The Digital Eye: XCMYK

Stephen Romaniello is an artist and educator teaching digital art at Pima Community College in Tucson, Arizona for over 20 years. He is a certified instructor in Adobe Photoshop and the author of several books on the creative use of digital graphics software. Steve is the founder of GlobalEye systems, a company that offers training and consulting in digital graphics software and creative imaging.

If you run any printer, whether it be an inkjet, a toner based, an RGB or even an image-setter, you’ve no doubt encountered the problems associated with matching color. Even the most expensive professional printing device may not meet your expectations of the brilliance of the beautifully displayed RGB image that you see on screen or the true colors of the original source image. Without color management, matching colors on any printer is a shot in the dark at best. Color management maps the gamut of colors to best reproduce the true source colors.

Many strategies have been developed to achieve this goal. And as you likely gathered from the headline above, there's a new color space in town—XCMYK. We'll speak about that in this article soon, but first some important background.

Color Spaces

A color space is a profile of colors that reflect the capabilities of a device and a substrate for the purpose of reproducing and matching representations of color. There are many color spaces used for specific kinds of output (see Figure 1). The three general types of color spaces are: RGB, CMYK, and CIELAB. Some of the most commonly used RGB color spaces are sRGB—which has a smaller gamut and is used for general display purposes—and Adobe RGB 1998 which has a wider gamut that encompasses a large part of the CMYK color range and is used primarily for images that are to be converted from RGB to CMYK.

The most common CMYK profile that is used for offset lithography is—SWOP (Standards for Web Offset Printing), for lithographic output to color separations and its variations for types of substrates—and GRACoL (General Requirements for Applications in Commercial Offset Lithography). CIELAB profiles are device independent and encompass the entire spectrum of color that humans can perceive.

Device- and substrate-specific custom color spaces can be made by measuring the color output of a specific printer on a target substrate with a spectrophotometer and then calibrating the device with special software.

Expanded Gamut Printing

Because four-color process printing uses only Cyan, Magenta, Yellow and Back (CMYK) to produce an entire range of color, its potential to produce accurate color is limited (see Figure 2). Expanded gamut printing is often employed in offset lithography for a broader color gamut by adding three additional colored inks into the process. Most frequently, orange, green and violet are added to expand the range of printable colors. The same is true with certain large-format printers. Solid colors and specific Pantone colors that have traditionally been difficult to achieve can be more closely represented. For example, orange colors will be matched more accurately when, instead of combining yellow and magenta inks, orange ink is introduced (see Figure 3).

Expanded Gamut Ink Sets

Certain inkjet printers use variations of colors to produce more accurate representations. Some ink sets include not only CMYK but also lighter cartridges of cyan, magenta and black to extend the gamut. Here are some of the common types of ink systems that are available for inkjet printers:

  • CMYK—is a four-color ink set.
  • CMYK + 2—is a six-color ink set that uses two lighter colors in addition to standard CMYK (CMYK + light magenta and light cyan).
  • CMYK + 3—is a seven-color ink set that uses three lighter colors in addition to the four standard colors (CMYK+ light magenta, light cyan and light black)
  • CMYK + 6—is a nine-color ink set that includes photo or matte black (they can be switched depending on the substrate), cyan, vivid magenta, yellow, light cyan, vivid light magenta, light black and light-light black
  • CMYK + OG (Hexachrome)—developed by Pantone, is a six-color expanded gamut ink set that adds orange and green to the four CMYK colors.
  • CMYK + OGV—is a seven-color expanded gamut ink set that adds orange, green and violet to the four CMYK colors.

The benefits of expanded gamut compared to four-color process systems are the ability to enhance visual resolution, produce finer details, smooth gradients, deposit brighter colors and reduce graininess (see Figure 4A/B).

Bridging the Gap

To produce more accurate color, toner and inkjet-based digital printers required a color space that was larger than the industry standards of GRACoL and SWOP in order expand their color range. The industry needed a bridge from CMYK to Expanded Gamut. A color space had to be developed that increased the gamut of printable color without having to drastically alter the printing device. Printers are proprietary. Each printer—and there are hundreds on the market—have different capabilities and use different ink sets, not to mention the many choices of printable substrates available to them. The one thing that they have in common though is that they can print to GRACoL and SWOP color spaces—but with varying results.

Enter XCMYK

Idealliance is a global association representing the visual communications industry. It is responsible for having developed both the GRACoL and SWOP color spaces which are the two most commonly used specifications in the global print industry. They are the driving force behind the development of the latest expanded-gamut color space for use with digital and traditional printers—XCMYK!

XCMYK is part of Idealliance’s Expanded Gamut Project. The XCMYK research was conducted by the GRACoL Committee over a 15-month period in 2015 and 2016, and involved 26 test runs held in the US, Canada, China, Korea, Pakistan, Taiwan and Singapore. The color space was also tested with a wide variety of digital printers. The XCMYK profile was released in early December of 2016.

To learn more, I spoke with Timothy Baechle, director of Global Print Media Markets and Technologies at Idealliance. He gave me the background on this new cutting-edge color space.

“The inception of the XCMYK color space started in early 2015. When looking at this project from a digital standpoint with Ron Ellis, CEO of Ron Ellis Consulting LLC and lead consultant on the XCMYK Task Force—we knew that digital users of both toner and inkjet printers who had either CMYK only, or expanded-gamut printers needed something that was wider and more encompassing than the GRACoL color space. What makes this beautiful is that anything that has a RIP attached to it can simply download this profile and go to work.

“The feedback, downloads, reports, data, analyses, and adoption did not just come from one print medium," he continues, "but from offset, digital, inkjet-cut sheet and wide format, and from print service providers, OEMs, creatives, brands, and suppliers.

“When anything is released internationally—especially something as advanced as XCMYK which required collaboration from individuals and suppliers from around the world—it is overwhelming to see such a universally positive response from the world print markets.”

The Details

XCMYK is a new expanded-gamut CMYK printing method that yields a much wider color gamut than regular four-color process printing. The XCMYK color space is based on high-quality sheet-fed offset printing using standard IS0 12647-2 compliant CMYK inks run at higher than normal density levels, with nontraditional FM (frequency modulated) screening. The XCMYK color space can be reasonably approximated on any suitably adjusted offset press without a custom ICC profile.

It can also be simulated on toner and inkjet digital printing systems that have an equal or greater native color gamut. As far as expanded gamut printers are concerned, with three additional inks, the CMYKOGV gamut is only 14 percent larger, which makes the ease of use and substantial cost savings of XCMYK advantageous.

XCMYK is a much larger color space and yields a gamut that is much closer to the capabilities of wide-gamut, wide format printers. Because XCMYK was created using G7—the gray balance technology developed by Idealliance that created GRACoL and SWOP—it has a similar look but is more vibrant. For devices with a wide gamut capability, XCMYK is a perfect way to take advantage of the printer’s potential and benefit from the accuracy of color management.

One of the benefits of the XCMYK profile is that the same color space can be used for digital printers and offset lithographic devices. The relationship that XCMYK has between digital and traditional print is designed to give printers a common color space that links wide-format digital and traditional print methods.

XCMYK profiles can be downloaded from www.gracol.org (see Figure 5). A detailed report on XCMYK and gamut analysis is also available in the same location.