Soft Proofing PDFs

Soft Proofing with PDF

Soft proofing color is viewing color on your monitor with a screen preview for the way color is printed to hard copy. Rather than print a test proof and consume paper and ink, soft proofing is a digital process whereby you use your computer monitor screen to preview things like proper color assignments, overprints, separations, transparency, and similar issues that might cause problems on printing devices.

With the exception of previewing overprints, all soft proofing options are contained only in Adobe® Acrobat® Professional. Most of the options you find for soft proofing apply to high-end commercial printing; however, some features can be useful when you're printing to desktop color printers.

Printing and soft proofing in Acrobat Professional is a quantum leap in Acrobat development, and the new features added to the program rival the best applications used today for commercial printing.

Proof Setup

The soft proofing commands in Acrobat Professional are contained in the Advanced menu. Select Advanced and choose from options for Custom, Proof Colors, or Overprint Preview.

Custom

Custom enables you to select from a list of ICC (International Color Consortium) profiles. A number of preset profiles are available from which to choose and you can also create your own custom profiles and add them to the list. You create custom profiles with either software applications like Adobe Gamma or hardware/software devices that are designed specifically for calibrating monitors and creating ICC profiles. As a profile is created, it is saved as a file to your hard drive.

In order for Acrobat to recognize the ICC profiles you create, you must be certain that the profiles are stored in the proper directory. By default, utilities and commercial devices used for calibrating color save profiles to a directory that makes them accessible to Acrobat. If you want to remove ICC profiles so fewer profiles show up in the Proof Colors dialog box or you have problems getting a profile to the right directory, open the folder where the profiles are stored. On Windows the path is System32\Spool\Drivers:Color. On Macintosh OS X look in Macintosh HD:Library:ColorSync:Profiles:Displays. When new profiles are added to the folder according to your operating system, you can access the profiles in Acrobat after you quit the program and relaunch it if the profile was added while Acrobat was open.

To select a profile for color proofing, choose Advanced > Proof Colors > Custom and the Proof Setup dialog box shown in Figure 1 opens.

Figure 1: Choose Advanced > Proof Setup > Custom to open the Proof Setup dialog box.

From the pull-down menu you'll see a number of different profiles appear in a long list. If you have an ICC profile developed for your system as the result of calibrating your monitor, select the profile in the list. If you have not created a profile, you can choose from one of the preinstalled profiles. As a general rule, select a CMYK proofing profile such as U.S. Web Coated (SWOP) 2 for files you intend to print as process (CMYK) color. For RGB Files to be printed on the LightJet use ColorMatchRGB.

If you want to preview the PDF document as it theoretically is printed on paper, choose from either an ICC profile you created or from the preset profiles such as Euroscale, SWOP, and so on. For printing on offset press on coated stock use U.S. Web Coated (SWOP) v2. When you select one of the presets for soft proofing prints, the two check boxes for simulating ink and paper become accessible.

To ensure your color proofing uses the same profile each time you view a file onscreen, open a document in Acrobat. Choose Advanced > Proof Setup > Custom and choose the profile that works best in your workflow. Quit Acrobat and re-launch the program. The last choice you made becomes the new default. You do not need to quit the program to make the profile choice a new default, but if the program crashes during a session, you lose preferences applied in that session. Quitting after making a preference choice ensures you that the preference is held in all subsequent Acrobat sessions.

Simulate paper white

If the check box for Paper White is enabled in the Proof Setup dialog box, the preview shows you a particular shade of gray as simulated for the paper color by the profile you choose. You may find that the preview looks too gray or has too much black. This result may not be the profile used, but rather the brightness adjustment on your monitor. If your monitor is calibrated properly and the profile accurately displays the paper color, the preview should show you an accurate representation of the document as it is printed on paper.

Simulate Ink Black

When the Ink Black check box is enabled, the preview shows you the dynamic range of the document's profile. Dynamic range is measured in values usually between 0 and 4, although some scanner manufacturers claim dynamic ranges of 4.1, 4.2, or higher. A dynamic range of something like 3.8 yields a wide range of grays between the white point and the black point in a scanned image. If the dynamic range is high, you see details in shadows and highlights. If the dynamic range is low, highlights can get blown out and shadows lose detail. When you enable the Ink Black check box look for the distinct tonal differences in the preview and detail in shadows and highlights.

Proof Colors

Choose Advanced > Proof Colors to preview the document using a profile you selected in the Proof Setup submenu. If you select the Proof Colors dialog box and choose a profile, the Proof Colors menu command is selected for you. You can turn off proofing without affecting your profile choice by returning to the Advanced menu and selecting Proof Colors again to turn the proofing off.

Overprint Preview

Overprints are often used to trap colors when files are intended for printing separations. Trapping a color creates an overlap between colors so any movement of the paper when printed on a printing press prevents printing colors without gaps between the colors. In other cases, overprints may be assigned to colors in illustrations intentionally where a designer wants to eliminate potential trapping problems. For example, you might assign an overprint to text to avoid any trapping problems where black text is printed on top of a background color. In other cases, a designer might unintentionally assign an overprint to a color during the creative process. As a measure of checking overprints for those colors that you properly assign and to review a document for potential problems, you can use Acrobat's Overprint Preview to display on your monitor all the overprints created in a file. To view overprints in a PDF document, select Advanced > Overprint Preview.

Note: Overprint Preview is available in both Acrobat Standard and Acrobat Professional.

To understand what happens with overprints and knockouts, look at Figure 2. The composite image is created for printing two colors. These colors are printed on separate plates for two different inks. When the file is separated, the type is knocked out of the background, leaving holes in the background as in Figure 3. Because the two colors butt up against each other, any slight movement of the paper creates a gap between where one ink color ends and the other begins. To prevent the problem, a slight bit of overprinting is added to the type. In an exaggerated view in Figure 4 you can see the stroke around one of the type characters. The stroke is assigned an overprint so its color, which is the foreground color, prints on top of the background color without a knockout.

Figure 2: Type is set over a background. Two colors are used and the file is color separated so each color appears on a separate printing plate.

Figure 3: When color is separated and the background color is printed, the background appears with the type knocked out.

Figure 4: If an overprint is assigned to the type, the overprint area of the type color prints on top of the background color. If the paper moves slightly, the overprint prevents any paper color showing through gaps created by the misregistration.

Designers can apply overprints in programs like Adobe Illustrator. If a designer inadvertently makes a mistake and selects the fill color to overprint, the color of the foreground image results in a different color created by the mix of the two colors. In Figure 5 a file is opened in Acrobat and viewed without an Overprint Preview. The figure shows the document as it should be printed. When Advanced > Overprint Preview is selected the overprints shown in Figure 6 appear. As you can see by comparing the figures, the overprints assigned in the file were a mistake. By using Acrobat's Overprint Preview command you can check for any overprint errors contained in your illustrations.

Figure 5: A file is previewed in Acrobat without an Overprint Preview. The file appears as it is intended to be printed.

Figure 6: When you select Advanced > Overprint Preview, all colors assigned an overprint are previewed on your monitor. In this example, the overprint assignments were a mistake.

To carefully examine overprints assigned to type characters, select the Loupe tool in the Zoom toolbar. Move the cursor around the document to preview overprints on small type.

From Adobe Acrobat 6 PDF Bible by Ted Padova. Copyright © 2003 Wiley Publishing, Inc. All rights reserved. Reproduced here by permission of the publisher. To buy this book, visit www.wiley.com.