Creating colour separations from PDF

Those who know us know that a central role of our work is the creation of technically valuable tutorials for brand owners, designers, agencies, printers and converters. We usually do this on behalf of our customers in order to present new materials, processes and technologies on the basis of special demo packaging and to demonstrate and illustrate their use in everyday printing. Since these demo packages are usually very elaborately crafted and also finished and we often work at the limits of what is currently technically feasible, especially with new material and process combinations, our tutorials provide a perfect interface between the technical support of our customers and the production departments of their customers and simplify the planning process immensely.

We have therefore decided to publish many of these tutorials here on LinkedIn, to link them to the corresponding customers and thus to create added value for all LinkedIn members, our customers and ultimately also for us through the exchange on these tutorials with all those involved.

Today we would like to start with a topic that I have already encountered very often as a query and which apparently often leads to process-related limits for many designers, pre-press specialists and printers. Those who know our tutorials have already seen that we almost always work with views of the colour separations of our print jobs. But how do you get hold of such colour separations? Especially if you don't work in prepress and can pick up these separations from a rip, don't have an ApogeeX workflow, no access to Esko or PitStop tools. Well, as long as you work with the Adobe Collection, you can do this with on-board tools. Even easier than many think and above all vector-based and highly precise. So precise, in fact, that the separations created in this way can later even be used to determine the exact area coverage, which is important information especially in process planning, e.g. for calculating the required inks, varnishes and adhesives. However, we will explain this to you in one of our upcoming tutorials.

As an example, I have deliberately chosen a complex packaging job that we were involved in project management for PrintCity a few years ago and which was produced on a Gallus ICS 670 in both offset and flexographic printing. We're concentrating on the offset version today, as this will certainly be closer to the production parameters of most designers and print service providers.

This print job for secondary packaging for sweets used four food-safe spot colours from Epple, three food-safe coatings from WEILBURGER Graphics, an effect pigment from Merck and two hot-stamping finishes from Kurz on the outside.

The printing forme was a mixed forme on which two packaging blanks and two DIN A4 samples were imposed.

 

As you can see from this screenshot, all the special forms were already included in a single print PDF and we had also already created the varnish bars and the ink take-off bars, which will later be important for calculating the area coverage. The only thing that is not yet included in these data is the printing company's printing wedge. For this, however, you only need to add a flat rate of 1 - 2 % area coverage depending on the wedge used.

Of course, in Acrobat you can now display the individual colour separations in such a composite file separately at any time, as can be seen in the following screenshot using Pantone 376 C as an example.

 

But if you want to have these extracts as a separate PDF, for example to show them in a tutorial, this is not quite so easy, unless you want to work with screenshots at this point for quality reasons.

 

The Workflow:

The first step needed to extract the colour separations is to export this print PDF as a postscript file. This reduces all transparencies that are possible and allowed since PDF/X 3 and converts the file including all trappings, overprinting elements and separations to a postscript-compatible flat layer.

 

Because of a bug in Acrobat that has not been fixed for years, you have to make sure that the file names are not too long. Otherwise you will often get error messages in later steps that you cannot explain at first. A maximum of 32 characters has proven to be crisis-proof. As always, you should refrain from using special characters, umlauts or spaces in the file name. This is not a must, but it often saves unpleasant surprises once you have become accustomed to this nomenclature.

Attention: Please give this file a different name (before the .ps suffix) than the source file. Otherwise the source file will be overwritten at the latest when the new PDF is ripped and will be irrevocably lost.

 

The next step is to select the correct settings for exporting this PostScript file. It is mandatory to select Generic PostScript Printer as the printer description language. All other settings will cause the rip process to be aborted later.

 

Warning: The Generic PostScript Printer is a virtual printer with a PostScript print driver which, depending on the operating system used, must first be created if it has not already been done. Adobe offers instructions for Mac OS X (all versions) here and instructions for Microsoft Windows XP here.

Now all that remains is to select the colour separations option under the Output tab.

 

And the export can be started by clicking on Save.

 

Depending on the size and volume of the vectors used in the print file and, of course, the performance of the computer used, this process may take a little longer. Especially since the PostScript file does not use any compression, these files are usually very large. For complex print jobs with many vectors, a few gigabytes are possible. For this reason, you should not start this process on a computer that is too small and always make sure that you still have enough hard disk space available.

 

The next step is to start Acrobat Distiller and select High Quality Printing as the setting.

 

Now simply add the PostScript file you just created to the queue and start the RIP process.

 

In newer versions of the Distiller, there is now another security warning, which you simply have to confirm.

 

If the job ran without errors, it should have been saved in the source folder and the distiller's log file should acknowledge the end of the job without an error message.

 

Next, open the PDF file you have just created and check that it has been ripped cleanly.

 

The final result should be a PDF file that has exactly the same format as the print PDF and as many pages as there were colour channels in the print file. For each individual separation, which is now available as a black separation, a new page was created in the PDF.

And the best thing about it: at the top of the page overview (x of y), all pages are now also marked according to the assigned colour names, which makes it much easier to assign the colour channels.

The following are the individual colour separations of this demo job:

 

Of course, not all separations are needed for further processing. In particular, auxiliary separations such as glue application or additional registration marks, info and guidelines can usually be neglected. But all separations are still available in (PostScript) print quality. Where vectors were created in the print file, they are still vectors, just separated in colour and prepared with all trapping and underfilling and according to overprint settings. The individual pages from this process can therefore even be reopened in Illustrator and edited there.

If you want to use these separations in colour (e.g. if you want to display magenta in magenta), we recommend that you simply export the required pages of the PDF as high-resolution tiff files and then colour them accordingly later in InDesign, for example. Of course, they are now bitmaps and no longer vectors, but the amount of work is so much less than recolouring the vectors all individually.

Conclusion: The process of digitally separating print data is actually quite simple - provided you have the appropriate knowledge - and once you've done it a few times, it's not much of a challenge. Personally, we have set up an additional automation and thus only need to throw the print PDF into a hot folder and then receive the fully separated final file including the exported tiffs fully automatically. However, this is only useful if you often need such separations, as we do.

If you liked this tutorial, please give us a Like or leave a comment. As mentioned at the beginning, we are now planning to publish tutorials on a regular basis via this new newsletter on all topics of our professional everyday life around the printing, packaging and media industry - but also sometimes on software, app and web development - and are of course happy about every feedback, every recommendation, every share and every constructive criticism.

Social networks thrive on dialogue and exchange and we look forward to an exchange with you!

 

PS: The project along with the associated tutorials and separations used there can be found on the PrintCity website.


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