16. Color Management and PDF: The Wave of the Future
“Once upon a time, there was a great ... no wait, wrong story” is often Chris’s initial thought when the subject of PDF arises. So much promise, so many problems (just like color management, sometimes), but anything worthwhile usually involves a fair bit of work. Over the years, PDF has been touted as the solution to so many different problems—as Bruce likes to say, “it’s a dessert topping and a floorwax”—that it’s often been hard to figure out just what it is good for.
PDF workflows can bring numerous benefits and numerous pitfalls, most of which we’ll ignore in this chapter. We won’t attempt to compete with the variety of excellent books and primers on PDF; instead we’ll simply give you a status report on the interaction between PDF and color management. We can tell you a lot, but there are still a huge number of unknowns, so you’re doubly on the bleeding edge when you deal with color management in PDF.
Why a chapter on PDF and not on Acrobat? First, PDF is much bigger than just Acrobat—many PDF workflows don’t even use Acrobat—so the real story is about PDF. The Portable Document Format (which is what PDF stands for) is designed as a platform-neutral container for all types of digital content, allowing that content to be distributed without requiring the recipients to possess, or even have any knowledge of, the various applications that generated the various components in the document. This flexibility is a mixed blessing for print publishers, so much of the ongoing effort in developing standards for PDF workflows involves defining subsets of PDF features that define what is and is not allowable in PDFs designed for print workflows.
It’s important to keep in mind that there are two halves to PDF: the file format half of PDF that gets most of the attention, and the equally important but often-overlooked usage half. We intend to focus primarily on the usage of PDF in a color management context, but to do so, we first need to talk about the various flavors of PDF that interest us.
The Flavors of PDF
Unlike PostScript, the Portable Document Format is an open one—Adobe publishes current versions of the specification so vendors can decide which aspects of each version they want to implement. Sounds like a recipe for chaos, and in some ways it is, but there’s also a method to the madness.
PDF Versions
There are four basic versions of the PDF specification: we’re primarily interested in only one of them, but we mention the others for the sake of completeness.
• PDF 1.2. This is the version of PDF produced by Acrobat 3, and it’s completely ICC-unaware, lacking any mechanism for supporting ICC profiles.
• PDF 1.3. This is the highest version of PDF produced by Acrobat 4, and the default for Distiller 5. It supports the embedding of ICC profiles on a per-object basis. This is the version of PDF that’s most interesting to the color management world.
• PDF 1.4. This is the version of PDF produced by Acrobat 5, and the highest version produced by Distiller 5. It too supports ICC profiles, along with transparency and a host of other features that lie outside the scope of this book.
• PDF 1.5. Acrobat 6 Standard and Professional will produce PDF conforming to this specification. It supports ICC profiles, transparency, better compression including JPEG2000, enhancements to encryption, and again all sorts of things outside the scope of this book.
Embedded profiles
PDF supports multiple objects (images—both vector and bitmap—as well as text, shapes, backgrounds, etc.). PDF can contain objects in different color modes, and each object can have an ICC profile associated with it as long as that mode supports ICC profiles. You could, for example, have multiple RGB, CMYK, and grayscale objects, each with a different source profile.
To minimize file size, each object references its source profile instead of having the profile embedded in the object—so six objects with Adobe RGB (1998) as their source profile don’t cause six copies of Adobe RGB (1998) to be embedded in the PDF, but rather just one copy referred to six times. These objects have a color space called “ICC-Based,” which means they’re considered device-independent.
Any object that doesn’t reference an ICC profile is device-dependent, denoted as: /DeviceRGB, /DeviceCMYK, and /DeviceGray, as the case may be.
Other noteworthy items
Rendering intent is set at the time the profile is embedded and is not related to the default rendering intent in the ICC profile. Also, destination profiles are not embedded in PDF documents, at least not yet.
PostScript Color Management
PostScript’s color-management philosophy has affected PDF’s color-management philosophy, and thus its behavior, so a little history is in order.
PostScript color management predates ICC-based color management, and is built-into RIPs with PostScript version 2017.xxx and greater. PostScript profiles are always unidirectional, so there are always at least two profiles for an output device. One profile is used as a source profile (device to PCS) called a Color Space Array, or CSA for short. The other is used as a destination profile (PCS to device) called a Color Rendering Dictionary, or CRD for short. CRDs only contain a single rendering intent, so there’s a separate CRD for each rendering intent.
Fundamentally, PostScript color management operates in the same way ICC-based color management does: CSAs and CRDs, like profiles, establish a relationship between device values and PCS values, and the color management system uses the information they contain to convert the device values, using a specified or default rendering intent.
Where do CSAs and CRDs live?
The usual location is in the RIP itself, and it’s all-too-common for built-in CSAs and CRDs to have no basis in reality either as assumed source profiles or as descriptions of the behavior of the output device in question, so the resulting conversions are frequently hideous. Recent products—in particular, newer color laser printers—have more reasonable RGB CSAs and CMYK CRDs, so the printers can receive RGB graphics and convert them properly to printer CMYK. But that’s still the exception rather than the rule.
The other location is in the PostScript print stream itself. The RIP then uses the CSAs and CRDs in the PostScript file instead of the built-in ones. If you create a PostScript stream that contains CSAs but not CRDs, the built-in CRDs are used.
In theory, each object gets its own CSA (source profile) and is also tagged with the CRD that should be used (because the CRD controls the rendering intent). Then the RIP uses each CSA and included CRD to perform color space conversions in the RIP. In practice, though, you quickly find out that some RIPs ignore CMYK CSAs altogether, others ignore CSAs in the print stream and use only built-in CSAs, and still others ignore CRDs as well. When it comes to implementing such a system, you usually end up with a mess (the fact that the most common page-layout program, QuarkXPress, can’t produce either CSAs or CRDs doesn’t help).
