was a little slower. The 23" P232W had impressed us in these tests and showed less noticeable motion blur in practice. Overall there wasn't a lot to separate these models really but the U2413 performed well enough in terms of response times.

24" 6ms G2G LG.Display AH-IPS

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

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

24" 4ms G2G AU Optronics AMVA (AMA = Premium)

We can also compare the U2413 against a series of other popular 23 - 24" models. The tests show that the other three screens all show a slightly less pronounced motion blur in these tests with a sharper moving image visible. However, they all introduce a degree of dark trailing, particularly on the U2312HM where it was quite apparent in practice. Again though, there's not much to separate the screens here.

24" 6ms 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 U2413 to have pretty fast transitions and low levels of motion blur, 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 U2413 performed well, although the overshoot in certain transitions was severe. 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 U2413 was pretty good overall. We had measured a pretty low average G2G response time of 7.9ms which was good, although we'd seen some high overshoot in certain transitions, especially when changing from dark to very bright / white shades. In practice it didn't feel quite as fast as some other models we'd tested like the U2713HM for instance. Keep in mind though that this is aimed at higher end uses and the semi-professional market and so the performance for gaming is obviously not a number 1 priority for Dell. It should still be perfectly adequate for most gaming, but those wanting to play fast FPS or competitive games may want to consider some of the more mainstream (and more suitable) models available, or better still, some of the 120Hz compatible displays out there.

On another note many gamers like to use exaggerated settings to make colours look brighter and more vivid. Wide gamut screens can serve this purpose well as they natively produces more saturated colours. This might not be strictly accurate but a lot of people prefer this more vivid and cartoony appearance and so it's useful that the option is available from the U2413. Of course if you want to revert to a standard gamut you can always switch to the sRGB mode too.

Additional Gaming Features
 

Refresh Rate Support - In a new test we will establish the maximum refresh rate supported by each display we review. While most screens have a recommended refresh rate, some do allow you to force a higher refresh rate if you desire. In some cases this can result in improved frame rates, which of course can be useful for gaming. However, in other cases while the screen might comfortably operate at a higher refresh rate, the extra frames are actually just dropped by the display, leading to juddering and stuttering playback. So in many cases, it holds no benefit anyway. We use a useful refresh rate testing tool to establish whether the screen can support a higher refresh rate input, and then whether it displays all frames properly or drops the extra frames in practice.

In the case of the U2413, the screen is designed to run at 60Hz refresh rate. Forcing a 75Hz refresh rate did display an image on the screen but it was very corrupted, both using a progressive and interlaced signal. This means it is not practically useable at 75Hz.

Aspect Ratio Control - The screen offers five options within the OSD menu for hardware level aspect ratio control. There are options to maintain the aspect ratio at 'wide 16:10', 'wide 16:9' or 4:3 which users will hopefully be familiar with. These will help maintain those specific aspect ratios for certain sources, stretching the image to fill as much of the screen as possible and using black borders to cover the sides (for 4:3 mode) or top and bottom (for 16:9 mode). It was good to see 16:9 included as a specific option as a lot of content is based on this format nowadays.

There is also then an option for 'auto resize' which retains the source aspect ratio no matter what it is, and fills as much of the screen as possible (black borders used where needed). This is particularly useful as it will automatically detect the aspect ratio and maintain it. This wasn't available on the U2412M and so some aspect ratios such as 16:9 could not be maintained at a hardware level. The U2412M only had options for 16:10, 5:4 and 4:3 so anything other than those would not be handled by the screen. In the case of the new U2413 this is handled via the 'auto resize' option without problem. The last option is for 1:1 pixel mapping which directly maps the source resolution to fill only the required number of pixels. Again handy for those wanting to maintain any source resolution and aspect ratio, without stretching the image at all.

Preset Modes - There is a 'game' preset mode available from within the preset mode menu. This seems to look quite similar to the standard preset mode and it gives you access to the dynamic contrast ratio if you want to use it, not that it really does anything in practice based on our tests. 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. As you will see from the next section, it also has a very positive impact on input lag.

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.

We have provided a comparison above against other models we have tested to give an indication between screens. Those shown with blue bars represent the total "display lag" as at the time of review we did not have access to an oscilloscope system to measure the response time element and provide an estimation of the signal processing. The screens tested more recently 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 Dell U2413 showed an average total display lag of 24ms during the initial tests in the standard preset mode, ranging up to 28ms maximum. This lag was not too severe, but a bit higher than we had seen from some other recent screens, and represented a lag of 1.5 frames. We measured half the average G2G response time as 3.95ms and so we can estimate that the signal processing is ~20.1ms in this mode. When switching to the 'game' preset mode we were very pleasantly surprised by the results. The screen goes blank for about 1.5 seconds when you switch to this mode and it seems that a large part of the signal processing is removed, presumably through bypassing of the internal electronics to a large degree. We measured an overall display lag now of only 9ms, and so the signal processing was estimated at a much lower 5.1ms. This game mode provides an overall lag which can be graded as CLASS 1 as described above and should be fine for most gamers.
 

