InQuestion: Color Matching for Digital Press Jobs
InQuestion is a regular column devoted to answering your questions about working with InDesign.
Q. My company is printing promotional brochures for an upcoming trade show. Because we only need a few hundred, they’re going on a digital press. I have an image with a dark blue background, but I need for the background to cover entire pages. I went into Photoshop and used the Eyedropper tool to sample the color, and built a swatch in InDesign with the same values, created a large rectangle, and filled it with that swatch. But in the printed piece you can still see the difference between the image and the InDesign object (Figure 1). I don’t want to have to create a ginormous image and composite the products together, because the client moves everything around so frequently. How can I make the colors match?
A. The RIPs (Raster Image Processors) that process graphics for digital presses seem to apply color management differently to raster content (images and image content generated by effects, such as drop shadows or glows) and vector content. The large flat color rectangle you’re using as a background is a vector shape. If you just needed a glow around your product shots, you could silhouette them in Photoshop, and then apply the glow in InDesign. But you have noise in the gradient background, and there’s really no way to do that in InDesign—you can add noise to the transition area of a gradient, but not inside an object.
For consistency across your page on a digital press, you will need to have all-image content. But don’t panic—this doesn’t mean you have to composite in Photoshop! Here’s the fix: in Photoshop, create a small new image (one inch square is sufficient), and fill it with the correct swatch. In InDesign, change the fill of your background rectangle to None, and then place the small swatch image in that frame. Choose Object > Fitting > Fit Content to Frame. Don’t worry—the swatch image has no detail and no grain, so it doesn’t matter how much you scale it. And because it’s so small, it doesn’t add much to the size of your InDesign file or an exported PDF.
Now, the content of your page is all made of the same material, and will provide consistent print output on the digital press. By the way, this issue is particular to digital presses; the RIPs for offset platemakers treat raster and vector content the same. And no, I don’t know why!
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