freieFarbe e.V. uses ColorLogic ZePrA’s Spot Color Iteration to Develop its Color Atlas

ColorLogic GmbH

28 July 2021

Founded by a coalition of German and Swiss color professionals, freieFarbe e.V., freeColor, is a non-profit association in Germany that specializes in prepress and color management. Their initiative is to share knowledge and tips on how to create consistent color across all application fields and to make color free.

Main Product

Their main product is the innovative HLC Colour Atlas, a tool for use as a basis for all stages of professional color communication – from design to the final product. The printed color atlas was designed and produced in accordance with the German standardization body DIN SPEC 16699 “Open Color Communication”, and contains over 13,000 CIELAB-HLC colors in the XL version. It is also available for free in digital format on our website. The prints have a color accuracy that would not have been possible a few years ago (average dE-00 < 0.5); and is comparable to the far more complex lacquer printing process.

The production team at freieFarbe e.V. tested various solutions for optimizing the individual colors.” says Holger Everding, CEO at freieFarbe e.V. “In the end, we found only one solution that allowed us to accomplish all steps: ColorLogic’s ZePrA with its Spot Color Iteration in combination with ColorAnt. Due to the iterative optimization of the atlas colors, even highly saturated colors, which are at gamut border of the printing system, are reproduced with the highest possible accuracy.”

Using ZePrA

ZePrA was put to the test due to their very special requirements. First, they used the color server software for evaluation of the printable HLC/Lab colors via the printer profile. A color library in CGATS format was imported into ZePrA as a spot color library and the best possible conversion was calculated for a given printer profile. As a starting point they were able to produce a table that shows all reproduction of HLC/Lab colors is possible with a dE-00 < 2.  

Second, the Spot Color Iteration feature in ZePrA allowed the measurement technology optimization of a complete spot color library, based on a printer  profile to improve on the deltaE. Measurements were taken either directly from ZePrA or in ColorAnt. This allowed them to create optimized color libraries for a wide variety of applications, which was essential for the production workflow of the HLC Colour Atlas. 

Advantages of using ZePrA

Another special ZePrA feature is the ability to optimize even very large color libraries. For the HLC Colour Atlas XL, they successfully prepared and calibrated a color library of 15,000 colors for measurement with an X-Rite i1Pro2 spectrophotometer and iO2 measuring table. However, this works just as well with 3 or 200 colors. Once the colors have been measured, ZePrA calculates new optimized device colors and test charts based on the printer profile, which are then measured once again as part of the iteration process. At the end after optimization with ZePrA for all colors that lie within the printable gamut, a dE-00 < 0.5 was achieved. This is within the reproducibility range of the printing system and the measuring instruments used.

At the start of the optimization, their color library contained colors that are in the gamut of the printer profile but had higher dE-00 than 2. After optimization with the Spot Color Iteration the results are a spectral color library and a color atlas generated from it, reproducing the printed HLC-CIELAB colors of different Atlas batches with a dE-00 <=1.

ZePrA and ColorAnt

ZePrA and ColorAnt are central and appropriate working tools at freieFarbe e.V. for optimizing the HLC color libraries and the associated color atlases. The iterative optimization of the atlas colors allowed them to reproduce even highly saturated colors with the highest possible accuracy. Furthermore, the color libraries created with these tools can be exported in a variety of data formats and can therefore also be used universally outside the ColorLogic environment.


CC-BY-40 · freieFarbe e.V.

Authors: Jan-Peter Homann, Screenshots: Matthias Betz

Contribution: Eric A. Soder, Holger Everding

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