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Copyright 2001, Graphic Arts Technical Foundation Adapted from GATF SecondSight 64, a reprint of an article appearing in GATFWorld magazine.
This article presents the survey results of a research project (conducted for GATF’s 1997 symposium on mastering digital workflow) to identify and rank the most commonly occurring problems with file preparation, along with some discussion and examples. Participants monitored digital files received in their plants for a two-week. The discussion focuses on operating procedures which by necessity vary from plant to plant, and any consequent recommendations should be taken with your own workflow in mind.
The list of potential problems compiled for GATF’s digital file problem survey was based on the preflight checklist presented in "Digital Preflighting" by Ron Bertolina (GATFWorld, March/April 1996). The list was reviewed by satellite symposium moderator Howie Fenton and by members of the satellite symposium focus group, and many of the problems they suggested were incorporated. The final list of 27 potential problems was put into a survey form that was sent to the focus group participants along with a set of instructions. The problems were divided into eight categories on the survey form: disks and files, pages, fonts, linked graphics, scans, proofs, trapping, and file processing.
The survey took place over a two-week period, and the surveys returned to GATF by the participating companies represent almost 1,000 digital files. Of the 949 files examined by study participants, a majority (549, or 57.9%) contained problems that needed to be fixed by output operators before being processed. A minority of files (400, or 42.1%) contained no reported problems.
The survey forms were compiled into a spreadsheet and used to compare the kind and frequency of problems that occurred with the digital files. The top 10 of the 27 potential problems are listed below (other problems affected 3.2% or less of the files with problems):
Fonts Missing
Of the files with problems, the most common problem was missing fonts, and it occurred in 20.2% of these files. This means that the customer used a particular type style in preparing a print job, but did not include the digital files for the screen font and printer font in the files sent to the service provider. When the fonts are not included, the output device generally substitutes an available font, such as Courier, in its place, and the type looks much different than was intended. Font substitution can cause text to reflow.
The variety of fonts available today and ease of installing them (in a system folder or with a font utility) make it easy for customers to lose track of all the fonts used. Gathering the necessary elements for the service provider has been simplified by utilities such as QuarkXPress’s "Collect for Output" utility, which gathers the page layout document and all linked graphics together with a report on fonts and graphics. Due to Quark’s interpretation of font copyright restrictions, the utility doesn’t gather the fonts. This makes it easier for customers to overlook the fonts more readily than linked graphics. Adobe PageMaker 6.5 offers the opportunity to include fonts when documents are saved via the "Save for Service Provider" option.
A dialog box appears during the collection process notifying the user that it is Adobe’s policy that copying Adobe brand fonts solely to output a customer’s job does not constitute a copyright infringement. Unfortunately, at this time, word processing, illustration, spreadsheet, and presentation programs do not provide a file collection utility.
Trapping Incorrect
The second most common problem, affecting 11.5% of problem files, was incorrectly set traps. Trapping refers to the creation of overlaps between adjoining colors to compensate for possible misregister. Any unwanted movement of the press sheet during the printing process will cause white space to show where colors should abut. The same result occurs when films are not properly aligned during stripping. A properly trapped job will have overlaps of sufficient width between colors to overcome the average amount of misregister likely to be encountered.
Traps can be set manually for graphic files created with programs such as Adobe Illustrator or Macromedia FreeHand, but designers do not typically utilize these trapping functions. Page layout programs with automatic trapping functions (such as QuarkXPress) will always yield trapped pages when printed as separations, yet most designers fail to properly adjust these trap settings for the printing method to be used. As a result, files arrive at the print shop incorrectly trapped (e.g., trap area widths are too thin or too wide, black type is not set to overprint colored backgrounds, metallic inks are set to spread).
It’s important to realize that the most serious problems do not occur when items lack trapping, such as adjoining colors which do not overlap. It is the items with incorrect traps (e.g., excessive spreading into backgrounds, white type set to overprint, color type spreading on a white background, attempts to trap small point sizes) that are actually more problematic for printers. Incorrect traps are quite common, since the automatic trapping functions of page layout software cannot be turned "off" when separations are printed. This forces printers to spend time examining individual areas which are likely to be incorrectly trapped.
Traps can be corrected within the original art files and page layout programs, or they can be added later, using PostScript trapping software or by trapping on the RIP itself.
Many printers invest the time to correct trapping in customer documents so that the corrected files can be archived for later use or returned to the customer. This way, the problem is less likely to occur on that same illustration or document in the future.
Other printers, however, take a different approach to this dilemma. They print the document in composite color mode, thereby disabling the automatic trapping within the page layout document. This allows the printer to create new traps to suit the printing process.
When the composite PostScript data is being printed, the information can either flow directly through the network to the output device, or it can be saved to a hard drive as a PostScript file. Saving it to a hard drive is necessary if trapping is to be done using a PostScript trapping software program (e.g., Luminous TrapWise, Ultimate Trapese, or DK&A Trapper) that uses Encapsulated PostScript files. The alternative is to create traps at the RIP itself. RIPs from Scitex, Screen, Rampage, Contex, Harlequin, and Linotype-Hell (now Heidelberg Prepress) offer trapping capabilities. Adobe has announced that the trapping features of Luminous TrapWise will be made available as part of the PostScript 3 CPSI (Configurable PostScript Interpreter) software, the core of many prepress RIPs. It seems likely that more vendors will offer trapping on the RIP as the use of PostScript 3 gains wider acceptance.
