Color rendering

Color rendering

As usual with the help of our probe we measured the difference between ideal colors and the ones actually displayed on the screen giving us a value called average DeltaE 94. We understand this data from our experience in this domain, however, this isn’t the case for everyone. We therefore are putting into place a new notation system based on our measurements, and which will immediately give you a better notion of quality in this area. Currently, there are no standards for color fidelity and manufacturers can pretty much say and do what they like (see the saga of the Samsung 226BW...). This system will only be for our website but at least it will be a step in the right direction.

By taking the differences between the measured colors and actual gamut found on the screen, a grade from A+ to F- will be given (and less if necessary). Of course, the higher up in the alphabet, the better the color fidelity. An A+ monitor will necessarily be factory pre-calibrated with an average DeltaE of less than 2 and with an extended gamut. Applied to current 24 inch products, this result in the following:


Two screens come out with flying colors (excuse the pun), the Dell 2407WFP (we tested the 4th version and it recently went to v5) and the new Iiyama. There is some disappointment concerning the 245T as Samsung equipped its screen with a wide gamut panel but did not pre-calibrate it. In our opinion, it cannot be used to its full potential if you do not have a calibration tool and manually adjustments produce results that aren’t much better. However, even with proper calibration it’s not perfect because after our color correction reds still weren’t natural.

The table above will not replace the usual detailed explanations. For those who are interested, here is the normal analysis of results. (Please note this time that the panel homogeneity section is found on the page devoted to each screen.)

The quality of colors is measured with the LaCie BlueEye Pro colorimeter, which in fact, is a Gretag colorimeter coupled to the software suite developed by LaCie.

Just to remind you, we work with a value called DeltaE. It represents a measurement between the color requested and the one really displayed on the monitor. The higher the result obtained, the less true colors are. 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 wouldn’t be content
- 1 < Delta E < 2 : colors are accurate.
- Delta E < 1 : the result is perfect.

DeltaE by default


You may have noticed that results are consistent with the grades above, and you can see that "A"s were given to screens with a starting average dE less than 2.5.

Besides color rendering, there is a point that concerns more and more people, depth of black. We measured a constant brightness of 200 cd/m² in white, and here we have a result that we aren’t used to seeing:

Depth of black (cd/m²) with a white of 200 cd/m²

The screen with the deepest black, the Samsung 245B, is not equipped with a PVA panel – historically the best technology in this area – but a TN. Next is the ViewSonic, with an MVA panel. Nevertheless, overall results are very good and most monitors are under the 0.30 cd/m² mark. These figures give us the following contrast ratios:

Contrast ratios measured with a 200 cd/m² in white (xxx:1)

So unfortunately, there is a bit of disappointment regarding the 245T. It’s the least gifted in default color fidelity and one of the weakest in contrast due to a lighter black than the others (note: this measurement was taken with the MPA function deactivated). It wouldn’t be fair, however, to harp on this too much as a contrast ratio of 700:1 is already very good. It’s just too bad to see an entry level TN, in particular, do much better, and this is the nice surprise of this article, the Iiyama does very well here. The quality of its factory pre-calibration is totally unexpected and very appreciable.

Each time, we analyze 18 color patches and 16 of these results are given in the following graphs:

TN 3 ms : Iiyama Prolite B2403WS

PVA 6 ms : Samsung SyncMaster 245T

PVA 6 ms : Acer AL2416W

PVA 6 ms : Dell 2407WFP rev.4

MVA 8 ms : LG L245WP-BN

TN 5 ms : Samsung SyncMaster 245B

MVA 8 ms : ViewSonic VX2435wm

The Samsung 245T after calibration


PVA 6 ms : Samsung SyncMaster 245T
After calibration with our LaCie colorimeter, the situation improves but it still isn’t perfect. The wide gamut is preserved, but there is a problem in the extreme shades which this graph doesn’t show. They are too vivid, almost fluorescent especially in reds. We get the impression that the 245T imposes an upscaling of sRGB photos in NTSC or that it extends the starting color space, even if the original photo comes from an sRGB source. This only becomes a problem on certain shades, but it does make rendering slightly off before printing and certain colors are different than what is put on paper.

Nevertheless, going under the calibration sensor is more than beneficial and is even a necessity. Colors are much better and even quite nice. However, plan on taking a few hours or even a week to get used to a new richness of colors which weren’t available on the majority of previous LCDs and on no CRT. Note that the Samsung SyncMaster 226CW, a 22 inch with a TN wide gamut panel that has simultaneously been released, also has problems with its default colors. Here again the colorimeter is able to make proper adjustments, notably in reds. One last point in this area is that strong reds aren’t necessarily a definitive characteristic of wide gamut screens and this is more isolated to the 245T that we received.

