Overprinting produces a color mixture where the orange circle overlaps the gray circle. This effect isn’t visible on screen. Without overprinting, the orange circle knocks out part of the gray circle.
In color separations designed for commercial printing, a front object usually knocks out a hole where it overlaps other objects; however, you can apply the Overprint Object option to an object to prevent it from creating knockouts in objects behind it. This can compensate for registration problems on some printing presses.
For example, if you draw a cyan circle on a yellow background, Canvas X Draw knocks the circle out of the background in color separations so cyan and yellow don’t mix in the circle. If you select the circle and use the Overprint Object option, the circle prints over a solid yellow background, and the cyan in the circle mixes with the background yellow, resulting in a green circle.
The effect of the Overprint Object option is not visible on screen. This effect is visible only in the printed output when you produce color separations. Verify the settings for a particular object by viewing the Trap tab in the Object Specs palette and then selecting the object.
Color mixing as described previously is not the primary reason for overprinting. It’s more common for designers to overprint dark objects on lighter backgrounds as a way to prevent a gap from appearing between the colors if the press registration (alignment) isn’t perfect.
Select the objects and deselect the Overprint Object checkbox. Then click Apply.
When objects of different colors touch, there is the potential for an unsightly gap to appear between the colors if the piece isn’t printed precisely aligned, or in register.
Choke trapping reduces the background knockout slightly to trap into a dark foreground object.
Spread trapping enlarges the stroke of a foreground object slightly to trap into a dark background object.
Trapping is a technique that purposely distorts the shapes of objects in color separations where different colors meet. The slight distortion creates tiny areas called traps where colors overlap. The trap areas can help avoid the appearance of gaps if the page is printed slightly out of register.
Before you use trapping in color separations, determine how likely it is that the piece will not be printed in register. Consider how beneficial it will be to distort the shape of some objects to compensate for possible misregistration; e.g., trapping type can ruin the appearance of the text, and probably isn’t necessary.
Whenever possible, design illustrations to avoid certain trapping problems, and always discuss trapping with your service bureau and printer to avoid unnecessary expense and inferior results.
In Canvas X Draw, trapping is best applied to vector objects that use a solid pen stroke and solid pen ink color. The following limitations apply to trapping:
Before printing color separations, specify the trap size. Select the Separations options in the Print dialog box to change the trap size value.