PostScript to PDF, PDF to PostScript
Enter PDF 1.3, which uses ICC profiles, not PostScript color management. Adobe created a mechanism whereby with PDF 1.3 and higher, profiles and CSAs can be interchanged when the document is converted from PostScript to PDF and vice versa. When you print a PDF to a PostScript printer, it’s turned back into PostScript, and all the ICC source profiles become PostScript CSAs. When you convert PostScript into PDF, all CSAs are converted into ICC profiles, and any CRDs are simply tossed into the bit-bucket.
You may have experienced Acrobat Distiller 3 and 4 converting CMYK images into LAB. This generally happens when those versions of Distiller encounter a PostScript CSA embedded in a CMYK EPS (probably from Photoshop with the “PostScript Color Management” checkbox selected). Distiller 5 either converts the CSA into an ICC profile or ignores it entirely, depending on the Distiller color settings.
With the possible exception of thoroughly troubleshot proofing systems, we recommend avoiding PostScript color management unless you’re one of the handful of people who’ve already gotten it to work reliably. If you have, congratulations—maybe you should write a book!
PDF/X
PDF supports many different types of digital content, but it doesn’t really help your PDF print workflow at all when the PDF contains the sixth Brandenburg Concerto or the latest Star Wars movie. So the PDF/X format and usage guidelines were created to ensure that PDF/X compliant PDFs contained only the data required for print. PDF/X is rapidly emerging as the standard for PDF-based print workflows.
Did we say “standard”? Of course, life is rarely that simple, and while the PDF/X bandwagon continues to gather momentum, PDF/X isn’t just one standard. Instead, it has several different conformance levels, predicated primarily on the PDF 1.3 specification, that fall under the umbrella of International Standard ISO 15930 as follows:
• PDF/X-1a:2001. This version, defined in ISO 15930-1:2001, is designed for “blind transfer” of print data in press-ready form—the PDF itself contains all the elements needed to print. Color must be CMYK (plus optional spot) only, and all images and fonts must be embedded. It is based on the PDF 1.4 spec, but explicitly prohibits the use of transparency. It’s also a pure subset of PDF/X-3:2002.
• PDF/X-2:2003. This version, defined in ISO 15930-2:2003, is functionally similar to PDF/X-3 but allows for externally referenced data, so it isn’t usable for blind transfers, and uses portions of PDF 1.4.
• PDF/X-3:2002. This version, defined in ISO 15930-3:2002, allows device-independent color. This includes LAB, as well as tagged RGB and tagged CMYK data. Untagged device dependent data is also allowed. As with PDF/X-1a:2001, it’s designed for blind transfers, and hence all images and fonts must be embedded. It’s a subset of PDF/X-2.
All versions of PDF/X were updated in 2003. The current versions all have 2003 in the name, but the changes are more clarifications. They’re based on PDF 1.4, but transparency is expressly prohibited for example. We know of no third-party products supporting the 2003 versions. Effectively, the versions listed earlier are currently supported.
We expect that PDF/X-1a will become the dominant standard for blind transfers in the United States since this market is primarily CMYK-only (plus optional spot) and rarely works with device-independent data requiring additional handling at output time. Both PDF/X-1a and PDF/X-3 will become the dominant standards for blind transfers in the European market. PDF/X-2 can be used anywhere an OPI workflow is currently being used, and as an internal format inside large enterprises. Since it supports usage of externally referenced data, and supports both device-dependent and -independent color, it can reference images, fonts, or PDF/X-1a and PDF/X-3 documents.
Various third-party tools make creating PDF/X straightforward—we discuss some of them in “Third-Party Stuff,” later in this chapter. While you can make PDF/X directly using Acrobat 6 Professional, and InDesign CS, third-party tools are still very useful, and sometimes necessary.
For more information on PDF and PDF/X, check out these resources:
OutputIntent
All PDF/X documents must have an OutputIntent specified. This can be an ICC-registered print condition name or an ICC profile. That means there’s an implicit and an explicit possibility. The implicit one is really vague, in our opinion—check out the ICC registry at www.color.org/registry2.html, and you’ll see what we mean. So we recommend setting the OutputIntent with an actual ICC profile, at least until the registry matures into something useful. If you produce a PDF/X-2 or PDF/X-3 document that contains device-independent data, the output intent profile must be fully embedded.
PDF/X-1a
By far, PDF/X-1a interests us the most since it’s relatively straightforward and has strong vendor support. Objects must be device-dependent (CMYK plus spot) color—ICC-Based color isn’t allowed. However, an OutputIntent is required. It’s important to realize that while you can use an ICC profile for the OutputIntent, the objects in the document are still device-dependent because PDF/X-1a prohibits per-object ICC profiles. The primary intent of the OutputIntent in PDF/X-1a is for verification purposes—it’s there to ensure that the document has been color managed to a specific destination in mind, and if that doesn’t match what’s in the job order or ticket, someone needs to pick up the phone and get clarification.
The OutputIntent is the profile that was used for color separation of the PDF’s content, so it becomes the source profile for all CMYK content (which is everything except for spot color).
PDF/X-3
PDF/X-3 can contain device-dependent data (either untagged RGB or untagged CMYK, but not both in the same document), as well as device-independent data (tagged RGB, tagged CMYK, and LAB). Each device-independent object, by definition, has an ICC profile associated with it, and the actual color space is referred to as “ICC-Based.”
