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Reducing, Or Eliminating, Objectionable Rosettes

When screens of cyan, magenta, in addition to dark are overlaid at their respective angles (105º, 75º, 45º) they course of report a moiré designing called a "rosette." If the printer is required to purpose a fairly coarse AM/XM halftone hide (e.g. 85-150 lpi (newspaper & periodical work) ), then, depending on the icon color content, the rosette designing tin conk visible plenty to last objectionable.
One means to trim down the visibility of the rosette construction is to motility to a finer AM/XM hide which makes the rosette smaller in addition to thence less visible. However, if that is non possible, so changing the separation method mightiness last a feasible option.

The bulk of RGB to CMYK icon conversions purpose "GCR" every bit the method (it is the default separation technique inward Adobe PhotoShop). This ensures that wherever C, M, in addition to Y inks are used dark volition last introduced. The effect is a real visible rosette construction every bit seen inward the left icon below. in addition to dark are overlaid at their respective angles Reducing, or Eliminating, Objectionable Rosettes
GCR----------Click icon to enlarge----------UCR

To reduce, in addition to fifty-fifty eliminate well-nigh rosettes, a amend strategy is to purpose the UCR separation method on problematic images. UCR separations (see icon on correct above) different GCR separations, primarily innovate dark solely inward neutral in addition to close neutral color areas. Since real little, if any, dark is introduced inward C in addition to one thousand hide tint areas – no rosettes are truly formed inward those areas in addition to thence no rosettes are visible. The effect is smoother, less grainy appearing color.
While the UCR separation technique tin trim down or fifty-fifty eliminate rosettes, at that topographic point is a downside inward that at that topographic point volition last a slight growth inward ink usage likewise every bit a slight reduction inward color stability through the pressrun. That is why it should last used solely for images amongst problematic colors - primarily nighttime blues in addition to purples likewise every bit nighttime peel colors/areas.
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