The basic essentials of stamping and retouching of stamps
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Typically, the size of the stamp is 30mm x 40mm, the scanning input accuracy is 400dpi, the illumination accuracy is 4000dpi, and the output is 300 lines/inch. It requires extremely rich levels and endless colors in a very small range. Stamp paper (90g/m2) is far less expressive than high-end book paper (157g/m2), so the field density and dot gain rate of the proofing must be stable, so that you can see the correct proof when you adjust the map and minimize the adjustment. The number of times the image data file is used to restore the original.
Proofing data management
Offset proofing, gravure proofing and digital proofing must be carried out in strict accordance with the requirements of color management, so that the provided proofs have reference value and serve as the basis for scanning, mapping, retouching and editing and final approval. Table 1 shows the contents of the data management of offset proofing, gravure proofing, and digital proofing.
Table 1 Data management contents of offset proofing, gravure proofing, and digital proofing
Proofer Type Plate Type Paper Type Ink Brand Proof Blank Plate Temperature Table Pressure Test Strip
Printing machine model Light source Vacuum pumping Exposure time Developing time Developing temperature 2% 25% 50% 75% 95%
Y M C K 75% 2% 50% 95%
Density/increase rate
Gravure Model Solvent Paper Type Ink Brand Proof Data Plate Roll Specifications Printing Pressure Squeegee
Electric engraving machine model Light source Electric engraving C, M, Y, K data Electric engraving needle model Electric engraving needle angle 2% 25% 50% 75% 95%
Y M C K 75% 2% 50% 95%
Density/increase rate
Digital proofing machine Resolution Zhang Zhang type Ink brand Nozzle diameter Proofing software Proofing speed
Digital proofing machine C, M, Y, K data INK ICC profile PAPER ICC profile 2% 25% 50% 75% 95%
Y M Y K 75% 2% 50% 95%
Density/increase rate
The basics of the map
Faithful to the original is the basic principle that should be followed for scanning and adjusting the length. For external image files, you must first make a digital sample, then adjust the data of the image file. After repeated adjustment and confirmation, the image will be retouched. For subtle levels, transition colors, Brush strokes and small lines are finely trimmed. The mapping work is a comprehensive examination of the personal qualities, which requires the operator not only to have a correct understanding and judgment on the input end, but also to give a correct understanding of the output from the perspective of the printing process.
1. Tweaking ideas and techniques
The idea of mapping should start from the whole, and the mapping method is shown in Figure 2, as follows.
(1) Starting from the tone and level, the tone can not be too hard, the richer the layer, the better. Consider the limited size of the stamp, the reasonable distribution of the bright tone, the proportion of the middle and the dark tone, and the printability 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 old.
(3) The performance of ink and stamp paper limits the complete restoration of the original. Therefore, the use of spot color inks is not uncommon in the stamp printing process, and some parts can only adopt the method of selecting the area, and even divide multiple layers.
(4) Using digital proofing can help reduce costs, shorten production cycles, and increase production efficiency.
Gravure and offset printing are two distinct processes. The dot values (recommended values) for bright and dark adjustments are completely different, the basis weight of paper (90~250g/m2), coating, fiber (postage paper, recycled postage card paper, The quality of the postage seal, offset stamp paper), the type of ink, the state of the printing press, the color sequence of the printing, the use of postage products, and the flexible matching of the spot color ink (anti-counterfeit colorless fluorescent ink, gold ink, silver ink, brown ink, The beige ink and the gray ink are also different. The abnormal changes of these factors (the root cause of the repair) will interfere with the correctness of the map. Therefore, it is necessary to carry out data management of the above processes.
Photoshop image processing software is a commonly used mapping tool. Various functions are infinitely varied. The menus such as “Edit”, “Image”, “Layer” and “Selection” can be combined. The perfection of production technology and the technical level of the planners closely related.
2. Tuning step
The steps to adjust the picture using Photoshop software are as follows.
(1) Analyze the acceptance criteria of the construction sheet and read the production process plan of the workshop.
(2) Determine the maximum density of the spot color version (refer to the spot color block or experience value) and the dot value between the dot value, the spot color selection, and the spot color.
(3) Organize the electronic files provided by the customer, create a map folder and back up, select the PSD or TIFF format as needed, and use the layers and selections (in order to maximize the level). Analyze the electronic documents, color spray samples and originals provided by the customer, and start the adjustment of the picture in combination with the actual printing conditions.
(4) Stamp printing requires reproduction of the richest graphics layer in a limited size, and to truly reproduce the three primary colors and spot colors, lines, strokes, and subtle levels also need to cooperate with the retouching personnel.
Gravure and offset printing are different for paper, ink, plate and printing equipment, and the calibration values for light and dark adjustments are completely different. In general, stamp printing is different from high-end exquisite albums. When making high-end exquisite albums, it emphasizes contrast and texture. The stamps of the stamps are relatively flat, the black tone is very long, and the spot colors are often used.
Thoughts and techniques for retouching
The stamp production process can be roughly divided into two stages. The previous stage includes electricity, map and retouching. The latter stage includes proofing and printing. The proportion of retouching can be large or small, but it does play a finishing touch. . The steps for retouching are as follows.
(1) Analyze the acceptance criteria of the construction sheet and read the workshop production plan.
(2) Comprehend the ideas and techniques of mapping.
(3) Find out the relationship between layers, selections, and spot color channels.
(4) Correct understanding of the structure of the picture, the relationship between light and dark, the proportion of color and creative ideas.
(5) Within a limited size, the richer the image hierarchy, the better the three primary colors and spot colors must be reproduced. The lines, strokes, and subtle levels need to be carefully scooped, dug, drawn, drawn, ticked, painted, and combined with Photoshop. Various functions are used flexibly.
(6) Make anti-counterfeiting spot color version, and make a large version according to the production construction.
Retouching is a very flexible job, requiring retouchers to be proficient in using a variety of software (including anti-counterfeiting software and spot color separation software), with a certain art common sense, clear printing process and printability, understanding The idea of the figure is to accurately grasp the creativity of the stamp.
Tutorial and retouching are “soft” jobs, which must be implemented in a regulated environment, but they must be played and created. Small stamps are also a great place to display talents!