LCD Panels with Response Time Compensation: 7 Monitors Reviewed

The ISO 13406-2 method to measure the monitor’s response time as the total time necessary to change the state of a pixel from pure black to pure white and back again brings but very little information about the real performance of the monitor and easily misleads the user. Today we are going to reveal all secrets about this parameter and discuss the response time compensation that affects the quality of dynamic images on the screen of 7 monitors from ViewSonic and Samsung.

by Oleg Artamonov
12/20/2005 | 08:32 AM

In my earlier articles (first of all in the article called X-bit’s Guide: Contemporary LCD Monitor Parameters and Characteristics , which was wholly concerned with the strong and weak aspects of LCD monitors as well as with the accepted methods of measuring their parameters) I have repeatedly stated that the ISO 13406-2 method to measure the monitor’s response time as the total time necessary to change the state of a pixel from pure black to pure white and back again brings but very little information about the real performance of the monitor and easily misleads the user.

 

The problem is that the response time value obtained by this method is not the maximum and even not an average, but the minimal speed the monitor can have. In practice, however, the user never deals with a pure white color even when working with black text on white background unless the monitor’s contrast setting is set at the maximum, which would be too bright and uncomfortable for normal work. However, it is only the maximum possible screen brightness that is regarded by the matrix as pure white, so it is going to treat the white background as gray rather than white. Moreover, the user never sees a pure black color in games or movies, either. In other words, we usually either deal with black into light-gray (when working with text, for example) or gray-to-gray transitions and the formally measured response time of the matrix thus has a very small practical value.

As a side remark, I’d want to make it clear that when I say “gray” in the context of LCD monitors I don’t mean the gray color the user sees on the screen, but any in-between state of any sub-pixel – red, blue or green. As you probably know, LCD monitors yield the necessary color of a sub-pixel by using an ordinary color filter. The filter of course has no effect on the response time, which is absolutely the same for sub-pixels of any color. So there is no need to specify the color of the sub-pixel. It is simpler to assume that “white” means the state of the maximum brightness of the sub-pixel, “black” is the minimal brightness state and “gray” is all the intermediary states, as if the monitor were black-and-white.

So again, in practice we usually deal with either black-to-gray or gray-to-gray transitions of the pixel state. On the physical level, a transition is accomplished by turning the pixel’s liquid crystals by a certain angle with an electric field, the two extreme positions of the crystals corresponding to black and white and the remaining positions to grays. It may seem that the process of switching from black to gray should go faster than switching from black to white since the crystals are turned round by a smaller angle, but the fact is the applied electric field not only determines the orientation of the crystals, but also the speed of their turning round. The force that affects the crystals is proportional to the square of the applied electric field. So it takes a four times smaller force to turn the crystals round by a two times smaller angle. Moreover, the crystals are affected by the forces that drive them towards their natural order (when there is no electric field applied, the crystals in the matrix are ordered and yield a pure white or a pure black color depending on the type of the matrix). These forces depend on the current orientation of the crystals and are always directed opposite to the electric field force.

The result of the interaction of the forces involved varies depending on the matrix type, TN+Film, S-IPS, MVA or PVA, but is not really satisfactory with any of them – switching between two levels of gray takes more time than a black-white-black transition on any existing matrix! The difference varies from 2-3 times with S-IPS to a factor of ten with MVA and PVA matrixes, which are very slow on black to dark-gray transitions that can take as long as 100 milliseconds and more while the black-to-white transition takes a mere 12-14 milliseconds.

Moreover, the designers of LCD matrixes found it easier to achieve very low response times exactly when it is measured with the standard “black-white-black” method. As a result, the so-called “fast” TN+Film matrixes with a specified speed of 16, 12 and even 8 milliseconds appeared. Alas, they are not 2-3 times, but only 25-30% faster than the older 25ms matrixes because the response time on halftones has in fact remained the same. And this is also the reason why it is virtually impossible to tell a 12ms matrix from a 16ms one with just your eyes, without using any special tools.

Let’s get back to the technical aspect of the matter, though. As I said above, the main problem with the response time is the quadratic dependence of the crystals-affecting force on the voltage applied to the LCD cell (on the electric field created by this voltage, to be exact). The solution of this problem has long been known under the name of Response Time Compensation.

The solid line on the graph above shows the response of an ordinary LCD cell. The applied voltage is marked in red and the brightness of the cell is marked in blue (for the sake of simplicity we can suppose that zero voltage results in zero brightness. This actually depends on the matrix type, but we need not delve so deeply into the matter now). At some moment the monitor is to change the brightness of this cell from zero to some in-between brightness (not the maximum possible). The monitor’s electronics sends a voltage of V0 to the cell to turn the liquid crystals by the necessary angle and this voltage remains constant after that until the brightness of the cell is to be changed again. Since the applied voltage is far from the possible maximum, the crystals are turning round rather slowly and the cell will have reached the desired brightness only after some considerable time.

The same effect can be achieved in a different way which is shown with the dotted lines above. The monitor’s electronics apply such a voltage to the cell that the crystals reach the necessary orientation exactly by the beginning of the next frame. In the new frame the voltage is reduced to V0 to maintain the desired orientation of the crystals. As a result, the monitor can accomplish a transition between any mid-tones in exactly one frame. And I want you to note that the LCD matrix’s own frame rate does not necessarily depend on the frame rate set up in the computer’s graphics card, so one frame can last shorter than 16.7 milliseconds (LCD monitors’ standard refresh rate of 60Hz).

This works also for transitions from a brighter tone to a darker one, except that the “boost impulse” is going to be negative. It is the dotted line on the graph above.

Although each monitor manufacturer promotes it under a proprietary trademark, the response time compensation concept has come to be known in the press and among the users as “overdrive”. This is a kind of a misnomer because the term “overdrive” refers only to the boost impulse of positive polarity as illustrated by the first figure. If the impulse is negative, as on the second figure, it is referred to as “under-drive”. So, the correct technical term is Response Time Compensation and it combines both under-drive and overdrive. Unfortunately, I have already witnessed how the term overdrive misleads people into thinking that LCD monitors only accelerate the transitions towards lighter tones, accomplished with a positive boost impulse, but this is not true. In all available monitors with response time compensation both types of compensation are implemented!

