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1. Unification of spot color names. In different software, the names of the two identical colors may be different. For example, FreeHand named PANIONEI 1F5 as PANTONE 1F5CVC or PANIONE 1F5CVV, while in PageMaker it was named PANTONE 1F5CV. In this way, when the FreeHand graphic object is placed in PageMaker for typesetting, there will be three names for the same color, and three printing plates will be generated during color separation output, causing output errors. Therefore, if the data file needs to be used in more than two kinds of software, before the integrated color separation output, it must be noted that the use name of the same spot color must be unified. The more common method is to use the color name in the software to determine the name of the same spot color in the color palette of various software to a unified name.
2. The angle of spot color screen. In general, spot colors are printed in the field, and dot processing is rarely done, so the angle of spot color screening is rarely mentioned. However, when using a light-colored screen with color registration, there will be problems with the design and modification of the screen angle of the spot color dots. If the spot color of a dot has overlapping areas with the color printed by other dots, the angle of the spot color screen must be considered. At this time, if the screen angle between the spot color dots and the screen angle of other colors is less than 30 degrees, there will be a screen hit or moire; if the angles overlap, it will cause ink overprinting problems, which will cause Severe distortion of print color. In addition, the screen angle of the spot color is generally preset to 45 degrees in the software (45 degrees are considered to be the most comfortable angles for human eyes, so that the dots can be arranged at the same angle as the horizontal and vertical lines can be reduced The ability of the human eye to detect dots), if a two-tone image or data file is printed with four colors and black (usually in four-color screen printing, the black dots are placed at 45 degrees, yellow is 0 degrees, (Magenta is 15 degrees, cyan is 75 degrees), and there are spot colors, or there are more than two spot colors, they will be output at 45 degrees during color separation and screening, so when using a light screen for spot colors, if It may be overprinted with other screen colors, you must open the dialog box of software color settings or print settings during color separation output, and modify the screen angle of spot colors.
3. Conversion of spot color to printing four colors. Many designers often use the colors in the spot color library to define colors and perform coloring when doing graphic design, and then convert them into CMYK printing four colors when separating colors. At this time, you should pay attention to three points: one is that the color gamut of the spot color is larger than the four-color gamut of printing. During the conversion process, some spot colors cannot be preserved for life and fidelity, and some color information will be lost; second, the output must be selected. " "Convert spot colors to four colors" option, otherwise it will lead to output error; third, don't think that the CMYK color value ratio displayed next to the spot color number allows you to reproduce the effect of the spot color with the same CMYK composition printing four-color ink ( If you can, you do n’t need a spot color.) In fact, if you do it in the same way, the obtained color will have a big difference in hue.
4. Trap processing of spot colors. Since spot colors are different from printing four colors (printing four-color inks generate intercolors by overprinting each other, that is, their inks are transparent), it is usually not used to generate an intercolor with the overprinting of two spot colors. Obtain very dirty color effects (of course there are exceptions, such as the intentional use of spot color overprinting to produce the third color required for superposition and mixing, this third color is full, thick and real, such as: spot color yellow The spot color that is modulated by imprinting is red, and the two colors are overprinted to produce a stable deep red color, which is often used as the cover of the book, etc.), so the spot color is generally defined without overprint (overprint) method. Keepaway). In this way, when using spot colors, as long as there are other colors next to the spot color graphics, you should consider making appropriate trapping treatments to prevent the occurrence of white border problems (the method of spot color trapping and related technical issues are more complicated, This is not repeated).
5. Color matching system for spot colors. When choosing a computer color matching system, first of all, it should be clear which is the spot color system and which is the CMYK four-color printing system, so as to know whether the color in the system you choose will have color conversion and whether it will be output during color separation There is color distortion. For example, the color matching systems commonly used in graphics software are PANTONE, TRUMATCH, FOCOLTONE, TOYO ColorFinder, ANPA-COLOR, RIC Color Guide, etc. Among them, TRUMATCH, FOCOL TONE and ANPA COLORR are based on the four-color printing system. Others The ones that belong to the spot color system (PANTONE system covers a wide range, both printing and spot colors). That is to say, in the spot color matching systems such as PANTONE spot color, TOYO Color Finder and RIC Color Guide, many of which have exceeded the printing four-color gamut and cannot be reproduced with four-color ink. The CMYK combination provided by the system The values ​​are only approximate.
So if you select the color in the spot color color matching system and output it as a printing four-color separation; or refer to the corresponding CMYK combination value of the spot color approximately displayed in the system and use these values ​​to replace the printing four colors The original spot color will definitely result in color distortion. Secondly, it should be understood that when the spot color color matching system does color separation processing, unless specifically set to convert the spot color into CMYK four colors for output, otherwise, each used Spot colors will be automatically divided into a color version independently. In the same way, after printing the colors in the four-color color matching system for coloring processing, when the color separation is output, it will automatically be based on the CMYK ratio of the color itself to the four printing plates without generating more Color version. Furthermore, it should be noted that in the bitmap environment, after the selected color (such as spot color) is used on the canvas, it will be automatically converted to the same color mode as the data file to which the color is applied (such as CMYK four-color mode) . Therefore, in the dot-matrix drawing software, spot colors must be intentionally added or specified (for example: add and define spot colors in Photoshop, there can be two situations: if the spot color is applied as a tone to the entire image , You need to convert the image to two-tone mode, and apply spot colors on one of the two-tone plates; if you use spot colors for specific areas of the image, you must create a spot color channel); and in the vector drawing environment, if Select or define a spot color, the color will always exist as a spot color attribute, unless the spot color attribute is specifically changed or converted into a process color (for example: a spot color added and defined in Iiiustrator, even if it is referenced to The data properties of this spot color will not be changed in other Illustrator data files or the data file using the spot color will be opened with other vector software, etc.)
6. The cost of spot color printing. In general, spot color printing is usually used for printing below three colors. If more than four colors are needed, CMYK four-color printing is appropriate. Because CMYK four-color printing is basically based on dot-overprinting, and spot colors are basically printed on the spot. Although spot colors are usually used only for local images, it is customary to double the price of ordinary printing inks when evaluating Estimated; in addition, if there are already four printing colors on the same layout, it is equivalent to one more color for printing, if the printing machine does not have extra printing units (such as printing machines with less than four colors or four-color printing machines) ), It takes twice as much time to print, and the cost is even higher.
In short, special care should be taken when using spot colors, otherwise it will not only cause color distortion, ruin your creativity and design, but also increase financial expenditure and unnecessary waste of time.
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