Overprinting & Trapping in Adobe PDF Quick Note
As Acrobat 5.0 has this new cool “Overprint Preview” feature. And as Barney Kassabian has prompted me, this raises the whole issue of QuarkXpress and overprints/trapping.
Over the last 2 years, I was under the impression that overprints were retained in composite Quark Postscript files. I was only partly correct, or a bit wrong. You choose. To clarify, I have been experimenting.
Overprinting in QuarkXpress 3.32 to Adobe PDF
If you save out of QuarkXpress 3.32 as an EPS, Quark keeps the overprinting settings (as set in the View>Trap Information palette). Distilling this with Acrobat Distiller 4.05 or 5 results in a PDF where the overprint is retained. New in Acrobat 5.0 – you can view this on screen.
However, if you use the Adobe preferred method of “Printing” via AdobePS to the Distiller (Mac: Create Adobe PDF, PC: Acrobat Distiller printers) — the overprinting information is NOT retained in the Postscript.
If you are a Postscript jockey, you can see the simple command is just plain missing from the Printed .ps file:
What about QuarkXpress 4.x?
Thankfully, QuarkXpress 4.x exports the “stovp” Postscript command when printing. Other trapping details are NOT retained in the composite Postscript output.
“T stovp‘ — set overprint on the next drawn object to true — in English. This particular command (stovp) is defined in both the EPS and the standard Postscript headers of a QuarkXpress 3.32 Postscript file; its a QuarkXpress specific command in their Postscript header. Its just that the Composite Postscript printed from Quark happens to be missing the appropriate overprint command.
If you are wise to the ways of Postscript, or willing to shoot off your own foot, you can insert this command into the Printed postscript file from the the EPS version and viola! you have overprinting in the Printed output. Be warned! This may result in a Postscript file that is no longer valid; it may not RIP; and the Distiller may ‘spit its cookies’ at you. You have been warned. Don’t try this at home. I am a trained professional. Your mileage may vary. Insert standard legal disclaimer here.
The good news in this is that overprint information IS LEFT in the EPS files; placed from Illustrator or Quark generated EPS.
So, what is the recommended workflow? Out of QuarkXpress 3.32, save each page as an EPS file. Place each of these EPS files BACK into a QuarkXpress document (or InDesign document
Please note: you should not nest EPS file inside EPS files inside EPS files. Why not? Each EPS saves a graphic state before srawing its contents; at least once. There is a limit of 15 of these in Postscript 3; and depending on the content in the EPS, the RIPÂ may cause a ‘limitcheck’ Postscript error.
Also please note: When creating and Distilling EPS files from QuarkXpress, note that Quark does not embed the fonts. This restriction forces you to Distill on the creating machine. Otherwise, there is the risk that you create a PDF where the fonts are not embedded.
And the resulting PDF displayed in Acrobat 5.0 with Overprint Preview turned on:
Another method, albeit more prone to trouble, is taking the EPS files created above and Distilling these directly. The trouble that you might find in this method is that the Distillers “Default Page Size” is used,Â UNLESS you have “Resize Page and Center Artwork for EPS Files” checked in the Advanved Tab.
Evidendly, Quark’s Composite postscript output changed in QuarkXpress 4.0x — where the overprinting settings were retained. This is good news.
In a slightly similar fashion, QuarkXpress only saves its choking/spreading information when it prints Separations (usually not the default PDF workflow) or if you export as a DCS file. Once you save as a DCS file, you have separated your work. The choking/spreading is not saved when you save as EPS.
How do you “recompose” the separated DCS file/separated QuarkXpress file into a composite PDF? Apart from using a Modern Prepress application like InDesign? Adobe InDesign: Prepress Techniques
Thankfully, CreoScitex have an Acrobat plugin called CreoScitex Seps2Comp You can download a trial version Windows and/or MacOS from their web site.
It takes a multiple page PDF and allows you to “recombine” them into a composite PDF. In theory, common elements will exist in exactly the same place across the different plates. Its a matter of then adding the images/graphics back together and generating a composite image on screen. To do this manually involves creating channels in a Photoshop file (one channel for each of C, M, Y and K) — but you are left with a purely bitmap image.
Here is a screen dump of Sep2Comp in action. Its just a simple matter of applying a certain ink to the page that contains that plate. In Pre-separated Postscript, there is a special command that details how the separation is composed; Seps2Comp reads this and automatically applies the appropriate plate to ink.
And the final result
Also good news is that PageMaker 6.x and InDesign 1.x saves composite Postscript with Trapping & Overprinting by default. There is no need for all this jumpling through hoops and funny business.
This is a screen dump of Acrobat 5.0 showing the effect of trapping using the default settings. As many of these traps have been set to overprint – you can see the traps live on screen. Cool.
InDesign 2.0: Generating Composite, Trapped PDFs has more info on how to do with with InDesign 2.0.
Adobe’s Support site on Trapping:
Quark’s Support site has good overviews of Trapping and Overprinting:
Thanks to Shane Stanley for suggesting the nested EPS change; Barney Kassabian for prompting this research & supplying test files; Grant Gittus for running his experienced eyes over my comments.
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