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myDavey
Inspiring
July 4, 2016
Question

Dot Gain or Gray Gamma

  • July 4, 2016
  • 4 replies
  • 35755 views

Hi, I have a project I am working on as follows:

There is a pdf created in a different program (no access to that) and the black text is really RGB-black

This pdf also has gray text / designs in it

I want to export it from InDesign converting colors to grayscale (this way I get 100% black text)

My question is regarding the gray. After a lot of testing with exports and color conversions...

It seems to me that the closest color conversion (to the original RGB) is either:

  • Dot Gain 30%
  • Gray Gamma 2.2

My question is: does it matter which one I go with?

Also, after searching on the forums, I saw that most people speak about Dot gain 20% - why am I getting 30%? (does this matter)

Thanks,

David

      This topic has been closed for replies.

      4 replies

      rob day
      Community Expert
      rob dayCommunity Expert
      Community Expert
      July 5, 2016

      It seems to me that the closest color conversion (to the original RGB) is either:

      • Dot Gain 30%
      • Gray Gamma 2.2

      When you convert from RGB to grayscale the preview of the converted gray values would depend on the gray profile used to soft proof in AcrobatPro. So if you export a PDF with the destination as a gray, make sure that you set AcrobatPro's simulation profile to the same profile otherwise you will get a different preview for the same output numbers.

      So here I've exported an RGB image with 10% Dot Gain as the destination. I've used the PDF/X-4 preset so the 10% Dot gain profile is the default for soft proofing (see my post in your other thread). If I change the simulation profile the preview changes even thought the output numbers are the same:

      My 10% Dot Gain export soft proofed as 30% Dot Gain:

        M
        myDaveyAuthor
        Inspiring
        July 6, 2016

        @Rob, thanks a lot for this! This really cleared some things up for me (especially with acrobat! I realize now that I've been using that tool falsely until now!)

        After doing numerous testing, and checking with my printers, it seems that for my files Dot gain 30% worked best

        Thanks,

        David

        J
        Community Expert
        Jeffrey_SmithCommunity Expert
        Community Expert
        July 5, 2016

        There is a difference in the two conversions and can be seen in this comparison:

        If you read the values of the two conversions, there is no more than a 2 percent difference throughout.

        And IMO, the conversion used will not have any significant difference in the finished printed results.

          Abambo
          Community Expert
          AbamboCommunity Expert
          Community Expert
          July 5, 2016

          Look at this:

          Dot gain | what is it and how to compensate for it

          and this

          Setting Up Your Images for Final Output > Getting the Best Grayscales in Photoshop CS3

          ABAMBO | Hard- and Software Engineer | Photographer
          rob day
          Community Expert
          rob dayCommunity Expert
          Community Expert
          July 5, 2016

          and this

          Setting Up Your Images for Final Output > Getting the Best Grayscales in Photoshop CS3

          That link is pretty old. Later versions of Photoshop let you save out Black Ink profiles from any CMYK profile so you can avoid older, less accurate curve based profiles. So if I'm using US Sheetfed Coated as my InDesign CMYK profile, I can use a matching Black Ink-US Sheetfed Coated for my grayscale  conversions and previews. A press can't have two different profiles—gray and K normally print on the same plate:

          Abambo
          Community Expert
          AbamboCommunity Expert
          Community Expert
          July 7, 2016

          Anything with CS3 as a reference is pretty old!

          profiles should be adapted to your final output intend, as this avoids a transcoding of colours (blacks) and gives the most accurate results. But as long as the profile is attached to the PDF, you should be good with any profile. (This is, I'm aware of it, not completly correct...)

          ABAMBO | Hard- and Software Engineer | Photographer
          barbara_a7746676
          Community Expert
          barbara_a7746676Community Expert
          Community Expert
          July 5, 2016

          Dot gain is intended for printing and gamma is intended for files that will be viewed on a monitor.

          Which dot gain percentage is best depends the quality of paper your file will be printed on. For example, an uncoated paper stock requires more dot gain compensation than a coated paper stock. Most people speak about a 20% dot gain because that is the default. That doesn't mean it is best for your project.

          It is always a good idea to communicate with your print vendor and ask them what they recommend.

            M
            myDaveyAuthor
            Inspiring
            July 6, 2016

            @Barabara, thanks for that clarification - that makes me more comfortable using 30%

            as for speaking with the printer, I spoke with them and they said they have entirely different profiles (they are not in USA), so that didn't really help. However, after matching up with what they have done, it is true that 30% was closest!

            Thanks,

            David

              rob day
              Community Expert
              rob dayCommunity Expert
              Community Expert
              July 7, 2016

              I spoke with them and they said they have entirely different profiles (they are not in USA),

              I'm not trying to talk you out of 30%, but normally you would use the printer's profile—that's the point of profiles they profile the printer's press conditions.

              One thing you have to be careful about is InDesign has no support for gray profiles. Embedded profiles in placed grayscales are ignored and the document's CMYK Black ink profile is used for the preview of grayscales. While you can force a conversion to grayscale on PDF export, the exported gray objects have no profile assigned. Exporting to 20% Dot Gain and 30% Dot Gain will produce the same preview if the PDFs are viewed via their respective destination profiles. The difference is 20% will export with higher output values than 30%.

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