For PDF/X-3, the OutputIntent is the source profile for the untagged device-dependent data, and is the intended destination profile for device-independent data. So the device-dependent data must be separated for the intended output already, as it won’t be converted again. This is the only PDF/X variant that
• Allows a destination profile to be included in the PDF for the explicit purpose of performing conversions
• Supports device-independent data
• Supports RGB output devices
PDF/X-3 is a superset of PDF/X-1a, which means that anything that claims to be a PDF/X-3 compliant reader must also correctly handle PDF/X-1a. Likewise PDF/X-2 is a superset of PDF/X-3. The numbers are out of sequence, but that’s the order the standards were agreed upon.
If your goal is to convert everything to CMYK in advance (an early binding workflow), and submit a CMYK-only (plus optional spot) file, you should make PDF/X-1a. The notion that one would create CMYK-only PDF/X-3 is silly because that’s not what it was designed for, whereas it’s inherent in PDF/X-1a. There is no advantage to a CMYK-only PDF/X-3 document, even though it can be done, and the disadvantage is that it’s potentially a source of confusion.
PDF/X-1a is not “for the U.S.” and PDF/X-3 is not “for Europe.” That the two markets have different ideas about color management and printing implies that PDF/X-3 will be more popular in Europe, but there are markets for which PDF/X-3 would be well suited in the U.S. This includes large format printing, which has essentially no standard print condition at all, and digital presses. The latter have excellent register but with generally poor adherence to SWOP even though they like to claim so, and hence are good candidates for implementing a PDF/X-3 workflow.
In subsequent sections of this chapter, you’ll find that specifying per-object ICC profiles isn’t for the faint of heart, and requires special workflow and software considerations. Once you have a PDF/X-3 document, printing or proofing it requires both faith and courage. You’ll need to use products that specifically support PDF/X-3 documents to effectively proof and output them.
Distiller 5
Adobe Distiller isn’t the only product capable of converting PostScript into PDF, but it’s one of the most common, and it serves well as an example application—just look for similar features and settings in the application you use.
Compatibility
We previously mentioned the various versions of PDF. Distiller’s Job Options dialog box is one of the places where they’re directly relevant to color management. The Compatibility pop-up menu in the General tab of Job Options affects the options available in the Color tab. If you select “Acrobat 3.0 (PDF 1.2),” your only color management policy options are to leave colors unchanged or to convert them. Since PDF 1.2 doesn’t support ICC profiles, there’s no way to simply tag the documents. Unless you have good reasons to do otherwise, we recommend choosing “Acrobat 4.0 (PDF 1.3),” because that’s what PDF/X is based on (see Figure 16-1).
Figure 16-1 Acrobat Distiller 5.0 Compatibility settings
Color Settings
The Adobe Color Settings for Distiller, which you’ll find under the Color tab of Job Options, look like those for other Adobe applications—but the similarity is misleading, because their behavior is unlike those other Adobe applications (see Figure 16-2).
Figure 16-2 Acrobat Distiller 5.0 Color Settings
Settings File
Distiller uses .csf files created in other Adobe applications, and displays them in the Settings File pop-up menu, but it can’t create them itself. When you choose a setting from the Settings File menu, the Color Management Policies menu is grayed out—the only way to enable Color Management Policies is to select the settings file called “None.”
Possibly the best way to handle this is simply not to worry about creating settings files for Distiller, since Distiller has such unusual color behavior anyway. If you save a .joboptions file, any custom color settings are saved as well.
Color Management Policies
The color management policies in Distiller are quite different than in any other Adobe application, by necessity, since Distiller’s job is to convert PostScript into PDF. Other Adobe applications open and display files, then let you edit them in some fashion. Distiller is just a completely different beast, and has policies to match.
• Leave Color Unchanged—this means preserve the numeric values in the PostScript file when converting it into a PDF. Ignore any CSAs in the PostScript file, and don’t embed the Working Space profiles.
• Tag Everything for Color Mgmt (no conversion)—also means preserve the numeric values in the PostScript file when converting it into a PDF. CSAs associated with objects are converted into per-object ICC profiles. The selected Working Space profiles are embedded, and apply to all other objects. All objects are considered tagged.
• Tag Only Images for Color Mgmt (no conversion)—means the same as tagging everything, except that only images are tagged. So vector objects, including text, are untagged, and considered device-dependent.
• Convert All Colors to sRGB—any CSAs associated with objects are used as source profiles. Objects with no CSAs take the Working Space profiles as assumed sources. The destination profile is sRGB, so everything is converted to sRGB.
A brief note on the Intent pop-up. Rendering intents are chosen at the time of PDF creation, just as in PostScript, which seems backwards—we generally find that we can’t tell which rendering intent will work best for a given object until we know the output destination. But that’s the way it currently works.
The Default option is unclear—it’s either the default PDF rendering intent (relative colorimetric), or it’s the intent, set in the PostScript file, that points to the CRD that would have been used had the PostScript file been interpreted by a PostScript RIP rather than by Distiller. We suggest setting it to relative colorimetric—then you at least know what you’re dealing with.
Working Spaces
The Working Space profiles are the ones that are used for tagging, depending on the color management policy selected.
For example, if your document contains a mix of RGB, CMYK and grayscale images, and you print a PostScript file, then distill with one of the “Tag for Color Management” color management policies, a single copy of each working space is embedded in the PDF document. The RGB Working Space profile becomes the source profile for all RGB images, the CMYK Working Space profile becomes the source profile for all CMYK images, and the Gray Working Space profile becomes the source profile for all grayscale images. Whether these embedded profiles apply to non-image objects depends on which color management policy you selected.