It should also be made clear that the RTC mechanism works on the lowest level possible. It processes the signal that then goes directly to the matrix. The fact is the value of the overdrive impulse depends only on the current position of the liquid crystals and the position they must be turned into. All the user-adjustable settings have to be made before the RTC block or else the RTC block would have to correct the compensation value depending on the user-defined parameters (contrast, color temperature, etc) which would be technically complex, but not really called for.

The RTC mechanism thus belongs entirely to the monitor and has no relation whatever to the graphics card, the driver, the OS or any other external object. If a monitor has RTC, RTC will work all the time, even if the monitor finds itself connected to a Tseng Labs ET-4000 graphics card on a computer running MS-DOS 5.0. If a monitor does not have RTC, it is next to impossible to emulate it with the graphics card since the emulation algorithm would have to be modified after any change in the user-adjustable settings of the monitor. Just take the 100 grades of contrast available on a typical modern monitor and the 100 grades of each of the basic colors (I mean the manual color temperature setup) and some 5 gamma compensation exponents, and you’ll get as many as 100*100*100*100*5 = half a billion variants! It would be virtually impossible to adjust the RTC emulation algorithm for each of the variants.

Software RTC emulation by the graphics card driver began to be discussed after such technology was mentioned in the descriptions of ATI’s and NVIDIA’s mobile graphics processors. The authors of the “sensation” just didn’t have a clear understanding of the RTC concept as well as of the difference between desktop and notebook monitors. The notebook’s own monitor makes up a single whole with the graphics subsystem and does not have its own settings. On a notebook, it is through the graphics chip that all the image setup operations are performed, so the requirements “the RTC block must be located after all the user-adjustable settings” and “the RTC block is in the graphics chip” are not contradicting. A desktop LCD monitor always has its own settings which can not be controlled by the graphics card – even the models that are controlled through software, like the Samsung SyncMaster 173P, have them.

But enough of others’ delusions, let’s learn more about the technical aspects of response time compensation instead. Obviously, the non-linear and non-monotonic dependence between the response time and the initial and final brightness of the pixel make it necessary for the monitor’s electronics to choose the compensation value individually, depending on the current and final state of the pixel. To do this, the RTC block includes a frame buffer that stores the previous frame. When the next frame arrives, it is compared with the contents of the buffer and the compensation value is chosen for each pixel whose brightness has changed.

Besides the above-described effect of “slow crystals”, there is also one more response-time-affecting factor – the electric capacity of the cell changes when the crystals within it are turned round. The cells of an LCD matrix are not constantly connected to a power source. The required voltage is set in them by a short impulse at the refresh frequency and is maintained after the impulse because each cell is a capacitor. Unfortunately, the capacitance of this capacitor is not constant, but depends on the position of the crystals. Suppose the voltage U0 was initially applied to a cell, but a new frame has changed it to U1. The cell capacitor took the charge Q=U1*C1 where C1 is its capacitance at the moment. The crystals begin to turn round and the capacitance changes and becomes C2 by the moment the next frame arrives. Since the charge remains the same, the voltage necessarily changes along with the capacitance, according to the formula U1*C1 = U2*C2. And the voltage changes in such a way that it now impedes the turning of the crystals. When the next frame arrives, the voltage U1 is again set on the cell and the speed of the crystals changes again, too (for the sake of simplicity I suppose that the cell’s color hasn’t changed between the frames). This step-like process can be illustrated by a diagram that shows how the brightness of a pixel is changing in time:

This graph (I took it on a BenQ FP737s-D) shows a long horizontal stretch that ends only with the arrival of the next frame. The level of that stretch is not high, but in some cases it may result in a barely visible afterglow behind moving objects. The response time compensation concept helps here, too – the cell must get such a voltage at the beginning of the first frame that it automatically reached the necessary brightness level by the end of the frame as the result of the change in the cell capacitance.

It is impossible to achieve absolute accuracy in Nature and, moreover, the monitor developers must also try to make the cost of the finished product low (the new models wouldn’t be so interesting if their price turned to be two or three times that of the older ones). The requirement for the new electronics with RTC not to be much more expensive than the older one limits its functionality, particularly the accuracy of the compensation impulse.

There are two cases possible, when the compensation impulse is too low or too high. In the former case the “ghosting” effect is more conspicuous than it might have been, but still much weaker than on RTC-less monitors based on the same matrixes.

The second case is illustrated above. The solid line shows the compensated response and the dotted line, the over-compensated response. It’s clear that the brightness of the pixel will not have only reached the desired level, but will have exceeded it by the end of the first frame, i.e. by the moment the compensation impulse will be removed. After the impulse is removed, the brightness will take some time, depending on the matrix’s inertia, to go down to the desired value.

This case is important as it gives birth to a new kind of visual artifacts you cannot see on an RTC-less monitor – they show up as stripes lighter than both the moving object and the background. Below you can see two snapshots of a black text that’s moving from right to left on a gray background. The first snapshot was made on a Samsung SyncMaster 194T monitor, which uses an ordinary RTC-less PVA matrix. We’ve got the typical “ghosting” effect, which is rather strong here due to the peculiarities of PVA technology. The text is almost illegible.

The second snapshot was made under the same conditions, but on a Samsung SyncMaster 930BF monitor which is based on a TN+Film matrix with RTC. You can see a sharp light shadow trailing behind the black text that is moving on the gray background.

On observing this effect, some hardware testers jumped to the conclusion that RTC works by first switching the matrix to a tone lighter than necessary and then into the necessary one. This is not so. Yes, the matrix receives a voltage impulse that, if maintained for long enough, would switch the matrix to a light tone, perhaps to the pure white color even. But this voltage is supposed to be removed before the pixel exceeds the desired brightness, so it is not generally correct to say that the matrix is switched through lighter midtones since it doesn’t have time to reach them if the RTC mechanism is set up correctly. All the “light shadow” effects you may see are only due to the issue of an inaccurate compensation impulse and must be considered as errors in the implementation of RTC. Normally, no such effects should occur.

However, practice shows that all monitors with RTC currently available suffer from this problem in a varying degree. The RTC error may vary from a few to a few tens of percent. That’s why a tester of RTC-supporting monitors must not only measure the response time alone, but also see to how the high speed is achieved. Otherwise, monitors with the strongest RTC artifacts are going to win every test just because sending a too-high accelerating impulse is the easiest way to achieve the lowest possible response time (and the RTC error is not accounted for in the response time measurement method).

