Common scene photos in ordinary life, such as street photos, people photos, landscape photos, which always contain several important objects or colors, for such photos, generally set their highlights, dark tones, neutral gray, skin tone That is, beautiful pictures can be adjusted to obtain better printing effects.
But there are also other types of pictures, such as product pictures, animal pictures, food pictures, jewelry pictures, etc. These pictures are characterized by one or two colors, which occupy a large area of ​​the picture; while others It ’s just the background. For such pictures, not only the highlights, dark tones, neutral grays, and skin tones should be adjusted, but also on this basis, the contrast of important objects in the pictures should be increased.
Figure 1 The adjustment diagram corresponding to each adjustment curve
As shown in Figure 1, each image is a cat with little background. If the picture is adjusted to make the cat clearer and the background loses some details, this is acceptable.
The white cat in the picture will occupy the brighter tone of the Curves curve; the black cat in the picture will occupy the darker tone of the Curves curve; and the gray cat will occupy the middle tone of the Curves curve.
You can find the exact tone range in the Curves curve. Place the mouse on the highlight and dark tone of each cat and record the number on the information panel. Another method is to use the Curves curve of a single channel and hold down the mouse to move on the picture. A circle will appear on the Curves curve to indicate the value of the mouse position at this time.
The highlights and dark tones in the picture were originally correct, use the curve as shown to increase the contrast. We should carefully consider the effect of various curves on the picture cat.
In the picture, there is a big difference between the cat pictures in each column and the cat pictures in each row. Each steep curve in (Figure 1) applies to a specific cat, increasing its contrast. However, the tone range in the other two cat pictures becomes flat, the contrast becomes smaller, and the level is lost. 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 analogy, like a transaction, get what you want, but also lose something you do n’t want.
Of the three curves, each one 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 increasing the contrast curve of the gray cat picture makes the white cat picture and the black cat picture so poor? The answer is a question of tone range. Gray cat pictures have the largest tone range (white cat pictures have the smallest tone range), so they have the longest range in the Curves curve. When corrections are made, the most areas need to be lost.
It can be seen from the effect of (Figure 1) adjustment:
The brighter tone part of Curves 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;
The middle tone part of Curves B is steeper, suitable for adjusting gray cat pictures, adjusting more details of gray cats, and increasing the contrast of gray cats;
The darker tone part of Curves C is steeper, suitable for adjusting the black cat picture, adjusting more details of the black cat, and increasing the contrast of the black cat.
We can specify that the white cat picture is a bright tone picture; the black cat is a dark tone picture; and the gray cat is a middle tone picture.
Most pictures contain both lighter tones and darker tones, but in a variety of ways. For example, a picture of grass, the grass is green. In CMYK mode, green is mixed by yellow and blue. And in nature's green, yellow still plays a major role. In the pictures of grass, yellow is the most, followed by green, 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, and the magenta channel is a bright tone picture.
As another example, the yellow channel is a black cat picture, the magenta channel is a white cat picture, and the cyan channel is a gray cat picture. You can use a curve similar to (Figure 1) to adjust this picture.
Use three different curves to adjust three different cat pictures. This is why the main channel curve is not used when adjusting the picture, but only a single channel curve. Because we have seen the effect of using a curve to adjust three cat pictures, which is not ideal.
In order to adjust CMYK pictures, it is necessary to realize that not only one color picture is adjusted, but four black and white pictures. Each frame can be adjusted individually, but the four frames affect each other.
If the highlight in a picture is correct, the dark tone is 70C70M70Y70K. This value is reddish because there is not enough cyan ink. Need to use 80C, not 70C. It needs to be adjusted.
The easiest way to think of it is to drag the 70C point on the curve upwards by 10 in the cyan channel; the second method is to drag the point in the upper right corner horizontally to the left to maintain a straight line and become steep. There are many other methods that can make 70C into 80C, as shown in (Figure 2). Which one should I use?
Figure 2 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, it is impossible to have 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 color in the picture, you can use any of these four curves. But most pictures are not like this, so there must be two to three of these four curves that are not used at all.
Which one can I use?
The selected curve should be the most important area in the picture located in the steep part of the curve.
Since color pictures can be seen as an extension of larger, more complex, and more difficult to adjust black and white pictures, we use the above method to adjust the pictures (Figure 3).
Figure 3 In the CMYK curve, the tiger part (the brown part in the curve) is adjusted to be steeper, which helps to improve the details.
When adjusting this picture, you also need to set the highlight and dark tone. 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, so that some details of other areas will be lost.
Adjusting this picture is also 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 cyan and pin channels are like gray cat pictures, and the yellow channel is like a black cat picture. Knowing this, we can use a curve similar to (Figure 1) to adjust this picture.
In the black channel, the tiger is in the bright tone; in the cyan and magenta channels, the tiger is in the middle tone; in the yellow channel, the tiger is in the dark tone. With the help of the color data displayed in the eyedropper tool and the information panel, locate the tiger on the Curves curve. The more accurate the positioning, the more accurate the color adjustment and the less the effect on the background. Adjust the tiger on the curve to be steeper.
