Data Management of Stamp Proofing

Normally, the size of the stamp is 30mm x 40mm, the scanning input accuracy is 400dpi, the photosetting accuracy is 4000dpi, and the output is 300 lines/inch, requiring extremely rich levels and infinitely varied colors in a very small range. The performance of stamp paper (90g/m2) is far lower than that of high-grade album paper (157g/m2). Therefore, the field density and dot gain rate required for proofing must be stable so that correct proofs can be seen during adjustment and adjustments can be minimized. The number of image data files reaches the goal of restoring the original.

(1) Data Management of Proofing

Offset proofing, gravure proofing and digital proofing must all be conducted in strict accordance with the requirements of color management, so that the provided proofs can be used as a reference value and serve as the basis for scanning, drawing adjustment, revision and editing, and final approval. Table 1 shows the data management of offset proofing, gravure proofing, and digital proofing.

Table 1 Data Management Contents of Offset Proofing, Gravure Printing, and Digital Proofing

(B) Basic Essentials of Adjustment

Faithful to the manuscript is the basic principle that should be followed when scanning and adjusting the length. External image files must first be typed digitally, and then adjust the image file data. After repeated adjustments and confirmation, the drawings will be revised to the subtle level, transition color, Brush strokes and small lines, etc. for more detailed trimming. The adjustment work is a comprehensive examination of personal qualities, which requires the operator not only to have a correct understanding and judgment of the input, but also to give a correct understanding of the output from the perspective of the printing process, as shown in Figure 1.

1. The idea and method of drawing

The idea of ​​adjusting the map should be based on the overall situation. The adjustment method is shown in Figure 2, as follows.

(1) Starting from the tone and level, the tone should not be too strong, and the richer the level, the better. It is necessary to consider the limited size of the stamps, the rational distribution of the bright tone, the proportion of the intermediate tone and the dark tone, and also the printing suitability of the paper.

(2) In order to make the color closer to the original, it can be achieved by lowering the saturation and making the color appear old.

(3) Ink and stamp paper The performance of the paper restricts the complete restoration of the original document. Therefore, the use of spot color ink is common in the stamp printing process, and some parts can only adopt the method of demarcating the area, and even separate multiple layers.

(4) The use of digital proofing helps reduce costs, shorten production cycles, and increase production efficiency.

Gravure and offset printing are two very different processes. The dot values ​​(recommended value) of bright and dark tone are completely different, the paper weight (90~250g/m2), coating, fiber (postage stamp paper, recycled postage card stock, The quality of postage and offset stamp paper, the type of ink, the status of the printing press, the printing sequence, the use of postage products, and the flexible collocation of spot ink (anti-counterfeit and colorless fluorescent ink, gold ink, silver ink, brown ink, Beige ink and gray ink are also different. The abnormal change of these factors (the root cause of rework) will interfere with the correctness of the adjustment. Therefore, the above processes must be managed data.

Photoshop image processing software is a common drawing tool, and various functions change endlessly. “Edit”, “Image”, “Layers”, “Selection” and other menus can be used in combination. The production process is improved and the technical level of the adjustment staff closely related.

2. Transfer steps

The steps to use Photoshop software to adjust the picture are as follows.

(1) Analyze the acceptance criteria for construction orders and read the workshop production process plan.

(2) Determine the maximum density of the spot color version (with reference to spot color patches or empirical values) and the tone between the dot value, spot color selection, and spot color.

(3) Organize customer-supplied electronic files, create a transfer folder and back up, select PSD or TIFF format as needed, use layers and constituencies (in order to maximize the level of extension) need to know the retouching staff. Analyze the electronic documents, inkjet samples, and manuscripts provided by the customer, and start plotting with the actual printing conditions.

(4) Postage stamps require the reproduction of as much graphics as possible in a limited size, and true reproduction of the three primary colors and spot colors. Lines, strokes, and subtleties also need to be coordinated with the retouching staff.

Gravure and Offset Due to the differences in paper, ink, plate, and printing equipment, the calibration values ​​of light and shade adjustments during plate making are completely different. In general, the printing of stamps is different from high-end exquisite albums. When high-grade exquisite albums are produced, the contrast and texture are emphasized. The tone curve of stamp reproduction is relatively flat, the black tone is long, and spot colors are often used.

(III) Ideas and Techniques of Retouching

The stamp production process can be roughly divided into two stages. The previous stage includes electricity, drawing and retouching. The latter stage includes proofing and printing. The proportion of retouching can vary, but it does play a crucial role. . The procedure for retouching is as follows.

(1) Analyze the acceptance criteria for construction orders and read the workshop production plan.

(2) Understanding the way of thinking and methods of drawing plans.

(3) Find out the relationship between layers, constituencies, and spot color channels.

(4) Correct understanding of screen structure, light and darkness, color proportions, and creative ideas.

(5) Within a limited size, the richer and richer picture and graphics layers are better, and the three primary colors and spot colors must be faithfully reproduced. Lines, strokes, and subtle levels need to be carefully picked up, dug, painted, traced, hooked, painted, and combined with Photoshop. The various functions are used flexibly.
(6) The production of anti-counterfeit spot color version, in accordance with the production and construction of a single large version.

Retouching is a very flexible job and requires the retouching staff to be able to skillfully use a variety of software (including anti-counterfeit software and spot color separation software), have certain art common sense, clear the printing process and printability, understand the adjustment The idea of ​​the plan seeks to accurately grasp the stamp's creativity.
Tuning and retouching are "soft" tasks. They must be implemented in a regulated environment, but they must be played and created. Small stamps are also a great place for talents! (Text / Xie Tiesheng)