"Black & Text" tab

"Width Scaling" parameter

This parameter lets you set a different trap width for "black" than for other colors. If you set a value greater than 100%, you can make sure that in the case of a rich or fat black the colors lying below are not visible as margins along the trap lines.

How this works: The black trap lines are created wider than the traps of other colors if you set values greater than 100 %. Values less than 100 % accordingly create narrower trap lines.

"Color Limit" parameter

This setting defines the value for black above which the trapping engine treats a dark color as black and as a result the special rules for black are applied.

How this works: The smaller the value entered, the more likely a dark color will be treated as black.

"Density Limit" parameter

This setting defines a threshold for neutral density (ND) above which the trap engine considers a spot color to be as dark as black.

The special rules for black are applied to a dark spot color only if the value set for "Color Limit" is reached. The spot color is treated as black if the value set is less than or equal to the neutral density of a spot color in the edited document.

Definition of the Neutral Density:

"Neutral density" is the degree to which a color is found in common in each separation of two adjacent colors:

Each process color (CMYK) has a different ink strength. "Neutral Density" was defined to determine the ink strength of a process color, with paper white having a neutral density of 0.

Example of the neutral density for process colors:

The following formula can be used to calculate the neutral density (ND) in values less than 100%:

ND = –1.7 · log(1 – Color(1 – 10^{(–0.6 · D)}))

The neutral density of all separations is obtained from the sum of the neutral densities of the single separations.