specialty fabrics Color management for Printing on fabric can be more precise with color management techniques from the pros. By Rich Adams Figure 1

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1 Color management for specialty fabrics Printing on fabric can be more precise with color management techniques from the pros. By Rich Adams Many of today s fabric printers would like to set up their color monitors to match their printers. It s easy to see why. Soft-proofing, or viewing a printed piece on-screen with accurate color simulation, lets you preview print jobs and make adjustments to the file before printing. Getting an accurate screen-to-print match requires that you calibrate and profile your monitor. It also requires an accurate profile of the printer. After all, monitor and printer colors are drastically different. However, there s no inherent reason they should match without proper color management. This article reviews the techniques necessary to get accurate color on-screen, in proofs, and on prints. What is color management? Color management is the use of industry-standard profiles to get color to match on different input and output devices, including scanners, digital cameras, monitors, printers and proofers. The process got its start in offset printing, where users wanted to get better color matching from scanner to monitor, monitor to press, and proof to press. Color management really caught on in large format printing, where the variety of printers, ink and media provide the biggest challenge to color matching. Benefits of color management include: more accurate color on the printer you avoid tweaking images and printing them over and over, or chasing color soft- and hard-proofing you can simulate color on the monitor, and also simulate a production printer on a lower-cost proof printer accurate input by profiling your scanner or digital camera, you can get accurate and consistent input, from one scanner or camera to another, and with the same equipment over time standard working spaces defined by color profiles, standard working spaces enable consistent color workflow as color files are transferred from content creators to service providers. The four Cs of color management. Most people think of color management as profiling, which means characterizing the color of an object and saving it as a color profile. But color management is more than just profiling. Rich Adams is a trainer at the Graphic Intelligence Agency, a graphics training and technical support company started in The company now has more than 30 employees with offices in Akron, Ohio, San Diego, and Barcelona, Spain. Adams develops curriculum and solutions on color, photo, large format, prepress, proofing and other graphics technologies. Think of the steps involved as a hierarchy (see Figure 1) in which you ought to address the lower-level processes before the higherlevel ones. Figure 1 Conversion Characterization Calibration Consistency The 4 Cs of color management form a hierarchy in which profiling (characterization) ought to be preceded by calibration (linearization of tones) and consistency (optimization of the device for best color reproduction). Applications like Photoshop use the color profile to convert color for matching from device to device. An analogy would be going to the drivers license bureau to get your photo taken. The photo is like the profile. To get the best picture, you d probably want to comb your hair. Likewise, before profiling, you should calibrate your printer. Calibration is achieving a known standard of performance on a device. Thinking further ahead, if you wanted your photo to look its best, you might put on a nice outfit before going to the bureau. Similarly, the first step of color management, consistency, means setting up the device to achieve the best color that it can reproduce. The fourth C conversion means changing the value of colors to make them match on different devices. Color management equipment To make color profiles, you ll need a color measurement instrument and a profiling application. Two types of instruments are used to make profiles. Colorimeters read color through red, 54

2 green and blue filters and measure values in the LAB color space, which mathematically models human vision. Spectrophotometers read the entire rainbow of the visible spectrum, measuring the distribution of light throughout its nm range of wavelengths. Both types of instruments are available in models that read emissive light coming from monitors and reflective light from print samples. To profile printers, you ll need to read hundreds of color patches, so you ll want an automated or scanning spectrophotometer. Handheld scanning spectrophotometers, like GretagMacbeth s i1, read patches as you slide them along strips. X- Rite s DTP41 reads color patches as you feed the target row-by-row through the machine. Automated scanning spectrophotometers, like Gretag- Macbeth s SpectroScan and iccolor, read targets automatically. Today s top profiling applications include programs from GretagMacbeth ( and Monaco ( a division of X-Rite, Applications are also available from Creo ( and Heidelberg ( but are used mostly by customers who have those manufacturers printing equipment. Profiling for fabric printing Monitor To profile your monitor, you will need an emissive colorimeter such as GretagMacbeth s i1 Display or Monaco s MonacoOptix. You can also use a spectrophotometer capable of reading monitor colors, such as GretagMacbeth s i1 Photo, i1 Publish, i1 Beamer, or Spectrolino. To achieve the first of the 4 Cs of color management consistency on a color monitor, the monitor should be relatively new and in good operating condition. Set brightness, contrast and color balance values (if available) that are Figure 2 The most commonly used standard RGB working spaces are Adobe RGB, ColorMatch RGB, and srgb, each defined by a standard ICC profile. Instruments most commonly used to profile print samples include (left to right) the GretagMacbeth i1, X-Rite DTP41, GretagMacbeth iccolor, and GretagMacbeth SpectroScan. close to the values to which you want to calibrate (some programs help you set these values by the numbers). Monitor profiling programs calibrate to a known color temperature (measured in Kelvin, where higher values are bluer) and contrast (gamma, usually 1.80 for Macs and 2.20 for PCs). After calibrating, the color management application will profile your monitor by reading a series of color patches. To save your profile, name it so that you ll remember the monitor type, calibration values, and date. For example, a profile for a Sony monitor at 6500 K, gamma 1.80, made on July 11, 2004 might be called Sony_D65G180_ icc. To check that applications are aware of your monitor profile, open Photoshop and check the Color Settings. Your monitor profile should be displayed in the list of RGB profiles. Don t select your monitor profile as a working space (you should use one of the standard spaces instead), but do confirm that it s in the list and therefore known to applications. Standard working spaces Standard working spaces were introduced in the late 1990s with Photoshop 5. A standard working space is a place to store color data until you know what you want to do with it. For example, you might want to display, print or proof a file. Standard working spaces are defined by International Color Consortium (ICC) profiles. Standard spaces common in the graphic arts (in order of increasing size) are srgb, ColorMatch RGB and Adobe RGB (see Figure 2). Standard working space profiles can be embedded into saved images, so that when the images are transferred from one computer to another, or from a content creator to a service provider, the color remains consistent. Printer To profile your printer, you ll need a spectrophotometer capable of reading reflective samples and a color management program that can make printer profiles. The 4 Cs of color management are important in printer profiling. The profile is just a snapshot of how the printer reproduces color in a certain condition. Before profiling, you should ensure printer consistency by optimizing the ink density settings and tone reproduction values for the ink and media you re using. If you re using a printer with the manufacturer s free driver, the consistency step may simply mean picking a media setting that gives enough ink for good color, but not so much that the ink 55

