Expert: Amy - 3/18/2004

Question
Hows it going?

I work in the art department of a flag company doing color separations on Adobe Illustrator 9 for pc. To trap, we normally inline objects and use those shapes to cut that specific section out of the lighter color under it. I notice illustrator has a trap function but can't get it to work for the life of me. Can you help?

Thanks,
-Chris Musto
http://www.nymbus7.com

Answer
Hi Chris,

It's going all right.

First off, you have to be working in a CMYK color mode (File > Document Color Mode - CMYK).

Then you should be in Overprint Preview mode (View > Overprint Preview) to properly view the results.

Draw two colored overlapping objects for your test. I'm using a light circle in a dark square for my little test while writing this. Note: Don't use Rich Black for a color, as automatic trapping doesn't work when you do. I'm sure you know this, but rich black is 100%K + any other amount of CM or Y.

Trap is controlled in the Pathfinder Window, which is accessed by choosing Show Pathfinder from the Window menu (or Shift + F9). Then you have to display the options by using the flyout menu arrow on the window's top right corner. Trap is the very last button on the bottom.

Choose your two objects to be trapped and click that last button.

In the trap dialog window, choose the thickness of your trap area and the H&W offset (these two things will be determined by the calibration of your press or other output device).

"Tint reduction"  100% will put 100% of the light color down in the spread/choke area. 50% will put 50% down, etc. I guess this will depend on your colors and press results.

"Traps with Process" will make the spread/choke area a process color versus a spot color if you are working with spot colors. To avoid creating a process color in a spot color piece, do not check this option.

"Reverse Traps" puts the darker color down instead of the lighter color. This is usually not preferred, because of the way the human eye views things, if I remember graphic design 101 correctly. If you have a light circle in a dark square, you usually you want your lighter color to spread into your darker area.  The default AI trap command will do it this way. If you have a dark circle in a light square, you want the light color of the square to choke the dark circle. Again, the default AI trap will do it this way.

And that is how you trap!

Anything else, just ask,
Amy Pace