Image Processing Reference
diamond-shaped areas are produced. The size of the dots is made proportional to the aver-
age lightness of the image at that point. The human eye hides the detail of the dot pattern,
so you perceive a continuously toned image and not a grid of dots. If you look very closely,
the dots become visible.
Color printing techniques apply the half-toning trick but they overlay cyan, yellow,
magenta and black (CMYK) to create the color. The half-tone mask is rotated by 15 degrees
for each successive color so as to reduce any moiré effects. Figure 6-10 shows the four color
The films for these prints are created in the same way as the newsprint half-tone
images, but usually a finer grating is used for the half-tone mask.
Figure 6-10 Color printing separations.