Mechanical Preparation, ContinuedHalftones(Continued)On occasion, the individual requesting the job may not have the originalcontinuous tone photograph but, a reproduced copy that has already beenthrough 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 rescreenthe image. Rescreening a halftone image will create a wavelike or checkeredpattern where the two dot patterns overlap. This is called moire. Thispattern can be undesirable and distracting. You can reduce or eliminate thiseffect by turning the screen 15 degrees away from the halftone or using ascreen 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 page1-51
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