At first, it was just the occasional shadow, and that was kind of novel. But then everyone got carried away—show me a headline, and I’ll show you text with a drop shadow (figure 1). There’s something fundamentally appealing about transparency: Start with simple elements, throw in a little peekaboo and things are more interesting. But, to paraphrase your mother, it’s all fun and games until somebody can’t print his job.

Of course, we’ve had transparency in Adobe Photoshop for many years. But its introduction in Adobe Illustrator 9.0 meant that vectors could play along. Adobe InDesign 2.0 brought transparency to page layout, and designers cheered. Printers, on the other hand, hid under their light tables, hoping it would go away. But the see-through cat is out of the bag—even QuarkXPress 7.0 contains transparency effects now.

What could be scary about transparency? Well, for starters, PostScript—the page-description programming language that powers many desktop printers and the imaging devices used by commercial printers—doesn’t understand transparency at all. As you’ll see, there are some accommodations you must make when creating transparent artwork, and some small modifications your printer needs to make to standard imaging workflows.

How applications handle transparency
Popular graphics applications create and handle transparency effects differently, with differences in imaging models and limitations. Within a single application, things aren’t too scary. It’s when you start cross-pollinating between applications that you hit some roadblocks.

For example, it’s easy to stack up multiple layers in a Photoshop file, assigning opacity settings and blending modes to allow the layers to visually interact. Shadows created within Photoshop correctly darken content underneath using the Multiply blending mode—as long as you remain in Photoshop.

But place that Photoshop file into Illustrator, InDesign or QuarkXPress, and the shadow knocks out what’s underneath—not the effect you want (figure 2). For some work-arounds, see the sidebar “Making Shadows Image Correctly” on page 28.

Although opacity in a Photoshop-layered, native file is honored by other applications, Photoshop blending modes—such as Multiply—are not translated correctly. Why is this? Photoshop’s internal imaging model differs somewhat from the model used in other Adobe applications and in QuarkXPress. The situation is much better for native Illustrator (.ai) files placed in InDesign because the two applications share the same imaging model. Happily, opacity and blending modes in Illustrator files—including shadows—are fully supported by InDesign. Whoopee!

QuarkXPress solves this dilemma by offering no support for native Illustrator files. Even version 7.0 allows only Illustrator EPS files, which cannot contain any transparency.

Figure 1: They’re everywhere: We can’t stop ourselves from adding drop shadows to everything. Remember, just because you can, doesn’t mean you should.

Figure 2: A Photoshop shadow initially looks fine in InDesign— or Illustrator or QuarkXPress. But viewing separations (right, with black plate turned off) shows that the shadow behaves as if it’s opaque, actually knocking out what’s underneath.

What do you mean, you flattened my file?
Because our primary print-imaging model, PostScript, doesn’t understand native transparency, applications that allow transparency have to “predigest” transparent content, turning it into PostScript-legal content that looks transparent.

When transparency first appeared in Illustrator 9.0, that digestion process—called flattening—wasn’t as sophisticated as current versions, and printers didn’t know quite how to image such content. The flattening process assumed that RIPs (Raster Image Processors) would be sophisticated enough to use the full complement of PostScript Level 3 operators, and a print file was generated based on that assumption. The flattener was counting on the RIP to “Do the Right Thing.” However, even RIP vendors who licensed PostScript from Adobe didn’t necessarily implement every single arcane programming command and were caught short by this newfangled stew, allowing instances of rasterized text and other unattractive artifacts to occur.

Fast-forward to present day: Flattening procedures currently used by Illustrator, InDesign and QuarkXPress are much more elegant and more effective, and major vendors have updated their RIPs to handle transparency.

Curious about what happens during flattening? InDesign, Illustrator and QuarkXPress analyze transparent content at the time of print or export, replace that content with opaque “stunt doubles” that PostScript understands and assign overprint attributes to polish it off (figure 3). In some cases, text must be converted to outlines to preserve a visual effect, but output correctly. Some situations may require that some objects are rasterized. It’s a pretty amazing engineering feat.

Figure 3: Flattening replaces transparent content (A) with opaque objects and assigns overprint attributes as necessary to image correctly (B).

Figure 4: You can’t have more than 100 percent of a single color unless you print multiple plates of that color. But InDesign’s normal view misleads you into thinking you can (top). Turn on Separations Preview (bottom), and InDesign displays the truth. Roll your mouse over an area of the page to view the percentages of each color in the palette.

