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matching blacks of photo & document

Jul 1, 2013 10:27 AM

I'm going to send a postcard to an online printing service. My design includes a photo with black background against the black card. The photo will require changing from high-res RGB to CMYK.

 

How do I make sure there's no difference between the photo and document in the blacks? I don't want a slightly lighter, darker, or tinted area.

 
Replies
  • Currently Being Moderated
    Jul 1, 2013 10:48 AM   in reply to powerdogvt

    The odds of a perfect match between a solid vector background created in ID and the continuous-tone raster background in a photo are slim to none unless the background was artificially added in photoshop. Honestly, your best options are to either extend the canvas in Photoshop and clone in some more background (which can be a challenge if you want it to look natural), or to change the design so the difference looks intentional. I sometimes add a paper-colored stroke to an image frame to get a clean break from a solid background which is very effective in masking the change in color.

     
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  • Rob Day
    3,123 posts
    Oct 16, 2007
    Currently Being Moderated
    Jul 1, 2013 2:13 PM   in reply to powerdogvt

    I'm going to send a postcard to an online printing service. My design includes a photo with black background against the black card. The photo will require changing from high-res RGB to CMYK.

     

    If the PS background is uniform spec your InDesign black as an RGB color with the same values as your PS background. Make sure the assigned RGB profiles match (select the image and make sure the RGB profile is document RGB via Object>Image Color Settings).

     

    If you export to PDF and set the Output Destination color to any CMYK profile the blacks will match in Acrobat.

     
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  • Currently Being Moderated
    Jul 1, 2013 3:17 PM   in reply to Rob Day

    Rob Day wrote:

     

    If the PS background is uniform

    If it's a photo it will almost certainly have variation from area to area due to lighting differences and this will become glaringly obvious once the image is placed on top of a truly uniform background (which is why I mentioned the "unless the background was artificially added" part in my response).

     

    You also have to watch out for older dual-layer RIPs that process vectors and raster differently at output that can cause color shifts even when the color specification is supposed to be the same. See InDesignSecrets » Blog Archive » Eliminating YDB (Yucky Discolored Box) Syndrome and it isn't limited to files with shadows or other transparency.

     
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  • Rob Day
    3,123 posts
    Oct 16, 2007
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    Jul 2, 2013 6:31 AM   in reply to Peter Spier

    RIPs that process vectors and raster differently at output that can cause color shifts even when the color specification is supposed to be the same...and it isn't limited to files with shadows or other transparency.

     

    I've seen that on composite printers, but never printing separations to an offset press. Obviously that doesn't mean it couldn't happen, but if it can it means the Separation and Output Preview panels are useless.

     
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  • Currently Being Moderated
    Jul 2, 2013 6:46 AM   in reply to Rob Day

    I certainly haven't seen it recently, but there's plenty of old equipment out there. And we don't know for sure that this is going to press and not a composite printer like an HP Indigo or Xerox iGen.

     

    Matching a photo to a background is just so fraught with problems, in my opinion, that it's seldom worth the effort. Either find a way to bleed the photo, or design so that differences are enhanced rather than looking like a mistake.

     
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  • Currently Being Moderated
    Jul 2, 2013 6:55 AM   in reply to powerdogvt

    Photos are already a four-color mix (rich black) in the background. You don't need to do a thing.

     
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  • Rob Day
    3,123 posts
    Oct 16, 2007
    Currently Being Moderated
    Jul 2, 2013 7:14 AM   in reply to powerdogvt

    But how would a photo's background be adjusted to Rich Black in Photoshop or InDesign?

     

    If you leave the photo as RGB and the black background  will become a 4-color black when it's converted to CMYK—the CMYK profile will convert the 0|0|0 to the richest black allowed by the profile's total ink limit. So for the US SWOP default it would be something like 75|68|67|90.

     

    If you want a specific mix you would have to make the conversion in Photshop and edit the background fill to your rich black mix.

     
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