LCD, David vs. Goliath: Iolair vs. Dell - BeHardware
>> Miscellaneous >> Monitors

Written by Vincent Alzieu

Published on April 4, 2008

URL: http://www.behardware.com/art/lire/712/


Page 1

24 inches: MVA vs. PVA

24 inches: MVA vs. PVA
24 inch screens gain even more ground aided by successive price reductions. The biggest stride is made by Iolair as they offer a 24 inch for roughly 300 Euros, the price of a 22 inch, with an MVA panel and DVI (HDCP). An immediate advantage compared to the very good Iiyama which has been popular these past few months is the Iolair screen that isnít subject to a poor lower viewing angle that darkens.


At the same time, Dell releases its 2408WFP, which has a PVA panel. The price is noticeably higher (a mere double) but the approach is a bit different. The 2408WFP wants in some way to never go out of style thanks to much better than average finishing touches, finer materials and much more developed functions.

The duel turned out to be extremely interesting with some unexpected surprises Ė sometimes good. Other times, the opposite occurred concerning the Dell. So what happened? At any rate, forget about the figures communicated in the characteristics. This test illustrates once again to what extent they are imprecise and especially misleading.
The tests
We run tests for reaction time in games, delay of display, and video rendering (SD, HD 720p, HD 1080p). We also evaluate ergonomics, viewing angles, the quality of upscaling, and the panel's brightness homogeneity. In short, we look at all aspects of a screen.

For color fidelity we use the LaCie Blue Eye Pro colorimeter, based on the Gretag tool and combined with the new LaCie software suite. More evolved than the previous version, this helps us to compare a monitorís display quality (color spectrum and DeltaE) in standard settings and after calibration. Results are sometimes surprising as itís often best to take the time to manually adjust colors (or at least contrast, brightness and color temperature).

The results of our study of 18 standard patches make it possible to create a table visually resituating the variation of colors compared to an ideal grey scale.

Rather than a response time measurement with an oscilloscope, we photograph the monitor in action. This is an effective way of capturing afterglow. The program used is Pixel Persistence Analyzer (or PixPerAn for those more familiar with it). Pictures showing these ghosting effects are captured with a Canon 350D at a shutter speed of 1/1000 s. We take 50 pictures in burst mode for each test to precisely measure the progression of afterglow between images. Otherwise, we haven't given up on the practical tests in games, HD and DVD video, web surfing, etc.

Finally, we measure the delay to display images compared to CRT monitors.

The test computer is self-assembled, has an AMD Athlon 64 3500+ processor and NVIDIA GeForce 7900 GTX card.


Page 2
Color rendering

Color rendering
The plot thickens starting with the first test, color rendering. Iolair modestly went with a normal non-extended gamut panel. It may appear less attractive than the promise of a wide gamut from Dell, but this is an assumption you especially shouldnít make.

To start with, neither monitor can be considered accurate with presettings. The Iolair produces satisfactory and coherent colors with nothing particularly too wrong. Unfortunately, itís another story for the Dell to the extent that this defect (and others discovered later in other tests) justified Dell sending us a second model, which sadly confirmed our initial results.

You may recall the larger the difference between actual and ideal colors, the higher the DeltaE value and the less the screen is accurate.
More precisely, here is how to interpret the graphs :
- Delta E > 3 : the desired color is noticeably different from the one on the screen.
- 2 < Delta E < 3 : color quality is satisfactory, but a graphic designer probably wouldnít be content
- 1 < Delta E < 2 : colors are accurate.
- Delta E < 1 : the result is perfect.

Itís a cold shower, all the more so unexpected given that the previous Dell 2407WFP-HC is identical to the 2408 on paper (and we can even ask how Dell justifies the name change). Moreover, the former model was properly adjusted but wasnít even as good as the previous 2407WFP (without the ĎíHCíí). Apparently, itís something we have to get used to ; as the years pass, settings become increasingly worse. This year, all evidence suggests that the color tables integrated to panels no longer take into account the specifics of each monitor. Wide gamut pre-settings are catastrophic with completely unnatural tones (gaudy red, supernatural greens, etc.). Here, the least poor settings are those in sRGB and thus we lose the wide gamut. At any rate, this is only of interest if your source documents were created in a similar color space, which isnít the case for any compact or classic bridge. The same goes for movies as well. Nevertheless, we have to honestly say that colors are poor even in sRGB mode and very far from what the competition has been capable of for several months now.
The Dell 2408WFP

PVA 6 ms : Dell 2408WFP

To put some numbers on these poor results, here are a few values. The entire spectrum is affected!

