Contrast and dynamic contrast difference. Advantages of static contrast. Low pixel response speed, but better than *VA matrices

Practical photography Bunimovich David Zakharovich

What is contrast

In everyday life, we call any sharply expressed opposite contrast. The concept of contrast can be applied to anything. Let's see what this means in photography. Briefly, it can be expressed as follows: contrast is the ability of photographic materials to convey the brightness of the photographed object with varying degrees of difference.

At one time, photographic films of different contrasts were produced. Some films conveyed differences in brightness in the same way as we distinguish them in real life, that is, without distortion. Such films were called normal. Others conveyed these differences with some understatement. They were called soft. Still others, on the contrary, exaggerated the difference in brightness. They were called contrasting.

The task of photography is to correctly, without any tonal distortions, convey the photographed object in the picture, and it is quite obvious that this can be done using only normal films. Therefore, simultaneously with the release of photographic films of the “Photo” type in four degrees of sensitivity, the production of soft and contrasting photographic films was also stopped, and all films of the “Photo” type are now produced only in normal grades.

However, shooting objects are different, and their correct reproduction in a photograph does not always meet the photographer’s creative intent. In practice, we sometimes have to photograph objects that are themselves very sluggish. This is what many objects look like in cloudy weather. It’s a different matter if you intend to consciously emphasize this lethargy, dullness, cloudy weather. Then, of course, it is best to shoot on normal films. But if such a task is not necessary and it happens that the picture needs to be made with contrast, and the weather is cloudy, then a contrast film could help out.

The opposite cases also occur, especially in summer, in clear, sunny weather. Bright sunlight greatly increases the contrast of the subject. When shooting on normal films, the object will turn out to have the same contrast. The details of an object in the shadows may disappear in the photo. In such cases, soft film could soften the contrast and thereby improve the technical quality of the image.

But the contrast also depends on the development time. Depending on how long you take to develop the film, the negatives may come out with different contrasts. Therefore, contrast can be controlled on normal films as well.

Translation from CNET

Do you want to know why this important parameter Images like contrast grows endlessly and remains incomprehensible to many?

Understanding what contrast is and how to evaluate it will help you choose best tv, based on your capabilities. But it's a little more complicated than it might seem.

Essentially, contrast is the difference between the brightest and darkest images the TV can produce. More precise formula:

white level / black level = contrast.

If a TV can produce 45 foot-lamberts of brightness with a white screen, but only 0.01 foot-lamberts with a black screen, it has a contrast ratio of 4,500:1. Unfortunately, in reality everything becomes more complicated.

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

Moreover, the contrast ratios in Lately have grown to such extreme values that sometimes there is literally no way to measure them. Why did this situation arise? The marketing department states the numerical values with which it can sell the product. In the end, specialist developers have to cheat and, lo and behold, the TV gets the necessary contrast. The only way to find out the real capabilities of TVs is to read reviews, but even they are not always accurate, as we will see later.

Contrast ratio: good and bad

Since you are reading this article from a display that has its own contrast ratio, it is not possible to give you real examples, what good and bad contrast looks like, so you'll have to look for other ways.

You can check how well your monitor is configured by reading special 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 quite easy to notice that the picture on the left is more correct. The image on the right has more high level black, and if you choose from two TVs placed next to each other, the choice is clear.

Contrast: natural and dynamic

There are two types of contrast. Most often they are called natural (native) and dynamic. Natural contrast is the one that display technology allows you to present without tricks. For an LCD display, this capability 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 this “internal contrast of the plot,” although someone may have better definitions in this regard?

This contrast is different from that which is attributed to most TVs today and which is called dynamic. Dynamic contrast is an extended term to describe a technology that allows for infinitely higher readings than natural contrast. When playing a movie or TV program, the TV adjusts the overall light output according to the nature of the scene being displayed. You may have manually adjusted the backlight of the LCD display, but the TV does the same automatically, analyzing the video being played in real time.

This gray scale is an example of the relative brightness of a 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, there will be a decent black level, but the overall light output will become insufficient.

