DOT SHAPE AND CONTRAST OF MOIRÉ BAND PATTERNS

Abstract

This chapter discusses dot shape and contrast of moiré band patterns. By a proper selection of dot shape and dot orientation, the moiré contrast can be decreased considerably in band patterns. These patterns never occur in the conventional fourfold screen symmetry. However, if a screen with fourfold symmetry is combined with a screen of sixfold symmetry, the interference always takes the form of band patterns. Such a combination may have some advantages, especially if the screen with sixfold symmetry is selected for yellow while the magenta, cyan, and black printers are made in a fourfold symmetry. A band moiré pattern may be expected between the screen lines with small angle separations. For example, when the yellow screen lines are directed at 0° and the magenta lines at 15°, then if the periods are of the same order of magnitude, a 15° band moiré in flesh colors and reds will occur. The contrast of this band moiré can, however, be reduced by selecting a favorable shape and orientation of the yellow dots. It is possible that by reducing the moiré contrast in the reds, the contrast of similar moiré bands in the greens may be enhanced. It depends on the colors that dominate the picture how the selection should be made.