Improve the contrast of the picture
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Photographs of scenes that are common in everyday life, such as street photos, people's photos, and landscape photographs, which always contain several important objects or colors. For such photos, they are usually set with highlights, dark tones, neutral grays, and skin tones. That is, you can adjust the beautiful picture and get better printing results.
But there are also other kinds of pictures, such as product pictures, animal pictures, food pictures, jewelry pictures, etc. The characteristics of these pictures are that one or two colors are the most important, occupying a large area of the picture; and other small parts It’s just the background. For such pictures, not only should the high light, dark tone, neutral gray, and skin tone be adjusted, but also the contrast of important objects in the picture should be increased.
Each image is a cat with very little background. This is acceptable if the picture is adjusted to make the cat clearer and the background loses some detail.
The white cat in the picture will occupy the brighter tone part of the Curves curve; the black cat in the picture will occupy the darker tone part of the Curves curve; while the gray cat will occupy the middle tone part of the Curves curve.
You can find out the exact range of tones in the Curves curve. Place the mouse on the highlights and shadows of each cat and record the numbers on the information panel. Another method is to use the Curves curve of a single channel, hold down the mouse to move on the picture, and a circle appears on the Curves curve to indicate the value of the mouse position.
The highlights and shadows in the picture are correct, using the curves shown to increase the contrast. We should carefully consider the impact of various curves on the picture cat.
There is a big difference between the cat picture in each column and the cat picture in each line. Each steep curve applies to a particular cat, increasing its contrast. However, the range of the tone in the other two cat pictures is flattened, the contrast becomes smaller, and the level is lost. The adjustment at this time is like shopping: on the one hand, you will buy things, on the other hand, you will lose money. Or use a better metaphor, like a transaction, get what you want, but you will lose something you don't want.
Each of the three curves will always adjust a good cat picture. From the second line below, the gray cat picture in the middle is well adjusted, while the other two pictures are the worst.
And why increase the curve of the gray cat picture contrast, will make the white cat picture and the black cat picture become so bad? The answer is a question of the range of the tone. Gray cat pictures have the largest range of tones (white cat pictures have the smallest range of tones), so it has the longest range in the Curves curve. When correcting, the area that needs to be lost is the most.
The brighter tonal part of the Curves curve A is steeper, suitable for adjusting the white cat picture, adjusting more details of the white cat, and increasing the contrast of the white cat;
Curves curve B has a steeper mid-tone part, which is suitable for adjusting gray cat pictures, adjusting more details of gray cats and increasing the contrast of gray cats;
The darker tone of the Curves curve C is steeper, suitable for adjusting the black cat picture, adjusting more details of the black cat, and increasing the black cat's contrast.
We can stipulate that the white cat picture is a bright picture; the black cat is a dark picture; the gray cat is a middle picture.
Most of the images contain both brighter and darker tones, but in a variety of ways. For example, a picture of a meadow, the grass is green. In CMYK mode, green is a mixture of yellow and blue. And in the green of nature, yellow still plays a major role. In the grass picture, the yellow is the most, the green is the second, and the magenta is the least.
In other words, in the grass picture CMYK four-color channel, the yellow channel is a dark tone picture, while the magenta channel is a bright tone picture.
For example, the yellow channel is a black cat picture, the magenta channel is a white cat picture, and the blue channel is a gray cat picture. You can use a similar curve to adjust this picture.
Three different curves are used to adjust three different cat pictures. This is why instead of using the main channel curve, only the single channel curve is used when adjusting the picture. Because we have seen the effect of using a curve to adjust the three cat pictures, it is not ideal.
In order to adjust the CMYK picture, it is necessary to recognize that it is not only to adjust a color picture, but to adjust four black and white pictures. Each frame can be adjusted individually, but the four images are mutually influential.
If the highlight in a picture is correct, the dark tone is 70C70M70Y70K. This value is reddish because there is not enough cyan ink. 80C is required instead of 70C. Therefore, adjustment is required.
The easiest way to think of this is to drag the 70C point on the curve up by 10 in the cyan channel; the second method is to drag the point in the upper right corner horizontally to the left, keeping a straight line and becoming steep. There are many other ways to make 70C 80C. Which one should I use?
If the goal is to adjust the value of 70 to 80, the above and each curve can be done, but they have different effects on each part of the picture.
In practical applications, there is no possibility that there will be so many choices, because there are four basic conditions for adjusting the picture, that is, the highlight is correct, the dark tone is correct, the neutral gray is correct, and the skin color is correct. If there is no neutral gray and skin tone in the picture, you can use any of these four curves. But most of the pictures are not like this, so there must be two or three of these four curves that are simply not used.
Which one can I use?
The curve chosen should be the most important area of the picture located in the steep part of the curve.
Since color images can be seen as an extension of larger, more complex, and more difficult to adjust black and white images, we use the above method to adjust the image.
In the CMYK curve, the tiger part (the brown part of the curve) is adjusted to be steeper, which helps to improve the detail.
When adjusting this picture, you also need to set the highlights and shadows. In this picture, there is an important object that occupies most of the area in the picture. We need to adjust the details of the tiger, which will lose some details of other areas.