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

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

In a bright scene, the TV increases the overall light output, but as you can see from the gray scale, increased brightness comes at the cost of losing decent black levels.

Light scenes become brighter, and dark ones become blacker. This is very good, and does increase the visible contrast of the display, but not as much as the stated contrast parameters would suggest. A TV with a contrast ratio of 5,000,000:1 is fantastic. I would really like to see it, it’s a pity that it doesn’t exist. An HDTV with a high dynamic contrast ratio may look better than a TV that doesn't, but it won't perform as well as a display with a high natural contrast ratio.

Yes, the LED backlighting of the LCD panel can be turned off, creating true black color, but this is not always possible during the playback of a real movie. Display with high natural contrast will show bright white text on a deep black background. A display with high dynamic contrast can 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 enhanced dynamic contrast. The right image can represent low level black, but does this by reducing the overall luminous flux. The high natural contrast of the display (left) allows you to reproduce maximum blacks, and at the same time bright whites, without technical tricks.

As you can see, a display with high natural contrast is what you need. The glare of street lamps is clearly visible against the inky black sky. During the day the sky is bright, but the black jacket is quite dark. It looks more like the picture on the screens CRT TVs, more like a movie in a cinema, more consistent with the real picture.

Today, the technology with the highest natural contrast is used in LCOS home projectors. Currently used in JVC projectors proprietary version this technology (D-ILA). These projectors have the highest measured natural contrast ratio. The version from Sony (SXRD) is quite behind, but takes second place. Plasma HDTVs can be considered 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, best manufacturers know this and have come up with several ways to imitate the high natural contrast characteristic of 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 change depending on what is shown on the screen. Although this is not done at the pixel level, and the LEDs are not controlled individually but by zones, the overall effect is generally very good.

Unfortunately, today most manufacturers have abandoned the use of full LED backlight, which is the only type of good local dimming. Such TVs are more expensive to produce.

Most LCD LED displays Today they use side (edge) lighting, in which backlight LEDs are placed on the top and bottom of the LCD panel. Several companies have developed methods to dim specific areas of the screen and backlight them (Edge LED), but the effect is not as good as using a full LED array behind the screen. Although many edge-lit TVs look great.

Measurement and all other problems

However, you naturally have long had a question: 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 real capabilities of the TV. In addition, some models may have glossy finish screen, while others are anti-glare, which also makes comparison difficult. As already mentioned, all manufacturers give inflated contrast ratios, which have little to do with real opportunities TVs. Therefore, you should not put much faith in the specifications.

So all that remains is to read the reviews. Unfortunately, only a few sites take contrast measurements during testing. And the obtained indicators can sometimes vary greatly, which is understandable, and also not uniform standard for measuring contrast. Someone might rate the contrast ratio as 20,000:1, while another tester might only get 1,000:1.

Much depends on what is being measured. You can take a black field (0 IRE brightness) from a tuning disk or signal generator, and then a white field (100 IRE) from the same sources. In this case, we get a decent overall contrast, but it is not very relevant when real viewing video (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.

A good addition would be to measure contrast using the ANSI method. In this case, eight black and white fields are displayed on the screen in a checkerboard pattern. All measurements are averaged. This gives good show about display capabilities, and much more relevant to actual video. A particular problem is that the brightness of the white boxes can affect the measurements of the black squares. Thus, to do everything correctly you will have to spend a lot of time.

Conclusion

IN in this case There is no clear answer. This is exactly 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 the HDTV models you like is enough precise measurements given in TV reviews from competent sites. And the knowledge gleaned from this article will also be very useful in order to imagine what the potential capabilities of the TV are. the best way will reveal itself under viewing conditions in your home.

As with many TV selection guides, we can say the following. Much depends on the conditions in which you plan to watch TV. If you are a movie buff and watch TV in a dark room or at night, the increased contrast of plasmas will look very cinematic.

If you watch TV more often during the daytime, nothing can compare with LED LCD in terms of brightness. Somewhere between them are located LCD TVs with a local or zone dimming system of LED backlighting. They can present better "internal plot contrast" than conventional LCD displays, but with a sufficient margin in terms of light output.

