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FLEXO Magazine : May 2013
Three technologies have emerged to enable a much better match between the color specified by the CPC and the color achieved on press. Press Characterization: The first technology is an improvement in press characterization technology. Ultimately, the conversion of spot colors to process colors is based on the press profile. The more accurate the press profile; the more accurate the color match. Between 2009 and 2013, it ’s become clear that placing as many targets on the press form as space permits, results in the most accurate profile. It’s been proven that having multiple samples within a press sheet and measuring multiple sheets throughout a run provides far greater color accuracy than measuring a single sheet. Closely related to the principle of “data quantity ” is the principle of “data smoothness. ” Random targets produced the best data, however, there is no way to tell whether the data is smooth by looking at a random target. The requirement of smoothness for flexo color data is well understood from the work that’s been done with dot gain curves. The need for smooth data is even greater for color profiles. Tools to view random data in “ visual” format allow us to see the smoothness Tools to view random data in visual format and to mathematically smooth the data enable us to work with less than perfect conditions. The image at left is the printed test target. The image in the center is the measured data displayed in visual form. The image at right is the same data that has been run through mathematical smoothing. The most stable combination of inks to reproduce any color is that combination of inks that are closest to that color. Press characterization data should include the maximum number of “relevant” combinations (see hue wheel at left). Color conversion logic should select the closest three colors to the color being reproduced (see hue wheel at right). 32 FLEXO may 2013 www.flexography.org