What does contrast mean. What is monitor contrast? Slow pixel response rate, but better than * VA sensors

We continue to understand modern technologies and characteristics of TVs. IN we talked about characteristics such as screen type, diagonal and resolution. Now we will consider the equally important characteristics of TVs: matrix response time, contrast, brightness, viewing angles.

Parameter matrix response time began to gain importance with the advent of televisions, the screen of which is a matrix. When choosing a plasma TV, this indicator can be ignored. Response time is measured in milliseconds (ms) and expresses the time it takes for a pixel to transition from one state to another (for example, from white to black and then back to white). The average response time of LCD screens is 2 to 10 ms.

The response time of the LCD / LED-screen matrix becomes important when watching dynamic scenes. In such cases, TVs with a long response time produce a "blurry" picture: behind fast-moving objects, residual glow trails are formed. To ensure that your shopping experience doesn't spoil, adjust response times to suit your TV use. A screen with a response time of 8-10 ms is suitable for watching movies, broadcasts, but if you plan to connect a computer, limit it to 5 ms.

CONTRAST

Under contrast it is customary to understand the ratio of the brightness of the bright part of the TV screen to the dark. For example, a value of 10,000: 1 means that white areas are 10,000 times brighter than dark areas. The level of contrast is determined by how saturated a dark color looks and how brightly white is displayed. The higher the contrast, the more detail and color can be seen on the screen.

For high-quality video playback in HD format, the matrix's own (static) contrast is not enough, so manufacturers have come up with a technology that allows you to increase this indicator. Modern TVs automatically adjust the screen brightness based on the analysis of the frame content. For low-light scenes, less backlight is emitted, this gives more depth to dark colors; bright frames, on the other hand, become brighter.

Hence the concept dynamic contrast, i.e. contrast measured with automatic brightness adjustments. LED-backlighting of the matrix has significantly increased the contrast, so LED TVs have a clear and deep image (unlike ordinary LCDs).

BRIGHTNESS

In order for the eyes to be comfortable watching TV in any lighting (natural or artificial), the TV must have a high brightness. Otherwise, watching TV will strain your eyesight and lead to fatigue.

Brightness is measured in luminous intensity per square meter. (cd / m2). Plasmas have the highest brightness, this is obvious, because the technology of plasma TVs itself involves the self-illumination of screen elements. LCD matrices have not yet reached such brightness indicators, tk. the flux of light emanating from lamps or LED backlights must overcome a layer of not quite transparent liquid crystals.

Typically, the brightness of LCD and LED TVs is in the range of 300-600 cd / m2, while the brightness of a plasma TV is 1000 cd / m2 and above. But don't jump to conclusions! Too high brightness entails a loss of contrast (however, some unscrupulous manufacturers, for obvious reasons, prefer not to mention this). There should be a golden mean in everything.

To make it easier for you to find the optimal combination of contrast and brightness, start from the following data:

• budget TV - brightness from 300 cd / m 2, contrast ratio from 1000: 1;
• mid-range TV - brightness from 400 cd / m2 , contrast ratio from 5000: 1;
• expensive TV model - brightness from 600 cd / m2 , contrast ratio from 20,000: 1.

And, nevertheless, too much brightness does not happen, moreover, it can be easily adjusted. The only rule to follow is not to place your TV in front of windows, otherwise sunlight will ruin the whole experience.

ANGLES OF VIEW

The viewing angle is the angle to the plane of the screen, when viewed from which the image is visible without distortion. The characteristic became relevant with the advent of digital TV. Possible image distortions are associated with the very structure of the LCD matrix. The fact is that the screen backlight (lamps or LEDs) is located at a very small, but still, distance from the matrix pixels. Because of this, the light falls into the "gap" between the pixels and the lamps, the diffusion area is limited.

In practice, this is expressed in the fact that with an increase in the viewing angle, we notice a decrease in brightness and contrast, the picture quality gradually deteriorates. The best image we see is perpendicular to the screen. In the range of +/- 60 o we observe an image of acceptable quality. Therefore, a distortion-free picture is available at a viewing angle of approximately 120 degrees.

Expensive and thin TVs have a larger viewing angle (170-175 o). For budget models, values \u200b\u200bof about 160-170 o are typical. There is a little trick here: with the correct installation, you can easily avoid "unsuitable" corners! Therefore, it is important to think about where you are going to install the TV.

For "plasma" this characteristic is not so important. A fundamentally different technology provides a large viewing angle (175-180 o).

PW Note: This article from ProjectorCentral covers the subject of contrast excellently. While at first glance there seems to be a contradiction with my approach (I love the Full On / Off contrast setting), I would like to point out the following:

1. In the end, the author completely abandons independent measurements of ANSI contrast.
2. The author emphasizes the uselessness of the "full on / off contrast" parameter (hereinafter - Full On / Off Contrast) for an ordinary buyer, based on the data published by the manufacturer.
3. The author talks a lot about the more expensive segment of home theater projectors.

Of all the published characteristics of projectors, the parameter " Full On / Off Contrast" least useful and more than others confusing... The claimed contrast will not provide much useful information about what you will actually see on the screen and certainly will not provide any useful information as to how the two projectors will look when compared side-by-side.

And yet, since buyers usually do not have the opportunity to see the projector in action or compare with another model before buying, they are addicted to the contrast declared by the manufacturer for a completely understandable reason. And who doesn't want a high contrast projector? And manufacturers are well aware of such sensitivity of the buyer to the contrast parameter, and therefore are forced to inflate it to absurd values \u200b\u200bin order to simply stay in the game.

Why are contrast specifications so terrible

There are two common methods for measuring contrast - " Full On / Off"and" ANSI". The first type of measurement is easier to manipulate, gives confusing numbers, and is the one most commonly used in the projector industry. The ANSI method is difficult to manipulate and produces much lower contrast values, but is much more informative. This method is rarely used. by manufacturers of projectors, excluding specific niches.Let's see the difference between these methods.

Parameter Full On / Off Contrast Ratio measures the ratio of the brightness of an all-white test image (100 IRE, “full on”) to the brightness of an all-black image (0 IRE, “full off”). A ratio of 10,000: 1 means that the meter has recorded that the brightness of white is 10,000 times greater than that of black.