Movies and Video

The following summarises the screens performance in video applications:

• 24" screen size makes it a reasonably small option by today's standards for an all-in-one multimedia screen, being quite a bit smaller than modern LCD TV's of course.

• 16:10 aspect ratio is less well suited to videos than a 16:9 format screen, leaving larger borders on DVD's and wide screen content which is commonly based on 16:9 aspect ratio.

• 1920 x 1200 resolution can support full 1080 HD resolution content.

• Digital interfaces support HDCP for any encrypted and protected content.

• Good to see that both DVI and DisplayPort are provided on this model, allowing you to connect your PC over DVI, and leave the DisplayPort free for an external device potentially. Also good to see HDMI included as that is very popular and widely used for external DVD and Blu-ray players.

• DVI and DisplayPort > Mini DisplayPort cables included in the box, but no "normal" DisplayPort or HDMI cables included.

• Light AG coating does not cause issues with reflections which glossy coatings can.

• Wide brightness range adjustment possible from the display, including high maximum luminance of ~342 cd/m² and a good minimum luminance of ~33 cd/m². This should afford you very good control for different lighting conditions.

• Black depth and contrast ratio are moderate for an IPS panel at 783:1 after calibration. Shadow detail in darker scenes should not be lost though as this should be ok for most movie uses. Those wanting to watch a lot of dark content may want to think about a VA technology based screen.

• Dynamic contrast ratio available but does pretty much nothing on this model.

• 'Movie' preset mode available but impacts contrast ratio a lot so should probably be avoided.

• Smart Video Enhance Feature available from the OSD menu. This is a new feature we've not seen on other Dell screens before. The feature automatically detects video (motion) in any window on the screen, and applies enhancements to the video. Only the video window is enhanced. Two different enhancement settings are available as well, those being "Movie"- suitable for movie or multimedia video clips, and "Advance" - User adjustable setting. This setting basically features tweaked (or customisable in the case of the "advance" option) settings for contrast, sharpness, offset, hue and saturation. It is designed to only impact video content on the screen so may be a useful feature to some, if you want to change the appearance of your video windows without impacting on the overall screen appearance.

• Wide colour gamut available from the backlighting system, so those who prefer brighter and more vivid colours for movies and videos can switch to the native gamut mode and benefit. sRGB emulation also available if you prefer standard gamut appearance.

• Good pixel responsiveness which should be able to handle fast moving scenes in movies without issue. Possibly some overshoot evident in changes from dark to light shades.

• Very good range of hardware aspect ratio options which should be able to scale and handle external devices easily. Nice to see an "auto" mode and 1:1 pixel mapping included.

• 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.

• Good range of ergonomic adjustments available from the stand. Should be easy to obtain a comfortable position for multiple users or if you want to sit further away from the screen for movie viewing.

• No 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 or audio connections but it is compatible with Dell's SoundBar.

• Picture in picture (PiP) and Picture By Picture (PbP) available if needed.

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

Dell U2410 and U2412M Comparison

I know many people are going to be asking the question: "which is better, the old U2410 or the newer U2412M and U2413 models?" The U2410 is going end of life now to be replaced by the U2413, which will then run along-side the U2412M. The distinction really is between a higher end semi-professional use monitor (U2410 and now U2413) and a more mainstream, multimedia orientated model (U2412M). This really does make them quite different to one another but we will try and provide a comparison of the three models here to help. I won't compare the various specs as they are not really relevant in practice and I'll look instead at the performance comparison based on our tests:

Dell U2410 vs. U2413 vs. U2412M Comparison

Colour Space

Like with the 27" range from Dell, probably the main difference between these three models is the colour space support. The U2410 and U2413 use wide gamut backlighting types (WCG-CCFL and GB-LED respectively) which offer an extended gamut covering 102 - 103% of the NTSC colour space. This can also cover the Adobe RGB reference space as a result and extends considerably beyond the sRGB reference which is still widely used. The support of wide gamut is great if you have a practical use for it and are working with wide gamut content or want to match the Adobe RGB space properly. However, if you are working just with sRGB content, viewing it on a wide gamut screen can lead to issues of over-saturation and neon appearing colours and is difficult to manage for many users. Thankfully both screens include an sRGB emulation mode which is useful in those circumstances.

The U2412M on the other hand uses White-LED backlighting which can only cover the sRGB reference colour space. It would be referred to as a standard gamut screen. This is therefore easy and practical if you are just working with standard gamut content, but obviously of no use if you need to work in a wider colour space as it cannot support it at all. There is no sRGB mode provided as the native gamut of the backlight is already very close to the sRGB space thankfully.