Most people choose tigers for adjustment without affecting the background. No matter how careful you choose, this effect does not look natural. Only the adjustment method of Curves curve is the method suitable for eyes.
We know that for a color, due to the different colors around it, what the human eye sees will be different. Please note that the color of the water area where the tiger stepped in (Figure 3) is this example.
Only humans have the feeling of visual contrast at the same time. 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, not only did it increase the contrast of the tiger, but also changed the color of the water to make it greener. Perhaps there will be many experts saying that this is just a mess; this simply does not respect the original! Just because a tiger steps into the water, the water will not change color!
However, the fact is exactly that, when a tiger steps into the water, the water does change color. This is why the picture below (Figure 3) is more natural.
In (Picture 3), the tiger is the most important. You can adjust other objects to have a lower contrast and the relationship is not too great. In (Figure 4) it is completely different.
Figure 4. The picture above shows the raccoon cat in the manuscript. Obviously it is an important object in the picture, but the snow scene cannot be ignored either. The middle picture is to keep the snow scene and adjust the contrast of the raccoon cat to be larger. The picture below shows the loss of snow scene, increasing the contrast of the raccoon cat.
The contrast of raccoon pictures can also be used to increase the contrast of tigers. However, in this picture, the raccoon cat has more gray components than the tiger, and all the CMY channels are similar to the gray cat image in (Figure 1). If the "S" shaped curve is applied in the three CMY channels, the raccoon 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 are lost, the more details of the tanuki get. The more you want to increase the contrast of the raccoon cat, the more you need to adjust downwards in its Curves curve. And the more this is done, the snow level becomes flatter. When adjusting this picture, you need to take care of both the raccoon cat and the snow scene, that is, the brown and gray parts of the curve (Figure 5), and try to make both parts steeper. Obviously, the picture in the middle (Figure 4) is much better than the picture above. And is the bottom picture better? Adjust the curve of these two pictures as shown in (Figure 5).
Figure 5 Adjust the curve used in Figure 4. The range of the raccoon cat on the curve is shown in brown, and the range of the snow scene on the curve is shown in gray. Note that in the following curve, the curve of the snow scene part becomes relatively flat, which improves the contrast of the raccoon cat and loses the snow scene.
The image adjustment expert always adjusts the image by throwing away some layers to achieve the purpose of improving the contrast of important parts.
If the picture is a very complicated picture, it must not be based on intuition, but must be carefully analyzed. It is necessary to always write down the color data of some places on the paper. It is worthwhile to spend more time, because you can find many useless colors, you can throw it away.
Let's analyze (Figure 6), first look at its highlights and dark tones.
Figure 6 The picture above is the original, reddish. Using the curve in this figure to adjust, it also increases the contrast for the road next to the pool and the pool.
Since we don't care if there is a dot 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 farther away, 12C11M24Y. Dark tone doesn't have so many options. Apart from the neutral gray recliner, nothing else will be gray. The person in the picture is too small to measure its skin color accurately.
However, there is a known color that we can refer to. Although we cannot tell exactly what color the tree is in the picture, it is definitely a greenish color.
This is not the case with the tree in the manuscript. The measured value is 57C64M100Y38K. This is a dark yellow, similar to orange, not green at all. We don't know how much to adjust, but certainly the magenta value needs to be reduced and the cyan value needs to be increased.
When adjusting the Curves curve, we also need to consider the need to increase the contrast. The content of this picture is quite rich. The swimming pool, trees, and stone carvings on the edge of the swimming pool are important parts to improve the contrast. Position these objects on the Curves curve and adjust these parts to be steeper.
In addition to brightening highlights, we also need to make the Curves curve steeper in these areas, and we can adjust the Curves curve in the magenta channel downward.
Cyan is an unwanted color in stone carvings, so the brightest part of the Curves curve is flattened. The swimming pool and the tree are located between the middle tone and the third quarter tone, making this part steeper and helping to increase the contrast between the two. Darker tones and quarter tones lose detail.
The magenta channel is more difficult to adjust. If the tree is going to be greener, the center needs to be adjusted downward. However, in this case, the darker parts will also turn green. We did this by moving the upper rightmost point in the Curves curve to the left, making the darker tones on the Curves curve steeper. Unfortunately, this is not yet possible here. Some sunbathing people wear red shirts with values ​​of 90M or higher. If you move this point too far to the left, it will cause too many levels of loss. The highlights in this Curves curve become steeper to adjust the stone carving.
Huang has little effect on contrast. In this picture, it is adjusted steeply to produce a color change in the swimming pool. Because the pool and stone carvings have relatively few yellows, this Curves curve is simpler than the other three colors. All that needs to be done is to adjust the middle tone up.
Black is also easier. The tree is dark, and other objects are bright. And there are no other objects in between. Therefore, adjust the two ends of the Curves curve to be steep, and adjust the middle tone to be flat.
It should be remembered that the method of digital adjustment of pictures is good. But using Curves curve to increase the contrast of the picture will adjust many details of the picture.
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