In contrast measurement method " ANSI"no white (100 IRE) and black (0 IRE) fields are used. Instead, a checkerboard image is used, consisting of 16 rectangles - 8 black and 8 white. First, the brightness of all white cells is measured and the resulting values \u200b\u200bare averaged. Then the same is done with the black cells The ratio of the average white value to the average black value is the ANSI contrast ratio.

When it comes to projectors, the Full On / Off and ANSI methods give completely different numbers, and the ANSI contrast ratio is always significantly lower (in fact, incomparably lower). The reason is that, although we usually get similar white luminance values \u200b\u200bfor an all-white test image (100 IRE) and for white squares on a checkerboard, the black luminance levels on black checkerboard squares used in the ANSI method will always be higher than on a completely black test image (0 IRE).

Why is this actually so? First of all, there is always the possibility of light scattering inside the optical system of a projector when projecting anything other than a black screen. When the projector is displaying an all-black test pattern (0 IRE), there is simply no light to scatter inside the projector, degrading black levels. On the other hand, when projecting a checkerboard, the picture is 50% white, and a lot of light passes through the projector. A tiny amount of this light is reflected and re-reflected within the lens or optical path, ultimately affecting the black level on the projected checkerboard. In addition, any dust caught in the path of the projected light will scatter it.

But the reader will ask: "How can miniscule light scattering have such a significant impact on the contrast ratio?" Can! For example, the meter shows that with “full on” white screen (100 IRE) we have 1000 units, and with “full off” black (0 IRE) we have 0.05 units. This will be a contrast ratio of 20,000: 1.

Switching to the "checkerboard", the brightness of the white cells is still 1000 units, but due to light scattering, we get 0.5 units on a black screen instead of 0.05. In this case, the contrast before our eyes fell 10 times, to 2000: 1, due to a subtle, almost invisible to the human eye (except in very dark conditions) change in the black level. This change in black level will be offset by any amount of bounced light in the room. Looking at the test patterns, the difference in contrast between 20,000: 1 and 2,000: 1 doesn't look as huge as the numbers differ.

But the fact remains that even small changes in black levels have a significant impact on the contrast setting. Everyone was paying attention to this little red EXIT sign in the theaters. This single sign can easily produce enough light to halve the contrast on the screen compared to a completely dark room.

Automatic iris and the like ...

When it comes to manipulating the "Full On / Off" contrast levels, the behavior of the projector itself plays a huge role. Many models adjust their luminous flux to the average brightness level of each individual scene. They can do this by adjusting the power consumption of the lamp on the fly, opening and closing the iris, or turning off the laser. Thus, when projecting a dark scene, you can instantly reduce the luminous flux level to make black appear blacker. Then, when it comes time to display a bright image, the light output is returned to its full power, resulting in a brighter, brighter image. For most projectors using these features, this adjustment of the light output is so fast that the viewer will rarely be able to notice it.

These dimming functions do work and are useful, and we're not saying they are bad. The point is that they confuse all the cards in the game of contrast. When the projector adjusts brightness in this manner, the “Full On / Off” contrast level will be based on measuring the blackest black in a dark scene and comparing it to the brightness of white in a bright scene, where similar black and white levels would not be possible in a single frame. Some manufacturers call it " Dynamic"contrast instead of" Full On / Off "contrast to emphasize that the numbers are obtained using the aforementioned real-time luminous flux adjustments.

This is where the ANSI method comes in handy. Since it assumes the use of one test image, which is 50% white and 50% black, it completely excludes from our calculations the ability of the projector to dynamically adjust the luminous flux, changing it from frame to frame. As a result, the ANSI contrast level will be significantly lower dynamic contrast ratio. In theory, this setting will give you a better idea of \u200b\u200bwhat you can see in any given frame.

Of course, ANSI contrast will not show anything about the positive contribution of dynamic dimming, so you'd be right to argue with me and say that ANSI contrast doesn't tell the whole story either.

Accurate ANSI contrast measurement

Despite our best wishes, ProjectorCentral.com does not measure ANSI contrast during the review process. This is because accurate ANSI contrast measurement requires either a pitch-dark room with completely black and non-reflective walls, carpets, ceilings, clothing, etc., or a black tunnel camera or tent specifically designed for this task. Why? Because the light from the white cells of the "checkerboard" is reflected from all objects in the room, highlighting the black cells, making the obtained contrast measurements obviously defective. The only type of contrast measurement, at least which we would be willing to publish, should be done in a specialized laboratory equipped with everything necessary to carry out such measurements.

How different are the numbers for each method?

In general, the "Dynamic" contrast level gives the highest values, "Full On / Off" with disabled luminous flux control will give lower levels, and "ANSI" will give very low contrast values \u200b\u200bthat the consumer is not used to seeing. How small? Well, in the home theater world, where high contrast is preferred over high lumen output, ANSI contrast ratios of 300: 1 would be average, 700: 1 would be very good, and 1000: 1 would be considered outstanding. But how many people would want to buy a home theater projector that has a claimed contrast ratio of 700: 1? In today's highly competitive marketplace with millions-to-one contrast levels, few are.

Christie Digital is one of the few manufacturers to publish all three types of contrast characteristics (Dynamic, Full On / Off, and ANSI). For example, for an installation projector Christie DHD600-Gdeclared 4800:1 dynamic, 1200:1 Full On / Off contrast and 250:1 ANSI contrast ratio. As you can see, even in the world of installation projectors, these methods give completely different numbers. Christie can afford to publish this information as it sells to knowledgeable buyers through professional AV resellers, and in the AV business everyone knows the difference between these parameters and what they mean.

On the other hand, the average consumer has no idea about these differences in contrast measurement methods. Unsurprisingly, they want the highest numbers possible. As such, for a manufacturer whose projectors are sold to the general public, it would be like death to publish ANSI contrast - they do not publish. A projector with an extremely high Dynamic Contrast Ratio, such as 500,000: 1, can still have an ANSI contrast ratio of 800: 1. Plus, this ANSI level means brilliant picture contrast, but the consumer will never know. A manufacturer will only publish ANSI contrast values \u200b\u200bif there is a strong desire to leave the business.

What to do?

To begin with, remember that while it can be technically difficult to measure ANSI contrast accurately, it is very easy to see. The high ANSI contrast ratio is characterized by solid blacks, sparkling whites, good yet natural color saturation [sic], accurate and well-defined shadow detail, and depth and dimensionality. Low ANSI contrast will result in lower black levels, lower color saturation, washed out shadow detail, flatter, two-dimensional image. When you look at the projector and think to yourself, “Wow! This is excellent contrast! " - then often you react to high ANSI, and not Full On / Off contrast.