Regardless of the method used, what’s most important is that printers be able to recognize the difference between files that are properly trapped and those that are not. This is one reason many printers hesitate to give up film in pursuit of computer-to-plate workflows—it’s possible for a stripper to examine the films and assess the quality of the trapping. Strippers and other prepress workers with experience in traditional graphic arts processes make excellent candidates for retraining for digital prepress operations because they bring their practiced knowledge of the conventional prepress craft with them.
Colors Incorrectly Specified
The third most common problem, affecting 10.9% of files with problems, was colors specified as spot rather than process. In page layout, illustration, and scanning software, users can name special colors and use them to fill shapes, create borders, or color type. Software typically gives users the option to separate the color into one or more of the four-color process (CMYK) plates, or to output it as a separate plate for printing with spot-color ink. If a user defines a special color without specifying it as a process separation, the color will output as an additional plate. The extra color would then have to be printed on an additional press unit or omitted from the job.
QuarkXPress’s default color palette contains CMYK plus the spot colors red, green, and blue. Eliminating these spot colors from the color palette reduces the likelihood that spot colors will be accidentally used in a document.
Images in the Wrong Mode
Advances in desktop scanners have enabled many designers to do their own scans for print. Desktop scanners produce image files that consist of red, green, and blue information, known as RGB mode. When output to imagesetters, these files must be converted to a format suitable for process-color printing, which is CMYK mode. By default, many RIPs will print unidentifiable colors (such as red, green, or blue) on the black plate. If an RGB image is output to film, the imagesetter may set a halftone on only the black separation, the CMY films will be blank (unless the imagesetter is equipped with PostScript Level 2 and a color rendering dictionary). The fourth most common problem, affecting 7.8% of digital files with problems, was images that were in the wrong mode.
Increased use of desktop scanners plus their use by operators with a wider variety of skill levels than in previous years most likely accounts for the predominance of RGB files in documents. (Desktop flatbed and slide scanners generally output RGB files; desktop drum and high-end drum scanners can be set up to output CMYK files.) RGB files will not separate unless the RIP is PostScript Level 2, contains a color rendering dictionary (CRD) for RGB-to-CMYK conversion, and has been set to convert modes automatically. CRDs have become the preferred paradigm in on-demand printing, especially with color copiers.
For print, CRDs simplify workflow by allowing RGB files to be separated at the RIP, and allow the RIP manufacturer to optimize color conversion for the reproduction characteristics of the output device. Use of CRDs in imagesetters and platesetters would enable service providers to customize CRDs for each combination of paper, ink, and press for which separations will be output.
Many pundits point out the potential of RGB files to simplify image capture, archiving, and customized output for specific print conditions, which is useful in multipurposing images for print, multimedia, and web publishing.
Page Settings Not Correct for Output Device
Page layout software, under "Page Setup" and other settings, provides several options for controlling output, including the page size, orientation, media size, margins, polarity (negative or positive), direction (right-reading or wrong-reading), and the like. The fifth most common problem, affecting 7.4% of problem files, was that these page settings were not set properly for the output device.
One way to help clients make page settings correctly is to supply them with templates that have the correct page settings. One study participant, Ric Williams, head of electronic prepress at Stevenson Photo Color, Cincinnati, Ohio, said, "We cater to book-cover designers and have a lot of repeat customers. From the beginning, we provide them with electronic templates and show them how to set up jobs for us to output." Apparently the templates and training pay off, as Stevenson had a remarkably low incidence of problems in the study.
Graphics Not Linked
The most common method of outputting graphics, such as illustrations and photos, is to import them into a page layout program that enables them to be combined with text on a page. Including the image files in the page layout document would, however, result in excessively large page layout files. Therefore, graphics are generally referenced as independent resources within the PostScript file, linked via PostScript commands to the pages on which they appear. As the survey showed, several problems can occur with graphics files. The sixth most common problem, affecting 5.3% of problem files, was that the graphics had lost their links to the page layout. This means that operators needed to reestablish the links prior to output.
In page layout documents, linked graphics may become unlinked if they are saved in a different folder than the one in which the document is saved. Also, modifying a file (as evidenced by a different file modification date and time) will cause the link to be shown as "modified." DK&A’s Picture Reunion, an XTension that searches for and relinks graphics that have become unlinked, may be helpful in finding and relinking QuarkXPress graphics.
Bleeds Inadequate
If a photo or other graphic is to extend to the edge of a page, it must be set up to bleed, or overlap the trim margins by a specified amount. The seventh most common problem was that bleeds were not set up properly or were inadequate. This affected 5.2% of problem files.