By default, on the 1st unit tested, color temperature was 7700 K in white and 6900 K in black. As you can see dominances are varied and there is no pattern that would be easy to correct manually. Gamma varies from 2.2 in black to 2.6 in white. The average difference between ideal colors and those actually displayed was 5.1 with satisfactory grays (except the gamma which prevented more progressive gradation) and a dE in blue which had a high of 16.5 !


PVA 6 ms : Dell 2408WFP
Unfortunately, the second screen tested wasnít any more accurate. In addition, we are also concerned about the very mediocre consistency of results between the two units. In general, they are identical: an average dE of 5.5, satisfactory grays, unruly blue and a gamma which is accentuated in going from black to gray. However, in more detail, it was disturbing to then find a color temperature of 9000 K, a dE in blue as high as 20.3, etc.

So itís therefore more than just a fear but rather almost a certainty: a generic color profile shouldnít make the 2408 perfect. For those who purchase this model, itís imperative to calibrate with a sensor in order to have accurate colors.

In sRGB, in both cases itís a bit better. The difference (average dE) drops to around 4.5, red loses its fluorescent aspect, dE goes down to 11, and color temperature is at a preferable 6800 K. However, it still cannot be considered good!

Is this Dellís fault? Yes, but not only. PVA panels such as the one used in this monitor are produced by Samsung which stuck them with poor settings. However, Dell could have taken the time to verify and correct them. Moreover, it seems incredible that this screen was able to leave the factory in such as state.
The Iolair MB24W: itís significantly less dramatic!

MVA 6 ms : Iolair MB24W

The starting average dE for the MB24W was 3.8 and this screen may appear very good in comparison to the Dell; however, it can be greatly improved with manual adjustments. Reduce green to 40 while red and blue are still at 50. The average difference is then at 2.8 or honestly one of the best scores weíve seen.

MVA 6 ms : Iolair MB24W
After calibration
In both cases, there are good results. The sensor works its miracles and all of the Dellís colors are remedied in dE and gamma. In the end, Ďíallíí you have to do is spend another 300 Euros (or dollars) for accurate colors. This means it can get very expensive!

PVA 6 ms : Dell 2408WFP


MVA 6 ms : Iolair MB24W



Page 3
Contrast, grays, homogeneity

Contrast measurements
PVA panels are historically good in contrast thanks to black levels that are normally very deep. This was the case for the second Dell 2408 tested. The first was disappointing with a contrast ratio measured at "only" 750:1 (and therefore below average for PVAs). On the second model, we found more standard values.

Likewise, results from the Iolair MB24W were not surprising even if they were significantly less impressive than those from the second Dell. This is only normal as MVA panels do not have the same depth in black.


PVA 6 ms : Dell 2408WFP


MVA 6 ms : Iolair MB24W
Grays
This test usually enables us to see differences in colors and how measurements translate into practice. Here, the two screens have rather correct grays, while other parts of the color scale are less accurate. Nevertheless, this will show you:
1 : the potential color dominances in grays
2 : the consequences of an unstable gamma


PVA 6 ms : Dell 2408WFP


MVA 6 ms : Iolair MB24W
Panel homogeneity
We rarely show you panel homogeneity test results because this can mislead readers more than anything else. Already, the results from two screens in the same series can vary depending on transport. Beyond that, the measured differences may seem large and they should be put into perspective.

A monitor with a very low deviation in color, a pro screen (and very very expensive), will have a variation of 10 to 15 % between the brightest and darkest point. A classic screen can go as high as 30% without this usually causing a problem.

Therefore, these two screens are above average.

The Dell gave us a 22% max difference with an average 4.6% variation per measurement point.

PVA 6 ms : Dell 2408WFP


The Iolair has a 21% maximum with an average variation of 3.5 %.

MVA 6 ms : Iolair MB24W


One word of caution on the Iolair: the MB24W (actually available under numerous brands varying depending on the country) is based on an older generation MVA panel that is supposed to no longer be produced. So expect stronger variations in its behavior than with monitors equipped with more recent components. In particular, this concerns the Mura effect and therefore homogeneity.


Page 4
Games : reactivity, input lag

Games: reactivity, input lag
Itís something weíve never done before: for once we will quickly go over the reactivity of these two screens (in fact, itís excellent and much better than what announced response times suggest) so that we can spend more time on a more negative characteristic of the Dell, its input lag.

After having tried a few response time measurement methods with an oscilloscope that often gave contradictory results with our visual impressions in games, since 2005 we have opted for a more concrete test using screen shots of afterglow with a reflex in burst mode.


