PS teach you to understand CMYK color mode

We are all learning about RGB content, RGB color mode is the most basic color mode, so RGB color mode is an important mode. As long as the image displayed on the computer screen, it must be in RGB mode. Because the physical structure of the monitor is to follow the RGB. We also touch the grayscale color pattern, which has some of its own properties, so that it is also applied to the description of the channel. It will also learn about other applications.

In addition, there is a CMYK color mode is also important. CMYK is also called the printing color mode, as the name suggests is used for printing.

It has a big difference compared to RGB: RGB mode is a luminous color mode, you can still see the contents of the screen in a dark room;

CMYK is a kind of reflective color mode, how do we read the contents of the newspaper? It is the sunlight or light that shines on the newspaper and then reflects into our eyes before we see the content. It needs to be light from outside, if you can't read the newspaper in the dark Room.

Previously said, as long as the image displayed on the screen, is the RGB mode performance. Now add a sentence: As long as the image is seen in print, is the CMYK mode performance. For example, periodicals, magazines, newspapers, posters, etc., are printed out, then the CMYK mode of the.

Similar to RGB, CMY is the first letter of 3 printing ink names: Cyan cyan, magenta magenta, yellow yellow. And K takes the last letter of Black, and the reason for not taking the first letter is to avoid confusion with blue. Theoretically speaking, only need to cmy three kinds of ink is enough, three of them should be added together should get black. However, due to the current manufacturing process can not produce high purity inks, CMY added the result is actually a dark red. Therefore, it is necessary to add a special black ink to reconcile.

Click on the color palette button, select the "CMYK Slider" in the menu, you will see CMYK is a percentage to choose, the equivalent of the concentration of ink. The following figure:

Like RGB mode, CMYK mode also has a channel, and is 4, C, M, Y, K each one. In Photoshop, enter the following left image. Note that the image above is in RGB mode after the input of Photoshop. The color mode of the image and some other information can be seen from the title area of the image window. The title area displays the image name, scaling ratio, color mode, and number of color channels. The picture shows RGB/8, which means that this is an RGB-mode image with a color channel of 8 bits. The following is the right figure.

Only RGB channels can be seen in RGB mode. We need to manually convert the color mode to CMYK before we can see the CMYK channel. The conversion Image Color mode can be from the menu "image mode CMYK color", note that the color of the image may occur some changes, the principle of change in this lesson will be mentioned later. View the channel at this point, you will see the CMYK channels of gray image, as shown below 4.

CMYK channel grayscale and RGB similar, is a kind of content of the expression. RGB grayscale to indicate the brightness of the shade, CMYK grayscale indicates ink concentration.

But there is a different definition of the shades in the gray chart:

RGB channel grayscale image is higher brightness, black indicates brightness is lower. White indicates the highest brightness, pure black indicates brightness is zero.

CMYK channel grayscale is white to indicate that the ink content is lower, black means higher ink content, pure white means that there is no ink. Pure black means the highest ink concentration.

Use this definition to see the CMYK channel grayscale, you will see the concentration of yellow ink is very high, and black ink is relatively low.

When the image is delivered, it is generally necessary to make the gray scale of these four channels into film (called out), then make sulfuric acid paper and so on, then on the printing press.

The traditional printing presses have 4 printing rollers (image analogy, the actual difference), respectively responsible for printing cyan, magenta, yellow and black.

A piece of white paper into the printing press to be printed 4 times, first printed on the image of the cyan part, and then printed on magenta, yellow and black parts, in order to the following figure:

From the above order, you can obviously feel the effects of the addition of various inks.

In the printing process, paper transmission between the rollers, may be due to thermal expansion or other reasons for the displacement, which may be the original color of the place is not printed on.

In order to test the quality of printed matter, in the printing of various colors, will be in the paper blank place to print a + symbol.

If each color is overprinter correctly, only one + symbol will be seen on the final finished product. If there are two or three, it indicates that a overprint error has occurred and will result in a scrap.

Different use of printed materials for overprinter errors caused by the waste standards are also different. Newspapers such as lower quality print, + symbol error 0.5 mm or even 1 mm are allowed.

But the book, exquisite magazines, especially the map and other fine print, the standard of waste products will be much stricter.

Because of the problems that may arise in printing, we should pay special attention to the production of images used for printing.

For example, to draw a very fine 0.1 mm line, then if the Overprinter dislocation 0.1 mm, there will be two lines. So how to avoid it?

This time, you should avoid the use of color in a variety of colors mixed color. The following 2 figures:

The left and right are green, the left side of the green on the CMYK four colors have ingredients, then use this color to draw the line will be printed 4 times. And the green on the right only uses the C and y two colors, in the printing time as long as only be printed two times is OK. The latter's chance of overprinting is much lower than the former. Note that "as long as the printed two times" does not mean that only through two rollers, but also to go through 4, but only two of the rollers have images printed on it.

From this small example, when making a print, the color you use will affect the printing success rate of the finished product. If it is RGB mode, then there is no need to be careful about this problem, because the screen is not possible to have a overprinter error occurred.

Then we ordinary family use inkjet printer, what is the color mode? Will it have overprinter errors?

Previously said, as long as the print is CMYK mode, inkjet printer is also in accordance with the CMYK mode of work, which contains CMYK four-color cartridges (individual models will be more but the same principle), and printing presses similar. But inkjet printers do not produce overprinter errors, this is why? We said that the printing presses of paper to go in and out of 4 rollers, overprinter error is in and out between. The inkjet printer is a one-time print. So there is no overprint error.

How does the inkjet printer achieve a one-time print?

The inkjet printer arranges the multiple nozzles in turn. In this way, when printing, the first line of paper is sprayed on C, and then the paper moves forward one line, the original first line stopped under the M nozzle was sprayed with M-color, while the new blank second line is sprayed on the C-color. Then the paper moved forward, the line has been sprayed C, M is now parked under the Y-color nozzle, is sprayed with Y-color. And the second line was sprayed with M. The new blank third line is sprayed on C. Analogy

If you cancel printing when you print to half of the inkjet printer, you'll see an unfinished portion of the image at the edge, similar to the following figure.

Since the principle of inkjet printers is not complex, why does a large printing press not use such a printing method?

Because of the low speed of the printing, the nozzle needs to have a moving process on each line, which takes time if the large format of the paper takes longer. Newspapers and so on a large number of printed matter needs to be completed in a short period of time, so this printing method is powerless. And the precision is also less than the printing press. So there's a big difference between printing and printing. Print generally a small quantity, quality and speed requirements are not high. Common in personal and small office use. Printing is the opposite.

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