No matter what kind of TV you have in your home, it is very important to set it up correctly, as the initial factory settings may not fully unlock the TV's full potential.

When talking about the contrast of a projector, first of all you should separate the contrast of the device itself and image contrast.

For example, to test a projector, I need to measure the contrast of the device itself, and when building home theater you need to know the contrast of the image, which consists not only of the contrast of the projector. In general, there are several ways to measure contrast, and the differences between them are not always obvious or intuitive.

What is contrast?

Another long introduction...

When talking about an image, contrast is the ratio of the brightness of white to the brightness of black.

To be pedantic, the “brightness” of the image (measured in foot-lamberts or nits) is measured from the screen, and there is also the luminous flux (lumens) or illuminance (lux), which is measured measuring device aimed at the projector.

All of these parameters can be used to determine contrast, but each has its own specifics, which will be discussed later.

The main thing for now is to understand the principle that we divide the “brightest” by the “darkest” - and get contrast. High contrast means high maximum brightness with "deep black levels". Low contrast is when the black color looks like gray, but the white color is not bright enough.

The peculiarities of our vision are such that there is a certain full range of brightness perceived by the eye with adaptation, and there is a range of brightness perceived without adaptation. For example, there is a story that pirates allegedly used an eye patch so that, upon breaking into the hold, they would have one eye already prepared for dark conditions. In other words, the eye is definitely not able to simultaneously cover the range of brightness that would include the darkness of the hold and the bright Caribbean sun on the deck - adaptation is required.

To create a contrasting scene at the projector, we, thank God, do not have to blind the viewer, although this is assumed by the HDR/UltraHD standards. For the familiar SDR, it is quite enough to repeat the brightness range that would be perceived by the eye as “contrast” without adaptation. It’s worth remembering here that SDR assumes that 100% white is the color against which you are this moment you read this text, and not the blinding light of some spotlight or desert sun in the viewer’s face.

I briefly inquired about the sensitivity of the eye. There is an opinion that without adaptation the eye perceives, in the language of photographers, “from 10 to 14 stops,” which in theory should correspond to a contrast (the ratio of bright to dark) from 1024:1 to 16384:1 (though I don’t know in which ones exactly) conditions).

1024:1 is usually not a problem for an entry-level DLP projector for a home, but 16,000 and more is definitely the top segment, although it is far from the limit of the projector’s capabilities. In general, there is nothing outrageous about creating a contrasting picture.

But right away important note. If I, as it were, propose to “prohibit the eye from using adaptation,” then let the projector’s specified contrast levels also be “fair” or “native.” The opposite of "native" is "dynamic" contrast, which is achieved using techniques such as automatic iris. In other words, we cannot see dynamic contrast in one image, but only sequentially - first on a dark, then on a white scene. And we should be able to see the “native” contrast on one stage.

Black depth

If we talk about contrast effects, then for starters we can separately mention the effect of brightness and black depth. It's clear that brightness is needed to make you believe you're on a sunny beach, or that the water is actually throwing reflections in your face. Especially high brightness is important in order to draw sunny weather...

The problem is that if there is a bright object, the eye will adjust to it and will be less picky about black. On a bright scene, even a “bad black” will look black, not only due to the adaptation of the eye, but also psychologically:

It turns out that we take two projectors with a contrast ratio of, for example, 2000:1. One will have deep blacks, the other will not, but will have extra brightness. That is, the level of black color should be discussed separately from contrast.

This suggests that the owner of an overly bright projector has two simple options: enjoy the high brightness, sacrificing blacks, or reduce brightness, improving blacks. For classic HD content there is a recommended brightness for the image, which in most cases is achieved at luminous flux 1000 lumens or less (in the appropriate picture mode). If, let’s say, the projector produces 2000 lumens in the exact mode, and your screen size is 90 inches (that is, small), then you should probably worry about reducing the brightness. For budget projectors, one of the options is lamp mode (normal/eco), while top models have a lamp mode for this. manual setting diaphragm, or fine adjustment brightness of the light source - for “laser manufacturers”. If you are the owner of a budget projector and want to reduce the brightness, then you can look towards gray screens, or even try attaching an ND (neutral neutral) filter to the lens. However, I can’t give any exact recommendations.

