What distinguishes a good display from a bad one: screen testing technique. How to correctly measure with a luxmeter

Our methodology for testing screens of smartphones and tablets consists of four relatively simple tests:

• Measuring the maximum brightness of black and white fields, as well as calculating the contrast from the obtained values;
• Definition of color gamut and white point;
• Color temperature measurement;
• Measuring display gamma using the three primary colors (red, green, blue) and gray.

The results of each of these tests characterize the individual features of the screen, so when finalizing the quality of the display, it is worth taking all four tests at once, and not any of them separately.

To determine each parameter, the X-Rite i1Display Pro colorimeter and the Argyll CMS software package are used. In this article, we will talk about each test, and also explain how to read and understand the graphs we received. So let's go!

⇡#Determining the maximum brightness of black and white fields, as well as calculating the static contrast

At first glance, this test seems to be the simplest. In order to measure the brightness of a white color, we display a completely white picture on the screen and measure the brightness with a colorimeter - the resulting value will be called the brightness of the white field. And in order to measure the brightness of black, we do the same with a completely black picture. The brightness of white and black fields is measured in cd/m2 (candela per square meter). The contrast is even easier to recognize: by dividing the brightness of the white field by the brightness of the black, we get the desired value. A nearly perfect smartphone or tablet screen has a static contrast ratio of 1000:1, although results of 700:1 and above are also excellent.

Unfortunately, this test can only be called simple in appearance. In recent years, smartphone manufacturers have followed the same path as TV manufacturers: they began to add various “enhancers” of the image to the firmware of the devices. This is not surprising, but rather natural, because almost all major smartphone manufacturers are developing TVs and / or monitors.

In the case of liquid crystal displays (with OLED everything is exactly the opposite), these “improvers” usually work as follows: the fewer bright dots on the display, the lower the brightness of the backlight. This is done, firstly, in order to provide a greater depth of black in those images in which there is a lot of this color. And secondly, in order not to waste electricity: if the image is mostly dark, it makes no sense to shine the backlight to its fullest - it is logical to mute it.

The problem is that the real contrast does not increase from this: when using the “enhancer”, the light areas in the dark image will also become a little darker, so the ratio of white and black brightness will at best remain the same as with full backlight. That is, if on a display equipped with dynamic backlight optimization, you measure the luminosity of white and black fields, as described above, and then simply divide one by the other, you will get not a real contrast value, but a rather abstract figure. Most often - very tempting (like 1500: 1), but having nothing to do with real contrast.

To get around this problem, we have ditched images filled entirely in black or white in favor of an image that is 50% white and 50% black. We have two such pictures (50-50 and 50-50-2 in the figure below), respectively, we measure the luminance values ​​of the white and black fields both in the upper and lower parts of the display - and average the contrast values ​​​​calculated after dividing these numbers .

A complete set of test images for measuring the characteristics of LCD displays

Optimization introduces a fair amount of error, including in the measurement of other screen parameters - color temperature and gamma. Therefore, in order to obtain more correct results, we also use for these tests not completely filled with color pictures, but squares that occupy about 50% of the screen area. At the same time, the background is filled with white or black color so that the ratio of light and dark points on the display is more uniform for all test images and dynamic adjustment of the backlight introduces minimal distortions into the results.

This approach makes it possible to increase the realism of the obtained contrast values ​​and other display parameters.

⇡ # Color gamut measurement

Our eye is able to perceive a huge number of colors, tones, midtones and shades. Here are just the most modern displays of mobile devices - like their "big brothers", TV screens and monitors - are not yet able to reproduce all this riot of color. The color gamut of any modern display is very much inferior to the part of the spectrum visible to the human eye.

The graph below shows an approximate range of the visible (optical) region of the spectrum, or "color gamut of the human eye." The white triangle on it highlights the sRGB color space, which was defined by Microsoft and HP in not very distant 1996 as the standard color space for all computer equipment that involves working with color: monitors, printers, and so on.

Compared to the entire optical region of the spectrum, the sRGB color gamut is not that great. And compared to the full spectrum of electromagnetic radiation (not shown in the graph), it’s a grain of sand in the sandbox

To be honest, working with color is far from simple, extremely confusing and not as well standardized as we would like. However, albeit with a fair amount of conventionality, we can say that most digital images are designed to use the sRGB color space.

From this there is such a consequence: in the ideal case, the color gamut of the display should match the sRGB color space. Then you will see images exactly as their creators intended. If the color gamut of the display is smaller, then the colors lose their saturation. If more, then they become more saturated than necessary. A "cartoonish" picture with oversaturated colors tends to look prettier, but this is not always appropriate.

Here and below: all the differences in the example images are exaggerated for clarity. That is, quantitatively, they do not necessarily correspond to the difference that can be seen on real displays, but simply show general trends.

Good color gamut values ​​are from 90 to 110% sRGB. Displays with a color gamut of 90% already produce a too faded picture. Screens with a wider color gamut can noticeably oversaturate colors and make the picture overly colorful.

Such display settings should not be considered very successful either, when the color gamut triangle in area is close to sRGB, but is highly distorted: this means that, instead of the color provided for by the standard, you will see some color significantly different from it on the display. For example, olive instead of green or carrot instead of rich red.

A set of images to determine the color gamut

Also, while measuring the color gamut, we find the coordinates of the white point and indicate it on the graph. We will talk about it in more detail in the next section.

⇡ # Determination of color temperature

The ideal color temperature for white is 6500 Kelvin. This is due to the fact that it is this color temperature that characterizes sunlight. That is, such a white color is the most natural and familiar to the human eye. More "warm" shades of white have a temperature below 6500 K, for example 6000 K. More "cold" - higher, that is, 8000 or 10000 K and so on.

Deviations in either direction are, in principle, undesirable. At a lower color temperature, the image on the screen of the device becomes reddish or yellowish. At a higher one, it goes into blue and blue tones. It should also be borne in mind that the white point of the display may, in principle, not fall on the Planck curve, which determines exactly the white color. On such a display, white has a very undesirable greenish (a very characteristic flaw in early AMOLED displays) or purple tint.

Ideally, for all grayscales - which are essentially the same white color, but of lesser brightness - the color temperature and color coordinates should be the same. If they differ within insignificant limits, then there is nothing wrong with that. If they change sharply from gradation to gradation, then on such a display, different parts of black-and-white images acquire a different shade and, in general, turn out to be slightly “rainbow”. It's not very good.

Test patterns used to measure color temperature

We measure color temperature for gradations 10, 20, 30...100% of pure white. The result is a graph that looks like this:

⇡#Measurement of display gamma by three primary colors (red, green, blue) and by gray color

If you do not go into deep theory, then graphs of gamma curves can be called the ratio of the incoming signal to the measured signal displayed by the monitor.

Gamma Measurement Image Set

Unfortunately, ideal displays do not exist, so any color on the screen is displayed with an error introduced by the LCD matrix. It is this error that we will measure. To prevent our measurements from being "spherical in a vacuum", all gamma curve plots have a reference curve drawn in black. Gamma 2.2, which is used in sRGB and Adobe RGB color spaces, is taken as the standard.

The examples of the graphs show that the curves we obtained do not always coincide with the reference ones. If the gamma curve passes below the reference one, it means that the halftones on such a display are underlit, they look darker than necessary. In this case, dark areas of the image can especially suffer - the details in them are lost. If the curve goes above the reference one, then the midtones are overexposed and the details in the light parts of the image are already lost.

There are also s-shaped and z-shaped gamma curves. In the first case, the image turns out to be more contrasting, while the details are lost both in the light parts and in the dark ones. In the second case, on the contrary, the contrast is underestimated, albeit with the benefit of detail. All cases of gamma mismatch are bad in their own way, because because of them the picture on the screen turns out to be changed compared to the original.

⇡#Conclusions

In order to distinguish a good screen from a bad one, you need to look at all the charts and graphs at once, one or a couple is not enough here.

With the brightness of white, everything is simple - the more it is, the brighter the display will be. Brightness at the level of 250 cd/m2 can be considered normal, and all values ​​above are good. With the brightness of black things are the opposite: the lower it is, the better. As for contrast, almost the same can be said about it as about white brightness: the higher the static contrast value, the better the display. Values ​​around 700:1 are good, and around 1000:1 are great. Note that AMOLED and OLED screens almost do not glow black - our device simply does not allow us to measure such small values. Accordingly, we consider their contrast ratio to be almost infinite, but in reality - if we arm ourselves with a more accurate device - we can get values ​​like 100,000,000:1.

With color gamut, things are a little more complicated. The principle "the more - the better" is no longer valid here. You should be guided by how well the color gamut triangle matches the sRGB color space. Displays that are completely ideal in this sense are practically not found in mobile devices. The optimum coverage is 90 to 110% sRGB, while it is highly desirable that the shape of the triangle is close to sRGB. Also on the color gamut graph, you should look at the location of the white point. The closer it is to the D65 reference point, the better the white balance of the display.

Another measure of white balance is color temperature. On a great monitor, it is 6,500 K for rich whites and hardly changes in different shades of gray. If the temperature is lower, then the screen will "yellow" the image. If higher - then "blue".

With gamma curves, everything is even simpler: the closer the measured curve is to the reference one, which we draw black on the graphs, the less errors the display matrix introduces into the image. We are well aware that it is not easy to remember all this at once. Therefore, we will refer to this material in future reviews. So you will always have information on how to read our charts at your fingertips.

If you notice an error, select it with the mouse and press CTRL+ENTER.

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TV screen brightness

Home > Settings > Brightness

Brightness (simplified) - equal to the ratio of luminous intensity to the area of ​​​​the luminous surface and is measured in candela per m2 or nits. 1 cd/m2 = 1 nit

Modern TVs have a declared screen brightness of 400-500 cd / m2 and even higher. Unless the manufacturers of CRT TVs are modestly silent about the brightness, because. due to technology limitations, it is difficult for them to obtain brightness above 150 cd / m2, and such characteristics will look pale against the background of LCD and plasma. However, this is sufficient in most cases. What does it say? On the one hand, that such TVs can be viewed at almost any reasonable brightness of natural or artificial lighting.

But there is another side. Too high brightness tires the eyes, especially if you watch a TV with a bright screen in low light or in complete darkness. So the viewer, who wants to preserve his vision, will first turn down the brightness.

The only area where such high brightness is required is when viewing 3D movies with shutter glasses, as even when open, LCD shutters absorb a noticeable amount of light.