Best practices
You can develop some healthy habits as you create transparency effects. Herewith, a checklist:

General Guidelines
1. Convert all unnecessary spot colors to process before output.
2. If possible, put text and linework above transparent effects in stacking order.
3. Don’t use opacity when a simple tint will suffice.
4. Avoid mixing RGB and CMYK content in a single document.
5. If you are working in an OPI workflow (low res/ high res swap), the high-resolution images must be in place before export/output. (If this doesn’t ring a bell, you’re probably not using an OPI workflow.)

Illustrator:
1. Before creating shadows or other soft-edged effects, set the appropriate resolution: Effect > Document Raster Effects Settings. A value of 200- 300 ppi at final size is appropriate. Where possible, use Effects rather than Filters. Effects are live effects that can be edited at any time, whereas Filters create literal content that’s more difficult to modify.
2. Embed any images involved in transparency.
3. Lastly, save as native Illustrator files for placement in InDesign.

InDesign:
>1. Use InDesign’s forensic tools to see a more faithful rendition of content: Choose Window > Output > Separations Preview, and you can view individual separations as well as color percentage values of all content (figure 4).
2. When printing or exporting to PDF or EPS, choose the High Resolution Flattener setting (under the Advanced controls in print and export dialogs). This ensures that any shadows or feathered edges have adequate resolution.
3. Ask the printer how you should submit your files, and whether special considerations exist because of the imaging workflow. Some printers want PDFs, and some want the packaged InDesign files plus fonts and support art. Never assume.

QuarkXPress 7.0:
1. Earlier builds of QuarkXPress 7.0 may struggle with even moderately complex transparency, crashing when you attempt to print or export. Update your installation to the current build, 7.1. On the Mac, you’ll have to install the 7.01 patch first. On Windows, you can apply the 7.1 update to the base 7.0 install without intermediate patches.
2. If you’re applying the same type of shadow to several objects on a page, group them first and then apply the shadow to the group as a whole. Looks the same, but prints and RIPs faster.
3. If you want a soft-edged silhouette on a Photoshop image, don’t use the Alpha Channel clipping approach. It just creates a harsh vector edge based on the pixels of the alpha channel. Instead, use a Layer Mask in Photoshop for true, soft-edged transparency.

White line fever:
misleading display in Acrobat
InDesign and Illustrator use an internal PDF Library to generate PDFs. QuarkXPress uses a non-Adobe solution from Global Graphics. Both methods make legal PDFs. Your print service provider should provide specifications for PDF creation. (If they say, “just send any old PDF,” that’s not a good sign.)

Acrobat versions 5.0 and later support live, unflattened transparency because the imaging model goes beyond PostScript limitations. Sounds great, doesn’t it? However, most current imaging devices are going to convert such PDFs into PostScript anyway, using their own recipes. So, unless your printer explicitly sanctions late-model PDFs, you should create PDF/x-1a files, which are Acrobat 4.0-flavored. Sounds fancy, but it’s a one-click preset choice in QuarkXPress and InDesign (File > Export), as well as Illustrator (File > Save).

Be forewarned: Your PDF may not appear correctly when viewed in Acrobat, for several reasons. Because the flattening process requires overprint to render some transparency effects in a PostScriptlegal form, you’ll need to turn on Overprint Preview in Acrobat (figure 5). In Acrobat 7.0, choose Advanced > Overprint Preview. In Acrobat 8.0, choose Advanced > Print Production > Overprint Preview. You’ll find this necessary when transparency (such as drop shadows) interacts with spot color content.

As figure 3 shows, the flattening process cuts content into little puzzle pieces. When you view such a PDF in Acrobat, you’re appalled by what seem to be gaps between those pieces, an artifact called stitching. There’s actually no gap: The pieces really touch and fit perfectly. But Acrobat anti-aliases vector edges to improve display, and the white lines are an unfortunate side effect of that effort. You can turn off the effect in Acrobat preferences (Acrobat > Preferences for Mac or Edit > Preferences for PC) by unchecking “Smooth line art.” But then you’ll encounter another side effect: Any text that was converted to outlines during flattening will look very rough (although it images fine). So you have to decide which irks you more—imaginary white lines or imaginary rough edges (figure 6).

Figure 5: Oh, no! It’s the Dreaded White Box Syndrome! Overprint Preview is off by default in Acrobat (left). Turn on Overprint Preview, and you’ll see that all is well (right). The file is fine: Acrobat is trying to reduce computational overhead (OK—being lazy).

