InQuestion: Color Matching for Digital Press Jobs
This article appeared in Issue 76 of InDesign Magazine.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?
Figure 1: A color used to fill areas in Photoshop and InDesign content appears the same onscreen in InDesign (left). But it may look quite different when output to digital presses (right).
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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I’ve never had this happen to me. Is it an issue with the printer’s set up?
How do we know if this will happen to our artwork BEFORE it gets printed?
It’s usually due to mismatched color systems, especially where transparency is involved, such as the drop-shadow mentioned in the example.
Generally working objects in the same color system (RGB vs. CMYK) and setting your document transparency blending space accordingly will keep you from seeing this happen.
Also, watch that your swatches are matching (RBG vs. CMYK and Spot vs. Process).
Exporting to a quality image for print will resolve problems and usually to a pdf will as well if you us a pdf4 v1.3 so it’s flattened.
I agree Paul, this usually happens if you are not working with consistent color systems and wrong exporting settings. I had to do this many times while I was working for a printing agency where the print jobs were almost always done by digital press.
Doing that, I also noticed that picking a color with the eye dropper from the image inside InDesign (not Photoshop) usually was a quick fix to solve this problem, although you still have to keep a close watch to what color system the image is using and make sure to use the right export settings.
Zooming in on the edges of the image in the resulting pdf with a good quality calibrated monitor will also often show slight differences if the colors do not match exactly. If you see even the slightest difference, you have to solve the problem because the difference will usually be worse after printing.
I’ve had this problem with our corporate logos and colours.
I’m going to apply this tip first thing Monday,
Thanks!
This also depends a lot on the type of Digital Press and the proficiency of the operator.
As we have the printer (a Versafire) close by, we can check and proof everything.
What has a lot of effect is the right PDF version, we tend to have more problems with flattened documents, also overprint objects can create issues.
Consistent use of color profiles helps a lot too.
But in the end sometimes the only way is to rasterize the document.
The workaround to replace vector objects with raster images is in my opinion a bad one, not to mention inconvenient. It shouldn’t take long for an experienced user to track down and solve the actual issue.
It is a color management issue. Checking the PDF with Acrobat and inspecting the two elements in question (comparing how their colors are defined) would likely reveal if the problem was wrong color/export settings in InDesign, or bad settings on the RIP.
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Let’s go back to the first bit of the example; sampling the color in Photoshop. That is good, it will give you the exact color value. But the color value is worthless without also knowing the color profile. If you use a different RGB profile for the RGB values in InDesign, then the resulting color will be different. So make sure you use the correct color profile and you are all good (or you will need to convert the values).
(Same goes for CMYK if you for some strange reason keep your raster images as that).
Now, even if you have defined the colors correct in the document, you could have export settings that are bad. For example you can have “dangerous” settings (when color accuracy is concerned) like discarding embedded profiles, or exporting your PDF without embedding the profiles used (or setting the output intent). Make sure the profiles are honored, and embedded, and the colors will be correct in the PDF. I would recommend converting everything to the same color space when exporting the PDF; usually this would be a CMYK profile recommended by the printer.
On the rip at the printer, they might have old software or poor settings for converting things, for example they might ignore CMYK profiles, or they might not use black point compensation when converting RGB to CMYK causing RGB images to turn out bad (yes, I’m looking at you Xerox-rip at work). This is why I would recommend having the PDF converted to a single color space when exporting the print-PDF if sending it out to someone else for printing.