By the way, a comfortable screen brightness is about 150-200 nits. And paragraphs 6.4, 6.5, 6.7 of SanPiN 2.2.2 / 2.4.1340-03 limit the brightness of objects that fall into the field of view when working with computers to a value of 200 cd / m2.

Thus, we can say that for any modern TVs, when buying, you can ignore the declared screen brightness. But when choosing LCD TVs, it is desirable to evaluate the uniformity of the backlight. This mainly applies to classic LCD TVs and LED TVs with side (edge ​​- Edge) backlighting. The best way to evaluate uniformity is to display a white box on the screen. Although in some cases the opposite is true, the unevenness is better seen on a black field.

The figure on the left shows a TV with a uniform backlight brightness, on the right - with a decrease in brightness from the center to the edges (the effect is exaggerated).



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LCD Display Design and Main Features of the Monitor - In the World of Monitors

The main structural element is a network of cells (1) filled with liquid crystals, a substance whose molecules can change their spatial orientation under the influence of an electric field. The control electronics (2) of the display receives a signal from the video input (3), depending on which the cell is either energized or not. Depending on the presence/absence of voltage, the liquid crystals are arranged in such a way that the polarizing film (4) stops transmitting the light of the backlight lamps (5) distributed by the special film (6), or, on the contrary, transmits it almost completely. The drawing on the screen forms a "mosaic" of many cells closed by a given value. Each pixel consists of three sub-pixels, which are provided with color filters for the primary colors red, green and blue, making it possible to output color images. TN+Film matrices use a film that increases the maximum viewing angles (7).

Main features of the monitor

Before you go to the store for a new display, you need to determine by what criteria to evaluate it. The concept of "quality image" consists of several objective parameters, the understanding of the essence and importance of which is necessary for a conscious choice. A small part of them can be gleaned from the passport data of the device, the user can evaluate some characteristics on his own, but the most important parameters can only be measured using special equipment - it is better to rely on monitor tests in this.

1. Screen size. The most understandable characteristic of the monitor. To date, models with a diagonal of 20-22 inches are universal for home use. Larger monitors are good for watching video, but will not be very comfortable to work with. Buying smaller models for most users simply makes no sense: even most 24-inch monitors can now be purchased for up to 10 thousand rubles.

2. Aspect ratio. The standard screen aspect ratio for modern monitors is 16:10. 4:3 displays are almost extinct. At the same time, the first models of monitors with a very controversial aspect ratio of 16:9 appeared. The resolution on their screens corresponds to the High Definition format. For example, a classic widescreen monitor with a diagonal of 24 inches has a resolution of 1920x1200 pixels, and a "newfangled" monitor has a resolution of 1920x1080 and, accordingly, its screen height is 120 pixels less. The only thing that justifies this loss is the ability to watch movies in HD without horizontal black bars around the edges.

3. Grain. Monitors that belong to adjacent categories by screen size often have the same resolution (for example, 20- and 22-inch displays have 1680x1050 pixels as standard). In such cases, the only advantage that a larger model has is a larger picture. The size of the image in pixels on a larger display does not exceed the size on a smaller one, moreover, on a monitor with a larger diagonal, in this case, the picture will be less clear due to the larger pixel size (which is called the grain).

Attention! Laptop screens come in a wide variety of screen size and resolution combinations. On sale you can find models with the same diagonal of the display, while the number of pixels on them will differ by one and a half times. In this case, before buying a device, you need to see both options "live", otherwise it is likely that the picture on the screen of the purchased laptop will not seem clear enough, or you will have to "break your eyes" when working with small interface elements at higher resolution.

4 Brightness. This parameter is measured in candelas per square meter (cd/sqm). For comfortable work with text documents and web surfing monitor brightness should not be less than 80 cd/sq. m., and for games and watching movies, only one recommendation can be given: the higher the brightness, the better. Contrary to possible fears, a monitor with “excessive” brightness will not hurt the eyes, since it can be lowered, but it will not work to increase the brightness beyond the maximum if the monitor “goes blind” on a bright sunny day. The brightness of the monitor is always indicated in its technical description, and these data can be trusted - in most cases they are not far from reality.

5. Contrast. Defined as the ratio of the brightness of the white color on the screen to the brightness of the black (see next parameter) and is written as a ratio (for example, 500:1). High contrast makes the image more “tangible” and “alive”, so its value cannot be overestimated. For a modern liquid crystal display, the contrast ratio is in the region of 400–500:1; for more “serious” models, this parameter can reach up to 700:1 and even higher. The minimum recommended contrast ratio for a home monitor is 300:1. Unlike brightness, a monitor's manufacturer's stated contrast ratio is not always accurate.

6. Depth of black. The liquid crystal matrix does not emit its own light and, regardless of whether it displays black or white, is illuminated by lamps of constant brightness. The disadvantage of this approach is that the closed pixels do not completely block the light and some of it gets out, turning black into dark gray. In bright daylight, this drawback may not be noticeable, but it can spoil the pleasure of watching a movie or a computer game at night. Monitor manufacturers do not provide specific data on the depth of black provided by their products. But in order to compare different displays, this parameter can be calculated independently, knowing the brightness and contrast of devices: just divide the first value by the second. For example, a display with a brightness of 200 cd / sq. m. and a contrast ratio of 400: 1, the brightness of black (or, as they say, a black point) will be 0.5 cd / sq. m is quite a lot for a modern display. On the other hand, a model with the same brightness and contrast ratio of 800:1 will have black pixels "shine" at a brightness of 0.25 cd/sq. m is a very good result.

7. Response time. The amount of time needed for an LCD cell to change its brightness from one set value to another. The response time is from several units to tens of milliseconds. With a long response time, fast moving objects on the screen turn out to be blurry, which is completely uncritical for working with text or static graphics, but greatly spoils the pleasure of a dynamic game or movie. To avoid this, the display response time should not exceed 8 ms, and 4-ms screens can minimize the effect of "blurring". You should not trust the value of the response time, which is indicated by the manufacturer in the description of the monitor. The point is not that the company can provide knowingly false information (this happens very rarely), but the difference in methods for measuring this parameter.

Traditionally, the transition time of a pixel from 10% to 90% brightness is measured, while the corresponding data is marked as BtW (Black to White - from black to white). But this technique is not objective: the matrix cell overcomes such a sharp transition in brightness at maximum speed, and the most common real situation in which it takes place is working with text - here the inertia of the display does not play a big role. In contrast, response time-sensitive images (movies, games) tend to be dominated by small changes in brightness. And they take much longer. To simulate these situations, the GtG (Grey to Gray) technique is used, the result of which is determined as the arithmetic average of the pixel transition time between several gray levels. The data obtained in this way, of course, is much closer to reality. But what method the monitor manufacturer used to obtain passport data is most often not reported. Therefore, it is better to rely on the results of objective tests carried out by experts, and, of course, when buying a monitor, check “by eye” whether the image on the screen is blurred when moving windows and playing dynamic video.

8. Viewing angles. One of the disadvantages of liquid crystal displays is the deterioration of the image when looking at the screen at an acute angle: the contrast drops and the color accuracy decreases. Small viewing angles make it impossible for several people to comfortably view the image on the monitor at the same time, and for one user they can create problems: on screens with a large diagonal, the picture along the edges of the display is always observed at a certain angle. A good value for viewing angles, which allows you to use the monitor without any special restrictions, is 160 degrees vertically and the same horizontally.

If you carefully study the technical characteristics of modern monitors, it turns out that almost all of them fit into this standard. However, in this case, the same trick is used as with measurement techniques. Initially, the maximum viewing angles were recorded at a level where the image contrast dropped to 10:1. But some manufacturers use a more "liberal" technique that allows the contrast to drop to 5:1. In addition, the measurement of contrast does not allow us to evaluate the distortion of color reproduction when changing the angle of view, and in most cases it is much more pronounced. Therefore, the data on viewing angles indicated by the developers are completely devoid of practical meaning. It is necessary either to evaluate the viewing angles "by eye" - when examining the display on your own, or be guided by professional tests.

9. Color gamut. Represents the range of colors that the monitor can display. Typically, the manufacturer does not provide such data, but they can be gleaned from tests. The number of shades that a monitor can reproduce is measured as a percentage of some color space, usually sRGB. Most modern displays are capable of reproducing 105-110% of the sRGB color gamut, and this is quite enough. Only users who work professionally with graphics, it makes sense to focus on the AdobeRGB standard, which involves the transfer of more saturated shades. The best monitors have color gamuts approaching or even exceeding AdobeRGB. But keep in mind: to correctly display sRGB graphics on such a monitor, you need to use programs that support color management. Not all applications have this capability, so the user will occasionally encounter color distortion.

10. Color accuracy. This is the most important display setting for all tasks related to photo processing and color computer graphics. It is not indicated in the technical documentation for monitors, only professionals can subjectively assess the accuracy of color reproduction, and then armed with specialized equipment, therefore, again, monitor tests are the only source of reliable information. Two main indicators can appear in them: ΔE and a graph of gamma curves.

The ΔE parameter shows the arithmetic mean deviation of all colors from the standard. Normal color reproduction for most users will be at ΔE less than 5, professionals need monitors with ΔE ranging from 0 to 1.5.

However, ΔE is not a universal indicator: it characterizes color reproduction from the standpoint of the sRGB standard, therefore it is not suitable for evaluating monitors with a wide color gamut. Gamma curve graphs are more informative: functions that display the dependence of the brightness of a pixel on the signal level at the video input, calculated separately for red, blue and green colors. By the divergence of these lines, one can determine the strength of color rendering distortions, as well as the conditions under which they appear. For example, if the curves are approximately the same along the entire length, except for the upper section, then the colors will be violated only in the light areas of the image. The shape of the gamma curves allows you to judge the contrast of the picture and is characterized by a certain number. Ideally, the lines should be smoothly "failed". This corresponds to a gamma of 2.2 for personal computers and 1.8 for Apple Mac computers. If the curves are lowered more (the “gamma number” is greater than 2.2), then the image will be too dark, soft shades will merge with each other. If the measured curves are higher than ideal, the picture on the screen will be whitish and "inexpressive".