ANSI contrast

Let's move on to measurements.

ANSI contrast measured from the projector screen, that is, we are talking specifically about his brightness. To measure contrast using the ANSI method, display test image as chessboard(black and white squares). On this parameter A number of factors other than the projector's capabilities have a huge impact:

properties of the screen fabric;
distance from the walls and room size;
lack of background lighting;
quality of darkening walls and ceilings, etc.

In this regard, it is important to understand that ANSI contrast is used to evaluate not the projector, but home theater, that is, a projector + screen + room system.

The first thing that catches your eye when trying to display a black and white checkerboard in an unprepared room is that the light from the white checkers, reflected from the ceiling, returns to the black checkers, significantly degrading the black level and contrast level. In most films, it is the simultaneous depth of black and brightness of white that gives the picture realism and the immersive effect, creates quality content the impression of volume, three-dimensionality. Therefore, ANSI contrast is exactly what you need to evaluate a home theater.

However, compare projectors Using ANSI contrast is difficult. If the author of the comparison is ready to guarantee that all measurement conditions will remain unchanged throughout the years during which he will make reviews, then (probably) you can take his word for it. However, one reviewer's ANSI contrast will be difficult to compare with another reviewer's ANSI contrast.

Why is this parameter so popular when testing projectors? The answer is that it completely eliminates the dynamic contrast factor. By measuring contrast using a checkerboard pattern, we don't give the projector any chance to engage the auto iris, which can increase contrast by 100 times or more, darkening blacks. Projectors with a laser light source, for example, allow the light to be turned off completely at any time, producing perfect blacks. But this will be useless when testing for ANSI contrast.

Full On/Off contrast (full on/off)

If ANSI is “simultaneous” contrast, then Full On/Off is “sequential”, that is, black and white measured one by one. This eliminates the influence of white on black and in almost any dark room we can quite accurately measure the brightness of black and determine the contrast the projector itself, if the measuring device is pointed at the projector (although there should not be a significant difference compared to measuring light reflected from the screen).

Fundamental importance when using this method is whether the projector has auto iris or similar dynamic contrast enhancement methods (lamp, laser) enabled. If they are turned on, then the black color may be 100 times darker or more, and we will measure dynamic contrast. If all this is turned off, then we get native(“fair”) contrast. In any case, we must be 100% sure whether "black enhancement" is used.

What contrast is indicated by the manufacturer?

Most likely dynamic. If it’s native, the numbers will seem too low. For example, when an expensive projector has a contrast ratio of 2000:1, then this is most likely the native contrast.

Dynamic aperture is useful if implemented well. It is also useful to the manufacturer because it allows any contrast to be specified in the specifications. As for, in fact, the correct operation of the diaphragm, there is a lot of uncertainty. For example, at what brightness does it start to work? Or will it turn on if there is a very small bright area on the screen? There are a lot of nuances, and the apertures of expensive projectors usually work more quietly and accurately.

The native contrast of the projector is highly dependent on the color rendering mode. The highest contrast ratio is usually achieved in the brightest mode, as color correction and calibration is inevitable reduce maximum brightness, but the black brightness remains the same.

Here's an example: in the bright mode, the white is slightly green, and to create an accurate mode for watching movies, we reduce the brightness of the green, which ultimately gives us the correct shade of white (neutral, colorless). As a result, the brightness of white decreased due to the loss of excess green, while the brightness of black remained the same (as much excess light as the projector matrix let through, so much does it let through). As a result, the mode seems to be intended for cinema, and the contrast turned out to be lower than in the bright mode, intended for a lit room.