Hereís the concept in this test: A car moves from right to left at high speed. The movement isnít perfectly fluid and depending on its speed, the car is shown in several successive positions. When this process is sped up, the car goes very fast, positions are very close and the eye perceives a fluid movement.

The perfect screen
A screen with two afterglow images

A monitor without ghosting effects would have previous images completely fading away when a new one appears. This is ideal, however in practice, it's often not the case as images progressively fade. Sometimes up to 5 afterglow artifacts remain on the screen representing the visible white trail behind objects.

We capture this LCD defect with a camera at a shutter speed of 1/1000 s by taking 50 pictures per test. We then can see a monitorís ghosting effects, or the carís position in the entire process from the moment when afterglow is at its maximum, up until when the next image is about to be created and the previous image is the least visible.

Here are the two extreme states between which each monitorís afterglow can oscillate.


PVA 6 ms : Dell 2408WFP


MVA 6 ms : Iolair MB24W

The above test already gives us a good idea of ghosting effects on the two screens. We can go into even more detail by looking at the frequency of minimum and maximum states of afterglow.

In dark blue : the average number of colored afterglow images (the most bothersome type).
In light blue : transparent afterglow images which in practice are barely noticeable.

PVA 6 ms : Dell 2408WFP



MVA 6 ms : Iolair MB24W

What do these figures imply ?
1 : More or less that differences are so small that they are imperceptible and the two monitors are equivalent. Moreover, this is consistent with our visual evaluation.
2 : Also that they have the same behavior as the fastest 24 inch TNs equipped with panels that have a given response time of 2 ms. In reality, the MB24W and 2408WFP are much more reactive than 5 ms TNs.

So does this make them gaming monitors? The input lag test is the other determining factor.
Input lag in games
If you didnít already know, almost all LCD monitors have a small delay in display. To measure this, we photograph a chronometer which is precise to 1/1000th of a second displayed in clone mode on our reference CRT and the LCD we are testing. We take 12 consecutive differences, eliminating the two extremes and then find the average delay.

For this test, we deactivate graphic card / screen synchronization to capture a more precise result instead a value that is rounded to the nearest image. For this reason, the resulting measurements are not dependent upon the fps value. An LCD functions at 60 Hz (even those that claim 75 Hz) and so 17 ms equals an average delay of a single image. In the same way, 33 ms equals 2 images. This may not seem like much, however, to lan gamer it could make a world of difference. For example, an adversary with an LCD or CRT will see his character two images before him. This can be compounded by the fact that the mouse can add another 1 to 8 ms (except very poor ones), and the graphic card adds a half image delay (at best and actually this can be 5 to 50 ms). More specifically in our research, we found that this can be a cumulative delay of 110 ms or 6.5 images. In this case, it is indeed noticeable and even bothersome for some gamers. For more details on this subject, see our article, LCD images delayed compared to those of CRTs ? Yes ! .


PVA 6 ms : Dell 2408WFP



MVA 6 ms : Iolair MB24W

No, results are indeed correct and we have two screens with diametrically opposed behaviors. On the one side is the Dell with an average delay of 4.1 images, and on the other, the Iolair with zero input lag Ė even having the luxury of occasionally being slightly ahead of the CRT.

As you can see on the Dell, the worst is that the delay varies from 60 (3.6 images) to 89 ms (5.3 images) once we discard the two extremes values. If we include the minimum, nothing changes. On the other hand, if we add the maximum, the 2408WFP is 10 images behind!

Even with Ďíonlyíí 4 images, the difference is perceptible in games and movies because you can hear sound before the image. More concretely in games, this translates into:



The two screens are in clone mode; however, with the Dell the game has just started while on the CRT we can see the character has started to advance with an enemy appearing in front of him. If the two screens were used by opposing players, guess who would win? Even in games versus the computer, on such a monitor we start out with a handicap.

This result was verified on the two 2408WFPs we tested as well as with several American colleagues that use our test methods.


Page 5
Viewing angles, movies

Viewing angles
We take pictures of the monitors from a 50į angle from all sides. The claimed viewing angles in a productís characteristics are often exaggerated especially for TN screens.

There are three types of technologies to choose from: TN, MVA and PVA, the last two being closely related. We could also add ASV Ė a variation of MVA from Sharp, in decline which we really only find in TVs.

