9 Replies Latest reply on Apr 30, 2013 2:14 PM by rob day

    ID CS6 RGB objects set to overprint = KO in PDF

    Hahnium Level 1

      Hello:

       

      While I wait on the phone for Adobe support (+60 minutes now) I thought I'd post here to see if anyone in the community had any feedback on this topic.

       

      We recently discovered that objects created with an RGB build but set to overprint in InDesign will end up as KO type in an exported PDF file. I'm trying to find out if this is the expected behavior or if this is some type of bug in CS6. This even ocurs when all colors must be converted to CMYK or spot color, such as when exporting to X1a.

       

      From a technical standpont, RGB objects set to overprint are tagged with 'OPM 0' and CMYK objects are tagged as 'OPM 1'

       

      From our Enfocus resources:

      There are two “overprint modes”:

       

      • Standard overprint mode, also known as “OPM 0
      • Illustrator overprint mode, also known as “OPM 1” or “nonzero overprint mode”

       

      The difference between both modes lies in the effect of the tint value 0 for one of the CMYK inks:

       

      • In standard overprint mode (OPM 0), the tint value 0 of one of the CMYK inks in the foreground object has a knockout effect on the color rendering of the underlying object. In other words, a foreground ink with a C, M, Y or K value of 0 % erases the corresponding background ink. Here, the “foreground inks win” principle applies.

       

      • In Illustrator overprint mode (OPM 1), the tint value 0 is neutral: it is ignored (as if it were “not specified”) and has therefore no effect on the color rendering of the underlying object.
        • 1. Re: ID CS6 RGB objects set to overprint = KO in PDF
          Steve Werner Adobe Community Professional & MVP

          I don't have the answer to your question, but, interestingly enough, I just saw this dialog in InDesign that relates to this.

           

          I opened up a file set up with Digital Publishing intent in CS6. That sets the following: (a) swatches set to RGB, (b) Transparency Blending Space is RGB, (c) ruler units are pixels, (d) default page sizes are for tablets and smartphones.

           

          When I chose Overprint Preview (on this file I didn't create), I got this dialog:

           

          overprint_rgb.jpg

           

          This suggests to me that the issue is your Transparency Blending Space (found under the Edit menu). You might try turning that off. If you have no transparency, I don't think that would be a problem because my understanding is this feature is only used when there is live transparency in your file.

          • 2. Re: ID CS6 RGB objects set to overprint = KO in PDF
            rob day Adobe Community Professional & MVP

            I'm trying to find out if this is the expected behavior or if this is some type of bug in CS6.

            Seems like expected behaviour to me. What happens on an overprint depends on the CMYK values of the over and underlying object. So the results of 0|65|0|0 and 0|65|0|1 are very different

             

            Screen shot 2013-04-30 at 2.36.42 PM.png

             

            Screen shot 2013-04-30 at 2.36.59 PM.png

             

             

            An RGB version of the pink would have unknown CMYK output values because any CMYK profile could be used in the CMYK conversion for print.

            • 3. Re: ID CS6 RGB objects set to overprint = KO in PDF
              rob day Adobe Community Professional & MVP

              You could multiply an RGB object and get an "overprint" effect:

               

              Screen shot 2013-04-30 at 2.45.28 PM.png

              • 4. Re: ID CS6 RGB objects set to overprint = KO in PDF
                Hahnium Level 1

                Rob:

                 

                If you spec that color as RGB instead of CMYK, leave the overprint attribute checked and export a PDF I believe it will KO, even with overprint preview turned on in Acrobat.

                 

                If you place the exported PDF back into InDesign and export PDF again. I think it will overprint.

                 

                That's where it get's interesting.

                 

                Our trouble specifically is PDF ads supplied with these types of characterisitics that have to be placed back into InDesign. The check for "CMYK object is set to overprint but OPM is off" is not part of a standard PDF/X1a check. Go figure.

                • 5. Re: ID CS6 RGB objects set to overprint = KO in PDF
                  rob day Adobe Community Professional & MVP

                  If you place the exported PDF back into InDesign and export PDF again. I think it will overprint.

                  I'm not seeing that. Here I'm overprinting 65% magenta on 100% black and ID's Overprint Preview shows how it will separate. An RGB conversion of the same color is set to overprint but OP preview shows there will be no OP effect.

                   

                  If I export to PDF/X-1a and place back OP Preview shows the same. So I think ID's Overprint Preview accurately shows what would happen to an RGB object set to overprint:

                   

                  Screen shot 2013-04-30 at 4.16.58 PM.png

                  • 6. Re: ID CS6 RGB objects set to overprint = KO in PDF
                    Hahnium Level 1

                    Rob:

                     

                    Export the file with both InDesign objects and your X1a placed to PDF again and open in Acrobat. Does the Placed PDF overprint all the pink?

                    • 7. Re: ID CS6 RGB objects set to overprint = KO in PDF
                      rob day Adobe Community Professional & MVP

                      I get this, which makes sense because my first export to PDF/X-1a forced the object to CMYK and the converted RGB pink has 0% black. So is your problem clients are accidentally overprinting RGB objects and are surprised by the overprint effect? Because I think if I had initially exported as PDF/X-4 the RGB pink would still be knocking out in the re-exported PDF.

                       

                      Screen shot 2013-04-30 at 4.44.24 PM.png

                      • 8. Re: ID CS6 RGB objects set to overprint = KO in PDF
                        Hahnium Level 1

                        So is your problem clients are accidentally overprinting RGB objects and are surprised by the overprint effect

                        Rob:

                         

                        You nailed it. I didn't try the PDF/X4 workflow you mentioned, but I'll have to see if the same thing occurs. It's just very surprising that separation preview is yielding different results between InDesign and Acrobat. I'm going to be adding that extra OPM preflight check to our supplied PDF workflow.

                        • 9. Re: ID CS6 RGB objects set to overprint = KO in PDF
                          rob day Adobe Community Professional & MVP

                          Here's export to X4 placed back and re-export to PDF/X-1a. Could you get your clients to provide X4?:

                           

                          Screen shot 2013-04-30 at 5.11.32 PM.png