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Transparency for Print Output in Adobe Creative Suite 3

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Table of Contents

  1. Introduction
  2. New transparency features in CS3
  3. The Adobe Print Engine
  4. New technology
  5. Creating transparency
  6. Transparency: live or flattened?
  7. Designers Guide to Transparency
  8. Creating and viewing transparency effects
  9. Best practices for working with transparency
  10. Transparency effects in Illustrator CS3
  11. Transparency effects in InDesign CS3
  12. Importing and placing files with transparency
  13. Building effects with transparency
  14. Saving and exporting files with transparency
  15. Printing files with transparency
  16. Delivering files with transparency to your print service provider
  17. Transparency-related resources
  18. Transparency: A Print Production Guide
  19. Best practices when flattening
  20. Flattening basics
  21. Advanced Flattener controls
  22. Flattening controls in Illustrator CS3
  23. Flattening controls in InDesign CS3
  24. Flattening controls in Acrobat 8 Professional
  25. Transparency and color
  26. Troubleshooting
  27. Glossary

Transparency: A Print Production Guide

Flattening basics

Flattening transparency accurately reproduces—by using opaque objects—the visual effect of transparency on printed output or in exported file formats that don’t support live transparency. You can flatten files containing live transparency using Adobe Illustrator CS3, Adobe InDesign CS3, or Adobe Acrobat 8 Professional: either directly open the file or place it as a graphic, and then print or export it. In addition, available only in Illustrator, you can flatten individual selected objects.

The Transparency Flattener (Flattener) built into Illustrator CS3, InDesign CS3, and Acrobat 8 Professional performs the conversion, according to how you’ve set it up based on the output requirements of the job. The Flattener works, where necessary, by breaking up transparent objects into smaller nontransparent objects. The technology uses various methods: breaking up parts of the artwork that overlap transparent areas, into smaller opaque regions to simulated the transparent effects; clipping overlapping regions of transparency into smaller groups; or simply rasterizing artwork into a bitmap.

Transparency in Adobe publishing applications is referred to as either live (editable, interactive with underlying objects, or both) or flattened. To keep your workflow as flexible as possible, keep transparency live as long as possible until the final output (up to and including flattening in the RIP). This lets you take advantage of transparency’s device independence (as vector art rather than raster images with fixed resolution); how easily it can be edited; and the ability to make last-minute production decisions without worrying about settings used for previously flattened items.

When planning your production workflow, you can make wise decisions about flattening transparency if you’re familiar with the process and the file formats that can contain live transparency.

See

Live transparency

The transparency attributes of objects created in Adobe publishing applications stay live and fully editable while in their native Photoshop CS3, Illustrator CS3, or InDesign CS3 format. That same transparency remains live, but not editable, when placed or imported into non-native applications that support the native file format (such as PDF 1.4, 1.5, 1.6, and 1.7).

See also

Live and editable transparency

The following file formats can contain live transparency that interacts with objects beneath them, allowing those objects to show through. For best results, use the latest version of the software:

  • AI: Adobe Illustrator 9, 10, CS, CS2, and CS3.
  • INDD: Adobe InDesign 2, CS, CS2, and CS3.
  • PSD: Adobe Photoshop 6, 7, CS, CS2, and CS3.
  • PDF: Adobe PDF 1.4, 1.5, 1.6, and 1.7 (Acrobat 5, 6, 7, and 8, respectively). PDF/X-4, which is based on PDF 1.4 or later.
  • TIFF: Version 6 (TIFF files saved from Photoshop 6 or later).

Transparency kept live until printing

The following file types let you keep transparency live (but not necessarily editable) until print time. For best results, use the latest version of the software:

  • AI files from Illustrator 10, CS, CS2, and CS3.
  • PDF 1.4, 1.5, 1.6, and 1.7 files created directly in Illustrator 9, 10, CS, CS2, or CS3; InDesign 2, CS, CS2, or CS3; or saved by Acrobat 5, 6, 7, or 8 Professional.

Note: Because Acrobat Distiller software creates PostScript files, which do not support live transparency, PDF files created by Distiller won’t contain live transparency.

These file types let you keep transparency live until print time, if they were saved with the Preserve Illustrator Editing Capabilities option chosen, and then opened in Illustrator:

  • EPS from Illustrator 9, 10, CS, CS2, and CS3.
  • PDF 1.3 from Illustrator 9, 10, CS, CS2, and CS3.

Note: These EPS and PDF 1.3 files will contain flattened transparency. However, the formats contain all of the live transparency information in an Illustrator-specific section of the file. You can access the native Illustrator data by opening the file in an appropriate version of Illustrator. Then you can edit the live transparency and resave it with the appropriate flattener settings.

Flattened transparency

Transparency is flattened when a file containing live transparency is converted into a format that doesn’t support live transparency, or the file is printed. Conversion is the job of the Flattener. During the flattening process, the Flattener replaces transparent objects with objects that are visually equivalent to the transparent orignals, but that contain no transparency. These new opaque objects are often referred to as flattened transparency. Flattened transparency does not contain any live transparent elements and, therefore, cannot be manipulated. Be sure to save a copy of the unflattened artwork for future editing if you think you may need to change artwork after flattening has occurred.

The following common file types do not support live transparency (the Flattener must flatten transparent objects prior to printing or exporting): PostScript, EPS, DCS, PDF 1.3 (Acrobat) and earlier, PDF/X (PDF/X-1a and PDF/X-3), GIF, JPEG, BMP, and versions of TIFF that do not conform to the TIFF 6.0 specification (for example, TIFF files created with a version of Photoshop software prior to version 6.0).

