Output stacker for the IBM InfoColor 70
 
 
 
 
 
 

The main reasons why digital printing differs from traditional printing are listed below. Click on the title bars to learn more. 

Also included in this section are case studies illustrating how digital printing has been used to radically change the value and turnaround of printed goods. 

In order to realise the benefits that digital printing can offer, we should first look at the way a traditional print job is prepared. 

Preparing a job for a traditional litho press is fairly labour intensive. Once the design has been approved. PC or Macintosh disks can be sent to the printers. 

Once there, any pictures are scanned at high resolution to generate digital images with sufficient quality of detail for printing. These are then added to the existing files. 

The job is sent to a device known as an imagesetter. This, in effect, creates very high resolution film masters for each page. If four-colour printing is used, there are four separate masters for each of the four process colours (cyan, yellow, magenta and black). 

Although it is relatively easy to impose the pages in the order required to create the pages of the job, in reality only about 40% of print companies actually do this. They rely instead on manual film planning or stripping. This process involves skilled craftsmen cutting and sticking the individual pages together to create the imposition. 

Once each set of films has been created for each printing plate, they are placed on top of the photo-sensitive plate and exposed to a powerful light source. The plates are then developed and punched and bent to fit onto the press. 

When the plates are on the press, the pressman inks up each plate and starts to adjust the press to register each colour at the correct ink density. It can take quite a lot of time (and hundreds of sheets of paper) to get an awkward job printing correctly. 

The digital printing method requires the disks from the client and the high resolution scans as before, however once on the screen the job is sent to the digital press and printing starts after only four or five pages of waste. There is no downtime between jobs if the individual print jobs are queued up sequentially behind each other on the computer. Imposition is handled by software built-in to the press itself.