3 COLOR MANAGEMENT FOR SPECIALTY FABRICS GretagMacbeth s i1 handheld (top) and SpectroScan table and Spectrolino (left) spectrophotometers are instruments for reading fabric samples. bleeds into or runs off of the fabric. If you re using a PostScript raster-image processor (RIP) with your printer, the RIP may have its own optimization routine that includes ink density, linearization and total ink limit settings. Calibrating a printer usually means linearizing the tone values, so that tints are evenly spaced from 0 to 100 percent in value. This ensures that images print with good contrast and smooth gradations. To profile the printer, print a test chart from the color management program, then read the chart with the spectrophotometer. Color management programs have separate test charts for RGB and CMYK printers. While most printers use CMYK (cyan, magenta, yellow, and black) ink, many are set up to receive RGB data. These include Epson inkjet printers that run with the manufacturer s free driver. If sent CMYK data, the driver will first convert it to RGB and then back to CMYK, or whatever combination of inks it uses (including light cyan, light magenta, and/or light black). CMYK printers, such as the HP 5500ps or printers run with a software RIP, use PostScript and print in CMYK mode. To profile an RGB printer, use an RGB test chart of 300 to 1,000 patches. To profile a CMYK printer, use a CMYK test chart with 300 to 1500 color patches. 56

4 COLOR MANAGEMENT FOR SPECIALTY FABRICS Fabric profiling tips Making color profiles of fabrics can present challenges, depending upon the media s thickness, stiffness and surface characteristics. Here are a few pointers for profiling based on our experience with fabrics for inkjet printing: Spectrophotometer selection Most of the scanning spectrophotometers read fabric just as well as they read paper. If you plan to profile a certain type or range of fabrics, it s a good idea to get a demonstration of the spectrophotometer before purchasing and make sure it works well with the range of fabrics you want to profile. Handheld scanning spectrophotometers If using a handheld scanning instrument like GretagMacbeth s i1, the instrument must be able to slide across the fabric easily, without rubbing or getting caught on the print. X/Y scanning spectrophotometers The GretagMacbeth SpectroScan can read the greatest variety of print samples, including fabrics up to 1.5 mm thick. On the SpectroScan, the sample remains stationary, while the Spectrolino measurement head moves across it. The faster ic- Color can read samples up to 1.0 mm thick. This instrument s read head remains stationary, while the sample moves underneath it. To feed properly through the iccolor, the fabric may need to be stiffened by taping the back. Shiny fabrics Graphic arts spectrophotometers were designed to read paper samples with a 0/45 degree measurement geometry. To minimize reflected glare, they shine light on the sample at a 45 degree angle and collect light on the vertical. When reading textiles, fabric fibers may scatter light, so the color will measure differently than it appears to the eye. Also, if a fabric has shiny fibers, the reflected glare may cause colors to read improperly. With the GretagMacbeth SpectroScan, you can attach a polarizing filter to help reduce reflected glare. The polarizing filter might cause the colors to read darker than they actually look, so it may be necessary to edit the profile to get the proper contrast and color balance. Include training When purchasing a color management system, consider including one or two days of training with the system. Setting up the instruments and software and getting the system to deliver good-looking color can be rather complicated and may be difficult to do by relying on telephone support. Working with a software RIP A software RIP is a program that drives a printer. Software RIPs such as Onyx PosterShop ( Scanvec Amiable PhotoPRINT ( and Wasatch ( offer a number of options for achieving consistency and doing calibration, to give you optimized, repeatable color. RIPs have a number of production features including the ability to drive multiple printers, group jobs together to save media, and preflight jobs. Profiling a RIP To make color profiles with a RIP, you ll need to start by setting ink limits. You want enough ink on the media to get a good color gamut, but not so much that the ink takes too long to dry or even puddles on the media. Next, you want to linearize the ink and media. This involves printing a series of tint patches from 0 to 100 percent area, reading the patches with a spectrophotometer, and allowing the program to create a linearization curve. The linearization 57

