Visual tests

Visual tests

Having high tech tools is once thing, but being able to personally step back and appreciate results is another. The easiest way is to often simply compare the screens. Starting the game UT 2004 on the monitors and comparing the results could be enough. If there is still a doubt, it’s possible to look at the fastest scene and long tracking shots of a couple of movies and analyze the result.


Even if two of these screens claim faster response times than the AS4314UTG, officially a 20 ms, none of the three monitors could compete with the Iiyama. After this the ranks are tighter and none of these screens can be qualified as fast. All three have a strong afterglow, that is too much for a game where the character does a lot of jumping around. Based on this, the second most reactive screen (or the least slow) is the LG L1920B. This is unexpected because it was supposedly the slowest with a response time of 25 ms. The third and fourth places are, respectively, the Philips 190S5 and Samsung 193P screens.

The result is final. There are strong differences between the screens. Here are the winners (and losers) of the visual assessment test:


It’s interesting to compare our results with the monitors’ specifications.


It’s ironic. If we were to rate the screens based on manufacturers claims the order would be reversed compared to our visual assessment.
First conclusion: never trust the specifications!

The ISO measurement

In the beginning, there was ISO...

ISO, the International Organization for Standardization, is a network of 146 countries. Its main activity is to establish technical norms.

The flat screen norm is named ISO 13406-2. This 150 page massive volume indicates the guidelines to follow regarding dead pixels, contrast ratios, viewing angles etc. This norm also indicates the procedure to measure screen response time, representative of screen reactivity. It also determines how fast the screen displays pictures. The lower the response time (measured in milliseconds) the less afterglow a screen should have. Afterglow is a trail of light left behind bright objects in motion (it is particularly characteristic of old laptops).

The norm stipulates to obtain the overall monitor response time, add the measured rising and fall time. In practice, this involves measuring the change from a white to a black pixel and then the reverse. The extreme parts of the signal are then subtracted to keep the 10% to 90% part of the signal.


The ISO measurement

We followed the norm’s instructions. It’s not possible to directly obtain the measurement as the first operation is to calibrate a screen’s colors. This is imperative to do or the measurement could include “dark grey – light grey” instead of “black - white”. This situation could give radically different results from one setting to another.

Once calibrated (with the manufacturer’s brightness level), here are the results of each screen:


If this classification is compared to the visual test of games and films:


The order is completely reversed. First in the visual test, the Iiyama is last with the ISO measurement. The Samsung and Philips provide equivalent results. So if there was still a doubt, now we know that the ISO norm isn’t representative of a screen’s real quality and characteristics.

These results demonstrate another interesting point. Besides the LG, none of the screens gave its claimed response time, which means that panel manufacturers left the ISO norm or at least changed it. If we take a closer look at a screen’s specifications, the indicated response time often goes along with a “typ”. In this way it’s important to understand that a response time measurement isn’t from white to black and vice versa but between two grays. This changes results.

Measures between greys

Measurements between grays

Afterglow mainly affect games and movies. With games or other activities, screen pixels constantly change from one color shade to another, such as light green to dark green, red, blue, etc.

If we take a closer look at pixels, we see that they are made up of three sub pixels, a red, green and blue. Each sub-pixel is a liquid crystal cell with a color filter. So it’s possible to assimilate these sub-pixels to gray cells with color applied at the last moment to obtain colors on the screen.

In this line of thinking, it would be interesting to add the measurement of response times in changing from grey to white and grey to another color. We only kept the 10 – 90 % part of the signal. Results were interesting in that response time doubles depending on the colors tested.

How to interpret the graph

The Y axis represents response time measured by adding rising + fall time.
The X axis starts at 0 and goes up to 255, with increments of 32. The indices represent different colors, where 0 = black, 255 = white and all intermediate values correspond to different shades of grey.
The Z axis only includes three values, 0 (black), 128 (average grey), and 255 (white). These are the reference colors.

For example with the Iiyama screen, the 24 millisecond time found at the intersection of the color 0 and 96 was measured in this test: color 96 to 0 black (rising time) + 0 black to 96 (fall time).

Some of the graph’s response times appears at 0. This happens when two colors are identical or when the difference is too small to get an accurate measurement. For this particular case we put the response time at 0 and the result is ignored.

Finally, each graph is followed by a table for further interpretation. Included is the response time following the ISO norm and our measurement, which is the average of all response times found between gray. Min and Max are the minimum and maximum response time measured in the test.

Iiyama AS4314UTG
Measured response time follows a certain logic. Smaller response times were measured from 0 (black) and they increase when the final color is lighter.


Response time measured varied from 24 to 56 milliseconds with an average of 38 milliseconds.

LG L1920B


IPS screens have the reputation of having a similar response time between all colors. We realize here that this is partly true. The gap between “min and max” is reduced compared to other technology, but the maximum response time is still almost two times larger than the minimum.


The LG screen seems faster than the Iiyama. This time the average response time is 30 ms.

Philips 190S5


TN technology is well known to be the least stable. Our measurements confirm this reputation and the gap between the minimum and maximum response time is almost three times more.


Samsung SyncMaster 193P


Measurements are quite stable but also high, whether from black, white or average grey. The highest response times were with intermediate grays.


Results compilation
With response times between colors, ratings are already different from the one obtained following the ISO norm.


It is closer to the visual test results, but still not the right one. Even if the LG screen’s min max response times are inferior to the Iiyama screen’s, the Iiyama remains the fastest for games.
Also it would seem illogical to find the same response time for the Iiyama and Philips. With the first screen it’s possible to play UT2004, while with the other it’s much more difficult.

Finally, the measured response time doesn’t really provide useful results. Measurements from white to black and between grays don’t resemble the visual test’s results. So why can’t we evaluate a screen’s performance with such a method?