Adjusting this picture is similar to adjusting the picture of the cat above, except that it is adjusted in four channels. The black channel is like a white cat picture, the green channel is like a gray cat picture, and the yellow channel is like a black cat picture. With this in mind, we can adjust the picture using a similar curve.
In the black channel, the tiger is in the bright part; in the cyan and magenta channels, the tiger is in the middle part; in the yellow channel, the tiger is in the dark part. By means of the color data displayed by the eyedropper tool and the information panel, the tiger is positioned on the Curves curve. The more accurate the positioning, the more accurate the color adjustment, and the less influence on the background. Adjust the part of the tiger on the curve steeper.
Most people choose the tiger and adjust it without affecting the background. No matter how careful you choose, this effect doesn't look very natural. Only the adjustment method of the Curves curve is the method applicable to the eyes.
We know that a color, because of the different colors around it, will be different when the human eye sees it. Please pay attention to the color of the water area that the tiger steps into. This is the example.
Only humans have the feeling of simultaneous visual contrast. When a tiger steps into a yellow pond with a yellow shore, we will notice a slight color change in the water.
After adjusting this picture, we not only improved the contrast of the tiger, but also changed the color of the water to make it greener. There may be many experts who say that this is simply noisy; there is no respect for the manuscript at all! Just because a tiger steps into the water, the water won't change color!
The civet cat in the manuscript is obviously an important object in the picture, but the snow scene cannot be ignored. The middle picture is to keep the snow scene and adjust the contrast of the civet cat to be larger. The picture below shows the loss of snow and the contrast of the civet cat.
The contrast of the civet cat image can also be used to improve the contrast of the tiger. However, in this picture, the civet cat has more ash components than the tiger, and all CMY channels are similar to the gray cat figure. If you apply the "S" shape curve in the three channels of CMY, the civet cat in this picture will get a lot of details, but the snow will be lost. And the snow scene is also very important in this picture.
So now the situation is that the more details of the snow scene loss, the more details of the civet cat. The more you want to improve the contrast of the civet cat, the more you have to adjust downwards in the Curves curve. The more you do, the flatter the snow landscape becomes. When adjusting this picture, you need to take care of both the civet and the snow, the brown and gray parts of the curve, and try to make both parts steeper. Obviously, the middle picture is much better than the picture above. Is the bottom picture better? Adjust the curves of the two pictures.
The range of civet cats on the curve is shown in brown, snow
The range of the scene on the curve is shown in gray. Note that in the curve below, the curve of the snow scene becomes flatter, which increases the contrast of the civet cat and loses the snow scene.
Picture adjustment experts always aim to improve the contrast of important parts by discarding a part of the hierarchy when adjusting the picture.
If the picture is a very complicated picture, you can't just rely on intuition, you have to undergo a careful analysis. Need to always write down the color data of some places on the paper. It takes more time to spend more time, because you can find a lot of useless colors and you can throw it away.
Let's first look at its highlights and dark tones.
The original is reddish. Using the curves in this figure to adjust, it also increases the contrast between the poolside road, the pool and the number.
Since we don't care if there are no dots on the shirt, it should not be used as a highlight. In fact, I did not choose a parasol as a highlight. I tried the recliner at a distance, 12C11M24Y. The dark tone does not have so many choices. Nothing else will be gray except that the recliner is neutral gray. The people in the picture are too small for us to accurately measure their skin tone.
However, there is a known color that we can refer to. Although we can't say exactly what color the tree in the picture is, it must be a greenish one.
This is not the case with trees in the manuscript. The typical value is measured as 57C64M100Y38K. This is a dark yellow, similar to orange, not green at all. We don't know how much to adjust, but we must reduce the magenta value and increase the cyan value.
When adjusting the Curves curve, we also need to consider increasing the contrast. The content of this picture is quite rich, and the stone sculptures on the edge of the swimming pool, trees and swimming pools are important parts to improve contrast. Position these objects on the Curves curve and adjust these parts to be steeper.
In addition to highlighting highlights, we also need to make the Curves curve steeper in these areas, and adjust the Curves curve in the magenta channel down.
Cyan is an unwanted color in the stone, so the brightest part of the Curves curve is flattened. The pool and tree are located between the mid-tone and the third-quarter tone, making this part steep and helping to increase the contrast between the two. The darker tone and the quarter tone will lose detail.
Magenta channels are difficult to adjust. If the tree is going to turn green, adjust its center down. However, in this case, the dark tone part will also turn green. We did this by moving the rightmost point above the Curves curve to the left, making the darker tonal portion of the Curves curve steeper. Unfortunately, this is not possible here. Some sunbathing people wear red shirts with a value of 90M or higher. If you move this point too far to the left, it will lose too much of its hierarchy. The highlights in this Curves curve become steeper, which is to adjust the stone carving.
Huang has little effect on the contrast. In this picture, it is adjusted steeply to create a color change in the pool. Since the pool and the stone are relatively small in yellow, this Curves curve is simpler than the other three colors. All you have to do is adjust the middle tone up.
Black is also easier. The tree is dark and the other objects are bright. And there are no other objects between the two. Therefore, the two ends of the Curves curve are adjusted to be steep, and the intermediate tone is adjusted to be flat.
It's important to remember that the way the image is digitally adjusted is good. But using the Curves curve to increase the contrast of the image will adjust many details of the image.