Adobe illustrator 10 Manuale Utente

A spot color is a special premixed ink that is used instead of, or in addition to, CMYK 
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 combination of the ink as mixed by 
the commercial printer and the paper it’s printed on, so it isn’t affected 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).

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 Illustrator; see 

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.

A process color is printed using a combination of 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, such as when 
printing color photographs. Keep the following guidelines in mind when specifying a 
process color:

For best results in a 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, those color values will be converted to CMYK when you print color 
separations. These conversions will work differently if you turn on color management; 
they’ll be affected by the profiles you’ve specified.

Don’t specify a process color based on how it looks on your monitor unless 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 a typical monitor.

Sometimes it’s practical to print process and spot inks on 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.