Beyond CMYK


You're not limited to just cyan, magenta, yellow, and black inks when you print a color image. You can create images that consist of combinations of CMYK and spot color, or even images that print only in spot colors.

Creating Duotones

A duotone image is composed of two colors, usually black and a spot color. Such images are a great way to add visual interest to a job with a limited color palette. There are variations on this theme, such as tritones (three colors), quadtones (four colors), and so on. Since these images usually contain spot-color components, it's important to create them correctly to ensure that they print as intended. Note that these images may be composed of all spot colors or a combination of spot colors and process colors. Start with a grayscale image, and then choose Image > Mode > Duotone (which is the starting point, even if you intend to create a tritone or quadtone image).

In creating a basic spot-plus-black duotone image, designers may make the understandable mistake of thinking that the Black ink listed in the Duotone Options dialog is a spot color (Figure 9.19). Don't worry: It's really just the plain, old-fashioned process black of CMYK fame, and there's no need to change it.

Figure 9.19. The Black ink chosen by Photoshop in the Duotone Options dialog is plain old process black. Don't alter it.


In fact, if you get ambitious and change the name of Black in the Duotone Options dialog to, say, Pantone Process Black C, for example, you actually cause what you're trying to prevent: You create an extraneous spot color when you import the image into a page layout, as shown in the QuarkXPress Colors palette (Figure 9.20). So just leave it alone, and Photoshop will do the right thing.

Figure 9.20. Changing the definition of Black in Photoshop's Duotone Options creates an extra black ink when you place the image in a page layout program such as QuarkXPress (right). Not what you had in mind.


Adding Spot Color to a CMYK Image

Occasionally, special handling is needed to accentuate portions of an image or to ensure faithful rendering of a color that falls outside the CMYK gamut. Adding spot ink on top of an image of flowers might allow the printed piece to better render the true color of the actual flowers, if process color falls short of doing so. In this approachvariously called bump plate, touch plate, or kiss platethe image contains additional colors beyond the standard cyan, magenta, yellow, and black.

The trick is to contain the extra color plates in an image format that's well digested by page-layout software. The most common format for this amalgam of colors is a special flavor of EPS called DCS 2.0, for Desktop Color Separations. Under the hood, these special images consist of all the individual color plates plus a low-resolution representation image for display. Both QuarkXPress and InDesign can handle DCS 2.0 files created by Photoshop, although there are some catches. QuarkXPress does not correctly generate a composite PDF of the DCS 2.0 content. Instead, QuarkXPress produces a PDF containing just the low-resolution component of the DCS file. Because of this issue, QuarkXPress documents containing DCS 2.0 files must be given special handling by the print service provider. InDesign handles DCS 2.0 content more intelligently and produces a correct PDF containing all the high-resolution data for all plates. But neither InDesign nor QuarkXPress correctly image DCS 2.0 files containing vector elements or text. You must add text in the page layout or in an illustration program, then place it on top of the DCS 2.0 file.

The DCS 2.0 format is getting a bit outdated, largely because of the special handling it requires. If you are creating specialized images containing spot color content, consider saving them as Photoshop PDF rather than DCS 2.0. Both QuarkXPress and InDesign accept Photoshop PDFs. Using Photoshop PDF rather than DCS 2.0 also ensures that PDFs exported from QuarkXPress will contain high-resolution content and spot colors.




Real World(c) Print Production
Real World Print Production
ISBN: 0321410181
EAN: 2147483647
Year: 2007
Pages: 132
Authors: Claudia McCue

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