Many users are aware that for a graphic to extend to the edge of a page, it is necessary to create a specified bleed (typically 1/16 or 1/8 in.). A problem can occur when pages are saved in EPS format. The PostScript bounding box definition, which is based on the page size specified in the program, will cause the bleed to be cut off in the EPS. This can be a problem especially with nonstandard electronic publishing programs. This is a client education situation that requires a communication solution.
Laser Not Supplied
The customer who sends electronic pages to a service provider for output to film and subsequent printing may not have an imagesetter for recording film but often has a black-and-white laser printer. In this case, printers will ask the customer to send a marked-up B&W laser print of the documents, with colors set to produce separate CMYK separations. Many service providers also prefer to have such B&W laser proofs marked up with the names of colors and files. The eighth most common problem was customer failure to provide a laser proof along with electronic files sent for output. This problem occurred with 4.6% of problem files examined.
Customers may think that B&W laser proofs are not important, especially for color jobs. Of what value then is a low-resolution B&W laser print? For printers, it’s like watching the customer’s monitor as the document is prepared. A printer who receives only a disk has no idea what’s on it. A B&W laser proof verifies the document to be output. The printer can compare a laser proof output at 100% to film or a proof, flip-checking to verify the correct positioning of elements and to rule out text reflow problems.
Files submitted via the Internet or over a phone line can be accompanied by a faxed laser copy. It’s better to output the copy on a laser printer and then fax it using a fax machine, rather than faxing directly from a computer. If faxing from a computer, the customer can’t see what the lasers look like.
Graphics Missing
A problem similar to but more serious than unlinked graphics occurs when graphics files are not included with the materials sent to the service provider. The missing graphics remain visible in page layout documents, but omitting the files (which are not part of the page layout) causes graphics to be output in low resolution. Low-resolution output will be pixelized or fuzzy looking. Missing graphics files occurred with 4.5% of files with problems and proved to be the ninth most prevalent problem.
This problem is similar to the missing fonts problem. QuarkXPress’s "Collect for Output" and PageMaker’s "Save for Service Provider" utilities will gather all necessary linked graphics. Customers should be advised or trained to use them.
Resolution Too Low or High
Photographs need to be scanned at a resolution specified for the screen ruling and output device. Image files that are too large consume excessive storage space and take too long to transmit and output. With files that are too small, the images will be fuzzy and pixelized. Improper resolution occurred with 2.7% of problem files and was the tenth commonest problem.
Resolution is especially important with digital images because the space required for a file increases with the square of the resolution—as resolution doubles, file size quadruples. A 4x5-in. CMYK image, for example, that takes about 3 MB at 200 dpi would be more than 12 MB at 400 dpi.
Numerous articles have been written about the resolution required for digital image files. Some authorities claim that a resolution of two times the screen ruling is optimal, based on the Nyquist theorem of analog-to-digital sampling, while others write that one and a half times may be acceptable. We have worked on jobs where customers were not satisfied with resolutions of 2x screen ruling. In one instance, the block letters in the company’s name reproduced with jagged edges. The customer was satisfied only by the results of scanning at a resolution 3x the screen ruling. Resolution depends on the nature of the original and the customer’s expectations for sharpness. Some scanning programs automatically select scanning resolution for the operator, e.g., Linotype-Hell’s Linocolor, Flamingo Bay’s Scan Prep Pro.
Another consideration for resolution is that the scanner operator may not know the designer’s intended enlargement or reduction. Higher resolution gives a designer more leeway to enlarge images.
Conclusions
Man and machine. The digital file problem survey addressed several problems that have plagued electronic production since the advent of PostScript imaging. These include PostScript errors that prevent files from completely processing, long processing times due to excessive file complexity, and banding in blends. None of these "classic" problems made the top 10 list, and none affected more than 1.4% of problem files.
The three most common problems were missing fonts, faulty traps, and improperly specified colors. These observations may indicate that technological advancements have helped eliminate some problems that were more common with earlier PostScript equipment, leaving operations requiring operator skill or attention, such as creating traps and including fonts, to remain as key hindrances in file preparation.
Preflighting and file repair. The results of the study highlight the importance of preflighting and file repair in the acceptance of customer files. Preflighting and file repair are different processes. Preflighting discovers and identifies problems with customer files. File repair is the process of correcting these problems after authorization has been given by the customer.
The first step in implementing preflighting is to modify your quotation sheets to make sure they carry a crucial phrase: "This quotation is based on the assumption that all supplied files are ready for output. Any corrections or changes necessary to ensure successful output will be charged as additional work at the appropriate hourly rate, upon approval of the customer."
File checking utilities like Extensis’s PreFlight Pro or Markzware’s Flight Check can help automate the preflighting process.
B&W vs. color. Although our survey results are not comprehensive enough to permit commenting on how file preparation problems affect different printing industry segments, the results do show that participants doing black-and-white or on-demand printing had fewer file problems than those doing color. Since the preparation of color files involves more options, settings, and skill, it is not surprising that jobs confined to one or two colors had fewer problems.
Acknowledgments
The authors wish to thank Mike Marcian, president of Corporate Press in Landover, Maryland, for suggesting this survey during a satellite symposium focus group conference call. We also thank the focus group members who tracked their customer file problems and shared their results.
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