That is why our tests of LCD monitors with response time compensation will include one more diagram which looks similar to the more traditional response time graph for black-gray-black transitions. This new diagram, however, shows the RTC error in percent. If during a transition from black (level 0) to gray (level 100) the pixel’s brightness level never exceeds 100, then the RTC error is zero. If the pixel’s brightness reached a maximum of “150” during this transition, the RTC error equals 50% (the maximum is 50% above the desired level of the pixel). The figure below shows you an example of a real-life oscillogram of the switching of a pixel in a monitor with poor RTC setup: the bottom gray line marks the original brightness of the pixel; the top gray line marks the resulting brightness; and the pink line marks the surge that resulted from the too-high overdrive impulse.

Of course, if this error is so gross that the artifacts are easily perceived by the eye, can the monitor be considered really fast? I think that besides the response time proper, such monitors should have another parameter – the time for the pixel’s brightness to get within 10% from the desired level. This time is to be measured by the “sloping” tail of the overdrive impulse and is going to be considerably bigger than the response time proper.

Talking about speed, the monitor manufacturers used to specify the response time as the total time it took to switch a pixel from black to white and to black again. This method has been changed after the introduction of monitors with RTC. If you see a remark “gray-to-gray”, “g-t-g” or “midtone” after the number, it means that the specified number denotes the averaged time of transitions between two gray midtones. In other words, the manufacturer measures the time it takes to switch the pixel between all possible midtones and then calculates the average number. Note also that they used to specify the total “black-white-black” time, while the new standard defines the response time as the time of a transition into one side only.

Of course, this change of the measurement method is mostly due to marketing reasons. The very concept of RTC implies that black-white transitions can’t be accelerated, at least on the existing panels, and RTC wouldn’t affect the response time in the slightest if it was still measured according to ISO 13406-2. But the customer should be given to understand that the new monitors are faster than the older ones, so either the term RTC must be explained in detail (and why this new 8ms monitor with RTC is faster than that older 8ms RTC-less model) or a new method of measuring the response time must be introduced that would ensure advantage to the new monitors.

I must confess I am personally very glad about the manufacturers’ decision to introduce the new measurement method. Although dictated by marketing reasons, it is logical from the technical point of view. The new monitors are really much faster than the older ones at practical use, i.e. when it comes to the midtone response time. And secondly, this way of measuring the response time gives the user a much better picture of the real performance of a monitor.

As usual, there’s some tricky issue with the new method, though. I mean the word “average”. Easy to notice, this measurement method will make a monitor that does all the transitions in exactly 15 milliseconds and another monitor that does half the transitions in 27.5ms and the other half in 2.5ms (the example is purely theoretical, of course), look exactly alike – they will both have absolutely the same response time! In other words, the averaging doesn’t tell you how the response time varies between different midtone transitions which may be important information in some cases (one of them will be presented below). Having some even sketchy response time graph for all the possible transitions in the monitor’s specification would help greatly, but I think we won’t see such a thing in near future.

In LCD monitor reviews on our site I have published only 2D response time graphs which showed transitions from black to different levels of gray and back again. Transitions between two tones of gray were not shown. Such a diagram doesn’t give you the full information about the tested matrix, but it does give more than enough info to evaluate the real-life performance of a monitor. However, we have improved the software part of our testbed to measure the speed of gray-to-gray transitions, too, and to present the results as 3D histograms.

Below is an example of such a histogram, built for the ViewSonic VG712s monitor (a 17” TN+Film matrix without RTC). The vertical axis shows time in milliseconds; the left horizontal axis shows the level of gray from which the transition occurs (from 0 to 255 stepping 32); and the right horizontal axis shows the final level of gray. So, for example, the transition from pure black (0) to light-gray (192) corresponds to the farthest light-blue column. There are all zeroes along the histogram’s diagonal due to obvious reasons, and there are also zeroes for the transitions between the lightest tones (224-255) because the monitor is tested at the maximum brightness and contrast settings when some of the lightest tones are in fact indistinguishable from each other or there’s such a small difference between them that it doesn’t allow to make any measurements with an acceptable accuracy.

And yes, the response time of this TN+Film matrix is far from perfect. The “fast” transitions into the pure white color are obscured completely by the tall columns of slow (over 20, and sometimes even over 30 milliseconds!) transitions between mid-level tones. The low but narrow line of gray-to-black transitions along the left side of the histogram can’t save the day for this matrix. Thus, TN+Film matrixes have a rather low real speed despite the beautiful numbers in their specifications.

But as soon as we take a ViewSonic VX724, a monitor on practically the same TN+Film matrix but featuring a RTC block, the picture changes dramatically: the columns are all much shorter (I’ve built both the diagrams on the same scale for better comparison). The maximum response time is 13.8 milliseconds; the minimal is a mere 2.0 milliseconds!

Unfortunately, not all RTC-supporting monitors can produce such pretty-looking diagrams as the ViewSonic’s. Below is the response time diagram of the Samsung SyncMaster 760BF which uses a TN+Film matrix, too. As you see, the diagram differs a lot from the one of the RTC-less monitor, yet some transitions still take quite a lot of time, up to 30 milliseconds. However, if you calculate the average response time for the 760BF, it will of course be much lower than that of any ordinary RTC-less TN+Film matrix.

Next goes the PVA technology represented by the Samsung SyncMaster 194T monitor (without RTC). PVA matrixes are generally very slow on transitions from black to dark-grays which may take as long as 100 milliseconds and more. This makes such matrixes unsuitable for dynamic games, of course. The diagram above agrees with what we have seen in our previous reviews: the transitions from black to dark-gray took as long as 90 milliseconds and was lowering towards the lighter tones. Yes, the monitor is quite fast on gray-black and gray-white transitions, but its average speed is going to be awful.

And this is the same PVA matrix with an RTC block added. The difference should strike your eyes – the Samsung engineers did not only manage to remove the tallest peak which remained almost unchanged. The second peak to the right is much lower, though, and the response time on the rest of transitions is on the same level (about 12 milliseconds and lower) rather than slowly declining as before.

Unfortunately, we could not find an RTC-supporting monitor on an MVA matrix to compare it with PVA.

Lastly, here is the S-IPS technology represented by the LG Flatron M173WA. Although the monitor is declared to have a response time of “12 milliseconds g-t-g”, its matrix does not use RTC. This is an ordinary S-IPS, but marked in the new fashion. On one hand, the diagram confirms the statement that a 25ms S-IPS isn’t any worse than fast TN+Film matrixes (the diagram of the ViewSonic VG712s above looks roughly the same), but it cannot compete with the new TN+Film matrixes with RTC. You don’t have much choice if you like S-IPS monitors – there are yet no S-IPS models with response time compensation on the market.