Gray rendering and gamut

Concretely: grey rendering

Unless you are an expert in monitors (and even then) it is difficult to imagine what these differences can represent. What is the most bothersome, however, is when we can see color dominances on the screen. These can affect all colors and are particularly noticeable in grays where the eye can quickly see when the image is stronger in blues or reds.

Here are the screen’s grays and reproduced as measured by our sensor. For comparison on the bottom line are the ideal grays.

TN 3 ms : Iiyama Prolite B2403WS

PVA 6 ms : Samsung SyncMaster 245T

PVA 6 ms : Acer AL2416W

PVA 6 ms : Dell 2407WFP rev.4

MVA 8 ms : LG L245WP-BN

TN 5 ms : Samsung SyncMaster 245B

MVA 8 ms : ViewSonic VX2435wm
If the screen you are currently using is calibrated or not, you should be able to see the differences between the two lines.

To answer a reoccurring question: to calibrate a screen, is it always necessary to use acalibration probe. Modifying parameters in the OSD is a simple adjustment and often not enough, because differences vary from one color to the next. If we have too much blue in lighter shades, we can have too much red in darker ones, or vice versa. So, when we decrease the amount of red this affects all colors, whether they have too much or not. We are only changing color balances and putting dominances somewhere else. On the other hand, hardware calibration rewrites the entire color table that is used by the graphic card. It’s better but is more expensive. A good probe will cost 300 Euros and for this reason, we largely prefer when screens are factory pre-calibrated.

Gamut : all in sRGB, except the 245T

The 245T undeniably goes further than others and for this reason parts of its rendering surprised us at first. The graph gives us an idea of this result, but doesn’t really tell us the specific characteristics. In particular, it doesn’t show us the differences in the reds and minimizes the improvement in blues. In short, it’s a good reference but not ideal.

Note that the gamut doesn’t change after calibration. The sensor makes corrections but without reducing the color space, an appreciable point. Still, if your colorimeter is a little old, request an update from the manufacturer. Older software suites don’t necessarily manage the wide gamut, which could mean a reduction in the color space to sRGB after calibration.

Reactivity tests

Reactivity tests

Here’s the concept in this test: A car moves from right to left at high speed. The movement isn’t 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.

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 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 monitor’s ghosting effects, or the car’s 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 monitor’s afterglow can oscillate.

TN 3 ms : Iiyama Prolite B2403WS, standard settings (OD at 5 or 0)
TN 3 ms : Iiyama Prolite B2403WS, with OD at 2
PVA 6 ms : Samsung SyncMaster 245T
In the beginning of this test, the Iiyama is disappointing and it isn’t better than a TN 8 ms. However, in looking through the OSD we find an OD (overdrive) adjustment in the « Miscellaneous » menu where there are six levels, from 0 to 5. Normally, we would pick 0 or 5 to activate or deactivate the function and this is what we actually did to start with. However, in trying out the number 2 setting we found it to be the best of all and the change is significant.

The 245T is better than the unadjusted Iiyama and is slower after we reset the overdrive levels–even if it’s not obvious in the photos above. The reason is that the B2403WS is almost always in the « best state » of afterglow, or in other words, it's never in its worst state while for the 245T the two states are found equally. Nevertheless, ghosting effects aren’t a real problem here and gaming is entirely possible. TN 2 and 3 ms screens are even better in this domain. So why were we disappointed? Because it's an MPA screen, a technology that should reduce retinal persistence and therefore afterglow. In this way, it fails for us. There is more information on this subject in the page devoted to the 245T, but in short, its activation doesn’t reduce this defect. Moreover, it even affects brightness homogeneity to the detriment of color quality.

Here is the reactivity of other competing screens:

S-PVA 6 ms : Acer AL2416W
S-PVA 6 ms : Dell 2407WFP
P-MVA 8 ms : LG L245WP-BN
TN 5 ms : Samsung SyncMaster 245B
P-MVA 8 ms : ViewSonic VX2435wm
TN 2 ms : Samsung SyncMaster 226BW series S

Viewing angles and movies

Viewing angles

We take pictures of the monitors from a 50° angle from all sides. The claimed viewing angles in a product’s characteristics are often exaggerated.

There are three types of technology to choose from: TN, MVA and PVA, the last two being closely related. For comparison, we added an IPS, the Dell 3007WFP HC. If you are a regular reader of our LCD surveys, you won’t be surprised by results, which are entirely normal.

