When discussing color management, one inevitably talks about the need to calibrate equipment and to obtain ICC profiles, but when a program is implemented all these elements must interact with the RIP. This two-part series examines that interaction.

In Part 1 of this article (July DG, page 56) we looked at using ICC color management profiles to get accurate and consistent color. To use a color-managed workflow, you need to link ICC profiles from beginning to end as source, destination, and (for proofing) simulation profiles. At each color conversion stage, you could select one of the ICC’s four standard rendering intents to handle colors outside of the printer’s gamut — typically relative colorimetric to get the most accurate spot colors and vector graphics, and perceptual for the smoothest photos and blends.

Here, in Part 2, we examine how to actually use those profiles in specific RIPs. Virtually all RIPs in use today are ICC compliant and use color profiles to ensure accurate and consistent output. If you know about source, destination, and simulation profiles, then even if you have never touched the RIP before, you can easily figure out how to set up a color management workflow.

WHAT YOU NEED
In the first half of this article we said that your equipment would vary according to your profiling scenario. Printer profiles are the most difficult to produce. If you planned to use manufacturer-supplied printer profiles, you don’t need to invest in a reflective color measurement instrument and profiling software. However, you’ll probably want an inexpensive monitor calibrator for accurately viewing files and for soft-proofing.
If a media manufacturer doesn’t supply profiles for the printer, RIP, and the settings you want to use, then it may be worthwhile to invest in a printer profiling instrument and application.

THE FOUR “Cs” OF COLOR MANAGEMENT
Making a printer profile isn’t just about printing a test chart and reading it with a color measurement instrument. First you have to set up the device to produce the best color. The four “Cs” of color management is a convenient way to think about each of the profiling procedures — they are consistency, calibration, characterization and conversion (see Table 1 and Figure 1).

Figure 1: The four “Cs” of color management is a convenient way to think about each of the profiling procedures. Once these steps are performed, the RIP can convert color for accurate matching.

Table 1: The 4 “Cs” of Color Management

To help you understand this somewhat involved process, we’ll use a somewhat tortured analogy — imagine that your driver’s license is about to expire, so you head down to your local motor vehicle office for a renewal.
When it’s your turn in line, you realize that you need to get your photo taken. Is your hair combed? Did you wear a suitable shirt that won’t blow out or create a moiré pattern? Thank goodness for motor vehicle offices with mirrors! If only you had thought ahead, you could have had the best driver’s license photo of your life.

1. Consistency. The first “C” means to keep your printer consistent by optimizing its color output. This step is comparable to choosing a nice shirt before your trip to the office of the Department of Motor Vehicles. To create color, inkjet printers shoot microscopic droplets of ink onto the media. The amount of ink required varies with the printer resolution, the media’s capacity to hold ink, and other variables. Therefore each RIP provides a way of setting the optimum ink density. Too much ink will actually lower density, as well as cause excessive drying time, bleed, running and other problems. Too little ink will make images too light. The first step in profiling is to determine the optimum ink density (see Figure 2). You want good color saturation along with quick drying and freedom from artifacts. Ink limits can be determined using a densitometer, but can just as easily be set by eye.

Figure 2: The first step in getting consistency on a printer is to set the optimum ink density. This usually involves reading a test chart of CMYK values from 0–100 percent relative ink. Note in the “before” target above that additional ink added at the right end of the scale doesn’t increase the density, but will waste ink and prolong drying time. In the “after” target, the optimum ink produces maximum density using the minimum amount of ink.

Most inkjet printers are CMYK, meaning they use combinations of cyan, magenta, yellow and black (keytone) inks. These may be combined with light cyan and light magenta or with other hues like orange, green, red, or blue. If each ink is measured on a scale of 0-100 percent dot area, then the sum of four inks (CMYK) is theoretically 400 percent. This figure is known as the total ink coverage. Generally printers don’t need 400 percent ink coverage to achieve their maximum density. They can get away with 100 percent black, and smaller percentages of CMY. As with ink limits, too much total ink coverage can lead to slow drying time, bleeding, and ink running. You usually set total ink coverage using the RIP manufacturer’s proprietary test target (see Figure 3).

Figure 3: In addition to individual CMYK ink channels, the sum of all inks, or total ink coverage, must also be set. In this example, total ink coverage is so high that ink puddles on the surface of the target. The optimum total ink coverage produces the darkest black with the minimum amount of ink.

2. Calibration. Once the ink limits have been established, calibration sets the printer to conform to standard by determining the printer’s contrast range from light to dark. Following our DMV analogy, this step is like combing your hair for the photo. Within this range, linearization ensures that tones are evenly spaced within the available density range (see Figure 4). Linearization ensures good highlight, shadow, and midtone detail. Linearization requires a densitometer.