You may have noticed that 3D histograms do not bring any additional information over 2D graphs. The conclusions that can be drawn from 3D diagrams (that the specified and real-life speed of older TN+Film matrixes differ greatly, that PVA matrixes are very slow on some kinds of transitions, and that S-IPS and TN+Film deliver roughly the same speed) can be drawn from 2D diagrams as well. However, it is difficult to compare monitors between each other using 3D diagrams, so I will still offer you 2D diagrams of black-gray-black transitions, reserving the 3D format for special cases.

But enough of theory, let’s get closer to real monitors with response time compensation. There’s only one thing left to note: the RTC mechanism affects moving objects only and has no effect on the static image, i.e. on color reproduction, viewing angles, contrast, etc. So besides the response time alone, there is no difference between an RTC-less monitor and a monitor on the same matrix, but with RTC.

TN+Film and PVA matrixes are currently employed in 17” and 19” models, so many manufacturers introduced their RTC-supporting monitors in pairs. The two monitors in such a pair differ only in the size of the screen and are identical otherwise – I will discuss them in twos. As for MVA technology, AU Optronics, the manufacturer of MVA matrixes, only targets screen diagonals of 19” and higher.

Samsung SyncMaster 173P+ and SyncMaster 193P+

Samsung’s SyncMaster 173P and SyncMaster 193P have already been reviewed on our site in the articles called "New LCD Monitors from Samsung. Part II " and "Closer Look at the 19" Monitor Features. Part III ". The “plus” versions of those models feature a response time compensation block.

Both monitors we obtained for our tests were colored black. The aluminum front panel and the stand are painted a matte black color, except for the edges that remained just polished. The rest of the case is made of a smooth and shiny black plastic. The monitors both look gorgeous and what is important they are user-friendly meaning that the painted front surfaces do not reflect light back, while the polished edges are too narrow to detract your eyes from the screen. This once again makes me recall with distaste some monitor manufacturers that just can’t distinguish their models in any other way but painting them high-contrast colors and adding shiny chromium insertions.

These two monitors are identical to their “plus-less” predecessors in design. The stand has two hinges that permit to turn the screen in almost any direction. The video inputs and the power connector are located at the back of the stand.

The monitors both carry a single button. It is a Power button which also switches between the inputs (on a long press). The button is highlighted with a mild blue LED at work. The monitor is fully controlled through the MagicTune utility which I described in detail in the review of the SyncMaster 173P. I only want to give you a piece of good advice: our monitors came with MagicTune version 3.6 which took as much as 293 megabytes of disk space after installation. It turned out that most of this space was occupied by dll- and chm-files that support the various languages the utility was translated into. If you leave just the files for the language you use (make sure to choose this language in the utility’s settings before deleting the unnecessary files!), the disk space required by MagicTune becomes a much more modest 36MB.

In my previous reviews I also mentioned the DDCcontrol utility that allows controlling these button-less monitors from under Linux. The utility has matured by now, acquiring a graphical interface (GTK+) and an applet for the Gnome Panel. It supports a large list of monitors, including the 173P+ and the 193P+ (the full list of monitors and graphics cards supported can be found on the project’s website in the documentation for the current version of the utility).

Alas, the response time of the SyncMaster 173P+ is poor. The curve jumps suddenly up on dark colors like with a typical PVA matrix.

The response time has improved over the ordinary SyncMaster 173P, but not very much (the graph above shows you the pixel rise time for the sake of simplicity). Still, this monitor does have an RTC block and the block does work as can be seen on oscillograms. You see one below – it shows the pixel brightness graph during a transition from black to 50% gray (the color RGB {128; 128; 128}).

Note how quickly the brightness grows up at the beginning of the graph. But after about 15 milliseconds the graph changes into a small horizontal ledge and then into a slow rise, typical of PVA matrixes. Here is the oscillogram of the same transition on the SyncMaster 173P:

This monitor doesn’t have RTC. There are no sharp turns in the graph, but the pixel brightness is growing up smoothly. So we have made sure the SyncMaster 173P+ is really equipped with RTC as confirmed by the characteristic look of the oscillograms. Secondly, the RTC mechanism of this monitor is insufficiently aggressive. The acceleration impulse is too weak and it ends much sooner than the pixel reaches the desired brightness (the moment the rapid brightness growth stops at the 15th millisecond is exactly the moment the compensation impulse ends). Thirdly, the “ghosting” effect on the 173P+ is not only weaker than on the 173P but also shows up differently. It looks not unlike the afterglow on CRT monitors where there is a barely visible but relatively long trail after a white object that is moving on a black background.

On the 193P+, the improvement just strikes your eyes! Although this monitor is still rather slow on dark tones (this is especially clear on the 3D histogram you have seen in the Introduction section), the response time graph goes down suddenly towards the light tones, rather than smoothly as on the older 193P. As a result, the pixel rise time does not exceed 15 milliseconds on most tones and is as low as 9 milliseconds at the minimum. By the way, make note that the response time minimum does not necessarily fall on the black-white transition for monitors with RTC.

I won’t give you an RTC error graph for these two monitors because there were no obvious errors on black-gray transitions (an RTC error is a too-high overdrive impulse that leads to the white-shadow artifacts as described above). A more detailed examination reveals that there appear some errors on gray to gray transitions, but they are very small, below 10%. The maximum observed RTC error was 16%. So, although the monitors are not absolutely free from the RTC-provoked artifacts, such artifacts are not visible at everyday work unless you are looking for them on purpose.

The gamma curves on the SyncMaster 173P+ look well, except that the monitor does not distinguish between the darkest tones of blue (the blue curve just coincides with the X axis there). Other than that, I have no complaints whatever.

It’s worse with the senior model. The gamma compensation value is too low, so the onscreen image seems whitish and washed-out at the default settings. Take note that the 193P+ offers you the option to adjust the gamma compensation value. The monitor’s color reproduction is much closer to the ideal if you set it at +0.3 - +0.5.

Both monitors reproduce smooth color gradients in the same manner: everything looks fine at the default settings, but when the contrast or brightness (which is obviously controlled through the matrix in these monitors) is reduced, barely visible cross stripes appear on the gradients.

The color temperature of the 173P+ is set up acceptably well. There is no big difference between the temperatures of different levels of gray.

