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PH_Red
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Problem generating PDFs from ID

Aug 9, 2012 11:23 AM

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

 
Replies
  • Rob Day
    3,120 posts
    Oct 16, 2007
    Currently Being Moderated
    Aug 9, 2012 11:41 AM   in reply to PH_Red

    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

     
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  • Currently Being Moderated
    Aug 9, 2012 11:45 AM   in reply to PH_Red

    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?

     
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  • Rob Day
    3,120 posts
    Oct 16, 2007
    Currently Being Moderated
    Aug 9, 2012 11:59 AM   in reply to Fede Gianni

    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.

     
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  • Currently Being Moderated
    Aug 9, 2012 2:08 PM   in reply to Rob Day

    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.

     
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  • Rob Day
    3,120 posts
    Oct 16, 2007
    Currently Being Moderated
    Aug 10, 2012 7:23 AM   in reply to PH_Red

    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

     
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  • Currently Being Moderated
    Aug 10, 2012 8:16 AM   in reply to PH_Red

    im glad to read that

     
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  • Rob Day
    3,120 posts
    Oct 16, 2007
    Currently Being Moderated
    Aug 10, 2012 8:24 AM   in reply to PH_Red

    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.

     
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  • Rob Day
    3,120 posts
    Oct 16, 2007
    Currently Being Moderated
    Aug 10, 2012 11:44 AM   in reply to PH_Red

    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.

     
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