Second, when setting up two projectors side-by-side, it is usually obvious which one is the most contrasting, without any measurements. The main criterion is comparison of images by their depth (apparent volume).

Third, unless proven otherwise, it should be assumed that there is NO direct relationship between "Dynamic" or "Full On / Off" contrast on the one hand and ANSI contrast on the other. Very high contrast "Full On / Off" doesn’t mean ANSI contrast is high - it can be really high, but you don’t know about it. The projector can have a low Full On / Off contrast ratio while still delivering very high ANSI contrast for impressive images. Don't be surprised if comparing Projector A with a claimed 50,000: 1 contrast ratio with Projector B at 500,000: 1, you find that Projector A looks much more contrasty. This happens all the time.

In other words, the "Dynamic" and "Full On / Off" contrast characteristics are downright misleading. They tell you almost nothing about what the average shot will look like. It would be incredibly useful if everyone published ANSI contrast, but the risk is too great for the manufacturer, simply because the buyer will misunderstand it. Unless the manufacturer suddenly decides to try his luck in a serious way and publish ANSI contrast in the specifications, do yourself a favor and just ignore the declared contrast levels that can be seen in specifications today... The declared Full On / Off and Dynamic Contrast levels will tell you nothing about how the image will look, and they are completely impossible to use to compare projectors.

Transfer from CNET

Do you want to know why such an important image parameter as contrast grows endlessly and remains incomprehensible to many?

Understanding what contrast is and how to measure it will help you choose the best TV based on your capabilities. But this is a little more complicated than it might seem.

Basically, contrast is defined as the difference between the brightest and darkest picture a TV can reproduce. A more precise formula:

white level / black level \u003d contrast.

If a TV can emit 45 fL with a white screen and only 0.01 fL with a black screen, it has a contrast ratio of 4,500: 1. Unfortunately, in reality, things get more complicated.

There are several ways to measure contrast. For example, a manufacturer can measure the maximum light output of one pixel at some maximum inaccessible in normal mode, then measure the light output from the same pixel in the complete absence of a signal. Such a situation is hardly possible with the usual viewing of films and TV programs, but without a generally accepted standard for measuring, such trifles do not bother TV manufacturers.

Moreover, contrast ratios have recently grown to such extreme values \u200b\u200bthat sometimes there is literally no way to measure them. Why did this situation arise? The marketing department declares the numerical values \u200b\u200bwith which it can sell the product. Specialists-developers, in the end, have to be cunning and, lo and behold, the TV gets the necessary contrast. The only way to find out the real abilities of TVs is to read reviews, but even they are not always accurate, as we will see below.

Contrast ratio: good and bad

Since you are reading this article from a display that has a different contrast ratio, you cannot give you real examples of what good and bad contrast looks like, so you will have to look for other ways.

You can check how well your monitor is configured by reading dedicated articles. And below are two images, on the left with good contrast, on the right with poor contrast.

The left image is more accurate with good contrast. On the right, the contrast is worse, the black level is higher.

It's pretty easy to note that the picture on the left is more correct. The picture on the right has a higher black level, and if you choose from two TVs side by side, the choice is clear.

Contrast: natural and dynamic

There are two types of contrast. Most often they are called natural (native) and dynamic. The natural contrast is the one that the display technology allows without trickery. In the case of an LCD display, this feature is determined by the liquid crystal panel. In the case of DLP technology, everything is determined by one or three DMD chips.

Imagine the above images on your TV screen. Natural contrast is determined by comparing the darkest part of an image with the brightest elements in the same scene. Let's call it "the internal contrast of the plot", although, maybe someone has better definitions in this regard?

This contrast is different from what is currently attributed to most televisions, which is called dynamic. Dynamic Contrast Ratio is an extended term for a technology that allows infinitely high readings compared to natural contrast. When playing a movie or TV program, the TV adjusts the overall luminous flux according to the type of scene being displayed. Perhaps you have manually adjusted the LCD backlight, the TV does the same automatically, analyzing the video being played back in real time.

This grayscale is an example of the relative brightness of the display. With the backlight set to maximum, the LCD is at its brightest, but has poor black levels. If the backlight level is set to minimum, the black level will be decent and the overall light output will be insufficient.

Automatic backlight adjustment (similar to the projector's aperture opening adjustment) is performed by the video signal control circuit and allows real-time adjustment of the total luminous flux, depending on what is on the screen at that time. Sample image using dynamic contrast:

In a dark scene, the TV dims the backlight (or covers the aperture of the projector), so the image becomes darker. At the same time, bright areas on the screen are lost, which also darken.

In a light scene, the TV boosts the overall luminous flux, but as you can see from the gray scale, the increased brightness comes at the expense of a decent black level.

Light scenes become brighter and dark ones blacker. This is very good, and does increase the apparent contrast of the display, but not as much as one would suggest based on the stated contrast settings. A TV with a 5,000,000: 1 contrast ratio is fantastic. I would very much like to see him, it is a pity that he does not exist. An HDTV with a high dynamic contrast ratio may look better than a TV that does not have this circuitry, but it will not be as good as a display with a high natural contrast ratio.

Yes, the LED backlighting of the LCD panel can be turned off, creating a true black color, but this is far from always possible during the playback of a real movie. A display with high natural contrast will show bright white text on deep black backgrounds. A high dynamic contrast display may have the same dark background, but the text will not be as bright.

Comparatively, it looks like this:

The image on the left simulates a display with high natural contrast. The one on the right has reduced natural contrast, but increased dynamic. The image on the right is capable of representing low black levels, but it does so at the cost of reducing overall light output. The high natural contrast of the display (left) makes it possible to reproduce as black as possible without technical tweaks, and at the same time bright white.

As you can see, a display with high natural contrast is the way to go. Against the background of an inky black sky, the glare of street lamps is clearly visible. During the day, the sky is bright, but the black jacket is dark enough. It looks more like a picture on CRT TV screens, more like a movie in a cinema, more in line with the real picture.

The technology with the highest natural contrast ratio today is the one used in LCOS home projectors. JVC projectors currently use the proprietary version of this technology (D-ILA). These projectors have the highest natural contrast ratio measured. Sony's version (SXRD) lags far behind, but comes in second. Plasma HDTVs can be considered the third in terms of natural contrast, although some DLP projectors are close to them.

