On the Same Wavelength: Color Management Essentials for Wide-Format

It has long been said — or at least implied — that color management is like the weather: everyone talks about it, but no one ever really does anything about it. The need for color management is well-established in general commercial printing, but as wide-format in all its myriad forms has grown, shops are discovering the need to manage their digital devices as well.

One of the inherent problems of color management for wide-format printing is the sheer number of variables — different presses, different ink sets, different substrates, and different applications. All the things that make wide-format printing so versatile, also make it difficult to color-manage.

Color management blues

Take all the available ink technologies. “There are solvent-based, dye-based, UV-curable, latex, and dye-sublimation inks,” said Bart Fret, director of large-format sales for GMG Americas. Dye-sub inks, Fret added, are particularly problematic. “They are either printed on paper and transferred under pressure and heat to the final substrate or printed direct-to-fabric. The transfer method has many variables, since even the pressure and speed at which it is transferred influences the colors.” As we saw in our Fabric Printing Expert series, any variation across a textile calender unit can cause inconsistent color.

Finishing can also impact the appearance of color. “Many materials are laminated after they are printed,” said Fret. “Coatings and laminates change the color of the artwork and need to be considered.”

The various applications for wide-format printing also can create color management snafus.

“Each media type and application has different requirements,” said Bryan Manwaring, director of product marketing for Onyx Graphics, Inc., “and the applications are used in different environments. For example, lighting can play a large role in the appearance of color. A vehicle wrap, for instance, may have outdoor lighting needs that aren’t necessary in textile applications. Shop owners must be aware of all variables and their potential impacts and employ the right technology to solve them.”

Then there’s the elephant in the room: wide-format graphics are big. “Most large-format and signage applications can be much larger than what we see in other printing processes such as labels, packaging, and commercial print applications,” said Mark Geeves, director of sales and marketing for Color-Logic. “Trying to color-manage billboards or large-format signage requires more than just single measurements of two or four millimeters with an instrument. It would be better to have large aperture instruments with the ability to average measurements or scanning instrumentation which could average measurements across a calibration, characterization (profiling), or process control patch.”

All of these challenges are enough, but major wide-format projects or campaigns can involve the same or similar graphics printed on some combination of wide-format technologies, and even analog technologies like offset. As a result, the color all has to match, sometimes down to the nanometer.

Red alerts

Effective color management starts with color measurement, which usually involves a spectrophotometer, a device that measures the amount of light reflected from a print sample. Small-format commercial printers usually have a small spectrophotometer kicking around, but measuring wide-format output raises some additional problems.

“Hardware flexibility is a key challenge,” said Jay Kelbley, product manager for Xrite. “Due to the varying sizes and formats of output, it can be important to have a flexible measurement device, such as a handheld and xy, rather than just a page scanner.” An xy device attaches to a scanning table that allows for automated scanning of color swatches or printer output. “A device that can be used on an xy table, like with Xrite’s i1i0, but also used handheld, like an i1 Pro 2, which gives the user the ability to automate scanning of color data as well as to take spot measurements on the printer.”

Some wide-format printers also have spectrophotometers built into the devices themselves, which greatly facilitates measurement. 

Orange you glad you manage color?

Once you have a measuring device, there are three basic steps to color management:

• Calibration — Essentially, you print color patches on your printer/press, measure the color values you printed, compare them to target values (i.e., what they should be), and then let the digital front end adjust individual ink densities to compensate for differences.
• Characterization — A given ink set will yield different color characteristics on  different substrates. As a result, a color profile (aka an “ICC profile”) is needed for each ink/substrate combination. A color profile is basically the “correction data” for a given ink set on a given substrate on a given printer. It tells the front end or the RIP how to adjust the ink densities to get the output to conform to standard values.
• Control — Keeping tabs on the printer to ensure that it doesn’t “drift,” or change the way it prints color over time, which can happen.

Another challenge specific to wide format is that color management solutions are in a kind of “arms race” with equipment and ink manufacturers. New ink sets and expanded colors are being introduced all the time, which makes it easier to reproduce Pantone and brand colors, but harder to color-manage.

“The more inks you add, the more difficult color management gets,” said Fret. “There are two major problems with most color management systems, since they are based on process CMYK. When additional inks are added, the profiles will use the same amount of data available to all the inks, significantly reducing the accuracy inside the profile.” Also, he added, “the ink mixing method is based on CMYK, but with more inks, there are now complementary colors that should not be mixed.” For example, take an ink set that adds orange. “At what point does the color management software decide to cease adding magenta and yellow to an orange-tinted color, and just add orange? Many of these systems just add all of the ink components, even the complementary ones, and just muddy the result.”

A good color management system will allow the user to define where and how to use an ink.

Indigo-go

Then there is “cross-process” color management — keeping color consistent across offset and digital, or even different digital, printing technologies.

“The best way to do this, rather than relying on each of the RIPs that drive each of the printers and their own color management systems, is to use one capable, centralized system that controls both the analog and all of the digital presses,” said Fret. “The less standardization that exists between and among different print devices, the more likely things can go wrong — and they often do.”

Using a centralized color management system doesn’t necessarily mean that you’re using the same software to manage, say, an offset press and a wide-format printer, but rather, said Fret, “the same color engine, possibly inside different software, that has the tools and specific controls for the printing process it addresses. This makes sure the color is managed to the same target regardless of the printing technology used so that the visual match between these is guaranteed, or is at least much closer.”

Then there is the proliferation of specialty inks, such as metallics, to which a lot of the existing solutions have yet to catch up. “Color-Logic focuses on metallics,” said Geeves, “and even though there are currently instruments designed to measure metallics, there are no software programs that can utilize those measurements. For working with metallics, we promote calibration and process control of the CMYK ink sets.”

How green is my galley?

Xrite’s Kelbley brings up another elephant in the room: proofing, specifically hard (print-based) vs. soft (monitor-based) proofing. “If someone is doing soft proofing, they’ll need a solution that supports monitor calibration,” he said.
”If they’re doing hard proofing, they should consider a viewing booth that supports several light sources, to accurately simulate the customers’ final possible viewing environments.”

In today’s environment, soft proofing has advantages over hard, especially for wide-format applications.

“I suggest large-format companies look at instruments and software that will calibrate a monitor for soft-proofing applications,” said Geeves. “Digital printing devices today are production machines, and I don’t know why so many companies use them for making proofs when color management provides the ability to use soft proofs on your monitor for so much of the output. Think about the loss in productivity by producing [hard] proofs over the course of a month.”

Yellow pages

There is no shortage of solutions for color management, be it for small- or wide-format. When shopping for a system or software, looking for ease of use should be paramount, as well as ensuring that it is compatible with what you are seeking to print.

“I would ask what kind of materials are being used to ensure that the solution chosen is compatible,” said Kelbley. “If a user is planning on using papers with optical brighteners, for example, you would want to make sure that the solution chosen can measure and compensate for these.”

“For profiling software, ease-of-use is a huge question to not only ask, but to get a demo of before purchasing,” said Geeves.

“PSPs need software solutions that make color management easy, and they need a solution that matches color across media and devices,” said Manwaring. “Questions might include, ‘Does your solution have the ability to hit specific corporate colors?’ ‘What kind of integrated tools are available to adjust my color gamut?’ and ‘Is it easy?’”

“A color management system should allow you to get the best possible results in the shortest time,” said Fret. “One of the most important things that a color management system should offer is a way to do all these things easily, so you do not require a color expert to use it.”