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Chapter 23. Print > Color separation tips

Color separation tips

  • Don't choose colors based on how they appear on screen, because a computer screen can only simulate printed colors. Always use a matching system booklet to choose colors.

    What's on your plate?

    In standard four-color process printing, a document is color separated onto four plates, one each for Cyan, Yellow, Magenta, and Black. The many other potential combinations include printing a spot color and black on two separate plates or printing a spot color and the four process colors, bringing the total to five plates.

    Hexachrome (high fidelity) colors color separate onto six process color plates, with the result being greater color fidelity due to the wider range of printable colors. An RGB picture can be color-separated using this method.

  • To apply a spot color tint—whether as a background color in an item or as type color—choose a shade percentage from the Colors palette or choose a TRUMATCH or FOCOLTONE color that has the desired value in Edit > Colors (Shift-F12).

  • If your document contains bitmapped pictures, ask your service bureau or commercial printer in which file format (TIFF, EPS, etc.) and image mode (CMYK, RGB, etc.) those pictures should be saved. You can use Photoshop to easily change a picture's file format, resolution, or image mode.

    Printing a spot

    Be sure to check Spot Color in the Edit Color dialog box for any spot color that you want to color-separate onto a separate plate. To output a particular color, choose File > Print, check Separations (Document pane), then, in the Output pane, choose Used Process & Spot from the Plates pop-up menu and Conventional from the Halftoning pop-up menu.

    Spot colors, if they are saved in an Illustrator or FreeHand file in the EPS format, will append to the Colors dialog box in the QuarkXPress document and will also display in the plate scroll window in File > Print (Output pane). Make sure the name that is assigned to any spot color that is used in both QuarkXPress and Illustrator is exactly the same in each program, otherwise two plates will print instead of the desired one.

  • Ask your output service whether to use Photoshop or QuarkXPress to convert any color pictures from RGB to CMYK for separations. A picture scanned into CMYK color mode doesn't need to be converted.

  • Any RGB spot colors from an imported Illustrator EPS file will remain as RGB spot colors (as listed in the Colors dialog box).

  • If your document contains hand-drawn registration or crop marks, apply the Registration color to them to ensure that they appear on all the separation plates.

  • For color work, order a color proof (IRIS or a 3M Rainbow) of the document so you can inspect it for color accuracy.

Trapping mini-glossary


The foreground object color prints on top of the background color, so inks actually mix together. Overprint is used if black is the foreground object color or if inks are intentionally mixed to produce a third (overlap) color.


To prevent inks from overprinting, the foreground object color shape is cut out (knocked out) of the underlying background color area on the background color plate. While this eliminates the problem of ink mixing, it creates a potential problem of a gap between the edges of the foreground and background colors. Trapping closes this gap.


The spread method of trapping is used when colors knock out and the foreground color is lighter than the background color. The edge of the foreground color object is enlarged slightly to make the foreground color spread into the background color on press .

Figure 1. In a spread trap, the foreground object color spreads into the background object color.


The choke method of trapping is employed when the foreground color is darker than the background color. The edge of the foreground color object shrinks slightly as a result of overprinting. This causes the background color to spread into (choke) the foreground color on press.



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