LCD TVs have made great progress over the past decade, but still lag behind other technologies in a number of ways. Fortunately, the best manufacturers are aware of this and have come up with several ways to mimic the high natural contrast inherent in other technologies.

The best way for LCD TVs to achieve high contrast within a scene is to use local dimming. In this case, the display backlight is an array of light-emitting diodes (LED sources), the brightness of each of them can vary depending on what is shown on the screen. Although this is not done and not at the pixel level, and the LEDs are not individually controlled, but by zones, as a rule, the overall effect is very good.

Unfortunately, most manufacturers today have given up on full LED backlighting, which is the only type of good local dimming. These TVs are more expensive to manufacture.

Most LCD LED displays today use side (edge) backlighting, which places the backlight LEDs on the top and bottom of the LCD panel. Several companies have developed methods for dimming specific areas of the screen and for such backlighting (Edge LED), but the effect is not as good as using a full LED array behind the screen. Many side-lit TVs look great though.

Measurement and all other problems

However, you naturally have a question for a long time: How can you find out which TV in the store has the best contrast? Good question. However, the increased brightness of the lighting distorts the actual capabilities of the TV. In addition, some models may have a glossy screen coating, while others are anti-reflective, which also makes comparison difficult. As already mentioned, all manufacturers give overestimated contrast ratios, which have little to do with the real capabilities of TVs. Therefore, you shouldn't really trust the specifications.

So it remains to read the reviews. Unfortunately, only a few sites do contrast measurements during testing. And the obtained indicators can sometimes vary greatly, which is understandable, moreover, there is no single standard for measuring contrast. Someone might estimate a contrast ratio of 20,000: 1, while another tester would only get 1,000: 1.

Much depends on what you measure. You can take the black field (brightness 0 IRE) from the tuning wheel or signal generator, and then the white field (100 IRE) from the same sources. This will give you a decent overall contrast, but it is not very relevant in real-world video viewing (which is never completely dark or completely white). In addition, numerous video processing systems begin to work on real material, which affect the brightness of individual areas of the image.

An ANSI contrast measurement would be a good addition. In this case, eight black and white squares are displayed on the screen in a checkerboard pattern. All measurements are averaged. This gives a good idea of \u200b\u200bthe display's capabilities, and is much more relevant to actual video. A particular problem is that the brightness of the white fields can affect the measurements of the black squares. Thus, in order to do everything right, you will have to spend a lot of time.

Conclusion

In this case, there is no definite answer. This is precisely the conclusion that can be drawn from everything written above. The best you can hope for today in order to get a general idea of \u200b\u200bthe vending HDTV models is fairly accurate measurements given in TV reviews from competent sites. And also the knowledge gleaned from this article will be very useful to imagine what potential TV capabilities will best unfold in the viewing conditions in your home.

As with many TV selection guides, the following can be said. Much depends on the conditions in which you intend to watch TV. If you are a movie lover and watch TV in a dark room or at night, the increased contrast of the plasma will look very cinematic.

If you watch TV more often during the daytime, nothing beats LED LCD in brightness. Somewhere between them are LCD TVs with a local or zone dimming system for LED (LED) backlighting. They can provide better "internal scene contrast" than conventional LCD displays, but with sufficient light output headroom.

Regardless of what kind of TV you have in your home, it is very important to set it up correctly, as the initial factory settings cannot fully reveal the full potential of the TV.

Modern technology is developing rapidly. New TV models appear regularly, offering ever higher picture quality. The concept of "high definition television" emerged and firmly rooted, raising the bar of experience to a new level. The transition to all-digital TV broadcasting is just around the corner, providing superior detail and noise reduction. Therefore, the question of replacing the home screen or buying an additional one naturally arises.

There are more than 120 manufacturers and several thousand TV models in the world. Each company seeks to attract the buyer with new proprietary technologies and developments, which, in order to make the right choice, you need to understand. The purpose of this article is to help you choose your TV.

Screen type

First of all, you need to decide for what purpose the TV is being bought: whether you will watch news or broadcast programs, DVD or Blu-Ray movies, whether you will put it in the kitchen or bedroom. After all, a screen suitable for receiving a satellite signal in a living room and a TV set for watching movie discs are not the same thing. The living room usually contains most of the components of a home media system: a DVD or Blu-ray disc player, surround sound speakers, a satellite receiver, and more. The TV in the kitchen usually works for the background, in the bedroom it is needed to receive terrestrial cable and satellite TV programs, and to view discs. Here you no longer need powerful sound and connection of additional devices. If a TV is needed for a nursery, consider the possibility of connecting game consoles, a camera or camcorder to it. When this issue is resolved, you can begin to understand the characteristics of the TV.

So, first, you must decide on the type of screen.

The following types of TVs are on the market today:

Liquid crystal (LCD, LCD);

Light-emitting diode (LED);

Plasma.

All of them have their own advantages and disadvantages - we will consider them in more detail.

LCD TV

LCD-technology (English LCD - Liquid Crystal Display, "liquid crystal display") is by far the most widespread. An LCD screen is a matrix of many dots, called pixels. Each pixel is made up of three “subpixels” of red, green, and blue. Liquid crystals inside the elements are able to change their position in space under the influence of an electric field, passing or blocking light from the backlight lamps installed behind the matrix. When all three subpixels are fully transparent, the cell is white, and when opaque it is black. Halftones and shades are obtained by mixing the primary colors in the desired proportion. Thus, using a special microcircuit, you can control the transparency of each pixel and form an image.

A design feature of the LCD technology is the need for light to "overcome" a layer of liquid crystals, the transparency of which is not ideal. Therefore, to obtain sufficient picture brightness, it is necessary to install powerful lamps, which increases the price and power consumption of the device. The elements are not able to perfectly block the flow of light - the black on an LCD TV screen is not actually completely black.

Among the shortcomings, it is also necessary to note the distortion of colors and the loss of contrast, since the viewing angle of the LCD is not so wide. Because of this feature, LCD TVs could not gain popularity for a long time, but now, thanks to the efforts of developers, distortion has become almost invisible.

The advantages of LCD TVs include a wide selection of models with different brightness (from 250 to 1500 cd / m2) and contrast (from 500: 1 to 5,000,000: 1). Thanks to this, the buyer can purchase a device that optimally combines the required image quality and affordable price. In addition, LCD TVs are lightweight and thick so they can be wall-mounted. But the biggest merit of liquid crystal technology is its massiveness. Due to large-scale production, prices for LCD TVs are now lower than other similar devices.

