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  • Overprint Mode 0 and 1

    I have recently downloaded test patches from the Ghent Work Group and run then through our RIP to test compliance. Many of the patches have been set up with two modes of overprint OPM 0 and OPM 1. I have tried to find further information regarding these two set ups but haven't had much luck. Does anyone know what the differences are or can point me to documentation which may help.

  • #2
    Re: Overprint Mode 0 and 1

    >I have recently downloaded test patches from the Ghent Work Group
    >and run then through our RIP to test compliance. Many of the patches
    >have been set up with two modes of overprint OPM 0 and OPM 1. I have
    >tried to find further information regarding these two set ups but
    >haven't had much luck. Does anyone know what the differences are or
    >can point me to documentation which may help.

    OPM is documented in the PDF Reference.

    Martin Bailey

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    • #3
      Re: Overprint Mode 0 and 1

      You can get a good explanation by downloading the AltonaTestSuite documentation from www.eci.org

      Paul Santer

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      • #4
        Re: Overprint Mode 0 and 1

        Thanks for the reply Martin, and excuse my ignorance but, could you expand further on the "PDF reference" you refer to. Is this a particular document or reference data associated with the patch.

        Thanks

        Comment


        • #5
          Re: Overprint Mode 0 and 1

          Ritchie,

          OPM 1 is needed when you have an CMYK Object (defined in DeviceCMYK) overprinting another (Device)CMYK Object.

          Meaning:

          DeviceCMYK overprinting another DeviceCMYK and OPM = 0 will result in the color tints of the CMYK object on top.
          DeviceCMYK overprinting another DeviceCMYK and OPM = 1 will result in the color tints of the CMYK object on top and the tints of the CMYK object underneath, if the topmost tint of the colorant has 0% - meaning if 0% cyan is defined, then the cyan from the object below will be used.

          Also: a DeviceCMYK image can not overprint any other CMYK object.

          If you need a CMYK object overprinting another CMYK object no matter how OPM is set up, the CMYK object has to be defined in DeviceN.

          Again: more in detail definition can be found in the PDF Reference Manual.

          Best regards,
          Peter Kleinheider

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          • #6
            Re: Overprint Mode 0 and 1

            Comment


            • #7
              Re: Overprint Mode 0 and 1

              Thanks guys

              I have located the PDF reference document. It's a heavy read and not having any programming experience much of it I find difficult to understand. But no more than I would expect from a very complex subject.

              As the GWG patches have objects set up in OPM 0 and OPM 1. I presume these are set at application level, or does the source colour space determine which overprint mode corresponds with particular files.

              Comment


              • #8
                Re: Overprint Mode 0 and 1

                Ritchie,

                OPM can be set for every object. OPM is not part of the color space, but of the graphic state.

                Regards,

                Peter Kleinheider

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                • #9
                  Re: Overprint Mode 0 and 1

                  Peter

                  I understand OPM can be applied to objects within application progams such as Adobe Illustrator (i.e. fills and strokes) but I'm struggling to understand how it's possible to set up a file with either OPM 0 or OPM 1 settings. Perhaps this refers to Transparrency settings?

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                  • #10
                    Re: Overprint Mode 0 and 1

                    Ritchie,
                    when creating a PDF via distiller, OPM can get controlled via the distiller settings.
                    When you export a PDF, OPM is set by the application. There is no way to explicitly turn it on or off. The application is responsible to use OPM accordingly. You actually should not bother too much where it comes from. It is rather important to honor OPM when generating an output. Thus the Ghent Output Suite gives you a great tool to check on that,
                    Special care needs to be taken when going PDF->EPS->PDF since OPM might get lost this way.

                    Regards,
                    Peter Kleinheider

                    Comment


                    • #11
                      Re: Overprint Mode 0 and 1

                      Thanks for that Peter

                      Many of the GWG swatches have ojects/images set up both in OPM 0 and OPM 1 and some of these are rendering incorrectly through our TrueFlow RIP either with honouring or not honouring the overprints, so I'm trying to understand how the swatches are created differently in order to form an opinion of certain settings I may need to adjust in order to render both OPM 0 and OPM 1 swatches correctly.

                      Thanks for your patience with me, it will sink in eventually.

                      Regards
                      Ritchie

                      Comment


                      • #12
                        Re: Overprint Mode 0 and 1

                        Ritchie,

                        again, when honoring overprinting, the PDFs have to output correctly. You should not care where it comes from or how it got created.

                        Very often CTP workflow's change the overprint settings in one of their modules like trapping or color management.

                        Do you output the patches one by one or do you amalgamate them?

                        How do you check the result? Is there a resulting PDF to look at?

                        Regards,
                        Peter

                        Comment


                        • #13
                          Re: Overprint Mode 0 and 1

                          "You should not care where it comes from or how it got created".

                          Peter
                          I know where you're coming from Peter but my brain does find it helpful if I understand as much as possilble with issues, so I can reach a suitable solution easier.

                          I am analysing the patches individually, by individually I mean each file, some files have 4 patches some have a lot more.

                          From an interpeted TrueFlow file I am able to output to Outline PDF (although this is still subject to overprint rules) and Tiff files. These "Ripped" files can be output to calibrated Epson printers for hi resolution proofing purposes or direct to plate.

                          I am viewing these swatches printed on our Epson 1055 Pro 6col printer, calibrated and profiled to our Roland 700 6 col litho press.

                          Comment


                          • #14
                            Re: Overprint Mode 0 and 1

                            > {quote:title=Ritchie wrote:}{quote}
                            > I know where you're coming from Peter but my brain does find it helpful if I understand as much as possilble with issues, so I can reach a suitable solution easier.

                            Excuse my ignorance, but how this help to find a suitable solution? Ether your workflow can handle those patches correctly by honoring the overprint settings or not. If not because it is not supported, you might run into issues where it is the fault of the workflow because the output was messed up.

                            > {quote:title=Ritchie wrote:}{quote}
                            > but I'm struggling to understand how it's possible to set up a file with either OPM 0 or OPM 1 settings.

                            if you create a PS and use distiller, you can control OPM by activating the "Illustrator Overpint Mode" in the Advanced-tab.

                            Another way where it can come from:
                            a text is defined in black (DeviceGray). In order to have this text overprint another CMYK element, it has to be converted to ether DeviceCMYK or Separation Black, since DeviceGray can not overprint DeviceCMYK. If the element only gets converted to CMYK and set to overprint but OPM is 0, it is still knocking out.

                            Besides that I do not know of any other way to directly control OPM. I would have to do some research.

                            Regards,
                            Peter

                            Comment


                            • #15
                              Re: Overprint Mode 0 and 1

                              Pitstop will show and allow you to change the OPM setting. Its found in the Prepress-->Overprint tab of the Inspector dialog.

                              I don't know of any desktop creative apps that give direct control of OPM to the user. Many of the files out there that are used to test some of the more obscure PDF operators are hand written by developers.

                              Cheers,
                              Rob

                              Comment

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