Precautions on the use of spot colors should pay attention to some issues

1. The unity of spot color names. In different software, the names may be different for the exact same two colors. For example, Free Hand named PANIonEI 1F5 PANTONE 1F5CVC or PANIONE 1F5CVV and PageMaker named PANTONE 1F5CV. In this way, when FreeHand graphic objects are placed in PageMaker, the same color will have three names. When the color separation is output, three printing plates will be generated, 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 based on the name of the color in the distribution software, and the name of the same spot color is renamed as a unified name in the palette of various software.

2. Spot color screening angle. In general, spot colors are printed in the field, and they are rarely processed at the outlets. Therefore, the point of spot color screening is rarely mentioned. However, when using a lighter mesh color, there will be problems with the design and modification of the spot color screen dot. If there is an overprint area between the spot colors of the outlets and the colors printed by other outlets, the issue of spot color screening must be considered. At this time, if the angle formed by the spot color screen's screen angle and other color screen angles is less than 30 degrees, collision or moiré will occur; if the angles overlap each other, ink overprint problems will result, which will result in The color of the print is seriously distorted. In addition, the screen angle of spot colors is generally preset to 45 degrees in software (45 degrees are considered to be the most comfortable angle for human eyes, so that the dots can be arranged in the same direction as the horizontal and vertical lines. The ability of the human eye to detect dots, if it is a two-tone image or data file, it is printed in four colors and black (usually in four-color screen printing, the black dot is placed at 45 degrees, yellow is 0 degrees, Magenta is 15 degrees, blue is 75 degrees), there are spot colors, or there are more than two spot colors, when the color separation screen is output at 45 degrees, so when using shallow network for spot colors, if There may be overprinting with other screening colors. You must open the software color setting or print setting dialog box when the color separation is output to modify the spot color screening angle.

3. The conversion of spot colors to printing four colors. Many designers often use the colors in the spot color library to define colors and perform coloring when they do graphic design. In color separation, they are converted into CMYK printing four colors. At this time, pay attention to three points: First, the color gamut of the spot color is larger than the color gamut of the printing. In the conversion process, some spot colors cannot be faithfully completed, and some color information will be lost; second, the output must be selected. Spot color conversion becomes a four-color selection, otherwise it will result in an output error. Third, do not assume that the CMYK color numerical value displayed next to the spot color number allows you to reproduce the spot color with the same four-color ink of the same CMYK composition ( If you can use it, you will not need to use spot colors. In fact, if you do so, the resulting color will have a large gap in hue.

4. Spot color trapping. Because the spot color is different from the four-color printing (printing four-color inks to generate inter-color printing on each other, that is, the ink has transparency), it is not usually used to generate a color between two spot colors, which is intuitively speaking. Get a very dirty color effect (of course there are exceptions, such as the intention in the design of the use of spot color overprint processing to produce the required, superimposed blend of the third color, this third color is full, thick and real, such as: spot color yellow On-press embossed spot color red, two colors superimposed to produce a steady dark red, often used as a book cover, etc.), so the definition of spot colors, generally do not use overprint (Overprint) but to use empty ( Keepaway). In this way, when spot colors are used, as long as there are other colors next to spot color patterns, appropriate trapping should be considered to prevent the problem of dew-white spots. (The method for trapping spot colors and related technical issues are more complex. This is not repeated).

5. Spot color matching system. When choosing a computer color matching system, first of all, it should be clear which are the spot color systems and which are the CMYK four-color printing systems, so as to know whether the color you choose to use in the system will have color conversion and whether it will Color distortion occurs. For example, color matching systems commonly used in graphic software include PANTONE, TRUMATCH, FOCOLTONE, TOYO Color Finder, ANPA-COLOR, RIC Color Guide, etc., among which TRUMATCH, FOCOLTONE, and ANPA COLORR are systems based on four-color printing. Others All belong to the system of spot colors (the PANTONE system covers a wide range of colors, both process and spot colors).

That is to say, in spot color matching systems such as PANTONE spot colors, TOYO Color Finder, and RIC Color Guide, many of these colors have exceeded the printing four-color color gamut and cannot be reproduced with four-color inks. The system provides CMYK combinations. Values ​​are only approximations. So if you have selected the colors in the spot color matching system and printed them in four-color printing, or referenced the corresponding CMYK values ​​that the spot colors displayed in the system, and used these values ​​to replace the four-color printing. The original spot color, the result will definitely lead to color distortion; Second, it should be understood that the spot color matching system when doing color separation processing, unless specifically set to convert the spot color to CMYK four colors, otherwise, each used Spot colors are automatically divided into a single color version. In the same way, after printing the colors in the four-color color matching system for coloring, the color output will automatically follow the color's own CMYK ratio to the four plates without generating more. The color version.