Adobe 62000112DM User Guide - Page 473

ADOBE ACROBAT 3D VERSION 8 466 User Guide Close-up of trap end examples: miter (left) and overlap (right) Trap thresholds You can adjust trap thresholds, as recommended by your prepress service provider, to correspond to your printing conditions. Step Specifies the color change threshold at which the trapping engine creates a trap. Some jobs need only the most extreme color changes trapped, while others require traps for more subtle color changes. The Step value indicates the degree to which components (such as CMYK values) of abutting colors must vary before trapping occurs. To change how much the component inks in abutting colors can vary before causing those colors to trap, increase or decrease the value for Step. The lower the Step value, the more often traps are created between colors. The default is 10%. For best results, use a value from 8% to 20%. Lower percentages increase sensitivity to color differences and result in more traps. Black Color Indicates the minimum amount of black ink required before the Black trap width setting is applied. The default value is 100%. For best results, use a value no lower than 70%. Black Density Indicates the neutral density value at or above which InDesign considers an ink to be black. For example, if you want a dark spot ink to use the Black trap width setting, enter the neutral density value here. This value is typically set near the default of 1.6. Sliding Trap Indicates the percentage difference (between the neutral densities of abutting colors) at which the trap is moved from the darker side of a color edge toward the centerline, to prevent abrupt shifts in trap placement and create a more elegant trap. During trapping, the trapping engine adjusts (slides) the trap position-from spreading the lighter color into the darker one, to straddling the centerline between them. For example, setting the Sliding Trap value to 70% moves the point at which the trap begins to straddle the centerline to the location where the lighter color exceeds 70% of the darker color in neutral density (lighter color's neutral density divided by darker color's neutral density > 0.70). Colors of identical neutral density will always have their traps exactly straddle the centerline, unless the Sliding Trap is set to 100%. Trap Color Reduction Indicates the degree to which components from abutting colors are used to reduce the trap color. This setting is useful for preventing certain abutting colors (such as pastels) from making an unsightly trap that is darker than either color. Specifying a Trap Color Reduction lower than 100% begins to lighten the color of the trap; a Trap Color Reduction value of 0% makes a trap with a neutral density equal to the neutral density of the darker color.