Parsing is one of the fundamental steps in prepress printing process. This consists of setting the print product pages on the printer sheet, to get faster printing, simplifying binding and reducing paper waste.
Correct loading minimizes printing time by maximizing the number of pages per impression, reducing the cost of time press and materials. To achieve this, the printed sheets should be filled as fully as possible.
Video Imposition
Task
The page layout on the printer sheet is affected by five different parameters:
- Product format: The completed page size determines how many pages can be printed on one sheet.
- Number of pages of printed product: The compositor must determine how many sheets will print to make the finished book.
- Stitching/binding method: Compositor must understand how sheets are placed to form signatures that make up the finished book.
- The direction of paper fibers: Many papers have "grains," which reflect the alignment of paper fibers. These fibers must run long along the creases, affecting the alignment, then the position, the pages on the printed sheets.
- Complete and bind
To understand how pages are related to each other, dummy can be used. This is made by folding several sheets of paper according to the way the press will print and fold the product. A small copy is then created, and this can help determine the number of products.
In the example above, a 16-page book is prepared for printing. There are eight pages on the front of the sheet, and eight pages on the back. After printing, the paper folds into a vertical half (page two falls into page three). Then folded again horizontally (page four meets page five). A third fold completes this process (page nine meets page eight). The example below shows the final result before binding and trimming.
Maps Imposition
Non-digital techniques
The imposition has been a necessity since the early days of printing. When a page is set using a moving type, the page is assembled in a metal frame called chase , and locks into place using wedges called quoins .
By the end of the 20th century, most of the font arrangements were in photographic films. The sheets are manually combined on a light table, in a process called stripping . Skilled workers will spend hours stripping pieces of the movie together in the correct sequence and orientation. The stripping term is also used for other changes to the prepared page, such as spelling corrections, or the stop press story in the newspaper. Digital techniques make stripping less necessary, but what has forced an increasing amount to leave it completely is the introduction of "pelatter", which puts the page directly into the printing plates; these plates can not be adjusted with a sharp knife. In addition, very high accuracy will be required for stripping the color work, as each ink color is in a separate part of the film.
Digital techniques
The process of manual imposition tends to cause congestion throughout the printing production. The first digital software, Impostrip, was released in 1989. The emergence of digital imposition not only helps a lot in ensuring the correct layout and adjustment of sheets with higher precision registers, but significantly reduces the usual loading errors (eg, slight register movement due to parallax). The entire book may be imposed and many complex functions are applied in an instant. Binding options can be changed quickly and the resulting loading to multiple output devices at once, often without user intervention. In turn, digital techniques help reduce material costs, time and complete production bottlenecks. There are different approaches to digital imposition.
- Imposition in the design application. Software packages that can be used for single page design can often be used to design the entire printed sheet, sometimes with a simple process such as copy/paste into larger sheets. It's still used, especially for low-volume work, but a popular alternative is the coercion function built in, or added into, to the design tool. This usually requires a document to be prepared as a single page and create a new document with a full sheet layout. This larger layout is then printed onto a movie or plate.
- Post-design coercion. Post-design apps may take PostScript or PDF files on one page and generate new PostScript or PDF files by applying a sheet layout for printing. This variation is to take a large number of single-page source files as input. This is perfect for magazines or newspapers, where pages can be done by different groups simultaneously.
- The imposition of the print driver. Some printer drivers allow one-page print output from the source application to be sent to the printer as a full sheet. These are not often found in professional production, but are popular for things like book printing on office laser printers. This variation offers the ability to print the layout as an in-app option.
- Loading of output device. This is sometimes called "imposition of in-RIP". This allows regular pages to be printed in any suitable way, and output devices handle the imposition. While this offers the advantage of enabling a specific tuning of the imposition for an output device, the cost is that there is no preview until the output is generated. This may mean expensive printing plates that take a long time to produce, or even (with a digital press error) in the finished copy: costly mistakes may occur.
Where the imprint layout is viewed on the screen, it can be called a printer's spread . This is used to contrast with reader deployments , which shows the on-screen printouts that will appear to the reader, not the printer; in particular, in the reader's spread for regular books, the facing page pairs are displayed side by side (ie, pages 2 and 3 together).
Proof of loading
Proof of loading is the last test performed before the start of printing.
This test is performed to verify, through the formation of a prototype, that the imposition is successful. The general check is that the pages are in the right place and the cross flow works. It can not be used as proof of proof for an image or color or layout as it is printed on a large low resolution inkjet printer.
Since inkjet printers can only print on one side of the paper, full proof (front and back) are printed on two separate sheets. They first cut along a line of falling cross, checking to see if they are in the correct position. The two sheets are then attached together to form a single sheet printed on both sides, and then the sheet is folded to form a signature prototype.
This proof is still called blue copy, digital blue copy to prototype, or blues plotter.
References
External links
- History of Imposition
Source of the article : Wikipedia
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