March 18, 2015
If you have ever printed an image from a computer, then you know that what comes out of the printer rarely matches what’s displayed on the screen. This can be one of the most frustrating aspects of digital printing — the problem is not limited to sublimation — and is something that must be addressed to ensure the highest level of quality in print production. Color management is a process that helps maintain color between devices, such as monitors and printers, as an image moves between them. The goal is to establish reliability, predictability and consistency when viewing or printing an image or design as a whole. The overall difficulty of this is due to the use of different technologies, models and components to produce color, as well as the fact that color itself is highly subjective in nature. To understand what color management is, you must first understand how it is produced by the different components of the production process, namely the computer monitor and printer inks. Computer monitors emit color as red, green and blue (RGB) light. Although merging RGB light can produce all colors of the visible spectrum, monitors are capable of displaying only a limited gamut (i.e. range) of that same spectrum. Whereas monitors emit light, inked paper absorbs or reflects specific wavelengths. Cyan, magenta and yellow (CMY) pigments serve as filters, subtracting varying degrees of red, green and blue from white light to produce a selective gamut of spectral colors. Figure 1 shows just how distinctly different the color spaces are. This also helps to explain the difficulty in accurately converting from one color space to another, as monitors are RGB and printer inks are CMY (and K, or black). Thus, every image displayed on your computer monitor has to go through a conversion process before it reaches the printing stage. Like monitors, printing inks also produce a color gamut that is only a subset of the visible spectrum, although the range is not the same for both. Consequently, the same artwork displayed on a computer monitor may not match that which is displayed in a printed publication. Also, because digital printing processes use CMYK inks, digital art (RGB) must be converted to CMYK color for print. Colors vary from monitor to monitor and printer to printer. Thus, the color generated on a printed page is dependent on the color system used and the particular printer model, not by the colors shown on the monitor. In addition, other factors will have an effect on color, including transfer paper, substrate material and substrate color. COLOR CORRECTION The art of adjusting color transformation so that you can produce the highest-quality results on your final product is called color correction. There are three basic methods of color management for dye sublimation: International Color Consortium (ICC) profiles, RIP software and custom printer drivers. The three methods are somewhat similar, though they have specific differences. An ICC profile is a software file that ensures that when a specific color is selected on-screen, the designated color is consistently and correctly delivered on the substrate. Think of it as a color-matching program, as the screen color rarely produces exactly the same output color. Thus, a profile creates a link between specific screen colors and specific output colors. It doesn’t change the color; rather it ensures the correct output for a given input. To use this method, you must work with ICC-compliant software (e.g. Adobe Photoshop, CorelDRAW). The profile will be placed in the output stage of printing and the original equipment manufacturer’s (OEM) printer driver will be set to “No Color Adjustment.” This setup will color-correct the image and then send the data to the printer without further affecting the colors. Color-correction profiles for dye sublimation have their own unique problems, however. Under normal profile creation, when a color swatch has been printed out for testing, the profiling software knows how to adjust the colors to print the correct ones. When a dye-sublimation transfer is pressed onto a substrate, the ink turns into a gas and, while in this state, the colors change properties. This change can be quite dramatic (some blues look like green on paper) and it is, therefore, impossible to judge whether the print is correct until it is sublimated onto the final substrate. Thus, many sublimators create custom profiles that correlate the screen color to the final sublimated color, rather than to the ink color only. More sophisticated users may choose to use raster image processor (RIP) software that includes an ICC profile-creation capability to manage colors. Simply put, RIP software converts the image into individual dots (rasterizing) and sends the files to the printer. The process of creating ICC profiles from scratch is time-consuming, requires a good understanding of color science, and is an art form in and of itself. The ICC profile-creation process begins with printing a linearized color pallet. A spectrophotometer is then used to measure the colors. From these data points, the software creates an algorithm that calculates the color space and generates the ICC profile. Various types of images are then printed on a variety of substrates and the profile is meticulously adjusted to optimize the final result. RIP software also handles workflow tasks, such as nesting images and batching or queuing files to print. RIP software is available from a number of software companies, including CADLink, Ergosoft, Wasatch and ONXY, and prices range from $1,000-$5,000. Custom printer drivers are software programs that have color correction built into the printer control system. The advantage of this method is the ability to use non-ICC-compliant (Paint Shop Pro, Print Shop, etc.) and ICC-compliant software as the color correction is performed at the printer driver stage. In addition, it’s easier and less technical to use a custom printer driver than it is to use an ICC profile. Sawgrass Technologies offers the exclusive PowerDriver printer driver system for most of its sublimation products. It contains built-in profiles specific to the sublimation process. It should be noted that PowerDriver works with most popular graphics programs, including Photoshop and CorelDRAW. This software inserts a color palette (ColorSure) into the graphics program so that a user can select colors from the palette while working on images, thereby ensuring that the correct “final” color will be consistently produced during the sublimation production process. Whether using an ICC profile or a custom printer driver, the user should print out and sublimate the entire palette onto a pure white substrate, and then retain this color “chart” as a visual reference (Figure 2). The ColorSure palette is included with PowerDriver, and those using an ICC profile can create a simple palette of their own. The aforementioned printed chart demonstrates the exact color that is created via sublimation (plus the RGB settings), so the graphic designer has an accurate reference when choosing the proper colors for the image that is being created. Though the colors may not look the same on the screen as they do on the final substrate (Figure 3), by choosing the desired colors from the chart, you are assured that the output will be a match each time, regardless of what is displayed on the computer monitor. The most important aspect of color management in sublimation printing is consistency. Any change in a variety of variables — substrate, sublimation paper selection, pressing time, temperature and pressure — will impact the final output. Thus, it’s necessary to experiment and test as needed in order to generate the desired results, then establish a set of standards to work by, with the full understanding that a change in those standards can lead to a change in the appearance and quality of the final product. Though color matching and correction can be challenging to new sublimators, it’s not an impossible process to manage as long as you understand the challenges. Think of it as translating from one language to another. There isn’t always an exact match for each word, but as long as you understand the concept of the final message, you can create the necessary words to get the desired result. Award-winning author and international speaker Jimmy Lamb has more than 20 years of apparel decoration experience. He currently is the manager of communications for Sawgrass Technologies, Charleston. S.C. For more information or to comment on this article, email Jimmy at email@example.com. Hear Jimmy speak on sublimation topics at the 2015 Imprinted Sportswear Shows (ISS). Individual seminars are just $25 if you pre-register at issshows.com. ——————————————————————————– Suggested Reading Like this article? Read these and other digital decorating articles at impressionsmag.com: • “Would You Like a Plaque With That?” • “The Personal Touch” • “Simple Sublimation Solutions”
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