Page 156 - Graphic Design and Print Production Fundamentals

144 Chapter 5. Pre-press
problem is multiplied when we boost the black colour by adding screened values of cyan, magenta, or
yellow to the colour block. When white type or graphics knock out of these background panels, any
slight mis-registration of any colour will leave a halo of that colour in the white type or graphic. This
problem can also be solved with trapping software. Essentially, the trapping engine outlines all the white
type with a small ‘black only’ stroke that knocks out the process colour that boosts the black, making
the white type fatter in that colour separation. This ‘reverse trapping’ works well when applied to the
four imaging technologies we have been examining: lithography, flexography, electrophotography, and
inkjet.