Dell ST2220T
Simon Baker, 21 February 2011

 

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It's not your average monitor, but we thought it would be very interesting to take a look at Dell's new 21.5" ST2220T display. What separates this from your average screen is that the ST2220T uses optical touch screen technology to offer a nice cross over for those wanting a tablet-like touch solution. Even if you ignore the touch screen capabilities, the screen itself is still a very interesting model. It is a 21.5" sized model using IPS panel technology. It has a unique design and a decent range of options and extras. It even has a glossy panel coating which is bound to attract some interest, as the traditional Dell anti-glare (AG) coating has been a sore subject for some people with recent monitor releases. We wil review the ST2220T in our normal way as a general monitor solution, and will of course take a look at its touch-screen functionality as well. Let's start by taking a look at the specs:

Size

21.5"WS

Colour Depth

16.7m (6-bit + AFRC)

Aspect Ratio

16:9

Colour Gamut

72% NTSC colour gamut (CCFL)

Resolution

1920 x 1080

Viewing Angles

178/178

Response Time

8ms G2G

Panel Technology

e-IPS

Contrast Ratio

1000:1 and 50,000:1 DCR

Interfaces

DVI (HDCP), D-sub, HDMI

Brightness

250

Colour

Glossy black bezel and stand

Special Features

Tilt stand only. Optical touch screen technology. 3x USB 2.0 downstream ports. Glossy panel coating

Buy

PCBuyIT.co.uk


Above: the Dell ST2220T shown tilted to a low angle

The ST2202T is an attractive design in my opinion. There is a glossy black bezel around the panel on all sides which is about 24mm wide. At the bottom edge there is a wider patterned section which acts as the stand and contains the stereo speakers. This is about 60mm thick at the widest points (including the feet). The overall appearance is sleek and attractive and it's a fairly unique design, a little like the Asus MS246H we tested back in March 2010.

The screen coating for this model is a glossy solution which does add a completely different feel to the screen as compared with other popular Dell models. It helped give a sharp and vivid image I thought and was very nice to look at. It did produce some extra reflections of course in certain lighting conditions, and this could be an issue if you have a window or light source behind you when you work. If you are using the touch-screen capabilities then the coating will pick up finger print marks quite a lot, but Dell do include a small cloth for wiping the screen at least. Screen coating is down to personal taste of course but some people have found the aggressive AG (anti-glare) coating of the recent Dell U series screens to be an issue.


Above: Rear views of the screen and stand. Click for larger versions

The back of the screen is also a nice glossy black and everything looks smooth and well designed. There is a simple Dell logo on the back and the whole unit looks very nice in my opinion. The materials were of a high standard and build quality felt excellent.

The stand is a silver colour and has a non-slip plastic base. This stand is used to control a very good range of tilt, from an almost flat position against the desk, up to a vertical position. The images below demonstrate this range of tilt. You can lay the screen flat on the desk as well by folding the tilt stand away if you like. The screen goes to this flat level since it is a touch screen and so some may want to operate it at that angle. The operation of this tilt was very smooth and easy to use.

There is no height adjustment available from this screen. Normally I would mark this as a negative if a stand did not offer a height adjustment as I think it's a useful feature to obtain a comfortable viewing position. However, it's a bit different due to the touch screen nature and the ability to operate from an almost flat position. It's actually possible to get a comfortable position for normal desktop use anyway which is good. Of couse there's also no swivel or rotate function available from this screen.


Above: side view of the screen showing USB and headphone connections

The screen has a fairly thin side profile as well as shown above. On the left hand edge are 3x USB 2.0 ports for easy connection of external devices. This is great to see included as they can be very handy for cameras, printers etc. It might have also been nice to see a couple on the back of the screen with the video connections, as you may have some devices you want to leave permanently connected and so want to keep the wires hidden out of the way behind the screen. The popular Dell U series has additional ports on the back as well as on the side, so a shame there weren't a couple more included here I think. There is also a headphone connection on the left hand side if you don't want to use the intergrated stereo speakers. Unlike some of the U series of screens there is no card reader available here sadly.

One of the key selling points of the ST2220T is its touch screen capability. We will test this later but I thought I'd mention a bit about its capabilities here as well. The screen uses optical touch technology for which you can use your finger, a stylus (min diameter of 7mm) or any pointer device. The touch capabilities include mouse functionality (click, drag, double-click and right click) along with supported Windows 7 multi-touch gestures if you are using that operating system. Dell's spec states that there is a typical touch response time of 15ms and that there is a +/-2.5mm accuracy over 95% of the touchable area.

