Preflighting is the process
of checking digital files prior to film output. It can be done manually
or with the assistance of a software package. The purpose of preflighing
is to identify problems that may occur in the print process prior to outputting
film, therefore reducing or avoiding the risk of wasting money by catching
errors when they are still easy to correct; prior to film output.
TrueType Fonts tend to be problematic due to the fact that there are no screen and printer fonts as in Type 1 fonts. Instead, there is only one scaleable font which, while OK on the monitor and when output by a laser printer, tend to be problematic when outputting through an imagesetter.
Improper Font styling is a common problem. Type 1 fonts are created with a separate font for each style, that is, plain, bold face,italic, etc. In page layout programs such as Quark and Pagemaker, styling can be applied to any text much like a word processing program. While this may look OK on your screen and even print nicely on your laser printer when the file gets to the image setter it will undoubtedly cause problems.
Imagesetters need the actual font, ie, Times Roman Italic, Times Roman Bold, etc. so be sure to include all typefaces that have been utilized in your document.
Unused Fonts are a problem when they are called for in a style sheet or template but are not actually used in the final page layout. If a font is identified in the style sheet, the imagesetter is going to look for that font regardless if it has been used or not.
Before we can have a meaningful discussion
about Image Problems, we will need to define a few technical terms, so
A typical problem occurs when only a low resolution file is provided. When output, it will look jagged, blurred, lacking in definition, or as we in the industry technically call it, "really ugly". Therefore, always check to make sure the high resolution files, not the low, are included. If you use OPI, then we will have the high resolution files on hand here, and will "swap out" automatically to high resolution.
Another popular glitch is not linking image files properly if they get renamed. Example: Your designer is rushing to meet a deadline. He/she makes a last minute change to a graphic filed called "Logo-1" resaves it as "Logo-2" and then wisely removes the old logo file from the disk. When we attempt to output the file, the imagesetter stops and gives us a look not unlike the RCA dog with his head tilted to one side. Why? Because the page layout still calls for "Logo-1" which no longer exists. Things could be worse... what would have happened if the designer had NOT removed the old logo? Your proofs would have arrived with the old image in place and if the error wasn't caught, your finished piece would have gone to press with it.
The failure to specify the proper amount of colors for a given job happens quite often. If you have ever gone through the experience of noticing that type or other elements are missing from your proofs, quite often the reason is the improper specification of color. As an example, if a job is specified to run as two colors only, with PMS 200 and PMS 135, but there are elements in the file that are specified as PMS 201, these elements will not appear on your films. The reason is that your printer has instructed its computer to output only 200 and 135. If 201 has not been specified, it will not appear in the final output.
Why colors don't print the way you last saw them on your monitor.
ADDITIVE PRIMARY COLORS The red, green,
and blue (RGB) components of light are called additive primaries. The
display of all monitors is RGB. The additive colors are transmitted from
light sources through the monitor.
It's not a woman's name, its when
your colors darken on press.
Trapping. The overlapping of one color over another.
A computer gives the user the ability to perfectly align colors. Since the printing process is an imperfect one, the same accuracy cannot be expected when the job is running on press. Therefore, when two or more colors touch eachother, a process called "trapping" is utilized. Trapping entails having different colors overprint eachother slightly, in order to compensate for any shifting of the paper as it goes through the press. The "trap" can be applied by the designer but it is usually advisable to allow your printer to apply traps because the amount of trap required will vary according to the press on which it is being printed, the sheet of paper being used, ink color, and position on the sheet of paper.