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  • Press compensation curves for FM screening

    Hello all,

    Management wants to create new compensation curves by printing P2P charts for CMYKOGV and they want to output the OGV as stochastic (FM). Just wondering if running P2P’s as stochastic is common practice? Aren't they supposed to be printed with an AM screen?

    Thanks

  • #2
    Hi Mac,
    The P2P51 will get you your cmyk data but you'll have to test the ogv inks separately and/or combined in a muli-ink chart. Have a look through this document, it should cover most of your cmykogv calibration questions. -dan

    http://www.techkonusa.com/wp-content...aper-Final.pdf

    Comment


    • #3
      Thanks for the response. To be clear, ganged up on one form we have the P2P for CMYK and also P2POGB charts for the extended gamut. So all 7 colors are represented on one form.

      Comment


      • #4
        Originally posted by MACLOUD View Post
        Hello all,

        Management wants to create new compensation curves by printing P2P charts for CMYKOGV and they want to output the OGV as stochastic (FM). Just wondering if running P2P’s as stochastic is common practice? Aren't they supposed to be printed with an AM screen?

        Thanks
        Originally posted by MACLOUD View Post
        Hello all,

        Management wants to create new compensation curves by printing P2P charts for CMYKOGV and they want to output the OGV as stochastic (FM). Just wondering if running P2P’s as stochastic is common practice? Aren't they supposed to be printed with an AM screen?

        Thanks
        It's more complicated than just building curves.

        A few thoughts:

        - If you intend to print the OGV inks FM then why not print the CMYK inks FM?
        - Are you using the extra inks to enhance images or simulate spot colors or both?
        - Most offset shops that I've worked with do not load the press with all 7 inks. Instead, they use 6 and just replace one of the 6 as needed by the job.
        - You need to make sure that the inks used for OGV are designed to run as "process" colors (i.e. be screened and wet trapped). This is a major point of failure and can be exacerbated with FM screening.

        Examples of inks (solid and screened) formulated correctly (left) for the O printer vs inks not properly formulated (right) and just the screen (badly formulated)


        Orange solid compared.jpgOrange screens compared.jpgOrange screen.jpg

        Comment


        • #5
          It's more complicated than just building curves.

          A few thoughts:

          - If you intend to print the OGV inks FM then why not print the CMYK inks FM? - I believe the main purpose is to avoid moiré patterns

          - Are you using the extra inks to enhance images or simulate spot colors or both? - just to simulate spot colors

          - Most offset shops that I've worked with do not load the press with all 7 inks. Instead, they use 6 and just replace one of the 6 as needed by the job. - we combo our runs, so usually we’re running orange violet and green.

          - You need to make sure that the inks used for OGV are designed to run as "process" colors (i.e. be screened and wet trapped). This is a major point of failure and can be exacerbated with FM screening.
          Examples of inks (solid and screened) formulated correctly (left) for the O printer vs inks not properly formulated (right) and just the screen (badly formulated) - as much as I would love to be, I am not involved in the formulation of the inks so I can only assume they are correct. We have an ink department within the press room, occupied by a representative from the ink company so I have to assume they know what they are doing.

          Thanks

          Comment


          • #6
            Just in case you haven't run FM before, you can expect dot gains to almost double.
            For example, if TVI is 20% @ 175lpi AM, then 20um FM might be 40%.

            Comment


            • #7
              Originally posted by MACLOUD View Post
              It's more complicated than just building curves.

              A few thoughts:

              - If you intend to print the OGV inks FM then why not print the CMYK inks FM? - I believe the main purpose is to avoid moiré patterns

              - Are you using the extra inks to enhance images or simulate spot colors or both? - just to simulate spot colors

              - Most offset shops that I've worked with do not load the press with all 7 inks. Instead, they use 6 and just replace one of the 6 as needed by the job. - we combo our runs, so usually we’re running orange violet and green.

              - You need to make sure that the inks used for OGV are designed to run as "process" colors (i.e. be screened and wet trapped). This is a major point of failure and can be exacerbated with FM screening.
              Examples of inks (solid and screened) formulated correctly (left) for the O printer vs inks not properly formulated (right) and just the screen (badly formulated) - as much as I would love to be, I am not involved in the formulation of the inks so I can only assume they are correct. We have an ink department within the press room, occupied by a representative from the ink company so I have to assume they know what they are doing.

