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ID to PDF color conversion problem

Nov 29, 2012 8:01 AM

Tags: #color #cmyk #pdf #conversion

I'm creating a PDF file for printing a color book. Typically, I use  PDF/X-1A:2001, which is recommended by the printer and which always gives me good color. This time, however, certain bright blues are coming out very gray. All the other colors look good. Does anyone have any suggestions for fixing the problem? I know almost nothing about color conversion as does the designer I'm working with. Thanks for any and all help.

 
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  • Currently Being Moderated
    Nov 29, 2012 8:09 AM   in reply to PH_Red

    PH_Red wrote:

     

    certain bright blues are coming out very gray. All the other colors look good

    Were these colors defined as CMYK, or are they RGB or Spot colors. Bright blue could be out of gamut for the CMYK space you are using.

     
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  • Rob Day
    3,118 posts
    Oct 16, 2007
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    Nov 29, 2012 11:04 AM   in reply to PH_Red

    PDF/X-1a forces all color into the destination CMYK space—usually your document's CMYK profile. The blues in the scan are out-of-gamut. Blues can be problematic for both converting and soft proofing because a good part of the blue spectrum is out of the CMYK gamut and cyan is out of the RGB gamut.

     
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  • Rob Day
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    Oct 16, 2007
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    Nov 29, 2012 11:46 AM   in reply to PH_Red

    Obviously there are plenty of books printed where color has to be exact.

     

    Depends on how far out-of-gamut the color is RGB 0|0|255 can't be printed under any circumstances.

     

    If you know what you're doing it can help to color-correct and make the conversion in Photoshop, but you can't avoid the gamut.  Selective Color can be used to manipulate Blue and Cyan after the conversion—you can look at the output numbers in the Info panel and make sure cyan is near 100% with a minimum of yellow and black.

     

    If the blues lean to cyan they will likely print brighter because cyan can't be displayed accurately.

     
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  • Rob Day
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    Oct 16, 2007
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    Nov 29, 2012 2:47 PM   in reply to PH_Red

    I'm getting slightly better results, but essentially more of a torquoise than a royal blue, which is what I need.

     

    Right you'll have to compromise either with the hue or value

     
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  • Currently Being Moderated
    Nov 29, 2012 2:51 PM   in reply to Rob Day

    or possibly add a spot blue channel.

     
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  • Rob Day
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    Nov 29, 2012 3:01 PM   in reply to Peter Spier

    It's pretty far out. I don't see anything in the Pantone book that's close.

     
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  • Currently Being Moderated
    Nov 29, 2012 3:15 PM   in reply to Rob Day

    I dunno. In my office, 2935c and 300c look like they might be acceptable compromises, or posibly 293c (but it's a bit dark). A skilled ink mixer might be able to come closer.

     
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  • Rob Day
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    Oct 16, 2007
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    Nov 29, 2012 3:33 PM   in reply to Peter Spier

    Are we looking at the same RGB? Here's sRGB 78|116|238 with Pantone 300, which is barely out-of-gamut:

     

    Screen shot 2012-11-29 at 6.27.47 PM.png

     
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  • Currently Being Moderated
    Nov 29, 2012 3:44 PM   in reply to Rob Day

    I'm looking at the swatch book, not the screen renderings, to judge the spots.

     

    I haven't calibrated the monitor in a few weeks, so it may be off, and you screen cap looks a tad more magenta, I think than my color in photoshop, but that could be the forum. Here's a grab from my screen:

     

    RGB Royal Blue.png

     

    And as you pointed out, pretty much anything other than a custom mixed spot is going to be some sort of compromise.

     
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  • Currently Being Moderated
    Nov 29, 2012 3:46 PM   in reply to Peter Spier

    OK, sorry, I see the problem. I've got the wrong color. 285 might be acceptable.

     
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  • Currently Being Moderated
    Nov 29, 2012 4:27 PM   in reply to PH_Red

    I'm afraid the bad news is that you're just not going to be able to reproduce the blues accurately at Lightning Source.

     
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