Drafting method and control
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In the printing industry, what we must know is that the final product is a printed copy based on visual impressions. Subjective visual judgment is inevitable, because most reproductions are no longer a copy of the manuscript. Although some aspect of the relationship between the original and the copy can be expressed in a measured manner, this cannot be an indication of the overall acceptability of the copy. Therefore, in addition to measurement, visual judgment becomes the basic requirement of most color reproduction systems, and this requirement can be achieved by color proofing. It is important that the draft is to simulate the final printing effect as accurately as possible. This is critical for a successful color reproduction system.
Definition of standard draft
A color proof that correctly reflects the final print production, so the closer the equipment and materials used in the drafting are to print production, the more effective it is.
Relationship between drafting and printing
From a production point of view, color printing is a process based on the principle of dot coloring, which requires strict precision and stable repeatability. However, there are many factors that affect the color of printing, such as the characteristics of paper, ink thickness, printing pressure, air humidity, and even the quality of plate making. The increase or decrease of each factor will affect the quality of the printed color.
Generally speaking, the manuscript provides the following three functions: First, it is used to check the effect of color separation plate making to determine whether the color of the picture is processed correctly and to provide a basis for the revision. Second, it is used to check the technical requirements of the registration and dot gain of the film as a reference for actual printing. Third, as a communication tool, the customer is signed and confirmed before printing, and is the standard for receiving goods in the future.
Definition of digital proof
Computer files are directly used to create images or sheets by color-generated devices. The purpose is to simulate the effect of final printing production, called digital proofing; there are Soft proofing and Hard copy proofing.
Soft proof
Use a calibrated computer screen to preview the effects of print production, called soft proofing. Currently used for content proofreading and color correction work; also useful for remote soft proof.
Drafting stage
Drafting may be required at different stages of the copying process; in the design phase, called Content proof, only the layout or layout of the layout is evaluated or checked. Contrac proof, on the other hand, needs to simulate the final effect on the printed matter as a confirmation target between the printer and the customer.
Contract drafting requirements
If it is a draft for analog printing production, then it must be similar to the specific printing characteristics; this can be summarized as the following three basic requirements, in addition, whether they are stable and economical.
1. The substrate used is the same as in printing, or its appearance is the closest match.
2. To accurately simulate the color effect of printing.
3. To accurately simulate the tone change.
Use of contract drafting
Printing buyers and printers sign a printing contract based on the same draft. The same manuscript will become the reference for printed matter. For the buyer of the printing buyer, it is necessary to confirm that the contract drafting is what they want. After internal confirmation, the signature and the signed and confirmed copy are returned to the printer. The printer's salesperson will confirm whether the work can be printed based on the signed copy. In the printing process, the printing operator will refer to the same draft, and will do everything possible to control the color of the printed matter consistent with the same draft. If one of the text, color, and hue cannot be met, the print operator will stop production until the new sample is confirmed.
Method of writing
There are two main types of drafting methods: Press proof, also known as Wet proof and Off-press proof. Non-printed drafts are subdivided into analog (Analogue) and digital (Digital) drafts, and with the rapid growth of CTP, digital drafting has become a very important mode of operation.
Press printing
Printing with a printing press is arguably the most accurate method of proofing, so that the materials and equipment used can be the same as those used in production; but in terms of economic efficiency, the cost is high, not only the cost of the printing press, but also There are also costs for plates, inks and paper.
Drafting machine
Using the drafter is the most common method of proofing. The drafting machine is usually monochrome, the plate is flat and the plate is rotated; the substrate is flat and the tape is rotated. The speed of the printer is much slower than that of the press, because most printers are monochrome, so they are wet-pressed and have sufficient drying time before and after.
From many perspectives, this type of proofing does accurately simulate the characteristics of print production. The paper can be printed in the same way as the official one, and the ink can also use the same pigment, so that the hue and density obtained in printing can be accurately reproduced. The problem comes from copying the tone shifting characteristics and overprinting. The dot gain of the pad is usually smaller than that in the printing. Because it is wet-pressed, the overprinting effect is better.
Non-printing
The non-printing proofing system can produce a more consistent tone shifting feature than the drafting machine. Non-printed drafts are faster and cheaper, but when more than three to four proofs are needed, most will become uneconomical. The ability to simulate printing varies depending on the accuracy of the proofing system, the process mode, the type of job, and the substrate.
Photographing system
In the past, the European and American markets have popular photo-taking (also known as chemical proofing), including DuPont's Cromalin and KPG's Matchprint; Cromalin has become synonymous with all non-printing drafts. Fujiart has also been adopted in Hong Kong, and it has gradually been replaced by digital manuscripts in recent years because of the high cost.
Although these all show that the color gamut is well matched, there are some problems in achieving the same tone shift as printing. The European analog proofing system uses a positive image and relies on the substrate to produce sufficient optical enlargement to match the mechanically and optically increased combination achieved in printing. The amount of exposure can be adjusted by a small amount of dot gain, but it varies depending on the illumination body and the substrate. From a consistency point of view, this is good, but if the color shift in production is not close to the proofing system, then we can do very little. In general, the Cromalin and MatchPrint systems typically have too high dot gains (especially in highlights to midtones) when matching high-quality jobs, but are ideal for publication jobs.
Digital proofing system
For the simulation workflow, the color separation film represents the fixed elements in the process for making plates and proofs, so it is necessary to reproduce or mimic the printing characteristics for the proofing system.
The biggest benefit of digital drafting is that there is no need for film. Digital drafting can reinterpret the data to achieve the desired effect in production, which provides greater flexibility in simulating different printing conditions. To make this possible, the drafting system must be larger than the color gamut that is produced in production.
There are many techniques used for digital drafting, including sublimation, thermal laser transfer, electrophotography, and inkjet printing. Ink printing is currently the most versatile technology and is the most popular of all types of drafts. Its flexibility and matching printing accuracy make it the most selected drafting system.
Do you need halftone dots?
The answer to this question is mainly based on the type of job being produced. Some customers absolutely don't need it. What they need is what the printed color will look like when judging the print from a normal distance under standard viewing conditions.
Others say they need to be able to predict the mat and they don't want to display the smoother, more detailed images they get on the press to the customer. ,
Most ink-printers use error diffusion or frequency modulation techniques. It has the advantage of producing a smooth continuous tone quality. The downside is that it is not a halftone copy. More and more drafting devices are now having higher resolution, and point-to-point halftone reproduction can be obtained using the correct screening technique. It usually does not accurately represent halftones, but it is more representative of the final effect on paper. It requires predicting the mat due to the incorrect dot angle, and can express the mate caused by the halftone dot interference of the pattern image in the original. Without halftone drafting, you can't find this problem early in the workflow.
For many customers, the requirement for halftone drafting can be based on some explanations to make more improvements in print matching, rather than being limited to solving specific mating problems. For this reason, we can find that halftones are better than no halftones, and the former is more attractive, especially now that higher resolution inkjet printers provide halftone performance.