11. Illumination uniformity. As well as the lack of black depth, the uneven illumination of the matrix will be clearly visible when working in the dark. When choosing a monitor in a store, you are unlikely to be allowed to turn off the light, so again you will have to study the test results. In most cases, experts indicate the average value of the deviation of the brightness of the backlight of various parts of the screen from the average brightness of the matrix or the brightness in the center of the image. At best, this indicator should not exceed 5-10%, a deviation of 10-15% is acceptable. If the value is greater, the differences in brightness on the screen will create great inconvenience. Keep in mind that displays that do not have sufficient black depth are at risk for backlight unevenness.

The ComputerPress test laboratory tested six LCD monitors with a screen resolution of 1920x1200: Acer P243W, BenQ FP241WZ, LG FLATRON L245WP, NEC MultiSync LCD2470WNX, SAMSUNG SyncMaster 245BW and XEROX XM7-24w.

This test is dedicated to LCD-monitors with a diagonal of 24 inches. Today, the choice of models with a similar diagonal is small. Few manufacturers offer more than two models with this screen size, and most have only one 24-inch model in their product line. Also note that the line between high-end consumer and professional displays has recently begun to blur.

We chose six popular widescreen 24-inch models for testing, the price of which does not exceed $ 1,500. We did not put forward any other conditions, so models with both an inexpensive TN matrix type and a more expensive MVA (PVA) participated in the tests for accurate display of colors.

We have already considered the advantages of widescreen models compared to conventional monitors in previous articles on this topic. Here we only note that at the moment a diagonal of 24 inches is perhaps the maximum suitable for home use and it makes no sense to purchase a monitor with a larger diagonal.

Another advantage of 24-inch models is support for Full HD resolution, which allows them to be used not only as a PC monitor, but also as a display device for other HD video sources such as a player and game consoles. Considering that a computer monitor can be used not only for its intended purpose, some manufacturers equip these devices with additional interfaces such as HDMI, S-Video, composite and component video connectors, which makes monitors even more functional.

Specifications for the tested monitors are shown in the table.

LCD Test Methodology

Required hardware and software

Equipment:

• a computer;
• GretagMacbeth Eye-One Pro spectrophotometer;
• photosensor;
• digital oscilloscope BORDO 211A (PCI-board), installed in a computer.
• Software:
• operating system Microsoft Windows XP Professional SP2;
• Eye-One Match 3.0.6 software;
• ProfileMaker Pro 5.0.5 software;
• program CHROMIX ColorThink 2.1.2;
• program Adobe Photoshop CS2;
• a utility for measuring pixel response time (proprietary development of the ComputerPress test laboratory);
• driver and utility for digital oscilloscope BORDO 211A.

General provisions:

• all monitors tested at operating resolution at 60 Hz refresh rate and maximum color depth;
• testing of all monitors is carried out using the same computer with the installed operating system Windows XP Professional SP2;
• the monitor is connected to the computer via a digital interface (DVI), and if it is not available, via an analog interface;
• measurements are taken in a darkened room to avoid the influence of external light;
• before testing, all monitors are calibrated and profiled;
• During testing, the following characteristics of monitors are measured:
• maximum brightness;
• uneven brightness;
• monitor contrast;
• color unevenness;
• color gamut;
• color accuracy;
• pixel response time according to the ComputerPress method.

Monitor Calibration and Profiling

Monitors are calibrated and profiled using a GretagMacbeth Eye-One Pro spectrophotometer, complete with Eye-One Match 3.0.6 software.

Calibrating and profiling a monitor are two different processes that run one after the other. The created monitor profile is only used to display its color gamut. Only certain programs that support this feature (such as Adobe Photoshop CS2) can work with monitor profiles. Packages like Microsoft Office do not support or use monitor profiles.

In order to calibrate the monitor and create its profile, you need to run the Eye-One Match 3.0.6 utility and select the monitor as the profiling device.

Monitors are calibrated in Advanced mode.

All monitors are calibrated with the following settings:

• White Point (white point) - 6500 K;
• Gamma - 2.2;
• Brightness - 120 cd/m 2 .

Monitor calibration adjusts monitor contrast, color temperature (by adjusting the R, G, B channels), and brightness.

When calibrating and creating a monitor profile, the spectrophotometer is positioned at the center point of the monitor.

The color field measurement file is stored in the profile. Additionally, the minimum and maximum brightness values ​​are measured.

Measuring the maximum brightness of a monitor

Measurement of the maximum brightness of the monitor is performed according to the calibration procedure described above, but all the initial steps - up to the stage of calibrating the brightness of the monitor - are skipped. Regardless of the set value of the desired brightness, the brightness, contrast and color channels of the monitor are set to 100%, and the measurement result is fixed.

Measuring brightness and color unevenness

After calibrating and creating a monitor profile based on measurements at the center point of the monitor, measurements of brightness and color patterns are made, which are used in the calculation of the profile, at eight more points:

• upper left corner (Left Up Point, LUP);
• left center (Left Center Point, LCP);
• lower left corner (Left Down Point, LDP);
• the central upper point (Center Up Point, CUP);
• central lower point (Center Down Point, CDP);
• upper right corner (Right Up Point, RUP);
• right center (Right Center Point, RCP);
• lower right corner (Right Down Point, RDP).

To do this, use the measurement technique described above at the central point, but skip all the initial steps before measuring the brightness of the monitor. When measuring the brightness of the monitor, the brightness level does not change.

The measurement results (maximum and minimum brightness) are recorded for each point. Profiles are saved with indication of the measurement point.

The resulting profiles make it possible to calculate the brightness unevenness, color unevenness, and contrast unevenness across the screen field when the central point is set to a color temperature of 6500 K and a brightness of 120 cd/m 2 .

Calculation of average brightness and unevenness of brightness, contrast and unevenness of contrast

Contrast calculation FROM at each point of the monitor is produced as the ratio of the maximum brightness to the minimum:

Calculation of the average brightness and contrast is based on the measured values ​​of maximum and minimum brightness at nine points on the monitor:

The calculation of the unevenness of brightness and contrast is calculated as the standard deviation for nine points of the screen:

The smaller the standard deviation in brightness, the better.

Color unevenness calculation

Calculation of unevenness of color is made according to the saved profiles for each of nine points of the monitor. The profiles are processed by ProfileMaker Pro 5.0.5, which uses the MeasureTool 5.0 utility and the Comparing tool. This tool compares the measurement results in Lab color coordinates for each color field of the monitor's center point profile with the remaining eight points. Thus, a total of eight report files are created.

From each report file, the Delta E value, averaged over all color fields, is applied, which characterizes the color difference (color mismatch) between the center point of the monitor and one of the eight extreme points. Next, the average (arithmetic mean) value of Delta E is calculated, which characterizes the color unevenness on the monitor screen. The lower the average value, the better.

Determining the color gamut of a monitor

A monitor profile created from the center point allows you to view its color gamut and compare it to other monitors or to the Adobe RGB color gamut of an ideal monitor that matches the Adobe RGB (1998) profile. For this, the CHROMIX ColorThink 2.1.2 utility is used. It also allows you to compare the color gamuts of different devices by their profiles in coordinate systems. Love and Xxy, both in 3D and 2D.

The larger the monitor's color gamut, the better.

Determining Color Accuracy

To determine the accuracy of color reproduction, the concept of an ideal monitor is introduced, which corresponds to the color gamut of Adobe RGB (1998). Since the Adobe RGB (1998) profile corresponds to a white point color temperature of 6500 K (D65), the comparison of the color gamuts of the ideal and tested monitors is correct.

Color accuracy refers to the Delta E color difference between the color on the ideal monitor and the color on the monitor under test, averaged over multiple measured color fields.

As a template for measured color fields, the Monitor Testchart.txt template is used, which is attached to the Eye-One Match 3.0.6 program and is used to create a monitor profile.

Next, the profile is compared with the results of measurements of the monitor at the center point of the screen and with the AdobeRGB file. For comparison, ProfileMaker Pro 5.0.5 is used, which runs the MeasureTool 5.0 utility (Comparing tool).

After that, the measurement results in Lab color coordinates for each color field are compared, as well as the calculation of the average Delta E value for all color fields.

The lower the average Delta E value, the more accurate the color reproduction of the tested monitor.

Measurement of pixel switching time

To measure the pixel switching time, a photosensor and a BORDO 211A digital oscilloscope connected to a computer are used.

The photosensor is assembled on a Siemens BPX90 photodiode and an Analog Devices AD8604AR precision amplifier. The resistance of the photodiode shunt to obtain the desired sensitivity is 10 MΩ, and the amplifier is powered directly from the computer (an LC filter and a compensation stabilizer on the 7805 microcircuit are additionally used to dampen interference from the switching power supply).

The technique for measuring the pixel response time is similar to the Grey-To-Grey (GTG) technique, but does not repeat it completely, so the measurement results cannot be compared with the technical data given in the documentation. When measured according to the method below, it is indicated that we are talking about the pixel switching time according to the ComputerPress method (KP method).

When measuring with a special utility, a horizontal line one pixel wide is turned on or off. The line color (in grayscale) is set using the utility. The photosensor registers the time of changing the brightness of a pixel.

There are two monitor settings when measuring pixel switching time:

1. The contrast and brightness levels are set to maximum. Similarly, the level of all color channels (R, G, B) is set to 100%.
2. Measurements are made on a monitor calibrated as described above, i.e. the brightness level is 120 cd/m2 and the white point color temperature is 6500 K.

The measurement is performed at the working resolution of the monitor and a frame rate of 60 Hz.

During testing, the transition time between the following halftone states (in R-G-B coordinates) of a pixel is measured: 0-0-0, 100-100-100, 150-150-150, 200-200-200, 255-255-255. The measurement results are entered in a table. Each measurement is taken five times, and the average time for five measurements is taken as the switching time.

An important and most controversial point in the measurement is that when moving from a lower level to a longer one, the rise time of the pulse front is measured not from 0 to 100%, but from 0 to 90%. Similarly, when switching from a higher level to a lower one, the pulse front decay time is measured from 100 to 10%.

On fig. 1 shows typical cases of switching a pixel from a lower semitone to a higher one. In this case, it may well turn out that many manufacturers measure the rise time of the pulse front from 10 to 90%. Therefore, we once again emphasize that the values ​​of the pixel response time given in the article according to the KP method cannot be compared with the manufacturer's data.

Rice. 1. Measurement of the pixel response time using the KP method

In addition to calculating the pixel switching time between individual states using the KP method, a three-dimensional diagram of the pixel response time is built for each monitor.

