Editor’s Note: In the first of this two-part series, (see Sign Business February 2007, page 72) the author described steps that you need to take to get ready for using printer ICC profiles. These included (1) requesting that customers supply files in RGB mode, not CMYK; (2) making sure all customer-supplied files have embedded standard working space profiles; and (3) optimizing your printer’s ink density, linearization, and total ink coverage.

In this article we will assume that you have invested in a color management system, including a color measurement instrument and profiling program. Or, you are contemplating such an investment and first want to know what the steps are in using it.

STEPS IN PROFILING

Step 1: Select a Target. The first step in profiling is to choose the color target you want to print to make the profile. If you’re using a digital printer with the manufacturer’s free driver, the printer probably prints in RGB mode. This doesn’t mean that the printer uses red, green, and blue inks, but rather that the driver is set up to receive files in RGB mode. If sent CMYK files, the driver will first convert them to RGB, then to separations for the printer’s ink combination (CMYK, CMYKcm, CMYKcmk, and so on). To profile an RGB printer, you must select a color target in RGB mode. This means the color patches are defined in RGB values, on a scale of 0–255, where 0 is dark (no color) and 255 is 100% color.

If your printer has a RIP, it probably prints in CMYK mode. This means the RIP is set up to receive files in CMYK mode. It can also accept RGB files, which it converts to CMYK before output using the ICC profile. To profile a CMYK printer, you’ll need to print a CMYK target. The color patches are defined in CMYK values from 0–100%.

Color targets are available with anywhere from 288–918 RGB patches and 323–1500 CMYK patches. In X-Rite’s (formerly GretagMacbeth’s) ProfileMaker Pro, you can even make custom test charts with up to 10,000 patches! Larger numbers of patches may make the profile subtly smoother, but will take longer to read.

Choose the appropriate target format for your instrument. Some instruments require special formatting, such as gaps or indicator patches.

Step 2: Print the Target. In either case (RGB or CMYK target), print the target with color profiles turned off (see Figure 1). This characterizes the printer’s “raw” color state. If the target is printed with a profile, you’ll be “profiling the profile,” not the printer.

Step 3. Measure the Target. After printing the color target, inspect it for proper ink density, color, and artifacts. Allow the target to dry for a minimum of 30 minutes before measuring.

If you’re not sure how much the color changes over time, measure the target after 30 minutes, one hour, and 24 hours, then compare the values using a color-comparison utility like GretagMacbeth’s MeasureTool or Chromix ColorThink Pro (see Figure 2).

Measure the printed target with your color measurement instrument (see Figure 3). It’s a good idea to save your measurements as a text file, in case you want to use them to build another profile.

For greater precision, you can measure several targets, compare them for similarity, and average them. For example, when profiling an inkjet printer, you could print one target in portrait format and one in landscape, compare the measurements, and average if they are slightly different.

Step 4. Build the Profile. To build the profile, open the measurement file and a reference file describing the target. You will need to select settings program and separation settings in your application (see Profiling Program Settings below).

Save the profile with an extension of .icc (International Color Consortium) or .icm (Windows Integrated Color Management). Profiles are cross-platform, so either extension will work on a Mac or Windows computer. When naming printer profiles, you may want to include some code indicating the printer, RIP, media, resolution, and date. For example, for an Epson 4800 with the ColorBurst RIP, Epson Proofing Semi-Matte media, and 720-dpi resolution that was made on March 1, you could write “EP4800_CB_EPPrfSM_720_030107.” Try to avoid using names that are too long, as you won’t be able to see the entire name in popup menus.

EVALUATING THE PROFILE
Before using a printer profile in production, it’s a good idea to test it. First, install the profile on your computer. For Macs, put it in the folder Library > ColorSync > Profiles; for Windows, WINNT > System 32 > Spool > Drivers > Color. Open a test photo in Photoshop, and check out the effects of the profile using View > Proof Setup > Custom. Choose your profile from the popup menu, then select View > Proof Colors (if not already selected). Turn “Proof Colors” on and off a few times, checking for color, gradation, and artifacts.

After soft-proofing the profile, print a test photo to your printer using the profile.

USING THE PROFILE

If your printer profile was made for a RIP, follow the manufacturer’s instructions for installing an ICC profile. For use with Mac or Windows applications, install the profile in one of the Mac Profiles folders or the Windows Color folder as described in the “Evaluating the Profile” section above.

