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FLEXO Magazine : September 2010
Technologies & Techniques Output prOfiles There has been a need to improve sev- eral aspects in the way output profiles are computed. For instance, the black genera- tion engine has needed revision in how it is mapped due to use of UCR and GCR and the “jumpiness” of the resulting curves seen in Figure 4. Both may produce a good visual match, but there is concern about the curve shape and the ability to produce smooth transi- tions and good shadow detail. New black generation engines have been built with an added smoothness control to address this as well. The effect of new smoothness algorithms can also be seen in the profile curves in Figure 5. Over the years, experience and feed- back from real-world application of color management has shown that posterization can plague output profiles, manifesting itself in banded gray ramps (Figure 6). Smoothness algorithms can help alleviate this problem; new noise reduction algo- rithms add robustness. Both help minimize the posterization effect as seen in the im- age capture in Figure 6. Optimization (iterative profiling) is a second step post-profiling method to reach greater color accuracy (for libraries such as Pantone), neutral gray, and more natural skin tones. This technique in conjunction with new core algorithms helps reduce the harsh transitions sometimes seen in skin tones or the loss of detail in shadows and accompanying reversals. Also, a better utilization of the gamut by the new engine is noted in round trip tests. Feature enhancements, like multi- threading in order to take advantage of multi processors, reduce profile calcula- tion times to a mere fraction of those found in previous systems. This is a welcome change in light of the growing popularity of figure 4. old black generation (left), compared to new black generation (right). figure 5. old algorithms (left), compared to new smoothness algorithm. figure 6. smoothness and noise-reduction algorithms help minimize the posterization effect. 48 FLeXO september 2010 www.flexography.org FLX_Sept2010_mech.indd 48 9/3/10 9:11 AM