6.1 Introduction
Roberto Medeiros
Learning Objectives
- Describe digital printing methods and their differences
- List the various inks used in inkjet printing and their characteristics
- Identify the key components of electrophotography
- Explain the seven steps of the electrophotographic process
- Describe the differences between toner types and how they affect imaging
- Evaluate the suitability of a paper for a project based on its characteristics
- Convert between paper basis weights and grammage
- Describe the key differences between page description languages
- Acknowledge the historical significance of Postscript in desktop publishing
- Explain the differences between PDF/X versions
- Describe the function of a RIP in a DFE
- Explain why calibration is critical in electrophotography
- Describe the key component in variable data printing
- Identify key benefits of open standard VDP formats
Digital printing can be defined as the reproduction of an image or document onto a substrate, directly from an electronic file, without the use of a fixed image plate. Traditional printing transfers an image permanently onto a fixed image plate, whereas digital printing transfers the image temporarily onto a photoconductive cylinder, called a drum, or directly onto the substrate itself. Printing in this manner provides some unique capabilities that sets it apart from traditional print methods. There is virtually no set-up or make ready, finishing tasks can be accomplished inline, and each sheet can have unique content, which makes this printing method ideal for publication printing, short print runs, or highly dynamic content.
The two most common digital printing methods in use today are electrophotographic (toner based) and inkjet (ink based). Both technologies are used in a wide range of printing devices from small desktop printers to large high-volume, high-speed digital presses. The term digital press is often used to describe commercial digital printers. In the past, speed was the determining factor of this designation. Today, we have specific criteria published by Idealliance, a not-for-profit member organization that develops standards and best practices for the digital media supply chain (Idealliance, n.d.). Apart from speed, colour accuracy to meet a specification and consistency over long print runs are key parts of Idealliance’s certification process. You can find out more at this webpage:
http://www.idealliance.org/certifications/digital-press
For the purposes of this text, we will focus on digital printers and presses used in commercial printing rather than on consumer or office printers.