Halftones-Cont.

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. Continued on next page 1-51