              Thanks
              Sorry, did you say "assume they are correct." LOL

              That's a dangerous assumption. In my experience ink companies do not share or archive information between divisions or in-plants. So, IMHO, you need to explain to your in-plant exactly what you intend to do and what you need in terms of ink performance. Work with them and don't assume. Otherwise you risk the inks doing what the samples I've posted did. (I've seen a shop kick out their in-plant ink guys and switch to a different supplier because the existing in-plant couldn't formulate the inks to run properly).

              You can avoid moiré with AM screens by using the "missing" angle. For example, Orange will not print over Cyan so you can use the Cyan angle for the Orange printer. The problem with mixing AM and FM on the same file is that they have different ink/water balance needs and they react differently to SID moves. That might cause issues in your presswork. Also they have different dot gain profiles which could prove difficult managing curves in your workflow. It's usually best to print all AM or all FM. But, you might get away with it. Personally I'd prefer to run everything FM - that typically how label and packaging offset printers are running. (BTW, it's also how flexo printers that adopt fixed palette printing are starting to do).

              The shops that I referenced are using only 6 colors at a time were doing combo sheets. The concern was having an ink unit sitting idle on the press if that ink wasn't being used. Instead they ganged jobs so that each used only the 6 inks on press (typically O or R plus V or B). Then one ink would be swapped out (typically the B/V) and replaced with G. So, for example, they would print CMYKOV then print CMYKOG. One ink change and wash up. This requires auditing of the range of spot colors you are trying to hit and some planning in prepress. Your situation might be different.

              Don't forget to take ink sequence into consideration. Try to keep the colors that will likely print together as far apart as possible. For example KCMYVGO is a better sequence than KCMYOGV. Most shops doing this type of work dedicate one press to only print this way. So they'll set the ink sequence to optimize the potential for dry trapping. E.g. VKCOMGY. Consider what works best with your press configuration.
              Last edited by gordo; 02-08-2019, 04:50 PM.

              Comment


              • #8
                Thank you all for the detailed info.

                I knew the word “assume” would cause some sparks lol...

                Since we run a lot of combo runs, there seems to always be one or 2 units that need a little help, ie, bring up the magenta in the midtones by 5%, reduce the yellow in the quarter tone 10%, etc. We are asked quite frequently to make curve adjustments while the job is on press. Management feels that with a stochastic screen, we won’t be able to make on the fly curve adjustments as easily as with a conventional screen. That is the reason we don’t plan on going FM on every color. Which leads me back to the direction of my original question... how can a color with an FM screen be manipulated on the fly? Let’s say the violet needs a boost on press, can it be boosted using a compensation curve?

                thanks

                Comment


                • #9
                  Originally posted by MACLOUD View Post
                  Thank you all for the detailed info.

                  I knew the word “assume” would cause some sparks lol...
                  I'm glad I met your expectations! LOL

                  Since we run a lot of combo runs, there seems to always be one or 2 units that need a little help, ie, bring up the magenta in the midtones by 5%, reduce the yellow in the quarter tone 10%, etc. We are asked quite frequently to make curve adjustments while the job is on press.
                  That's a very bad/inefficient/costly way to work. I've only been to a few shops that work that way (adjusting curves in live production). It usually indicates that there is a problem somewhere in the process that should be corrected. But, whatever it takes to get the job out the door I guess.

                  Management feels that with a stochastic screen, we won’t be able to make on the fly curve adjustments as easily as with a conventional screen.

                  That is the reason we don’t plan on going FM on every color. Which leads me back to the direction of my original question... how can a color with an FM screen be manipulated on the fly? Let’s say the violet needs a boost on press, can it be boosted using a compensation curve?
                  There is no difference in making curve adjustments - on the fly or not.

                  You will likely have problems if you mix screens as per the reasons mentioned before. Since you're in the States, have a look at house brand labels under a loupe. You'll find that the ones printed with FM screening do not mix screens - they're 100% FM.

                  Tone reproduction curves (dot gain compensation curves) are created and/or adjusted the same way for FM as with AM.
                  Last edited by gordo; 02-08-2019, 11:59 PM.

                  Comment


                  • #10
                    I will pass all this info up the chain of command and hope they listen, thank you once again.

                    Comment

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