The screen also includes integrated 2W stereo speakers which are housed in the bottom of the screen as shown above. These should be more than adequate for general office noises and  average use. There is an audio input on the back as well to connect from your PC and the HDMI input can also take sound as well as video. The headphone jack on the left hand side of the screen can be used for discrete listening.

The back of the screen features a reasonable range of interface options with DVI-D (HDCP supported), HDMI and D-sub available. It may have been useful to see an additional HDMI or a DisplayPort connection here as well, but there's a decent range nonetheless.
 

The back of the screen also features a useful cable holder to tuck your cables nicely out of the way as shown above.


The OSD menu buttons are located on the right hand edge of the screen and there are four there above the power button. The power LED glows a subtle white colour during normal operation. The OSD menu buttons are not labelled in any way. Pressing any of the buttons brings up the small start menu in the bottom right hand corner where there are indicators on the screen itself telling you what each button does. It was easy to use and navigate, and very intuitive as we had found with the Dell U series screens. With the buttons out of sight on the edge of the screen it was perhaps a little more tricky to get used to at first. There was quick access (once you've pressed any button to bring up the small menu) to the preset modes and brightness and contrast controls although these can be customised through the 'personalize' menu when you get into the main sections.

The OSD menu has all the usual options you would expect. The color settings menu gives access to the preset modes and there are options for standard, multimedia, game, warm, cool and custom RGB.

The Dynamic contrast ratio control is located in the display settings section but is only available when using the 'game' preset mode. You will also notice that you can control the 'response time' setting here as well which we will test later on in our gaming section.

 

In terms of power consumption the manufacturers spec states 'typical' usage of 28W during operation, or up to 55W with USB active. In standby, Dell say that the screen will use 1W of power.

State

Power Usage (W)

Factory Default

28.0

Calibrated Settings

22.1

Standby

1.1

We tested this ourselves and found that out of the box the screen used a very low 28.0W of power which was as advertised by Dell. Once calibrated power consumption was 22.1W (see calibration section) since we had changed the OSD brightness control to 36% here. In standby the power consumption was only 1.1W, so again, as advertised. The screen remains pretty cool during operation, even after long periods of use and hardly gives off any heat from the top of back. There is a very faint electronic buzz if you press your ear against the screen but it's not something you'd notice in normal use.



Colour Accuracy, Black Depth and Contrast

The Panel and Backlighting Unit

The Dell ST2202T utilises an LG.Display e-IPS LM215WF5-SLA1 panel and is capable of producing 16.7 million colours. The panel itself actually uses a 6-bit colour depth with frame rate control (A-FRC) to produce the 16.7m colours. This is different to regular 8-bit IPS matrices, but this is likely a measure taken to achieve a lower price point for these modern lower-cost displays. Studying detailed information from LG.Display's datasheet confirms the panel is indeed 6-bit+AFRC.

The screen can offer a colour gamut covering approximately 72% of the NTSC colour space as it uses standard gamut CCFL backlighting. This colour space is approximately the same as the sRGB reference but is less than modern wide gamut screens of course.

Testing Methodology

An important thing to consider for most users is how a screen will perform out of the box and with some basic manual adjustments. Since most users won't have access to hardware colorimeter tools, it is important to understand how the screen is going to perform in terms of colour accuracy for the average user.

I restored my graphics card to default settings and disabled any previously active ICC profiles and gamma corrections. The screen was tested at default factory settings using the DVI interface, and analysed using an X-rite i1 Pro spectrophotometer combined with LaCie's Blue Eye Pro software suite. An X-rite i1 Display 2 colorimeter was also used to verify the black point and contrast ratio since the i1 Pro is less reliable at the darker end.

Targets for these tests are as follows:

  • CIE Diagram - validates the colour space covered by the monitors backlighting with the black triangle representing the display

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

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

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

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

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

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


Default settings of the screen were as follows

Monitor OSD Option

Default Settings

Brightness

75

Contrast

75

Preset Mode

Standard


Dell ST2220T - Default Factory Settings

 

Default Settings

luminance (cd/m2)

222

Black Point (cd/m2)

0.19

Contrast Ratio

1169:1

 

The out of the box settings for the ST2220T were actually pretty decent in most cases. The screen felt bright and colourful and the glossy coating really helped bring out the detail and add something to the 'feel' of the panel. The colours felt even and fairly balanced although there was a very slight tendency towards green. The screen was a bit too bright though at its default 75% brightness setting, so this would need to be turned down for most users in normal lighting conditions to get a comfortable setting.

