11 Replies Latest reply: Aug 10, 2012 11:44 AM by rob day RSS

    Problem generating PDFs from ID

    PH_Red Community Member

      I generate PDFs for digital book printing. I get excellent results with color using the standard PDF/X-1a: 2001 setting. However, my grayscale images are always washed out, losing all the contract I carefully dialed in  in Photoshop. The only way I've found to maintain the image quality is to turn off all compression. However, this produces huge files, which are difficult to upload to the printers I use.

       

      The images are usually TIFFS and have all been resized to 300 dpi before being linked to the ID file.

       

      Am I missing something?

       

      Thanks for any suggestions.

       

      Fred

        • 1. Re: Problem generating PDFs from ID
          rob day MVP

          ID doesn't have a grayscale space the way Photoshop does so by default the 2 programs preview grayscale objects differently. In ID when Overprint or Separation Preview is turned on the grayscale is previewed through the document's CMYK profile. By default Photoshop uses the 20% dot gain curve gray profile

           

          Lots of threads on this see this one:

           

          http://forums.adobe.com/message/3484956#3484956#3484956

           

          Also check to see if your digital printer is printing the PDF's CMYK and gray values unchanged. Many online printers force additional CMYK conversions even when you send X-1a files

          • 2. Re: Problem generating PDFs from ID
            Fede Gianni Community Member

            i would try:

             

            - check the consisteny of Color settings in all the suite and the specific working spaces of grayscale images

            - save in PSD instead of TIFF

             

            where you apply the compression?

            • 3. Re: Problem generating PDFs from ID
              rob day MVP

              check the consisteny of Color settings in all the suite and the specific working spaces of grayscale images

               

              You can't match ID and Photoshop Color Settings for grayscale images. ID has no grayscale color space and  ignores any grayscale profile embedded in a grayscale image. Grayscale values output or export to the black channel unchanged as long as there's no transparency or the Transparency Blend Space is CMYK.

              • 4. Re: Problem generating PDFs from ID
                Fede Gianni Community Member

                You can't match ID and Photoshop Color Settings for grayscale images.

                d'oh!, youre right!

                 

                then the solution is?

                 

                saving the grayscale as cmyk?

                 

                Pit Stop? (i used it to change almost anything in a PDF)

                 

                what about this: go to photoshop, check the "proof color option" in the "proof setup/custom" look at the grayscale spaces (the ones starting with dot gain and gray gamma) with preserve numbers and preview checked, then change colorspaces until you see the same "washed" effect, and do the corrections with the proof color checked.

                • 5. Re: Problem generating PDFs from ID
                  PH_Red Community Member

                  Let me point out that I am NOT a designer or production person. But i'm usuall the last one to check the files and do the conversion. (BTW, our designer doesn't know anything about this either, although she's very talented as a designer.)

                   

                  Any photos that are over 300 ppi I downsample in PS as the last part of my workflow. Since the PDF dialog box is essentially set to only downsample anything over 300, I don't  understand why the images would look any different after the PDF is generated. As I said ealier, when all compression is turned off, they look fine in the PDF. So????

                  • 6. Re: Problem generating PDFs from ID
                    rob day MVP

                    As I said ealier, when all compression is turned off, they look fine in the PDF. So????

                     

                    I can't replicate what you are describing can you post screen caps showing the differences, or the PDFs

                    • 7. Re: Problem generating PDFs from ID
                      PH_Red Community Member

                      As I said, I'm not designer, so I'm fiddling  in the dark a bit. Anyway, I just changed the color conversion destination to sRGB, without changing anything else, and that seeme to do the trick. The main printer we use (who also does a lot of work for Blurb and Lulu), wants the files in sRGB, so that's what gave me the idea. I've got a reasonably sized file, with the grayscale I want.

                       

                      I should poiint out, with regard to the postings here, that it was never an issue of not getting the results from the press after seeing what I wanted onscreen. If the screen looks good, we get good output results at the printer.

                      • 8. Re: Problem generating PDFs from ID
                        Fede Gianni Community Member

                        im glad to read that

                        • 9. Re: Problem generating PDFs from ID
                          rob day MVP

                          The main printer we use (who also does a lot of work for Blurb and Lulu), wants the files in sRGB, so that's what gave me the idea. I've got a reasonably sized file, with the grayscale I want.

                           

                          Just keep in mind that your grayscales and black/gray objects are now RGB will print as 4-color CMYK mixes. There's the potential problem of color casts in the grayscale-to-RGB images, and the real problem of small black 4-color text going off regisister.

                           

                          They may be capable of maintaining neutral values when the RGB grayscale images are separated, but you would be better off converting the grayscales to sRGB in Photoshop and exporting to PDF/X-4 (not X-1a). In that case your black text will be black only.

                          • 10. Re: Problem generating PDFs from ID
                            PH_Red Community Member

                            Rob, that's interesting you point that out, because I noticed a color cast to one of our grayscale books, but didn't know where it was coming from. (We have our b/w books printed on an HP color digital press for more range in the grayscale photos.)

                             

                            So you're saying to convert color images to grayscale and then back again to RGB in Photoshop? And how does PDF/X-4 differ from X-1a with regard to blacks??

                            • 11. Re: Problem generating PDFs from ID
                              rob day MVP

                              So you're saying to convert color images to grayscale and then back again to RGB in Photoshop?

                               

                              No. Your idea of setting the PDF export destination color to sRGB means that every object (CMYK, grayscale, or RGB) in the layout will get converted to sRGB on export. At the printer your sRGB PDF will get converted back to CMYK on output—there are no RGB printers. If you really want to convert grayscales to sRGB do it in Photoshop, but they will get converted to 4-color CMYK on output and may or may not have a cast.

                               

                              If neutrality is a must then you have to deliver grayscale, not RGB, and the printer has to output your values. If you place grayscales and export to PDF/X-a the PDF will be all CMYK and the grayscales will be on the black plate—the numbers will be unchanged from Photoshop. The preview might change in Acrobat or ID but the output numbers won't.

                               

                              It maybe that your printer will not output your PDF's CMYK values unchanged. If you look at the printed grayscales under a loupe the halftone dots will be all black if your PDF values are being printed unchanged.

                               

                              PDF/X-1a forces all color to CMYK or spot color, flattens transparency, and does not include color profiles—the assumption being the values need to output unchanged.

                               

                              PDF/X-4 doesn't allow any conversions and all objects have a color profile—the assumption is all RGB object will get converted to CMYK at output via the printer's profile. So with PDF/x-4 any sRGB objects would get converted on output and any black only text would output unchanged.