PDF / X

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Under PDF / X several are standards of ISO summarized. These describe the properties of print templates as PDF files in order to enable the data from prepress to be transferred to the actual printing process in accordance with the template . This is how PDF / X-1a describes the true-to-color reproduction in the CMYK color model . While PDF / X-3 insufficiently expands this to the RGB color space , with PDF / X-4 a standard was created that meets the requirement for an exchange that is as media-neutral as possible.

properties

PDF / X standardizes a subset of the Portable Document Format (PDF) that meets the requirements of printing technology for the respective print template . Both PDF elements that can impair the predictability of the print result and those that cannot be meaningfully printed (e.g. video and audio ) are prohibited . In addition, precise information is required that is necessary for the printing company , e.g. B. Trim , color information and fonts used . The aim of the standards is to avoid or at least minimize various problems when exchanging files from DTP and graphics programs with the printer.

Compliance with the requirements can be checked during the entire print preparation using the so-called preflight . This means that the print result corresponds to the desired layout much more reliably . The print media standard prefers PDF / X as the data format for proofs ; it is based on the Process Standard Offset (PSO) anchored in ISO 12647 .

The quality requirements that depend on the specific printing process are not defined. For example, the requirements in newspaper printing differ from both commercial printing and high-quality picture printing . Most layout and some word processing programs offer direct export of PDF / X files. Alternatively, you can first print in PostScript , then the data can be converted to PDF or PDF / X using conversion programs such as Adobe Acrobat or Ghostscript .

Various aspects of PDF / X are not taken into account when creating the templates:

  • the resolution of full tone , halftone or line images suitable for the process ;
  • in the case of lossy compressed JPEG images, clearly visible artifacts can appear;
  • Hairlines that are too thin can "break away" when printed, they can then only be seen with the measuring magnifier or not at all;
  • a missing font style in the PDF file is replaced by another, often Courier ;
  • black font or lines are defined in such a way that they are built up in three or even four colors when printing, cf. CMYK color model .

Some of these problems are already pointed out by some programs during the PDF creation with so-called check profiles in a "list of possible problems".

PDF / X defines regulations primarily for the following problem areas:

Colour reproduction

Color specifications must meet certain requirements. The support of Lab- and ICC-based color information in PDF / X-3 enables a certain "media neutrality", i. H. The same document can theoretically be output under different printing conditions with the best possible color representation. In the past, PDF / X-1 was more strongly adapted in America, while PDF / X-3 was predominantly propagated in Europe. Today, modern workflows worldwide recommend PDF / X-4 for unflattened print data and PDF / X-1a for flattened transparencies.

  • Clearly interpretable color information

Other information

There are also other properties which include the following:

  • Completeness of data and information for printing
  • Exclusion of unpredictable printing results
  • no alternative images that are set to printing
  • Page size of the trimmed page ( TrimBox ) and required bleed allowances ( BleedBox )
  • Bleed and trim size must be defined (BleedBox, TrimBox)
  • no use of LZW compression
  • Notes and comments are only allowed outside the printed area
  • no JavaScript , no form functions
  • all images must be integrated (no OPI functions, there is PDF / X-2)
  • no encryption ("security"), as this is an obstacle for files that are to be printed by others
  • Overcrowding : It must be indicated whether the PDF / X file has already been overfilled or whether the recipient still needs to overfill
  • Date of creation or last change date as well as document title and information on the generation program must be available
  • no page description operators that are not defined in PD format
  • Embedded PostScript prohibited
  • Exclusion of gradation curves ("transfer functions").
  • no transparencies

In 2003 PDF / X-3 was published as ISO 15930-6 in a revised version - referred to as PDF / X-3: 2003 - with essentially only minor formal changes being made. With the revised version, however, all PDF / X-1a files are now always valid PDF / X-3 files.

Overview of the standards

PDF / X now exists in a large number of variants, which are identified by an appended number and a year. There is a corresponding version of ISO standard 15930 for each variant.

The ISO 15929 standard describes the guidelines and principles according to which the various parts of ISO 15930 are developed:

  • ISO 15930-1: PDF / X-1a: 2001 limited to CMYK and special colors on the basis of PDF 1.3 color specifications .
  • ISO 15930-2: the originally planned version of PDF / X-2 never appeared (see standard part -5).
  • ISO 15930-4: PDF / X-1a: 2003 updates PDF / X-1a from 2001 on the basis of PDF 1.4. Above all, CMYK and spot colors are supported in every combination.
  • On the basis of PDF 1.4, ISO 15930-5: PDF / X-2: 2003 also supports externally referenced page elements in addition to embedded page content and thus enables OPI-like workflows.
  • ISO 15930-6: PDF / X-3: 2003 based on PDF 1.4 updated version of PDF / X-3: 2002.
  • ISO 15930-7: PDF / X-4 and PDF / X-4p are based on PDF 1.6. If all required elements are contained in the file, one speaks of PDF / X-4. If reference is made to an external color profile, the variant PDF / X-4p is called. Color management, CMYK, RGB, grayscale and spot colors are supported. PDF transparencies and other optional content such as JPEG2000 , 16-bit image data and OpenType fonts are also permitted.
  • ISO 15930-8: PDF / X-5 is based on PDF 1.6 and supports both embedded and externally referenced elements. In addition to the possibilities of PDF / X-4, multi-channel ICC profiles can also be used.

See also

Web links

Individual evidence

  1. ↑ ISO 15929: 2002. March 17, 2008, accessed October 7, 2010 .
  2. ↑ ISO 15930-1: 2001. August 30, 2006, accessed October 7, 2010 .
  3. ↑ ISO 15930-3: 2002. September 7, 2007, accessed October 7, 2010 .
  4. ↑ ISO 15930-4: 2003. October 7, 2009, accessed October 7, 2010 .
  5. ↑ ISO 15930-5: 2003. October 7, 2009, accessed October 7, 2010 .
  6. ↑ ISO 15930-6: 2003. October 7, 2009, accessed October 7, 2010 .
  7. ↑ ISO 15930-7: 2010. July 16, 2010, accessed October 7, 2010 .
  8. ↑ ISO 15930-8: 2010. July 16, 2010, accessed October 7, 2010 .