Photoshop Color Channel Example

PHOTOSHOP After learning this, we have to learn the boring color theory, because if we don’t learn it, it will be difficult to continue learning. Now we have encountered a difficulty: Color channel. When I first learned about channels, I have already said: When you open a photo (RGB mode), four channels will automatically be generated in the channel: the first is the RGB composite channel , the second is the red channel, the third is the green channel, and the fourth is the blue channel. What do these passages illustrate? What's the use? This has to start with the color mode. (If your channel is wrong, please go to "Image" and "Mode" first to see if this picture is in RGB mode. If not, click RGB.)
In order to analyze colors, people Various theories emerged. RGB is one of them, and it is also the most suitable one on the Internet. R stands for red in English; G stands for green; B stands for blue. Red, green and blue are the three primary colors of light. All colors are composed of these three colors. A color represented by a combination of the three primary colors (from zero to 255), for example: medium blue (R=100, G=156, B=200). In addition, black is without any light , so the values ​​of the three primary colors are all zero. (R=0, G=0, B=0). White is the strongest light of the three primary colors. (R=255, G=255, B=255). The figure below shows the production of black, white, red, green, blue, yellow, cyan, and magenta and their representation methods. These most basic values ​​​​are what we should remember.
Red: (R＝255, G＝0, B＝0) only red; Green: (R＝0, G＝255, B＝0) only green; Blue: (R＝ 0, G=0, B=255) only blue;
Yellow: (R=255, G=255, B=0) A mixture of green and red, no blue.
Green: (R=0, G=255, B=255) A mixture of green and blue, no red.
Product: (R=255, G=0, B=255) A mixture of red and blue, no green.
Black: (R=0, G=0, B=0) None of the three primary colors.
White: (R=255, G=255, B=255) All three primary colors are present.
Above we learned three primary colors, three combination colors, two special colors, a total of eight colors
Let’s talk about gray by the way. When the three values ​​are equal and are not zero or 255, it becomes gray. For example: (R=55, G=55, B=55). It can also be like this: (R=5, G=5, B=5), which must be gray. However, the larger the value, the lighter the color, closer to white, and of course, the smaller the value, the closer to black. The medium price gray is (R=127, G=127, B=127).


From this, we derive the concept of "
Color Wheel". This color wheel has a total of 360 degrees, starting from red and divided into 60 degrees. Turn the color wheel counterclockwise, red and green are 120 degrees apart, with a yellow Y sandwiched in between, and the range of yellow is smaller, indicating that yellow is a mixture of red and green. 120 degrees from green is blue, and the thin area in the middle is cyan C. Sandwiched between blue and red is the magenta color M. You can memorize the counterpart of each color: red versus blue, yellow versus blue, green versus green. We have to remember their arrangement:
Red, yellow, green, cyan, indigo, purple Plus black and white, the interaction of these eight colors will produce countless colors. The above is about the production and types of colors. This is called "hue". It is one of the three properties of color. The other two properties are saturation and brightness. Leave that for later. Hue refers to what kind of color. From now on, when we talk about changing hue, we mean changing one color into another color.
By the way: In the printing industry, the CMYK mode is used to represent colors. C: cyan; M: magenta; Y: yellow, K: black. One more black. The CMYK mode is exactly 60 degrees different from the RGB mode on the color wheel. It uses four values ​​from zero to 100 to represent color, such as (88, 23, 158, 15)
Now we return to the channel panel. There are red channels, green channels, and blue channels. In fact, the colorful colors of an RGB photo are composed of a combination of these three colors. PS decomposed their colors and placed them in these three color channels. When the three channels are combined, it becomes a colorful photo. We only need to slightly change one of the color channels, and the color of the entire photo will change.
To understand this further, let’s do an experiment. Here is a photo:


We can see four channels in the channel panel. Except for the RGB channel, when you click on one of the channels in turn, they are all black and white. It's just that the black and white of a few channels are a little different. In the channel, white means yes, black means no . Pay attention to her face. You can see that the face in the red channel is particularly pale, the green channel is worse, and the blue channel is the darkest. What is this indicating? Since the face is reddish, the face in the red channel is the whitest and the most red. In the red channel, the whiter the place, the stronger the red here. Green is also whiter, and there is more green. What color will red and green make? It's yellow. It's the color of your skin. Faces rarely need blue, so the blue channel is the darkest.
Just now we paid attention to the face, next we will pay attention to the mountains, rivers and sky behind. Let’s look at each channel again: now it’s the other way around, with the red channel being the darkest, the blue channel being the brightest, and green being the middle. The reason is that the background color is basically light blue. The contrast between the colors of the characters and the background in this photo is very eye-catching.
Next, you can try to turn off one color channel and only turn on two pairs of color channels, such as red and green, to see what color cast will appear? In the absence of a blue channel, the photo is yellowish, which is consistent with the "color wheel" principle mentioned earlier.
If we want to change the color of the photo, we can change the black and white of each channel separately.

For example: add a gradient from white to black to the red channel: look at the picture on the left, the word (red) behind the title bar refers to the red channel. Now you can see:

A gradient from light red to light blue appears on the left side of the photo. In the upper half, there is too much red, and in the lower half, there is too little red. Only a small part in the middle is consistent with the color of the river in the original picture.
You can try to paint black and white on each channel and see how it changes.
Let’s take a look again, what will happen if the blue channel is turned off? Due to the loss of blue, the picture can only have red and green, which combine to create a yellowish color. Hope this will give you a deep impression.

Okay, today, we didn’t do any examples, we just did a little experiment. But this lesson is very important. First of all, we got to know the three primary colors, plus black, white, and two of the three primary colors combined to form yellow, cyan and magenta. On this basis, I also got to know gray and learned the RGB representation of color. Learned more about the "Color Wheel". This color wheel is something we will often use in the future. Don't forget. The other two major attributes among the three major attributes need to be studied separately to fully learn the basic theory of color

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