Also LCD TVs have gained popularity for their versatility. LED TVs provide comfortable viewing in almost any environment, so they are suitable for most rooms. In terms of the level of contrast and color rendering, expensive LCD models can compete with plasmas, which allows them to take their rightful place, for example, in the living room of the Hi-End class.

LED TV

The difference between LED TVs (English LED - Light Emitting Diode, "light-emitting diode") from liquid crystal is only in the matrix backlight technology: instead of fluorescent lamps, LEDs are used, due to which LED TVs have a number of advantages over LCD.

An LED TV is capable of displaying more colors than a "tube" LCD TV, so the image looks more natural. The use of LEDs made it possible to reduce the thickness of the screen and reduce power consumption by up to 40%, compared to LCD. The brightness and contrast characteristics have also improved significantly.

The only drawback of this technology is its relative high cost. However, the advantages of LED TVs suggest that over time they will become leaders in this market.

Because LED TVs are based on liquid crystal technology, they are as versatile as LCDs. But due to its merits, LED TV will be more preferable than LCD when it comes to your living room.

Plasma TV

Plasma TV screen is also a matrix of small elements, but this technology is implemented in sealed cells filled with gas - neon or xenon. If, with the help of special transparent electrodes, an electric voltage is applied to the cell, then the gas inside it turns into a plasma state and begins to emit ultraviolet light. The rays fall on a phosphor layer applied to the cell wall, which, depending on its composition, emits red, green or blue light. The higher the applied voltage level, the more intensely the cell glows. Different shades of color are obtained by mixing the three primary colors. By controlling the voltage supplied to the cells, the electronic module forms an image on the plasma screen.

Thus, according to the principle of operation, the cells are similar to fluorescent lamps, that is, they have the property of self-luminescence, therefore a plasma TV has some advantages over LCD and LED.

Plasma TVs provide excellent picture contrast and are about 3 times brighter than most LCD and LED screens. After all, a pixel in an inactive state does not emit anything - it is really black, and the light emitted by it in an active state has a sufficiently high intensity. The use of phosphor makes colors vivid and saturated. Plasma TVs have a very fast response time compared to LCD and LED.

Plasma technology has a number of specific design problems. The main one is the problem of the minimum cell size. Creating a small cell - actually a gas-filled glass flask with electrodes - is difficult. Therefore, the development of this technology runs counter to the development of other "matrix" visualization technologies: the diagonals of plasma TV screens have only recently reached 32 inches, while plasma screens with large diagonals (over 50 inches) have been around for a long time.

The availability of only models with large screen diagonals on sale has made plasma TVs the usual choice for buyers who want to get the most out of watching movies in bright, saturated color.

The main characteristics of the TV:

Screen diagonal;

Resolution.

Advanced TV options:

Matrix response time;

Contrast;

Brightness;

Viewing angles;

Interfaces;

Additional functions.

Screen diagonal

Screen diagonal can be considered a fundamental characteristic of a TV. It directly affects its size, weight and price. Correctly selected screen diagonal largely determines the comfort and impressions obtained from viewing, therefore it deserves the utmost attention when choosing.

Traditionally, the size of the screen diagonal is measured in inches and denoted, for example, like this: 32 ". It is easy to calculate it in centimeters: 1 inch \u003d 2.54 cm.

In order for the viewing to be comfortable, the diagonal of the TV screen must necessarily correspond to the size of the room in which it is planned to be installed. The most common in the domestic market are screens ranging from 26 to 42 inches. For a TV in a living room, a large screen diagonal is very important, since the whole family or a group of guests can gather in this room at the same time, and each of those present must perceive the image clearly, while not causing strain and eye fatigue. There can be many layouts, but in most cases a TV with a screen diagonal of 32 ”or more will be optimal for a living room.

For the kitchen and bedroom, it is better to choose a smaller TV, because the area of \u200b\u200bthese rooms is usually inferior to the area of \u200b\u200bthe living room. Studies show that the optimal diagonal of a TV screen should be about 3 times less than the distance at which it is supposed to be watched. If the TV is too large for a given room, the image on the screen will not be perceived as a whole. There may be some "graininess" of the picture and jagged edges between objects. This is especially true for models with a plasma screen: when viewed at too close a distance, the image tends to "disintegrate", that is, individual pixels become visible. Therefore, for the kitchen, we recommend choosing a TV with a screen diagonal of 20-26 ", for a bedroom it can be slightly larger - up to 32".

Most 15-21 ”models have a D-Sub (sometimes referred to as“ VGA ”) or DVI port that allows you to connect your TV to your computer as a monitor.

Resolution

Be sure to pay attention to the screen resolution. This characteristic is responsible for the quality and detail of the image.

The screen of any liquid crystal, LED or plasma TV consists of cells, called pixels, the total number of which is called the screen resolution (English "resolution"). It is expressed as two numbers, the first of which indicates the number of pixels horizontally and the second vertically, for example, 1920x1080. The high resolution screen allows the TV to display crisp images with plenty of detail and smooth lines without jagging.

A 42 ”TV with a resolution of 1920 x 1080 will show a clearer picture than a TV with a resolution of 1366 x 768 at the same diagonal. The point is that having more pixels on the same screen area means that each of them is smaller.

Today, the best image quality available to the general consumer is provided by a relatively new digital television standard - HDTV or high definition television (HDTV).

HDTV (English "High-Definition TeleVision") is a set of high quality television broadcasting standards, which includes requirements for format, resolution and image formation method, as well as for sound quality.

High Definition Standards Formats:

720p: 1280 x 720 resolution progressive scan;

1080i: 1920 × 1080 resolution, interlaced;

1080p: 1920 x 1080 resolution progressive scan.

Scan, denoted by the Latin letters "i" and "p", is a way of displaying a frame on the screen. Unlike Interlacing Scan, Progressive Scan provides better image quality, that is, completely eliminates the combing effect on the edges of objects moving horizontally, as well as jitter of a still picture (for example , in pause mode). To work with progressive scan, the TV needs a more powerful and expensive processor, but support for this mode is mandatory for modern HDTV screens.

High definition television standards are developed by the European Information and Communication Technology and Consumer Electronics Association (EICTA). To facilitate the identification of models, this organization has also published requirements for the technical parameters of devices capable of processing high-definition signals. Also, special markings have been approved.

