Spot Color

In offset printing, a spot color is any color generated by an ink (pure or mixed) that is printed using a single run. Spot colors are special pre-mixed inks used instead of, or in addition to, the process color (CMYK) inks. Each spot color requires its own plate on the press. If you are planning to print an image with spot colors, you need to create spot channels to store the colors. More advanced processes involve the use of six spot colors (hexachromatic process), which add Orange and Green to the process (termed CMYKOG). The two additional spot colors are added to compensate for the inefficient reproduction of faint tints using CMYK colors only. Spot color printing is effective when the printed matter contains only one to three different colors, but it becomes prohibitively expensive for more colors. However, offset technicians around the world use the term spot color to mean any color generated by a non-standard offset ink; such as metallic, fluorescent, spot varnish, or custom hand-mixed inks.
Most desktop publishing and graphics applications allow you to specify spot colors for text and other elements. There are a number of color specification systems for specifying spot colors.
Creating Spot channel in Adobe Photoshop
You can create a new spot channel or convert an existing alpha channel to a spot channel
First choose Window > Channels to display the Channels palette. Do one of the following
create a channel:
• Ctrl-click (Windows) or Command-click (Mac OS) the New Channel button in the Channels palette or click the pop-out menu in the Channels palette.
• Choose New Spot Channel from the Channels palette menu.
New Spot Color in Adobe Illustrator
• Ctrl-click (Windows) or Option-click (Mac OS) the New Swatch button in the Swatches palette.
• Ctrl-drag (Windows) or Command-drag (Mac OS) the color from the toolbox or Color palette to the Swatches palette. Or, if you selected an object, Ctrl-drag (Windows) or Command-drag (Mac OS) the object to the Swatches palette.
• Select New Swatch from the Swatches palette menu. Select Spot Color for Color Type. Set additional swatch options if needed and click OK.
You can find some predefined spot colors, such as colors from the TOYO, PANTONE, DIC, and HKS in the "libraries".
are defined using Lab values.
Soft Proofing of Spot Colors
Remember that spot colors (gold, silver, fluoresent) can't be reproduced on a monitor exactly because they exist outside the gamut or color range of monitor and other proofing devices.

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