Figure 4: Calibration of the printer to achieve known standards is done by linearization, which evens out the tones from 0–100. This produces consistent prints from printer to printer and over time.

3. Characterization. The steps leading up to an inkjet printer’s ICC profile are designed to optimize color reproduction. The ICC profile is a snapshot of the printer’s color reproduction capability (like the photo taken for your driver’s license). This is usually made by printing a chart of 300-1500 color patches, then reading these with an automated spectrophotometer (see Figure 5).

Figure 5: Color profiling captures the printer’s color reproduction characteristics into a standard ICC profile. To make the profile, a color target of 500–2,000 patches is read with an automated spectrophotometer such as this X-Rite i1 iO scanning table. (Image courtesy of X-Rite.)

4. Conversion. Once you’ve done your job by properly installing a manufacturer’s profile or creating your own, then the RIP can do the hard work of converting color values from those of the source profile (usually a standard working space like Adobe RGB) to the destination profile (your monitor profile for soft proofing and printer profile for output). The clerk has processed the paperwork, placed the new photo and printed your brand new license (I told you it was a tortured analogy).

DOWNLOADING PROFILES
Manufacturers typically post profiles on their Web sites in a compressed format, such as ZIP (.zip) or Aladdin StuffIt (.sit) archives. To download a profile:

Visit the media manufacturer’s Web site and browse to the downloadable media profiles. These are usually organized by printer, RIP or driver, ink, resolution and other variables.

To download a profile from the list, right-click (Windows) or Control-click (Mac) on the profile link, and select Download File to Disk. Download the file to your desktop or other location where you can easily find it.

After downloading the profile archive, decompress it with Aladdin’s free StuffIt Expander (www.allume.com) or WinZip Computing’s WinZip (www.winzip.com).

The archive may include a ReadMe file that tells how to install and use the profile.

USING PROFILES IN RIPS
The following section shows how some of today’s more popular RIPs accept profiles.

Onyx. Onyx RIP Queue, PosterShop, and ProductionHouse programs all use a media format known as an Onyx Media Library (.oml). To install an .oml, select the printer you want to use and open the Onyx Media Manager. In Media Manager, select Profile > Import, and browse to the profile.

SA International (SAi). FlexiSIGN and PhotoPRINT programs from SAi are essentially the same RIP marketed to different customer bases. Current versions of both RIPs can import profiles as a preset file (.ptf), which includes a linearization file (.trc), ICC profile (.icc), and all the settings that were used to make the profile.
To import a .ptf, start the RIP, select File > Import Preset (see Figure 6), and browse to the .ptf file. If the profile you downloaded has separate .trc and .icc profiles instead of a .ptf, these can be added to their respective settings in the Color Management tab (see Figure 7). To get the correct color, be sure to set the same resolution and screening that were used to make the profile.

Figure 6: Manufacturer-supplied profiles can be imported into SA International FlexiSIGN and PhotoPRINT programs using the Import > Presets function.

Figure 7: In FlexiSIGN, the Default Job Properties dialog box shows the ICC profile (.icc) and the linearization file (.trc), which can be imported individually or as a Preset.

Wasatch. Profiles for Wasatch’s SoftRIP program for version 5 and higher come in the form of a Wasatch configuration file. To install the profile, copy the folder into the wwrip5 > Configurations > <printer name> folder, where “<printer name>” is the name of your printer. The profile will then be available in the Print > Setup > Configuration setting in the RIP (see Figure 8).

Figure 8: To load a manufacturer-supplied profile into Wasatch SoftRIP, place the profile in the Configurations folder and then into the sub-folder bearing the printer’s name.

EFI. The Fiery RIP program from EFI creates a connection between users, workflows and output devices. To set up color management, you must first create a workflow. To set input profiles, first select the workflow, then click on Properties > Color > Color Management (see Figure 9), where you can select CMYK, RGB, Gray, and Multicolor input profiles and check the box to read embedded profiles. To set up printer profiles, first select the printer, then click on Properties > Output Device > Quality, and select a Media Set, which includes the ink type, base linearization and media profile.

Figure 9: Color profiles in EFI’s Fiery RIP are based on the workflow.

Drivers. To install an .icc profile for your printer’s driver, place it in the folder Windows/System32/Spool/Drivers/color or in the folder Mac Library/ColorSync/Profiles.

CONCLUSION
If you understand the principle of color workflow — that color “comes from” an input profile, holds in a standard working space, and “goes to” an output profile — you can figure out how to use profiles in any RIP for accurate, consistent color.

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