Pre-flighting is a term used in the printing industry to describe the process of confirming that the digital files required for the printing process are all present, valid, correctly formatted, and of the desired type. The term originates from the pre-flight checklists used by pilots. The term was first used in a presentation at the Color Connections conference in 1990 by consultant Chuck Weger.
In a common digital prepress workflow, a collection of computer files provided by clients will be translated from an application-specific format such as Adobe InDesign or QuarkXPress to a format that the raster image processor (RIP) can interpret. But before this rasterization occurs, workers in the prepress department confirm the incoming materials to make sure they are ready to be sent to the RIP. This is an important step because it prevents production delays caused by missing materials or improperly prepared materials. Once the incoming materials have passed the pre-flight check, they are ready to be put into production and sent to the RIP.
These intermediate formats are commonly called page description languages (two common PDLs are Adobe PostScript and Hewlett-Packard PCL). The RIP prepares the final raster image that will be printed directly (as in desktop inkjet or laser printing), set to photographic film or paper (using an imagesetter), or transferred direct-to-plate.
Depending on the hardware and software components and configurations, RIPs have unique problems rasterizing the image data contained in a PDL file. If there is a failure in rasterizing the image, it can be costly, as imagesetters, direct-to-plate systems, and high-end inkjet printers can consume expensive supplies, can require extensive amounts of time to process complex image data, and require skilled labor to operate.
The process of pre-flighting a print job helps reduce the likelihood of rasterization problems that cause production delays. Page layout software applications, (which allow users to combine images, graphics, and text from a variety of formats,) automate portions of the pre-flight process. Typically, client provided materials are verified by a pre-flight operator for completeness and to confirm the incoming materials meet the production requirements. The pre-flight process checks for:
Other, more advanced pre-flight steps might also include:
The specifics of what checks are made is governed by the features of the pre-flight application, the formats of the client provided files, and the targeted output device as well as the printing specifications.
A purpose-built software application is not required to pre-flight a file, although several commercial applications are available. Small shops may use an inexpensive laser printer to test whether or not their file will print. The conversion to Portable Document Format (PDF) can reveal problems, and can in some circumstances be considered a pre-flight process.
Early pre-flight methods were largely manual, and typically relied on checklists that highly-skilled prepress operators would use to verify the production readiness of each incoming job. As desktop publishing and graphics applications, PDLs, RIPs, and output devices evolved, the process became more complex. Software plug-ins and stand-alone applications that supported the major desktop publishing applications were then developed to meet that need, along with proprietary tools made by hardware manufacturers and commercial printers and service bureaus. The developers of the major applications then began to incorporate functionality in their applications, leveraging their knowledge of their own file formats.
As early as 1996, Ron Bertolina brought preflighting into the mainstream of the printing industry with his 1996 GATF article on "Preflighting Digital Files," which can be found adapted from 2001 GATF SecondSight 75 at http://www.bestprintingonline.com/resources/art1253.htm