Adobe InDesign CS3 Bible

One of InDesign's most sophisticated tools is its set of transparency options, which let you make items partially transparent. You apply transparency with the Transparency pane (Window ‚ Transparency, or Shift+F10). Figure 25-9 shows the pane as well as a brochure that uses transparency to create a vellum effect on a stripe that contains text that overprints a background photo. The artist chose a transparency setting of 74 percent for the white frame's Opacity, as well as the Screen setting for transparency type.

Figure 25-9: The Transparency pane and its pop-up menu, as well as an example of a transparent object overprinting the photograph.

There are 16 different transparency types ‚ called blending modes ‚ as shown in Figure 25-10. The differences among them can be subtle or extreme, depending on a variety of issues. (Photoshop and Illustrator users will recognize these options from those programs.) You should experiment with them to see what effect works best in each case. The 16 modes are:

• Normal: Colors the selection with the blend color, without interaction with the base color . This is the default mode.

• Multiply: Multiplies the base color by the blend color. The resulting color is always a darker color. Multiplying any color with black produces black. Multiplying any color with white leaves the color unchanged. The effect is similar to drawing on a page with multiple Magic Markers.

• Screen: Multiplies the inverse of the blend and base colors. The resulting color is always a lighter color. Screening with black leaves the color unchanged. Screening with white produces white. The effect is similar to projecting multiple slide images on top of each other.

• Overlay: Multiplies or screens the colors, depending on the base color. Patterns or colors overlay the existing artwork, preserving the highlights and shadows of the base color while mixing in the blend color to reflect the lightness or darkness of the original color.

• Soft Light: Darkens or lightens the colors, depending on the blend color. The effect is similar to shining a diffused spotlight on the artwork. If the blend color (light source) is lighter than 50 percent gray, the artwork is lightened, as if it were dodged. If the blend color is darker than 50 percent gray, the artwork is darkened, as if it were burned in. Painting with pure black or white produces a distinctly darker or lighter area but does not result in pure black or white.

• Hard Light: Multiplies or screens the colors, depending on the blend color. The effect is similar to shining a harsh spotlight on the artwork. If the blend color (light source) is lighter than 50 percent gray, the artwork is lightened, as if it were screened. This is useful for adding highlights to artwork. If the blend color is darker than 50 percent gray, the artwork is darkened, as if it were multiplied. This is useful for adding shadows to artwork. Painting with pure black or white results in pure black or white.

• Color Dodge: Brightens the base color to reflect the blend color. Blending with black produces no change.

• Color Burn: Darkens the base color to reflect the blend color. Blending with white produces no change.

• Darken : Selects the base or blend color ‚ whichever is darker ‚ as the resulting color. Areas lighter than the blend color are replaced , and areas darker than the blend color do not change.

• Lighten: Selects the base or blend color ‚ whichever is lighter ‚ as the resulting color. Areas darker than the blend color are replaced, and areas lighter than the blend color do not change.

• Difference: Subtracts either the blend color from the base color or the base color from the blend color, depending on which has the greater brightness value. Blending with white inverts the base color values; blending with black produces no change.

• Exclusion: Creates an effect similar to, but lower in contrast than, the Difference mode. Blending with white inverts the base color components . Blending with black produces no change.

• Hue: Creates a color with the luminance and saturation of the base color and the hue of the blend color.

• Saturation: Creates a color with the luminance and hue of the base color and the saturation of the blend color. Using this mode in an area with no saturation (a gray) produces no change.

• Color: Creates a color with the luminance of the base color and the hue and saturation of the blend color. This preserves the gray levels in the artwork, and is useful for coloring monochrome artwork and for tinting color artwork.

• Luminosity: Creates a color with the hue and saturation of the base color and the luminance of the blend color. This mode produces the inverse of the Color mode.

  Figure 25-10: The 16 transparency blending modes in the Transparency pane.

  Note ‚

  The Difference, Exclusion, Hue, Saturation, Color, and Luminosity modes do not blend spot colors, just process colors.

  Note ‚

  InDesign's blending calculations differ based on whether the document is to be printed (usually via CMYK) or seen on-screen (as RGB). Be sure to choose the right blending space based on the intended output. To do so, choose Edit ‚ Transparency Blend Space ‚ Document CMYK or Edit ‚ Transparency Blend Space ‚ Document RGB, as appropriate.

You have two other options in the Transparency pane:

• Isolate Blending restricts the blending modes to the objects in a group, instead of also applying them to objects beneath the group. This can prevent unintended changes to those underlying objects.

• Knockout Group obscures any objects below the selected group. But those objects beneath the knocked-out group are still affected by any blend mode settings applied to the group, unless Isolate Blending is also checked.