 

The CIE digram confirms that the backlighting offers a colour gamut which covers the sRGB reference well, extending a little beyond that space along the blue > green edge but not by much. This does confirm that this is a standard gamut model of course as wide gamut CCFL backlighting would extend far beyond this reference. The default gamma setup was good with only a 2% deviation from the 2.2 target. White point was also very good being only 1% out from the 6500k at 6414k. The luminance was too high though being recorded at 222 cd/m2. This did give us a very good black depth though at 0.19 cd/m2, which produced a 1169:1 static contrast which was excellent for an IPS panel. Colour accuracy was also moderate with an average dE of 2.5. This did range up to 6.6 maximum though in blue shades. Apart from the high brightness (which is easy to just adjust through the OSD menu), this default performance was pretty good and should be adequate for most regular users without the need for further calibration. Obviously a colorimeter could help you obtain even better colour accuracy, but at least the gamma and white point were well set up out of the box.

 


Dell ST2220T - Default Factory Settings, Custom RGB Preset

 

Monitor OSD Option

Default Settings

Brightness

75

Contrast

75

Preset Mode

Custom (RGB)

RGB

100 / 100 /100

 

Default Settings,
Custom RGB preset

luminance (cd/m2)

219

Black Point (cd/m2)

0.19

Contrast Ratio

1154:1

 

I also tested the screen at default settings after switching to the 'Custom (RGB)' preset mode. This gives you access to individual control over the red, green and blue channels for calibration procedures. I did want to check whether this returned any more accurate results than the 'standard' preset. There was not really any difference in this preset. The measurements were all within the same approximate percentages from the targets as they had been before in the 'standard' mode. Colour accuracy was slightly better on average now, with an average dE of 2.0 (instead of 2.5). However, maximum dE was now 7.0 instead of 6.6. There's no real benefit in just switching to this preset without further calibration steps, but it is useful to use if you are doing anything more as the control over the RGB channels is useful.

 

 

 

Calibration Results

 

I wanted to calibrate the screen in each of the main preset modes to determine what was possible with optimum settings and profiling. I used the X-rite i1 Pro spectrophotometer combined with the LaCie Blue Eye Pro software package to achieve these results and reports. An 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 ST2220T - Calibrated Settings

Monitor OSD Option

Adjusted Setting

Brightness

36

Contrast

75

Preset Mode

Custom (RGB)

RGB settings

97, 91, 96

 

Calibrated Settings,
Custom RGB preset

luminance (cd/m2)

120

Black Point (cd/m2)

0.13

Contrast Ratio

925:1

 

I remained in the 'custom (RGB)' preset for this process so that I could adjust the controls from the OSD menu. I followed LaCie's calibration process through, adjusting the OSD settings in line with the recommendations made in the process, and then letting the software carry out the LUT adjustments at a graphics card level and create an ICC profile. The screen does not feature a hardware LUT calibration option so other than the OSD alterations, the rest of the process is carried out at a graphics card level in profiling the screen.

 

The calibration was a success. The slight deviance in gamma and white point was now corrected, and we had a much more comfortable luminance of 120 cd/m2 now as we had aimed for. We still had a very good black depth of 0.13 cd/m2 and an excellent static contrast ratio of 925:1. Colour accuracy was also corrected very nicely and we now had a dE average of 0.3 / maximum 1.0. LaCie would classify colour fidelity as being excellent now.

 

You can use our settings and calibrated ICC profile on your screen as well if you want. See our ICC profile database for more information. I tested the screen with various colour gradients which were very smooth and showed no sign of banding. There was only very slight gradation as well so this was very positive.

 

 

 

Calibration Performance Comparisons

 


 

I've plotted these measurements on the above graphs in comparison with some of the other screens we have tested in a similar size and market segment. Out of the box, default colour accuracy was very similar to that of the other 21 - 23" e-IPS models we have tested. The ST2220T had an average dE of 2.5 which was very similar to the 21.5" Dell U2211H (2.3) and 23" Dell U2311H (2.4). It was also very similar to the 23" NEC EA232WMi (2.4), NEC EA231WMi (2.7) and Viewsonic VP2365wb (2.5) displays. All these e-IPS panels offer a pretty moderate default colour accuracy which would probably be adequate for most casual users and pretty respectable when you consider the relatively low retail cost.