After all possible transitions between different halftones have been measured, the average value of the pixel response time is calculated. To do this, the geometric mean time of transitions between all semitones is calculated. The value calculated in this way is the response time of the pixel according to the KP method.

Subjective assessment

Measurement of the above parameters of monitors allows you to compare models by individual characteristics. However, for an integral comparison of monitors, it is incorrect to rely only on the listed characteristics. In addition, each monitor has individual features that are sometimes impossible to measure, but at the same time cannot be ignored when choosing the best model. Non-measurable characteristics include monitor functionality, design, and a number of design features that ultimately affect the price of the device: multimedia capabilities, the presence of a USB hub, and the screen rotation (Pivot) function. The functionality of monitors is determined by the capabilities of the on-screen menu, the presence of quick keys for adjusting brightness and contrast, the ability to simultaneously connect the monitor to two system units with a choice of signal source, the number of supported color temperatures, the ability to save monitor settings in memory, etc.

Although all of the above monitor characteristics can only be evaluated and compared subjectively, they significantly affect the choice of a particular model.

Based on the measured characteristics and a subjective assessment of the advantages and disadvantages of each model, we chose the best monitor, as well as the optimal model.

Editor's Choice

Models were awarded the Editors' Choice sign BenQ FP241WZ and LG FLATRON L245WP, which demonstrated high functionality and good performance in objective tests.

Test participants

Acer P243W

Maximum brightness on a white field - 467.1 cd / m 2

Average brightness on a white field - 110.93 cd / m 2

Average brightness on a black field - 0.17 cd / m 2

Average contrast - 768.7

Average brightness deviation - 6.97 cd / m 2

Pixel response time (according to the KP method) - 5.2 ms

The Acer P243W monitor belongs to the updated line of LCD monitors of the same company. Its front panel is made of glossy black plastic, and the screen is covered with a high-contrast Crystalbrite optical filter. This filter has both advantages and disadvantages. The image on matrices with such a coating is clearer and more contrasting compared to the image on matrices not equipped with such a filter. However, the glossy coating of the matrix reflects everything in front of the display. Unfortunately, in a well-lit room, it is quite difficult to choose a position of the monitor in which nothing will be reflected in it.

The body of the monitor is quite thin. The stand is made of silvery plastic and allows you to adjust the position of the matrix in only one plane. The stand is detachable, allowing you to mount the monitor on a wall or other VESA-compatible stands. There are special holes on the rear panel for mounting the monitor on the wall.

The lower part of the front panel of the case is unusual - it is made in the form of a protruding triangle. In the center of it is the company logo, pointing upwards, which gives the monitor a special appeal and originality.

Here on the right is the monitor control panel containing four buttons. Two buttons are on-off and are made in the form of rocker keys. They are quite large and easy to press. These buttons are used to call the system menu and change settings in it. The power on/off button has an LED indicator directly above it. The last button is responsible for automatically setting the monitor with an analog connection.

The monitor's menu is no different from the menus in earlier models. It is convenient and quickly mastered. Of the features of the menu, we note the support of the Russian language.

The monitor has a full range of interfaces, including analog D-Sub input, digital DVI-D (with HDCP support) and HDMI. The rear panel also has a connector for a standard power cable and a Kensington Lock. Note that the HDMI connector is not placed very well - too close to the stand leg, as a result of which a standard HDMI cable cannot be plugged into the connector without first removing the stand leg. The lower part of the transport stand is removable.

By default, the monitor's brightness was set to 85% and the contrast to 50%. After calibrating the monitor to a brightness of 120 cd/m 2 , the settings were as follows: brightness was 14%, contrast was 50%, red was 80%, green was 69%, and blue was 69%. Note that when the contrast is increased above 50%, the light tints of the image merge with white. Therefore, the contrast setting should not exceed 50%.

The maximum brightness measured in the center of the screen was 467.1 cd/m 2 , which even slightly exceeds the value stated in the specification (400 cd/m 2 ).

The average deviation of brightness over the entire field of the display was 8.08 cd/m 2 . The brightest was the right center area of ​​the display, and the most dimly lit was its lower left corner.

On fig. Figure 2 shows the RGB curves and color gamut of the Acer P243W, as well as other parameters obtained during the monitor calibration process.

Rice. 2. Gamma curves and color gamut of the Acer P243W monitor

On fig. Figure 3 shows the gamma coverage of the Acer P243W monitor profile (solid surface) compared to the sRGB (grid) profile in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 3. Acer P243W monitor profile comparison (solid surface)

The color gamut of this monitor is quite traditional for models that use backlight lamps with a conventional phosphor. As can be seen from the figure, the color gamut almost completely exceeds the standard sRGB gamut and loses to it only in blue colors.

The maximum pixel response time according to the CP method corresponded to the transition from gray with parameters 50-50-50 to white and amounted to 13.7 ms. At the same time, the pixel response time measured by the CP method is 5.2 ms (Fig. 4).

Rice. 4. Pixel transition time from one
status to another for the monitor Acer P243W

The main advantage of the monitor is a rather high maximum possible brightness, which in our case even exceeded the declared value.

The main disadvantages of the Acer P243W, in our opinion, are not very large viewing angles and the creation of glare by the optical filter that covers the display. The Acer P243W monitor is based on a TN-matrix. And although the viewing angles are declared equal to 170 and 160 °, in fact they are less. Traditionally, for this type of matrices, there is not enough vertical viewing angle, so when viewed from below, the image darkens.

The high-speed characteristics of the monitor allow it to be used for watching dynamic videos and games, as the monitor matrix implements the response time compensation technology.

BenQ FP241WZ

Maximum brightness on a white field - 428 cd / m 2

Average brightness on a white field - 116.11 cd / m 2

Average brightness on a black field - 0.19 cd / m 2

Average contrast - 685.8

The average brightness deviation is 8.81 cd / m 2

Average Delta E - 0.99

Pixel response time (according to the KP method) - 9.2 ms

The BenQ FP241WZ monitor is unique in our testing as it provides the user with the new PerfectMotion response time reduction system. which was previously called BFI (Black Frame Insertion). PerfectMotion technology allows, according to the manufacturer, to get a clearer and more dynamic image on the screen. Its main feature is that a black segment is inserted between the frames, due to which the high dynamics of CRT monitors is achieved. In addition, PerfectMotion avoids artifacts and flare, which are more or less present on monitors with response time compensation technology. This function is activated by a special button. Its setting allows changing the parameter from 0 to 3.

At the same time, the monitor matrix, made using A-MVA technology, supports RTC response time compensation technology. From a designer's point of view, the BenQ FP241WZ monitor is practically no different from its predecessors. It is made in a black case, only the front panel around the display is painted in silver. The monitor menu buttons are located on the right side of the case.

The monitor menu is implemented using nine buttons, one of which is used to turn on the power. The menu is quite convenient, with all the necessary functions, the Russian interface is supported.

The stand is very functional and allows for height and tilt adjustment. In addition, the mode of rotating the panel to portrait mode is supported. The monitor can also be rotated left and right, thanks to the rotating mount.

The monitor is equipped with a full set of interfaces. In addition to traditional inputs (15-pin D-Sub and DVI-D), several analog video inputs are available, including S-Video, RCA composite video, YUV component video, and HDCP-enabled HDMI.

Among other functional features of the BenQ FP241WZ, we note the presence of a three-port USB hub. On the top of the monitor is one USB port for more convenient webcam connection. The remaining two ports are located on the left side of the case.

The monitor can be mounted on a wall or other VESA-compatible stand.

After calibrating the BenQ FP241WZ monitor to a brightness of 120 cd/m2, the monitor settings were as follows: brightness was 4%, contrast was 50%, red was 51%, green was 50%, and blue was 48%. By default, brightness was set to 90% and contrast to 50%.

The maximum brightness measured at the center of the screen was 428 cd/m 2 , which corresponds to 85.6% of the specification (500 cd/m 2 ).

The average brightness deviation over the entire display field was 8.81 cd/m 2 . In our case, the right center area of ​​the display turned out to be the brightest, and its lower left corner was the most dimly lit.

On fig. Figure 5 shows the RGB curves and color gamut of the BenQ FP241WZ, as well as other parameters obtained during the monitor calibration process.

Rice. 5. Gamma curves and color gamut of the BenQ FP241WZ monitor

On fig. Figure 6 shows the gamma coverage of the BenQ FP241WZ monitor profile (solid surface) compared to the sRGB (grid) profile in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 6. BenQ FP241WZ monitor profile comparison (solid surface)
with sRGB (grid) profile in L*a*b* color coordinate system
at a color temperature of 6500 K (white point)

The maximum pixel response time according to the CP method with the PerfectMotion technology turned off corresponded to the transition from white to black and amounted to 12.7 ms. At the same time, the pixel response time measured by the CP method is 9.2 ms (Fig. 7).

Rice. 7. Pixel response time of BenQ FP241WZ monitor
when Perfect Motion is off

Pixel response time was not measured with PerfectMotion enabled. As the monitor inserts black frames, the brightness curve on the oscilloscope becomes "saw" due to backlight flicker. It is rather difficult to estimate how much the time of “ignition” or “extinguishment” of a pixel has decreased. For example, let's look at two time graphs of the transition of a pixel from black to white with the PerfectMotion function disabled (Fig. 8) and enabled (Fig. 9).

Rice. 8. Graph of the transition of a pixel from black to white on a monitor
BenQ FP241WZ with PerfectMotion Disabled

Rice. 9. Graph of the transition of a pixel from black to white on a monitor
BenQ FP241WZ with PerfectMotion enabled

By increasing the PerfectMotion parameter from 1 to 3, you can achieve a decrease in the reaction time of the backlight, but it should be understood that this function should not be enabled in all cases. For example, in a static picture, it is better to turn it off, since with an increase in the PerfectMotion parameter, the overall brightness of the backlight decreases. Of course, it can be increased using the on-screen menu, but what if the monitor is accurately calibrated to some color temperature and when the brightness setting is reduced, almost all other parameters “float”?

The advantages of this monitor include uniform illumination, fast pixel response time, new technologies that reduce the afterglow time of pixels, large viewing angles, good color reproduction and, of course, very high functionality.

It is almost impossible to find fault with the monitor, we only note a not very high contrast ratio. The monitor shows insufficiently saturated color, which is why this indicator is not so high.

In general, the BenQ FP241WZ monitor showed good results in almost all tests, and in addition, it turned out to be the most functional model, which allowed us to mark it with the Editor's Choice sign.