Figure 6: The white “stitching” lines you see in Acrobat are not gaps—they’re a result of Acrobat’s anti-aliasing to ensure smooth linework display. But turning off “Smooth line art” causes outlined text to look rough. Keep in mind that both ugly effects are just display artifacts—the file will print correctly.

What your printer needs to do
While RIPs have matured and flattening is much more sophisticated than it was at the dawn of transparency, a few tweaks by the print service provider are still necessary to ensure proper imaging.

Remember how you had to turn on Overprint Preview in Acrobat for correct display of transparency involved with spot colors? Well, your printer has to turn on PostScript overprint in the RIP to correctly image such effects. (In most workflows, it’s turned off.) If you receive a contact proof with Dreaded White Box Syndrome, remind your printer to turn on PostScript overprint.

Some RIPs think they need to trap the flattened puzzle pieces to each other, leading to unnecessary visible trap lines. Your printer may have to create a modified queue to prevent this. And, on Rampage RIPs, it may be necessary to turn off something called Dual Rasterization to prevent an effect similar to Acrobat’s White Line Fever. Each RIP has its own hardware and software, and thus its own particular set of issues. The RIP’s vendor can help your printer find patches and a work-around to correctly image challenging files.

Additionally, if your printer is a member of Adobe Solutions Network, the company is eligible for extensive tech support directly from Adobe to help deal with any software issues. If the company isn’t a member, it should join to receive the great resources available.

A postscript: beyond PostScript
After all these years, PostScript may be ready to retire. Adobe’s new PDF Print Engine goes beyond the capabilities of PostScript, allowing live transparency and true PDF-native workflows. It will soon begin appearing in commercial RIPs and will eventually make its way into our desktop printers. Just imagine—no more problems with transparency!

Don’t worry; we’ll come up with something else to challenge the new technology. We always do!

SIDEBARS:

Recommended resources:
QuarkXPress transparency guide
http://tinyurl.com/2t6z8h

A Designer’s Guide To Transparency
Adobe’s guide to creating and printing transparency from Illustrator, InDesign and Acrobat.
http://tinyurl.com/2dl6jj

For you: Find an Adobe Solutions Network printer:
http://tinyurl.com/yrdzvm

For your printer: Adobe Print Service Provider Resources
http://tinyurl.com/dugds

PDF Print Engine
If you’re curious about the Next Big Thing in imaging, check out Adobe’s information page: http://tinyurl.com/p2kg4

Imaging Photoshop Shadows Correctly From Other Applications
If it’s a simple shadow—one of those down-and-to-the-right numbers— just create the shadow in the page layout rather than in Photoshop. However, if you need a fancy cast shadow that can’t be accomplished with simple drop shadow options, you’ll have to cheat. If you’re planning to place such an image into Illustrator or InDesign, you’ll need to make a “shadow sandwich.”

In Photoshop, create the shadow on a separate layer so that you can handle the object and its shadow separately. For use in Illustrator, you’ll need to save two versions of the image—one for just the object (no shadow), and one for just the shadow alone. Place the shadow image, and use the Transparency palette in Illustrator to assign the Multiply blending mode. Then place the image containing only the object and align it vertically and horizontally with the shadow image.

If your destination is InDesign CS2, there’s no need to separate the object and shadow layers into two separate images because InDesign can do that for you. Place the image into InDesign, select the frame with the Selection tool (black arrow) and then copy it to the Clipboard (you’ll see why in a second). Your original frame should still be selected: Choose Object > Object Layer Options. Using the controls in the dialog box, turn off the visibility of the object layer, leaving only the shadow layer visible. Then, in the Transparency palette, set the frame’s blending mode to Multiply. Now it’s time to finish the sandwich. Choose Edit > Paste in Place to plop the Clipboard image into the page. Using Object Layer Options (below), turn off the shadow layer, leaving only the object. All done! Yes, it’s a bit tedious, but it ensures that your shadow will output correctly.

If you’re using QuarkXPress, you may still have to accomplish this the old-fashioned way— by building a complete composite of image, shadow and background elements in Photoshop—because QuarkXPress through version 6.5 doesn’t provide any drop shadow or blending mode options. QuarkXPress 7.0 doesn’t support blending modes from Photoshop, nor does it allow you to assign a blending mode to an object, but it does allow you to skew and scale its own drop shadows. This is kludgy, but it images correctly.

Coming up
In the next issue, we’ll take a peek at upcoming new software releases that will give you a good case of Shrinkwrap Lust.

Claudia McCue is a consultant, trainer and writer focused on the practical aspects of designing for print. She is author of Real World Print Production (Peachpit Press) and a frequent presenter at industry conferences.