Calibrating Color

InDesign comes with several color management system (CMS) options. A CMS helps you ensure accurate printing of your colors, both those in imported images and those defined in InDesign. What a CMS does is track the colors in the source image, the colors displayable by your monitor, and the colors printable by your printer. If the monitor or printer does not support a color in your document, the CMS alters (recalibrates) the color to its closest possible equivalent.

To activate a CMS, make sure color management is enabled in your document. Do so by using Edit ‚ Color Settings to get the dialog box shown in Figure 29-1. Be sure Enable Color Management is checked. (I'll get to the other options a bit later in this chapter.)

Figure 29-1: The Color Settings dialog box lets you activate color calibration and set document defaults.

Note ‚

Don't confuse InDesign's CMS capabilities with color matching. It is impossible to match colors produced in an illustration or paint program, or via a scanner, with what a printer or other output device can produce. The underlying differences in color models (which actually determine how a color is defined) and the physics of the media (screen phosphors that emit light versus different types of papers with different types of inks that reflect light) make color matching impossible . But a calibration tool like a CMS can minimize differences.

Setting up your system

To achieve the best reproduction of printed colors on-screen, you need a closely controlled environment for your computer. Most people don't bother, relying instead on their brain's ability to mentally substitute the print color for what they see on-screen after they've had experience seeing what happens in actual printed documents. But the more you do to control the color viewing environment, the closer the match between what you see on-screen and what you see on the page.

These tips on setting up your system are in order from simplest to most complex:

Dim the lights. Most people turn the brightness of their monitors too high, which distorts colors by overdoing the blues and underdelivering on the reds. Turn the brightness lower, to between 60 and 75 percent maximum. To make sure you can still see the screen, lower the amount of light in your workspace by using lower-wattage bulbs , turning off overhead lighting right above your monitor, and/or using translucent shades in nearby windows .
Change the color temperature of your monitor to 7,200 degrees on the Kelvin scale. Most monitors have on-screen controls to do so.
If your monitor came with a color profile, use it. On the Mac, the Displays control panel has an option in the Color pane for setting color to a profile (stored in the System\Library\ColorSync\Profiles folder), or you can use the ColorSync control panel to set profiles for several devices. In Windows, use the Display control panel; the Settings pane has an option called Advanced that will open a dialog box that has a Color Management pane. The profiles are stored in the Windows\System\Color folder. Some monitors or video cards come with their own color-setup software.
Use a calibration tool. Tools such as Monaco Systems' Monaco Sensor or X-Rite's Monitor Optimizer calibrate your monitor and create a color profile specifically for it. These calibrators cost $375 to $600, so they're typically purchased by graphics departments, not individual designers. Note that color calibration software without a hardware calibrator device is worthless ‚ without being able to measure what colors actually come from your monitor, there's no way they can meaningfully adjust the colors your display shows. Also note that monitors vary their color display over their lifetime (they get dimmer), so you should recalibrate every six months. For most users, the variances in monitor brightness, color balance, and contrast ‚ coupled with the varying types of lighting used in their workspace ‚ mean that true calibration is impossible for images created on-screen and displayed on-screen. Still, using the calibration feature will make the on-screen color closer to what you'll print, even if it's not an exact match.
Work in a color-controlled room. In such a room, the lighting is at 5,000 degrees Kelvin, so the light reflecting off your color proofs matches that of a professional prepress operation. (There's long been a standard, the latest version of which is called ISO 3664, that has set 5,000 degrees Kelvin as the industry standard for proofing color printing. Basically, 5,000 degrees is filtered daylight where the red, green, and blue components are equal. The International Prepress Association [ www.ipa.org ] has a lot of standards information and resources related to color accuracy.) Monitors should also be set with a white point of D65 (something done with calibration hardware and software). Also try to buy monitors with a neutral, light gray shade ‚ or paint them that way ‚ so your brain doesn't darken what you see on-screen to compensate for the off-white monitor frame right next to the screen image. Similarly, all furnishings should be neutral, preferably a light gray. Avoid having anything with a strong color in the room ‚ even clothes.

Defining color models

Whether you define colors in InDesign or in your illustration or paint program, the method you use to define them is critical to ensuring the best possible output. Defining all colors in the same model as the target output device is best. Use the following guidelines:

If your printer is RGB (this is rare), use the RGB model to define colors.
If your printer is CMYK (like an offset printer or most ink- jets ), use CMYK to define colors.
If you're using Pantone colors for traditional offset printing, pick one of the Pantone solid models if using Pantone inks. Pick the Pantone Process Coated model if your printer is using inks from companies other than Pantone.
If you're using Pantone colors for traditional offset printing, pick the Pantone Process Coated model if you will color-separate those colors into CMYK.
Trumatch and Focoltone colors were designed to reproduce accurately whether output as spot colors or color-separated into CMYK. Other models (such as Toyo and DIC) may or may not separate accurately for all colors, so check with your printer or the ink manufacturer.
If you're using any Pantone, Focoltone, Trumatch, Toyo, or DIC color and outputting to a desktop color printer (whether RGB or CMYK), watch to ensure that the color definition doesn't lie outside the printer's gamut , as explained in the next section.
Never rely on the screen display to gauge any non-RGB color. Even with the InDesign CMS's monitor calibration, RGB monitors simply cannot match most non-RGB colors. Use the on-screen colors only as a guide, and rely instead on a color swatchbook from your printer or the color ink's manufacturer.
InDesign's CMS does not calibrate color in EPS or PDF files. If you use EPS, I strongly recommend that you use the DCS (pre-separated CMYK) variant. If you use PDF files, embed the correct color profile in the application that you created the PDF file from or by using Adobe Acrobat Distiller's options to set color profiles.

Adjusting on-screen display

Here's how InDesign's CMS works in practice:

To have color calibration in effect for a monitor, you must be displaying thousands of colors (16-bit color depth) or more colors (or a higher color depth, such as 24-bit). On the Mac, use the Displays control panel to change your monitor's bit depth. In Windows, use the Display control panel.
Select the monitor or color space in the RGB pop-up menu in the Working Spaces section of the Color Setting pane (refer to Figure 29-1). The monitor or color space that you select will tell InDesign how to display imported images and colors defined within InDesign. The first four options ‚ Adobe RGB (1998), Apple RGB, ColorMatch RGB, and sRGB IEC61966-2.1 ‚ are all "neutral" color spaces, meaning that they aren't adjusted for specific monitors. Adobe program typically save their images with the sRGB profile, which works well if you define colors based on swatches and use exact RGB settings or existing swatches. The other options are monitor-specific profiles, which make sense to use if you choose your colors based on what you see on-screen.
Select the output devices in the CMK pop-up menu in the Working Space section. This is only for the imaging device used at your prepress bureau to create the actual color separations (covered in more detail later in this chapter). If you're outputting to PDF files for on-screen display, choose a neutral option in the RGB pop-up menu instead of a monitor-specific option.
Set the color management of imported images in the Color Management Policies section of the dialog box. In the RGB and CMYK pop-up menus , you can select a color profile to apply to each imported or pasted picture ‚ these will override any embedded profiles in the pictures. The default option in both cases is Preserve Embedded Profiles, which is the best option if your graphics sources have already had color models applied intentionally to help calibrate the output. If your pictures are not usually color-managed at the source, it's best to override them and choose either Convert to Working Space, which uses the color profiles selected in the Working Space section of the dialog box, or Off, which strips out any color profiles. There are also two options on when to notify you of profile mismatches ‚ Ask When Opening and Ask When Pasting ‚ as well as one to alert you to pictures without a profile (Ask When Opening). You should check all three; one exception is that if you have chosen Convert to Working Space in the RGB and CMYK pop-up menus, you can uncheck Ask When Opening for Missing Profiles, since you won't be using any embedded profiles from the original picture.

Use the Conversion Options section to control the display and printing of bitmapped images. (Make sure the Advanced check box option is selected to display this section.) The Engine pop-up menu lets you choose the CMS technology to use, while Intent determines how colors are adjusted by the selected engine. You have four options in the Intent pop-up menu, as well as a related check box:

Platform Difference ‚

In the Engine pop-up menu, the list of available CMSs depends on what platform you're using: The Adobe ACE CMS is available for all platforms, while the Apple ColorSync and Apple CMM CMSs are available just for Macintosh, and Microsoft ICM CMS is available just for Windows. Choose a CMS that is compatible with your output equipment; if in doubt, choose Adobe ACE.

Perceptual tries to balance the colors in an image when translating from the original color range to the output device's color range under the assumption that it's a photograph and, thus, needs to look natural. This is appropriate for photographs.
Saturation tries to create vivid colors when translating from the original color range to the output device's color range ‚ even if doing so means some colors are printed inaccurately. This is appropriate for charts and other slide-like graphics whose colors are intended for impact rather than naturalness.
Relative Colorimetric is the same as Absolute Colorimetric except that it will shift all the colors to compensate for the white point of the monitor as set in the Monitor profile ( essentially , adjusting the brightness of the output to compensate for any dimness or excess brightness in the monitor).
Absolute Colorimetric makes no adjustments to the colors during output. So it allows, for example, an image that uses two similar colors to end up being output as the same color because of the printer's limited color range.
Use Black Point Compensation adjusts the color range for maximum range, permitting truer colors in most cases and a more natural look to converted photographs. You should leave this checked, unless you know your source image has a small range (such as being mostly midtones), in which case black-point compensation can distort shadows and subtle colors in an effect similar to a moir ƒ pattern.

