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  • Late stage conversion

    I am blessed to work in a rather high-end in-plant shop. I don't have the misery that you commercial folks do dealing with the stuff designers throw at you. But I do need help understanding the advantages and/or disadvantages in early vs. late profile conversion.

    For years we have been converting all our images to CMYK before importing them into Indesign, and convert any spot colors our designers use as well and then output an X-3 PDF. If I output to a given profile as an X-1a PDF, I know my Adobe RBG images will convert, but the Indesign spot colors are throwing me off.

    1. Why won't an X-1a PDF convert an Indesign spot color to CMYK?
    2. Why does that same color convert differently (using the same profile) when it is saved as Lab, CMYK, or RGB in Indesign? The numbers in Acrobat vs. Indesign's separation preview are different.

    Thanx for any input in advance.

  • #2
    Re: Late stage conversion

    Park,

    "1. Why won't an X-1a PDF convert an Indesign spot color to CMYK?"

    It will as long as it is set to do so in Ink Manager (accessible from Swatch palette and also when printing or exporting PDF, in the Output tab > Ink Manager)

    2. Why does that same color convert differently (using the same profile) when it is saved as Lab, CMYK, or RGB in Indesign? The numbers in Acrobat vs. Indesign's separation preview are different."

    Are the same RGB and CMYK profiles used in Acrobat as in InDesign? If not, that's part of your problem. If so, then also think about this:
    1. If outputting RGB from InDesign, need to use the Edit menu > Transparency Blend Space > Document RGB. Otherwise, use Document CMYK as Transparency Blend Space.
    2. In Ink Manager, if you check 'All Spots to Process', InDesign will use the CMYK equivalents provided by PANTONE for the PANTONE colors. If outputting as Spot, when preflighted in Acrobat Pro, will tell you the Spot color's Alterrnate Colorspace is Device CMYK color. These CMYK values will be used in the case the Spot color is converted to process/output as process at any point in the workflow.
    3. In Ink Manager, if you check 'Use Standard Lab Values for Spots', InDesign will use the Lab equivalents provided by PANTONE for the PANTONE colors. If outputting as Spot, when preflighted in Acrobat Pro, will tell you the Spot color's Alterrnate Colorspace is Lab color. If converted/output as process, InDesign (or later in the workflow) will take PANTONE's Lab values of the spot color, use the Document CMYK profile (which must describe the device/ink/paper that it will be printed on, such as GRACoL2006_Coated1v2 for #1 paper) and the default Relative Colorimetric rendering intent with Black Point Compensation to get the CMYK values needed to as close as possible match the actual PANTONE color's appearance.

    Don

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    • #3
      Re: Late stage conversion

      Hi Don,

      We use an all RGB workflow also and convert to cmyk on export from Indesign, by saying...

      "1. If outputting RGB from InDesign, need to use the Edit menu > Transparency Blend Space > Document RGB. Otherwise, use Document CMYK as Transparency Blend Space."

      You mean for sending RGB out of Indesign for conversion downstream right? If converting out to cmyk out of Indesign we should be using "Document CMYK as Transparency Blend Space" correct?
      Just asking for my own peace of mind.

      If I receive a file from our designers with a spot color where it should have been process, or we're going to print it as process, I address that in the swatches palette, thereby fixing the file for archiving. I've normally just used the solid to process numbers in Photoshop to get the cmyk numbers. I suppose I should get the numbers, convert to Lab with Absolute and then to my G7 profile? Or, is color picker giving me cmyk numbers based on the G7 profile since that profile is my default in color settings?

      Don, we're still going with G7, working pretty well, press could pay closer attention to gray balance but pretty good matches overall. Realized this week, duh, gray balance is only thing that controls color with this method, curves only control neutral print density tone curve, or lightness\darkness, as long as they are gray balanced on press, whatever the dot gains, inks, paper that day, we should have a "similar" color appearance. Our previous methods, SWOP and custom profile, we controlled color with density and dot gain curves in the rip to give desired results at press, with G7, gray balance is the only thing to control color on press, during the run anyway. If we achieve gray balance and our inks colors are still in Lab tolerance, we're finding pretty good matches to the G7 proof, but having trouble getting press to look at gray balance, instead of just densities.