The color temperature setup of the 193P+ is somewhat worse: the difference between the min and max temperatures (at the same settings in the monitor’s menu) may amount to 2000K, which is rather too much.

Both monitors have about the same maximum brightness (the senior model is a little brighter, but the difference is negligible) and contrast. The latter seems good if compared with TN+Film monitors for which the typical level of black is about 0.7-0.9cd/sq.m, but as you know from our previous reviews, Samsung’s PVA matrixes can show much better numbers. On the other hand, the contrast ratio of the SyncMaster 193P, the predecessor of these monitors, was not very high and was much lower than that of the SyncMaster 910T and the 920T. I guess controlling the brightness through the matrix rather than through the backlight lamps is the reason for that (unlike the 193 model, the 910 and 920 adjust their brightness through the lamps).

Returning to the main topic of this review, i.e. to response time compensation, the SyncMaster 173P+ and 193+ leave an ambiguous impression. On one hand, these monitors are considerably faster than their predecessors, but on the other hand, they are still not fast enough. Their response time on the darkest colors is still high. And as for the design and the static-image-related characteristics (color reproduction, brightness and contrast, viewing angles, etc), these models have not improved in the slightest. RTC is the only point of difference from their predecessors, but RTC does not have any effect on the static image.

Samsung SyncMaster 970P

The lifecycle of the 173rd and the 193rd series proved to be short. Just as the arguments on was it at last possible to play games on PVA matrixes were reaching their climax at various Internet forums, there came the news that the 173P+ and the 193P+ would soon be taken out of production and would be replaced with SyncMaster 770P and SyncMaster 970P models with a yet lower response time.

We only managed to find a sample of the senior 970P model for this review, but I think that most of its results can be extrapolated to the SyncMaster 770P since these two models make up a pair similar to the above-described 173P+ and 193P+. In other words, the size of the screen is the single important point of difference between them.

The SyncMaster 970P is made in a completely new case no other monitor from Samsung has ever had before.

The front panel of the 193P+ was made of aluminum (of painted aluminum when the case was red, blue or black), but the case of the 970P is wholly made of smooth white plastic with decorative light-gray inserts. There is not a single metal thing here – even the Power button has lost its chromium plating and is now made of translucent plastic.

A long folding “leg” is fastened on the rather massive rectangular base. Besides the top and bottom joints, there is now a third joint exactly in the middle of the “leg” thanks to which the 970P permits to adjust the height of the screen in a wide range, just like monitors with classically designed stands (the screen height range was rather limited with the 193P+ and its screen also moved forward and backward as you changed the height). And like with the 193P+, the screen can be positioned horizontally or even upside down. You can fold the monitor up and mount it on a wall or pivot the screen into the portrait mode.

The single control here is the Power button, located in the center of the stand and made of translucent plastic. It is highlighted with a blue LED at work. This button also switches between the monitor’s inputs – you should press and hold it for a few seconds to do that. The rest of the monitor setup must be performed through the MagicTune utility (as far as I know, version 3.6 works normally with the 970P). Unfortunately, the above-mentioned DDCcontrol utility does not yet support the 970P, so all Linux users who want to buy this monitor have to wait for a new version of the utility or, if the monitor is already purchased, contact the authors of the project and help them add the 970P support. You should run the console command “LANG= LC_ALL= ddccontrol -p -c -d” and send the output data to the DDCcontrol mailing list at the address ddccontrol-users@lists.sourceforge.net.

The monitor’s connectors are implemented in a curious fashion. The 193P+ has them at the back of the stand, but the stand of the 970P has a non-detachable “tail”. The tail ends in a box with a power and a DVI-I connector (you can attach either a DVI-D or, via an adapter, an analog D-Sub interface to this connector). To tell you the truth, I can’t comprehend the point of this solution. The monitor’s stand is larger than the 193P+’s, so I don’t think anything prevented putting the connectors on its rear panel. The box itself is not handy as you can’t detach it from the monitor and it doesn’t have its own fastening while the length of the cord is only about 20 centimeters. And the strangest thing is that there is virtually nothing inside the box, besides the two connectors…

So I hesitate to judge the exterior design of the SyncMaster 970P as against the earlier models. It has its strong points like the wide range of screen height adjustment, but it has bad points, too, like the odd box with the connectors, the rather big base, and the use of plastic instead of aluminum. So choosing between the design of the 193P+ and the 970P is a matter of personal taste.

Let’s now turn to the tests. The monitor is declared to have a response time of 6 milliseconds, i.e. 2 milliseconds smaller than that of the SyncMaster 193P+. My measurements prove that the RTC mechanism of the 970P is really set up more aggressively:

The monitor is still rather slow on the darkest tones, but its speed improves quickly towards the lighter colors and doesn’t change much on them. Compared with the 193P+, the SyncMaster 970P is obviously faster.

Alas, the speed increase is accompanied with an increase of the RTC error. Below you can see the 970P’s RTC error graph which shows how brighter than necessary the pixel becomes during a transition from black to a level of gray:

I don’t say the error is big. The peak is at 17% only. Yet, there are errors and the RTC artifacts are going to be more conspicuous on the 970P than on the 193P+. This is the price for the lower response time.

I also took the response time graph at 75Hz refresh rate as a kind of experiment (in the rest of the cases the reviewed monitors worked at 60Hz refresh rate) and was greatly surprised to find that the shape of the graph differed much from the above one:

This graph looks more like the SyncMaster 173P+’s. The monitor has become considerably slower and the decrease of the response time from the darks to the lights is now less abrupt. The shape of the graph resembles a graph of an ordinary PVA matrix without response time compensation (well, an ordinary PVA is still much slower than that). Most of RTC errors have disappeared, too, because the overdrive impulse is obviously too weak, so where could the errors come from? I want to note that the monitor was attached to the digital output of the graphics card during the tests.

Apart from response time, the SyncMaster 970P proved to be much alike to its predecessor. Like on the 193P+, the gamma compensation exponent is too low at the default settings, and the image looks pale and faded.

This can be corrected by increasing the gamma in the monitor’s settings.

The backlighting is uniform, and the viewing angles are typically wide as they are with all PVA matrixes: almost 180 degrees as far as contrast is concerned, but with noticeable distortion of colors on a deflection of 40-45 degrees from the normal. The monitor reproduces smooth color gradients perfectly at the default settings, but there appear cross stripes on them as soon as you step down the monitor’s brightness or contrast setting.