 

Calibration with a colorimeter/spectrophotometer can produce more accurate results of course and all these models are pretty close in terms of dE performance. The ST2202T is ever so slightly behind at 0.3 whereas some of the models shown here are 0.2 average dE. Nothing you'd really notice of course in practice. Don't forget that some of the models shown here also offer further advantages when it comes to colour critical work. Professional grade monitors like the NEC PA series also offer other high end features which separate them from some of these other models, including extended internal processing, 3D LUT's and hardware calibration. These comparisons are based on a small selection of tests, so it should be remembered that other factors do come into play when you start talking about professional use. For further information and tests of a high end professional grade screen with hardware LUT calibration, you may want to have a read of our NEC SpectraView Reference 271 review.

 

 

I've included a comparison of the black point and contrast ratio above as well. The ST2220T performed very admirably here, being one of the best of the IPS screens in fact. With a very low 0.13 cd/m2 black point, calibrated static contrast ratio was 925:1 which was excellent and only a little short of the advertised 1000:1. We'd actually achieved a little higher than this at default settings (see next section) but these results above factor in a post-calibration performance after grey scale, gamma, white point (etc) correction. The IPS based NEC EA232WMi was slightly better at 933:1, the TN Film based BenQ XL2410T was actually a little better at 996:1, and the BenQ EW2420's AMVA panel offered a fantastic contrast ratio of 2995:1. A very good performance from the Dell ST2220T here nevertheless.

 

 


Contrast Stability

I wanted to see how much variance there was in the screens contrast as we adjusted the monitor setting for brightness. In theory, brightness and contrast are two independent parameters, and good contrast is a requirement regardless of the brightness adjustment. Unfortunately, such is not the case in practice. In most monitors the brightness control in the OSD menu controls the intensity of the backlight unit, and so as you reduce this control you reduce the luminance. Black depth should also reduce at the same time, and hopefully maintain a stable contrast ratio across the range of adjustments. Where the brightness control does not change the backlight intensity it can have a significant impact on the contrast ratio.

We recorded the screens luminance and black depth at various OSD brightness settings, and calculated the contrast ratio from there. Graphics card settings were left at default with no ICC profile or calibration active. Tests were made using an X-rite i1 Display 2 colorimeter. It should be noted that we used the BasICColor calibration software here to record these, and so luminance at default settings may vary a little from the LaCie Blue Eye Pro report.

OSD Brightness

Luminance
(cd/m2)

Black Point (cd/m2)

Contrast Ratio
( x:1)

100

268

0.23

1166

90

250

0.21

1189

80

228

0.20

1140

70

213

0.18

1186

60

196

0.17

1152

50

178

0.15

1188

40

158

0.13

1217

30

137

0.12

1143

20

115

0.10

1150

10

91

0.08

1143

0

70

0.06

1159

 

Luminance Adjustment Range =  198 cd/m2

Black Point Adjustment Range = 0.17 cd/m2

Average Contrast Ratio = 1167:1

The brightness control afforded us a decent enough range of adjustments to the luminance of the screen. At the top end, a 100% setting returned us a luminance of 268 cd/m2 which is actually slightly higher even than the specified 250 cd/m2 from the manufacturer. This could be adjusted down to around 70 cd/m2 at a 0% setting which was decent enough. A setting of around 25% should return you a luminance of ~120 cd/m2 which is recommended for LCD screens in normal lighting conditions. That assumes no other settings are changed of course, but should give you a decent starting point and a more comfortable setting to save your eyes.

Black depth was excellent across the adjustments, ranging from 0.23 cd/m2 down to 0.06 cd/m2. Overall the static contrast ratio was very stable and there was an excellent average contrast ratio of 1167:1. I have plotted these results on the graph below.

 


Dynamic Contrast

The Dell ST2220T features a dynamic contrast ratio (DCR) control, which boasts a spec of 50,000:1

Dynamic contrast ratio involves controlling the backlight of the screen automatically, depending on the content shown on the screen. In bright images, the backlight is increased, and in darker images, it is descreased. For this test I would use the colorimeter to record the luminance and black depths at the two extremes. Max brightness would be recorded on an all white screen once the DCR has caught up. Black depth would be recorded on an all black screen.

The DCR feature is only available when you enter the 'game' preset but is not available in the 'multimedia' mode for some reason. I've never really found that Dell's DCR's do much in practice to be honest and have been a bit underwhelmed by their performance. Here is sadly no exception. When you enter the game mode and turn DCR on the brightness control is locked from the OSD menu. I carried out our usual tests, and even switching between a fully black and fully white image didn't seem to show any real variance in the backlight intensity. This DCR didn't seem to function at all as far as I could tell.

