Some issues that should be noted when using spot colors before printing

1, the unity of the spot color name in different software, for the exact same two color, the name may be different. For example, FreeHand named PANIonEI IF5 as PANTIONE 1F5CVC. 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 commonly used method is the color name in the tight 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 screen 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 the spot color of a dot has the overprint area following the colors printed by other dots, the spot color screening problem 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, it will cause the screen to generate moiré; if the angles overlap each other, it will cause ink overprint problems, which will cause prints The color 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 bi-tonal image or data file, it is printed with 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, green is 75 degrees,) there are spot colors, or there are more than two spot colors, then in the color separation screening will be 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 color to four-color printing

Many designers often use the colors in the spot colors to define the colors and perform the coloring when they do the graphic design, and convert them into the four-color printing of the CMYK during color separation. 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 beside the spot color pattern, trapping processing should be considered to prevent the problem of dew-white spots. (The method of spot color trapping and related technical problems are more complicated. Narrated).

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, the color area matching systems commonly used in graphic software include PANTONE, TRUMATCH, FOCOLTONE, TOYO ColorFinder, ANPA-COLOR, RIC Color Guide, etc., among which TRUMATCH and FOCOL TonET ANPA COLORR are based on a four-color printing system. 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 four-color color gamut, and cannot be represented by 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 the coloring process, the color-matching output will automatically follow the color's own CMY blending ratio to the four plates without generating more. The color version. Second, note that in the context of a dot-matrix diagram, the selected color (for example, a spot color) is automatically converted to the same color mode as the data file to which the color is applied (for example, CMYK four-color mode) after it is used on the canvas. . So in the dot matrix drawing software, for the spot color, it must be deliberately added or specified (for example, adding and defining a spot color in photoshop, there can be two cases: if the spot color is applied as a hue to the entire image , you need to convert the image to a two-tone mode and apply a spot color on one of the two-tone plates; if you use a spot color for a specific area of ​​the image, you must create a spot color channel; and in a vector drawing environment, When a spot color is selected or defined, the color will exist together as a spot color attribute unless the spot color attribute is specifically changed or converted to a process color (eg, a spot color added and defined in the liiusttrator, even if it is referenced In other Illustrator data files, data files that will use this spot color are opened with other vector software, and the color attributes of this spot color are not changed.)

6, the cost of spot color printing

Generally, spot color printing is generally used for printing below three colors. If four or more colors are required for printing, four-color printing of CMYK is suitable. Because CMYK four-color printing is basically based on dot overprinting, and using spot colors is basically printed in the field. Although the spot color is usually only used locally in the image, it is customarily used twice the price of ordinary printing ink. To estimate; In addition, if the same layout has four printing colors, it is equal to one more color for printing, if the printing press has no extra printing units (such as less than four color printing machines or four color printing machines. ), it will take twice as much time to print, and the cost will be higher.

In short, special care should be taken in the use of spot colors, otherwise it will not only cause color distortion, spoil your creativity and design, but also increase economic expenditure and unnecessary time waste.