Models that meet the minimum HDTV requirements are labeled "HD-Ready", which literally means "HDTV Ready". That is, a TV with the "HD-Ready" sticker is necessarily equipped with:

A screen with a resolution of at least 1280x720 pixels;

At least one input capable of receiving HD signals in 720p and 1080i formats. This can be an analog YPbPr1 component input, or digital DVI or HDMI;

At least one DVI or HDMI digital input supporting HDCP content protection technology.

The most common resolution for HD-Ready TVs is 1366x768 pixels. Such models are forced to interpolate the 1080i signal, reducing its resolution.

The "Full HD" label is given to TVs capable of displaying 1080p images and must be equipped with at least one HDMI input to receive a high definition signal. The screen of a modern Full HD TV always has a resolution of 1920 x 1080.

The HDTV TV screen is always widescreen, that is, it has an aspect ratio of 16: 9. This format covers up to 70% of the field of view of the human eye, which allows the viewer to immerse themselves in the atmosphere of the film, which enhances the viewing experience.

Russian terrestrial analogue television broadcasting has a resolution of 720x576 pixels with an aspect ratio of 4: 3. Video from a standard DVD is usually played in 720x480 (16: 9) resolution. A natural question arises - will the new TV be able to receive a signal from "non-HDTV" sources, and how will this affect the image quality?

Yes, an HDTV is capable of receiving and displaying a standard definition signal. In this case, an image with an aspect ratio of 4: 3 can be displayed on a widescreen screen in two ways: with black stripes at the edges of the picture, or by cropping a little at the top and bottom. Some TV models have a special processing unit that removes noise from the analog signal, increases the resolution using interpolation, applies digital anti-aliasing algorithms, thus improving the picture to HDTV standards. However, one should not expect "miracles" from such transformations. A high definition signal is required to obtain a high quality picture.

Unfortunately, there is no widespread high-definition television broadcasting in Russia. This requires the modernization of a large number of TV stations and the transition to fully digital TV broadcasting, which is planned for 2015. Therefore, at the moment only Blu-Ray discs, satellite or cable TV, and game consoles can serve as a source of high-definition signals. Nevertheless, in some regions of the country, digital broadcasting is already being launched, and cable TV networks are emerging and developing.

Matrix response time

The concept of "response time" was not applied to CRT televisions, since the duration of the afterglow of the phosphor was rather short. But with the advent of "matrix" screens, this parameter has become very important.

Matrix response time is the average time it takes for a screen matrix element to transition from one state to another. Excessive response times can result in “trails” of residual glow behind fast-moving objects.

Usually the time it takes for a pixel to go from white to black and then back again is measured. But some manufacturers measure the response time using the so-called "GtG" (Eng. "Gray-to-Gray", "from-gray-to-gray") scheme. The response time is expressed in milliseconds (ms). Its typical values, for example for LCD matrices, are in the range from 2 to 10 ms.

When watching dynamic scenes in films, for example, chases or battles, the fast response time will not allow the picture to "blur". For comfortable viewing of films and programs, a screen with a response time of up to 8-10 ms is enough, but if you plan to connect a TV to a computer, you should limit your choice to models with a response time of less than 5 ms. The response time can be ignored if you buy plasma. In this case, its value is invariably low.

Contrast

Another characteristic of a TV screen that affects viewing comfort is picture contrast, which is the ratio of the brightness of the lightest to the darkest. That is, the brighter the matrix displays white, and the deeper and richer the black, the higher the contrast level of the screen. So, for example, at a contrast ratio of 1000: 1, white areas are 1000 times brighter than black. High contrast allows you to see more shades of color and picture detail.

But the intrinsic, "structural" (also called static) contrast of even expensive LCD matrices is still insufficient, especially when playing HD video, where the requirements for image quality are very high.

To increase the visible contrast, manufacturers have come up with a fairly effective and, at the same time, inexpensive solution. Modern TV analyzes the content of each frame and automatically adjusts the screen brightness. Thus, in low-light scenes, the backlight emits less light, making dark colors deeper, and in bright frames, it becomes brighter, increasing the white.

Contrast measured using this automatic backlight dimming is called Dynamic Contrast (DC). Its values \u200b\u200bin expensive models can reach 5,000,000: 1, and acceptable image quality is provided by dynamic contrast ratios of about 10,000: 1.

The use of LED backlighting for LCD TVs has significantly increased the contrast, so the image on the LED TV screen looks deeper and clearer than on a conventional LCD.

Brightness

The high brightness of the screen allows you to comfortably watch TV in external, natural or artificial lighting conditions. Low brightness images are difficult to read and cause excessive eye strain.

The brightness of a TV screen is expressed in luminous intensity per unit area and is measured in cd / m2 (read as "candela per square meter").

Currently, the most expensive LCD TVs are almost equal in brightness to plasma TVs, which have always won in this parameter due to the self-luminescence of the screen elements. But most of the LCD matrices are still inferior to them, since the flow of light from lamps or LEDs has to overcome a layer of liquid crystals, the transparency of which is not absolute. Typical brightness values \u200b\u200bfor LCD and LED TVs range from 300 to 600 cd / m2, while for "plasmas" it easily reaches 1500 cd / m2.

However, brightness is not the only important characteristic of a TV, as some manufacturers try to teach it. The fact is that with an increase in the brightness of the image, its contrast decreases, and the colors become dull and inconspicuous, despite the declared "large color gamut". Therefore, a high screen brightness must always be combined with sufficient contrast.

Based on practical experience, we can formulate several recommendations for choosing the optimal ratio of brightness and contrast. So, for a budget TV model with a brightness of 300 cd / m2, the contrast should be at least 1000: 1. In the middle segment, we recommend choosing a screen with a brightness of 400-500 cd / m2 with a contrast ratio of about 5000-10000: 1, and for the high-end class - already from 600 cd / m2 to at least 20,000: 1.

An excess margin of brightness will not be superfluous, especially since it can always be adjusted within a fairly wide range. And of course, not every TV can "compete" in brightness with direct sunlight, so you should avoid installing it in front of windows.

Viewing angles

Maximum viewing angle is another characteristic of a TV that has appeared with the advent of digital screens. It denotes the maximum angle to the plane of the TV screen, when viewed from which the image is perceived without distortion.

To understand where the distortions come from, it is necessary to carefully study the structure of the screen matrix - this effect is due to its very structure.

