Simulate overprint question

[mpc999-n4I6RV]

Please help me understand the Simulate Overprint feature of Acrobat Pro 8. (I have tried Acrobat 8 Help and searching the forums, with no result.)

I am making a PDF from InDesign CS3 for printing on a digital printer. This is a document being repurposed from a press job that used CMYK plus 3 Pantone colors. The job printed fine on an offset press; no complaints from the printer. I am leaving it with the spot inks and letting the digital printer output CMYK. It prints fine on our in-house Xerox DocuColor laser.

The document contains a PSD graphic on a transparent layer and the background turned off, placed in InDesign. It sits on an InDesign background box filled with a spot color.

When I make a PDFX1-a file (transparency flattened), the PSD knocks out the background when viewed in Acrobat with Overprint Preview turned off. When OP is turned on, it displays correctly. The remote digital printer is telling me it prints on his machine with the white knockout, not the graphic showing.

When I send him a Press-Ready PDF exported from InDesign (live transparency), it displays correctly but still prints with the white knockout instead of the graphic.

When I modify the InDesign PDFX1-a preset to turn on Simulate Overprint in the Output panel, the resulting PDF prints the graphic correctly. What I don’t understand is that doing this converts all the Pantones to process, and turns the black type to four-color type. Since this is a digital output job, the all-spots-to-process doesn’t matter, but I don’t want 4-color black type.

In making the PDFs, I have tried the following Output combinations:

Color Conversion: Convert to Destination – both plain and Preserve Numbers options

Destination: US Web Coated SWOP v2

Profile Inclusion: both including and not including profiles

Clearly, I don’t understand the Overprint settings in Acrobat. The only file that works with the graphic ruins the type. What can I do?

[Glenn_McDowall]

cmyk can overprint a spot

cmyk can not overprint cmyk

simulate overprint takes this into consideration and emulates the colour produced by mixing the cmyk colour with a spot.

I think the 4 colour blacks are a different problem caused by conversion from one profile to another.

If you go back to the Indesign document and use the Ink Manager to convert the spots to cmyk before you Export to PDF it should all work as expected.

[mpc999-n4I6RV]

Thanks for the reply. Indeed, using the ink manager will solve the problem. However, I'm not understanding two things:

The CMYK graphic does not overprint the spot color background, it knocks it out. That's what I want and that's what separations show. So what does the Acrobat overprint setting have to do with it in terms of on-screen viewing and digital copier output?

My color settings in CS3 are synchronized to US Web Coated SWOP v2, so the working space and the destination space when I make the PDF are the same. In my examples, I don't understand why the type is becoming 4 colour.

[Glenn_McDowall]

mpc999 wrote:

The CMYK graphic does not overprint the spot color background, it knocks it out. That's what I want and that's what separations show. So what does the Acrobat overprint setting have to do with it in terms of on-screen viewing and digital copier output?

elementary my dear Watson.

earlier you said that there was a transparent background cmyk sat on top of a spot colour background. One of the ways that InDesign handles this is to use an overprinting white (0%cmyk) to produce the transparent shape, this isn't a problem if the spot colour remains a spot. If you change the spot to cmyk before you export to pdf then InDesign no longer has this technique as an option and so no longer uses overprinting white.

mpc999 wrote:

My color settings in CS3 are synchronized to US Web Coated SWOP v2, so the working space and the destination space when I make the PDF are the same. In my examples, I don't understand why the type is becoming 4 colour.

I don't understand this one fully but am guessing that Acrobat8 is not synced with CS3 and is using a different Working space, an alternative explanation is that transparency is affecting a more than obvious area, or there is some sort of Output Intent attached to your file.