The color temperature measurements produce almost the same results, except that the image is generally colder on the 970P than on the 193P+. The difference is negligible, about 200-500K, so you can hardly spot it without special tools.

The contrast ratio of the 970P is unfortunately even lower than that of the 193P+ and is as low as the typical contrast ratio of TN+Film matrixes. If the monitor displays a black background, you can see even in daylight (not to mention working in darkness!) that it is actually dark-gray rather than true black.

So the 970P differs from the 193P+ with a more aggressive RTC mechanism and with the new design of the case, so if you are satisfied with the looks and the speed of your 193P+, there is no sense in replacing it with a 970P. But if you are shopping for a new monitor, you should consider the 970P first – the 193P+ is probably going to leave the market soon.

Among the monitor’s drawbacks I would name some design solutions I could not quite comprehend, the rather low contrast ratio (for a PVA matrix), and the stronger RTC artifacts (if compared with the 193P+). The artifacts are not so strong as to cause any discomfort, though. And despite the noticeable reduction of the average response time, the monitor is still very slow on transitions between the darkest tones.

The users of the SyncMaster 970P should also take note of the difference in the monitor’s reaction at different refresh rates. In my tests the monitor proved to be considerably faster at 60Hz than at 75Hz. On the other hand, if you don’t want the maximum speed, but want to get rid of the RTC-provoked artifacts, you may even want to set the refresh rate at 75Hz.

Samsung SyncMaster 730BF and 930BF

The RTC innovation is not limited to PVA matrixes, although has the biggest effect on them, because the midtone response time has traditionally been the scourge of PVA technology. So along with the above-described 173P+ and the 193P+, RTC-supporting monitors with TN+Film matrixes came out from a number of manufacturers like Samsung, BenQ, ViewSonic, etc. Samsung’s 730BF and 930BF were the first to come to our test lab.

Like the 173P+/193P+ and 770P/970P pairs, the SyncMaster 730BF and 930BF mainly differ in the size of the screen. They use the same matrixes, they have identical specified parameters (including the average response time of 4 milliseconds), they offer the same setup options and they have identical cases. That’s why I’m going to discuss them both at once.

The 930BF/730BF are designed in the matte black plastic case with a silver bezel typical of Samsung’s inexpensive monitors. There are hardly any differences from 710 and 713 series models that had a similar market positioning: the place and the appearance of the control buttons have changed, and the whole front panel used to be silver before.

The control buttons are placed along the center of the bottom edge of the case on a small rectangular ledge. Quick access is provided to the MagicBright feature (five sets of monitor settings), to the brightness parameter, to switching between the inputs and to the auto adjustment feature. The Power On button is located on the right and I think it is a better position than in the center, as on some older models, where you could accidentally press it while setting the monitor up. The button is highlighted with a soft green LED. The onscreen menu is the standard menu of Samsung’s modern monitors and you can of course control the monitor through the Windows-based MagicTune utility.

The monitor has an analog and a digital input, and an integrated power adapter. Unlike on the 970P, there are two separate connectors for the two inputs: D-Sub for the analog signal and DVI-D for the digital signal (it is impossible to connect an analog cable to this connector unlike to the 970P’s DVI-I). In my tests I attached the monitor to the digital output of the graphics card.

This is the graph of the SyncMaster 930BF – the graph of the junior model is absolutely the same. The RTC technology is at its best here: the response time is everywhere lower than on the black-white transition (where it is a little above 10 milliseconds). Without RTC, analogous matrixes have a response time of 23-27 milliseconds at the maximum, but now this maximum is much lower. If we don’t count in the black-white-black transition, the full response time of this monitor is as low as 7 milliseconds!

Alas, this impressive result was achieved through inadequate means, in my opinion:

This is the RTC error graph for the 930BF (it looks the same for the 730BF). You can see that the error amounts to tens of percent, which is just horrible in comparison with the above-discussed 970P. As a result, a white trail is perfectly visible even in Windows desktop applications when you’re dragging a window (especially at low contrast and brightness settings), not to mention in movies or games:

You don’t have to look for this effect; it is perfectly visible at ordinary use of the monitor and leaves a nasty impression at work as well as in games.

As for the static image, these two monitors do not differ much from many other models on TN+Film matrixes. The monitor reproduces color gradients without any obvious problems; the viewing angles are ordinary for this matrix type (which is another way of saying that the vertical viewing angle is too small). The backlighting is not strictly uniform: narrow, but clearly visible light streaks can be seen on a black background along the edges of the screen even in normal daylight. Well, this is not an untypical thing for TN+Film, either.

The gamma curves for the 730BF and 930BF are nearly identical, so I only offer you one graph, for the senior model at the default settings. The monitor is well-calibrated, but the contrast setting is higher than necessary as the characteristic bend of the curves at the top right of the graph indicates. As soon as you reduce the contrast by a few percent, the bend disappears while otherwise the curves remain unchanged. I didn’t observe any loss of dark tones at reduced brightness or contrast settings.

The color temperature setup of the two models differs a lot. It’s more or less correct on the 930BF where there is a small difference between the temperatures of different tones of gray, while the 730BF is just predisposed to blue hues. Its color temperature is high above the norm. The “Warm” mode looks the worse in practice because you clearly see the difference between the white color that has a red-yellow hue typical of the low temperature and gray whose temperature is above 7000K, i.e. among cold, blue hues. It is really hard to use the monitor in this mode without additional calibration. The “Normal” mode produces a similar difference in numbers (it should actually correspond to 6500K temperature), but it doesn’t strike your eyes that strongly.

The brightness and contrast parameters are exactly what you may expect from a good modern TN+Film matrix. I want to note the fact that the 730BF seems to have a slightly higher brightness of the backlight lamps. It has a brighter white and brighter black than the 930BF, although their contrast ratios are similar.

So, the main and very serious drawback of the SyncMaster 730BF and 930BF monitors is their very shoddy implementation of RTC: the RTC error amounts to tens of percent, so any moving object is accompanied with visual artifacts. The artifacts are so strong that they even make working with desktop applications uncomfortable: light, almost white, trails follow behind the mouse cursor and moving windows. The trails become the more conspicuous if you reduce the brightness and contrast below the default (but at the default settings the brightness of white is 200cd/sq.m, i.e. two times above the level recommended for work with text). I could also complain at the inaccurate color temperature setup of the 730BF, but this defect is really negligible against the gross problems with the RTC setup!

