You can use the curve->; Tone saturation, color selection of decoloring channel or layer->; Layer styles consist of gradient overlay and color overlay.

Color correction: it is to restore the original color of the picture.

Commonly used instructions in color correction:

Color scale and curve, color balance, hue/saturation, optional color, channel mixer (rarely used).

1, color scale and curve:

A, "color scale" is mainly used to adjust the lightness, darkness and contrast of colors, so as long as you think the canvas is too dark and too bright and the contrast is not obvious enough, you can consider using it to adjust the picture. The role of the black-gray-white triangle slider in the dialog window of "Levels" is that the brightness of the black slider will decrease when it moves to the right, and the brightness of the white slider will increase when it moves to the left. The gray slider controls the midtones. Moving to the left will increase the brightness, and moving to the right will decrease the brightness.

B. Curves: Similar to the Levels dialog box, the Curves dialog box allows you to adjust the entire tonal range of an image. However, the curve can be adjusted at any point in the range of 0-255, instead of using only three variables (highlight, dark and midtone), while keeping other values of 15 unchanged. You can also use curves to precisely adjust individual color channels in an image.

2, color balance:

For normal color correction, the Color Balance command changes the overall color mixture of the image.

To use the color balance command:

(1) Make sure that the composite channel is selected in the Channels palette. This command is only available when viewing composite channels.

(2) Open the color balance dialog box.

(3) Select "Dark Tone", "Intermediate Tone" or "Highlight" to select the tone range to be changed emphatically.

(4) Select "Keep Brightness" to prevent the brightness value of the image from changing with the change of color. This option can maintain the tonal balance of the image.

(5) Drag the slider to the color to be added in the image; Or drag the slider away from the color you want to reduce in the image.

The value above the color bar shows the color change of the red, green and blue channels. (For laboratory images, these values represent channels A and B.. ) The value range can be from-100 to+100. 3, hue/saturation:

This function is mainly used to control hue, saturation and brightness.

4. Optional colors:

Optional color correction is a technique used by high-end scanners and color separation programs, which increases and decreases the amount of printed color for each increased and decreased original color pixel in the image. Even if "Optional Color" uses CMYK color to correct images, it can also be used to correct RGB images and images to be printed.

Optional color correction is based on a table that shows the quantity of each printing ink used to create each primary color. By increasing and decreasing the number of printing inks related to other printing inks, you can selectively modify the number of printing colors of any primary color without affecting any other primary colors. For example, optional color correction can be used to significantly reduce cyan in green pixels of an image while keeping cyan in blue pixels unchanged. To use optional color commands, do the following: Make sure that a composite channel is selected in the Channels palette. Optional color commands are available only when viewing composite channels.

Opens the Optional Colors dialog box. Select the color you want to adjust from the color menu at the top of the dialog box. This group of colors consists of additive primary colors and subtractive primary colors, as well as white, neutral colors and black.

For the method, select an option:

Relatively change the percentage of cyan, magenta, yellow or black in the total. For example, if you add 10% from 50% magenta pixels, 5% will be added to magenta. The result is 55% magenta (50% x 10% = 5%). (This option cannot adjust pure anti-white light because it contains no color component. )

Adjust the color absolutely according to the absolute value. For example, if 10% is added from 50% of magenta pixels, the total amount of magenta ink will be set to 60%.

Note: Adjust the proximity between the color-based and the options in the color menu. For example, 50% magenta is between white and pure magenta, and the correct proportion mixture defined for these two colors will be obtained. Drag the slider to increase or decrease the pixels of the selected color.

The change of optional color instructions also has similar effects, such as the shadow of people's faces in the sun and the connection between blue sky and white clouds. If you use a medium-gray filter, you can distinguish them better and will not be confused because of the "color shift" between pixels. But the effect of these measures is difficult for ordinary people to see. Optional color command can obviously distinguish or improve the image color, but the operation should be moderate. It belongs to an expert-level advanced operation that understands photography. As long as the color that needs to be emphasized exists in the original information, we can be promoted in the "optional color" instruction.

5. Channel mixer:

The Channel Mixer command allows you to modify a color channel using a mixture of the current color channels. With this command, you can do the following: Realize creative color adjustment, which is not easy for other color adjustment tools.

Choose a different percentage from each color channel to create a high-quality grayscale image.

Create high-quality sepia tones or other color images.

Convert images in an alternate color space, such as YCbCr used in digital video.

Switch or copy channels.

In a word, "hue command" and "optional color" have strong exponential change characteristics, and we can play with all kinds of colors at will. Since we can make all kinds of colors, they can also correct all kinds of color casts at will, but no matter how we play with these commands, the premise is that the three primary colors and the recognition of color casts are excellent! The change of "channel" in color gradation instruction is different from that in "channel mixing" instruction, which is a single color "density" adjustment (proportion), while the color "channel" in color gradation instruction is the change of color level, that is, the change of color contrast, and the color information can change on any section; The "Optional Color" command can change the "black and white density" of a single color; In the Tone command, you can change the brightness of a single color. Therefore, the comprehensive correction of color deviation can be realized by using these instructions comprehensively.

Color matching: change a specific tone to form a tone picture with a different feeling.

Image processor has an essential understanding of the generation and change of color. So experts in color matching know how to adjust it at a glance. However, it is impossible to adjust a very satisfactory effect at one time. Such people are not experts, but experts among experts, which are rare in the world.

In PS, there are generally only two principles that can be used, namely, addition mode and subtraction mode. For example, the most commonly used RGB and CMYK are the representatives of these two modes.

Generally speaking, in order to mix colors quickly, you must be familiar with the following points:

First, how light is produced.

Second, saturation, hue and lightness.

3. How do colors change in additive mode and subtractive mode?

Fourth, the color wheel.

Master and deeply understand the above points, and pay more attention to practice at ordinary times. I believe you will also "know how much green has been added, how much red has been added and how much blue has been added!" Los Angeles.