 

Game preset mode

Max luminance (cd/m2)

142

Min Black Point (cd/m2)

0.12

Max Dynamic Contrast Ratio

1182:1

The dynamic contrast ratio control didn't really work at all. We were left with a contrast ratio which was only really the same as our default static contrast ratio figure we had measured before. To be honest this 50,000:1 figure is exagerated massively anyway. Even if the DCR technolgy could control the full range of the backlight properly, you would only have a maximum luminance of around 268 cd/m2, and a minimum black point of 0.06 cd/m2. You can see this from our contrast stability tests above. This would only give you a maximum DCR of 4467:1 anyway so a long way off the advertised figure. If we took Dell's maximum brightness spec of 250 cd/m2, you would need a black point of 0.005 cd/m2 to achieve the 50,000:1 figure, something which clearly this panel is not capable of, even at 0% intensity.

 


Viewing Angles


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

Viewing angles of the ST2202T are very good, as you would expect from a screen based on an e-IPS panel. Horizontally there are very wide fields of view with a small contrast shift only really becoming noticeable from a fairly wide angle of about 45. Vertically, the contrast shift was a little more pronounced but the fields of view were still very good. The panel is free from any off-centre contrast shift which you see from VA matrices, and this is why IPS technology is so highly regarded in the colour enthusiast and professional space. It is also free of the very noticeable contrast and colour tone shifts you see from TN Film panels vertically. On a black image there is a slight purple hue when viewed from some wide angles, and from others, a moderate white glow. The glossy panel coating does reflect light quite a lot though so you do have to be careful when viewing from an angle not to catch windows or lamps reflecting from another position.

 


Panel Uniformity

Measurements of the screens luminance were taken at 35 points across the panel on a pure white background. The measurements were taken using BasICColor's calibration software package, combined with the X-rite i1 Display 2 colorimeter. The above uniformity diagram shows the difference, as a percentage, between the luminance recorded at each point on the screen, as compared with the reference point of a calibrated 120 cd/m2. This is the desired level of luminance for an LCD screen in normal lighting conditions, and  the below shows the variance in the luminance across the screen compared with this point. It is worth noting that panel uniformity can vary from one screen to another, and can depend on manufacturing lines, screen transport and other local factors. This is only a guide of the uniformity of the sample screen we have for review.

Uniformity of Luminance

The uniformity of the panel was moderate as a whole. The luminance was a little darker towards all four edges, particularly along the right and left hand sides. Here the luminance ranged down to 99 cd/m2 in the worst cases which was not too severe. 65% of the screen was within 15% deviance from the target at a central point which was ok but not perfect. It was very hard to notice this variation in practice but if you viewed an all grey background in a darkened room, you could just about pick out a slightly darker right hand side, but this was not easy to spot. I don't think the luminance uniformity should cause any real problems to a normal user.
 

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. Uniformity of the backlight was very good in this test. There was very minimal leakage at all, apart from a slight amount in the top left hand corner and a little along the lower left hand edge. You can notice this using the naked eye when viewing an all black background in a darkened room, but in practice you are unlikely to see any real issue her I don't think.

 


General and Office Applications

Normally I would rate a 20 - 22" sized screen down a little in terms of its use for office applications, but this would normally be down to its 'small' (by todays standards) 1680 x 1050 resolution. Thankfully in the case of the ST2202T, like the Dell U2211H, the panel used offers a full 1920 x 1080 resolution. This is the same as many popular 23 - 24" screens and it's good to see a high resolution on a smaller screen. The pixel pitch is obviously a little smaller than the larger screens since you are squashing the full resolution into a smaller screen diagonal. However, at 0.248mm I still felt it was comfortable for prolonged office use without text being too small. I'd found the 0.233mm pixel pitch on the Dell U2711 (2560 x 1440 resolution / 27" screen size) to be a little too small for my personal preference, but the ST2202T was not as severe. This 1080 resolution is suitable for some good side by side working which I think is always handy for office use.