The liquid crystal matrix is \u200b\u200ba multi-layer surface and is a very thin structure. The pixels are optically isolated from each other by polarizing filters, and the lamps or backlight LEDs are located at a very small, but still non-zero distance from them. And therefore the light, passing through the cells, enters a kind of "well", which limits the area of \u200b\u200bits dispersion.

A wider viewing angle is provided by a thinner and therefore expensive matrix. Most LCD TVs have a viewing angle of 170 degrees, while flagship models range from 175-178 degrees.

Distortion appears as a change in screen colors and a drop in apparent brightness and contrast. As the viewing angle increases, the observer sees not a sharp drop in picture quality, but a gradual deterioration. The best results are obtained when looking perpendicular to the screen, and distortion remains subtle in the range from about -60 to +60 degrees. Thus, the optimal viewing angle for the TV is about 120 degrees.

Budget models usually have viewing angles of about 160-170 degrees. But with the correct installation of such a model, viewing from an “inappropriate” angle will be impossible, and you simply will not be able to notice the distortion, while saving quite a lot. A good option would be, for example, installing such a TV at the end (short) wall of a not too large room. In order not to experience discomfort associated with an incorrectly selected viewing angle, you need to consider the location of the TV.

For plasma panels, the viewing angle problem is not so acute, thanks to the peculiarities of this technology. The fact is that visible light is emitted by a layer of phosphor, which is much closer to the outer surface of the screen than lamps or backlight LEDs for LCD and LED screens. Therefore, almost all plasma TVs provide a maximum viewing angle of about 175-178 degrees.

Interfaces

The TV interfaces allow you to connect other devices to it: DVD and Blu-ray players and video recorders, game consoles, digital cameras and camcorders, surround sound speakers, laptops and other attributes of the modern “digital home”.

The list of possible interfaces is wide enough:

Composite (AV). It was widespread in the era of CRT TVs, but the quality it offers does not meet today's requirements. Therefore, televisions are equipped with a composite input for compatibility with older devices. Usually presented in the form of three RCA ("cinch") connectors, one of which, as a rule, yellow, is used for video transmission, and the other two - for stereo sound transmission.

Component. An analog interface that implements the transmission of a video signal in the form of three image components. This eliminates the need to mix the signal in the source and then separate it in the receiver, which provides better picture quality compared to the composite input. However, it is inferior to digital connections and TVs are equipped with component video and audio outputs for compatibility with older devices. Switching is carried out using RCA connectors ("tulip"). Does not transmit sound.

SCART. Combined multi-pin interface for analog transmission (input and output) of image and sound over a cable up to 15 meters long. It is the standard for devices intended for sale on the European market. In terms of the video signal transmission quality, it is at the level of the component interface, but some TV models also allow two-way exchange of digital commands via SCART, for example, the synchronization of the TV and VCR start-up. Compatible with composite and component interfaces using SCART-"tulip" adapters.

SCART-RGB. This designation is sometimes used to identify a SCART interface that supports RGB video transmission for better image quality.

S-Video. An analog connector used to output images to a TV from a computer, laptop, video recorder, digital camera and other devices. Choosing the appropriate adapter cable, for example, from S-Video to 4 "tulips" or from S-Video to SCART, you can connect a variety of image sources. Does not transmit sound.

D-Sub. A common standard analog video output used to connect computers to a TV. The signal transmitted via this interface is very sensitive to interference and electromagnetic interference, so the image quality depends on the quality of the cable used and its length, which can be up to 15 meters. D-Sub equipped TVs can usually be used as full-fledged computer monitors. Does not transmit sound.

DVI. Transmits a higher quality image than D-Sub due to the use of a digital signal format and no double digital-to-analog conversion. A 4.5 meter DVI cable allows you to transfer images with a resolution of 1920x1200, and a 15 meter cable - up to 1280x1024 pixels. Does not transmit sound.

HDMI. a modern high-definition multimedia interface designed to transmit high-definition video (up to 2560x1440) and multi-channel audio over a single cable up to 5 meters long. It is compatible with DVI, but is mainly used for switching various household audio / video equipment; also, via HDMI, you can connect a computer equipped with this interface to a TV.

Mini-jack. The stereo jack used for audio output is often found on the front of the TV. In this case, it is intended to connect headphones.

Coaxial audio output (BNC). Digital interface for sound transmission. It features high signal quality and minimal interference. Used to transfer sound between the TV and a disc player or AV receiver, and to connect surround speakers.

Optical audio-out (Toslink). Digital interface for transmitting surround sound. Allows you to transmit a multichannel signal without interference, thanks to the use of an optical cable that is not susceptible to electrical interference. Used to transfer sound between the TV and a disc player or AV receiver, and to connect surround speakers.

USB. A computer connector that has become widespread in television technology. Used to read music and videos from flash drives. Usually located on the front of the TV, which allows you to quickly connect a USB flash drive for viewing. In the absence of digital TV broadcasts, the USB port can serve as a convenient HD source.

As a rule, any TV set is equipped with a wide range of various connectors, but only expensive models can boast all existing interfaces, and, accordingly, versatility in connection.

When choosing a TV, you need to think in advance about what devices you plan to connect it to, and make sure that the TV model you choose has the appropriate interfaces. In the set of ports, it is better to include those that may be useful in the future.

Recently, it has become very popular to connect devices via HDMI. In addition to its high bandwidth, this interface is highly versatile and therefore fitted on many components of a modern home media system. Preference should be given to TV models that have as many HDMI ports as possible.

Tuners

Despite the possibility of connecting many signal sources, receiving television programs remains an important task for the TV. Any TV has a built-in electronic unit that is responsible for receiving terrestrial, satellite or cable television signals, which is called a tuner (English "tuner", literally, "tuner").

A TV can be equipped with more than one tuner. Thus, two tuners allow using the "Picture-in-picture" (PIP) mode to display images from two TV channels at once. This can be useful, for example, if you are waiting for a show to start while watching news or music videos. Often the manufacturer indicates PIP support in the characteristics of a TV that has only one tuner. In this case, this function will only work when connecting additional signal sources other than the antenna: disc player, computer, camcorder, satellite receiver or others.