The key thing to note is that “Working Spaces” in Distiller really means the profiles that are embedded into the document. They start out as assumed profiles and become embedded profiles in the PDF.
Any objects in the PostScript stream that have CSAs associated with them don’t use the Working Space profiles, but have their CSAs converted into ICC profiles which are embedded into the PDF along with the Working Space profiles. CSAs are the only mechanism that allows Distiller to specify profiles on a per-object basis. Distiller also ignores embedded ICC profiles in the PostScript print stream (which usually appear only when you print a document containing an EPS file with an embedded ICC profile).
Device-Dependent Data
As the name implies, these settings only affect device-dependent data, and prior to PDF generation typically only apply to EPS files, since the options are all based on PostScript functions. With the possible exception of overprint settings, ICC-based objects aren’t affected by these options.
It’s generally a good idea to preserve overprint settings. If they exist in the PostScript file, they have to be preserved in the PDF file if you want the document to print the way the originating application intended.
“Preserve Under Color Removal and Black Generation” exists mainly for legacy support. If your images have already been separated to CMYK, then placed into a page-layout application, and output to PostScript, the images are “press-ready” so PostScript UCR or GCR functions shouldn’t exist to begin with, and preserving them is moot.
Remove transfer functions unless you really know what you’re doing, and have a specific reason for using them. Since a PDF could end up being printed anywhere, it’s almost always best to remove them—it’s usually counterproductive to use them on other people’s equipment.
Unless you explicitly want an element to override RIP settings because you placed an EPS with specific halftone screens in your page-layout software, you usually want to remove halftone information too.
Making PDFs
Three main factors affect your ability to make decent PDFs whether you intend to use them for the Web, soft proofing, or final output (plain PDF, PDF/X-1a, or PDF/X-3):
• Proper preparation of all support files in their respective applications, especially the final application you use to print the PostScript file that Distiller will process. This includes page settings, font embedding, image preparation and linking, and so forth.
• Use of an appropriate PPD file for your PostScript printer driver (which includes making the application you’re printing from aware of the PPD—something that may or may not happen automatically).
• Use of appropriate settings in Distiller, paying special attention to the color settings.
Output-only PDF—press
As previously mentioned, there are many resources on how to make good PDFs, so we’ll stay focused on the color aspects. We’ve already discussed the first of the three factors mentioned above in the earlier application chapters.
The second and third factors mentioned above are workflow-specific, but very important. We’ve come to trust and recommend as a starting point the DDAP PPD, and their accompanying Distiller Settings Files, which are available for both platforms at www.ddap.org/tools/univppd/.
Note that the Distiller Settings File turns color management off, so you’ll end up with a device-dependent PDF. This works as long as you produce output-ready PostScript prior to building the PDF. The resulting PDF won’t have automatic soft-proofing or hard-proofing capabilities, since there’s no source profile embedded in the document. (If you refer back to Figure 16-2, you’ll see that it’s based on the DDAPOptimizedv5 settings file for Distiller 5. Colors are left unchanged and untagged.)
From here, you can feed the PDF to an application such as Apago PDF/X-1 Checkup, or Enfocus Certified PDF (part of PitStop Pro and Server, and Instant PDF), which preflights the PDF, fixes problems it can fix, and makes a note of those it can’t. Assuming everything can be fixed, you end up with a PDF/X-1a document.
Color-managed PDF—desktop
This is a PDF that has profiles associated for all objects. While it’s possible to produce a PDF that has profiles associated with some objects and not others, we recommend you avoid doing so unless you enjoy lessons in frustration.
Using Distiller, we recommend producing an “output-ready” PDF in your page layout application, as previously described in “Output-only PDF—press,” only embedding the final output device’s profile. Since all the color is already converted for one kind of output device, you can describe it all with a single device profile. Embed that profile, and Acrobat 5 and Acrobat Reader 5 use it automatically for on-screen preview, while other applications that can read color-managed PDFs may be able to repurpose the content for some other device (such as for proofing—see Figure 16-3).
Figure 16-3 Adobe Distiller Settings: color-managed PDF
Be careful: as configured in Figure 16-3, Distiller won’t convert anything in the document, so you must make sure that all the color is already converted for output before you feed it to Distiller. Distiller is just being used to tag objects with a source profile (and of course make a PDF file).
Also, while you can effectively use such a PDF for soft and hard proofing, it isn’t necessarily repurposable—since all objects, including black-only text, become device-independent, they won’t be black-only if repurposed.
The real problem is that Distiller’s options don’t really offer enough flexibility. If you choose “Tag Only Images,” non-image objects will only print correctly to the intended destination and will look wrong everywhere else, whereas if you choose “Tag Everything For Color Mgmt (no conversion)” and print to a destination other than the intended one, black text gets converted to rich black, which can create major problems.
PDF/X-3 addresses the problem by letting you define black text as device-dependent, so that it will print as black-only on any destination device, while tagging all objects that need color management to produce the correct appearance.
Color-managed PDF—Internet
The suggestions in the previous two sections generally provide the best results. But if you want to create the smallest possible files, and have the color display reasonably well on the random collection of uncalibrated monitors that serve as the delivery system for the Internet, you may want to try these settings instead.