 

The luminance of the screen was too high at default settings but not too bad. You are easily able to adjust the brightness control to reach a comfortable luminance for varying lighting conditions. A brightness setting of 25 - 30% should give you a luminance of around 120 cd/m2, and you can get lower should you desire, down to a decent 70 cd/m2. There's no preset mode for 'text' or 'internet' here, so you will need to calibrate one of your preset modes to a suitable luminance if you are using a lot of office applications. It should be noted that the brightness/contrast setting applies to all preset modes so you cannot save a setting individually for any given preset. I personally think that ambient light sensors and dynamic backlighting control can be useful for office work, but there isn't one available here sadly.

 

The screens ergonomics are limited here but do afford you a decent range of tilt which is easy to use and should allow you to get a position you want. For office use, it is a shame not to see height, swivel or rotate functions available though. The 3x USB 2.0 ports on the left hand edge are useful as well for connecting cameras, printers etc. A card reader might have been a nice added extra as well like some of the U series screens.

 

Both the DVI and VGA interfaces presented a clear and sharp image and there was very little difference noticeable to be honest. The DVI digital interface had a very slight edge so is obviously the preference if you can use it. The glossy screen coating does add a nice 'feel' to the screen and white text backgrounds appear clean and crisp, and free from any 'dirty' feel that some people complain about with aggressive AG coating on panels. It does however occasionally present an issue with reflections in some lighting conditions which you need to be careful of.

 


Responsiveness and Gaming

Before we get into the side by side screen comparisons I first wanted to have a look at the 'overdrive' feature Dell have built into this monitor. This option is available via the 'display settings' section of the OSD menu as shown above. Dell's spec for the ST2220T states that the screen has an 8ms G2G response time with overdrive activated. It also states a 14ms G2G figure when overdrive has been switched off, although if the function is truly switching off the Response Time Compensation (RTC) impulse then this perhaps should read as a 14ms ISO measurement instead, which would also be in keeping with modern e-IPS panels without RTC (e.g. NEC EA232WMi = 14ms ISO response time). We tested the screen using the PixPerAn tool with overdrive enabled and disabled and the results are captured below.

The screen was tested using the chase test in PixPerAn, a good bit of software for trying to quantify differences in real terms responsiveness between monitors. As a reminder, a series of pictures are taken on the highest shutter speed and compared. The images below show the best case example on the left hand side, and the worst case example on the right hand side. This should only be used as a rough guide to comparative responsiveness but is handy as a way of keeping a constant test of each screen.



21.5" 14ms LG.Display e-IPS (overdrive OFF)


21.5" 8ms G2G LG.Display e-IPS (overdrive ON)

As you can see there is a defined improvement in responsiveness when you enable the overdrive function on this screen. To be fair, even without this activated the moving car does not show any obvious ghosting images, but does show some fairly obvious motion blur. The camera captured a fairly noticeable trail image, even in the best case example, and this is in keeping with the non-overdriven e-IPS panels in screens like the NEC EA232WMi and ViewSonic VP2365wb. Once the overdrive is turned on the motion blur is reduced quite nicely although there is a very slight pale halo introduced as a result of the RTC impulse and some slight overshoot. This is just about detectable in the best case image above but a little bit more apparent in the worst case example. For gaming, I would certainly recommend having this function turned on as it does help improve responsiveness and there are very few artefacts to worry about thankfully.



21.5" 14ms LG.Display e-IPS (overdrive OFF)


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


23" 14ms LG.Display e-IPS

Overdrive = Off: The ST2220T performs almost identically to the NEC and ViewSonic models here, neither of which use RTC to boost pixel responsiveness. Those two models are rated with a 14ms ISO (black > white > black) response time and so this does back up the assumption that the spec of the Dell without overdrive enabled should really be 14ms ISO, and not 14ms grey to grey. Regardless, the screen behaves like these other models with the feature disabled.
 


21.5" 8ms G2G LG.Display e-IPS (overdrive ON)


23" 8ms G2G LG.Display e-IPS


24" 6ms G2G LG.Display H-IPS


24" 5ms G2G LG.Display e-IPS

Overdrive = On: With the overdrive function enabled the motion blur is reduced nicely and the responsiveness is better. It's not actually a drastic change when you switch between the two, but the improvement is there. The ST2220T performs quite similarly to the other Dell models shown here. The 23" U2311H has a slightly less pronounced blur, but there is slightly more of a white trail evident. The RTC impulse is a little bit more aggressive on the U2311H model which gives you this result. The 24" U2410 is very slightly faster than the ST2220T but nothing really that you'd ever notice in practice, and the 24" HP ZR24W is very similar again. I'd say that the ST2220T offers a very comparable performance to all three of these competing models really in normal use.