The U2410/U2413 are perhaps more useful to colour enthusiasts, photographers and designers thanks to the wide gamut support, but for the general consumer, most will not need to use wide gamut and will only be concerned with the appearance of standard gamut (sRGB) content. As such they would not want the over-saturated colours and issues associated with trying to manage standard gamut on a wide gamut screen, and so a W-LED based model like the U2412M is more readily accessible to the average user. The U2412M is also a fair bit cheaper than the other models (even with the U2410 on end-of-line sales) so a decision regarding whether you truly need or want wide gamut may play a big part here.

Colour Depth

I'll also make reference to the fact that the U2410 and U2413 feature an 8-bit + A-FRC panel which can offer a colour palette of 1.07 billion colours if you have a relevant end to end 10-bit workflow (application, operating system, graphics card, interface etc). That is very rare and so to 99% of users this support of "10-bit" is largely irrelevant. It's 12-bit / 14-bit internal processing is designed to help improve gradients and signal processing as well. These kind of features are usually reserved for high end graphics screens such as the NEC PA series, but Dell included them here on the U2410/U2413 as well. The U2412M uses only a normal 8-bit colour depth and actually uses a 6-bit panel with FRC. It has a normal 8-bit signal processing as well. This is more than adequate for most users, especially given the aforementioned complexities with achieving a 10-bit workflow. If you do have such a workflow and want support of 10-bit content then the U2410 / U2413 would be a more suitable choice. I suspect many people just won't need it. Again the extra cost of the U2413 is related to this 10-bit support.

Features and Specs

The U2412M is missing a few of the extra features found on the other two models like the card reader, factory calibrated preset modes, an HDMI interface, DisplayPort cable and touch sensitive buttons. The move to a LED backlighting units has brought about energy and environmental benefits for the U2412M and U2413 compared with the older CCFL unit and helps offer a thinner screen profile. One final thing to note of importance is that the new U2413 uses a light AG coating and so does not suffer from the grainy, dirty appearance in some uses that the heavy AG coating of the U2410 and U2412M had. A positive change there for sure.

Performance

I've included a table summarising these screens side by side based on the testing we have carried out and on my opinions. The screens are colour marked as green (winner), amber (second place) or red (loser) in each category which should be self explanatory. Where I was not able to separate the two they are shown in grey. I will justify each result below:

• Approximate price - at the time of publication the new U2413 is ~£108 more expensive than the old U2410 which is going end-of-life. It is considerably more expensive than the U2412M as well (£231 more). This is logical on the most part given it is very new, and as it features some higher end extras and is more aimed at professional users than the mainstream U2412M.

• Features - The U2413 wins here as it's retained some of the extras of the old U2410 (card reader, touch sensitive buttons) but has added a few extras like USB 3.0 support, daisy chaining and hardware calibration. The U2412M is lacking quite a few of the extras that the other two models had so is lacking in this area, going some way to explaining the lower cost of course. I suppose really the value of these features depends on what you're looking for from your screen and what you need.

• Screen coating - The new U2413 has a light AG coating and so does not suffer from a dirty, grainy appearance that the heavy AG coating on the U2410 can bring. The U2412M also had an aggressive AG coating but we did feel at the time that it was perhaps slightly less than the U2410. The coating on the new U2413 is much lighter though.

• Interfaces - The U2410 and U2413 are ahead of the U2412M here, but go about it slightly differently. The U2410 had D-sub, composite and component inputs, but arguably most of those are "old" requirements now and probably rarely used. The U2413 instead offers a Mini DisplayPort connection and daisy chaining capabilities via DisplayPort which are probably more useful for the modern market. Both are a little ahead of the U2412M which didn't offer composite, component, Mini DisplayPort / Daisy Chaining or even the very popular HDMI.

• sRGB colour support - Being W-LED based the U2412M is a native standard gamut screen and so its use with sRGB content is simpler than the other two for most users. The U2413 carries the more reliable factory calibration in the sRGB mode than the old U2410 did which is important to users who might not have other means to calibrate their screens.

• Extended gamut support - The U2410 and U2413 have a wide colour gamut, the U2412M does not.

• Office and Windows - There's not a massive amount to separate them on here although I've marked the U2413 as more suitable thanks to the lighter AG coating. The addition of USB 3.0 is also useful and helps put the new U2413 ahead of the old U2410. The U2410 remains ahead of the U2412M since it has a card reader and a wider range of options for colour space and 10-bit support if needed.

• Viewing angles - No real separation here

• Movies Overall - The U2413 and U2410 have more video connections which some users might need, but the contrast ratio on the older U2410 was not great. The U2413 might not have as good a contrast ratio as the U2412M but offers more additional features.

