Understanding spot and process colors

You can designate colors as either spot or process color types, which correspond to the two main ink types used in commercial printing. In the Swatches panel, you can identify the color type of a color using icons that appear next to the name of the color.

When applying color to paths and frames, keep in mind the final medium in which the artwork will be published, so that you apply color using the most appropriate color mode.

If your color workflow involves transferring documents among devices, you may want to use a color-management system (CMS) to help maintain and regulate colors throughout the process.

A spot color is a special premixed ink that is used instead of, or in addition to, process inks, and that requires its own printing plate on a printing press. Use spot color when few colors are specified and color accuracy is critical. Spot color inks can accurately reproduce colors that are outside the gamut of process colors. However, the exact appearance of the printed spot color is determined by the combination of the ink as mixed by the commercial printer and the paper it’s printed on, not by color values you specify or by color management. When you specify spot color values, you’re describing the simulated appearance of the color for your monitor and composite printer only (subject to the gamut limitations of those devices).

Keep the following guidelines in mind when specifying a spot color:

• For best results in printed documents, specify a spot color from a color-matching system supported by your commercial printer. Several color-matching system libraries are included with the software.

• Minimize the number of spot colors you use. Each spot color you create will generate an additional spot color printing plate for a printing press, increasing your printing costs. If you think you might require more than four colors, consider printing your document using process colors.

• If an object contains spot colors and overlaps another object containing transparency, undesirable results may occur when exporting to EPS format, when converting spot colors to process colors using the Print dialog box, or when creating color separations in an application other than Illustrator or InDesign. For best results, use the Flattener Preview or the Separations Preview to soft proof the effects of flattening transparency before printing. In addition, you can convert the spot colors to process colors by using the Ink Manager in InDesign before printing or exporting.

• You can use a spot color printing plate to apply a varnish over areas of a process color job. In this case, your print job would use a total of five inks—four process inks and one spot varnish.

A process color is printed using a combination of the four standard process inks: cyan, magenta, yellow, and black (CMYK). Use process colors when a job requires so many colors that using individual spot inks would be expensive or impractical, as when printing color photographs.

Keep the following guidelines in mind when specifying a process color:

• For best results in a high-quality printed document, specify process colors using CMYK values printed in process color reference charts, such as those available from a commercial printer.

• The final color values of a process color are its values in CMYK, so if you specify a process color using RGB (or LAB, in InDesign), those color values will be converted to CMYK when you print color separations. These conversions differ based on your color-management settings and document profile.

• Don’t specify a process color based on how it looks on your monitor, unless you are sure you have set up a color-management system properly, and you understand its limitations for previewing color.

• Avoid using process colors in documents intended for online viewing only, because CMYK has a smaller color gamut than that of a typical monitor.

• Illustrator and InDesign let you specify a process color as either global or non-global. In Illustrator, global process colors remain linked to a swatch in the Swatches panel, so that if you modify the swatch of a global process color, all objects using that color are updated. Non-global process colors do not automatically update throughout the document when the color is edited. Process colors are non-global by default. In InDesign, when you apply a swatch to objects, the swatch is automatically applied as a global process color. Non-global swatches are unnamed colors, which you can edit in the Color panel.

Sometimes it’s practical to use process and spot inks in the same job. For example, you might use one spot ink to print the exact color of a company logo on the same pages of an annual report where photographs are reproduced using process color. You can also use a spot color printing plate to apply a varnish over areas of a process color job. In both cases, your print job would use a total of five inks—four process inks and one spot ink or varnish.

In InDesign, you can mix process and spot colors together to create mixed ink colors.

Adobe InDesign and Adobe Illustrator use slightly different methods for applying named colors. Illustrator lets you specify a named color as either global or nonglobal, and InDesign treats all unnamed colors as nonglobal, process colors.

The InDesign equivalents to global colors are swatches. Swatches make it easier to modify color schemes without having to locate and adjust each individual object. This is especially useful in standardized, production-driven documents like magazines. Because InDesign colors are linked to swatches in the Swatches panel, any change to a swatch affects all objects to which a color is applied.

The InDesign equivalents to nonglobal swatches are unnamed colors. Unnamed colors do not appear in the Swatches panel, and they do not automatically update throughout the document when the color is edited in the Color panel. You can, however, add an unnamed color to the Swatches panel later.

Named and unnamed colors only affect how a particular color updates in your document, never how colors separate or behave when you move them between applications.