: Spot Color Transparency and Screens in Illustrator (Illustrator CS5) I have a design that will be printed on a line printer. Possible are up to 7 colors, or a 4-color process with 3 line colors.

@Tiffany317

The printer's RIP will understand it. To get a real feel for how things will process, turn on Overprint Preview. That's how it will print. If you have objects set to overprint that should knock out, or vice versa, you'll see the difference quite clearly.

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@Si6392903

To achieve "transparency" effect Illustrator simply mixes color of given object with color of its background. For example: objects fill is set to Pantone 451. Object have opacity set to 50% and tint to 100%. It has white background. If mixing mode is "Normal" resulting color will be 50% of given Pantone. Exact recipe how resulting color is calculated is described as a math formula. Different formulas are known by specific names as "mixing modes".

Take a look at "Separation preview" in your Ill to see actual values of separate component colors on output.

When all your objects have "white artboard" as their background it doesn't make any difference if their color is made lighter with transparency setting or with tint control. It does however make a difference if their background isn't white. Similar things happen when "overprint" (most unfortunate name) is on.

Printer, in fact, won't understand transparency at all. If something will, it'll be RIP, but it'll also "simulate" transparency by telling printer to use in specific ares e.g. lighter colors. Exactly what Ill does before "sending" image to monitor.

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