Short definition Preflight:
In traditional preflighting, customer files are analyzed for resolution, font embedding, color spaces, hairlines or number of elements/pages to prevent non-printable files from entering production. Users can define their own criteria for what is printable and what is not.
By the way, a modern preflight is not only used for error search or correction, which I will explain in a separate article.
Preflight is always the first action, isn't it?
Many customers have set the automatic quality check (preflight) as the first workflow step. This is not wrong. But here are two reasons why in the vast majority of cases it is better not to preflight the original customer files, but to prepare the files in advance.
1. increase speed
2. reduce error rate
Quality of customer data varies greatly
Customers use a wide variety of software to create PDF files. This ranges from InDesign, Illustrator and CorelDraw to Word and PowerPoint. The range of file formats with which the print service provider is supplied is correspondingly wide: PS, XPS, EPS and DCS 2.0 files as well as PNG, JPEG, GIF, TIFF, JPEG 2000, Photoshop EPS and Photoshop PSD image files.
The skill level of the users ranges from beginners to professional agencies. The quality and complexity of the delivered files is correspondingly different.
The Asura module "Create PDF" converts all these mentioned file types into PDF. During the format conversion - as described below - various file optimizations are carried out in the background. The generated PDF then goes into the preflight.
What slows down the preflight?
Very large file sizes or very complex files slow down the entire workflow. Every tool that deals with such a file groans and moans. A few examples:
- File contains winter landscape, each snowflake is an extra vector graphic. This results in files with over a million elements and an unnecessarily large file volume
- File shows a bee, which is not embedded as an image, but drawn with 100.000 vectors. Think of a page with 10 bees, that's one million vector elements...
- Typically, in most software applications when exporting to PDF, each line is saved as an extra text element - if you are lucky. Mostly there are even several text elements per line -> many text elements in file. Documents with several thousand pages and several fonts are actually always designed in such a way that each font is embedded on each page. This inflates the file size and is unnecessary.
- Documents often contain elements that are completely outside the print area or are invisible because they are clipped. In other words, there are elements that have no influence whatsoever on the display or printing. These elements are superfluous.
- Elements can be on invisible layers. Then they are unnecessary, but still increase the file volume.
- The more complex and larger a file, the slower the preflight (and of course any other action in the workflow).
How can I speed up the preflight?
The preflight speed is increased if the file is simplified and reduced in size beforehand. Depending on the nature of the file, one or more preparation steps may be necessary.
The module "Create PDF" of the prepress suite Asura optimizes the structure of a PDF file. Files are virtually dismantled into their individual parts and - with our knowledge of how good, lean PDF files must be - reassembled. This is done fully automatically and our users decide for themselves which aspects should be optimized.
These optimizations mean that files contain fewer elements, have a simpler and more logical structure and the file size is reduced. This accelerates the preflight.
Am I even allowed to change customer files before printing?
This is a question that we keep hearing and that we answer with a clear "yes". A number of measures are essential in order to be able to print a file at all. At the latest the RIP will change the file massively. Here are some examples of automatic interventions in the customer file:
- Customer sends RGB file -> automatic conversion to CMYK with correct profile
- Customer sends file with special colors, but orders 4C
- Customer sends file as in screenshot: one can assume that white areas should not be printed
- File is delivered without bleed
- File contains transparent elements
- File is so complex that the RIP cannot process it
Reduce error rate
Which files are removed by the Preflight?
In principle, each user determines which file criteria are unwanted in the workflow and shall lead to the file being rejected in the preflight. There are very different approaches: Some printers expect almost perfect files and reject the file if it is delivered with the wrong ICC profile, while others repair defective files laboriously, sometimes manually. Here is a list of preflight results that may cause some users not to print a file, but to send it back to the customer:
- Fonts are missing, are not included
- Printable annotations found in file
- Transparent elements found in file
- Page with too many pictures or graphics found in file
- Wrong color space, wrong ICC profile found in file
- Images with too high resolution found in file
- Images with too low resolution found in file
- Too high ink coverage found in file
- Spot colors found in file (when print is in CMYK)
- Pages with missing bleed found in file
All these file properties, which often lead to the exclusion of a file from the production workflow, can be corrected fully automatically so that they do not cause any problems during printing. The only exception: Point 7 - images with too low a resolution cannot be reliably "upsampled"..
How can I reduce the error rate?
If Preflight reports that files cannot be printed, there are three possibilities:
- Just print it anyway and hope,
- Repair file manually
- Contact customers and ask for correct file
The first variant is risky, the other two cause effort and delay. Therefore, it is advisable to keep the number of files rejected as low as possible. But how? According to what criteria?
As a general rule, I suggest that Preflight should only reject files which cannot be corrected automatically and reliably. Whether these errors are corrected manually or whether the file is returned to the customer is a question of efficiency and the time remaining until the start of printing.
The most important measure, however, is to precede the preflight with the "Generate PDF" module. Then only pre-optimized files will enter the preflight.
Preflight is an essential part of every prepress stage. The aim is to prevent files from being printed incorrectly. With good file optimization software, users can both increase the preflight speed and automatically correct many file errors. This results in more throughput. More files are delivered in better quality to RIP and print. It is advantageous not to preflight the original customer data, but first to fundamentally optimize it, preferably with the "Create PDF" module.
Who is the best contact person at OneVision?
If you are already a OneVision customer and want to get more out of your software, then contact trainer(at)onevision.com.
If you do not yet have OneVision software in use, please contact sales.ce(at)onevision.com.