Illuminated room

Rooms without prepared surfaces have a significant impact on the black level, but any external light simply kills it. In this regard, if there is possible light pollution in the room, the black produced by the projector itself (black depth) becomes less significant the brighter the light, and the maximum brightness becomes more significant. As a result, for office and school projectors, if they are operated in the light, everything turns upside down. The contrast of the projector is no longer important (since it is measured in the dark), but the brightness is important, which will increase the level of real ANSI contrast.

Sometimes contrast in such conditions refers to legibility (for example, text). Minimum level contrast ratio, giving relative legibility is approximately 4:1, although an image with a contrast ratio of 7:1 or 10:1 can be called adequate. For office projectors, the quality of color rendering in the brightest modes is of particular importance, since poor color rendering on maximum brightness may force the user to switch to a less bright mode, losing contrast/legibility.

It is worth noting that, despite the fact that black can be considered lost in illuminated rooms, this does not prevent you from creating a beautiful and colorful bright image with an emphasis on illuminated objects.

Screen influence

There are several ways the screen can affect black levels. Speaking about the most budget-friendly solutions, we are unlikely to go far from choosing between the usual matte and gray screen. The latter equally absorbs “white” and “black”, and therefore is only suitable for removing excess brightness. As a result, black becomes darker, and white... also darker. If the projector does not have very high contrast, then this may be a suitable option if you want to use it in a dark room.

The next level is reflective screens. Unlike usual matte screens, scattering light evenly in all directions, these screens also have a small " mirror effect", or "glossy effect" in the sense that they reflect the light incident on the surface more directionally, according to the principle "the angle of incidence is equal to the angle of reflection." Therefore, the viewing angle of these screens is lower, as is the uniformity of brightness. But they tend to reflect unwanted light falling from the side not at the viewer, but “somewhere else,” as a result of which the black level improves (especially in rooms that are not ideal from the point of view of a home theater). As a trade-off for this, spectators must be positioned in a narrower area.

At the forefront of technology are multi-layer ALR (Ambient Light Rejection) screens. They “eat up” side light more effectively, although they are significantly more expensive - this is clearly not a solution for a budget home theater. Typically, it's also about reflecting or absorbing light coming from the side and enhancing light coming from the side of the projector.

demonstration of the effect of ALR screen fabric CineGrey 5D

Gamma correction

Gamma correction is what happens to the brightness of the projector between black and white. In other words, the projector's response curve to the signal. For example, what percentage of maximum brightness will the projector output if it is commanded to “show 10% brightness”? Answer: not 10%.

In a lit room, a sharper increase in brightness is required for dark shades (shadows) so that they are distinguishable and do not merge. If you use a projector set for a lit room in a dark environment, the detail of dark objects will be overly emphasized and the image will be look low-contrast. In order for the picture to look contrasty and natural, the gamma correction must be set correctly. You can read more about gamma.

Conclusion

I just wanted to say that the topic is extensive and this article will be updated. But that's all for now. Thank you for your attention!

Which TV screen contrast is better, dynamic or static?

Buying an LCD TV in a store is not an easy matter. You have to take into account a lot of different parameters, and the cost of the TV is not the first of them. In addition to the diagonal, type and country of manufacturer, it is recommended to pay attention to the specified contrast values of the picture displayed on the LCD TV screen. And if image quality is extremely important to you, then pay attention to how contrasting a picture a particular model can produce.

What is contrast?

What is the contrast ratio of an LCD TV? It's about about the ratio of the brightness of two points, one of which corresponds to the lightest, and the other to the darkest area. Simply put, by indicating the contrast of the TV image, the manufacturer shows how many times the lightest point of the screen is brighter than the darkest point of the screen that the LCD TV screen is capable of producing. Of course, it is impossible to determine the exact contrast parameters by eye. To determine the contrast, the TV must undergo a special test using high-precision instruments. This means that manufacturers who indicate certain contrast indicators have to take their word for it. Alternatively, you can read one of the reviews or testimonials on various sites and forums. Here we post unbiased information from users who tested this model LCD TV in person.