LG FLATRON L245WP

Maximum brightness on a white field - 397 cd / m 2

Average brightness on a white field - 110.49 cd / m 2

Average brightness on a black field - 0.12 cd / m 2

Average contrast - 1005

Average brightness deviation - 6.10 cd / m 2

Average Delta E - 1.19

Pixel response time (according to the KP method) - 7.6 ms

LG Electronics is positioning the LG FLATRON L245WP for graphics processing, design and Full HD video viewing. The monitor uses a Premium MVA matrix manufactured by AU Optronics.

The monitor has an elegant design, so it will successfully fit into any interior. Its body is black and the stand is made of aluminum. The stand of the device allows you to adjust the tilt and height, as well as rotate the screen around the axis.

The OSD setup buttons are located on the bottom of the display and are grouped on the left side of the display. In addition to the power on / off button, which is also located on the lower end of the display, but on the right, there are seven buttons that are used to call, control and configure the monitor settings. Some of them act as shortcut buttons when the user is not in the monitor menu. So, the OK / AUTO key performs the function of auto-tuning with an analog connection and confirmation when making any changes in the monitor menu, the INPUT key switches sources when several video signals are connected at the same time, the PIP key is combined and serves to call the PIP (Picture-In-Picture ).

The power indicator is located in the lower right corner of the monitor's bezel and illuminates blue when the monitor is on and amber when the monitor is in standby mode. Note that the monitor menu functions allow you to turn off the button backlight.

The menu structure almost completely repeats the structure that was implemented in earlier models, but its functions are somewhat different from the previous ones. For example, when connected via a digital interface (we believe that this is the only way a monitor with a similar diagonal should be connected), when the built-in color temperatures (9300 and 6500 K) are selected, no settings related to displaying the image are available to the user, when choosing the sRGB mode, the user can change only one parameter - brightness. Only when choosing a custom mode, access to all settings is opened - brightness, contrast and manual adjustment of the color palette by color components.

Since the monitor is equipped with the PIP (Picture-In-Picture) function, its settings are also implemented in the menu. There are two options for its operation: displaying two windows side by side, that is, the monitor screen is divided in half and the image from the first video source is displayed on one half, and the image from the second is displayed on the second, and the image from the second source is displayed in a small window. In the second case, one more setting is available to the user - the choice of the position of the window in which the picture will be displayed. There are four display options - in each corner of the monitor. Note that the monitor also has a scaling function that allows, when using a lower resolution, to display the picture both in one-to-one mode and stretch it to the entire display area.

Other monitor menu options - OSD language selection (several languages ​​are provided, including Russian), factory reset, menu lock (child protection), menu position adjustment, etc.

The monitor is equipped with D-Sub, HDMI interfaces with support for HDCP digital data transmission protection protocol and composite video and audio inputs. The presence of HDMI (High-Definition Multimedia Interface) provides fast connection of consumer video devices, including HD-DVD-, Blue-ray-drives and game consoles.

With two USB 2.0 connectors, users can connect various USB devices such as keyboards, mice, and flash drives through the monitor. The monitor also has an audio output (standard 3.5mm mini-jack), which allows you to connect headphones or external speakers that can be attached to the bottom of the monitor. External speakers are not included with the monitor and are sold separately. By the way, an additional power connector is provided on the back of the monitor to connect speakers.

Note that in sRGB mode, the monitor is indeed very well calibrated (Fig. 10). In addition, when this mode is selected in the menu, the change of all parameters is blocked, with the exception of one and only - brightness. It was in this mode that the LG FLATRON L245WP monitor was tested. To achieve the desired brightness level of 120 cd/m 2 , the brightness level was reduced to 12%.

Rice. 10. Gamma curves and color gamut of LG FLATRON L245WP monitor

The maximum brightness measured at the center of the screen was 397 cd/m 2 , which is 79.4% of the specification value (500 cd/m 2 ).

The average deviation of brightness over the entire field of the display was 6.1 cd/m 2 . The brightest was the right central area of ​​the display, and the most dimly lit - its lower left corner.

On fig. Figure 10 shows the RGB curves and color gamut of the LG FLATRON L245WP, as well as other parameters obtained during the monitor calibration process. It can be seen from the figure that there is a complete correspondence between the desired and observed color temperatures. RGB-curves of the monitor look good, only in one place there is a noticeable blockage.

On fig. Figure 11 shows the gamma coverage of the LG FLATRON L245WP monitor profile (solid surface) compared to the sRGB (grid) profile in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 11. LG FLATRON L245WP monitor profile comparison (solid surface)
with sRGB (grid) profile in L*a*b* color coordinate system
at a color temperature of 6500 K (white point)

As can be seen from fig. 11, the color gamut almost completely overlaps the standard sRGB gamut and loses to it in blue and slightly in green colors, but significantly exceeds it in red.

The maximum pixel response time according to the CP method corresponded to the transition from black to white and amounted to 12.2 ms. At the same time, the pixel response time measured by the CP method turned out to be 7.6 ms (Fig. 12).

Rice. 12. Pixel transition time from one state
to another monitor LG FLATRON L245WP

The advantages of the monitor include very high-quality color reproduction, generally acceptable response time of the matrix, which is equipped with response time compensation technology, which allows the monitor to be used for watching dynamic video and games, rich black color and, as a result, a high contrast ratio, as well as the presence of an interface HDMI.

MVA-matrices are distinguished not only by good viewing angles, but also by a large black depth and high contrast. Thanks to this, it is very comfortable to work with texts on such monitors, and the LG FLATRON L245WP model is no exception.

Among the shortcomings of the LG FLATRON L245WP, we note the not very uniform backlight of the display.

The indicators demonstrated in the tests, as well as a good design, a functional stand and the presence of additional interfaces, allowed us to mark this monitor with the Editor's Choice sign.

NEC MultiSync LCD2470WNX

Maximum brightness on a white field - 486.9 cd / m 2

Average brightness on a white field - 121.96 cd / m 2

Average brightness on a black field - 0.20 cd / m 2

Average contrast - 769.8

The average brightness deviation is 7.51 cd / m 2

Average Delta E - 1.50

Pixel response time (according to the KP method) - 8.3 ms

NEC Display Solutions has added a new 24" widescreen LCD monitor, the LCD2470WNX, to its MultiSync 70 lineup. It is designed primarily for professional applications and meets the needs of the most demanding users. The manufacturer also recommends using it in all cases where it is not possible to use dual-screen solutions, for example, due to limited space on the desktop.

The monitor has a black plastic housing with a silver bezel around the matrix.

The monitor stand is very functional and allows you to adjust the height of the matrix relative to the table, rotate about the vertical axis and rotate the matrix left and right thanks to the rotating base of the stand. In addition, there is a swivel mechanism for working with the display in portrait mode.

The power button is located on the front panel, and all other buttons are located on the right side of the device. The monitor menu, its structure and functions are quite traditional for NEC monitors. You can adjust the contrast and brightness of the image and set the color temperature (5400, 6500, 7500 and 9300 K) in the monitor's OSD menu. The monitor supports sRGB mode and custom color palette setting by color channels.

The color adjustment system allows you to choose from six color balance settings. Proprietary NaViSet software allows you to adjust monitor settings without resorting to the on-screen menu. The FullScan function is responsible for using the entire screen area at almost any resolution. IPM technology integrates measures taken by the developers to reduce the monitor's power consumption.

The monitor provides for the installation of several scaling methods. It is possible to enable or disable the Hot Keys. When this function is enabled, brightness and contrast can be adjusted directly without going through the menu.

The monitor is equipped with analog (D-Sub) and digital (DVI-D) interfaces, which are located on the rear panel. On the back side of the stand there is a fastening for the interface wire and the power wire. It is also worth noting that the monitor supports HDCP digital content protection technology.

After calibrating the NEC MultiSync LCD2470WNX monitor to a brightness of 120 cd/m2, the monitor settings were as follows: brightness was 43%, contrast was 50%, red was 84.7%, green was 89.9%, and blue was 79.2%. . By default, the brightness in the monitor was set to 100% and the contrast to 50%.

The maximum brightness measured at the center of the screen was 486.9 cd/m 2 , which is 97.38% of the specification value (500 cd/m 2 ).

The average deviation of brightness over the entire field of the display was 7.51 cd/m 2 . The brightest was the right central area of ​​the display, and the most dimly lit was its upper left corner.

On fig. Figure 13 shows the RGB curves and gamut of the NEC MultiSync LCD2470WNX, as well as other parameters obtained during the monitor calibration process.

Rice. 13. Gamma curves and color gamut of the NEC MultiSync LCD2470WNX monitor

On fig. Figure 14 shows the gamma coverage of the NEC MultiSync LCD2470WNX monitor profile (solid surface) compared to the sRGB profile (grid) in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 14. NEC MultiSync LCD2470WNX Monitor Profile Comparison
system L * a * b * at a color temperature of 6500 K (white point)

The maximum pixel response time according to the CP method corresponded to the transition from black to gray with parameters 150-150-150 and amounted to 12.2 ms. At the same time, the pixel response time measured by the CP method turned out to be 8.3 ms (Fig. 15).

Rice. 15. Pixel transition time from one state
to another monitor NEC MultiSync LCD2470WNX

The advantages of the monitor include high display brightness and good backlight quality (which is ensured by color uniformity across the entire field) and color reproduction.

The high-speed performance of the matrix allows you to use the display for watching videos and games.

Among the shortcomings of the monitor, we note a greatly overpriced price for it on the Russian market.

SAMSUNG SyncMaster 245B

Maximum brightness on a white field - 388.2 cd / m 2

Average brightness on a white field - 113.59 cd / m 2

Average brightness on a black field - 0.22 cd / m 2

Average contrast - 886.6

The average brightness deviation is 6.75 cd / m 2

Average Delta E - 2.78

Pixel response time (according to the KP method) - 8.6 ms

Like most junior models, SAMSUNG SyncMaster 245B is made of black plastic. The monitor stand provides, in addition to tilt, the matrix adjustment in height and its rotation to the right and left by 360 °. If necessary, the stand can be removed and replaced with a standard VESA-compatible bracket.

At the bottom of the front panel there are five buttons, one of which, with a light diode, is responsible for turning the monitor power on and off. One of the buttons is dual and serves, depending on where the user is - in the monitor menu or not, to call up quick monitor settings, including setting brightness and contrast, or to call the Magic Brigth 2 function.