Why this measurement fails

Why this measurement fails

Flat screens are designed to work with a refreshing rate of 60 to 75 Hz. This frequency doesn’t indicate a sweep frequency (like with CRT screens), but indicates the picture rate sent by the graphic card.

With 60 pictures per second (60 Hz), the picture rhythm reaches 1 /60 = 17 ms.

At 75 Hz the picture rhythm reach 13 ms.

By looking at the above graphs, we can see that picture flow is often faster than pixel speed. At 60 Hz (1 image every 17 ms), liquid crystals are at the half-way point when the next image arrives.

With a flat screen, colors are rarely accurate in animate sequences. Fortunately, we don’t notice this. Images should quickly change from one to another and instead of displaying black, we see a dark grey. In practice, screen characters move slower than that. They don’t display radically different colors but close shades successively. The afterglow effect only appears when an object moves in a background of a radically different color.

For example, with the Iiyama AS4314UTG screen:

If the picture changes in T0 from white to black (in T1= 17 ms) the transistor applies maximum tension to the liquid crystals. This situation provides the fastest results.

At T1, the liquid crystals are in intermediate position, approximately half way between the beginning and the end (the 255 to 0 response time is 35 ms for this screen). The pixel displays an intermediate grey.

Still in T1 the graphic card changes the pixel color, it has to return to white. This is when the inertia problem shows up. What is the time required for liquid crystals to stop and come back to display white? How many milliseconds are required to slow down and reverse their movement?


The longer this time is, the more different the desired color will be from the one displayed. This is when a trail of light appears.

For the moment we are unable to evaluate this inertia time with the tools we possess. Until we succeed in establishing a new more accurate testing procedure, we will have to keep testing screens with a visual analysis of movies and games. This is the only true way to estimate a screen’s performance.

ISO measure for text

ISO measure for text

For the moment we focussed our tests on games and movies, but we must say that the ISO 13406-2 norm was written for flat screens used in a professional environment. 1999 was the year they started creating the norm and it was finalised in 2001. Back then, users dreamt of flat screens and it was still the prehistory of this market. Professional screens are destined for work in a professional environment, for example, the writing and reading documents, two relevant activities as we surf the Internet, write reports, etc.


In this context conditions are different. To get clear and sharp text, there must be a light color on a dark background or as is the case most of the time, dark on a light background. This is where the response time measurement is relevant. So, a screen’s reactivity with games and movies is different from reactivity with text.


This time, response time corresponds to visual tests.


Response times confirm our visual impressions. The LG monitor is the fastest of all four for text. The Philips and Samsung screens provide equivalent results just below the LG. All three screens are noticeably more reactive than the Iiyama. Even if it’s possible to see an afterglow effect when really close to the screen, in practice this effect is negligible. It’s not possible to play with a slow screen, but a slow screen with text can still be used without problem. The only difference is reduced user comfort.

In conclusion the “black – white – black” and “white – color (including black) – white” should only be used to evaluate a screen’s reactivity in an office environment. Response time even between grays shouldn’t be included in evaluating a screen’s performance with games and movies.

Color quality and Conclusion

Comparative test : color quality

We almost forgot the original objective of this article was a 19” screen comparative test between the attractive LG L1920B, Philips 190S5 and Samsung 193P. Not everyone’s main activity is gaming or watching movies. People also work, read documents, retouch pictures, etc.
The precedent page mentioned use in an office environment. We now will address picture quality.

We come back to our tried and true method of calibrating a screen with our LaCie colorimeter.

How to Interpret the graph

X axis: 0 black to 100 white
If Delta > 3, the desired color is noticeably different from the color displayed.
1< Delta E < 2: colors are accurate
Delta E < 1: the result is perfect.

Contrast ratios measured

This method is once more recommended by the ISO 13406-2 norm. (You might want to take the opportunity to look at this article: "Focus on LCDs" for the problems with this measurement):
-maximum brightness divided by black brightness = contrast ratio.

The three screens have a white close to 200 cd/m². There is a difference with black, a clear advantage for the 193P, the only one able to satisfy requirements of professional photographers.
For most of us, however, these three screens are excellent. We have to remind you that, not so long ago, contrast ratios were rarely over 200 : 1…


LG L1920B


IPS technology has considerably improved during the last three years. It used to be a short-winded technology with viewing angles and color quality inferior to VA panels. These criticisms are now behind them.
The L1920B displays nicer colors than most CRT screens. Its response time is satisfactory especially if we consider the black – white – white result (and vice versa, both the same speed).
Of the three 19” screens tested it’s the fastest to display text with the least afterglow effect when the text is scrolled down.
People spending a lot of time on Internet will appreciate this quality.


Philips 190S5FG


The 190C5FG is equipped with a TN panel but provides excellent color. The vertical viewing angle isn’t great, however, when looking from below.

Otherwise, gamers might be a little disappointed with game quality. Despite a claim of a 12 ms response time there is still has a strong afterglow effect. However, this is no surprise as we already noticed this problem with several 17” screens equipped with 12 and 16 ms Samsung and LG-Philips panels.

We are now anxiously waiting for the 8 ms Hydis and AU Optronics panels.





Samsung 193P



It’s quite original that the 193 P doesn’t have any controls on the screen. All adjustments are made directly via accompanying software in Windows.
Also, unlike the pre-version tested a few months ago, this monitor had good adjustment. After calibration it was even better. The screen claimed a 1000 : 1 resolution and it lives up to its promises.

At 6500 K it’s perfect from black (0.19 cd/m² two time deeper than with the LG and Philips) to white.

Overall a nice design combined with great color quality makes it an exceptional screen if you aren’t too much into gaming. Its only down side was a poor visually estimated response time which doesn’t make it the ideal screen for games.