First of all, for lateral viewing angles the IPS is by far the best. If this is the most important criteria for you, this is the type of technology you need. In second place comes the 245B, a TN panel. In the past (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 aren’t perfectly in front of it. Finally, we have the PVAs and MVAs, which are equal. Beyond 40° from both sides, there is a loss of contrast, which however isn’t too extreme. In fact, there are only really problems in the vertical plane.

Vertical viewing angles : The IPS screen always offers an image that is almost perfect at 50° 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). It’s 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.



TN 3 ms : Iiyama Prolite B2403WS
PVA 6 ms : Samsung SyncMaster 245T

PVA 6 ms : Acer AL2416W

PVA 6 ms : Dell 2407WFP rev.4

MVA 8 ms : LG L245WP-BN

TN 5 ms : Samsung SyncMaster 245B

MVA 8 ms : ViewSonic VX2435wm

IPS 6 ms : Dell 3007WFP HC
Something to note so as not to penalize the LG L245-BN in evaluating its test results is the fact that it is equipped with a panel that is slightly glossy. This isn’t comparable to some laptops, however, care should be taken to block out ambient lighting so that they won’t be seen on the screen or reduce visibility.

Rendering in movies

Ideally these Full HD 24 inch screens should display movies perfectly. Unfortunately, they aren’t TVs and for this reason the manufacturers didn’t integrate image correction circuits that mask MPEG compression, smooth out objects, and which upscale non Full HD sequences. The image is shown as it is received, compressed, with color defects and aliasing.

The 245T does slightly better than the others due to its wide gamut. Color fidelity is superior and less affected by solarization, which is typically seen in sunsets. On this screen, all shades and the color gradient are better reproduced. On the other hand, this doesn’t improve compression or shimmering, which is still very noticeable on this monitor.

The Iiyama has neither a wide gamut nor correction circuits. The result is that there is solarization in complex scenes and video noise in large uniform color areas.

Whatever the monitor, to more enjoy your movies regardless of the encoding format, step back!

In the absence of correction circuits, there is however a solution, at least if you are equipped with a recent ATI or NVIDIA graphic card. Their drivers emulate this correction with more or less success as we discussed in our article ATI and NVIDIA correct the twinkling effect of LCDs in movies .

Iiyama Prolite B2403WS

Iiyama Prolite B2403WS

In the beginning we liked the Prolite B2403WS in all domains except one, reactivity because of its afterglow. The manufacturer leaves us with very poor standard settings, and we had to look to find a way to really take advantage of the 3 ms response time. Indeed, this monitor’s reactivity was the worst of all 24 inch screens and comparable to that of a TN 8 ms. However, by going in the OSD in the « Miscellaneous » page, you can activate the different OD (OverDrive) levels. Instead of 0 or 5, choose level 2 and watch the miracle as afterglow diminishes considerably.

In the end, this Iiyama Prolite B2403WS was a real favorite in our office. It combines the main essential ingrediants of a good screen with excellent reactivity (after adjustment), pre-calibratedd colors (!!!), a reasonable price (this is relative of course but exactly a year ago the Dell 2407WFP was launched at 1150), nice design, rotating base, vertically adjustable and can be pivoted.

Here it is from all angles:




Aesthetically, if we have one criticism, it’s the base which looks too classic. After this, we would have preferred a metal finish instead of plastic, but at this price…

The screen is inexpensive, however, there are rumours that the 24 inch competition will offer something at around 399 euros (tax included) without any precise model mentioned. And of course, for those looking for bigger screens at lower prices, waiting this out could be a tempting option. However, for a 100 euros less, we can’t expect such ergonomics nor the pre-calibrated colors of this Prolite B2403WS.

Color homogeneity

The maximum difference in brightness between two points was 22 %. This is a better than average (usually around 30%) but not as good as the Samsung 245T, which is more in the high end. So overall, it’s a good result.

Note that is rare to be able to visually detect this difference.

Samsung SyncMaster 245T

Samsung SyncMaster 245T

There are three main marketing points for the 245T:
- very good connectivity (with HDMI),
- a wide gamut,
- the MPA function, which is supposed to reduce afterglow due to retinal persistence.

For the first point, there is little disappointment and the screen is definitely well equipped in this domain.

As for the wide gamut, it would have been more effective if this screen was factory pre-calibrated, which the evidence suggests Samsung neglected to do. Or at least this is true for the first version, which was lent to us for this test.