 


21.5" 8ms G2G LG.Display e-IPS (overdrive ON)


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


22" 3ms G2G Samsung TN Film + 120Hz

I've also included a comparison above against two gamer-orientated screens, both featuring heavily overdriven TN Film panels, and 120Hz technology. The pixel responsiveness of both of these is a little ahead of the ST2220T as you will probably expect and the 120Hz frequency allows for improved 120fps frame rates and the support of 3D content as well. The BenQ XL2410T does show some rather noticeable RTC overshoot in the form of dark trails behind the moving image (speech bubble and head) which is unfortunate, and a sign that the RTC impulse is too aggressive. The Samsung 2233RZ remains our champion in this test.

The Dell ST2220T should be perfectly adequate for most gaming but those wanting to play fast FPS may still want to look elsewhere, perhaps at some of the modern 120Hz TN Film models with super fast response times and support for 120fps frame rates and 3D content. If you do buy the Dell ST2220T then I would certainly recommend making use of the overdrive function which improves pixel responsiveness nicely.
 

  • Apsect Ratio Control - The ST2220T supports limited aspect ratio control options through the OSD 'display settings' menu. There are only options for 'full' and '4:3' though, so any other aspect ratios and 1:1 pixel mapping are not catered for via the hardware.
     

  • Preset Modes - There is a gaming preset mode available for those who want to set up a preset based on their requirements. The dynamic contrast ratio is only available when using this mode although didn't seem to work at all. The preset was a little more blue as well than our calibrated custom (RGB) preset model.

 


Input Lag

  

As usual I tested the screen in clone mode with a CRT to determine the level of input lag. This is something which can put off some gamers and is a delay between graphics card and monitor output. By hooking up a CRT you can show that  the LCD lags behind somewhat, which can affect users in some situations where they rely on the screen image being as fast as their inputs (e.g. fast FPS shooting games). Often, input lag is very low and probably wouldn't represent too much of a problem in real terms.

The input lag of the ST2220T was pretty good really, with an average delay of only 16.3ms. This ranged up to 20ms in the worst cases which again was not bad. This puts it on par with the Dell U2211H and only slightly behind the U2311H and U2410 in fact. With this level of input lag, users shouldn't find it a problem for most gaming to be honest.

 


Movies and Video

The following summarises the screens performance in video applications:

  • 21.5" screen size makes it a reasonable size for viewing movies, but fairly small by todays standards. With the availability of 23-24" screens now, you might find something bigger more suitable

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

  • 1920 x 1080 resolution can support true 1080 HD resolution content. Good to see a full 1080 resolution being used on a 21.5" screen

  • Digital interfaces support HDCP for any encrypted and protected content

  • Fairly decent interface options available with 1x DVI, 1x HDMI and 1x D-sub. Might have been good to see DisplayPort available as well

  • Black depth and contrast ratio are excellent and some of the best we have seen from an IPS panel. Detail in darker scenes should not be lost

  • Dynamic contrast ratio is available but doesn't really work at all sadly.

  • Multimedia preset mode is available. This looked fairly similar to our calibrated custom profile. might be useful to some

  • Good pixel responsiveness meaning fast moving images should be fine. I would recommend having overdrive enabled.

  • No backlight bleed along the top and bottom edges which is great, as this could prove distracting in movies, especially where black borders are present. Some slight leakage from the top left hand corner and left hand edge, but nothing too severe and shouldn't present any real problems in movie viewing.

  • Wide viewing angles thanks to IPS panel technology making it suitable for viewing from different positions and for multiple viewers without issue

  • Decent tilt adjustment available but otherwise very limited. Might present a problem when trying to find a comfortable position for the screen, particularly with multiple viewers..

  • Integrated stereo speakers might be useful for 'light' sound and general use. The headphone socket is also useful for quieter viewing.

  • Glossy panel coating may present problems with reflections depending on your viewing position and lighting conditions. Keep it away from a window as they are particularly noticeable.

 


Touch Screen Capability

To take advantage of the touch screen capabilities of the ST2202T the screen must be connected to your PC's USB port using the provided cable. This connects to the upstream interface on the back of the monitor, and is also used to allow the 3x USB 2.0 downstream ports on the side function. There is a driver package supplied on the CD-rom or available from Dell's website which must be installed first. There is only support for Windows Vista and Windows 7 officially, and I could find no information on using this function with Windows XP. Mac OS is also not officially supported at this time.

The touch screen allows you to interact with the computer in a similar way to a mouse as follows:

  • Tap the screen once for a single mouse click.