In Job Options, Color tab, change the Settings File to None—the Web Graphics Default color settings file is useless with Adobe Distiller. Next, set the Color Management Policies to “Convert All Colors to sRGB.” Finally, set whatever output profile you used to create the PostScript as the working space—if your document is entirely Adobe RGB (1998), for example, set that as the RGB Working Space so that Distiller uses it as the source profile when it converts everything to sRGB. Likewise if your document is CMYK, set the working space to the CMYK profile you used as the destination when you created the PostScript file (see Figure 16-4).
Figure 16-4 Adobe Distiller settings: Convert to sRGB PDF
Acrobat 5
Compared to Adobe’s other applications, Acrobat 5’s color management capabilities are just as funky as Distiller’s. While the Color Management Preferences dialog box looks familiar, its scope is limited compared to the other applications, and printing from Acrobat makes us wonder what in the world Adobe was thinking.
The redeeming feature of Acrobat is that color management really just happens without any configuration. Acrobat grabs the display profile automatically from the operating system, and uses embedded profiles automatically and seamlessly, regardless of the color management preferences. Setting up remote soft proofing is as simple as calibrating and profiling a monitor and installing Acrobat on the client side. (On the “server” side, of course, someone needs to embed the correct profiles into the PDFs.)
Color Management Preferences
To open Acrobat’s Color Management Preferences click on “Color Management” in the list on the left of the General Preferences dialog box (see Figure 16-5). Like Distiller, Acrobat can use Color Settings files created in other Adobe applications as well, but it can’t create them itself. Since Acrobat always uses either an embedded or assumed source profile, color management is always on, even though there’s a “Color Management Off” settings file.
Figure 16-5 Acrobat Color Management Preferences
The Working Spaces are the assumed profiles—they apply to all untagged objects in PDF files. If you set the RGB Working Space to monitor RGB (your display profile), the numbers in untagged RGB images get sent straight to the display, so you’re effectively getting no color management, but everything else gets color managed and there isn’t anything you can do about it.
Embedded profiles are always honored, and thus override the Working Spaces. Therefore, be cautious about what profile you select for the Working Spaces, because they affect untagged objects, which in the PDF world are fairly common. If you set your RGB Working Space to ProPhoto RGB, for example, most RGB content in PDFs will be superbly oversaturated compared to any intent the original producer had for the PDF.
The Conversion Options only affect conversions for Proof Colors (described later) and for printing.
Printing
Source profiles are either embedded in the PDF document, or assumed by Acrobat’s Color Management Preferences, but you need to specify a destination profile. Yet for non-PostScript printers, Adobe has provided absolutely no mechanism for specifying a destination profile or a rendering intent. When you print to a non-PostScript printer, it converts from the source profiles to the display profile.
So when you print to raster printers from Acrobat, you’re best off selecting ColorSync or ICM in the printer driver. We’ve confirmed that Acrobat hands off the display profile to the operating system as the source profile for the data stream at print time. From there, the destination profile is dictated by the printer driver.
When you print to a PostScript printer, the Adobe section of the driver contains an Advanced button that doesn’t appear in non-PostScript printer drivers. Clicking it opens the Print Settings dialog box, with no fewer than seven color-management-related options, not one of which is a rendering intent setting—see Figure 16-6!
Figure 16-6 Acrobat Print Settings (PostScript printer only)
We generally ignore the first three checkboxes regarding halftones, transfer functions and UCR/GCR. If you need to use these features, you know it—if you aren’t sure, only experiment when you have lots of spare time. The same goes for “Apply Overprint Preview” which is useful for forcing Acrobat to render the overprint function if your printer doesn’t support it.
“Print ICC colors as Device colors” produces identical results whether checked or unchecked, so it seems to do nothing. (We’re really unclear on what it would do if it did work—if you don’t want conversions, just select Same As Source as you would in other Adobe applications, instead of a destination profile.)
“Apply Working Color Spaces,” fortunately, does work, but we fail to understand why it’s optional. When it’s checked, Acrobat uses the Working Spaces in Color Management Preferences as source profiles for untagged objects in the conversion to print space. When it’s unchecked, Acrobat uses a hardwired conversion that produces results charitably described as lurid and weird.
Last but not least is the Color Profile pop-up menu. This works like the Print Space pop-up menu in other Adobe applications, but it lacks rendering intent control—maybe someone from the Photoshop team should walk across the hall and have a chat with the color people on the PDF team to try to standardize user interface features and terminology.
Distiller 6
Very little has changed in the way of color management in Distiller 6 compared to version 5.0. Therefore we recommend starting with that section, and then reading this one, which discusses additional features found only in Distiller 6.0
The major change in Distiller 6.0 is that it can create PDF/X-1a and PDF/X-3 documents directly from PostScript. See the new presets in Figure 16-7. PDF/X-1a will likely be the more viable in most workflows because of limitations with Distiller 6’s PDF/X-3 generation. If you need to produce PDF/X-3 documents, check out the section on InDesign CS later in this chapter.
Figure 16-7 Acrobat Distiller 6 presets
When set to produce either of these PDF/X flavors, Distiller 6 internally normalizes a PostScript file to PDF, then it essentially preflights it for PDF/X-1a or PDF/X-3 compliance, and if it passes a PDF is saved. The distinction is important because neither Distiller nor Acrobat has the ability to fix minor problems that might prevent a file from being valid PDF/X-1a or PDF/X-3. For that you’ll need one of the products mentioned later in this chapter.
PDF/X-1a, PDF/X-3
If you intend to make PDF/X-1a from Distiller, hopefully the “PDFX1a” preset is already sufficiently configured for your needs. But chances are many of you will need custom settings, if for no other reason than to set an OutputIntent profile other than “U.S. Web Coated (SWOP) v2” which is the default.