      Have a good one!
      Terry

      Terry

      Comment


      • #4
        Re: Late stage conversion

        "You mean for sending RGB out of Indesign for conversion downstream right?"

        No. Transparency Blend Space needs to be set to RGB if outputting RGB out of InDesign (such as when exporting PDF using Standard setting, which converts CMYK in InDesign to RGB in the PDF, and you want it to look the same in the PDF as in InDesign, so you have to set the Transparency Blend Space to RGB before making the PDF, and then change it back to CMYK to export PDF/X or print PostScript). I always make sure I save the document with Transparency Blend Space set to CMYK.

        "If converting out to cmyk out of Indesign we should be using "Document CMYK as Transparency Blend Space" correct?
        Just asking for my own peace of mind"

        Yes, that's correct.

        If I receive a file from our designers with a spot color where it should have been process, or we're going to print it as process, I address that in the swatches palette, thereby fixing the file for archiving. I've normally just used the solid to process numbers in Photoshop to get the cmyk numbers."

        That's what I do for now, just use the same PANTONE-provided CMYK numbers. But I don't print to G7 yet (except for a couple customers).

        "I suppose I should get the numbers, convert to Lab with Absolute and then to my G7 profile?"

        What numbers? If PANTONE-provided CMYK numbers, what ICC profile would you assign to the numbers before doing a conversion to GRACoL2006_Coated1? I would just scan a printed piece or pick PANTONE's Lab values to get what I wanted to match as close as possible. I would then plug those Lab numbers in Photoshop color picker and see what the CMYK numbers were given (as long as the CMYK profile in color settings is GRACoL2006_Coated1 profile if printing on #1 paper, or maybe use an uncoated profile if printing on uncoated paper).

        "Or, is color picker giving me cmyk numbers based on the G7 profile since that profile is my default in color settings?"

        Yes. When I start printing to GRACoL2006_Coated1, I've thought about doing tests again, because from what I see, starting with Lab values (either PANTONE-provided Lab values, or Lab values obtained from scanning a printed piece I want to match the color of with a spectrophotometer), and using color management, the default Relative Colorimetric Intent with BPC, and the correct output profile for the paper type to get the CMYK values, is what is giving the best results that I've seen (and Michael Eddington has said the same).

        Terry, are you one of the ones that used the Excel calculator I made? If so, did you use the NPDC portion of the calculator or the TVI/dot gain portion?

        As far as G7, it's used to set up the press/paper to get to solid aims and then correct plate curves to get gray balance while still being within tolerances on the solids and overprints. During production, my understanding is that the pressman would try to get to gray balance and not do as many readings as he/she has traditionally. (Note: density readings wouldn't have to be done if gray balance is reached, since the paper's already been set up using G7). I've heard that the pressman would check the gray balance with a spectro-dens set to visual density to make sure all three CMY are equal at 50 (a low one would mean that that ink's density needs to be raised until gray balanced), and maybe check the Lab values of the solids to make sure still within tolerance (which should be). I've heard that after setting up to G7, in production pressman would use the tools he/she is accustomed to, which is density.

        You have a good one too!

        Don

        Comment


        • #5
          Re: Late stage conversion

          Don,

          "Terry, are you one of the ones that used the Excel calculator I made? If so, did you use the NPDC portion of the calculator or the TVI/dot gain portion?"

          Yes, I used the NPDC portion. Yes, we are using density first at startup (no spectro at press) to get close then tweaking to gray balance from there. We us the gray balanced densities to start up with each time. Problem is getting them to check the gray balance instead of just running to the densities that worked last week. Oh well, we'll get there eventually, I guess.

          Thanks again,
          Terry

          Comment

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