The Engine field chooses the color management engine. By default, this is Adobe’s ACE (Adobe Color Engine), but you will have a couple of additional options. On Windows, you’ll also see the
Microsoft ICM, and on Mac the Apple CMM and Apply ColorSync. There isn’t much difference between them. They’re all based on specs from the International Color Consortium, in which Adobe’s ACE developers hold the highest seats. Stick with the ACE.
The Intent drop-down box is for rendering intent—through what process, using which relational choices, should a color outside the gamut be brought into gamut for printing. There are four options:
Perceptual This rendering intent tries to maintain smooth tonal transitions between colors, even altering colors as needed, and is usually best for photographic imagery, although relative colorimetric is better nearly as often.
Saturation Most often used for business graphics or illustrations where vibrancy is more important than hue, the saturation rendering intent maps out-of-gamut colors to in-gamut colors by striving to maintain saturation values even if hues must be shifted.
Relative Colorimetric In this rendering intent, the white points of both the source gamut and the destination gamuts are aligned, and then out-of-gamut colors are scaled in gamut relative to their distance from the white point. Although some tonal variances are lost, relative colorimetric is the best of the four for maintaining color accuracy and should be considered the default rendering intent for most work.
Absolute Colorimetric As the name implies, this rendering intent maps colors to their absolute locations in the source and destination gamuts. Colors that are in gamut remain unchanged, while out-of-gamut colors are clipped to the nearest in-gamut color (along the outer edges of the gamut). Absolute Colorimetric often creates a posterization effect in images with many out-of-gamut colors or subtle tones. The advantage to this rendering intent is its ability to simulate the effects of substrate colors on ink.
Each rendering intent has its own typical uses, but do experiment with them. Rules of thumb are better in most situations, but every design is different, with its own unique considerations. Moreover, the document rendering intent is to account for objects created natively in InDesign and the majority of images. Each image can be assigned its own rendering intent individually, so you
can fine-tune any for which the overall rendering intent is not ideal.
Use Black Point Compensation
Usually better left on, this option maps the pure black of the source profile (or working space) to the pure black of the destination profile (output device). For example, let’s say you’re employing printer and substrate combination that, after 92% gray, everything goes to pure black—the values are said to be plugged. Similarly, the whites get blowout below 14% gray. (Both of these are fairly common with low- to mid-count linescreens or highly absorbent paper like newsprint.) A press or pre-press operator knows about these limitations with equipment and will build them into the device and substrate-specific ICC profile. That profile will then tell InDesign that it doesn’t have a full range in which to set black tones, that it only really has 78%. With Black Point Compensation checked, InDesign will reset the value of pure black to 92% black—the point at which the ink will plug up to become full black—and adjust the white point to 14%. All the values in between will shift slightly to maintain smooth transitions. In that scenario, for example, 50% gray input will shift up slightly to maybe 52 to 56% so that it stays as the midpoint between black and white, preserving tonal range.
If you modify the color settings in one application, the legend at the top of the dialog will alert you that the others in Creative Suite (assuming you have them) are out of synchronization. To ensure consistent color between InDesign, Photoshop, Illustrator, and Acrobat, you should mirror your settings from one to the rest. In the first three, you’ll find this dialog in the same place—Edit ➢ Color Settings—and in Acrobat on the Color Management pane of its Preferences (Cmd+K/Ctrl+K). Note that Photoshop has additional controls in its Color Settings dialog, primarily dealing with gamma and spot control, while Acrobat has fewer controls than InDesign.
Per-Image Color Management
As noted earlier, each image placed, pasted, or dropped into InDesign can have its own output color profile and rendering intent. They can come in that way or be changed once in the document. Moreover, changes to an image profile within InDesign only change its output from InDesign; they do not alter the original asset on disk. To change an image profile and/or rendering intent, with an image selected, choose Object ➢ Image Color Settings or Graphics ➢ Image Color Settings from the context sensitive menu to access the Image Color Settings dialog (see Figure 10.5). These are the same controls you access when placing color-managed image files with Show Import Options checked.
Changing Color Profiles
In Color Settings (or Bridge’s Suite Color Settings), you define the color management options for the InDesign application and any new documents created while those options are in effect. What
you do in there, however, will not alter color management options on existing documents. To alter the working spaces, rendering intents, and so on you need Assign Profiles or Convert to Profile, which are both found on the Edit menu below Color Settings. The difference between assigning and converting profiles is a tricky, hair-thin line.
Remove or Assign Document Profiles
Assign Profiles (see Figure 10.6) first lets you strip off any profiles assigned to the document, including those previously assigned through this dialog, added via Convert to Profile, or in effect as the working spaces at document creation time. When you discard profiles, be careful: They will probably look fine onscreen because they’ll use the current Color Settings working spaces and rendering intents while the document is opened, but the document itself will not carry those profiles with it to press or someone else’s computer. When you assign the current working space (below the Discard radio buttons) or assign another profile from the drop-down menus, the RGB and CMYK color definitions will remain unchanged, although they will appear different onscreen. Assigning a profile doesn’t remap colors with a rendering intent; it effectively tells InDesign that the colors were wrong to begin with, that these are what they should have been.
Although the ability to both discard and assign new profiles is frequently useful, what is really cool about Assign Profiles is the bottom three drop-down boxes that let you set rendering by image type. Solid Color Intent defines the rendering intent for vector artwork, either natively drawn or imported somehow (place, paste, drop). Default Image Intent is the default raster or bitmap image rendering intent. Lastly, the confusingly named After-Blending Intent is the rendering intent to apply to objects that interact through transparency. For instance, if one image is overlaid on another and set to the Multiply blending mode, then the two objects will be mapped to in-gamut colors using the rendering intent specified here if different from the intent in Color Settings.
The handy Preview check box lets you see the results of your changes with the ability to hit cancel and revert to the pre–Assign Profiles state.
Convert to Profile
Converting a profile is the opposite of assigning a profile. Instead of telling InDesign the colors were off, they should have been this, Convert to Profile (see Figure 10.7) says, The color definitions were right—and they look fine onscreen—but now I need them mapped to this other gamut in this color profile. As the dialog indicates, Convert to Profile fires up the UN translator to convert the document’s speech from the Source Space color language into the Destination Space color language.
When would you use Convert to Profile? A good example is when you have to begin a project ahead of knowing how it will output and on what substrate. In that case, you’d set the document working spaces to large gamut profiles like Adobe RGB (1998) and U.S. Web Coated (SWOP) v2. Later, once you’ve received the correct ICC profile for the printer and substrate, use Convert to Profile to remap the CMYK profile to that particular profile. Just be careful: Every time you convert the document profile, you’re mapping colors between two separate gamuts, causing permanent, possibly destructive changes. Once the document profile is converted, you can almost never go back.