Mechanical Preparation, Continued
Halftones
(Continued)
On occasion, the individual requesting the job may not have the original
continuous tone photograph but, a reproduced copy that has already been
through the halftone screen. If the halftone screen used was coarse and open,
you may be able to shoot it as a line shot. If not, you may have to rescreen
the image. Rescreening a halftone image will create a wavelike or checkered
pattern where the two dot patterns overlap. This is called moire. This
pattern can be undesirable and distracting. You can reduce or eliminate this
effect by turning the screen 15 degrees away from the halftone or using a
screen 50 lines coarser or finer than the original screen.
Figure 1-38 shows a sectional view of a glass halftone screen.
Figure 1-38.—A sectional view of a glass halftone screen.
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