By: Cory Sawatzki and Juergen Roesch
Written for the Idealliance: Guide to Print Production V.18.
If You Work With Brand Colors, You Need to Know About CxF
Consistent appearance and predictability is what print buyers expect. And while printing CMYK can still sometimes result in surprises and rejections, it is generally very well defined and specified. Standards and proof systems assist in streamlining all steps from concept to production.
The moment spot colors enter the mix, everything changes. Just about every domestic or international brand is defined by their custom color schemes and therefore relies on accurate reproduction. Communicating color information just for solids can already become challenging, and even more so when printing tints or overprints.
A common way of communicating colors is the use of spot color swatches, though fading, rubbing or even changes in their formulation or production processes can introduce differences between these swatches. It’s also important to understand that most swatches are mainly order numbers of ink buckets and just show the visual result of that ink onto one specific paper stock. There are different swatch books for different stocks, such as coated, matte, or uncoated papers. On any other material, the color result can be very different. This is the variation that can be expected if only specifying an ink name. And that set only covers different types of paper, no foil, film, metal, or fabric.
Many brands use ink draw-downs or color chips, to provide a visual representation of the ink solid which gets sent to all involved in the design and production process. In many cases also information on the conditions under which the print color must be compared to the provided sample get provided. Printers can then use ink formulation tools to match the provided color chip on the final print substrate. Often tint behavior cannot get extracted from a singular color sample and can be problematic to predict.
This is where CxF comes to the rescue. CxF stands for Color Exchange Format and is not a product, but a digital file format (like PDF). Developed by GretagMacbeth (today a part of X-Rite) it has since seen several improvements and is today an open and official ISO standard: ISO 17972.
CxF, is an XML based data format which can include spectral measurement data of ink solids and the entire range of tint and overprint tint values. What makes CxF so important is its ability to also contain valuable information on measurement conditions such as device and filter settings, brand specified tolerances, substrate types, and already existing ink formulation recipes. Additional custom information that might be considered valuable to store and exchange can also be included.
One of the benefits of CxF is the ability to embed CxF data for every spot color of a print job into the PDF/X-4 of the print job itself. This provides a secure way of storing all pertinent brand color information into a single file. Embedding ensures a reliable form of communication without the possibility of lost data. Due to this, there is no need to ship physical ink drawdowns or equip everyone in the print supply chain with identical copies of a spot color booklet.
(PDF/X-4 is required as lower PDF or PDF/X versions lack full support of spot color and overprint information)
The print job assets you would have previously needed to collect in an envelope, including images, proofs, text copies, films, or spot color chips, are now stored securely within the job’s PDF. A PDF/X-4 with embedded CxF serves as a more secure “job bag” to safely store all the information on how every page element and each spot color channel is supposed to print and look. This single file format ensures information cannot get lost – like a spot color chip falling out of an envelope.
Because everything is within a single digital file, a copy of the file can be sent across the country or around the globe in minutes and contains every piece of data that’s required to accurately reproduce the job as desired.
CxF does more than just aid in the print production process for brand colors. Because CxF is an ISO standard it is also in use by most visualization, design, proof, signage, production applications, and now textile. At this point some manufacturers might not yet have added complete and accurate support, or many users in your supply chain use outdated tools, therefore, it is recommended to check with your supply chain to verify all their products provide support for CxF/X4 (ISO 17972-4). Many design tools only allow import of CxF’s L*a*b* values and many don’t support accurate visual representation of tint or overprint appearance, but as long as all output tools can correctly reproduce color information from the embedded CxF data, your print production can be matched globally.
CxF provides the ability to specify the ink sequence in production. Together, with the spectral tint and overprint values in CxF/X4, this allows precise visualization, prediction and eventually process control.
The opacity of an ink defines how it changes when it gets printed on top of another ink as well as how it modifies the appearance of the ink it gets printed on top of. Think of printing Yellow over Cyan: you expect green. Depending on the opacity of the yellow ink, the produced green can be a bit more Cyan or a bit more Yellow. At maximum opacity Cyan is hidden under Yellow if opacity is low, there’ll only be a greenish sheen to the Cyan. Now change the print sequence to Cyan over Yellow.
CxF/X4 within a PDF/X-4 includes spectral tint and overprint data so applications can use that data together with the print sequence information for accurate print prediction.
With all these benefits, everyone should be aware of and even use CxF/X4
If you work with standardized, seasonal, or brand colors and haven’t looked at CxF lately, take a look!
Here some info on the history of the ISO 17972 standard:
There are four different ISO 17972 documents: CxF3 (ISO 17972-1) which provides prepress digital data exchange and verification for 4 color process printing. CxF/X2 (ISO 17972-2) which defines the Custom Resource within the CxF/X structure for the creation of scanner target data. CxF/X3 (ISO 17972-3) which defines the output target data within the CxF/X structure for the creation of output printer target data. CxF/X4 (ISO 17972-4) which defines the exchanging spot color characterization data within the CxF/X structure.
For more information about CxF or ORIS CxF Toolbox, please contact us at: firstname.lastname@example.org