Thus, the main new area of interest in Distiller 6 is found in the PDF/X section of the Adobe PDF Settings dialog, located from the Settings drop-down menu (see Figure 16-8). A major oversight in the user interface is the fact you can apparently select both PDF/X-1a and PDF/X-3 at the same time. Don’t try it, it doesn’t work, and will likely cause aberrant behavior in Distiller that will make you homicidal or suicidal, or both, when you attempt to troubleshoot the ensuing problems. Please select one or the other.
Figure 16-8 Adobe PDF Settings dialog
The remaining area of interest, from a color management perspective, is the selection of the OutputIntent Profile Name. Make sure you have an explicit understanding with the receiver of the file as to what the Output-Intent should be for the job. If they accept PDF/X-1a, they should know what this request is about, and if they don’t it should raise a red flag until you have the contract proof in your hot little hands.
The RegistryName(URL) field defaults to the ICC Web site, since with device-dependent PDF/X including PDF/X-1a, it’s not necessary to embed a full ICC profile as the OutputIntent. Instead you can reference the colorimetric behavior. If the OutputIntent you select is not one of these registered behaviors, you should either provide a valid URL or leave it blank. If you fail to do this, your job won’t be hosed, but technically it won’t be a valid PDF/X-1a file.
It’s technically possible to create PDF/X-3 using Distiller, but we don’t recommend it, for several reasons.
• If the PostScript file contains only CMYK, you’re almost certainly better off creating PDF/X-1a instead. If it contains CMYK and Lab, Distiller can and will create a PDF/X-3.
• If the PostScript file contains RGB, Distiller’s PDF/X-3 preset expects all RGB objects to be tagged with CSAs, and if they aren’t, Distiller will fail to produce a PDF/X-3. Very few applications insert CSAs in the PostScript stream. The one that does so reliably, InDesign CS, has a PDF/X-3 export feature that we recommend using instead of Distiller.
• Instead of relying on the existence of CSAs, you can change the Color Management policy in Distiller to Tag Everything for Color Management. If you tag only images, any RGB objects that remain untagged will then cause PDF/X-3 creation to fail, so that’s a limitation. A bigger one is that everything that’s CMYK in the document will also be tagged, including images you may not want repurposed later. But if your document contains only RGB and LAB content, this could be a viable means of creating PDF/X-3.
• You can set the CMYK Working Space profile to match the OutputIntent profile you select in the PDF/X portion of the dialog. That way, CMYK objects undergo a null transform at output time, and RGB and LAB objects are dutifully converted to CMYK. But that means you’re stuck with that OutputIntent in order to ensure CMYK objects null transform, thereby negating the whole point of PDF/X-3, which is its portability to unknown destinations.
The bottom line is that Distiller’s PDF/X-3 support seems fairly dubious for any serious usage of PDF/X-3. You’ll almost certainly prefer using InDesign CS, which exports PDF/X-3 documents directly, a whole lot more easily, and with far fewer limitations.
Acrobat 6
There are a number of subtle but useful added features in Acrobat 6, but otherwise it behaves very much like Acrobat 5, so we recommend reading both sections to get a complete picture.
Color Management Preferences
The preferences dialog, shown in Figure 16-9, has one new and important addition—the “OutputIntent overrides working spaces” is checked by default. It makes Acrobat use the OutputIntent profile as the assumed source profile for untagged content, for viewing purposes only. It’s the source profile for viewing all content in PDF/X-1a documents, and for viewing untagged objects only in PDF/X-3 documents. It is not used as a source profile when printing, so it is also non-binding.
Figure 16-9 Acrobat 6 Preferences
The one situation in which you might want to uncheck this option is when you receive a PDF in which the specified OutputIntent doesn’t describe the actual output device. You can uncheck the option, and then select the correct profile as the CMYK Working Space. When you click OK, Acrobat updates the display of the PDF to show you how it will print to this different destination. It’s very important to note that this does not remove or change the OutputIntent in the PDF, it simply ignores it in favor of the selected CMYK Working Space.
Proof Setup and Proof Colors
This feature works as in other Adobe applications (see Figure 16-10). For more information see Chapter 12, The Adobe Common Color Architecture. Unfortunately it neither shows nor automatically selects the OutputIntent profile when you open a PDF/X-1a or PDF/X-3 document. Unless you know what the OutputIntent profile is, and have it separately installed, you cannot fully soft proof. See the discussion on Acrobat Preflight for a workaround.
Overprint Preview simulates overprints on-screen, which is important if your document calls for overprints because they’ll look very different on-screen without this option selected compared to how they would be printed on a press. Another useful feature is Separation Preview, which shows CMYK + spot numeric values, with checkboxes to enable or disable viewing each channel. Maybe the next version will also show RGB values.
Preflight
Acrobat 6 incorporates a Preflight tool, which includes a standard complement of configuration sets, to which you can also add your own as you see fit. Preflight is accessed from the Document drop-down menu. See Figure 16-11. The top three useful color management related features here have to do with verification of PDF/X-1a and PDF/X-3, report generation which shows source profiles and OutputIntent, and a feature to extract the OutputIntent profile.
Figure 16-11 Acrobat 6 Preflight: Profiles
Analyze and Report
The easiest way to verify a PDF for PDF/X-1a or PDF/X-3 compliance is to select the conformance level you want from the Preflight list, and click Analyze. Preflight won’t repair problems in PDFs but it will generate both pass/fail and a detailed report on any problems it finds. See Figure 16-12.
