ePUB Illustrated — November 2001

2. Page Integrity - Reflow

What ePUB terms page integrity is also commonly referred to as page flow, or page layout. A common problem with OG applications is "page reflow." Or, "Why is my 32 page document now 35 pages?" Page integrity is primarily a problem with Word and WordPerfect, but may also occur in larger PowerPoint files.

Why does reflow happen? Mainly it happens because OG applications are not designed for structured print output. Word and WordPerfect are text editors and they do a great job of handling text, but they are not layout applications and therefore they do not handle page layout particularly well. The technical answer is that text editors usually flow text and layout pages based on printer metrics. In other words, your OG document flows based on the settings (metrics) contained in the printer that is connected to your computer workstation. Since each printer has different capabilities, each printer's metrics are different. Therefore, document layouts based on printer metrics will appear different when you change printers. Test it yourself by changing printers in a Word document (Hint: Longer documents are better. You should notice slight to major differences in line endings and page breaks).

A related problem is that most office printers use a control language called PCL while the printing industry is almost exclusively PostScript. PCL printers have different metrics than PostScript printers. Even with standalone printers that support both languages and can switch between PCL and PostScript, the metrics differ and documents may change. Concurrently, commercial print vendors use high-end PostScript printers which do not exist in the typical office environment. Therefore, it is common for OG files to change appearances, sometimes drastically, when submitted for press output.

Fonts also impact Page integrity when customers fail to supply them to the print vendor. There is a common misconception that fonts are not required if they are "common" or "system" fonts (see the Myths article for more). However, the only way to guarantee that a job processes correctly is to supply any and all necessary fonts.

3. Lack of Prepress Features

Due to production requirements, files submitted for commercial offset printing must have special features including, but not limited to: Trim Marks, Bleeds, and Color Separation. Software that does not support these special features require additional handling and processing. In turn, costs rise and schedules are jeopardized.

Definition of Terms:

Bleeds:	Areas of image, text, art, or other data that extends beyond (1/8" minimum) the edge of the printed page. Vendors need bleed when trimming items in the finishing process.
Trim Marks:	Automatically drawn lines indicating where the paper should be cut to produce the correct page size. Trim marks are necessary for offset printing when the original paper that goes through the printing press is larger than the final page size (see bleeds), and trimming is required.
Color Separation:	The act of separating a color graphic or photo into single-color layers. To print colors with an offset press, all colors must first be deconstructed into separate layers. Each single-color layer is then printed separately or combined to form the desired product.

OG software does not support these common prepress functions. Each OG submission that is processed by the commercial print community incurs extra charges that are not applicable to professional graphics applications such as Quark XPress or Adobe InDesign. In addition, issues such as trapping are also ignored by OG applications.

4. Graphics Handling

In the print publishing industry, two formats (.TIFF and .EPS) are primarily used for graphical elements. However, most OG applications do not handle .TIFF and .EPS graphics well or sometimes at all. Those OG applications that support them typically convert .TIFF and .EPS to internal formats (embedding files) that are incompatible with most PostScript production processes. This internal embedding and conversion may effect RIP performance, consequently causing problems at output. Other potential problems with OG graphics are color shift and loss of information to name just two. For a technical paper from Adobe Systems Incorporated on the downside of Office Graphics applications, please click HERE for the PDF file.

Most PG applications provide the ability to link to high-res .TIFF and .EPS files; however with OG applications, graphics are always stored in the document. This inability to "link in" files can cause problems with trapping, color separation, and other prepress features. While it is possible to extract the embedded graphic files, the extraction is time consuming and expensive. Additionally, many vendors do not have the technical expertise to efficiently handle embedded graphics in OG files. Another drawback of these applications is the inability to verify status of embedded documents. Since certain file characteristics can cause RIP problems, prepress workers are trained to look for potential problems that will affect their workflow. Most PG applications provide the ability to "get info" on linked or embedded graphics (e.g., color mode, resolution, link status). This information provides invaluable insight, but is unavailable in OG applications.