How to Use Spot Color in Designing a Plate (Part 2)

Set spot colors with desktop plate software

1. PageMaker, CoreIDraw, or FreeHand

The spot color setting of these softwares is relatively simple, as long as the spot color ink (Spot CoIor, nk) can be selected in the color setting, but it is better to use the spot color of the Pantone color library, because it is more popular, software and corpse The Pantone Library has better support and Pantone spot color inks are also easy to purchase. The trapping of spot colors is best set manually, because the trapping options for spot colors in such software are not well-understood (non-professionals try not to use them). And you can't see the results on the screen. The questions in the settings will only be visible when you wait for the film. When manually setting, it is necessary to add an edge line to the overprinted solid color patch and set the edge line to be overprinted. At the same time, the choice of the trapping value (edge ​​width) is more important, too small does not work, too big there will be a clear border, affecting the appearance. Generally, the trapping value is determined by the printing machine's overprinting accuracy and paper condition. For example, when printing with high-quality coated paper and high-precision printing machine, only the trapping value of 0.08-0.10 mm is needed, and vice versa. Increase but do not exceed 0.25mi.

The setting of the network cable angle does not need to be considered in the software. It can be notified that there is a spot color version in the file and the output center is set. If it is a large version of the document, you must add register lines, but you must select the set color of the software.

2. Photoshop

Photoshop's spot color production is more complex, to grasp a few key points.

(1) There are mainly four methods for creating a spot color channel.

1 Select “New Spot Channel” from the drop-down menu of the channel panel, select the color and density in the pop-up dialog box, and then operate on the spot color channel.

2 Create a new spot channel through the selection. Remove or select the image area (generate the selection), select the "New Spot Channel" command in the channel panel menu, select the color in the pop-up dialog box (same as 1).

3 Convert the alpha channel to a spot color channel. First select the alpha channel to be converted, then select “Channel Options” from the channel panel drop-down menu or double-click the alpha channel, select the spot channel in the “Channel Options” dialog box; change the desired color and name . Note that the pop-up color box is the normal color picker box. If Pantone color is needed, click the "Custom" button, switch to the "Custom Color" box, and select the desired spot color or Define the color.

(2) It is best not to use the trapping function in Photoshop, so as not to affect the picture color. The author proposes to manually set trapping, and you can see the effect after you finish it. There are two methods: First, load the spot color channel selection on the image of CMYK mode, modify or shrink 1 to 2 pixels under the selection menu, and then fill in white; second, remove the same size as the spot color range. After the figure part, cancel the constituencies and expand the scope of spot colors.

(3) If there is a spot color channel in Photoshop, the format of the stored file is very important, and it must be stored in DCS 2.0 (*.EPS) format in order to send out the correct spot color in other imposition software. DCS 2.0 format supports multi-channel files, and CMYK files with one A, ph臼 channel and multiple spot channels, including low-resolution display images for positioning and rich-resolution images for color separations The following is a good example

In Photoshop, select Photoshop DCS2.0 (*.EPS) format after OK. The system defaults to the "spot color" option. In the DCS 2.0 Format dialog box, select "Sweat (8 bits per pixel)" in the "Preview" item and select "Single file with color composite (72 pixels/inch)" from the DCS pop-up menu. Select ASCII from the Encoding pop-up menu instead of the "Halftone Screen", "Include Transfer Function", and "Image Interpolation Method" options. If the file contains vector data, select Include Vector Data. The specific explanation is as follows.

Preview: Select "8-bit/pixel" for viewing, layout positioning is also more accurate. The DCS format file is a low-resolution preview file that can display CMYK four-channel files or spot color channel files. However, when storing files, it is important to put all the files in a directory for distribution.

Encoding: Different encodings can affect file size and processing time, but also affect compatibility. ASCI, "Identity of mouth is a common coding method, and it is lossless coding. Binary is a more compressed form of ASCII, more efficient than ASCII, and its files are smaller than ASC, files are smaller, and processing speed is faster, but considering ASCII, the compatibility is stronger, so choose ASCII.

Transfer function: The method of controlling the ink concentration by means of a curve is generally based on the specific conditions of the printing plant, and it is not recommended.

Vector data: When the layer contains images of vector data such as paths, text, and graphics, it can have better output. Using this option for saving will make it possible for other programs to use vector data.

Image Interpolation: When this option is selected, the system can resample the image when it is output to eliminate aliasing.

In addition, when the output center is connected to a distribution document made with the above software, it is necessary to figure out what color printing is. If it is multi-color printing (spot color printing), be sure to pay attention to the correct setting of spot color. Incorrect documents are corrected or returned to customers to make standard documents.

Henan No. 2 Xinhua Printing Factory Liu Caiqin

Source: Print Technology 2005, 10 (Publishing and Commercial Printing)