Figure 4: To use a printer profile with Photoshop or other ICC-compliant application, select File > Print with Preview, and choose your profile. The application will convert color to match at print time.

To print with your profile from Photoshop or other ICC-compliant application, select File > Print with Preview, and select Color Management. From the Output popup, select Let Photoshop Determine Colors, and choose your profile from the Printer Profile popup (see Figure 4). Photoshop will then convert the image colors to the printer profile upon output.

Profiling Program Settings

We will use X-Rite ProfileMaker 5 to illustrate printer profiling settings that are typical for inkjet printers (see Figure 5).

Figure 5: X-Rite’s ProfileMaker 5 profiling application in Printer profiling mode.

Profile Size (Default/Large)—We recommend using the Large profile size (ca. 2 MB). The Default size (750 K) is for profiles where you want a small file size, e.g., for posting on a Web site or emailing to a customer. The Large profile size will sometimes produce a noticeably smoother profile.

Perceptual Rendering Intent (Paper/Neutral)—Use the Neutral Gray intent for most purposes. This attempts to neutralize any color cast in the paper where there is sufficient dot area to do so. As an example, Paper-colored Gray could be used to retain a buff-colored cast in the media for an artistic effect.

Gamut Mapping (Colorful/Chroma Plus/Classic)—The gamut mapping algorithms from Classic (ProfileMaker 3) to Chroma Plus (ProfileMaker 4) and Colorful (ProfileMaker 5) provide increasing saturation. You may want to try the different algorithms to see which looks best.

Viewing Light Source—The viewing light source is used to make the profile match color under the specified lighting condition. For most applications, choose D50. If you have one of the specific viewing booth brands shown in the pop-up, choose that setting to make color match better in that booth. You can also take a reading of your ambient light with an i1 instrument and i1 Share software, and use the reading in ProfileMaker.

Correct for Optical Brightener—If available for checking, this indicates that ProfileMaker has detected the presence of optical brighteners in the media. These fluorescent dyes make paper look brighter by absorbing invisible UV radiation and re-radiating visible light in the blue region of the spectrum. UV brighteners tend to make profiles look too yellowish. ProfileMaker compensates for UV brighteners if the checkbox is marked.

Separation Settings—The Separation button (available only for CMYK printers) lets you make settings for CMYK-mode printers (see Figure 6).

Predefined—Select Inkjet 400 for most inkjet printers. You can then change the specific settings in the other pop-ups.

Separation—GCR levels of 1, 2, 3, and 4 correspond approximately to 20%, 40%, 60%, and 80% gray-component replacement. Use GCR 3 for most applications. Higher GCR levels replace more of the “gray component” (C+M+Y) with black (K). This can save ink and reduce drying time, but may result in lower shadow densities.

Black Start—This is the percent cyan at which black starts to print (e.g., 40% means that a 1% K dot prints at C = 40%). If you see black speckling in the highlights of your print, raise the black start point. Values as high as 70% may be necessary with coarse droplet-size printers. Lower values can be used with fine-dot printers or those that use a light black ink.

Black Max—This is the maximum black percentage in the reproduction. We recommend setting black to 95% to allow 5% “headroom” to ensure shadow detail. (To enter values, move the slider or enter the desired percentage in the K “Define Black Point” box.)

CMYK Max—This sets the total ink coverage (sum of C+M+Y+K) for the profile. Total ink should be as high as the printer/ink/media allow to ensure dark shadows. If you have reduced ink coverage in your RIP, leave the profile’s total ink coverage at 400% (395% with 95% K). If your RIP doesn’t allow setting total ink coverage, it may be necessary to reduce it in the profile if you notice excessive ink in shadows.

Define Black Point—These values can be used to change the CMYK dot percentages of the black.

Neutralize—Clicking the Neutralize button neutralizes the shadow based on the color readings of the test chart. We recommend not clicking the Neutralize button for most inkjet printers.

Black Width—This setting, introduced in ProfileMaker 4 at the request of gravure printers, affects GCR’s replacement of black in chromatic (saturated) colors. It can also be used in inkjet profiles to reduce black speckling in flesh tones.

(Click here to read Part 1 of this article series.)