Application of Curve Tool in Photoshop Color Correction
We are a big printing company in Shenzhen China . We offer all book publications, hardcover book printing, papercover book printing, hardcover notebook, sprial book printing, saddle stiching book printing, booklet printing,packaging box, calendars, all kinds of PVC, product brochures, notes, Children's book, stickers, all kinds of special paper color printing products, game cardand so on.
For more information please visit
http://www.joyful-printing.com. ENG only
http://www.joyful-printing.net
http://www.joyful-printing.org
email: info@joyful-printing.net
At present, pictures have become an important means of information transmission, but many pictures are not ideal in quality, such as layer compression, color cast, and contrast, mainly because these pictures come from poor picture discs and lower resolution digital cameras. And the scanner or the internet, so it is necessary to correct these pictures. The most widely used image correction software is Adobe's image processing software photoshop, and its leading position in the field of image processing has been accepted. Curve is an important color level correction tool in photoshop. Many people are unfamiliar with it. Here we will give a detailed introduction to its role in photoshop.
The Curve tool has a powerful image color grading correction function that provides any level of adjustment, and the gradation adjustment curve is at its core. It can not only adjust the main channel, but also adjust the individual monochrome channels. The Curve tool is more convenient than the Level tool when adjusting the color cast. The Level tool changes the level of the image by moving the light and dark buttons, which is more suitable for high-key and low-key adjustment of the image: the Curve tool can add some nodes to the adjustment curve and arbitrarily change the shape of the curve to produce corresponding level changes. The high, medium and low key have a good adjustment, which is much more powerful than the Level tool. If Level is a coarse adjustment, then Curve is fine-tuned. The adjustment of the Curve curve should be made for the characteristics of different originals, either linearly or nonlinearly.
Open the image\Adjust\Curve (shortcut Ctrl+M) in the photoshop menu bar to bring up the curve dialog box, as shown in Figure 1. You can see that the gradation adjustment curve is in the middle of the dialog box, its horizontal axis represents the gradation (input) of the original image, and the vertical axis represents the corrected gradation (output). By default, the two axes range from 0 (black) to 255 (white), and the curve in the axis is called the tone curve. The initial value (ie, the default state) has the same input and output values, so the gradation curve is a 45° straight line. The gradient bar below the tone curve is used to describe the gray value of the horizontal axis. In the lower right of Figure 1, there are three straw tools, black field, gray field and white field calibration pipette, which can realize the black and white field calibration of the image.
Curve can achieve the following three functions
1. Image level adjustment
The Curve curve can effectively adjust the depth of the image color, especially for the adjustment of some boring images. Let's take a look at an example to see how to use this tool to adjust the image hierarchy. Figure 2 is a boring image. The whole image is gray and seems to be raining. Therefore, the detail of the image is lost, and the contrast of the dark tone is too small and the level is insufficient. To do this, we need to widen the contrast of the dark tone, while increasing the overall brightness of the image, making the colors of each layer lighter. Open the curve dialog box, use the CMYK mixing channel as the adjustment object, pull down the curve, and adjust the parameters and results as shown in Figure 3. It can be seen that Figure 3 is obviously much better than the overall effect of Figure 2. The whole image is clearer, the details are more abundant, and the contrast is also opened.
2. Correct color cast
The Curve tool can correct the overall color shift of the image or the color shift of a certain tone, but the ability to correct the color deviation of a certain color is poor. Because it is the object of the channel, not the color of the object. Let's look at an example. Figure 4 is a picture of a woman. We know from the face that C2%M35%Y26%K0%, its M is larger than Y. There is a rule for the skin color of the characters: the color of the Oriental and Westerners is M and Y or the main color is red, containing a small amount of C and K. The difference is that the oriental skin color is yellowish, and the color of the skin is slightly larger than M; the color of the Westerner is slightly larger than that of Y; but their Y and M are generally less than 40%, so that the skin color can be reflected. White, especially for women, except for special circumstances. It can be seen that the figure in Figure 4 is an oriental woman, so its Y should be slightly larger than M, and Figure 4 is the opposite, so we need to lower the M in Figure 4, here we use Curve tool. Open the curve dialog box, select the magenta channel as the adjustment object, and pull down the curve to get the result we want. The parameters and results of the adjustment are shown in Figure 5. Compared with Figure 4, Figure 5 shows that the skin tone is slightly yellowish and appears whiter and more in line with the oriental skin color. The adjustment of the M version here will affect the gray balance of the entire image, so the adjustment is not too large.
3. Black and white field calibration
When determining the black and white field, it should be noted that the black field of the image should have sufficient density. The percentage of the dot is above 95%, which should be the darkest part of the image; the white field should be close to the net, and the percentage of the dot is below 5%. The whitest place in the image. Once a point is selected on the image as a black and white field, the brightness of the other pixels on the image will change accordingly. If a point is selected as a white field on the selected image, the percentage of the dots whose original brightness is higher than a is 0%, the level disappears, and the point whose brightness is lower than point a will increase the brightness with respect to point a. If the b point on the selected image is black, the percentage of the dots whose original brightness is lower than the b point is 100%, and the point where the brightness is higher than the b point lowers the brightness with respect to b. It can be seen that if the black and white field of the image is not properly selected, the brightness and color of the entire image will change. For example, in a woman wearing a white gauze dress, if a point is selected as a white point on the scarf she wears, the percentage of dots at that point is C27% M18% Y4% K0%. As can be seen from the percentage of its dots, this point is not the brightest point on the image, and contains more gray components. Therefore, the percentage of the dots of the skirt with higher brightness than this point is 0%, which becomes a white color, the level is lost, and the face of the character There is also a loss in the upper level. If you select a point on the white gauze of her chest as a white field, the percentage of dots at this point is Cll%M1%Y2%K0% compared with other pixels on the image. The uppermost point is the white point on the image, so the overall brightness of the image does not change much with respect to this point, and the brightness is only slightly improved. There is no loss in the level of the skirt and the face, the transition is natural, and the color of the face is whiter and more tender due to the increased brightness of the face.
The Curve curve can also be drawn as needed to make some special effects words, which we won't go into detail here. When using this tool, be sure to clarify your purpose, and then consciously adjust, do not arbitrarily adjust. Only by using this tool in practice can you have a deeper understanding of its function.