Look in the Swatches panels of InDesign and Illustrator, and the Colors list in QuarkXPress, and you’ll see a mystery color named “Registration.” It’s intended for page information, registration marks, and trim marks. When we used to output film and strip it up on light tables, we used registration marks to ensure that all the inks printed in alignment. Registration is intended for use only by the application, not the user, except in rare cases.
It was another one of those thoroughly snakebit jobs that go wrong at every step, but at its core is a mystery concerning how QuarkXPress treats an overprinting grayscale image in an exported PDF. “Regular” overprinting objects, such as text or boxes, display and print predictably. But grayscale images are handled differently, and this results in a misleading display in Acrobat, which leads to a surprise on press. And, as you know, “surprise” is not a good word in printing.
Here’s the timeline: Continue reading