Figure 16-12 Acrobat 6 Preflight: Results
You’ll note two different items for PDF/X-3, one which implies only CMYK+spot, and the other that ICC/LAB are acceptable. By definition PDF/X-3 allows for CMYK, spot, ICC-Based, and LAB colors. We recommend using the “ICC/Lab OK” preset for PDF/X-3 verification. Again, if you want CMYK-only plus optional spot color, use PDF/X-1a.
If you have a PDF file that is not PDF/X-1a or PDF/X-3 but should be capable of complying with one of those standards, click the PDF/X... button, which reveals a new dialog. Note the specification pop-up menu at the top. The “Save as PDF/X-1a” or “Save as PDF/X-3” option will first verify, and then if the PDF passes it will convert the file to the selected conformance level. See Figure 16-13.
Figure 16-13 Acrobat 6 Preflight: PDF/X dialog
Extract OutputIntent
The third option in the Preflight:PDF/X dialog is “Extract ICC profile...” This option will extract the OutputIntent profile from a PDF/X-1a or PDF/X-3 document if it was fully embedded in the PDF. You can then install the profile in the correct location, and now you can select it in Proof Setup: Custom for both soft and hard proofing purposes.
Printing
There are two big changes in Acrobat 6’s printing abilities. First, you can now color manage prints using ACE to non-PostScript printers. Second, you can print proofs.
From the print dialog, find the Advanced button and click it to reveal the Advanced Print Setup dialog (see Figure 16-14). In the Advanced Print Setup dialog, ensure that you select Output in the list on the far left.
Figure 16-14 Acrobat 6 Print dialog box, and Advanced Print Setup dialog box
Printer Profile
This functions like the Print Space pop-up menu in other Adobe applications. Select a profile for the printer you will currently be printing to. If you don’t want any color management to occur at print time, select “Same As Source (No Color Management)”.
Apply Working Color Spaces
Although it’s as mysterious in Acrobat 6 as in Acrobat 5, you probably want this selected so that Acrobat will use the Working Spaces as source profiles for any untagged content in your PDFs. If you find a reason to not check this option, we’d like to hear about it.
Apply Proof Settings
Checking this option references back to the profile and other settings selected in Proof Setup: Custom, and lets you do cross rendering. Unfortunately that profile is not listed in the print dialog, as in other Adobe applications. The rendering intent options are affected by the simulation checkboxes in Proof Setup: Custom.
• Relative Colorimetric, with Black Point Compensation—is the default with neither Paper White nor Ink Black checked.
• Relative Colorimetric, no Black Point Compensation—Ink Black is checked.
• Absolute Colorimetric—Paper White is checked (and Ink Black is checked and grayed out).
InDesign CS Export PDF
InDesign CS can export PDFs directly, without the need for Distiller. When it comes to color management, InDesign’s Export PDF capability is pretty good, with a couple of potential pitfalls. It produces fully color-managed PDFs, with or without embedded profiles for every object, or mixed-mode PDFs. It can also create PDF/X-1a and PDF/X-3 documents directly, although there are limitations with its ability to create PDF/X-3, mentioned later in this section.
PDF Export Presets
The PDF Export Presets dialog, which you open by choosing File>PDF Export Presets>Define, lets you create and save presets for making PDFs, and is a real time-saver (see Figure 16-15). We suggest you familiarize yourself with the various PDF settings for two reasons—familiarity with them seems to make all the difference in the world between exporting problematic and problem-free PDFs, and we don’t discuss most of the settings because they don’t pertain to color management.
Figure 16-15 InDesign CS PDF Export Presets dialog box
Screen and eBook
These presets set the Destination Profile to Document RGB on some machines, and Monitor RGB on others. We don’t know why, but the bad news is that in either case “Include ICC Profiles” is not selected so you’re guaranteed to see the color differently on every machine that views the resulting PDF. Create your own preset with a rational destination profile (sRGB?) and include the ICC profile.
PDF/X-1a
This preset works as advertised. Any RGB or LAB content is converted to CMYK using the selected Destination Profile, which is then embedded as the OutputIntent profile.
PDF/X-3
This preset works with the following limitations: your destination is CMYK, and you don’t want any tagged CMYK objects. InDesign produces compliant PDF/X-3 with a CMYK OutputIntent only, and all CMYK objects in the layout are untagged /DeviceCMYK in the resulting PDF. If the document contains placed tagged CMYK images, the tags are ignored and not embedded when making PDF/X-3.
Due to limitations in the Export PDF interface, we recommend you live within these limitations. If you have more sophisticated requirements, use a third-party application such as PitStop Pro to re-tag CMYK objects you want tagged, or to create PDF/X-3 for RGB destinations, and be very brave and even more cautious.
Export PDF
The Export PDF dialog is accessed one of two ways: by choosing File>Export and selectingAdobe PDF as the format, or by choosing a preset from File>PDF Export Presets. We prefer the latter. In the left column is an Advanced option, which is where you’ll find the Color and PDF/X sections (see Figure 16-16).
Figure 16-16 InDesign CS Export PDF dialog box
Color
Color offers three options. Leave Colors Unchanged does exactly that—if you create a document with mixed-mode images and elements, you’ll create a mixed-mode PDF. Selecting either RGB or CMYK enables the Destination Profile pop-up menu, discussed next, and converts all the content in your document to the destination profile.
Destination Profile
Here you select a destination profile for output. If the destination is a press, make sure you select Document CMYK as the destination, which is the default. If you don’t, InDesign will convert everything, tagged and untagged, because it sees the CMYK source profile, Document CMYK, as being different than the Destination Profile.