The MPA function : the principle and its efficiency

Finally, we have the MPA function. Deactivated, we have a normal screen with a « static » image. By pressing a button on the front of the monitor, this « artificial sweeping » is activated. Homogeneity is slightly affected and even noticeably so. Here is a series of burst photos taken at 1/400 of a second with the MPA function activated:


On these images, we can make out four CCFL tubes (commonly called neons) which serve as backlighting, and that shut down one by one to simulate the sweeping associated with this technology. The black band is supposed to clean our eyes of the persistent bright traces emitted by the N-1 image. We have already come across this system twice with BenQ on its FP241W Z and then the FP241VW. The former is equipped with 16 tubes, the latter only has 8. Samsung cut this in half again and was in error to do so. With 16 and 8 tubes, there is a noticeable defect in the form of a twinkling, which in the end is typical of screens with 60 Hz tubes. To this we can add the loss of color homogeneity and contrast due to the large size of the bands – at least compared to those of a CRT.

With its four tubes, the 245T suffers from the same homogeneity and twinkling problems.
Where Samsung does better : The loss of contrast is negligible.
Where this Samsung does less well : On the applications we tested, there was no noticeable gain in comfort and the afterglow is always the same. In short, it doesn’t bring any improvement and even degrades the image. We strongly recommend that you forget this function and deactivate it whatever your activity; movies, games, web surfing. Try it out, you never know, but in our opinion, there was no interest.

This leaves us with the rest ; the gamut, ergonomics and color homogeneity of this screen.

Gamut, photo and movie rendering

As you may have noticed in the previous pages, the 245T’s gamut is indeed one of the widest on the market and theoretically it is one of the rare screens to be able of displaying all colors that were captured by a reflex which uses the Adobe RGB color space. Unfortunately, the 245T isn’t calibrated and our colorimeter, which however is one of the best in our opinion (newest version of the LaCie Blue Eye Pro, could not correct all colors. Even after calibration, red was a problem with rendering that was almost fluorescent. Let’s just hope that other such tools do better, which is entirely possible.

An extended gamut on TVs theoretically adds a second advantage of better rendering in movies. This means no more uniform color areas (where there should be many shades) and solarization and twinkling are also reduced. Here again, the 245T leaves something to be desired. Color fidelity is much better, but the twinkling and MPEG defects are still easily noticeable. And actually this is no surprise because the 245T is first and foremost a computer screen. Samsung doesn’t integrate the video correction circuits which are found in its LCD and plasma TVs. This is too bad because the 245T will not be the first screen to be perfectly versatile.

Ergonomics in images

Color homogeneity

With all the results in, we have a 15% maximum difference between two corners of the panel and an average of 4.6 % between two points. This, with those of the Dell 2707WFP, is one of the best results and good news for graphic artists.

For comparison, screens usually have 30% differences between points and more between corners.

Conclusion

Conclusion

So are we going to see an invasion of 24"s like what we saw recently with the 22"? Manufacturers are very skeptical, however, we think that this diagonal size is going to rapidly replace the 22" for advanced users. The only limitation will come in terms of graphics, because for the latest games in 1920x1200, a GeForce 8800 GTS 640 MB, or even an 8800 GTX, won’t be too much. For other uses, an entry level card will be sufficient.

The stocks of 24"s which were ordered are proof of manufacturer’s skepticism towards this diagonal size. We, however, wouldn’t be surprised if there were shortages for the products with the best quality/price ratio at year’s end – exactly as was the case for a period of six months with the 22 inch. In other words, it wouldn’t be too surprising to see the Iiyama screen in short supply.

Launched at a recommended price of 499 euros, it combines almost everything needed for a versatile screen except very large viewing angles. Otherwise, in terms of ergonomics, reactivity, default colors, price and design, it was well conceived. Currently, it is the least expensive on the market, however, soon other screens could go even lower with the possibility of a 24 inch for 399 euros between now and Christmas. Just don’t expect calibrated rendering or such ergonomics as the B2403WS’.

The Samsung 245T should please professional photographers on the condition that they have a good calibrator and the eye to fine tune parameters. It’s just too bad that Samsung didn’t pre-calibrate its monitor and that the MPA function is so inefficient.

And what about Dell? The 2407WFP is only around for a few more weeks and already in some countries Dell has presented its successor, the 2407WFP HC. More specifically, this is the same screen but with an extended gamut. In the US, for example, it is offered (on sale as we speak) for 569 dollars (without tax) or 411 euros (without tax or 492 euros taxes included). If you are starting to believe in miracles, go to Dell.fr for a dose of reality. There we can see that the current 2407WFP, or its previous version, is at 981 euros taxes included and not on sale. When feeling generous, Dell will sometimes lower this price to around 730 euros but either way we are far from its US strategy.