5 COLOR MANAGEMENT FOR SPECIALTY FABRICS Figure 3 Photoshop s Proof Setup dialog box enables you to specify the profile of the final output device for soft-proofing on the display as well as printing to a proof printer. curve ensures that your printer reproduces tones with the best contrast, and enables you to calibrate multiple printers to match. After linearizing, you should determine the total ink coverage: the sum of all printing ink percentages that the printer, ink and media can handle. This ensures that you won t put too much ink on the media in the shadow areas. After determining ink limits, linearizing and setting total ink coverage, you can then print a profiling target and create a profile for the printer. Some RIPs include profiling packages as options. Before purchasing, make sure that the package supports the color measurement instruments you want to use. Or, before buying instruments, make sure they re supported by your RIP. Workflow for color matching Workflow refers to the way images, files and documents are moved from one device or process to another. When colormanaged workflow is properly set up, it enables consistent color from input to output on multiple devices. Think of workflow as a path from one device to another. A file could be described as coming from a source device and going to a destination device, each described with a color profile. Photoshop shows how profiles are handled on the workflow path. The Image > Assign Profile command is used to define the source of an image, if none was embedded in the image (or the one embedded was removed). Image > Convert to Profile is used to convert a file from the current source space to the destination space. Scanner to monitor When scanning a photo or capturing a digital photo, the source would be the scanner and the destination would be a standard working space. The source profile can be applied using your scanning or digital image capture software if it supports ICC profiles or by using Photoshop s Image> Assign Profile command. You can then convert to a standard working space (e.g. Adobe RGB) using the Image > Convert to Profile command. To display your image accurately, you want to make sure that What You See Is What s In the File (WYSIWIF). Photoshop converts from the standard working space profile to the monitor profile. Monitor to print When printing an image, the source would be the standard working space, and the destination would be the printer profile. To convert to the printer profile, use Photoshop s Print with Preview command (see Figure 3), specifying the printer profile. Upon printing, Photoshop will convert the image from standard RGB to printer RGB (for RGB printers) or printer CMYK (for CMYK printers). Proof to print To match a production printer on a faster or lower-cost proof printer, you ll need a color profile for each device. To preview the job as it will print, use Photoshop s View > Proof Setup command, specifying the profile for the production printer. To print to a proof printer, use Photoshop s Print with Preview command, specifying the production printer as the source space and the proof printer as the destination. All the calibration, scanning and training may seem daunting at first, but once a color management system is set up, only minor adjustments will be needed, depending on the project. The real pay off comes with precise color printing on fabric and less time spent chasing color. To offer feedback or comment on this article, please contact Mary Connor, Editor, , mlconnor@ifai.com. Turn to page 82 to contact the source for this article. Resources You don t have to puzzle out your color management problems on your own! Several savvy companies work exclusively on getting your graphics to look the best they can, the first time around. It can be difficult to set up your color management system and it s costly to make mistakes. So if you re serious about printing great graphics, these companies can help: The Graphic Intelligence Agency (GIA), Akron, Ohio, provides training and support for the visual communications industry. The company s goal is to make complicated products easy to understand. GIA offers color management workshops, interactive online training, and training that is tailored to client needs. The GIA Web site offers what the company calls Clear Papers, which are just like white papers, only less opaque. Check out their Web site at Rods and Cones, Santa Cruz, Calif., provides workflow systems and technical services for people who use graphics and color. The company makes assessments and recommendations based on customer needs. Graphics experts at Rods and Cones test every new profiling and media management technology on the market, so their customers don t have to. Check out their Web site at Here are a few more links on color management. These companies sell color management products, but there is knowledge to be gleaned from their Web sites. Look for the buttons labeled training, online seminars, troubleshooting and white papers, or type color management into the site s search engine. Adobe Systems, Apple Computer, or Aurelon, Color Solutions, ColorVision, Gretag Macbeth, Kodak, Monaco Systems Solutions, cosys.com Praxisoft LLC, X-Rite Inc., 58