SyncMaster 760BF

The SyncMaster 760BF (and the 19” SyncMaster 960BF which will be presented to you in our upcoming reviews) is based on a TN+Film matrix with response time compensation.

The superb design of the case distinguishes this monitor from earlier models. I even think it looks prettier than the “image-making” SyncMaster 770P and 970P. The monitor catches your eyes at once and it does so not with contrasting black-and-white elements or mirroring inserts or extra-bright LEDs or some other “visual junk”, but on the contrary, with its low-key, restrained and eye-pleasing appearance. The case is made of smooth white plastic with a decorative light-lilac bezel which does not stand out much against the white background. The base is mostly of the same light lilac color with a white edging.

The single inconvenience of this design is that the glossy white plastic may reflect the objects behind your back (windows, lamps, etc), I personally did not feel any discomfort at work – the reflections and flares are not as strong as to distract you. Still, if you’ve got this monitor, you should keep this fact in mind as you choose where to put it.

The monitor’s stand is deliberately rounded which adds it more charm against the typical angular models you can see in shops. The functionality of the base cannot match that of the 173+/193+, not to mention the 770P/970P, yet the portrait mode is available. The screen can be lowered almost to the level of the desk, but you can’t flip it backwards or place horizontally as you can with the 173P+. The screen of the 760BF can be deflected backwards by no more than 30 degrees. The monitor is folded up for transportation, but forwards rather than backwards.

The connectors are located at the back of the base, under the raised part that resembles a carry handle (well, you can really use it as a handle if necessary).

So it is rather easy to plug in the connectors because the “handle” is above them and does not intervene, but when the monitor stands on the desk, the connectors are almost invisible.

The monitor does not have a separate D-Sub connector, but this doesn’t mean it takes in only digital signal. You can attach either a digital cable or an adapter from an ordinary D-Sub (included) to the monitor’s DVI-I connector. The power adapter is external – a standard 14V power source of Samsung’s monitors.

There’s only one button of the monitor – the Power button. It can also be used to switch between the analog and digital inputs. To set the monitor up you must use the Windows-based MagicTune utility. The current version of the Linux-based DDCcontrol program I mentioned above does not yet support the 760BF or the 960BF. The Power button is highlighted with a soft blue LED at work.

The response time graph does not differ from the SyncMaster 730BF’s one and it shouldn’t. The manufacturer declares an average response time of 4 milliseconds for both models.

But the RTC error graph is just horrible. We’re dealing with an error of over 100% here – note that I even had to adjust the scale of the Y axis to fit the graph in!

Moreover, I also discovered that the monitor is sluggish (up to 32 milliseconds) at switching between two light tones. It seems RTC just does not work at all on such transitions – the numbers are too alike to the performance of a typical RTC-less TN+Film matrix (see the diagram at the beginning of the article). Fortunately, the RTC errors that impressed me so much on black-gray transitions are noticeably lower on gray-gray ones. But “lower” does not mean you can disregard them altogether as they still amount to 40-60%!

Alas, the SyncMaster 760BF has not improved since the SyncMaster 730BF as concerns the RTC implementation. The RTC error is still so big that it makes working in Windows uncomfortable. The monitor’s behavior on transitions between light tones is strange, too.

The gamma curves are similar to those of the 730BF and the 930BF. They are generally good, but there is a characteristic bend in the top right part of the graph that betrays a too-high contrast setting. This bend disappears as soon as the contrast setting is lowered.

The color temperature is set up with a definite bent towards colder hues. Even the “Warm” setting gives you a temperature of about 6500K which should correspond to “Normal” rather than “Warm”. The difference between the different levels of gray is not too high, but noticeable.

The white brightness of the 760BF is a little lower than of the 730BF, but the black brightness is, on the contrary, a little higher, so the contrast ratio is lower, too. The contrast ratio still remains at an acceptable level for matrixes of that type, though.

So, the SyncMaster 960BF differs from the SyncMaster 730BF in the design of the case mostly – a very pretty and elegant case, I should confess – and the lack of control buttons. The characteristics of the two monitors are very, very similar, and the 760BF has the most serious defect of the previous model – the most inaccurate RTC setup. RTC artifacts are all too visible. Alas, this almost negates all the advantages of this monitor. It turns to be suitable for simple office work only, but why would you need a monitor with RTC for office work? I hope Samsung will solve the RTC setup problems in their future monitor models – at least they’ve managed to almost eliminate them in their monitors on PVA matrixes!

ViewSonic VX724 and VX924

Of course, Samsung was not the only manufacturer to produce RTC-enabled monitors. ViewSonic did so, too. In the market positioning and functionality, the VX724 and the VX924 models (they only differ in the size of the screen) correspond to the above-described Samsung 730BF and 930BF. They have a simple, plain case and a TN+Film matrix with a declared response time of 4 milliseconds (the number of 3 milliseconds has recently appeared; ViewSonic says this number does not imply a new matrix, but that they just measured the response time with more precision and found the average response time to be 3 rather than 4 milliseconds. Thus, there is absolutely no difference between ViewSonic monitors labeled “4ms” and “3ms”). Sometimes you can see the number “5ms” which is not the averaged time of gray-to-gray transitions, but the black-white response (it seems to be the pixel rise time rather than the full response time; for example, the full response time of the above-described monitors from Samsung was about 10 milliseconds, which gives you those 5ms if divided by half).

The case of the monitor should be known to you from our previous reports. ViewSonic often uses it in its inexpensive models. The main disadvantage is that the stand is rather tall, yet you cannot adjust the height of the screen. You may not like it if you’ve got a low chair or a tall desk and you have to look at the screen from below. For example, the screen of the VX924 is 4 centimeters higher than the screen of the 930BF, while the screen of the VX724 is 5 centimeters higher than the screen of the 730BF.

The monitor is equipped with an analog and a digital input (implemented as separate connectors), and an integrated power adapter.

The control buttons are located at the bottom of the front panel and are labeled in ViewSonic’s traditionally incomprehensible way. Instead of the typical labels “Menu” and “Select” or appropriate icons, there are just the numbers “1” and “2”. The functions of the buttons are explained in bottom string of the onscreen menu which looks and behaves like a typical ViewSonic menu.

The monitor provides quick access to the brightness and contrast settings as well as to switching between the inputs. The auto-adjustment can only be started from the monitor’s menu. Note also that if you choose the “sRGB” color temperature setting in the menu, the brightness and contrast settings become blocked.