First of all , lateral viewing angles with IPS technology are by far the best. Next usually come monitors with TN panels. In the past (more than 2 years ago), TNs were rather catastrophic from the side angles. Now, it is possible for several people to share a screen, even if they arenít perfectly in front of it. Finally, we have the PVAs and MVAs, which are more or less equivalent. Beyond 40į from both sides, there is a loss of contrast, which however isnít too extreme. In fact, there are only really problems when looking from below.

Vertical viewing angles : The IPS screen always offers an image that is almost perfect at 50į and even beyond. In this area, other technologies are largely inferior. The PVAs are behind with a rather abrupt loss of contrast with an image that is still visible though not as flattering (black is more gray, white is pale, loss of depth). Itís the same but even more sudden with MVA panels. Finally, we have the TN screen. From above, the image loses all of its contrast. From below, it turns black. This complicates things when you want to use this screen as a TV and depending on the size of viewers, the monitor may have to be inclined.

PVA 6 ms : Dell 2408WFP


MVA 6 ms : Iolair MB24W


And for comparison :


TN 2 ms : Iiyama ProLite E2201W


IPS 8 ms : Dell 3008WFP
Movie rendering

At this time, we havenít yet tested a single monitor equipped with a video correction chip worthy of this name. We still have to rely on the graphic card, which has made small improvements in this domain but far from the smoothing and upscaling capabilities of the best televisions. Here, all compression defects are readily visible and watching a DivX requires some patience!

Otherwise, this test opposes a

  • PVA screen : appreciated for its viewing angles that are a bit larger than those of an MVA and for its deeper black. On the other hand, PVA panels Ė and itís no exception here Ė are particularly subject to shimmering. Moreover, as weíve seen this model has a very handicapping input lag. A movie encoded in 25 images / second = 1 image every 1/25 = 40 ms. On average, with 70 ms of delay on the two screens tested here, sequences are displayed two images after the accompanying sound. Itís something occasionally sought after in movies to accentuate a surprise effect. Crack ! And Freddie jumps out of the closet... You will more or less consciously experience the entire sequence a little in advance by hearing it first. And itís true that in movies, itís less bothersome than in games and only the most sensitive will be occasionally affected. This is all the more true because the attention we give movies is less than what we give to an FPS.

    Finally, on our test screen we can unfortunately confirm that shimmering and denatured colors (as long as there has been no calibration with a sensor) are indeed present.

  • an MVA screen with blacks that are slightly washed out and viewing angles that are a bit smaller. (There is no dead angle but we do lose contrast more quickly than with a PVA when moving from the central axis). On the other hand, shimmering is much better controlled here.


  • Page 6
    Energy consumption and heat

    Energy consumption
    Consumption is measured with the display of a standard photo :

  • 200 cd/m≤ : if you have a versatile use of your screen, this is a good setting that is comfortable for games and work.

  • 100 cd/m≤ : if you are a graphic designer or you work at night, this setting is both easier on the eyes, and closer to paper rendering and a CRT.

    PVA 6 ms : Dell 2408WFP


    MVA 6 ms : Iolair MB24W

    The two monitors are big energy users. A screen like the Iiyama B2403BW, also a 24 inch, consumes around 40 watts at 200 cd/m≤.
    Monitor temperature

    With such high energy use, we might fear an excessive production of heat. In the end, this doesnít turn out to be problem. Both screens are above the average but are still within reason. They give off roughly 40į and there is no particular danger of burning oneself or especially damaging the cells on the panel. It becomes a problem above 50į, and higher than 55į it is best to switch it off.

    As a reference, a "cold" screen gives off around 30į (a measurement taken at a moderate room temperature of 19į in our office).


  • Page 7
    Dell 2408WFP

    Dell 2408WFP

    The 2408WFP replaces the 2407WFP-HC. It has lost the suffix but not the associated function and itís still a wide gamut. However, this year it has been particularly a problem as neither Samsung, the panel manufacturer, nor Dell, had the characteristic in mind with regard to the screenís color tables. For this reason, tones are over-saturated, almost fluorescent. Manually, we found a correct setting, which was better, but not that great. Without a calibration sensor, finding correct colors on such a screen becomes a real challenge.

    The change from the 2407WFP-HC to the 2408WFP was extremely fast, something unusual for Dell. Why? There could be some relation to a certain polemic which (already) surrounded the poor quality of PVA panels. Numerous users reported having found a severe reverse ghosting (black afterglow) on their monitors. During tests we were aware of this and looked for the phenomenon on the test monitor but didnít find anything. Neither did we find it on a 2407WFP-HC which one of our readers brought by to our labs. (He even admitted not seeing this defect although he carefully scrutinized his screen). This doesnít mean that the black ghosting is inexistent as the considerable amount of testimony on the net, our forum and even Dellís website attests. Dell is aware of the situation and confirmed its existence on its forum via one of its technicians. So itís not too surprising that the 2407WFP-HC was quickly replaced even by another screen that according to characteristics appears to be a clone.

