Printing FAQ (22-27)

22. In the color separation, when the image is transferred from RGB to CMYK, the naked eye can see some color changes on the screen. What is the reason? What is the effect on the image color?

A: When the image is converted from the RGB color mode to the CMYK color mode, some bright colors on some images will produce obvious changes, and this change is sometimes observable, and it will generally change from bright colors to dull ones. Some colors. This is because the color gamut of RGB is larger than the color gamut of CMYK, which means that some colors that can be represented in the RGB color mode are beyond the color range that can be expressed by CMYK after they are converted to CMYK. Replace with similar colors. Therefore, these colors produce more obvious changes. Actually, if there is a color exceeding the color gamut in the image of the RGB color mode, the Gamut Warning may be used for preview.

23, what is the color space? What is the significance of clarifying the gamut space?

We edit images in RGB, CMYK, and Lab, and the essential difference is working in different color gamut spaces. The color gamut refers to the range of colors that can be expressed by a certain color model, and also refers to the range of colors that can be represented by specific media such as screen display, printer output, and print copy. The color of the visible spectrum of the natural world forms the largest gamut space, which contains all the colors that the human eye can see. In the color mode, Lab has the largest gamut space. It contains all the colors in RGB and CMYK.

24. What is the best mode for designing the color mode of an image?

A: In Photoshop, the color modes of an image are RGB mode, CMYK mode, GrayScale mode, and other color modes. The use of any mode for designing image patterns depends on the end use of the design image. If the designed image is to be printed or printed on printing paper, it is best to use the CMYK color mode so that the color seen on the screen is close to the output printing color or the printed color. If the design is for electronic media display (such as web pages, computer projection, video, etc.), the color mode of the image is best to use RGB mode, because the RGB mode is more vivid and richer in color, and the picture is also better. And there are only 3 channels in the image, the data volume is smaller, and the disk space is less. If the image is gray, use GrayScale mode is better, because even if the image is expressed in RGB or CMYK color mode, it still looks neutral gray color, but its disk space is much larger. In addition, if the gray image is to be printed, if it is expressed in the CMYK mode, there are four editions of the film and the printing, the cost will not be great, and it may cause color cast problems when the gray balance is not well controlled during printing. When the ink volume is too large, color shifts occur in gray images.

25. How is gold and silver printed? What are the requirements for prepress design?

A: In the design, customers often require the use of gold and silver printing, because gold and silver can not be achieved by four-color printing, so their printing and technology have special requirements. When printing, gold and silver are processed according to spot colors, that is, they are printed with gold ink and silver ink. Therefore, the film should also be a spot-colored film. A film sheet is produced separately and printed separately.

In computer design, a color should be defined to represent gold and silver, and defining the color type as a spot color can meet the design requirements. Since gold, silver, and silver are opaque, gold and silver content can be set to be overprinted.

26, what is the spot color and spot color printing?

A: Spot color means that when printing, instead of printing this color by printing four colors of C, M, Y, and K, the specific color is used to print the color. Spot color inks are premixed by the printing factory or produced by the ink factory. For each spot color of a print, there is a special color version corresponding to the print. Using spot colors can make colors more accurate. Although the color cannot be accurately represented on a computer, the pre-printed color sample card of the standard color matching system can see the exact color of the color on the paper, such as the Pantone color matching system to create a very detailed color sample card .

For the non-standard spot color colors set in the design, the printing factory may not be accurately deployed, and the exact color cannot be seen on the screen. Therefore, if it is not a special requirement, it should not be easy to use a spot color of its own definition.

27. What are the commonly used color methods in computers? What is the best way to define a color?

A: Whether on a computer or printing, you need a way to describe different colors. The colorimetric method is also called a color model or a color model. There are many types of color models, each of which can describe colors from different angles, but different color modes are suitable for different occasions, and the accuracy is different.