Tip ‚

Depending on what kinds of documents you produce, you'll likely want Perceptual or Saturation as your setting.

QuarkXPress User ‚

InDesign and QuarkXPress have comparable color-calibration features, but there are some differences: QuarkXPress does not let you apply black-point compensation. And InDesign lets you save your color-management preferences for use in other documents.

Using calibrations from other programs

Other programs may have similar settings for calibrating their display against your type of monitor. For example, Adobe Photoshop offers such an option (via Photoshop ‚ Color Settings on the Mac and Edit ‚ Color Settings in Windows); it's similar to the InDesign Color Settings dialog box. If you're creating colors in a program and importing those colors into InDesign, it's important to have them calibrated the same way, or at least as closely as the different programs will allow.

Understanding profiles

The mechanism that a color management system (CMS) uses to do its calibration is the profile that contains the information on color models and ranges supported by a particular creator (such as an illustration program or scanner), display, and printer. InDesign includes dozens of such predefined profiles.

A CMS uses a device-independent color space to match these profiles against each other. A color space is a mathematical way of describing the relationships among colors. By using a device-independent color model (the CIE XYZ standard defined by the Commission Internationale de l' ƒ °clairage, the International Commission on Illumination), a CMS can compare gamuts from other device-dependent models (like RGB and the others). What this means is that a CMS can examine the colors in your imported images and defined colors, compare them against the capabilities of your monitor and printer, and adjust the colors for the closest possible display and printing.

Calibrating imported colors

When you load an image into InDesign, the active CMS applies the default settings defined in the Color Settings dialog box. But you can change those settings for specific images as follows :

As you import each file, check Show Import Options when you place a graphic into InDesign in the Place dialog box (File ‚ Place, or z +D or Ctrl+D). In the resulting dialog box, go to the Color pane and select the appropriate profile from the Profile menu, as well as the appropriate rendering intent from the Intent pop-up menu. Figure 29-2 shows the dialog box.

Figure 29-2: You can apply color profiles when importing pictures.

Any time after you place a graphic, select it with a selection tool and choose Object ‚ Image Color Settings to set a new profile and/or rendering intent. You can also turn off color management for this object. Figure 29-3 shows the dialog box.

Figure 29-3: You can apply color profiles to an object after it's placed in your document.

Note ‚

Only profiles appropriate for the image type will appear in these pop-up menus ‚ for example, only CMYK profiles ( generally , these are output devices) will appear for a CMYK TIFF file, even though the image may have been scanned in from an RGB scanner and later converted to CMYK with Photoshop. This limitation exists because InDesign assumes that the image is designed for output to that specific printer and, thus, will calibrate it with that target in mind. For RGB files, InDesign lets you apply monitor-oriented profiles and scanner-oriented profiles.

Saving color-management preferences

You can save and use color-management settings in other documents. The process is simple: Use the Save button in the Color Settings dialog box to save the current dialog box's settings to a file. If you want to use that saved color-settings information in another document, open that document and click the Load button in the Color Settings dialog box, then browse for and select the color-settings file. That's it! This is a handy way to ensure consistency in a workgroup.

Changing document color settings

If you put together a document with specific color settings, as described earlier, but then decide you want to apply a new profile across your pictures or replace a specific profile globally in your document, you can.

Choose Edit ‚ Assign Profiles to replace the color management settings globally, as Figure 29-4 shows. You can set the RGB profile and CMYK profiles separately, as well as set the color intent for solid colors, bitmap images, and gradient blends using the Solid Color Intent, Default Image Intent, and After-Blending Intent pop-up menus.

Figure 29-4: InDesign provides two dialog boxes ‚ Assign Profiles (top) and Convert to Profile ‚ to change color-management preferences throughout a document. While their functions overlap, each has unique settings.

Similarly, you can change the document's color workspace by choosing Edit ‚ Convert to Profile, which opens the Convert to Profile dialog box also shown in Figure 29-4. It also lets you change the CMS engine, rendering intent, and black-point compensation settings.

There's real overlap in these two dialog boxes. Using the Assign Profiles dialog box to replace the document profile does the same as the Convert to Profile dialog box when it comes to replacing the profiles. The only difference there is that the Assign Profiles dialog box can also remove profiles from the document. Both dialog boxes let you change the rendering intents for colors, though the Assign Profile dialog box gives you several levels of control not available in the Convert to Profile dialog box. But the Convert to Profile dialog box lets you change the black-point compensation and the CMS engine. These really could be combined into one dialog box.

Calibrating output

When you're ready to output your document to a printer or other device, you set the profile and rendering intent for that destination device in the Color Management pane of the Print dialog box (File ‚ Print, or z +P or Ctrl+P), which has a Print Space section with a Profile pop-up menu and an Intent pop-up menu. Here you select the appropriate options for your output device. Chapter 31 cover printing in more detail.