• Responsiveness - Not a massive amount to separate them all here really. They all behaved quite similarly in practice with low levels of motion blur and good pixel response times. The U2412M showed a pretty noticeable dark overshoot, but we know from our more advanced oscilloscope method that the new U2413 suffers from some high overshoot in certain transitions too.

• lag - hard to accurately compare since the U2410 and U2412M were only tested using the old stopwatch method. I've provided the figures for reference but keep in mind the U2413 figures are far more accurate than the old U2410/U2412M measurement. The U2413 does feature a useful 'game' mode which greatly reduces the lag, and we'd seen a similar positive result with the old U2410 at the time as well.

• Black depth - We achieved the best result with the U2412M after calibration (0.13). The U2413 (0.16) had made some positive improvements compared with the old U2410 (0.22) though which was good.

• Calibrated Static Contrast Ratio - Again the U2412M performed best here with a static CR of 947:1 which was excellent for an IPS panel. The U2410 was quite poor in this area really at 541:1, but the U2413 had made some nice improvements thankfully, but still only provided a moderate contrast ratio of 783:1.

• Dynamic Contrast Ratio - None worked that well at all really, although the 1402:1 offered by the U2410 was higher than the other two which didn't seem to offer any practical benefit at all.

As we'd concluded with the 27" U2713H as well, overall the U2413 felt like a worthy successor to the popular U2410. There's been some positive changes made including a much lighter AG coating, hardware calibration support, USB 3.0 inclusion, an improved black depth and improved contrast ratio. Thankfully Dell have not cut corners and have kept some of the premium features from the old U2410 as well with touch sensitive buttons, a wide colour gamut backlight, 10-bit colour depth and even the integrated card reader. Dell may have done away with a couple of things like the composite, component and D-sub connections but in today's market they're not really missed and are easily out-weighed by the new things they've added instead. The replacement of the U2410 is certainly justified we think. Of course this is still aimed more at professional users and so carries a higher price point than some of the more mainstream models out there including the U2412M (by quite some margin), but the extra features justify that price point well, and to be fair it's very competitively priced.

The more mainstream U2412M will be available along side the U2413 and still fits a niche well. It may not have the wide gamut  backlight, 10-bit colour depth or the hardware calibration support, but then many users just don't need (or even want) those anyway. It still brings you a good range of connections and features and unless you specifically need the extras of the U2413, still makes an excellent choice for your average user. It even offers some stronger performance when it comes to black depth and contrast ratio which was pleasing, and is very well priced.

Conclusion

This has been a very extensive review and we've had a lot of time to test the new U2413 fully. As we've said in the previous section the U2413 seems a very worthy replacement to the U2410 and a great alternative to run along-side the U2412M which still has it's place. We won't repeat all of those points again here but please read the comparison section above for more information and importantly to help you understand where the differences are.

From a performance point of view we were pleased with the out of the box performance, including the reliable Adobe RGB and sRGB colour space emulations and factory calibrations. The results after software profiling were pleasing although the contrast ratio was not as good as we would have hoped from a modern IPS panel. The hardware calibration was pretty inflexible in terms of device support, and the lack of any reporting functionality from Dell's software was a shame. Nevertheless it seemed to produce good results on the most part, especially being useful with the Adobe RGB emulation and for retaining tonal values to produce smooth gradients. Obviously the GB-LED backlight delivers a wide gamut and the AH-IPS panel used offers 10-bit support as well for those users who need either. The backlight dimming was fine as well, with PWM not being needed to control the backlight within a comfortable range. Below a setting of 20% brightness PWM was introduced but at a very high frequency which is unlikely to cause too many problems for users.

One area which disappointed us again was the uniformity correction. We had seen from our U2713H tests that it didn't seem to work at all, but had been more impressed with its implementation on the U2913WM since. With the U2413 the function did work, but it was practically unusable since it wasn't available in any of the main modes you'd want to use it, and even when you did find one where you could, it would lock the brightness at a setting which was too high and uncomfortable for any prolonged use. Along with support for more hardware colorimeter tools for LUT calibration, this is an area we'd like to see Dell address if they can.

Dell have made some positive changes with the new screen though, and the move to a lighter AG coating is very welcome. The addition of USB 3.0 and the return of the card reader was also very nice. The lag was also nice and low when using the 'game' preset mode, and we are grateful to Dell for including a mode to help bypass some of the signal processing. The pixel response times were also decent, although there were some issues with overshoot in some circumstances which was a shame. A more balanced and better controlled overdrive impulse would be welcome here.

Like the U2713H we feel it falls a little short of being a truly high end professional screen, but given its retail price is ~£273 less than something like the NEC PA241W it is still an interesting alternative. It carries some of the performance features you might want and certainly delivers with a wide range of connections, adjustments and extra features. Another very good screen from Dell and well worth considering if you want something high end, but at a very reasonable cost.