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FLEXO Magazine : July 2014
that it is difficult, hardly reproducible and may yield gray balances that shift from one color cast to the other over the tonal range. Instead, gray balance can be calculated with the highest level of preci- sion from a very limited number of color measurements. The DFTA Technology Center offers the respective calculator software which has been verified in its functioning (see Image 2). The evaluation of the gray balance is based on seven deliberately modified color blocks per tonal range block, which may even be reduced to only four color blocks if space on the test target is scarce (see Image 3). Optimizing The Print Condition Now that we have discussed the importance of gray balance, it is time to explain how it may be plausibly embedded into a print con- dition—i.e. a combination of substrate, printing ink, printing press, printing plates, etc. —for harvesting the fruits of optimum stability of the print process and easiness of file preparation. This is how to optimize your print condition: • Evaluate the optimum amount of ink transfer for the process inksC,M,YandKoverthe analysis of the curves derived from an inking experiment in the CIE Lab color space. Here I would like to point to a trade press article written by Christian Weber. He suggests adjusting the optimum amount of ink transfer on the maximum saturation of the respective color that may be derived easily from the shape of the ink’s CIE Lab curve If one stays beneath this optimum saturation, the print results will be less brilliant and colorful than might be possible otherwise; if one goes beyond the point of optimum satura- tion, one loses colorfulness again though the darkening of the respective ink, plus one adds extra cost to the process through over inking. To those of you using the extra ink transfer capa- bilities of the flat top print forms: Do not exaggerate and over stress their processes. The respective ink transfer experiments for this optimization step may practically be carried out on a proof printing press • The first production press trial with a test target including step wedges and gray balance test elements yields the press charac- teristic curves (be sure to measure Relative Colori- metric Intensity) and the respective information about gray balance. Please make sure to use the DFTA gray balance test target and the DFTA gray balance calculator software (seen in Image 2 and Image 3) • Calculate suitable compensation curves for platemaking accord- ing to the information derived in the prior step • Second platemaking under consideration of the calculations from the prior step and second proof print with a test target that verifies the gathered cognition and, if OK, uses a color manage- ment test target for color profiles. This test target may be either one of the following: Optimization of process inks through ink transfer experiments, according to Christian Weber Image 2: The DFTA-TZ Gray Balance Calculator “Even if its roots date back several years, it seems like the G7 initiative has only just now reached the European continent. ” 48 FLEXO | JULY 2014