Editing Imposition (section)

== Digital techniques ==
Manual imposition processes tend to cause bottlenecks of the whole printing production. The first digital imposition software, Impostrip, was released in 1989.<ref>{{cite web |url=http://americanprinter.com/mag/imposition_cim_you_0205/ |title=Imposition software, CIM & you, Part 1, AMERICAN PRINTER, February 2005 |accessdate=2012-01-17 |url-status=dead |archiveurl=https://web.archive.org/web/20101019124205/http://americanprinter.com/mag/imposition_cim_you_0205/ |archivedate=2010-10-19 }}</ref>  The advent of digital imposition has not only helped a lot in making sure layout and sheet arrangement are correct with higher register precision, but it significantly reduces the usual imposition errors (e.g., slight movements of register due to parallax). An entire book may be ''imposed'' and many complex functions applied in an instant.  Binding options may be changed on the fly and impositions produced to multiple output devices at once, often with no user intervention. In turn, digital techniques help to reduce material costs, time and resolves production bottlenecks. There are several different approaches to digital imposition.<ref name="Handbook of print media" >{{cite book
  |title=Handbook of print media: technologies and production methods
  |last=Kipphan  |first=Helmut
  |date=31 July 2001 |editor=Helmut Kipphan
  |publisher=Springer 
  |isbn=3-540-67326-1
}}</ref>

* Imposition in the design application. Software packages that can be used to design single pages can often be used to design entire printed sheets, sometimes by a process as simple as copy/paste onto a larger sheet. This is still in use, especially for low volumes of work, but a popular alternative is an imposition function built in, or added in, to the design tool. This typically takes a document prepared as single pages and creates a new document with full-sheet layouts. This larger layout is then printed to film or a plate.
* Imposition through shell scripts and operating system features.  This approach works particularly well on desktop Unix in a small office/home office environment (where a printer may only be capable of handling A3 and smaller).  A trivial script might be written to re-arrange pages in a [[PostScript]] or [[Portable document format|PDF]] file to make them suitable for final imposition through the built-in ''Page Setup''.  
** For the imposition of an A4-sized hardcover book on A3 paper, for example, one could first write a shell script to re-arrange the document in the following sequence: 1, 32, 31, 2, 3, 30, 29, 4... 33, 64, 63, 34, 35, 62, 61, 36...  Then, using ''Page Setup'' or ''Print'' (under the File menu) one could print two pages per sheet, double-sided.  The result could then be folded in half along the width, arranged as 8-sheet signatures, sewn, and bound.
* Post-design imposition. A post-design application might take a [[PostScript]] or [[Portable document format|PDF]] file in single pages and produce a new PostScript or PDF file with imposed sheet layouts for printing. A variation of this is to take a large number of single-page source files as input. This is especially suitable for a magazine or newspaper, where pages may be worked on by different groups simultaneously.
* Print driver imposition. Some printer drivers enable the source application's single-page printed output to be sent to the printer as full sheets. This is not often found in professional production, but is popular for such things as booklet printing on office laser printers. A variation of this offers the ability to print layouts as an option in the application.
* Output device imposition. This is sometimes called "in-[[Raster image processor|RIP]] imposition". This allows regular pages to be printed by any suitable means, and the output device handles imposition. While this offers the advantage of enabling specific tuning of the imposition for an output device, the cost is that there is no preview until the output is produced. This may mean a costly printing plate that takes some time to produce, or even (with a digital press) errors in finished copies: expensive mistakes are possible.

Where an imposition layout is viewed on screen, it may be referred to as a '''printer's spread'''. This is used to contrast with '''reader's spread''', which shows a finished printed piece on screen as it will appear to the reader, rather than the printer; specifically, in a reader's spread for a typical book, pairs of facing pages are shown side-by-side (that is, pages 2 and 3 together).