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Hexachrome Printing

The Whys and Hows of RIPping HiFi Print Jobs

By Dan Reid

Hifidelity printing is on the rise. The flexography market is aggressively adopting the PANTONE Hexachrome printing system for increased color vibrancy. Large and grand format printers that support red and blue or Hexachrome ink configurations are available today. The challenge is selecting a RIP that provides robust calibration and mature color separation features using ICC color format.

Adding hifidelity printing or a Hexa-chrome workflow is a daunting challenge for most. Not only is support for multi-color workflows sparse but confusing. Seperating images into five or more color channels is not a system print professionnals are accustomed to, let alone graphic designers.What file formats support more than four color channels? How do you target color for hifidelity systems in the regular imaging toolset of Photoshop, Illustrator, etc.?

A growing handful of applications support more than four color channels. Photoshop does not directly support converting to more than four color channels. Neither does Adobe Illustrator. Adobe InDesign v2 does not support the Hexachrome printing process as Quark v4+ does.

Plug-ins from Pantone aid in separating to six-color Hexachrome printer profiles from Photoshop and Illustrator but not five or seven or more. So you see multi-color separations are not standardized across applications by any means. This is where a mature RIP can convert to special ink configurations instead of relying upon clients (or workstations) to convert upstream.

4/c vs Hexachrome
The most widely publicized hifidelity ink configuration is justifiably the Hexachrome process. Hexachrome certified inks are not the run of the mill cyan, magenta etc. inks but have brighteners to achieve a cleaner color resulting in a larger color gamut. You really aren’t taking advantage of the Hexachrome process if you just add orange and green to your normal CMYK ink set. The Hexachrome process was introduced in 1996 by a direct descendant of Pantone’s founder; Pantone boasts 90 percent or better matching with Hexachrome certified inks and paper combinations.

Hexachrome requires color management ICC profiles for conversion. Ideally the RIP will recognize and use embedded ICC profile information for bitmap graphics and allow default designation for EPS. If the RIP does not support six color ICC profiles, pre-seperate them in Photoshop or Illustrator using the PANTONE HexWare plug-ins or within a page layout program. Verify that the RIP accepts pre-separated files like DCS 2.0, EPS or PDF to get around proprietary color systems. Proprietary color systems utilize tables instead of standard ICC profiles.

In most cases two additional colors work best instead of odd color configurations. You wouldn’t really want to build a five color ICC profile of just an additional red primary for photographic output. Adding blue with red primary provides the complimentary color to balance hue back. So a RIP that does not support five or seven channel ICC profiles is not necessarily a limitation.

Offset and sheet-fed printers charge a premium for additional spot color bump plates because of the additional make-ready and clean-up in the printing. Hexachrome ink configuration minimizes make-ready and clean-up. The time, materials and labor savings alone justify using a six color configuration. Jobs designed for four color plus spot plates can be converted to Hexachrome process to allow more jobs on the same press without clean-up between jobs.

Spot Colors
A RIP should have the option to measure color with a spectrophotometer. Most RIPs include default tables for Pantone color libraries. Better RIPs use L*A*B* values of the PANTONE MATCHING SYSTEM using the ICC output profile. For instance ColorBurst RIP incorporates Praxi-soft’s VectorPro product to minimize color mismatch. VectorPro’s supertweak function builds optimized libraries using an output profile and licensed Pantone L*A*B* libraries instead of generic process builds.

Elements for success
The biggest factor bar none in successful hifidelity and Hexachrome printing is the RIP software. Most RIPs support color calibration for four color printing but may not for additional colors. A good RIP uses a color measurement device for primary color ink restriction and linearization (dot gain curves). Ideal RIPs include an option to designate how much and where the additional primaries are mixed. The idea is to restrict the additional primaries by lightness and saturation. RIPs that include this advanced feature offer a number of confusing GUI. After determining ideal ink restrictions and linearization curves you can successfully characterize the stable printing process.

The calibration data should be used for both pre-separated files and those converted by the RIP. File formats that support multi-channel are DCS 1.0 or 2.0, EPS, PDF v1.3 and separated Adobe Postscript 3 files. DCS is commonly found in programs like Photoshop for saving out each color channel as a separate file. V2 contains each plate in a singular file with a composite preview available. Since the file is separated color plates, no color processing aside from calibration restrictions is imposed. Separated files also feature a single file containing all the color info. PDF offers the same features and functionality.

So multi-color printing is not for the timid. Pre-separating upstream can sometimes mitigate confusing workflows. The choice for conversion in Photoshop and Illustrator is limited by the Pantone plug-ins known as HexWare. Other software programs like Gretag’s iQue color server product do support six channel ICC profiles for conversion. QuarkXPress v4.x (and higher) does support Hexachrome ICC profiles.

Even these alternative solutions can be baffling to configure. Choosing a RIP with Hexachrome ICC profiles support simplifies conversion. Undoubtedly the RIP will have adequate calibration options to maintain consistency.

Oct2002, Digital Output

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