    However, one detail did actually change; the addition of a new DisplayPort interface. This input is supposed to replace DVI in a few years (the more optimistic say two years). It highly resembles an HDMI including its characteristics that the two may be confused. They both conduct the image and sound which is practical for those that own a monitor with integrated speakers. The advantage of the Display Port, which justifies its adoption, is that itís not limited. HDMI, in the photo on the right, does not go beyond 1920 x 1200 pixels while Display Port climbs into higher resolutions. Whatís the interest on a 24 inch? None and all the more so that the first DisplayPort cards wonít be released before May 2008.

    At the current time, we havenít heard anything about the above mentioned defect on the 2408 nor did we detect any such problem in our monitors. On the other hand, if there was some small improvement here, this is accompanied by so much other deterioration in other areas that we have to give this screen a red card. Between its totally unsuited color settings, excessive input lag which is apt to turn away gamers and movie fans and double the average energy use, the 2408WFP leaves us perplexed. How could such a screen have been launched on the market and especially for this price? In the beginning we hoped problems were just related to defects on the first unit we received but the second was identical. In addition, various tests then appeared in the U.S. (itís true, largely inspired from our test procedure) reporting similar results. They also reported significant input lag, color defects, etc.

    So werenít these Dell screens verified at the end of the production line? At this price level, itís incomprehensible even if the look and ergonomics are still as exemplary.


    Page 8
    Iolair MB24W

    Iolair MB24W

    Remember less the company and more the name of the product as the MB24W can actually be found under roughly twenty other different brands. Itís indeed the same each time except for the interfaces. So be careful as there are VGA-only versions and VGA + DVI as well. You might as well opt for the second and the one we tested here which is HDCP compatible on its DVI. At this price level, itís quite a nice surprise.


    Briefly, the MB24W:
    - has an MVA panel that produces washed out blacks,
    - viewing angles that are smaller than those on a PVA but larger than vertical ones with TNs,
    - excellent reactivity, comparable to the best 2 ms TNs,
    - good rendering in movies thanks to well controlled shimmering (comparable to the best TN panels but not better),
    - isnít too environmentally friendly : it consumes almost double the average,
    - is equipped with an older generation panel; verify for potential Mura and dead pixel defects (even if our test monitor was perfect in these two areas)
    - has average color presettings but are easily improved,
    - basic ergonomics and finishing touches: crude plastic, thick bezel, no vertical adjustability or rotating base.
    - in the end has an extremely interesting quality/price ratio for those who want to game on a big screen, work or even touch up images without spending too much.




    Page 9
    Conclusion

    Conclusion
    For the lazier readers that skipped over the previous pages :

    The Dell 2408WFP : not good! Except for office use, its look, ergonomics, finishing touches and materials. In short, itís (still) as superb but totally failed our gaming tests.

    The Iolair MB24W (and all MB24Ws sold under various brands, preferably with DVI) : good. Itís a very nice surprise and rather unexpected to find an MVA panel for this price with such reactivity and more or less good colors as they were easy to correct (at least in our case and letís hope you get the same panel series). Either way, note that the MB24W is theoretically an MVA screen. In France, we received the assurance that it only exists in this technology. On the other hand, in England we can also find the occasional TN under this name. You will have to make a case by case verification. If the announced viewing angles are 178 or 180į, then itís an MVA. If they are only 160 or 170į, it's a TN and itís significantly less attractive. The monitor will be less reactive and the lower viewing angle quickly darkens like on all TNs.

    So in the end, is the Iolair a good alternative to the Iiyama B2403BS and its white clone, the Belinea o.display 24 4.1? And does MVA technology " trample" over TN as we can sometimes read on forums ?


    Yes, you can opt for the Iolair if you are looking for a reactive large screen for the best possible price. Also, if you are allergic to the fact that TNs are subject to a lower viewing angle that darkens.

    Nevertheless, Iiyama and Belinea screens hold several non-negligible advantages and have our preference overall. First of all, construction is an entirely different affair as the plastic used is of much higher quality and assembly is more precise and better fitted. The base is superior and, for example, itís vertically adjustable and pivots. Next, they produce a much deeper black. And finally, they consume half the energy.


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