Include ICC Profiles
This option embeds ICC profiles into the PDF. If you selected Leave Colors Unchanged in the Color pop-up menu, each profile used in the document is embedded in the PDF. If you choose to convert the document to RGB or CMYK, only the destination profile is embedded, since all document content is converted to that destination.
Simulate Overprint
This option does two things. It makes InDesign do the overprint itself before producing the PDF, which is useful for making dual-purpose PDFs for screen and print because many consumer devices—and even some PostScript RIPs—have no idea what overprinting is. But it also converts spot colors to process, so it’s not an option you want to use when preparing PDFs for press—use the Ink Manager instead.
Ink Manager
The Ink Manager can perform a variety of functions, which are described in the InDesign User Guide. If you make changes here, they affect the exported PDF, not your InDesign document. Be careful with these settings if you rely on InDesign to perform trapping, because some of them are used by InDesign’s trapping engine.
If you select the option to convert all spot colors to process, they’re converted using the CMYK equivalents supplied by Pantone in whichever Pantone library you used to specify the spots. They aren’t converted using ICC-based color management, so your process Pantone colors probably won’t look right unless you’re really lucky.
PDF/X Output Intent Profile
Ensure you select a profile for the intended output conditions with this pop-up menu. With the PDF/X-1a preset, this will snap to match the Destination Profile, and vice versa. Unfortunately, even though PDF/X-3 allows RGB OutputIntents, InDesign CS does not.
EPS, PDF, and AI Formats
InDesign CS will color-manage EPSs containing either PostScript CSAs or ICC profiles. It uses either for on-screen preview, as well as for outputting PostScript and exporting PDF. InDesign assume Document profiles as the source profile for untagged EPS, which means if the Destination Profile is something other than Document CMYK, untagged CMYK EPS will be converted.
Placing PDF or AI formatted files into an InDesign document follows similar rules. Keep in mind PDF is a container format, so it can contain multiple objects with different source profiles, as well as untagged objects. The untagged objects inherit the Document profiles. The only ways to prevent objects from being converted during PDF export are
• Select Leave Colors Unchanged.
• Make sure that the Document Profile (the assumed source for untagged objects) and the Destination Profile you select in Export PDF are the same.
Because of the complexities of these formats, and the simplicity of the InDesign Image Color Settings interface, it is not possible to change the source profiles, either assumed or embedded, or per-object rendering intents from within InDesign. Therefore, Image Color Settings is grayed out when placing EPS, PDF, and AI (Adobe Illustrator) documents.
Third-Party Stuff
There are a number of really good products on the market, but the one we’ve worked with the most, and hence can discuss with some authority, is Enfocus PitStop Pro 5 for Acrobat 5, and version 6 for Acrobat 6.
Enfocus PitStop Pro
This plug-in for Acrobat lets you do all kinds of manipulation and editing on PDFs, but we’ll only look at the ones that are color-management related. Consider it one of the necessary tools in the arsenal if you’re a heavy PDF user. (Or for high-volume workflows, consider the industrial-strength PitStop Server—for more information, go to www.enfocus.com.)
PitStop Pro strengths
PitStop Pro offers the following useful capabilities for creating and massaging color-managed PDFs:
• It distinguishes between device-dependent (RGB, CMYK, Gray) and LAB and ICC-Based color spaces on a per-object basis.
• It lists the embedded profile associated with each object.
• It lets you untag objects, reassign profiles to objects, and embed profiles on saving the PDF.
• It lets you specify a destination profile to which any object can be converted. It supports RGB-to-CMYK, CMYK-to-RGB, and RGB- or CMYK-to-grayscale conversions using ICC profiles.
• It lets you do any of the above object by object, or globally.
• It preflights and produces certified PDF/X-1a, and PDF/X-3 documents with a preflight report, and tracks changes to the PDF as it moves through production.
• It offers downloadable “PDF Profiles” that extend its ability to preflight PDFs for other target viewers, such as the Internet.
PitStop Pro weaknesses
However, it isn’t perfect, and has the following weaknesses:
• It offers no rendering intent control for conversions, which use the destination profile’s default rendering intent.
• It doesn’t directly support RGB-to-RGB or CMYK-to-CMYK conversions, though you can work around the limitation by first converting an object into LAB as an intermediary space.
• It doesn’t support DeviceLink profiles.
Other Products
We haven’t worked with these products as much as we have with PitStop Pro, but they come recommended by people whose judgment we trust:
• Apago PDF/X Checkup, www.apago.com
• Callas PDF/X Inspektor (free), and PDF Inspektor, www.callas.de/
• Dalim TWiST and SWiNG, www.dalim.com
• OneVision (various products), www.onevision.com
The Wave of the Future
If, as we suspect, print publishing will be forced by brute economics to make the transition from arcane craft to modern manufacturing process, it seems likely that PDF workflows, whether based on the current PDF/X standards or on ones that don’t yet exist, will become prevalent. But while unambiguous communication of documents between creator and producer will ultimately benefit both sides, note that the shift from delivering application files, fonts, and linked graphics to delivering a print-ready PDF/X-1a involves a shift of responsibility back to the content creator.
In some ways, PDF/X is a 21st-century equivalent of the PostScript dumps Bruce used to send to service bureaus in the mid-1980s—when things went wrong, the blame was always his. PDF workflows hold huge promise, but they’re still experimental, and you can always spot the pioneers by the arrows protruding from their backs—so if you’re considering PDF workflows, take it one step at a time, test thoroughly, and don’t attempt untried procedures when you’re facing critical deadlines.