Quick access is provided to switching MagicBright modes, adjusting brightness, switching inputs and auto-tuning to a signal.

Traditionally, for many models of monitors from this company, the SAMSUNG SyncMaster 245B implements the proprietary functions of MagicTune and Magic Brigth 2. The latter has six preset monitor settings: Text, Internet, Sports, Movies, Games, and user mode . With this feature, the user can easily and quickly adjust the optimal levels of brightness and contrast by simply selecting one of the preset modes.

The menu is quite common for SAMSUNG monitors, which is simple and convenient. The set of settings is typical for mid-range monitors. The OSD settings can be changed programmatically using the MagicTune utility, if desired, without using the control buttons on the front edge of the monitor.

Of the interfaces on the rear panel of the SAMSUNG SyncMaster 245B, analog D-Sub and digital DVI-D are implemented. Note that the monitor is not equipped with speakers, however, it is possible to connect them directly to the monitor. For this purpose, there is a power connector for connecting a special speaker unit, as well as appropriate fasteners.

After calibrating the SAMSUNG SyncMaster 245B to 120 cd/m2, the monitor settings were as follows: brightness was 23%, contrast was 75%, red was 45%, green was 50%, and blue was 41%. By default, the brightness in the monitor was set to 100% and the contrast to 75%.

The maximum brightness measured at the center of the screen was 388.2 cd/m 2 , which is 97.05% of the specification value (400 cd/m 2 ).

The average deviation of brightness over the entire field of the display was 6.75 cd/m 2 . Traditionally, the center of the display has become the brightest area, and its lower left corner has become the most dimly lit.

On fig. Figure 16 shows the RGB curves and gamut of the SAMSUNG SyncMaster 245B, as well as other parameters obtained during monitor calibration.

Rice. 16. Gamma curves and color gamut of the monitor SAMSUNG SyncMaster 245B

On fig. Figure 17 shows the gamma coverage of the SAMSUNG SyncMaster 245BW monitor profile (solid surface) compared to the sRGB (grid) profile in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 17. SAMSUNG SyncMaster 245B Monitor Profile Comparison
(solid surface) with sRGB profile (grid) in color coordinate system
L*a*b* at 6500K color temperature (white point)

This monitor color gamut is quite common for monitors with a TN-matrix. There is a slight increase compared to the sRGB standard in the green and red areas, with a slight loss in the blue area.

The maximum pixel response time according to the CP method corresponded to the transition from gray with parameters 50-50-50 to gray with parameters 200-200-200 and amounted to 21.4 ms. In this case, the pixel response time measured by the CP method was 8.6 ms (Fig. 18).

Rice. 18. Pixel transition time from one state
to another monitor SAMSUNG SyncMaster 245B

The advantages of this monitor include a high level of contrast (the result even exceeded the declared value), good color reproduction and a functional stand.

Among the shortcomings, we traditionally mention a not very large horizontal viewing angle, which is associated with the panel production technology, and too long, in our opinion, the response time of the matrix.

The monitor matrix is ​​made using TN technology without response time compensation and is notable for its low cost. Therefore, this monitor cannot be recommended for color and image processing users. In general, the SyncMaster 245B monitor is not bad and is quite well configured. At the same time, it is significantly cheaper than its competitors based on other types of matrices.

In conclusion, we note that the brightness of the monitor is regulated by modulating the power supply of the backlight lamps at a frequency of 180 Hz. When measuring the response time of a pixel, this flicker made it quite difficult to correctly measure this parameter.

XEROX XM7-24w

Maximum brightness on a white field - 350.2 cd / m 2

Average brightness on a white field - 112.09 cd / m 2

Average brightness on a black field - 0.33 cd / m 2

Average contrast - 450.7

Average brightness deviation - 6.56 cd / m 2

Average Delta E - 2.04

Pixel response time (according to the KP method) - 4.8 ms

The XEROX XM7-24w monitor has expanded the well-known XEROX XM7 series. This line includes four large-format models with different diagonal sizes - from 19 to 24 inches. The model in question is the oldest in the line. It is aimed at corporate and home users.

Looking ahead, we note that this is the only multimedia model that participated in testing. The speakers, as in the younger models of the series, are hidden inside the case. A cursory glance at the monitor does not tell that it is equipped with speakers. Their location, in our opinion, is quite good - it allowed the manufacturer to give the monitor a more aesthetic appearance due to the narrow bezels around the display.

The XEROX XM7-24w model has traditional design for XEROX monitors. Their main distinguishing feature is the XShield protective coating, which consists of a special glass that protects the matrix from mechanical damage, and an anti-reflective coating. The menu control buttons are located at the bottom of the front panel.

The monitor menu provides the user with traditional settings. The menu supports several languages, including Russian, although some items have grammatical errors, while others are not translated at all. Therefore, we recommend that you still choose English for the interface.

The stand is not very functional and only allows you to adjust the angle of the monitor. This model has no height adjustment.

The XInput function allows you to connect the XEROX XM7-24w monitor simultaneously to three external devices thanks to the presence of a digital (DVI-D) and two analog (two D-Sub) connectors. You can change the video signal source by simply pressing a button, sequentially displaying an image from a game console, PC or laptop, which greatly simplifies the work with external devices. True, it is worth noting that among the monitor interfaces there are two analog connectors, which looks a little strange with such a diagonal size and resolution.

After calibrating the XEROX XM7-22w monitor to a brightness of 120 cd/m2, the monitor settings were as follows: brightness was 6%, contrast was 78%, red was 52%, green was 49%, and blue was 45%. By default, the monitor's brightness was set to 100% and the contrast to 50%.

The maximum brightness measured at the center of the screen was 350.2 cd/m 2 , which is 87.55% of the specification value (400 cd/m 2 ).

The average deviation of brightness over the entire field of the display was 6.56 cd/m 2 . Traditionally, the center of the display has become the brightest area, and its lower right corner has become the most dimly lit.

On fig. Figure 19 shows the XEROX XM7-24w RGB curves and gamut, as well as other parameters obtained during monitor calibration. The figure shows that this monitor has balanced RGB curves and displays a color gamut close to the sRGB standard. A complaint can be caused by a very high level of brightness in the black field at the center point of the display, which was about 1.

Rice. 19. Gamma curves and color gamut of XEROX XM7-24w monitor

On fig. 20 shows the gamma coverage of the XEROX XM7-24w monitor profile (solid surface) compared to the sRGB profile (grid) in the L*a*b* color coordinate system at a color temperature of 6500 K (white point).

Rice. 20. XEROX XM7-24w Monitor Profile Comparison
(solid surface) with sRGB (grid) profile in color coordinate
system L * a * b * at a color temperature of 6500 K (white point)

The maximum pixel response time according to the CP method corresponded to the transition from gray with parameters 50-50-50 to white and amounted to 18.9 ms. In this case, the pixel response time measured by the CP method was 4.8 ms (Fig. 21).

When buying a computer, it often happens that the monitor is chosen according to the residual principle - for which there is enough money left over from buying the system unit. There is some sense in this. Monitor performance is not affected by computer performance. But it should be understood that a cheap monitor with a low maximum resolution, a “blurred” image and poor color reproduction can negate the advantages of a top-end video card. A flickering backlight will lead to rapid fatigue and may adversely affect vision. So saving on the monitor can "go sideways", especially if the computer is supposed to be used often and a lot. Therefore, it is better to take the choice of a monitor with all responsibility, choosing it in accordance with the tasks.

The main influence on the price of the monitor is its diagonal size. But even among monitors of the same size, prices can vary by an order of magnitude, depending on other characteristics. It should be understood that many characteristics of monitors are important to some users and completely uninteresting to others. Knowing what characteristics are required for specific tasks, you can make the right choice by choosing a good monitor at the best price.

Depending on the purpose, it is customary to distinguish four groups from cheap to expensive models of a similar size: office, multimedia, gaming and professional.

Office monitors are designed to work with office programs. The requirements for such monitors are minimal and aimed at reducing fatigue during prolonged work: sufficient brightness, contrast and high-quality backlighting.

For multimedia monitors, the characteristics that provide a spectacular “picture” come to the fore. Good color reproduction, large diagonal, ultra-wide (Ultrawide) format distinguish these monitors from the rest.

Gaming monitors are monitors with a high maximum resolution, high refresh rate, and low response time. Here, color reproduction can be sacrificed for high-quality reproduction of dynamic scenes. Gaming monitors are usually widescreen. Ultrawide and curved monitors are also often marketed as gaming monitors.

The monitors of professional designers, photographers and artists must provide maximum color depth and color reproduction. Also desirable is a large maximum resolution, a small pixel size (this will ensure image clarity) and advanced calibration settings.

Monitor specifications.

Size (diagonal) monitor is its main characteristic, primarily determining its price and attractiveness to the user. Diagonal size is measured. The wider the monitor in terms of aspect ratio, the smaller the area of ​​​​the visible area with the same diagonal.
The screen diagonal varies from 18 inches to 55 and above. In general, the larger the diagonal, the better: more information is placed on the monitor, the effect of presence in games and when watching videos is higher.
Unfortunately, as the diagonal grows, the price grows exponentially. Therefore, recently workstations with two or more monitors have become increasingly popular: many modern video cards allow you to connect multiple monitors, which allows you to significantly increase the area of ​​\u200b\u200bthe desktop at a minimal price.

Maximum resolution.
Screen resolution is the number of pixels - dots that make up the image in width and height. The higher the maximum resolution, the clearer the image and the more information perceived by the eye is placed on the screen.

Keep in mind that the maximum resolution for each monitor is optimal - at this resolution, each pixel corresponds to one LCD element. You should not work with a monitor at a resolution lower than the maximum - this will either reduce the visible area (a black frame is formed), or each pixel will consist of several LCD elements, and it may turn out that some pixels will become larger than others (the image will begin to be noticeably distorted) .

The maximum resolution should match the size of the monitor: if it is not enough, the images will be grainy, if the resolution is too high, text and objects will become too small. To determine if the maximum resolution matches the size, use the value ppi - pixel density. PPI (Pixels Per Inc - "pixels per inch") is equal to the number of pixels per inch of the monitor. Text and modern objects operating systems configured for monitors with 96 ppi, therefore, in order to preserve the clarity of text and small elements, it is desirable that the ppi of the monitor be at least 90-100. If the monitor's dpi is much less than 90 (75 or less), images will become grainy. For watching videos and some games, this is not so important, but for work such a monitor will already be uncomfortable.

