Until the 1950s, there were no real industry standards for the colors of inks used in commercial printing. The Pantone Matching System (PMS) was established because, at the time, each manufacturer of inks followed its own standards and did not share them with their competitors, which became the source of much frustration. If inks were purchased from multiple vendors, the colors would not match. PMS changed this situation with a standardized ink color book.
Today, by contrast, there are industry standards for color formulations across not only printing technologies, but also other industries. As trends are monitored across a variety of business segments, more books on color are published.
Further, color management—which was a seemingly random process in the 1950s, if it could even be called color management at the time—has evolved into a completely organized process for the graphic arts industry, from input (e.g. scanning, photography and desktop files) to output (i.e.printed graphics); and from offset to flexographic to toner and inkjet printing; and from simple desktop printers to enormous high-end flatbed presses.
Regardless of how a file is created or produced, customers demand accurate colors matched across a variety of systems, including both monitors and printers. The developments of the past set the stage for the new generation of color measurement and management expertise that today’s wide-format printing sector has grown to depend on throughout its workflow, from design to production to quality control.
Certainly, achieving great color output is important for anyone hoping to profit in the sign and display graphics business. When working with wide- to grand-format printing equipment, there are four key considerations for reaching this goal:
- Consistency.
- Calibration.
- Characterization.
- Conversion.
Spectral technology can help manage the complexity of color-measuring optically brightened substrates.
Consistency
The very first consideration is the condition of the printing device. The printer must already be behaving consistently if color management is to proceed successfully.
“Getting the device into a known state is the most important process before you do anything else,” says Larry Spevak, president of ColorBurst Systems, which develops raster image processor (RIP) software for inkjet printing.
To this end, proper and consistent maintenance and regular servicing of the equipment will be key.
Calibration
The next step is calibration, which involves adjusting the printer to match a given set of color values, so as to ensure all printed colors remain consistent throughout the production process.
“Once a consistent condition of the printing device has been established, the next fundamental task that has to be done properly is calibration,” says John Nate, worldwide technical product training manager for Electronics for Imaging’s (EFI’s) Fiery Wide Format color management software. “I don’t care how well everything else is done; you will not be able to get to your desired results if calibration is done improperly or not frequently enough.”
Nate compares this procedure to baking a cake, where calibration is like setting the proper temperature for the oven.
“If the oven temperature is too low, you will get brownies instead of cake,” he says, “and if it is too high, the cake will burn before it is baked through. This is why calibration has to be done early on. You cannot overcome the limitations later if the calibration is off.”
“In the calibration process, there are three things to consider: printhead height, bi-directional inkjets and the media feed,” says Spevak. “These are relatively easy to calibrate for most devices, but grand-format printers are so fast and are equipped with such a large printhead array, they must be ‘dialled in’ very carefully. Most are set up with a manual or automation calibration routine for this reason.”
Printed graphics should be checked under the same lighting conditions they may actually encounter once they are installed in the field
Characterization
While calibration is the process of adjusting the printing device’s behaviour to meet certain targets, characterization—also known as profiling—is the process of modifying how the device prints various colors, based on the inks and substrates being used. Typically, the results
of characterization are stored as an International Color Consortium (ICC) device profile, which then allows a colour management system or colur-aware application to make necessary modifications as the need arises.
“The first steps in characterization are to print a set of ‘profile patches’ and then create a profile that takes into consideration that device, the ink set and the target substrates,” says Spevak. “That is used for linearization of the RIP. If you do those things with a properly calibrated digital printer, you are golden. You will get the best color for the gamut that is possible for that ink and that media.”
Linearization refers to the process of optimizing the printer’s imaging system as a means of controlling all of the optical and physical variables involved in printing the image to generate an image with predictable and consistent results.
Conversion
The fourth consideration, conversion, involves the transformation of one type of color space to another.
“This is the least-understood of the four Cs,” says Lou Prestia, a senior product line manager for EFI. “When we calibrate or characterize, we are creating one-, two- or three-dimensional (1-, 2- or 3-D) tables. The conversion stage is when we apply those different tables to accomplish a transformation.”
In this sense, conversion is highly reliant on the steps that precede it.
“If you are making a profile and converting the colors in software like Adobe Photoshop, it is as easy as clicking ‘convert to profile’ and choosing the rendering intent and the destination profile,” says Prestia, “but in the world of digital printing, it is a more complicated process because there is discrete calibration, a 2-D lookup table on most RIPs and a characterization or ICC profile, which is typically 3-D, depending on how many inks are being used. This is why it is very important to use the appropriate calibration, the 2-D density or tonality correction in the creation of the profiling patches and the right profile for the printer. Only by using them together—and not ignoring the conversion phase of the overall process—will color management deliver the precision, consistency and expected results you are aiming for.”
Other considerations
During color management, another critically important aspect is the set of lighting conditions under which colors are being evaluated. The same color will look very different, after all, under different lighting conditions. The International Organization for Standardization’s (ISO’s) 3664:2009, Graphic Technology and Photography—Viewing Conditions, was reviewed in 2015 and specifies how viewing areas should be illuminated, whether using light booths or building lighting.
The Pantone Matching System (PMS) helped standardize ink colors. Photo © Bigstock.com
“ISO 3664:2009 is a great standard for people in production,” says Juergen Roesch, manager of business development for color management software developer GMG Americas, “but it is also important to understand your controlled viewing conditions in your production department may not be consistent with the printed graphics’ actual end-use viewing environment, which can cause some level of discontinuity.”
With this in mind, light booths are now available that enable viewing under a wide variety of possible lighting conditions, so printed materials can be checked under the same conditions they may actually encounter once they are installed in the field.
Another consideration is continuing education. While color management is, in many ways, becoming easier for the sign and graphics industry, there is still much education needed, both in production environments and on the customer side.
“One of the most important considerations for the sign industry today is color education,” says Leslie Herrmann, workflow studio manager for Global Imaging, which integrates wide- and grand-format printing systems with supplies. “This involves ensuring you are up-to-date on color standards and how to implement color management. Without that knowledge, you are basically crawling around in the dark.”
There are many resources available to help signmakers learn more, including online training, professional consulting and certification processes. Even color experts find it important to stay current and learn about the latest developments. Investing in the development of color management expertise is certainly one of the most important steps any sign and display graphics business can take, as it will move that organization to a whole new level of professional expertise.
Alfonso A. Hernandez, Jr., is a regional sales manager for X-Rite Pantone, which develops color management systems. The International Digital Enterprise Alliance (IDEAlliance) has certified him as a G7 expert and as a process control expert and has master-certified him as a color management professional (CMP). This article is based on information he presented in December 2015 at the United State Sign Council’s (USSC’s) annual Sign World International show. For more information, visit www.xrite.com.