Brightness homogeneity

Brightness homogeneity

LED backlighting is made of a multitude of diodes. In addition to the wide gamut, they can also provide better panel homogeneity to avoid dark or over-lighted areas.

The XL20’s result is a bit disappointing at first. The gaps are moderate – less than 8% form one corner to the other – but not reduced to zero. This result is nevertheless:

-comparable to those measured with the Nec LED, the LCD2180WG, which also features LED backlighting but is much more expensive than the LCD2180WG.

- better than LCD monitors with standard CCFL backlights. Differences can attain up to 50% and more commonly 25% between two areas.

We confirmed in a previous article that CRTs were also subject to this problem. The Mitsubishi Diamondtron 930SB shows variations of up to 15%.

Reaction time

Reaction time

A car moves from left to right at high speed.

Movement isn’t perfectly fluid. Depending on its speed, the car is shown in several successive positions. If the car goes very fast, the positions are very close and the eye perceives a flowing movement.

perfect monitor monitor with two afterglow images
A monitor without ghosting effects would have previous images completely fading away when a new one appears. This is the theory and in practice, it's often not the case as images progressively fade. Sometimes up to 5 afterglow images remain on the monitor and represent the visible white trail behind objects. Some monitors have strong overdrives in addition to image anticipation algorithms. In this case, an image can appear in front of the main object, creating a white halo ahead of objects in motion.

We capture afterglow with a camera at a shutter speed of 1/1000 s for an LCD. We take 50 pictures per test. We then can see a monitor’s ghosting effects, or all the car’s position in the entire process. The most important image is the one on the left, the better one. It will be the most displayed on the monitor, while the one on the right is in transition.

Here are the two extreme states with each monitor as afterglow oscillates.

A-MVA 8 ms : Samsung SyncMaster XL20

This is a typical result of MVA 8ms monitors. Here, this MVA is qualified as A, for Advanced. From our point of view, we don’t see the difference compared to P-MVAs (P for Premium) in games, unless you really scrutinize the scene over and over. In this case, the A-MVA (Samsung XL20) looks a bit faster. This is shown in the “best” picture, in which the ghost trail is completely white instead of showing a bit of color like the ViewSonic VX2025wm below. For common use, however, even a very demanding user will not see the difference between two versions of MVA panels.

Comparison with competing monitors:
P-MVA 8ms : ViewSonic VX2025wm

PVA 8 ms : Samsung SyncMaster 215TW

IPS 6 ms : Nec MultiSync 20WGX²

TN 5 ms : Samsung SyncMaster 204B

IPS 16 ms : Nec MultiSync LCD2090UXi
Our conclusions are unchanged. TN 2, 3, 4 and IPS 6ms like the Nec 20WGX² are the fastest for games. This isn’t perfect (our expectations for 100 and 120 Hz monitors are great) but this is the closest to CRTs for now.

Then comes the MVA, A-MVA and P-MVA which are noticeably faster than the PVA 6/8 ms and TN 5/8/12/16 ms.

Viewing angles and movies

Viewing angles

We take pictures of monitors on the side with a 50° angle. Announced viewing angles in characteristics are often over exaggerated. As for the XL20, its angles are quite good. This is less impressive than with IPS monitors (they have been the reference for years) but it is better than P-MVAs. We do not have the technical documentation to explain the differences (probably minor) but here is one of the keys that justified the name modification of these panels:
A-MVA 8ms : Samsung SyncMaster XL20

P-MVA 8ms : Belinea 10 20 30W

IPS 16 ms : Dell 2007WFP

TN 6 ms : Samsung SyncMaster 204B

PVA 8 ms : Samsung SyncMaster 215TW

P-MVA 8ms : ViewSonic VX2025wm
The XL20 obviously has wider viewing angles compared to P-MVA monitors (Belinea and ViewSonic). It competes with the Dell (IPS panel) which remains the best for in this test. The reductions for the Samsung are quite low but are nevertheless there. This is particularly true from the sides (horizontal angles).

Movies

It is best this time to leave the Adobe RVB and come back to sRGB. The best is even manual adjustments. If you don’t, you will be annoyed by the washed out black strips above and below the film. When choosing the sRGB, this problem is less noticeable.


For twinkling, we didn’t notice any improvements compared to P-MVA panels. A-MVAs aren’t better but neither are they worse. Twinkling is visible for someone looking for it from a distance inferior to 2 meters. It is, however, more discreet than with TN, PVA and IPS panels.
To reduce it, move to the graphic card
level. We recently published an article about NVIDIA and ATI drivers which now have quite efficient correction functions. For now, we prefer NVIDIA’s solution which gives the possibility to manually and more efficiently adjust the correction.

We do find it unfortunate however, that Samsung didn’t announce the DVI input as being HDCP compatible. There is a possibility that it might not be capable of displaying HD movies and games protected by the HDCP encoding norm.

Conclusion

Conclusion

The XL20 is the future of LCD monitors. We particularly appreciated its really wide gamut, the possibility to easily switch from one color profile to another and the new viewing angles (finally!!!). Whether it’s for movies or dual monitor configurations, it is really a great improvement.

The only thing is, we don’t know the price. In principle it should be moderate. We have heard somewhere around 1400 euros, but this hasn’t been officially confirmed. Of course, this would be much more expensive than current 20” monitors - priced around €350. This has also to be compared to the only other LED monitor on the market, the NEC with the same diagonal, same gamut, but priced at 5000€ (!). Also, this is the first LCD of this type to target the general public. We believe that little by little, this technology will be present in more affordable monitors.

Another detail to settle in the future is the design. LED backlights really increase thickness. In consequence, because of the unattractive design and lack of progress in reaction time, not everyone will go for this technology.

What improvements in 2007 ?

This year will be a good year for monitors. We first expect many HDMI monitors with HDCP compatibility to display protected digital content (consoles and movies).

We also expect the first 1ms monitors, but we are skeptical about the real improvements induced by this reduction in time. Our hopes are on the future 100 and 120 Hz monitors as we have seen in the TV world.

Canon persists on announcing the release of the first SED monitors by the end of the year in Japan and in the US. At first, this technology will be restricted to TVs. This is something that we won’t test at first except if we see a real convergence between the world of the office and living room (which is likely to happen). There are now some very good TVs that can be used very effectively as monitors!

OLED: does it really exist? We haven’t heard from this technology for a long time. Samsung pretends to have forgotten about it and Sony announced stopping its production of monitors (and all technologies are concerned). Will they ever succeed one day in releasing an OLED?