CxF: Color eXchange File format

If you work with color, you will be learning more about CxF, (Color eXchange Format) the new, open-source, XML-based, universal standard for color specification. It will re-define some aspects of our job.

It was approved by the ISO in June of 2015, but is now hitting it's stride.

Here is the definition, as written by X-Rite, who proposed and championed the new standard:

"CxF is a new standard allowing seamless, worldwide, digital communication of all commercially significant aspects of color. Furthermore, CxF is defined in a completely open way so that all aspects of a color can be communicated, even when the application and the color communication features required are unknown. For example, every software vendor implementing / supporting CxF is able to extend the information set to the needs of a new application without affecting the general usability. Wherever color communication is mission-critical, CxF should be considered the communication solution of choice " 

"Typically, color communication is done today using colorimetric measurement values such as CIE-Lab, XYZ, RGB, density, CMYK, or spectral measurement values. These values are often communicated in proprietary formats that don’t provide for meaningful communication outside of a narrow use." 

"In general, it is not sufficient to communicate a color recipe, a reflectance curve, or a CIE-Lab value. Depending on the application there are specific needs in the way a color should be communicated. A universal color communication language must be open –to describe and communicate such known and even new, as-yet undefined effects. In addition, this language needs to be able to bridge the gap from one industry to another. Depending on the application, further attributes need to be assigned to spot colors. Among the infinite list of possible attributes assigned to spot colors are serial numbers, part numbers, color mixtures, price of pigments, light resistance of the color, descriptions, application notes, comments, and many more. "

Spot colors, or “named” colors are created in the design process to provide a specific visual color for a given name on a given substrate. The process of rendering spot/named colors on different output devices is challenging due to:

• Differences between different print technologies (colorants, screening, tonality)
• Differences related to substrates
• Differences related to different ink companies and formulations
• Differences related to different tonalities on different print technologies
• Differences related to different measurement devices, and conditions
• Differences related to different lighting conditions
• Differences related to overprint on white vs black vs another ink
• And more…

CxF/X4 was created to solve the problem of not getting an accurate/desired spot colors when printing on different devices, and not being able to accurately proof.

It has since become an improvement over the previous standard/

ISO 17972 defines methods for the use of CxF3 to exchange measurement data and associated metadata within the graphics industry.

• CxF3 (ISO 17972-1) This format provides prepress digital data exchange and verification for 4 color process printing.
• CxF/X2 (ISO 17972-2) This format defines the CustomResource within the CxF/X structure for the creation of scanner target data
• CxF/X3 (ISO 17972-3) This format defines the output target data within the CxF/X structure for the creation of output printer target data
• CxF/X4 (ISO 17972-4) This format defines the exchanging spot color characterization data within the CxF/X structure

CXF/X4 was developed to help address these issues related to Spot/Named color workflows.

Implementing CxF

In order to make CxF/X4 work in your environment, you need to have the 5 C’s of Color Control. 

• Color Capture device appropriate to the substrates being used in your process
• Calibrated output devices which render color consistently within the page and between pages
• Characterization of the actual spot/named colors for the given substrates being imaged (CxF/X4)
• Conversion which recognizes the CxF/X4 tags embedded in the PDF in order to convert to different print conditions (including proofing) accurately
• Conformance which allows you tosses the print and compare to the Reference color to determine if it's within desired expectations of color tolerance.

1. Determine the appropriate Color Measurement device:

Ensure measurement device is appropriate for given substrate, a 45/0 is appropriate for measuring on paper and similar substrates where the light from instrument is reflected at a predicted 45 degrees angle, but it is not appropriate when printing on substrates that have a metallic quality which will scatter the ancient light at different angles other than 45 degrees.

Understand that no two instruments measure the same way and that when multiple instruments are using in a workflow, that the color conformance between them has to be calculated before implementation, or you could find yourself beyond your tolerances before you start. 

2. Calibrate output devices

Obviously, for precise and accurate color reproduction, it is required to have output devices that can image color well within the customers' expectations for color tolerance. 

3. Characterization
Similar to how CMYK ICC Profiling defines the characterization data set of how a given set of inks/screening/tonality/substrate/print device will render color, we need a characterization data set of how a given spot/named color will render color for a given set of inks/screening/tonality/substrate/print devices. 

This characterization data set is created by printing tints of the desired color over white and black ink and on a given substrate (this quantifies the opacity of the ink, which is a major variable related to color reproduction). This requires printing the required color and measuring in the result. Once we have a characterization data set, we now can predict how this named color will react when exposed to different variables such as different substrates, print devices, lighting and mixing with other inks.

Again, similar to ICC Profiles, once you have your desired CxF/X4 characterization data for your given color, now you can provide a color palette to designers so they can more accurately see the results of this color when used in an actual design.


4. Conversion of the CxF/X4 data for different processes

Also, similar to ICC Profiles, CxF/X4 characterization data can be used to physically convert the color to different print conditions and accurately represent the original intent (assuming the output device has sufficient gamut to simulate the desired named color. 

This is critical for proofing the color to simulate what it will actually look like on the final device.

This CxF/X4 data can be used in an ink formulation system to automatically generate a new ink which will share the same spectral properties for devices that can’t use the same ink that the original definition was created for. For instance, Offset versus Screen print inks.

5. Conformance to assure the printed result will meet customer expectations

Again, similar to using ICC Profiles to assess the conformance of CMYK output, the Conformance can be assured by using the CxF/X4 data as the reference and assessing if the reproduction of the desired named color matches within defined tolerances.

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CfX contains meta-data specifications for a number of print variables, including, but not limited to:

Substrate types:
Coated Paper
Uncoated Paper
Cardboard
Glossy White Film
Transparent Film
Metallic Film
Transparent Film (reverse)
Leather
Metal
Paint
Paper
Plastic
Textile
Tile
Vinyl
Wood
Ceramic
Other

Background:
Substrate,
Process_Black,
Other.

Surface Finish:
None
Gloss Laminated
Matt Laminated
Gloss Varnished
Matt Varnished
Other

Print Process:
ElectroInk
Electrophotography
Flexography
Rotogravure
InkJet
Offset Lithography
ScreenPrinting
Other

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Also from X-Rite, the go-to CFX resource page, with links to the ISO docs, and other resources:

https://www.xrite.com/page/cxf-color-exchange-format

Here is a cool webinar video that explains and explores the format:

https://vimeo.com/138970501

And here is a link to a "What They Think" article:

http://whattheythink.com/articles/74283-cxf3-color-management-exciting-things-come/

The International Color Consortium (ICC) has praised the new format as an excellent way to spec spot colors:

http://www.color.org/CxF_test.xalter

We currently work in CGATS format, so here is a nifty online converter that may be helpful:

http://www.jpereira.net/apps/cxf2cgats/

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Do you have a color management question, horror story or event to share?

Email me at reilley4color@gmail.com