You can also flatten files containing live transparency Illustrator CS3, InDesign CS3, or Acrobat 8 Professional.

Determining whether an object will be flattened

An object that has a transparency effect applied to it is called a source of transparency. An object or placed file that appears beneath a source of transparency (regardless of the layer it is on) interacts with transparency. The Transparency Flattener processes both objects that are a source of transparency and those that interact with transparency, possibly changing their composition in the output.

An object is a source of transparency if it has any of the following:

  • An opacity of less than 100%.
  • Any blending mode other than Normal.
  • An opacity mask (Illustrator).
  • A drop shadow or feather.
  • An inner glow or outer glow effect or other live effects (Illustrator; Figure 31).
  • A fill or stroke with a style, brush, pattern, or filter effect that has any of the previous properties.

In addition, an object is a source of transparency if it is one of the following placed files:

  • Photoshop (native, PDF, or TIFF) file with a transparent background.
  • Illustrator (native or PDF) file that contains one or more objects with any of the previous properties.

Illustrator CS3 Transparency panel, and examples of transparency effects

Figure 31. Top: Illustrator CS3 Transparency panel: A. Blending mode  B. Opacity  C. Opacity Mask. Bottom: examples of transparency effects: None (left), Inner glow (center), and outer glow (right).

In general, an object interacts with transparency if it is:

  • A source of transparency.
  • Overlapped by a source of transparency.
  • Very close to (usually within 1 point) a source of transparency and beneath it in stacking order (including objects on other layers).

The best way to determine whether an object interacts with transparency is to use the Flattener Preview in Illustrator CS3, InDesign CS3, or Acrobat 8 Professional. Without using the Flattener Preview, it’s difficult to determine whether an object interacts with transparency.

See also

Previewing overprinting

When flattening transparency that interacts with spot colors, the Flattener may use overprinting to render the proper result; opaque objects will simulate transparent effects. To display and print the transparency correctly, you must use software (a RIP or previewing application) that supports PostScript overprinting. Without overprinting support, objects set to overprint will instead knock-out the objects beneath them (Figure 32).

Be sure to set your PDF viewers, composite proofers, and production RIPs to implement overprinting and not ignore it.

To turn on Overprint Preview, in Illustrator CS3 and InDesign CS3, choose View > Overprint Preview. In Acrobat 8 Professional, choose Advanced > Print Production > Overprint Preview. This allows you to properly view flattened transparency in a PDF file in Acrobat 8 Professional or Reader 8, as placed in an InDesign CS3 document.

Note: You can also set objects to overprint in Illustrator and InDesign, but that overprinting is not a form of transparency and does not need to be flattened. To see how overprinting affects the objects, be sure to turn on Overprint Preview.

Overprint Preview in Acrobat 8 Professional with black and spot-color blue.

Figure 32. Overprint Preview in Acrobat 8 Professional with black and spot-color blue. Left: Off; drop shadow overprints on top of a spot color. Right: Overprint Preview On; how the image appears on output devices that support overprinting.

About the flattening process

The more complex a design (mixing images, vectors, type, spot colors, overprinting, and so on), the more complex is flattening and its results. To achieve the visual effect of transparency with the use of opaque objects, the flattening technology examines the interactions at every point of the transparency. The Flattener assesses if the objects involved can be kept in their original form (for example, vectors as vectors or type as type), if they can be converted to a related form (for example, type to outlines), or if the entire region must be rasterized because of its complexity. Flattener settings control the following:

The Flattener does several things to the objects involved:

  • The Flattener cuts the original transparent objects apart and replaces overlapping transparent regions with a set of discrete, abutting objects called atomic regions, that are either vector objects or rasterized areas. Each atomic region stands on its own and does not rely on underlying or overlapping objects for its final appearance (Figure 33).

     

    The flattening process: Cut apart transparent objects represent overlapping areas as discrete pieces, either vector objects (shown here) or rasterized areas. Live transparency (left) is split into flattened atomic regions (center). Final output (right) simulates the original, but uses opaque elements.

    Figure 33. The flattening process: Cut apart transparent objects represent overlapping areas as discrete pieces, either vector objects (shown here) or rasterized areas. Live transparency (left) is split into flattened atomic regions (center). Final output (right) simulates the original, but uses opaque elements.

  • When using the built-in High Resolution Flattener preset, the Flattener retains the integrity of original transparent objects whenever possible (for example, type remains type and vectors remain vectors). Depending on the complexity of a design and the flattener settings used, it may convert type or strokes to outlines or expand patterns.
  • If an object being processed by the Flattener has either its fill or stroke set to overprint, the Flattener may process the overprinting. If the Flattener processes overprinting, the flattened objects it creates won’t have any overprinted fills or strokes.

See also

Flattening individual objects in Illustrator CS3

Available only in Illustrator, you can flatten individual selected objects. Note that flattening this way is not recommended: It’s best to keep transparency live until just prior to printing, to keep files with transparency as device independent as possible.

To flatten individual objects in Illustrator CS3:

  1. Select the objects you want to flatten.
  2. Choose Object > Flatten Transparency (Figure 34).

     

    The Illustrator CS3 Flatten Transparency dialog box with a preview of a flattened object.

    Figure 34. The Illustrator CS3 Flatten Transparency dialog box with a preview of a flattened object

    Two options are unique to the Object Flattener’s Flatten Transparency dialog box (and unavailable in the Flattener Preset Settings dialog box): Preserve Alpha Transparency and Preserve Overprints and Spot Colors.

  3. Select Preview option to view what will happen during flattening and what the Flattener will do at various settings.
  4. Click OK to flatten the selected objects. Once flattened, the transparency effects are no longer live and their appearance is not easily modified.

See also

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