How does transparency work in Adobe® InDesign®?

InDesign’s four main transparency effects can be used to create cool designs, but it is important to understand how transparency works so the printed output matches the intended design.

TRANSPARENCY DEFINED
Transparency is an effect applied to a page element that makes the underlying elements visible. One can see through an element to elements underneath it.

Drop Shadow
When you add a drop shadow to an object, a soft-edged duplicate shape of the object is displayed behind the object, making it appear that a shadow is being cast on the page background or any underlying objects. The effect can be a blending of the shadow with any underlying object.

Feathering
Feathering softens the edges of an object by fading the object from opaque to transparent over a user defined distance. Feathering the edge of an object causes the object to fade smoothly outward and blend into the page background or any objects behind it.

Blending Mode
The option to apply any of several blending modes to objects lets you vary the way the colors of objects blend with the colors of underlying objects.

Opacity
You can vary the degree of transparency of an object or a group by adjusting its opacity. An object with an opacity of 100 percent is totally opaque (that is, you can’t see anything behind it); an object with an opacity of 0 percent is totally transparent. As you decrease an object’s opacity, the page background or any underlying artwork becomes increasingly visible through the object.

FLATTENING
If you’re going to create transparency effects, you should also understand a little bit about flattening. All transparent objects in a file—as well as all linked graphic files that interact with transparency— must be flattened for print output, including PostScript®, Encapsulated PostScript (EPS), and PDF 1.3 and earlier. At its simplest, the process of flattening converts all overlapping areas in a stack of transparent objects into a collection of opaque objects that retains the appearance of the original transparent objects when printed.

In the example below, the two overlapping objects result in three atomic regions after flattening.

• Left (live transparency): Two objects overlap.
  • The blue object is in front of the pink object
  • The Multiply blending mode is applied to the blue object.
• Center (flattened transparency, exploded view):
  • Flattening the two objects produces three atomic regions.
• Right (flattened transparency, non-exploded view):
  • The printed results look the same as the original objects

TRANSPARENCY DILEMMA
Keep in mind when working with transparent objects that as the number of overlapping transparent objects increases, so does the complexity of the transparency effects.

Atomic regions (below):

• Left is the live transparency.
• Center is the flattened transparency, exploded view.
• Right is the flattened transparency, non-exploded view.

FORCE TEXT TO OUTLINES
When text gets involved with transparency (either it is transparent or something is transparent on top of it), the type almost always gets turned into paths which act as clipping paths. This can slow down printing and sometimes the text appears thicker than the equivalent characters that aren’t converted to outlines. The problem with thickening type is also an issue around thin lines.

Generally, type should be on top of all other objects unless it is supposed to interact with transparency. Placing text frames and spot colors on the top of the stacking order will help keep them from being involved in transparency flattening.

Contributed by:
Debbie King
Technical Support Adviser
Herff Jones Kansas City Printing Facility