  • Tap the screen twice in quick succession for a double mouse click.

  • Touch down and then move your finger to drag an object.

  • Touch and hold for a right mouse click.

  • To select a menu option, touch down on the menu, then move your finger to the required option, then lift your finger to select the option. Alternatively, tap the menu, then tap the option required as you do with a mouse.

The touch screen does not require much pressure to sense a touch either and for best results you have to point at roughly right angles to the screen and keep the rest of your hand clear of the glass. You can use your finger or a stylus which offers a little bit more accuracy. I found the finger touch to be perfectly useable though once you've got accustomed to the 'aim' and have used it for a few minutes. There was only minimal lag as well which was good, nothing which should cause you problems in practice I don't think. Dell rate this lag at 15ms incidentally.

 

I took the above video which shows the touch screen in operation in a series of functions as explained below. This was connected to a Windows 7 machine.

  • Simple one press activation - you will spot there is a small target and 'splash' when you press the screen showing where you have touched

  • Dragging and moving the control panel window around. This is easy to do and you can spot the slight lag as you do this, but it's not too bad I don't think.

  • Double clicking to make the control panel window full size and then small again. This is very easy to do and the screen responds well.

  • Dragging the control panel window again off the screen which activates the Win7 split screen viewing automatically

  • I then zoomed the camera in to show the right click function. You have to press and hold the screen for about 1.5 seconds. A circle then appears and goes around your touch-point. When you release the screen the right click menu appears. This is one area which is of course a little more cumbersome than using a mouse as you have the added press and hold in there. When you start trying to copy and paste it becomes quite a drawn out process with all these holds.

  • I then clicked into the address bar (after missing the first press!). On the left hand edge of the screen a small app appears. When you press this, it pops out a little way allowing you to click it. This in turn flashes a touch screen keyboard into view. This is easy enough to use and offers a full QWERTY layout

  • I then demonstrate the dragging and scrolling in an internet window. First I use the scroll bar and drag that up and down which operates well. I then just press, hold and scroll the same webpage using the touch screen functionality which is good.

  • Lastly I again drag the control panel window around for good measure.

 

 

I then did a shorter video which shows you the multi-touch functionality of Windows 7. You can, with two fingers, pinch and pull the screen to zoom in and out, very much like you can on an Apple iPhone / iPad. You can also click and then highlight text, but this is a little more tricky to get used to and certainly not as easy as using a mouse.

 


Conclusion

I really enjoyed using the Dell ST2220T actually, as it was something a little different to other screens we have tested. If I ignore the touch-screen capabilities for now, the performance of the screen itself was excellent I thought. Factory set up of gamma and colour temperature were very good and colour accuracy was decent enough for most casual users. The black depth and contrast ratio were excellent as well for an IPS panel which was a great result. Once calibrated the performance was of course even better. I had no real complaints about the viewing angles or uniformity either really. Yes, there were some slight variations in luminance uniformity along the sides, but nothing too severe and the screen was pretty much free from any backlight bleed. The response time and input lag was also very good and on par with other modern fast IPS panels in this regard.

I personally liked the sleek design of the screen as well and it looked very nice sat on the desk. While it is a bit of a shame to be missing height adjustment, I didn't really find it too much of a problem in my personal use, and the tilt range was excellent and easy to use. The glossy panel coating did add to the 'feel' of the screen and appearance of the image which I liked. Unfortunately it was a little too reflective in some conditions. The touch-screen support was also a nice feature and fun and easy to use.

Overall the performance of the monitor itself is very comparable to Dell's popular U2211H model, just with a few significant changes like the different design, integrated speakers, added touch-screen support and a glossy panel coating. I suppose many people would not have the need for the touch screen functionality day to day, but the screen should not be dismissed as just a standalone monitor I don't think. The ST2220T does cost a little bit more, being priced at ~270 GBP at the time of writing, compared with the 220 of the U2211H. However, the extra 50 for the additional features is very reasonable I think. As a touch screen monitor it is a very nice solution I think, but even if you forget it has that support the ST2220T is a very nice 21.5" IPS screen which is well worth looking in to.
 

Pros

Cons

Good default setup and great black depth / contrast ratio

Disfunctional dynamic contrast ratio

Fast response time and low input lag

Although offering a decent tilt range, no heigh adjustment from the stand

Glossy screen coating improves the feel of the screen, and touch screen support is very useable

Reflections potentially an issue due to glossy screen coating

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