At the default settings, smooth color gradients are reproduced rather well, although two or three cross stripes can be discerned that should not be there. But if the contrast setting is reduced, there appear more conspicuous stripes. The matrix’s backlighting is rather uniformly distributed on the screen, although on a closer inspection you can note that there are lighter areas at the bottom and top of the screen, near the edge of the matrix.

The response time graph looks odd in comparison with older RTC-less monitors, but quite normally for the new monitors. It does not differ much from the graphs of the above-described TN+Film monitors from Samsung.

The graph of the VX724 differs but slightly. The pixel rise line goes a bit higher, but has the same shape. The difference between the two models is very small, especially compared with how faster these monitors are against ordinary TN+Film matrixes.

The RTC error graph is obviously better than with the Samsung monitors. There’s only one 23.5% peak as opposed to nearly 40% with the SyncMaster 930BF and 150% (!) with the 760BF.

The graph of the VX724 looks even better. The maximum error is just a little over 10%. Well, the map of transitions between different tones of gray has some errors of about 60%, but the overall result is still much better as compared with the Samsung monitors.

The RTC error is small on black-gray transitions which are prevalent in Windows desktop applications, so the RTC-related artifacts are hardly perceptible and are not discomforting at all. They are not conspicuous in games and movies, either, unless you are looking for them on purpose. In this case the excellent response time of the monitor makes up with interest for the accompanying visual artifacts.

The gray-to-gray transitions histogram shows that the monitor is free from the problems with light-gray to light-gray transitions we have seen on the SyncMaster 760BF. The histogram is quite uniform, with a maximum of about 14 milliseconds (the maximum was as high as 32 milliseconds on the 760BF!)

So, the strong RTC artifacts and high response time on light tones is not the common problem of all monitors on TN+Film matrixes, but a problem of Samsung who did not implement the RTC mechanism well enough. The RTC artifacts are less strong on the ViewSonic monitors, and the problem with the light tones is not observed at all.

The gamma curves of the monitors go below the necessary level (you see the VX924 graph above, but the graph for the VX724 is almost the same). It means the onscreen image is going to look darker and have a higher contrast than necessary. When the brightness and contrast settings are reduced in the monitor’s menu, the curves go up a little, getting closer to the theoretical curve for gamma=2.2.

The color temperature setup of both monitors is acceptable, but the 19” model is a little better in this respect: the difference between different levels of gray is smaller on it. As for the junior model, the 5400K setup looks the worst of all: the white color does have the said temperature, but light gray is close to 7000K!

The contrast and brightness parameters of these monitors are at an average level as TN+Film matrixes generally go. The 17” model was the brighter of the two Samsung monitors whereas here the senior VX924 is brighter than the VX724, their contrast ratio being almost the same (except at the 100nit settings).

So while the first TN+Film monitors from Samsung with RTC call for improvements, ViewSonic has offered much better products. Its monitors are actually faster than Samsung’s, considering the problems of the latter on transitions between light tones, but have a much lower RTC error. In most cases you can’t discern any RTC artifacts on the ViewSonic monitors! Both these advantages result from a more accurate RTC setup.

As concerns the static image, these monitors do not differ from the models on the same, but RTC-less matrixes. The RTC mechanism can only affect a moving object, and apart from this feature, these monitors haven’t changed since their predecessors.

Conclusion

This article does not cover all the new LCD monitor models with response time compensation. Unfortunately, we have not yet tested BenQ’s models on TN+Film as well as PVA matrixes, and we don’t have ViewSonic’s VP191 and VP930 on MVA matrixes, but anyway, we can already make a few observations.

The response time compensation technology is going to do the most good to PVA and MVA matrixes which used to be awfully slow on midtone transitions and, accordingly, unsuitable for dynamic games. This review has shown you that the new models on PVA matrixes employ the RTC mechanism to achieve a considerable response time reduction for a majority of color tones, except for the darkest. The latter problem will probably be dealt with as the RTC technology improves further, but even now we can say that the new LCD monitors on PVA matrixes suit not only for office work, but also for many dynamic games. Coupled with their traditionally good contrast ratio, color reproduction and viewing angles and wide market availability (they are employed in 17” models, too), this makes them a most appealing option for the home user.

TN+Film matrixes that have been formally considered the fastest available, have now become the fastest for real. Their response time on midtones used to be as high as 25-30 milliseconds, but now the RTC mechanism solves this problem completely. For example, the maximum response time of the ViewSonic VX724 and VX924 monitors is only 14 milliseconds, the average response time being even lower (RTC-less matrixes do quite a number of transitions within that 25-30ms range, while the new RTC matrixes do but a few transitions in 14ms or a similar time). The new TN+Film matrixes are obviously faster than the ex-champions in “real” speed, S-IPS ones.

The artifacts resulting from an inaccurate setup of the RTC mechanism are a temporary phenomenon. The example of the Samsung 193P+ and the 970P shows that the new model on the same matrix has a better RTC setup and has a considerably better response time at moderate enough artifacts, while the example of the Samsung 930BF and the ViewSonic VX924 shows how the more accurate RTC setup makes the ViewSonic a much better product in terms of response time and RTC error.

I guess it is going to develop like with the “fast” 16ms TN+Film matrixes (they are not really fast as explained above) which not only had a different response time, but also color reproduction. Unlike the 24-bit 25ms ones, they were 18-bit matrixes, and their image quality was awful at first: striped gradients, very small viewing angles, and a really negligible advantage in speed over the older matrixes (as you could learn from our reviews, those matrixes could only do black-white-black transitions within those declared 16 milliseconds). But eventually the manufacturers improved the angles, corrected the FRC algorithms that were responsible for displaying 24-bit color on a 18-bit matrix and now the new 16, 12 and even 8ms matrixes are no worse than the older 25ms ones in any image-related parameter and have a better response time, even though not such a good response time as their specifications promise.

I think the RTC mechanism is going to develop in a similar way. In this review you have seen the representatives of the first generation of RTC-supporting monitors, yet they already ensure a much better response time, even though the improved speed is accompanied with a new type of undesired image artifacts. But as the algorithms and technical aspects of RTC improve, we will hopefully see the response time getting lower while the artifacts becoming negligible, if not vanishing at all. Well, the positive effect from the reduced response time is much bigger than the negative effect from the RTC artifacts even on some new models (like on the above-described ViewSonic monitors and on the PVA-based models from Samsung). So the value of the RTC innovation is doubtless even now.