The maximum resolution of the monitor must be supported by the graphics card.
When replacing a monitor with a larger one, you should also remember that increasing the resolution also increases the load on the video card.

Aspect ratio (format) refers to the ratio of screen width to height. Old monitors had a ratio of 5:4 and 4:3, these are still on sale now and are usually used for office tasks - it is most convenient to work with “paper” format documents on them. Most modern monitors have an aspect ratio of 16:9 (wide format). This format most optimally covers the field of view of a person. Ultrawide monitors (21:9, Ultrawide are recommended for gaming and video viewing. Although the screen edges of such monitors fall out of focus, they are visible in peripheral vision, which increases the effect of presence. However, ultrawide monitors show more noticeable color distortion at the edges of the screen, especially if the monitor is directly in front of your face at a short distance.A curved screen reduces the color distortion at the edges, in addition, such a screen further enhances the effect of presence.

Technology and type of matrix manufacturing.
The matrix is ​​called the basis of the monitor - a package of transparent plates, between the layers of which are liquid crystals. To date, there are three types of LCD matrices:

1. TN (TN+film)-most simple technology manufacture of LCD matrices. Advantages - a short response time (the smallest among modern matrices) and low cost. But there are also enough shortcomings: a small viewing angle, poor contrast and color reproduction. The highest response speed has made TN matrices popular among e-sports players, but such matrices are not suitable for professional work with graphics and video viewing.

2. IPS (SFT)/PLS eliminate the shortcomings of TN: they provide full coverage of the sRGB color space, and therefore better color reproduction. They feature high contrast and good viewing angles: up to 180º. IPS are most often used in professional monitors, but relatively recently they began to capture the inexpensive segment, winning a fair chunk of the market from TN.

The disadvantages of IPS are a relatively high price, a long response time and a characteristic glow effect for this type - the glow of the corners of the screen, which is especially noticeable at an angle and with a dark picture.
To date, IPS combines a whole family of technologies that differ slightly in characteristics. The most common technologies are:
- AD-PLS - improved PLS matrix (analogous to IPS from Samsung). It differs from the usual PLS in a shorter response time;
- AH-IPS - better color reproduction and brightness, reduced power consumption;
- AHVA is a technology from AU Optronics that provides a high viewing angle
- E-IPS - increased pixel light transmission allows the use of less powerful backlights, which reduces the price and reduces power consumption.
- IPS-ADS - increased viewing angle and reduced image distortion due to the electric field generated by the electrodes at the edges of the screen.

3. VA in terms of characteristics and cost, they are between TN and IPS types. They have good color reproduction, better than IPS, contrast, average viewing angles and response time.
There are also several technologies for the production of matrices of this type:
MVA(PVA) - improved color reproduction, deep blacks.
AMVA, AMVA+ - further development of MVA technology, with improved color reproduction and reduced response time.
WVA+ is an evolution of HP's MVA technology providing a wide viewing angle of up to 178º
Pixel response time.
Due to the peculiarities of the LCD matrices, the color change of each pixel when a control signal is applied to it occurs rather slowly (by the standards of electronic devices) and is measured in milliseconds. The first LCD matrices had a response time of up to hundreds of milliseconds, they were not suitable for viewing dynamic scenes at all, and even a long trace remained behind the mouse cursor when moving. Modern LCD matrices have a shorter response time, but if this indicator is greater than 15 ms, the image may “blur” when playing highly dynamic scenes. Therefore, this parameter is important for fans of dynamic games and, especially, cybersportsmen. How important?

For example, consider the case where a small "object" crosses the entire screen in 0.1 seconds. Let's say the frame rate in the game is 30 FPS, then the item will receive 3 images during the span, each will stay on the screen for 33 ms. If the response time is more than 16 ms, then for some time two objects will be on the screen at the same time (one - "disappearing" - from the previous frame, the other - "drawing"). So for ordinary players it may not matter, but for e-sports players, the response time becomes almost the main characteristic of the monitor.

monitor brightness, Measured in cd/m2, it defines the luminous flux emitted by a completely white screen at 100% brightness of the backlights. This indicator may be important if the monitor is installed in a well-lit room, in a room with large panoramic windows or on the street - in this case, more brightness is required - from 300 cd / m2. In other cases, a brightness of 200-300 cd / m2 will be enough.

Monitor Contrast is determined by the ratio of the brightness of black and white colors displayed by the monitor. Most modern monitors have a contrast ratio of 1000:1 and this is enough for both work and play. Also in the characteristics there are indicators of dynamic contrast, described as the difference between white at maximum brightness and black at minimum, but there is no single method for measuring dynamic contrast, so you should not rely on this indicator.

Viewing angle
Due to the structure of the LCD matrix, pure color and maximum brightness can only be seen when looking at the screen at a 90º angle. If you look at the screen from the side, the brightness of the glow of the pixels decreases. Even worse, the brightness of the glow of pixels of different colors falls unevenly, so when viewed from the side, colors begin to distort. A small viewing angle was originally one of the worst drawbacks of LCD screens, so monitor manufacturers have constantly been (and are) developing new technologies to increase viewing angles. To date, they have managed to achieve noticeable results - the viewing angles of modern matrices have been brought to the maximum possible.

But not everything is so perfect - a viewing angle of, for example, 176º only means that inside an angle of 176º the screen contrast will not fall below 1:10. The change in contrast will still be quite noticeable and can cause discomfort even if the viewer is inside the viewing angle. Moreover, different monitors (with the same viewing angles) can be qualitatively different when viewed from the side. If the conditions for using the monitor suggest that it will often have to be looked at from the side (for example, a monitor on the wall, a multimedia monitor, an additional monitor), then you should not be guided only by the declared viewing angle, since the viewing angle does not say anything about the dynamics of contrast changes within this angle. This indicator is not indicated by manufacturers, so the only way to evaluate it is to look at the monitor "live".

IPS matrices look best when viewed from the side - noticeable contrast changes begin in most models only when they deviate from the perpendicular by 45-50 degrees, which gives a 90-100º viewing angle without a noticeable decrease in contrast. Worst of all - TN: despite the declared viewing angles of more than 170º, changes in contrast sometimes become noticeable at a deviation from the perpendicular already by 20º.

Maximum refresh rate
The screen refresh rate indicates how fast the image on the screen is updated. Most modern monitors have a refresh rate of 60 Hz and this is quite enough for comfortable work. There is an outdated opinion that this frequency is not enough. PC users who have found CRT monitors remember that it was uncomfortable to work with them at 60 Hz - the screen flickered noticeably. But the design of LCD screens is fundamentally different from the design of CRT screens. LCD screens do not flicker at any refresh rate (or rather, they do flicker, but this has nothing to do with the refresh rate). The inertia of human vision averages 27.5 ms, a minimum of 20 ms, and a refresh rate of 50 Hz is enough for smooth movement on the screen. Some gaming monitors support frequencies up to 240Hz, with the claim that this will provide maximum smoothness and detail of movements. For this statement to make sense, the video card must not only support such a frequency, but also provide the appropriate FPS. For high resolutions, a rare graphics card will be able to deliver the same 240 FPS even on older games.

Support dynamic update screen may be more useful for smoothing motion in games. The essence of dynamic update is to “adjust” the screen refresh rate to the FPS provided by the video card in order to avoid a situation where the moment of the screen update falls on the moment the next frame of the game is displayed and only half of the new frame is drawn on the screen. Although this image lasts for a negligible amount of time, the effect can be noticeable in scenes with sudden changes in brightness. FreeSync technologies from AMD and G-Sync from Nvidia prevent such situations. Technology differences for the user are expressed in the minimum supported FPS: for G-Sync it is 30 FPS, and for FreeSync it is 9.

Screen coverage can be glossy or matte (anti-reflective). In a glossy surface, as in clean glass, light sources are reflected, and when the room is brightly lit, objects around the monitor and the operator himself are reflected. It is believed that glossy screens provide more saturated colors, but they are comfortable to work with only in the right lighting. Matte surfaces are devoid of such shortcomings - reflections of objects are not visible on them, and even glare from bright light sources is minimized.
Color gamut shows how well the monitor can display all colors from a particular color space. color space sRGB is the standard color space used by most consumer photo and video devices. If your monitor does not provide full sRGB coverage, it may lose some of the colors displayed on other devices with full sRGB coverage. The average user probably won't notice, but designers and photographers shouldn't choose this model.

color space Adobe RGB slightly wider than the standard due to the rich shades of blue, green and yellow. Most consumer devices will not be able to reproduce these additional colors, but many fall into CMYK spaces and can be printed. Therefore, monitors with full coverage of Adobe RGB are needed by professional printers and those photographers who work for print publications.

Touch screen today is no longer perceived as a curiosity, but there is little point in buying a monitor with touch screen no - the accuracy of cursor positioning with a finger is much lower than with a mouse, plus prints on the surface of the monitor do not paint it at all. Touch screen monitors are usually used only for special purpose computers - for example, installed in public areas to inform visitors or for visitors to work with specialized software, again in public places.

Sometimes the conditions for using the monitor require it to be able to change its position over a wide range - turn it on a stand, raise it, lower it, and change its tilt. You can purchase a separate bracket, or you can choose a monitor with an appropriate stand - height adjustable, tilt and swivel, with a 90º turn - portrait mode, which is convenient when working with narrow and long page documents.

If the stand is not enough, and you want to mount the monitor to the bracket, then most monitors are equipped with VESA mount, you just need to choose the appropriate size for the bracket.

Important characteristics of monitors are the presence of certain connectors. It can be video connectors:

- VGA(D-SUB, DB15) - legacy analog RGB connector. At the moment, support for the VGA standard has been discontinued; on modern monitors, this connector is installed for compatibility with older video cards. It should be used as a last resort - in the absence of a digital connection. The maximum resolution when connected via this connector will be 2048x1536 pixels at 85 Hz.

- DVI(DVI-D) is a more modern connector used for transmitting video information in digital form. The maximum resolution allowed when connected via this connector is 2560×1600 at 60 Hz in Dual link mode. If the monitor resolution is greater than 1920×1080, then to connect it through this connector, the video card must be equipped with a DVI-D Dual link connector.

