Screening

Inks used in colour printing presses are semi-transparent and can be printed on top of each other to produce different hues. However, a printing press cannot vary the amount of ink applied except through screening, a process that represents lighter shades as tiny dots, rather than solid areas, of ink.

In process colour printing, the screened image (or halftone) for each ink colour is printed in succession. The screen grids are set at different angles, and the dots therefore create tiny rosettes which, through a kind of optical illusion, appear to form a continuous-tone image.

To appreciate the effect in the image shown, view your monitor from a distance.