Types of Contrast

As we have already said, contrast can be not only static, but also dynamic. Static contrast, also called natural, will determine the capabilities specific model LCD TVs. Well, dynamic contrast can be achieved through the use of special technologies. Static contrast is taken from the brightness of an individual pixel viewed in a static (motionless) scene. That is, a still image is taken, in which the darkest and brightest points are selected, after which the accepted formula is used. Dynamic contrast is measured only after contrast enhancement technology is applied to the picture. LCD TVs have the ability to regulate contrast, focusing on the plot of the video being played back.

Benefits of Static Contrast

Of course, LCD TVs with high performance static contrast are valued much higher than those with high dynamic performance. And this is completely justified. It is enough to display a picture with white text on a black screen. A TV with high natural contrast will actually show white text and a black background.

As for a TV with dynamic contrast, white letters on a black background will appear gray. From this we conclude that televisions with high natural contrast will show more realistic regular video, which is highly appreciated by amateurs high-quality image. For example, in daylight a black car on the screen will be really black, but in the evening it will be possible to distinguish bright street lights without any problems. Approximately the same image, in terms of contrast, can be seen in modern cinemas.

TVs with perfect contrast

It is worth noting that in terms of contrast, the most realistic images were provided by kinescope TV models. But today, when HDTV is in fashion, CRT TVs are no longer produced. As a result, the “yellow jersey of the leader” has been handed over to LCOS home projectors with the highest natural contrast, among which JVC D-ILA devices stand out. Following them we can distinguish Sony devices SXRD. And only after them good contrast demonstrate modern plasma TVs.

Local dimming

IN last years Manufacturers of LCD TVs managed to introduce certain technologies that made it possible to achieve an acceptable level of contrast. Particularly impressive results were achieved through the use of LED backlighting with local dimming technology. Of course, you won’t be able to adjust every pixel; control is carried out only by a group of LEDs, but the result is more than worthy. Ideally, the backlight LEDs should be located across the entire screen. But manufacturers deliberately abandoned such models because they were too expensive and inaccessible to a wide group of consumers. Modern LCD TVs use edge lighting, in which LEDs are located at the top and bottom. The edge lighting can also work with local dimming technology. Edge-lit LCD TVs display impressive contrast when using local dimming.

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Image contrast describes the degree of contrast in a photograph. This dimensionless quantity, quantified by the ratio of the brightness of the lightest area of the image to the darkest.

Derived from the English Contrast ratio - a technical term used to determine the ratio between the strongest and weakest illumination of a reference screen when projecting white and black colors onto it.

Contrast– one of the main characteristics of the image, directly related to the brightness of the pixels.

As you increase the contrast of an image, the light areas (pixels) become lighter and the dark areas darker. As a result, pixels are redistributed due to the mid-tone range. Some of them turn into light, and some into shadow.

When the contrast of the image decreases, on the contrary, the mid-tone range expands due to the borderline highlights and shadows. Dark pixels become lighter, and light pixels become darker and partially transition into midtones.

A high-contrast image may contain no midtones at all. Conversely, a low-contrast image will have a predominantly gray color.

There are many images taken under unfavorable lighting conditions that have a faded, dull appearance. Such images need increased contrast.

Contrast shows how visually distinguishable certain areas (objects, items) of an image are. It directly affects the visibility of details and image clarity.

How to determine the contrast of an image

It should be noted that image contrast is a subjective value. Some people like contrasting images, while others like softer tones.

By analogy with optical contrast, which characterizes the distinguishability of an object from its surrounding background, the contrast of an image can be quantitatively defined as the ratio of the difference in brightness of light and dark areas to the light one.

K = (B 1 – B 2) / B 1

Here K is the contrast of the image, B 1 is the brightness of the lightest area, B 2 is the brightness of the darkest area.

The brightness of individual pixels in an image can be determined in Photoshop.

If K=1, we have absolute contrast. At K=0 there is no contrast. The image will be Gray background. Details will be indistinguishable.

True, this is only true for black and white images. They are characterized by bright contrast.

In a color image, objects that have the same brightness can be clearly distinguished due to color contrast.

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