Tuners are of three types:
analog.So far, the most relevant type of tuner for the Russian buyer. Allows you to receive an analog TV signal from a conventional antenna or cable TV network;

digital. Able to receive a digital television broadcast signal. At the moment, it is practically not conducted anywhere in Russia, therefore, the presence of a digital tuner on the TV now can only be considered as a reserve for the future;

hybrid. Combines the capabilities of digital and analog tuners. There are a lot of TVs equipped with a hybrid tuner on the market today, and buying such a model can probably be considered the best option.

Sound

The built-in speaker system is present in almost any modern TV. When buying a TV screen for the living room, it usually means connecting a home theater system, but if the target room is a kitchen or bedroom, you can also look at the device's own audio capabilities to save space.

Inexpensive TVs can only reproduce mono sound and use one or two speakers. More advanced ones are equipped with a built-in stereo system, in which the number of speakers can be from two to eight. Some Russian terrestrial TV channels broadcast with stereo sound in A2 / NICAM format, and for full reception of such broadcasts, the tuner must also support this format.

The high power of the TV's built-in speaker system is important for generating sufficient sound power in large rooms. It is rational that TVs of small diagonals are equipped with acoustics with a power of 1-5 W, and large ones - 10-20 W or more. As a rule, the manufacturer selects it in such a way as to provide a comfortable sound when the TV is installed in a suitable room (see the subsection “Screen diagonal”).

When choosing a TV for the living room, you should pay attention to the presence of a Dolby Digital processor in it. It will allow the TV to independently decode the signal for playback of a multi-channel 5.1 sound track, and if there is a built-in amplifier, output it to an external speaker system. Otherwise, you will need to connect another device equipped with a Dolby Digital decoder to enjoy surround sound.

Additional functions

Many modern TVs have in their arsenal a set of additional features with the help of which manufacturers expand the functionality of products. It is rather difficult to give any specific recommendations here: your choice, most likely, will depend on how necessary and convenient one or another function seems to you.

Some Philips TVs are equipped with the AmbiLight function, which uses additional multi-color lamps on the cabinet to create ambient lighting in the room. Its color is chosen depending on the color prevailing in the scene: for example, if there is fire there, the backlight will be orange-red. This enhances the movie experience and immerses you in its atmosphere.

Panasonic Viera series TVs have a VIERALink function that allows you to easily combine multiple devices of this brand, such as a disc player, satellite and AV receiver into a single coordinated system and control it with just one remote control. The Sony BraviaSync technology used in the Bravia series TVs works in a similar way.

Below is a short list of other additional features found in many TV brands from different brands:

off / on timer. Allows you to set the TV to turn on or off automatically at a specific time. For example, the screen in the kitchen will turn on when you go to work;

24Hz (24p True Cinema).Films are initially shot at 24 frames per second. But when burning them to a regular DVD, the format requires 25 frames per second, which leads to a slight acceleration of the image when viewing. A TV that supports this function is able to restore the original playback frame rate, provided the disc player also supports it;

program guide (EPG). Electronic program guide with description. More convenient than its paper and newspaper version, but support for this function exists only for digital terrestrial or cable TV broadcasting;

protection from children. Prevents children from turning on the TV when adults are away. It can also implement blocking of individual TV channels;

teletext. Allows you to receive additional information on the TV screen, if such an opportunity is provided by local television broadcasting;

automatic volume control. TV channels and disc recordings may have different volume levels. This function automatically analyzes the volume of the sound source and adjusts it according to a user-selected level;

enter channel names. Allows you to easily identify channels using custom labels;

list of favorite channels. You can add the channels you would like to watch into it, without wasting time switching programs one by one;

freeze frame (Time Shift). Provides the ability to "stop time" by pausing while watching a TV program. Naturally, its broadcast continues, but you will not miss anything, since the TV saves a video to its internal memory, which you can watch later.

Some TV models provide a choice of operating modes: standard, game, cinema and others. Switching to the appropriate mode allows you to automatically adjust the display settings so that they are optimal for the selected image type. For example, the game mode activates a special circuit to reduce the response time of the sensor and thereby eliminate the blur effect of fast-moving objects, which is very important for games.

We buy a TV

Following these recommendations and carefully analyzing the parameters, you can easily choose the TV that is most suitable for you. We hope that with the help of our advice, you can create a modern, high-tech, well-functioning media system in your home that will make your stay at home more fun and enjoyable.

Contrast

Contrast - in the most general sense, any significant or noticeable difference (for example, “Russia is a country of contrasts ...”, “contrast of impressions”, “contrast of taste of dumplings and broth around them”), not necessarily quantified.

Contrast - the degree of contrast, most often expressed quantitatively as a dimensionless quantity, ratio or logarithm of ratios.

Basic meanings

Quantitative characteristics

Contrast as a transfer characteristic

In quantitative measurement, in contrast to the previous group of meanings of the term, the ratio of the differences of two measured quantities, the output signal and the input, is used.

In the context of optical and photometric measurements, the term is used contrast ratio or contrast ratio... A similar parameter of the transfer characteristic in electronics is called ac gain.

• Lowered lens contrast - an integral characteristic describing the decrease in the contrast of the image formed by the lens in comparison with the contrast of the optical object. Depends on lens aberrations, coating, lens processing, frame features, scene and lighting. Usually not standardized and not described with an exact numerical value or graph.

Other meanings and terms

• Contrast (statistics) (eng. en: Contrast (statistics)) is a linear combination of two or more average values. In the simplest case, the difference between the two mean values.
• Cold and hot shower - alternate change of water temperature from the coldest to the hottest and vice versa.
• Linguistic, or semantic contrast (eng. en: Contrast (linguistics)) - opposition (eng. opposition) between the two parts of the argument.
• Contrast agent (eng. en: Contrast medium) - a substance added during medical examinations (usually with radiography and fluoroscopy) in the body fluid to obtain a more contrasting image of the organs being examined. For example, Barium Sulfate, Iodolipol.

Notes

• Photocinema: Encyclopedia / Editor-in-Chief E. A. Iofis. - M .: Soviet Encyclopedia, 1981. Articles:

Wikimedia Foundation. 2010.

See what "Contrast" is in other dictionaries:

CONTRAST, contrast, many others. no, wives. (book). distract. noun to contrasting; the presence of contrast. Ushakov's explanatory dictionary. D.N. Ushakov. 1935 1940 ... Ushakov's Explanatory Dictionary

CONTRAST, oh, oh; ten, tna. Ozhegov's Explanatory Dictionary. S.I. Ozhegov, N.Yu. Shvedova. 1949 1992 ... Ozhegov's Explanatory Dictionary