- HDMI- the most common connector for transmitting high-definition digital video data today. The latest revision of HDMI supports resolutions up to 10K at 120Hz, with no such monitors commercially available yet.

- display port(mini Displayport) is an analogue of HDMI, designed specifically for computer equipment. The latest edition supports a maximum resolution of 8K (7680 × 4320) at 60Hz.

- Thunderbolt- Apple interface. Thunderbolt versions 1 and 2 use their own connector (also called Thunderbolt), Thunderbolt version 3 uses a connector USB Type-C. Thunderbolt version 2 supports resolutions up to 4K (3840 × 2160), version 3 supports resolutions up to 5K (5120 × 2880). Sometimes found in appliances and other brands.

The monitor may have additional connectors:
- 3.5 headphone jack: HDMI and Displayport interfaces allow sound transmission, then the headphones can be connected not to a computer, but to a monitor.

USB - some manufacturers build it into the monitor USB hub

Built-in speaker system can save space on the table and get rid of extra wires - sound is also transmitted to it via HDMI or Displayport. Suitable for simple voice acting for undemanding users.

Monitor Options

Let's start with the budget segment. If you are an unpretentious user, then buy the most inexpensive 18-21 ”monitor, which is quite suitable for working with office programs.

The quality of the matrix, viewing angles for such models will not be so hot, but at least all this is offset by accessibility.

The best option for the home is 23-25 ​​inch models with FullHD resolution. Not too big and not too small - the ultimate balance of clarity and cost.

Not demanding on the PC graphics card, as in the case of 2K or 4K models, the pixel size is acceptable. Image, fonts and icons will not be so small. Choose the type of matrix, design, set of connectors, etc., depending on personal preferences and wallet. If you need maximum picture quality, then it will be IPS, VA and other types of matrices other than TN. TNs themselves are somewhat cheaper and often faster, i.e. better suited for dynamic content and games.

For aesthetes or lovers of design solutions, monitors with a "frameless" case are offered. This does not affect the functionality, but such elegant monitors look quite nice on the table.

How we test smartphones and tablets | Display tests

The display of a mobile device serves as its main interface. During the day, we can look at it for more than one hour under different lighting conditions. Since the quality of the display greatly affects the perception of the image, it is necessary to carefully study its operation.

For display measurements, we use the SpectraCal C6 colorimeter, which accurately measures the color and brightness of LCD and OLED screens. The C6 is calibrated by SpectraCal using a Konica Minolta CS-2000 spectroradiometer and is NIST (National Institute of Standards and Technology) certified for accuracy. Although enclosed designs such as the C6 are more stable than designs that expose the filters to air, the accuracy of all colorimeters can change over time. Therefore, our C6 instrument is recalibrated if necessary.

With the C6 colorimeter, we use SpectraCal CalMAN Ultimate for Business v5, which allows you to create your own workflows and offers many measurement options. In the process, the CalMAN program creates beautiful graphs that you see in our reviews.

When testing, the C6 is placed in the center of a carefully cleaned device screen. Test patterns for display testing are controlled manually or using the CalMAN program running with the SpectraCal MobileForge application.

Display Brightness

Maximum and minimum

Display brightness is measured in candelas per square meter (cd/m2) or nits and affects the readability of the screen under various lighting conditions. The higher the maximum brightness, the easier it is to see the screen in bright environments, such as in a well-lit room or in direct sunlight outdoors. For dimly lit rooms or at night, a lower minimum brightness is preferred so that the screen does not dazzle you and disturb others.

To measure the maximum brightness, the display brightness control is set to the maximum value and a 100% white pattern is displayed on the screen. The minimum brightness is measured in the same way, but the brightness control is set to the lower limit.

The obtained values ​​show the maximum and minimum brightness achieved with the standard brightness control. But sometimes you can "unlock" higher or lower values ​​by using third-party apps to control screen brightness. The correlation of the adjustment level with the brightness value is factory-configured and can be set below actual hardware limits. If there are significant differences between stock and unlocked metrics, we may add them to the overview.

Display brightness: maximum and minimum, nits (more is better)

Full brightness chart, including values ​​at APL=50

For OLED, we measure two brightness levels: APL = 50% and APL = 100% (APL - Average Picture Level). This is because the brightness of the OLED display changes depending on the image on the screen ( ( (English) you can find a more detailed discussion of APL). The APL values ​​used provide good upper and lower bounds for real data.

Note! Maximum brightness values ​​for OLED screens with APL not set for measurements are essentially useless. In the technical specifications of many manufacturers, and even on some media sites, the indicated brightness values ​​\u200b\u200bare found to be significantly higher (sometimes up to 10%) than we get at the lowest levels of APL.

After calibration

After measuring the maximum and minimum brightness levels, the screen is calibrated to 200 nits ± 1%. In this mode, the rest of the display and battery tests are performed.

Since some manufacturers adjust the brightness slightly, often dimming it after a few seconds or minutes of adjustment, we continue to monitor screen brightness during all tests to make sure it stays at 200 nits.

Black level and contrast

Black level: White level 200 nits (lower is better)

Contrast ratio: 200 nits white level, ratio: 1 (higher is better)

The black level represents the brightness of the all black (0% white) pattern that we measure after setting the brightness of the 100% white field to 200 nits. OLED displays show true black as they turn off the pixels. But this does not apply to LCDs, which use a separate always-on backlight. Even when the LCD panel pixel is disabled, there is still light leakage from the backlight.

The display contrast indicates the ratio of brightness between an all white (100% white) and all black (0% white) field, or in other words, the contrast is equal to the value at 100% white divided by the value at 0% white. As with dynamic range, the higher the value, the better. Obviously, a lower black level makes blacks appear deeper and maximizes the screen's contrast ratio. Since the black level of OLED displays is close to zero, they have an infinite contrast ratio.

Gamma

The human visual system perceives light non-linearly according to a gamma or power function, and is more sensitive to changes in dark colors than in light colors. This quality improves the dynamic range of vision and prevents blinding from bright sunlight outdoors (the CMOS sensor of digital cameras perceives light more linearly, which is one of the reasons for poor dynamic range).

If the brightness values ​​of digital images were encoded linearly according to the linear brightness levels on the screen (not a CRT), then too many bits of information would be wasted encoding bright areas of the image that we cannot perceive, and too little encoding shadows, which would result in loss of quality or increase in file size. However, with non-linear gamma luminance coding, the bits are optimized for the light we perceive, resulting in higher visual quality and reduced file sizes.

Gamma 2.2 (right)

The gamma value is an exponent used in a power law expression to create a specific gamma curve. The ideal gamma value is 2.2. A screen with a gamma of less than 2.2 appears bright or fuzzy with fewer shadows, while a display with a gamma of more than 2.2 appears darker with loss of shadow detail and fewer highlights. In the photos above, you can see how changing the gamma curve affects the image.

Gamma: White level 200 nits (2.2 is optimal)

Gamma is measured in 10% increments from black (0% white) to 200 nits (in our case, 100% white). For comparison with other displays in our reviews, we display the average gamma of the entire range of brightness. We also include a graph of the gamma values ​​at each measurement point in relation to the ideal value of 2.2, shown by the yellow line. The gamma curve of an ideal display will exactly match the flat yellow line.

CONTENT

One of the most important characteristics that affects human performance is the brightness of light. This characteristic is equal to the ratio of the luminous intensity in a particular direction to the projection area of ​​the luminous surface onto a plane perpendicular to the observation axis. Unit brightness measurements- candela per square meter (cd/m2). Brightness characterizes the spatial and surface distribution of the light flux. For brightness measurements special devices are used - luminance meters.

Brightness meter converts the luminous flux created by a natural or artificial light source into a continuous electrical signal proportional to the level of illumination. This information is displayed on the board. instrument for measuring brightness as a digital value.

Primarily, brightness measurement necessary to control the level of light perception of the human eye. Insufficient or excessive brightness can cause fatigue, visual impairment and, as a result, complete or partial loss of performance. Modern brightness meter is necessary in order to control and promptly respond to changes in this parameter. At the same time, it must be remembered that the light generated by the source must have such a spectral distribution of the energy brightness density that would ensure unambiguous assignment of one or another color to it. The need for constant monitoring is due to the use of modern technology - LCD monitors, TVs, fluorescent lamps, the introduction of LED lamps.

luminance meter- a device of first necessity in the services of labor protection and safety. Luminance meters are widely used in cinemas, science centers, educational and medical institutions, museums and libraries. All without exception, they are compact in size and light in weight.

Measurement method- a technique or a set of techniques for comparing the measured value with its unit or scale in accordance with the implemented measurement principle. According to the general methods of obtaining measurement results, methods are distinguished into: direct and indirect. Direct measurement method- measurement, in which the desired value of the quantity is found directly from experimental data. Direct measurements do not require measurement procedures (MVI) and are carried out according to the operational documentation for the measuring instrument used. Confirmation of the compliance of these methods with mandatory metrological requirements is carried out in the process of approving the types of data of measuring instruments (GOST R 8.563-2009 State system for ensuring the uniformity of measurements. Methods (methods) of measurements). In accordance with the Law of the Russian Federation "On Ensuring the Uniformity of Measurements" (Article 9), measurements must be carried out in accordance with duly certified methods. “Measurements related to the scope of state regulation of ensuring the uniformity of measurements must be carried out according to certified measurement procedures (methods), with the exception of measurement procedures (methods) intended for performing direct measurements ...” (From Federal Law No. 102-FZ “On ensuring the uniformity of measurements” part 1 of Article 5).

Selecting an instrument that performs brightness measurement, depends on the tasks assigned to him. For example, "TKA - PKM" (09) combines the functions of a luminance meter (overhead method), a luxmeter and a heart rate meter, and allows for comprehensive control over all lighting parameters at the workplace. The TKA-YAR film projection luminance meter is indispensable for the installation of film projectors and equipment in cinema halls, and the TK-VD/01 spectrocolorimeter will allow not only controlling the brightness of film screens, but also measuring the color characteristics of digital film projectors. Luminance meters are designed for the brightness of self-luminous objects by the method specified in the passport.

When purchasing such a device for brightness measurements it is necessary to pay attention to the certificates of its compliance with the current sanitary rules and state standards. The scientific and technical enterprise "TKA", founded in 1991, is engaged in the development and manufacture of optical measuring instruments. Thanks to its own research and production base, STP "TKA" is a recognized leader in the production and supply of technical means for controlling lighting parameters.

2014-04-03 All articles